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Injectable dermal fillers, which are used for various plastic surgery purposes, are experiencing explosive growth in the market due to increasing interest in appearance management. Hyaluronic acid (HA) hydrogels have been considered an ideal material for fillers due to their high-water retention, biodegradability, and biocompatibility. However, their application is limited by shortcomings in durability and persistence caused by rapid enzymatic degradation. Therefore, in this study, we introduce acetylated hyaluronic acid-divinyl sulfone (AcHA-DVS) hydrogels for novel approach to improving the physical properties and gel retention time of HA. The AcHA-DVS hydrogels showed significant advantages in terms of longevity and performance as dermal fillers compared to HA-DVS hydrogels. These results suggest that our new AcHA-DVS hydrogel is a promising biomaterial for use as an injectable filler or scaffold of tissue engineering.

Three-dimensional (3D) culture systems that provide a more physiologically similar environment than conventional two-dimensional (2D) cultures have been extensively developed. Previously we have provided a facile method for the formation of 3D spheroids using non-adhesive N-hexanoyl glycol chitosan (HGC) hydrogel-coated dishes, but with limitations such as low gel stability and weak mechanical properties. In this study, chemically crosslinked hydrogels were prepared by photocrosslinking of methacrylated HGCs (M-HGCs), and their spheroid-forming abilities were evaluated for long-term 3D cell cultures. The M-HGC hydrogels demonstrated not only enhanced gel stability, but also good spheroid-forming abilities. Furthermore, the M-HGC-coated dishes were effective in generating spheroids of larger size and higher cell density depending on the crosslinking density of the M-HGCs. These results indicate that our hydrogel-coated dish system could be widely applied as an effective technique to produce cell spheroids with customized sizes and densities that are essential for tissue engineering and drug screening.

Dopamine-modified hyaluronic acid (DA-HA) has been initially developed as an efficient coating and adhesion material for industrial uses. However, the biological activity and safety of DA-HA in the brain have not been explored yet. Here, we report a series of evidence that DA-HA exhibits similar functionality as dopamine (DA), but with much lower toxicity arising from autoxidation. DA-HA shows very little autoxidation even after 48-hour incubation. This is profoundly different from DA and its derivatives including L-DOPA, which all induce severe neuronal death after pre-autoxidation, indicating that autoxidation is the cause of neuronal death. Furthermore, in vivo injection of DA-HA induces significantly lower toxicity compared to 6-OHDA, a well-known oxidized and toxic form of DA, and alleviates the apomorphine-induced rotational behavior in the 6-OHDA animal model of Parkinson’s disease. Our study proposes that DA-HA with DA-like functionalities and minimal toxicity can be an effective therapeutic substitute for L-DOPA in Parkinson’s disease.

BACKGROUND: Tissue engineering approaches to treat damaged bone include various tissue transplants such as autologous, allogeneic, and xenografts. Artificial materials have been widely introduced to meet the demand for graft materials, but insufficiency in supply is still not resolved. In this study, human adipose tissue, easily obtained from the human body, was harvested, and the tissue was decellularized to fabricate a decellularized human adipose tissue matrix (DM) as an alternative graft material. METHODS: Human adipose tissue was obtained via liposuction. The obtained fresh adipose tissue sample was cut into pieces then put into decellularization solution (1% antibiotic–antimycotic solution and 1% phenylmethanesulphonyl fluoride). Lipids were further removed via treatment in isopropanol. The sample was then subjected to another enzymatic digestion and lipid removal processes. The obtained decellularized adipose tissue matrix was lyophilized to form a graft material in disc shape. RESULTS: Decellularization was confirmed by nuclear staining methods and detection of RNA and DNA via PCR. Bone morphogenetic protein 2 (BMP2)-loaded DM showed the ability to form new bone tissue when implanted in subcutaneous tissue. In recovery of a mouse calvarial defect model, BMP2-loaded DM exhibited similar levels of bone tissue regeneration efficiency compared with a well-defined commercial product, BMP2-loaded CollaCote®. CONCLUSION: The DM developed in this study is expected to address the problem of insufficient supply of graft materials and contribute to the treatment of bone defects of critical size as an alternative bone graft material with preserved extracellular matrix components.

