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Background: The impact method was used to make unilateral femoral comminuted fractures in tree shrews, which were then intravenously injected with lipopolysaccharide to create a traumatic systemic inflammatory response syndrome model. Methods: The treatment group was infused with tree shrew umbilical cord mesenchymal stem cells via the tail vein. After 10 days of treatment, 6 tree shrews were killed in the control, model and treatment groups and pancreatic tissue was collected for metabonomic analysis. Result: The 25 differential metabolites in the normal, model and stem cell treatment groups showed a trend of first decreasing and then increasing and 11 metabolites showed a trend of first increasing and then decreasing. These findings are in line with the recovery of the curative effect of the stem cell therapy model group. [ABSTRACT FROM AUTHOR]

Our comprehensive genomic investigation employing tree shrew calcium oxalate stone models unveils intricate links between kidney stone formation and diverse physiological systems. We identify a constellation of genes whose expression patterns point to multifaceted interactions among cardiovascular health, renal fibrosis, and bone homeostasis in the pathogenesis of renal calculi. Key players include CHIT1, TNFRSF18, CLEC4E, RGS1, DCSTAMP, and SLC37A2, which emerge as pivotal actors in arteriosclerosis, renal fibrosis, and osteoclastogenesis respectively, showcasing the complexity of stone disease. The downregulation of ADRA1D, LVRN, and ABCG8 underscores roles in urodynamics, epithelial-mesenchymal transition, and vitamin D metabolism, linking these to nephrolithiasis. Comparative genomics across tree shrew, human (Randall's plaque), rat, and mouse identifies shared KEGG pathways including Calcium signaling, Actin cytoskeleton regulation, Neuroactive ligand-receptor interactions, Complement and coagulation cascades, TRP channel regulation by inflammatory mediators, p53 signaling, and Fc gamma R-mediated phagocytosis. These pathways underscore the interconnectedness of immune, inflammatory, and metabolic processes in stone development. Our findings suggest novel targets for future therapeutics and prevention strategies against nephrolithiasis, highlighting the need for a holistic view of the disease encompassing multiple pathogenic factors. [ABSTRACT FROM AUTHOR]

ABSTRACTEpstein-Barr virus (EBV) infection in humans is ubiquitous and associated with various diseases. Remodeling of the immune microenvironment is the primary cause of EBV infection and pathogenesis; however, the underlying mechanism has not been fully elucidated. In this study, we used whole-transcriptome RNA-Seq to detect mRNAs, long non-coding RNAs (lncRNA), and microRNA (miRNA) profiles in the control group, 3 days, and 28 days after EBV infection, based on the tree shrew model that we reported previously. First, we estimated the proportion of 22 cell types in each sample using CIBERSORT software and identified 18 high-confidence DElncRNAs related to immune microenvironment regulation after EBV infection. Functional enrichment analysis of these differentially expressed lncRNAs primarily focused on the autophagy, endocytosis, and ferroptosis signalling pathways. Moreover, EBV infection affects miRNA expression patterns, and many miRNAs are silenced. Finally, three competing endogenous RNA regulatory networks were built using lncRNAs that significantly correlated with immune cell types, miRNAs that responded to EBV infection, and potentially targeted the mRNA of the miRNAs. Among them, MRPL42-AS-5 might act as an hsa-miR-296-5p “sponge” and compete with target mRNAs, thus increasing mRNA expression level, which could induce immune cell infiltration through the cellular senescence signalling pathway against EBV infection. Overall, we conducted a complete transcriptomic analysis of EBV infection in vivo for the first time and provided a novel perspective for further investigation of EBV-host interactions.

Synaptic plasticity is a key cellular model for learning, memory and chronic pain. Most previous studies were carried out in rats and mice, and less is known about synaptic plasticity in non-human primates. In the present study, we used integrative experimental approaches to study long-term potentiation (LTP) in the anterior cingulate cortex (ACC) of adult tree shrews. We found that glutamate is the major excitatory transmitter and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionicacid (AMPA) receptors mediate postsynaptic responses. LTP in tree shrews was greater than that in adult mice and lasted for at least 5 h. N-methyl-d-aspartic acid (NMDA) receptors, Ca2+ influx and adenylyl cyclase 1 (AC1) contributed to tree shrew LTP. Our results suggest that LTP is a major form of synaptic plasticity in the ACC of primate-like animals. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'. [ABSTRACT FROM AUTHOR]

The tree shrew (Tupaia belangeri) has long been proposed as a suitable alternative to non-human primates (NHPs) in biomedical and laboratory research due to its close evolutionary relationship with primates. In recent years, significant advances have facilitated tree shrew studies, including the determination of the tree shrew genome, genetic manipulation using spermatogonial stem cells, viral vector-mediated gene delivery, and mapping of the tree shrew brain atlas. However, the limited availability of tree shrews globally remains a substantial challenge in the field. Additionally, determining the key questions best answered using tree shrews constitutes another difficulty. Tree shrew models have historically been used to study hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, myopia, and psychosocial stress-induced depression, with more recent studies focusing on developing animal models for infectious and neurodegenerative diseases. Despite these efforts, the impact of tree shrew models has not yet matched that of rodent or NHP models in biomedical research. This review summarizes the prominent advancements in tree shrew research and reflects on the key biological questions addressed using this model. We emphasize that intensive dedication and robust international collaboration are essential for achieving breakthroughs in tree shrew studies. The use of tree shrews as a unique resource is expected to gain considerable attention with the application of advanced techniques and the development of viable animal models, meeting the increasing demands of life science and biomedical research. [ABSTRACT FROM AUTHOR]

The Chinese tree shrew (Tupaia belangeri chinensis) has emerged as a promising model for investigating adrenal steroid synthesis, but it is unclear whether the same cells produce steroid hormones and whether their production is regulated in the same way as in humans. Here, we comprehensively mapped the cell types and pathways of steroid metabolism in the adrenal gland of Chinese tree shrews using single-cell RNA sequencing, spatial transcriptome analysis, mass spectrometry, and immunohistochemistry. We compared the transcriptomes of various adrenal cell types across tree shrews, humans, macaques, and mice. Results showed that tree shrew adrenal glands expressed many of the same key enzymes for steroid synthesis as humans, including CYP11B2, CYP11B1, CYB5A, and CHGA. Biochemical analysis confirmed the production of aldosterone, cortisol, and dehydroepiandrosterone but not dehydroepiandrosterone sulfate in the tree shrew adrenal glands. Furthermore, genes in adrenal cell types in tree shrews were correlated with genetic risk factors for polycystic ovary syndrome, primary aldosteronism, hypertension, and related disorders in humans based on genome-wide association studies. Overall, this study suggests that the adrenal glands of Chinese tree shrews may consist of closely related cell populations with functional similarity to those of the human adrenal gland. [ABSTRACT FROM AUTHOR]

Introduction: Acute respiratory distress syndrome (ARDS) is a leading cause of respiratory failure, with substantial attributable morbidity and mortality. The small animal models that are currently used for ARDS do not fully manifest all of the pathological hallmarks of human patients, which hampers both the studies of disease mechanism and drug development. Objectives: To examine whether the phenotypic changes of primate-like tree shrews in response to a one-hit lipopolysaccharides (LPS) injury resemble human ARDS features. Methods: LPS was administered to tree shrews through intratracheal instillation; then, the animals underwent CT or PET/CT imaging to examine the changes in the structure and function of the whole lung. The lung histology was analyzed by H&E staining and immunohistochemical staining of inflammatory cells. Results: Results demonstrated that tree shrews exhibited an average survival time of 3–5 days after LPS insult, as well as an obvious symptom of dyspnea before death. The ratios of PaO2 to FiO2 (P/F ratio) were close to those of moderate ARDS in humans. CT imaging showed that the scope of the lung injury in tree shrews after LPS treatment were extensive. PET/CT imaging with 18F-FDG displayed an obvious inflammatory infiltration. Histological analysis detected the formation of a hyaline membrane, which is usually present in human ARDS. Conclusion: This study established a lung injury model with a primate-like small animal model and confirmed that they have similar features to human ARDS, which might provide a valuable tool for translational research.

Alzheimer's disease (AD) is the most common chronic progressive neurodegenerative disease in the elderly. It has an increasing prevalence and a growing health burden. One of the limitations in studying AD is the lack of animal models that show features of Alzheimer's pathogenesis. The tree shrew has a much closer genetic affinity to primates than to rodents and has great potential to be used for research into aging and AD. In this study, we aimed to investigate whether tree shrews naturally develop cognitive impairment and major AD-like pathologies with increasing age. Pole-board and novel object recognition tests were used to assess the cognitive performance of adult (about 1 year old) and aged (6 years old or older) tree shrews. The main AD-like pathologies were assessed by Western blotting, immunohistochemical staining, immunofluorescence staining, and Nissl staining. Our results showed that the aged tree shrews developed an impaired cognitive performance compared to the adult tree shrews. Moreover, the aged tree shrews exhibited several age-related phenotypes that are associated with AD, including increased levels of amyloid-β (Aβ) accumulation and phosphorylated tau protein, synaptic and neuronal loss, and reactive gliosis in the cortex and the hippocampal tissues. Our study provides further evidence that the tree shrew is a promising model for the study of aging and AD. [ABSTRACT FROM AUTHOR]

Myopia is widely recognized as an epidemic. Studies have found a link between Transforming Growth Factor-beta (TGF-β) and myopia, but the specific molecular mechanisms are not fully understood. In this study, a monocular model in tree shrews (Tupaia belangeri) was established to verify the molecular mechanism of TGF-β in myopia. The results indicated that there were significant changes in TGF-βs during the treatment of myopia, which could enhance the refractive ability and axial length of the eye. Immunohistochemical staining, real-time fluorescent quantitative PCR, and immunoblotting results showed a significant upregulation of MMP2 and NF-κB levels, and a significant downregulation of COL-I expression in the TGF-β treated eyes, suggesting that NF-κB and MMP2 are involved in the signaling pathways of TGF-βs induced myopia and axial elongation. Moreover, the expression levels of IL-6, IL-8, MCP-1, IL-1β, TNF-α, TAK1, and NF-κB in the retina were all significantly elevated. This indicates that TGF-β stimulates the inflammatory response of retinal pigment epithelial cells through the TAK1-NF-κB signaling pathway. In conclusion, this study suggests that TGF-β promotes the progression of myopia by enhancing intraocular inflammation. • Investigating the role of transforming growth factor (TGF)-β in the development of myopia. • Determining the molecular mechanisms of TGF-β in myopia using methods such as western blotting. • TGF-β significantly enhanced the development of myopia. • TGF-β2 promotes retinal inflammation through the smad7-TAK1-NFκB signaling pathway. [ABSTRACT FROM AUTHOR]

Objective: Systemic sclerosis (SSc) is a chronic systemic disease characterized by immune dysregulation and fibrosis for which there is no effective treatment. Animal models are crucial for advancing SSc research. Tree shrews are genetically, anatomically, and immunologically closer to humans than rodents. Thus, the tree shrew model provides a unique opportunity for translational research in SSc. Methods: In this study, a SSc tree shrew model was constructed by subcutaneous injection of different doses of bleomycin (BLM) for 21 days. We assessed the degree of inflammation and fibrosis in the skin and internal organs, and antibodies in serum. Furthermore, RNA sequencing and a series of bioinformatics analyses were performed to analyze the transcriptome changes, hub genes and immune infiltration in the skin tissues of BLM induced SSc tree shrew models. Multiple sequence alignment was utilized to analyze the conservation of selected target genes across multiple species. Results: Subcutaneous injection of BLM successfully induced a SSc model in tree shrew. This model exhibited inflammation and fibrosis in skin and lung, and some developed esophageal fibrosis and secrum autoantibodies including antinuclear antibodies and anti-scleroderma-70 antibody. Using RNA sequencing, we compiled skin transcriptome profiles in SSc tree shrew models. 90 differentially expressed genes (DEGs) were identified, which were mainly enriched in the PPAR signaling pathway, tyrosine metabolic pathway, p53 signaling pathway, ECM receptor interaction and glutathione metabolism, all of which are closely associated with SSc. Immune infiltration analysis identified 20 different types of immune cells infiltrating the skin of the BLM-induced SSc tree shrew models and correlations between those immune cells. By constructing a protein-protein interaction (PPI) network, we identified 10 hub genes that were significantly highly expressed in the skin of the SSc models compared to controls. Furthermore, these genes were confirmed to be highly conserved in tree shrews, humans and mice. Conclusion: This study for the first time comfirmed that tree shrew model of SSc can be used as a novel and promising experimental animal model to study the pathogenesis and translational research in SSc. [ABSTRACT FROM AUTHOR]

[Display omitted] • The LPS-induced tree shrews exhibited severe shortness of breath, resulting in hypoxemia. • The induced group of animals exhibited 72 ∼ 120 h endpoints, and none of them recover. • Diffuse alveolar damage was observed in the lungs of the tree shrew, which is the histological hallmark for the acute phase of ARDS. • 3D reconstruction of the lung CT images was used to accurately measure the extent and distribution of the whole lung injury in LPS-induced tree shrews. Acute respiratory distress syndrome (ARDS) is a leading cause of respiratory failure, with substantial attributable morbidity and mortality. The small animal models that are currently used for ARDS do not fully manifest all of the pathological hallmarks of human patients, which hampers both the studies of disease mechanism and drug development. To examine whether the phenotypic changes of primate-like tree shrews in response to a one-hit lipopolysaccharides (LPS) injury resemble human ARDS features. LPS was administered to tree shrews through intratracheal instillation; then, the animals underwent CT or PET/CT imaging to examine the changes in the structure and function of the whole lung. The lung histology was analyzed by H&E staining and immunohistochemical staining of inflammatory cells. Results demonstrated that tree shrews exhibited an average survival time of 3–5 days after LPS insult, as well as an obvious symptom of dyspnea before death. The ratios of PaO 2 to FiO 2 (P/F ratio) were close to those of moderate ARDS in humans. CT imaging showed that the scope of the lung injury in tree shrews after LPS treatment were extensive. PET/CT imaging with 18F-FDG displayed an obvious inflammatory infiltration. Histological analysis detected the formation of a hyaline membrane, which is usually present in human ARDS. This study established a lung injury model with a primate-like small animal model and confirmed that they have similar features to human ARDS, which might provide a valuable tool for translational research. [ABSTRACT FROM AUTHOR]

Abstract Background Cross-species transmission of zoonotic IAVs to humans is potentially widespread and lethal, posing a great threat to human health, and their cross-species transmission mechanism has attracted much attention. miRNAs have been shown to be involved in the regulation of IAVs infection and immunity, however, few studies have focused on the molecular mechanisms underlying miRNAs and mRNAs expression after IAVs cross-species infection. Methods We used tree shrews, a close relative of primates, as a model and used RNA-Seq and bioinformatics tools to analyze the expression profiles of DEMs and DEGs in the nasal turbinate tissue at different time points after the newly emerged swine influenza A virus SW2783 cross-species infection with tree shrews, and miRNA-mRNA interaction maps were constructed and verified by RT-qPCR, miRNA transfection and luciferase reporter assay. Results 14 DEMs were screened based on functional analysis and interaction map, miR-760-3p, miR-449b-2, miR-30e-3p, and miR-429 were involved in the signal transduction process of replication and proliferation after infection, miR-324-3p, miR-1301-1, miR-103-1, miR-134-5p, miR-29a, miR-31, miR-16b, miR-34a, and miR-125b participate in negative feedback regulation of genes related to the immune function of the body to activate the antiviral immune response, and miR-106b-3p may be related to the cross-species infection potential of SW2783, and the expression level of these miRNAs varies in different days after infection. Conclusions The miRNA regulatory networks were constructed and 14 DEMs were identified, some of them can affect the replication and proliferation of viruses by regulating signal transduction, while others can play an antiviral role by regulating the immune response. It indicates that abnormal expression of miRNAs plays a crucial role in the regulation of cross-species IAVs infection, which lays a solid foundation for further exploration of the molecular regulatory mechanism of miRNAs in IAVs cross-species infection and anti-influenza virus targets.

Abstract Background Epstein-Barr virus (EBV) infection is a major global threat; its manifestations range from the absence of symptoms to multiorgan malignancies and various gastrointestinal diseases. Analyzing the composition and metabolomic profile of gut microbiota during acute EBV infection might be instrumental in understanding and controlling EBV. Methods Six tree shrews were inoculated with EBV by intravenous injection. Blood was collected at regular intervals thereafter from the femoral vein to detect EBV and inflammatory biomarker. At the same time, tree shrew faeces were collected for 16 S rRNA gene sequencing and Non-targeted metabolomics analysis. Results 16 S rRNA gene characterization along with β diversity analysis exhibited remarkable alterations in gut microflora structure with a peak at 7 days post-infection(dpi). Some alterations in the relative richness of bacterial taxon were linked to infectious indicators. Of note, Butyricicoccus relative richness was positively linked to EBV presence in the blood and plasma, the opposite correlation was seen with Variovorax and Paramuribaculum. Non-targeted metabolomics indicated the fecal metabolome profile altered during EBV infection, particularly 7 dpi. The relative abundance of geranic acid and undecylenic acid in stool samples was positively linked to systemic inflammatory biomarkers, and an inverse relationship was reported with the estrone glucuronide, linoleic acid, protoporphyrin IX and tyramine. Conclusion Collectively, EBV infection in this model correlated with changes in the composition and metabolome profile of the gut microbiota.