Direct lineage conversion holds great promise in the regenerative medicine field for restoring damaged tissues using functionally engineered counterparts. However, current methods of direct lineage conversion, even those using virus-mediated transgenic expression of tumorigenic factors, are extremely inefficient (~25%). Thus, advanced methodologies capable of revolutionizing efficiency and addressing safety concerns are key to clinical translation of these technologies. Here, we propose an extracellular vesicle (EV)–guided, nonviral, direct lineage conversion strategy to enhance transdifferentiation of fibroblasts to induced cardiomyocyte-like cells (iCMs). The resulting iCMs have typical cardiac Ca 2+ transients and electrophysiological features and exhibit global gene expression profiles similar to those of cardiomyocytes. This is the first demonstration of the use of EVs derived from embryonic stem cells undergoing cardiac differentiation as biomimetic tools to induce cardiac reprogramming with extremely high efficiency (>60%), establishing a general, more readily accessible platform for generating a variety of specialized somatic cells through direct lineage conversion.

Cell culture technology has evolved into three-dimensional (3D) artificial tissue models for better reproduction of human native tissues. However, there are some unresolved limitations that arise due to the adhesive properties of cells. In this study, we developed a hexanoyl glycol chitosan (HGC) as a non-cell adhesive polymer for scaffold-based and -free 3D culture. The uniform cell distribution in a porous scaffold was well maintained during the long culutre period on the HGC-coated substrate by preventing ectopic adhesion and migration of cells on the substrate. In addition, when culturing many spheroids in one dish, supplementation of the culture medium with HGC prevented the aggregation of spheroids and maintained the shape and size of spheroids for a long culture duration. Collectively, the use of HGC in 3D culture systems is expected to contribute greatly to creating excellent regenerative therapeutics and screening models of bioproducts.

Cell labeling technologies are required to monitor the fate of transplanted cells in vivo and to select target cells for the observation of certain changes in vitro. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have been transplanted for the treatment of heart injuries or used in vitro for preclinical cardiac safety assessments. Cardiomyocyte (CM) labeling has been used in these processes to facilitate target cell monitoring. However, the functional effect of the labeling agent on hiPSC-CMs has not been studied. Therefore, we investigated the effects of labeling agents on CM cellular functions. 3’-Dioctadecyloxacarbocyanine perchlorate (DiO), quantum dots (QDs), and a DNA plasmid expressing EGFP using Lipo2K were used to label hiPSC-CMs. We conclude that the hiPSC-CM labeling with DiO and QDs does not induce arrhythmogenic effects but rather improves the mRNA expression of cardiac ion channels and Ca2+ influx by L-type Ca2+ channels. Thus, DiO and QD labeling agents may be useful tools to monitor transplanted CMs, and further in vivo influences of the labeling agents should be investigated in the future.

Thermogels have been extensively utilized as one of representative in situ forming hydrogel systems for biomedical applications. However, most thermogels often suffer from a weak mechanical strength and low physical stability. To overcome these intrinsic weaknesses of conventional thermogels, we developed a new in situ crosslinkable thermogel system with enhanced and tunable physicochemical properties. Thermosensitive N-hexanoyl glycol chitosans (HGCs) were synthesized by N-hexanoylation of glycol chitosan and further modified to yield methacrylated HGCs (M-HGCs) and thiolated HGCs (SH-HGCs). A mixture of M-HGCs and SH-HGCs (M/SH-HGCs) retained not only their thermogelling properties but also their reactive functionalities for chemical crosslinking at physiological temperature. Compared to conventional thermogels, the M/SH-HGC thermogels showed enhanced mechanical properties due to physical and chemical crosslinking mechanisms. The physicochemical properties of the M/SH-HGC thermogels were characterized in terms of the sol–gel transition temperature, gelation time, mechanical strength, and biodegradability. They showed negligible toxicity in cells, and the in situ crosslinking step did not affect cell viability. These results suggest that our crosslinkable thermogel system is useful not only as a new in situ forming hydrogel but also as a biomaterial for various biomedical applications due to its thermogelling characteristics and enhanced and tunable physicochemical properties.