Objective To observe the primary tumor of tree shrews and to provide a basis for studying the pathogenesis and prevention of trichoepithelioma.Methods A tumor was discovered in the chest and abdomen of a tree shrew during natural cultivation. The tree shrew was anesthetized, and the tumor was surgically removed. Hematoxylin and eosin (HE) staining and immunohistochemical staining were performed on the tumor tissue after paraffin section, and the tumor cells were isolated and cultured by passage. The isolated tumor cells were subcutaneously injected into healthy tree shrews and nude mice. The tumorigenesis of tumor cells in vivo was observed once a day, with nude mice continuously observed for 2 months and tree shrews observed for more than 6 months.Results HE staining showed that the basal cells in the dermis were arranged as a whole, like a string of petals, forming nests and stripe-like structures with clear boundaries. The observation results after magnification revealed that the tumor cells were arranged in a pallisade-like and basal pattern, with deep nuclear staining and minimal cytoplasmic. Immunohistochemical staining showed the high expression of CK protein and low proportion expression of ki-67 protein in tumor cells, as well as the high expression of vimentin and low expressions of Bcl2 and CD10 in tumor cell mesenchyme. The isolated tumor cells grew well in DMEM medium containing 10% fetal bovine serum and could be cultured by passage, but no tumor formation was observed in healthy tree shrews and nude mice inoculated with tumor cells.Conclusion Combined with the location of the tumor, overall morphology, HE staining, and immunohistochemical results, the thoracoabdominal mass of the tree shrew was diagnosed as a trichoepithelioma.

Background: Epstein-Barr virus (EBV) infection is a major global threat; its manifestations range from the absence of symptoms to multiorgan malignancies and various gastrointestinal diseases. Analyzing the composition and metabolomic profile of gut microbiota during acute EBV infection might be instrumental in understanding and controlling EBV. Methods: Six tree shrews were inoculated with EBV by intravenous injection. Blood was collected at regular intervals thereafter from the femoral vein to detect EBV and inflammatory biomarker. At the same time, tree shrew faeces were collected for 16 S rRNA gene sequencing and Non-targeted metabolomics analysis. Results: 16 S rRNA gene characterization along with β diversity analysis exhibited remarkable alterations in gut microflora structure with a peak at 7 days post-infection(dpi). Some alterations in the relative richness of bacterial taxon were linked to infectious indicators. Of note, Butyricicoccus relative richness was positively linked to EBV presence in the blood and plasma, the opposite correlation was seen with Variovorax and Paramuribaculum. Non-targeted metabolomics indicated the fecal metabolome profile altered during EBV infection, particularly 7 dpi. The relative abundance of geranic acid and undecylenic acid in stool samples was positively linked to systemic inflammatory biomarkers, and an inverse relationship was reported with the estrone glucuronide, linoleic acid, protoporphyrin IX and tyramine. Conclusion: Collectively, EBV infection in this model correlated with changes in the composition and metabolome profile of the gut microbiota. [ABSTRACT FROM AUTHOR]

d‐Galactose (d‐gal) and l‐glutamate (l‐glu) impair learning and memory. The mechanism of interaction between the gut microbiome and brain remains unclear. In this study, a model of cognitive impairment was induced in tree shrews by intraperitoneal (ip) injection of d‐gal (600 mg/kg/day), intragastric (ig) administration with l‐glu (2000 mg/kg/day), and the combination of d‐gal (ip, 600 mg/kg/day) and l‐glu (ig, 2000 mg/kg/day). The cognitive function of tree shrews was tested by the Morris water maze method. The expression of Aβ1‐42 proteins, the intestinal barrier function proteins occludin and P‐glycoprotein (P‐gp), and the inflammatory factors NF‐κB, TLR2, and IL‐18 was determined by immunohistochemistry. The gut microbiome was analyzed by 16SrRNA high‐throughput sequencing. After administering d‐gal and l‐glu, the escape latency increased (p <.01), and the times of crossing the platform decreased (p <.01). These changes were greater in the combined administration of d‐gal and l‐glu (p <.01). The expression of Aβ1‐42 was higher in the perinuclear region of the cerebral cortex (p <.01) and intestinal cell (p <.05). There was a positive correlation between the cerebral cortex and intestinal tissue. Moreover, the expression of NF‐κB, TLR2, IL‐18, and P‐gp was higher in the intestine (p <.05), while the expression of occludin and the diversity of gut microbes were lower, which altered the biological barrier of intestinal mucosal cells. This study indicated that d‐gal and l‐glu could induce cognitive impairment, increase the expression of Aβ1‐42 in the cerebral cortex and intestinal tissue, decrease the gut microbial diversity, and alter the expression of inflammatory factors in the mucosal intestines. The dysbacteriosis may produce inflammatory cytokines to modulate neurotransmission, causing the pathogenesis of cognitive impairment. This study provides a theoretical basis to explore the mechanism of learning and memory impairment through the interaction of microbes in the gut and the brain. [ABSTRACT FROM AUTHOR]

Radiotherapy-induced muscle injury (RIMI) is a major complication of radiotherapy for nasopharyngeal carcinoma. Transcription factor (TF) expression and alternative splicing are crucial events in transcriptional and posttranscriptional regulation, respectively, and are known to be involved in key signaling pathways contributing to a variety of human disorders, including radiation injury. To investigate the TFs and alternative splicing events involved in RIMI, we constructed a tree shrew model as described previously in which the RIMI group received 20 Gy of irradiation on the tensor veli palatini (TVP) muscles. The irradiated muscles were evaluated by RNA sequencing (RNA-seq) 6 months later, and the results compared with those for normal TVP muscles. The alt5p and alt3p events were the two main types of differentially regulated alternative splicing events (RASEs) identified via the Splice sites Usage Variation Analysis (SUVA) software, and these RASEs were highly conserved in RIMI. According to functional enrichment analysis, the differentially RASEs were primarily enriched in pathways related to transcriptional regulation. Furthermore, we identified 16 alternative splicing TFs (ASTFs) in ASTF–differentially expressed gene (DEG) networks based on co-expression analysis, and the regulatory networks were chiefly enriched in pathways linked to cell proliferation and differentiation. This study revealed that RASEs and ASTF–DEG networks may both play important regulatory roles in gene expression network alteration in RIMI. Future studies on the targeting mechanisms and early interventions directed at RASEs and ASTF–DEG networks may aid in the treatment of RIMI. • Radiotherapy-induced muscle injury(RIMI) is a major complication of radiotherapy for nasopharyngeal carcinoma. • Tree shrew model simulating radiotherapy for NPC is useful for research into RIMI. • RASEs and ASTF–DEG networks may both play important regulatory roles in gene expression network alteration in RIMI. [ABSTRACT FROM AUTHOR]

Aim: Periodontitis is an inflammatory, infectious disease of polymicrobial origin that can damage tooth‐supporting bone and tissue. Tree shrews, evolutionarily closer to humans than commonly used rodent models, have been increasingly used as biomedical models. However, a tree shrew periodontitis model has not yet been established. Materials and Methods: Periodontitis was induced in male tree shrews/Sprague–Dawley rats by nylon thread ligature placement around the lower first molars. Thereafter, morphometric and histological analyses were performed. The distance from the cemento‐enamel junction to the alveolar bone crest was measured using micro‐computed tomography. Periodontal pathological tissue damage, inflammation and osteoclastogenesis were assessed using haematoxylin and eosin staining and quantitative immunohistochemistry, respectively. Results: Post‐operatively, gingival swelling, redness and spontaneous bleeding were observed in tree shrews but not in rats. After peaking, bone resorption decreased gradually until plateauing in tree shrews. Contrastingly, rapid and near‐complete bone loss was observed in rats. Inflammatory infiltrates were observed 1 week post operation in both models. However, only the tree shrew model transitioned from acute to chronic inflammation. Conclusions: Our study revealed that a ligature‐induced tree shrew model of periodontitis partly reproduced the pathological features of human periodontitis and provided theoretical support for using tree shrews as a potential model for human periodontitis. [ABSTRACT FROM AUTHOR]

Objective To observe the primary tumor of tree shrews and to provide a basis for studying the pathogenesis and prevention of trichoepithelioma. Methods A tumor was discovered in the chest and abdomen of a tree shrew during natural cultivation. The tree shrew was anesthetized, and the tumor was surgically removed. Hematoxylin and eosin (HE) staining and immunohistochemical staining were performed on the tumor tissue after paraffin section, and the tumor cells were isolated and cultured by passage. The isolated tumor cells were subcutaneously injected into healthy tree shrews and nude mice. The tumorigenesis of tumor cells in vivo was observed once a day, with nude mice continuously observed for 2 months and tree shrews observed for more than 6 months. Results HE staining showed that the basal cells in the dermis were arranged as a whole, like a string of petals, forming nests and stripe-like structures with clear boundaries. The observation results after magnification revealed that the tumor cells were arranged in a pallisade-like and basal pattern, with deep nuclear staining and minimal cytoplasmic. Immunohistochemical staining showed the high expression of CK protein and low proportion expression of ki-67 protein in tumor cells, as well as the high expression of vimentin and low expressions of Bcl2 and CD10 in tumor cell mesenchyme. The isolated tumor cells grew well in DMEM medium containing 10% fetal bovine serum and could be cultured by passage, but no tumor formation was observed in healthy tree shrews and nude mice inoculated with tumor cells. Conclusion Combined with the location of the tumor, overall morphology, HE staining, and immunohistochemical results, the thoracoabdominal mass of the tree shrew was diagnosed as a trichoepithelioma. [ABSTRACT FROM AUTHOR]

Macroautophagy/autophagy initiated by STING1 (stimulator of interferon response cGAMP interactor 1) is actively involved in viral infection; and it is known that interferon-inducible guanylate-binding proteins (GBPs) exploit autophagy to defend the host against bacterial infection. Here we showed that in the tree shrew (Tupaia belangeri), a close relative to primates, TbGBP1 (T. belangeri GBP1) interacts with TbSTING1 to initiate autophagy and inhibit herpes simplex virus type 1 (HSV-1) infection.

The lateral geniculate nucleus (LGN), a retinotopic relay center where visual inputs from the retina are processed and relayed to the visual cortex, has been proposed as a potential target for artificial vision. At present, it is unknown whether optogenetic LGN stimulation is sufficient to elicit behaviorally relevant percepts, and the properties of LGN neural responses relevant for artificial vision have not been thoroughly characterized. Here, we demonstrate that tree shrews pretrained on a visual detection task can detect optogenetic LGN activation using an AAV2-CamKIIα-ChR2 construct and readily generalize from visual to optogenetic detection. Simultaneous recordings of LGN spiking activity and primary visual cortex (V1) local field potentials (LFPs) during optogenetic LGN stimulation show that LGN neurons reliably follow optogenetic stimulation at frequencies up to 60 Hz and uncovered a striking phase locking between the V1 LFP and the evoked spiking activity in LGN. These phase relationships were maintained over a broad range of LGN stimulation frequencies, up to 80 Hz, with spike field coherence values favoring higher frequencies, indicating the ability to relay temporally precise information to V1 using light activation of the LGN. Finally, V1 LFP responses showed sensitivity values to LGN optogenetic activation that were similar to the animal’s behavioral performance. Taken together, our findings confirm the LGN as a potential target for visual prosthetics in a highly visual mammal closely related to primates.

To achieve surgical anesthesia in animal experimentation, it is important to select the appropriate anesthetic dose. However, few studies have investigated the reasonable anesthetic dose in tree shrew (Tupaia belangeri). The aim of the study was to review the literature to determine the most commonly used anesthetic dose in tree shrew and to calculate the reasonable equivalent dose between tree shrew and rat based on the body surface area conversion. Two groups of 10 adult tree shrews each were anesthetized with 1% sodium pentobarbital through intraperitoneal injection separately at doses of 62 mg/kg (equivalent dose) and 40 mg/kg (reported dose). Anesthetic depth and times were assessed in addition to vital signs. The results showed that the dosage was quite different across studies, ranging from 15 mg/kg to 80 mg/kg, with 40 mg/kg being the most frequently reported dose. However, the group of tree shrews anesthetized with the commonly reported dose were unable to meet the requirements of surgery. In contrast, the equivalent dose (62 mg/kg, intraperitoneal injection with sodium pentobarbital) calculated by body surface area conversion could achieve an anesthetic time of 44.28 ± 3.95 min with no serious or fatal effects. During anesthetic monitoring, we found that sodium pentobarbital had an inhibitory effect on the blood pressure, pulse rate, respiratory rate and rectal temperature in tree shrews, especially on the respiratory rate. Thus, our study indicated that the use of the equivalent dose of sodium pentobarbital was effective in anesthetizing tree shrews. [ABSTRACT FROM AUTHOR]

In this study, we aimed to investigate whether chronic retinal inflammation is involved in the pathogenesis of form-deprivation myopia (FDM) using tree shrews as an animal model. Twenty-one tree shrews were randomly divided into 7-day/14-day FDM (FDM7/FDM14) groups and their corresponding 7-day/14-day control groups. Refraction and axial length were measured. To determine the effects of form deprivation on inflammation, we used real-time polymerase chain reaction (PCR) and immunohistochemistry to assess the expression levels of several proinflammatory cytokines. At day 0, the eyes in the FDM and control groups were hyperopic. However, after 7 and 14 days of form deprivation, the refractive error of the eyes in the FDM7 and FDM14 groups shifted from +6.6 ± 0.3 diopters (D) to +4.0 ± 0.5 D and from +6.4 ± 0.3 D to +5.0 ± 0.3 D, respectively. The levels of tumor necrosis factor-α, interleukin (IL)-6, IL-8, monocyte chemoattractant protein-1, and nuclear factor κB were increased in the FDM eyes, compared with those in the control eyes. The increase in matrix metalloproteinase-2 expression was greater in the FDM eyes than in the contralateral and control eyes, whereas collagen type I expression was downregulated. In conclusion, chronic inflammation may play a crucial pathogenic role in form-deprivation myopia in tree shrews.

Simple Summary: The function and regulation of rapid-eye-movement (REM) sleep is a topic of ongoing debate. It is often assumed that REM sleep is a homeostatically regulated process and that a need for REM sleep builds up, either during prior wakefulness or during preceding slow wave sleep. In the current study, we tested this hypothesis in the day-active tree shrew (Tupaia belangeri), a small mammal closely related to primates. We exposed the animals to a low temperature of 4 °C during their main sleep phase, a procedure that is known to suppress REM sleep. Cold exposure caused a significant drop in brain temperature and body temperature and also resulted in a strong and selective suppression of REM sleep. However, contrary to our expectation, the loss of REM sleep was not recovered during the subsequent day and night. These findings in a day-active mammal confirm that the expression of REM sleep is highly sensitive to environmental temperature but do not support the view that REM sleep is homeostatically regulated in this species. The function and regulation of rapid-eye-movement (REM) sleep is a topic of ongoing debate. It is often assumed that REM sleep is a homeostatically regulated process and that a need for REM sleep builds up, either during prior wakefulness or during preceding slow wave sleep. In the current study, we tested this hypothesis in six diurnal tree shrews (Tupaia belangeri), small mammals closely related to primates. All animals were individually housed and kept under a 12:12 light-dark cycle with an ambient temperature of 24 °C. We recorded sleep and temperature in the tree shrews for 3 consecutive 24 h days. During the second night, we exposed the animals to a low ambient temperature of 4 °C, a procedure that is known to suppress REM sleep. Cold exposure caused a significant drop in brain temperature and body temperature and also resulted in a strong and selective suppression of REM sleep by 64.9%. However, contrary to our expectation, the loss of REM sleep was not recovered during the subsequent day and night. These findings in a diurnal mammal confirm that the expression of REM sleep is highly sensitive to environmental temperature but do not support the view that REM sleep is homeostatically regulated in this species. [ABSTRACT FROM AUTHOR]

Primate-specific genes (PSGs) tend to be expressed in the brain and testis. This phenomenon is consistent with brain evolution in primates but is seemingly contradictory to the similarity of spermatogenesis among mammals. Here, using whole-exome sequencing, we identified deleterious variants of X-linked SSX1 in six unrelated men with asthenoteratozoospermia. SSX1 is a PSG expressed predominantly in the testis, and the SSX family evolutionarily expanded independently in rodents and primates. As the mouse model could not be used for studying SSX1 , we used a non-human primate model and tree shrews, which are phylogenetically similar to primates, to knock down (KD) Ssx1 expression in the testes. Consistent with the phenotype observed in humans, both Ssx1- KD models exhibited a reduced sperm motility and abnormal sperm morphology. Further, RNA sequencing indicated that Ssx1 deficiency influenced multiple biological processes during spermatogenesis. Collectively, our experimental observations in humans and cynomolgus monkey and tree shrew models highlight the crucial role of SSX1 in spermatogenesis. Notably, three of the five couples who underwent intra-cytoplasmic sperm injection treatment achieved a successful pregnancy. This study provides important guidance for genetic counseling and clinical diagnosis and, significantly, describes the approaches for elucidating the functions of testis-enriched PSGs in spermatogenesis. The importance of primate-specific genes (PSGs) in spermatogenesis is largely unknown. This study identified variants in an X-linked PSG, SSX1 , associated with male infertility. By using cynomolgus monkey and tree shrew models, this study provides a powerful experimental system for elucidating the functions of testis-enriched PSGs in spermatogenesis. [ABSTRACT FROM AUTHOR]