3D spheroids, which have the potential to bridge the gap between 2D cell culture and native tissue, are used as tissue models in many applications, particularly in cancer, stem cell, and pharmaceutical research. A considerable amount of effort has focused on the development of more relevant physiological models. However, spheroids still have limitations in that they cannot replicate the components and structure of the ECM in the natural environment. In this study, we proposed new concept of scaffold-based techniques for the generation of spheroids. Spheroids were successfully generated by single cell or small number of aggregated cells between HA particles. The size of each spheroid was uniform, a necrotic core didn't form, and the system showed high viability. The expression levels of the proteins and genes required to maintain cell-specific functions increased. Thus, our system provides more physiologically relevant models and could be applied to regenerative medicine or drug screening.

Wheatgrass and barley grass are freshly sprouted leaves of wheat and barley seeds and are rich sources of phytochemicals. This study was conducted to investigate the effects of drought stress on the biochemical compounds and antioxidant activities of barley grass and wheatgrass extracts. The grass was cultivated in an organic soil growing medium with different levels of drought stress (a control with 100% water holding capacity (WHC), mild drought stress with 75% WHC, moderate drought stress with 50% WHC, and severe drought stress with 25% WHC) in a growth chamber by controlling temperature (20/15 °C, day/night), light (12/12 h, light/dark; intensity 150 μmol m-2 s-1 with quantum dot light-emitting diodes), and relative humidity (60%) for 7 days. The drought stress showed increased levels of biochemical compounds, especially phenolics, flavonoids, and vitamin C, in both barley grass and wheatgrass extracts. The wheatgrass extracts showed 1.38-1.67 times higher phenolics, flavonoids, and vitamin C contents than the barley grass extracts did. The antioxidant (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, and nitrite-scavenging activity) and antioxidant enzymes (guaiacol peroxidase, catalase, and glutathione reductase) were the highest under severe drought stress in both barley grass and wheatgrass extracts; and the wheatgrass extracts showed 1.20-5.70 times higher antioxidant enzyme activities than the barley grass extracts did. Proper drought-stress treatment of barley grass and wheatgrass may be a convenient and efficient method to increase biochemical compounds and antioxidants in our diet to exploit the related health benefits. © 2021 Society of Chemical Industry.

The current 2D culture model systems developed for drug screening are not sufficient to reflect the characteristics of in vivo solid tumors. Therefore, more effective in vitro tumor model systems must be developed for translational studies on therapeutic drug screening and testing. Herein, we report a new ultra-low adhesion (ULA) hydrogel for generating 3D cancer cell spheroids as tumor models in vitro. N-octanoyl glycol chitosan (OGC) was synthesized and coated onto the surface of a typical cell culture dish. Cell spheroids were effectively formed on the OGC-coated surface, and phenotypes of the tumor cells were well maintained during culture. More importantly, U373-MG cells cultured on OGC-coated plates were more resistant to doxorubicin than cells cultured on typical plates. Our OGC-based ULA system may offer a convenient method for 3D cell culture to provide enhanced performance in cancer research, drug screening and toxicology.

Biofunctional polymers have been widely used to enhance the proliferation and functionality of stem cells. Here, we report the development of a new biofunctional polymer, octanoyl glycol chitosan (OGC), and demonstrate its effects on the cell cycle and stem cell function using tonsil-derived mesenchymal stem cells (TMSCs). OGC treatment (100 μg/mL) significantly increased the proliferation of TMSCs, which could be attributed to cyclin D1 up-regulation in the G1 phase of the cell cycle. Additionally, OGC enhanced the ability of TMSCs to differentiate into adipocytes, chondrocytes, and osteoblasts. Taken together, this new biofunctional polymer, OGC, can promote stemness and osteogenesis, as well as induce stem cell proliferation by enhancing the intracellular metabolic rate and regulating the cell cycle. Thus, in the future, OGC could be a potential therapeutic additive for improving stem cell function.

Discovering and developing ideal cell culture methods is important for cell biology, drug development, and cell therapy. Recent studies have explored and demonstrated the use of nanoscale structures and patterns that influence cell behavior, such as 3D scaffolds. In this study, we analyzed the effects of nanopatterned-surface dishes using chondrocytes as model cells. Chondrocytes grown on nanopatterned dishes exhibited rounded shapes. Interestingly, chondrocytes have a lower COL10 mRNA level when cultured using nanopatterned dishes. The nanopatterned dishes induced G0-/G1-phase cell cycle arrest and reduced the rate of proliferation. Our results suggest that nanoscale structures can directly control cellular behaviors and can be used for chondrocyte cell culture without causing chondrocytes to lose their functions. These results help to elucidate cellular responses and behaviors in native-like environments, and this information can be used to improve human health.