BACKGROUND: At present, human placental mesenchymal stem cells are rarely used in bone tissue engineering research, and the use of human placental mesenchymal stem cells in the treatment of osteoporotic fractures is likely to open new horizons for their therapeutic methods. OBJECTIVE: To investigate the mechanism of human placenta-derived mesenchymal stem cells in the treatment of tree shrews with osteoporotic fracture, and the effect of different drug delivery methods on the efficacy of tree shrews with osteoporotic fracture. METHODS: Bilateral ovaries and uterus were removed from female tree shrews to simulate postmenopausal osteoporosis, and they were naturally fed for 180 days. The osteoporotic fracture tree shrew model was established by performing a right femoral fracture. The 24 tree shrews with osteoporotic fracture were randomly divided into four groups. We adjusted the concentration of the human placenta-derived mesenchymal stem cells to 1×109 L-1. In the tail vein injection group, human placenta-derived mesenchymal stem cells were injected with 1 mL in the tail vein. In the tail vein combined with fracture injection group, human placenta-derived mesenchymal stem cells were injected with 0.5 mL in the tail vein and 0.5 mL at the fracture site. In the tail vein combined with intraperitoneal injection group, human placenta-derived mesenchymal stem cells were injected with 0.5 mL in the enterocoelia and 0.5 mL in the tail vein. In the model group, 1 mL physiological saline was injected through tail vein. From the 3rd day after the fracture, tree shrews were injected once a week and three times in a row. Eight weeks after the last treatment, bone mineral density was tested in tree shrews of each group. Three-point bone biomechanics and hematoxylin-eosin staining experiments were performed on the femurs of tree shrews in each group. The expression levels of osteocalcin, estrogen, bone alkaline phosphatase and tartrate resistant acid phosphatase were measured by ELISA in all groups. The mRNA expression levels of bone morphogenetic protein-2, osteoprotegerin and receptor activator of nuclear factor-κB ligand were measured by quantitative real time polymerase chain reaction. RESULTS AND CONCLUSION: (1) Eight weeks after the last treatment, compared with the model group, the other three groups showed increased bone mineral density, maximum load, structural stiffness and energy absorption, with tail vein injection group showed the most significant increase. (2) Serum estrogen, bone alkaline phosphatase and osteocalcin expression levels in tail vein injection group, tail vein combined with fracture injection group, and tail vein combined with intraperitoneal injection group increased significantly compared with the model group. Serum tartrate resistant acid phosphatase levels decreased significantly in the tail vein injection group, tail vein combined with fracture injection group, and tail vein combined with intraperitoneal injection group compared with the model group. These serum detection results showed the most obvious improvement in tail vein injection group. (3) Hematoxylineosin staining showed significant improvement of pathological changes in tail vein injection group and tail vein combined with fracture injection group. (4) The expression level of osteoprotegerin and bone morphogenetic protein-2 mRNA in tail vein injection group, tail vein combined with fracture injection group, and tail vein combined with intraperitoneal injection group increased to varying degrees compared with model group; the tail vein combined with fracture injection group had the highest level. (5) The expression level of receptor activator of nuclear factor-κB ligand mRNA in tail vein injection group, tail vein combined with fracture injection group, and tail vein combined with intraperitoneal injection group decreased to different degrees compared with model group, with tail vein combined with fracture injection group having the lowest level. (6) It is concluded that human placenta-derived mesenchymal stem cell transplantation can effectively improve the symptom of tree shrews with osteoporotic fracture, increase bone formation indexes such as bone alkaline phosphatase, osteocalcin and osteoprotegerin, decrease bone resorption indexes such as tartrate resistant acid phosphatase and receptor activator of nuclear factor-κB ligand, and improve bone mineral density and bone biomechanics of tree shrews. Tail vein injection group had the best results for systemic treatment and tail vein combined with fracture injection group showed better results for treatment at the fracture site. [ABSTRACT FROM AUTHOR]

Background: Nogo-66 receptor (NgR1) is a glycosylphosphatidylinositol-linked cell surface receptor with high affinity for Nogo-66. The binding of Nogo-66 to NgR1 plays a key role in inhibiting neurite growth, limiting synaptic plasticity and mediating Mammalian Reovirus (MRV) infection. The Chinese tree shrew (Tupaia belangeri chinensis) is, a new and valuable experimental animal that is widely used in biomedical research. Although susceptible to MRV, little is known about tree shrew NgR1 and its role in MRV infection. Methods: In this study, we cloned NgR1 form the Chinese tree shrew by RACE technology and analyzed its characteristics, spatial structure and its tissue expression. We also examined the expression pattern of NgR1 in the response of tree shrew primary nerve cells (tNC) to MRV1/TS/2011 infection. Results: Tree shrew NgR1 was found to have a closer relationship to human NgR1 (90.34%) than to mouse NgR1. Similar to the protein structure of human NgR1, the tree shrew NgR1 has the same leucine-rich repeat (LRR) domain structure that is capped by C-terminal and N-terminal cysteine-rich modules. The tree shrew NgR1 mRNAs were predominantly detected in the central nervous system (CNS), and tree shrew NgR1 can mediate infection by MRV1/TS/2011. Conclusions: Taken together, these results help to elucidate the function of NgR1 and provide a basis for using the tree shrew as an animal model for studies of the nervous system and infectious diseases. [ABSTRACT FROM AUTHOR]

The myodural bridge is a dense connective tissue connecting muscles and ligaments to the spinal dura mater in the atlanto-occipital interspace. Some researchers believe that the myodural bridge may play a vital physiological role. It is possible, for instance, that the prevention of spinal dura mater infoldings might be involved in regulated cerebrospinal fluid circulation. For instance, it is possible to prevent spinal dura mater infoldings, regulating cerebrospinal circulation. Bats are nocturnal and the only mammals that can perform a genuine and sustained flight, whereas tree shrews are arboreal mammals that often climb to a high altitude of about 10,000 feet. Both animals have lifestyles that are different from other previously studied mammals. The study of these two animals will shed further light on the existence of the myodural bridge in mammals. Gross anatomical dissection was used to observe the connections between the deep muscles of the neck and the dura mater at the level of the atlanto-occipital interspace. The existing structures were analyzed using conventional and special histological staining techniques. The suboccipital regions in bats and tree shrews contained the rectus capitis dorsal major (RCDma), rectus capitis dorsal minor (RCDmi), oblique capitis anterior (OCA), and oblique capitis posterior (OCP). Dense connective tissue connects the RCDmi to the posterior atlanto-occipital membrane (PAOM) and the latter to the spinal dura mater. The myodural bridge in these mammals shares a similar structure to the myodural bridge in humans. Histological analyses confirmed that the connective fibers of the myodural bridge were primarily type I collagen fibers. In this study, it is supplemented by the existence of the myodural bridge in mammals. This further demonstrates that myodural bridge widely exists in the normal anatomy of mammals. This provides morphological support for a comparative anatomical study of the physiological function of the myodural bridge. [ABSTRACT FROM AUTHOR]

Genetically engineered chymosin from the tree shrew (Tupaia belangeri chinensis) has been obtained and partially characterized for the first time. The target enzyme was produced in Escherichia coli, strain BL21(DE3). It was shown that tree shrew recombinant chymosin coagulates cow milk (Bos taurus). The total and specific milk-clotting activity of the obtained enzyme was 0.7–5.3 IMCU/mL and 8.8–16.6 IMCU/mg. The nonspecific proteolytic activity of tree shrew recombinant chymosin in relation to total bovine casein was 30 and 117% higher than that of recombinant chymosin of cow and of single-humped camel respectively. It was found that in comparison with most of the known genetically engineered chymosins, the tree shrew enzyme showed exceptionally low thermal stability. After heating at 45°C, the coagulation ability of tree shrew recombinant chymosin decreased by more than 40%, and at 50°C the enzyme lost more than 90% of the initial milk-clotting activity. The Michaelis constant (Km), enzyme turnover number (kcat), and catalytic efficiency (kcat/Km) for genetically engineered chymosin from the tree shrew were 6.3 ± 0.1 µM, 11 927 ± 3169 s–1 and 1968 ± 620 µM–1 s–1, respectively. Comparative analysis showed that the primary structure of the chymosin-sensitive site of cow kappa-casein and the supposed similar sequence of tree shrew kappa-casein differed by 75%. The ability of tree shrew recombinant chymosin to coagulate cow's milk, along with a low thermal stability and high catalytic efficiency with respect to the substrate, imitating the chymosin-sensitive site of cow kappa-casein, suggests that this enzyme is of potential interest for cheese making. [ABSTRACT FROM AUTHOR]

Epstein-Barr virus (EBV) infection in humans is ubiquitous and associated with various diseases. Remodeling of the immune microenvironment is the primary cause of EBV infection and pathogenesis; however, the underlying mechanism has not been fully elucidated. In this study, we used whole-transcriptome RNA-Seq to detect mRNAs, long non-coding RNAs (lncRNA), and microRNA (miRNA) profiles in the control group, 3 days, and 28 days after EBV infection, based on the tree shrew model that we reported previously. First, we estimated the proportion of 22 cell types in each sample using CIBERSORT software and identified 18 high-confidence DElncRNAs related to immune microenvironment regulation after EBV infection. Functional enrichment analysis of these differentially expressed lncRNAs primarily focused on the autophagy, endocytosis, and ferroptosis signalling pathways. Moreover, EBV infection affects miRNA expression patterns, and many miRNAs are silenced. Finally, three competing endogenous RNA regulatory networks were built using lncRNAs that significantly correlated with immune cell types, miRNAs that responded to EBV infection, and potentially targeted the mRNA of the miRNAs. Among them, MRPL42-AS-5 might act as an hsa-miR-296-5p "sponge" and compete with target mRNAs, thus increasing mRNA expression level, which could induce immune cell infiltration through the cellular senescence signalling pathway against EBV infection. Overall, we conducted a complete transcriptomic analysis of EBV infection in vivo for the first time and provided a novel perspective for further investigation of EBV-host interactions.

AIM:To establish the model of pseudomonas aeruginosa and staphylococcus aureus keratitis infection in tree shrews. To determine the expression of IL-17 in the bacterial infection process of tree shrews cornea, and the mechanism of IL-17 in bacterial keratitis of tree shrews is discussed.METHODS: The tree shrew bacterial keratitis models were established by the contact lens-assisted corneal scratching method. After establishing models successfully, the infection symptoms of the model were evaluated by using anterior segment photography and in vivo confocal microscopy on 1, 4, 7 and 14d after performing inoculation, and pathological sections were made to observe histopathological changes in the cornea. Samples were collected at the corresponding time points above, and the expression of IL-17 mRNA in the corneal tissues of tree shrews was detected by real-time quantitative PCR, and the expression of IL-17 protein was detected by ELISA.RESULTS:The success rate of modeling the tree shrew pseudomonas aeruginosa and staphylococcus aureus keratitis models was 96% and 100%.The clinical manifestations and inflammatory cell infiltration of the tree shrew keratitis was consistent with the changing rules of the cornea in histopathological. IL-17 gene and protein expression profiles in tree shrew corneas were consistent with the severity of corneal inflammation basically. CONCLUSION:The use of contact lens-assisted corneal scratching method can successfully establish animal models of pseudomonas aeruginosa and staphylococcus aureus keratitis in tree shrews that more closely resemble the natural course of human bacterial keratitis infection. IL-17 participated in the occurrence and development of bacterial keratitis in tree shrews.

BACKGROUND: Fibroblast-like synoviocytes play an important role in the pathological process of rheumatoid arthritis. When inflammatory arthritis occurs, fibroblast-like synoviocytes in the synovial lining layer will proliferate in large quantities, and the release of inflammatory factors during this period can cause joint inflammation and cartilage damage. OBJECTIVE: To establish methods for isolation, culture, purification, and identification of tree shrew knee joint fibroblast-like synoviocytes in vitro, and explore their biological characteristics; to establish methods for detection of TLR8 pathway related molecules in fibroblast-like synoviocytes from tree shrews, and preliminarily explore the activation of TLR8 pathway in the cells. METHODS: Fibroblast-like synoviocytes from tree shrews were isolated and purified using tissue block method and continuous passage method. Cell proliferation was detected using cell counting kit-8. Cell morphology was observed using hematoxylin-eosin staining. Immunocytochemical staining was used to detect the expression of vimentin in synoviocytes. Before and after stimulation with human TLR8 ligand R848, the expression of TLR8 and its signaling pathway proteins in tree shrew fibroblast-like synoviocytes and human fibroblast-like synoviocytes was detected using western blot assay, while the expression of TLR8 pathway and its downstream mRNAs in tree shrew fibroblast-like synoviocytes were detected using RT-PCR. RESULTS AND CONCLUSION: Under an inverted microscope, tree shrew fibroblast-like synoviocytes after 3 generations of subculture were mostly spindleshaped cells with similar size, high purity, good growth and proliferation in vitro. Hematoxylin-eosin staining revealed that the cells were mostly spindle-shaped, similar in size. Immunocytochemical staining results showed that Vimentin positively expressed in fibroblast-like synoviocytes. Cell counting kit-8 testing results showed an “S”-shaped growth curve of tree shrew fibroblast-like synoviocytes. Western blot results revealed that at 48 hours after R848 stimulation, the expression level of nuclear factor-κB protein significantly increased (P < 0.05), the expression level of p-P38 protein decreased (P < 0.05), and there was no change in the expression of TLR8, MyD88, P38, p-Erk1/2, and RANKL proteins (in tree shrew fibroblast-like synoviocytes (P > 0.05). After R848 stimulation, the expression of p-P38 in human fibroblast-like synoviocytes also significantly decreased, and no changes were found in the expression of TLR8, MyD88, P38, p-Erk1/2, and RANKL proteins (P > 0.05). Findings from RT-PCR and agarose gel electrophoresis detection showed that the mRNA expression of tumor necrosis factor ɑ, interleukin 6, interferon β, TLR9-2, TLR9-1, TLR8-2, TLR8-1, TLR7-2, and TLR7-1 mRNA expression had no significant change after 48 hours of stimulation with R848 (P > 0.05). To conclude, the tissue block adherence method can be used to isolate tree shrew fibroblast-like synoviocytes, and TLR8 pathway-related molecular detection method for tree shrew fibroblast-like synoviocytes is successfully established. [ABSTRACT FROM AUTHOR]

Hepatitis B virus (HBV) infection is a global public health problem. The clinical outcomes of HBV infections are influenced by host as well as viral factors, including viral genotypes and subgenotypes. The interplay between HBV and host innate immunity remains unclear because of the lack of a suitable small animal model. Tree shrews (Tupaia belangeri) have been utilized as a useful animal model for hepatitis viruses such as hepatitis B and C viruses. In this study, we characterized acute infections by HBV genotype F (HBV-F) wild type (Wt) and mutant type (Mt) viruses in adult tree shrews. Serum alanine aminotransferase levels were measured before and post-infection 7 and 14 dpi. Both HBV-F-Wt and Mt were detected in the HBV-F-infected tree shrew serum and liver tissue at 7 and 14 dpi. We examined the intrahepatic expression patterns of Toll-like receptors (TLRs) (TLR1-9 mRNAs), cGAS, several transcription factors such as STAT1, STAT2, IRF7, HNF4, PD-L1, and cytokines, including IFN-b, IFN-g, IL-6, and TNF-a in HBV-F Wt/Mt-infected tree shrews. When compared with uninfected animal group, significant suppression of TLR8 in HBV-F-Wt infected animals and significant suppression of PD-L1 in both HBV-F-Wt and Mt infected animals were observed. Thus, tree shrew can be a useful animal model to characterize HBV-F pathogenesis. [ABSTRACT FROM AUTHOR]

Background: The product of the SEC14L2 (SEC14 Like Lipid Binding 2) gene belongs to a family of lipid-binding proteins including Sec14p, alpha-tocopherol transfer protein, and cellular retinol-binding protein. SEC14L2 expression enables replication of clinical hepatitis C virus (HCV) isolates in several hepatoma cell lines, and mutations in SEC14L2 may enhance HCV replication in vitro. The Chinese tree shrew (Tupaia belangeri chinensis) is a potential animal model for studying HCV replication, however, the cDNA sequence, protein structure, and expression of the Chinese tree shrew SEC14L2 gene have yet to be characterized. Methods and results: In the present study, we cloned the full-length cDNA sequence of the SEC14L2 in the Chinese tree shrew by using rapid amplification of cDNA ends technology. This led us to determine that, this is 2539 base pairs (bp) in length, the open reading frame sequence is 1212 bp, and encodes 403 amino acids. Following this, we constructed a phylogenetic tree based on SEC14L2 molecules from various species and compared SEC14L2 amino acid sequence with other species. This analysis indicated that the Chinese tree shrew SEC14L2 protein (tsSEC14L2) has 96.28% amino acid similarity to the human protein, and is more closely related to the human protein than either mouse or rat protein. The Chinese tree shrew SEC14L2 mRNA was detected in all tissues, and showed highest expression levels in the pancreas, small intestine and trachea, however the tsSEC14L2 protein abundance was highest in the liver and small intestine. Conclusion: The Chinese tree shrew SEC14L2 gene was closer in evolutionary relation to humans and non-human primates and expression of the tsSEC14L2 protein was highest in the liver and small intestine. These results may provide useful information for tsSEC14L2 function in HCV infection. [ABSTRACT FROM AUTHOR]