Background We investigated whether electrical stimulation via indium tin oxide (ITO) could enhance the in vitro culture of neonatal rat ventricular myocytes (NRVMs), which are important in vitro models for studying the mechanisms underlying many aspects of cardiology. Methods Cardiomyocytes were obtained from 1-day-old neonatal rat heart ventricles. To evaluate function of NRVMs cultured on ITO with electrical stimulation, the cell viability, change of cell morphology, immunochemistry using cardiac-specific antibodies, and gene expression were tested. Results Defined sarcomeric structure, cell enlargement, and increased distribution of NRVMs appeared in the presence of electrical stimulation. These characteristics were absent in NRVMs cultured under standard culture conditions. In addition, the expression levels of cardiomyocyte-specific and ion channel markers were higher in NRVMs seeded on ITO-coated dishes than in the control group at 14 days after seeding. ITO-coated dishes could effectively provide electrical cues to support the in vitro culture of NRVMs. Conclusions These results provide supporting evidence that electrical stimulation via ITO can be effectively used to maintain culture and enhance function of cardiomyocytes in vitro.

Thermogels that undergo temperature-dependent sol-gel transition have recently attracted attention as a promising biomaterial for injectable tissue engineering. However, conventional thermogels usually suffer from poor physical properties and low cell binding affinity, limiting their practical applications. Here, a simple approach for developing a new thermogel with enhanced physical properties and cell binding affinity is proposed. This thermogel (AcHA/HGC) was obtained by simple blending of a new class of polysaccharide-based thermogel, N-hexanoyl glycol chitosan (HGC), with a polysaccharide possessing good cell binding affinity, acetylated hyaluronic acid (AcHA). Gelation of AcHA/HGC was initially triggered by the thermosensitive response of HGC and gradually intensified by additional physical crosslinking mechanisms between HGC and AcHA, resulting in thermo-irreversible gelation. Compared to the thermos-reversible HGC hydrogel, the thermo-irreversible AcHA/HGC hydrogel exhibited enhanced physical stability, mechanical properties, cell binding affinity, and tissue compatibility. These results suggest that our thermo-irreversible hydrogel is a promising biomaterial for injectable tissue engineering.

Background Mucoadhesive polymers, which may increase the contact time between the polymer and the tissue, have been widely investigated for pharmaceutical formulations. In this study, we developed a new polysaccharide-based mucoadhesive polymer with thermogelling properties. Methods Hexanoyl glycol chitosan (HGC), a new thermogelling polymer, was synthesized by the chemical modification of glycol chitosan using hexanoic anhydride. The HGC was further modified to include thiol groups to improve the mucoadhesive property of thermogelling HGC. The degree of thiolation of the thiolated HGCs (SH-HGCs) was controlled in the range of 5–10% by adjusting the feed molar ratio. The structure of the chemically modified polymers was characterized by 1H NMR and ATR-FTIR. The sol-gel transition, mucoadhesiveness, and biocompatibility of the polymers were determined by a tube inverting method, rheological measurements, and in vitro cytotoxicity tests, respectively. Results The aqueous solution (4 wt%) of HGC with approximately 33% substitution showed a sol-gel transition temperature of approximately 41 °C. SH-HGCs demonstrated lower sol-gel transition temperatures (34 ± 1 and 31 ± 1 °С) compared to that of HGC due to the introduction of thiol groups. Rheological studies of aqueous mixture solutions of SH-HGCs and mucin showed that SH-HGCs had stronger mucoadhesiveness than HGC due to the interaction between the thiol groups of SH-HGCs and mucin. Additionally, we confirmed that the thermogelling properties might improve the mucoadhesive force of polymers. Several in vitro cytotoxicity tests showed that SH-HGCs showed little toxicity at concentrations of 0.1–1.0 wt%, indicating good biocompatibility of the polymers. Conclusions The resultant thiolated hexanoyl glycol chitosans may play a crucial role in mucoadhesive applications in biomedical areas.