Hepatitis B virus (HBV) infection is a global public health problem. The clinical outcomes of HBV infections are influenced by host as well as viral factors, including viral genotypes and subgenotypes. The interplay between HBV and host innate immunity remains unclear because of the lack of a suitable small animal model. Tree shrews (Tupaia belangeri) have been utilized as a useful animal model for hepatitis viruses such as hepatitis B and C viruses. In this study, we characterized acute infections by HBV genotype F (HBV-F) wild type (Wt) and mutant type (Mt) viruses in adult tree shrews. Serum alanine aminotransferase levels were measured before and post- infection 7 and 14 dpi. Both HBV-F-Wt and Mt were detected in the HBV-F-infected tree shrew serum and liver tissue at 7 and 14 dpi. We examined the intrahepatic expression patterns of Toll-like receptors (TLRs) (TLR1–9 mRNAs), cGAS, several transcription factors such as STAT1, STAT2, IRF7, HNF4, PD-L1, and cytokines, including IFN-β, IFN-γ, IL-6, and TNF-α in HBV-F Wt/Mt-infected tree shrews. When compared with uninfected animal group, significant suppression of TLR8 in HBV-F-Wt infected animals and significant suppression of PD-L1 in both HBV-F-Wt and Mt infected animals were observed. Thus, tree shrew can be a useful animal model to characterize HBV-F pathogenesis.

The lens mitochondrion of the tree shrew, located along the optical pathway between the lens and photoreceptors, has been investigated. The results suggest that the lens mitochondrion acts as a quasi-bandgap or imperfect photonic crystal. Interference effects cause a shift in the focus and introduce wavelength-dependent behavior similar to dispersion. Optical channels within the mitochondrion form a mild waveguide, preferentially propagating light within certain compartments. The lens mitochondrion also functions as an imperfect UV-shielding interference filter. Overall, this study provides insights into the dual role of the lens mitochondrion and the complex behavior of light within biological systems.

[Display omitted] Cytochromes P450 (P450s or CYPs), especially the CYP2C family, are important drug-metabolizing enzymes that play major roles in drug metabolism. Tree shrews, a non-rodent primate-like species, are used in various fields of biomedical research, notably hepatitis virus infection; however, its drug-metabolizing enzymes have not been fully investigated. In this study, tree shrew CYP2C18, CYP2C76a, CYP2C76b, and CYP2C76c cDNAs were identified and contained open reading frames of 489 or 490 amino acids with high sequence identities (70–78 %) to human CYP2Cs. Tree shrew CYP2C76a, CYP2C76b, and CYP2C76c showed higher sequence identities (79–80 %) to cynomolgus CYP2C76 and were not orthologous to any human CYP2C. Phylogenetic analysis revealed that tree shrew CYP2C18 and CYP2C76s were closely related to rat CYP2Cs and cynomolgus CYP2C76, respectively. Tree shrew CYP2C genes formed a gene cluster similar to human CYP2C genes. All four tree shrew CYP2C mRNAs showed predominant expressions in liver, among the tissue types examined; expression of CYP2C18 mRNA was also detected in small intestine. In liver, CYP2C18 mRNA was the most abundant among the tree shrew CYP2C mRNAs. In metabolic assays using human CYP2C substrates, all tree shrew CYP2Cs showed metabolic activities toward diclofenac, R,S -omeprazole, paclitaxel, and R,S -warfarin, with the activity of CYP2C18 exceeding that of the other CYP2Cs. Moreover, tree shrew CYP2C76 enzymes metabolized progesterone more efficiently than human, cynomolgus, or marmoset CYP2Cs. Therefore, these novel tree shrew CYP2Cs are expressed abundantly in liver, encode functional enzymes that metabolize human CYP2C substrates, and are likely responsible for drug clearances. [ABSTRACT FROM AUTHOR]

The putamen (Put) is necessary for habitual actions, while the nucleus caudate (Cd) is critical for goal-directed actions. However, compared with the natural reward (such as sucrose)-seeking habit, how drug-related dysfunction or imbalance between the Put and Cd is involved in cocaine-seeking habit, which is not easy to bias behavior to goal-directed actions, is absent. Therefore, in our present study, in comparison with sucrose-habitual behavior, we evaluated the distinctive changes of the two subtypes of dopamine (DA) receptors (D1R and D2R) in cocaine-seeking habitual behavior animals. Moreover, the adaptive changes of Cav1.2 and Cav1.3, as prime downstream targets of D1R and D2R respectively, were also assessed. Our results showed that a similar percentage of the animals exhibited habitual seeking behavior after cocaine or sucrose variable-interval self-administration (SA) training in tree shrews. In addition, compared with animals with non-habitual behavior, animals with cocaine habitual behavior showed higher D1Rs and Cav1.2 expression in the Put accompanied with lower D2Rs and Cav1.3 expression in the Cd. However, after sucrose SA training, animals with habitual behavior only showed lower membrane expression of D2R in the Put than animals with non-habitual behavior. These results suggested that the upregulation of D1Rs-Cav1.2 signaling may lead to hyper-excitability of the Put, and the inactivation of D2Rs-Cav1.3 signaling may result in depressed activity in the Cd. This imbalance function between the Put and Cd, which causes an inability to shift between habits and goal-directed actions, may underlie the compulsive addiction habit. [ABSTRACT FROM AUTHOR]

Simple Summary: The Chinese tree shrew, a squirrel-like mammal, has been widely used as a laboratory animal in biological research. However, the low survival rate of the pups has seriously hindered the establishment of inbred lines of this species and further limited its wider use. We found a milk substitute appropriate for artificial rearing of Chinese tree shrew pups independent of any obvious adverse effects on their survival, health, and reproductive performance compared to those of the maternally reared pups. The successful optimization of a milk substitute for the artificial rearing of Chinese tree shrew pups may increase the availability of this experimental animal. The Chinese tree shrew (Tupaia belangeri chinensis) has the potential to replace the use of non-human primates in biomedical research. To increase the availability of this species, we have undertaken the ambitious task of establishing inbred lines of the Chinese tree shrew; however, we have been hindered by a low survival rate of inbred pups. Here, we report our artificial rearing (AR) of Chinese tree shrew pups using four different milk substitutes: the formula described by Tsang and Collins (milk TC) and three commercially available milk substitutes intended for possums (milk A and milk C) and for guinea pigs (milk B). We compared the effects of these milk substitutes and maternal milk on the daily milk consumption, growth performance, and survival of the pups. We also assessed the life span and reproductive performance of the F1 individuals given the best milk substitute as compared to the maternally reared (MR) pups. Milk B was found to be appropriate for AR. Pups fed with milk B had a high survival rate at the weaning age compared to those fed with the other milk substitutes. The AR pups fed with milk B had a life span similar to that of MR pups. AR females fed with milk B had an earlier age of the first reproduction, a larger number of litters, and a higher rate of survival of the offspring at the weaning age compared with the MR females. The successful optimization of a milk substitute for AR of Chinese tree shrew pups will undoubtedly facilitate the wide usage of this experimental animal. [ABSTRACT FROM AUTHOR]

Background: Previous studies have established several animal models for experimental autoimmune uveitis (EAU) in rodents without the fovea centralis in the human retina. This study aimed to develop and explore the application of a novel EAU model in tree shrews with a cone-dominated retina resembling the human fovea. Methods: Tree shrews were clinically and pathologically evaluated for the development and characteristics of EAU immunized with six inter-photoreceptor retinoid-binding proteins (IRBPs). IRBP-specific T-cell proliferation and serum cytokine of tree shrews were evaluated to determine the immune responses. Differentially expressed genes (DEGs) were identified in the eyes of tree shrews with EAU by RNA-sequencing. The disruptive effects of the DEG RGS4 inhibitor CCG 203769 and dihydroartemisinin on the EAU were investigated to evaluate the potential application of tree shrew EAU. Results: IRBP1197–1211 and R14 successfully induced chronic EAU with subretinal deposits and retinal damage in the tree shrews. The immunological characteristics presented the predominant infiltration of microglia/macrophages, dendritic cells, and CD4-T-cells into the uvea and retina and pathogenic T helper (Th) 1 and Th17 responses. The subretinal deposits positively expressed amyloid β-protein (Aβ), CD8, and P2Y purinoceptor 12 (P2RY12). The crucial DEGs in R14-induced EAU, such as P2RY2 and adenylate cyclase 4 (ADCY4), were enriched for several pathways, including inflammatory mediator regulation of transient receptor potential (TRP) channels. The upregulated RGS4 in IRBP-induced EAU was associated with mitogen-activated protein kinase (MAPK) activity. RGS4 inhibition and dihydroartemisinin could significantly alleviate the retinal pathological injuries of IRBP1197-1211-induced EAU by decreasing the expression of CD4 T-cells. Conclusion: Our study provides a novel chronic EAU in tree shrews elicited by bovine R14 and tree shrew IRBP1197-1211 characterized by retinal degeneration, retinal damage with subretinal Aβ deposits and microglia/macrophage infiltration, and T-cell response, probably by altering important pathways and genes related to bacterial invasion, inflammatory pain, microglial phagocytosis, and lipid and glucose metabolism. The findings advance the knowledge of the pathogenesis and therapeutics of the fovea-involved visual disturbance in human uveitis. [ABSTRACT FROM AUTHOR]