Various nanopatterning techniques have been developed to improve cell proliferation and differentiation efficiency. As we previously reported, nanopillars and pores are able to sustain human pluripotent stem cells and differentiate pancreatic cells. From this, the nanoscale patterns would be effective environment for the co-culturing of epithelial and mesenchymal cell types. Interestingly, the nanopatterning selectively reduced the proliferative rate of mesenchymal cells while increasing the expression of adhesion protein in epithelial type cells. Additionally, co-cultured cells on the nanopatterning were not negatively affected in terms of cell function metabolic ability or cell survival. This is in contrast to conventional co-culturing methods such as ultraviolet or chemical treatments. The nanopatterning appears to be an effective environment for mesenchymal co-cultures with typically low proliferative rates cells such as astrocytes, neurons, melanocytes, and fibroblasts without using potentially damaging treatments.

Systemic injection into blood vessels is the most common method of drug administration. However, targeting drugs to the heart is challenging, owing to its dynamic mechanical motions and large cardiac output. Here, we show that the modification of protein and peptide therapeutics with tannic acid-a flavonoid found in plants that adheres to extracellular matrices, elastins and collagens-improves their ability to specifically target heart tissue. Tannic-acid-modified (TANNylated) proteins do not adsorb on endothelial glycocalyx layers in blood vessels, yet they penetrate the endothelium to thermodynamically bind to myocardium extracellular matrix before being internalized by myoblasts. In a rat model of myocardial ischaemia-reperfusion injury, TANNylated basic fibroblast growth factor significantly reduced infarct size and increased cardiac function. TANNylation of systemically injected therapeutic proteins, peptides or viruses may enhance the treatment of heart diseases.

The use of injectable hydrogel formulations have been suggested as a promising strategy for the treatment of degenerative disc disease to both restore the biomechanical function and reduce low back pain. In this work, a new thermo-sensitive injectable hydrogels with tunable thermo-sensitivity and enhanced stability were developed with N-hexanoylation of glycol chitosan (GC) for treatment of degenerative disc disease, and their physico-chemical and biological properties were evaluated. The sol-gel transition temperature of the hydrogels was controlled in a range of 23–56 °С, depending on the degree of hexanoylation and the polymer concentration. In vitro and in vivo tests showed no cytotoxicity and no adverse effects in a rat model. The hydrogel filling of the defective IVD site in an ex vivo porcine model maintained its stability for longer than 28 days. These results suggest that the hydrogel can be used as an alternative material for treatment of disc herniation.

We report a biocompatible and in situ cross-linkable hydrogel derived from hyaluronic acid via a bioorthogonal reaction and confirm the clinical potential of our hydrogel through in vivo cartilage regeneration. Gelation is attributed to copper-free click reactions between an azide and dibenzyl cyclooctyne. HA-PEG4-DBCO was synthesized and cross-linked via 4-arm PEG azide. The effects of the ratio of HA-PEG4-DBCO to 4-arm PEG azide on the gelation time, microstructure, surface morphology, equilibrium swelling, and compressive modulus were examined. The potential of a hydrogel as an injectable scaffold was demonstrated by the encapsulation of chondrocytes within the hydrogel matrix in vitro and in vivo. The results demonstrated that the hydrogel supported cell survival, and the cells regenerated cartilaginous tissue. In addition, these characteristics provide potential opportunities for the use of injectable hydrogels in tissue engineering applications.

A variety of VEGF inhibitors have been reported to treat cancers by suppressing tumor angiogenesis. Bevacizumab, a monoclonal VEGF antibody, was the first FDA approved anti-angiogenic agent for cancer treatments. However, bevacizumab shows modest therapeutic efficiency and often cause resistant problem in significant populations of cancer patients. To solve these problem, we investigated the therapeutic efficacy of siRNA drugs targeting VEGF and combination of the RNAi drug with bevacizumab for cancer treatments. For efficient VEGF siRNA delivery, chemically polymerized siRNAs were complexed with thiolated-glycol chitosan (psi(VEGF)/tGC). The poly-VEGF siRNA and thiolated-glycol chitosan formed stable nanoparticles via electrostatic interaction and chemical crosslinking, and showed high accumulation in tumor tissues resulting in efficient gene silencing. Both VEGF siRNA nanoparticles and bevacizumab had efficient therapeutic effects in tumor xenograft mouse models. Interestingly, most pronounced therapeutic efficacy was observed when the two distinct VEGF inhibitors were treated in combination revealing synergistic effects. The results showed that the psi(VEGF)/tGC nanoparticle mediated knockdown of VEGF exerts anti-tumor effects and the combination treatments with bevacizumab can extend the treatments options to conventional bevacizumab treatments for cancer therapy.