This study aimed to observe the ultrastructure on the surface of the inner ear of a normal tree shrew using scanning electron microscope (SEM). The specimens of cochlea, macula utriculi, macula sacculi, and crista ampullaris of the normal adult tree shrew were collected and observed by SEM. We used immunofluorescence for cochlear protein Atoh1 staining. We observed that cochlea of the tree shrew is centered on the cochlear axis, circling about 3.5 times from bottom to top of the cochlea. The organ of Corti is located between medial and lateral grooves, including inner and outer hair cells as well as supporting cells. Maculae staticae include macula of saccule and macula of utricle, and the surface of macula is covered with a large number of otoliths. We found a gelatinous layer below the otoliths, followed by the layer of the honeycomb structure. The hair cell cilia of macula and crista ampullaris include one kinocilium and more stereocilia. There is no obvious cross structure but numerous hair cell cilia on semicircular canal crista ampullaris. Immunofluorescence staining showed that protein Atoh1 is mainly distributed in the nucleus of the cochlea's inner and outer hair cells. The observation of the inner ear structure under SEM elucidate the fine surface morphological structure of the entire cochlea, the vestibular maculae staticae, and crista ampullaris, providing new insight into the structure and function of the inner ear of tree shrew. Highlights: This article is the first to describe the inner ear ultrastructure of a small primate tree shrew by scanning electron microscopy (SEM).Under an SEM, the phalangeal processes of Deiter cells in tree shrews were observed to be connected to the tip of a neighboring hair cell, which was different from that of Deiters' cells in guinea pigs, and this crossed one hair cell, and connected to the tip of the third hair cell.It was observed that the crista ampullaris of tree shrews were horseshoe‐shaped, and similar to that of humans and monkeys, this had no obvious "cross‐shaped hump" structure.Tree shrew's ABR threshold value curve conforms to the mammalian U‐shaped curve, wave III is the main wave of ARB, its sensory frequency may be higher 8 kHz, and the characteristics of the stereocilia of tree shrew we have observed may be related to the perception of higher frequency hearing. [ABSTRACT FROM AUTHOR]

Human adenovirus (HAdV) species B can cause severe acute respiratory diseases. However, the researches to combat this infection have been hampered by the lack of an animal model permissive to the virus. Here, we report in vitro and in vivo HAdV species B infections of tree shrews, the closest relative of primates. HAdV-3, -7, -14, and -55 efficiently replicated in primary cell cultures. After intranasal inoculation of tree shrews with HAdV-55, the viral replication in the oropharyngeal region remained high until day 5 post-infection and was still detected until day 12. HAdV-55 in the lung or turbinate bone tissues reached the highest levels between days 3 and 5 post-infection, which indicated viral replication in the upper and lower respiratory tracts. HAdV-55 infection caused severe interstitial pneumonia in the animal. IL-8, IL-10, IL-17A, and IFN-γ expression in the peripheral blood mononuclear cells from infected animals was up-regulated. The pre-vaccination with HAdV-55 cleared the virus faster in the respiratory tract, mitigated lung pathological changes. Finally, HAdV-55 infection was propagated among tree shrews. Our study demonstrated that the tree shrew is a permissive animal model for HAdV species B infection and may serve as a valuable platform for testing multiple anti-viral treatments.

Abstract Background The domestication of tree shrews represents an important advance in the development of standardized laboratory animals. Little is known regarding the miRNA changes that accompany the transformation of wild tree shrews into domestic tree shrews. Results By performing miRNA-seq analysis on wild and domestic tree shrews, we identified 2410 miRNAs and 30 differentially expressed miRNAs in the hippocampus during tree shrew domestication. A KEGG analysis of the differentially expressed genes showed that the differentially expressed miRNAs were associated with ECM-receptor interaction, the phosphatidylinositol signaling system, protein digestion and absorption, inositol phosphate metabolism, lysine degradation, fatty acid degradation and focal adhesion. Most of these pathways could be classified under environmental information processing, organismal systems and metabolism. The miRNAs exclusively expressed in wild and tame tree shrews GO enriched in terms of divergent functions. The miRNA-mRNA networks suggested that novel-m1388-5p and novel-m0746-5p might play regulatory roles in domestication of tree shrews. Real–time RT-PCR analysis was employed to verify the presence of these miRNAs. Conclusion We identified a number of candidate miRNA-regulated domestication genes that may represent targets for selection during the domestication of tree shrews.

Background: This study aimed to address the lack of information on the male germ cell seasonal development of domesticated tree shrews (Tupaia belangeri chinensis).Materials and Methods: Testicular tissues were collected from 60 tree shrews (n = 5 per month). The ultrastructures of the testes and spermatids were examined via transmission electron microscopy. Apoptosis of spermatogenic cells was measured through terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining. The expression of proliferation factors, namely, proliferating cell nuclear antigen (PCNA) and Ki67, in testicular tissues was assayed through immunohistochemistry.Results: Spermatid ultrastructure showed seasonal differences, and spermatogenesis was relatively active in June and July and relatively stagnant from October to November. The percentage of TUNEL-positive germ cells was less during October and November, while greater in July than other phases. The number of PCNA-nucleus-positive germ cells was most in June and July, but with cytoplasm staining from October to November. Ki67 presented positive expression in the testes from April to September, with highest expression in June, but with no expression from October to March.Conclusions: In summary, there are seasonal differences in tissue morphology related to spermatogenesis in domesticated tree shrews. PCNA expression and Ki67 expression are good indicators of seasonal differences in male germ cells. [ABSTRACT FROM AUTHOR]

Background: Umbilical cord mesenchymal stem cell transplantation can treat metabolic syndrome, but the tracing of cells in the body after transplantation has always been a problem. Tree shrew umbilical cord mesenchymal stem cells were labeled with the dark red fluorescent dye DIR and a metabolic syndrome model in tree shrew was generated. The migration, distribution, colonization and survival of the cells were observed. Methods: Tree shrew umbilical cord mesenchymal stem cells were labeled with the dark red fluorescent dye DIR. Three days after the tree shrew model was generated, the pancreas, kidney and liver were placed in a small animal live imager to observe the distribution of the labeled cells. Result: The labeled cells showed deep red fluorescence in the live imager. After treatment with the transplanted cells, dark red fluorescent signals were observed in the liver, kidney and pancreas of the tree shrews but not in the untreated group and no dark red fluorescent signal was observed in the cell distribution. [ABSTRACT FROM AUTHOR]

Abstract Background Clostridioides difficile is a major cause of antibiotic associated diarrhea. Several animal models are used to study C. difficile infection (CDI). The tree shrew has recently been developed as a model of primate processes. C. difficile infection has not been examined in tree shrews. We infected tree shrews with hyper-virulent C. difficile strains and examined the alterations in gut microbiota using 16S rRNA gene sequencing. Results C. difficile colonized the gastrointestinal tract of tree shrew and caused diarrhea and weight loss. Histopathologic examination indicated structures and mucosal cell destruction in ileal and colonic tissues. The gut microbial community was highly diversity before infection and was dominated by Firmicutes, Fusobacteria, Bacteroidetes, and Proteobacteria. Antibiotic administration decreased the diversity of the gut microbiota and led to an outgrowth of Lactobacillus. The relative abundance of Proteobacteria, Gammaproteobacteria, Enterobacteriales, Lachnospiraceae, Enterobacteriaceae, Escherichia, Blautia, and Tyzzerella increased following C. difficile infection. These taxa could be biomarkers for C. difficile colonization. Conclusions In general, the disease symptoms, histopathology, and gut microbiota changes following C. difficile infection in tree shrews were similar to those observed in humans.