The integration of a targeted delivery with a tumour-selective agent has been considered an ideal platform for achieving high therapeutic efficacy and negligible side effects in cancer therapy. Here, we present engineered protein nanoparticles comprising a tumour-selective oncolytic protein and a targeting moiety as a new format for the targeted cancer therapy. Apoptin from chicken anaemia virus (CAV) was used as a tumour-selective apoptotic protein. An EGFR-specific repebody, which is composed of LRR (Leucine-rich repeat) modules, was employed to play a dual role as a tumour-targeting moiety and a fusion partner for producing apoptin nanoparticles in E. coli, respectively. The repebody was genetically fused to apoptin, and the resulting fusion protein was shown to self-assemble into supramolecular repebody-apoptin nanoparticles with high homogeneity and stability as a soluble form when expressed in E. coli. The repebody-apoptin nanoparticles showed a remarkable anti-tumour activity with negligible side effects in xenograft mice through a cooperative action of the two protein components with distinct functional roles. The repebody-apoptin nanoparticles can be developed as a systemic injectable and tumour-selective therapeutic protein for targeted cancer treatment.

Intro This project aimed to teach third grade students the differences between viral and bacterial infections through active learning. Presentation effectiveness and students’ retention of information were assessed using a game and post-quiz. This project addresses the school’s concern about the misunderstanding of causes and treatments of illnesses. Methods Students took a pre-quiz in order to establish their base knowledge of bacterial and viral infections. A question and answer style presentation was utilized to teach differences between viral and bacterial illnesses, as well as the appropriate management of each. An interactive game of “doctor and patient” was then played, during which students were given a bacterial or viral infection scenario and choose associated symptoms and management utilizing pre-made answer cards. Finally, a post-quiz was administered to determine short-term change in knowledge. Students were given an informational magnet and flyer to share with parents or guardians to re-enforce the information. Results Of the 20 participants that took the pre-quiz, only a subset of 18 were available to take the post-quiz. The overall analysis of post-test questions portrayed an increased number of correct answers after the presentation and game. Individually, question two was trending towards significance, with a p value of .08. Despite a lack of significance, students overall scored higher on the post-quiz and were better able to distinguish between types of infections and determine proper management. Conclusion Parents often seek the use of antibiotics for their children even when viral infections are present, which do not warrant antibiotic interventions. Understanding the signs, symptoms, and differences between viral and bacterial infections may help community members seek appropriate care and may reduce requests for antibiotics. It is more likely that community members will use antibiotics correctly if they have a better understanding of when they are warranted. In future studies, with larger parameters, a significant difference can be made in children and their families’ understanding of antibiotics, reducing misuse and misunderstanding within the community as a whole. Limitations Given the overall small sample size in our study, the data were limited statistically and may not be generalizable. Additionally, two students that took the pre-test quiz were not available to take the post- test, further limiting our sample size. We did not pair data between the pre-test and post-test due to a desire to preserve student anonymity. This pairing may have allowed for further analysis of specific results.

Stem cell therapy offers promising solutions to diseases and injuries that traditional medicines and therapies can't effectively cure. To get and explain their full therapeutic potentials, the survival, viability, integration, homing, and differentiation of stem cells after transplant must be clearly understood. To meet these urgent needs, noninvasive stem cell imaging and tracking technologies have been developed. Metabolic labeling technique is one of the most powerful tools for live cell imaging and tracking. In addition, it has many advantages for in vivo live cell imaging and tracking such as low background, correlation of survival, and very toxic and nontoxic by-products. Herein, we described the fundamental information and process of metabolic labeling techniques and suggested optimal condition for in vitro and in vivo imaging and tracking of human umbilical cord blood-derived endothelial progenitor cells (hUCB-EPCs). Based on this study, metabolic labeling techniques can be helpful for understanding the safety and effectiveness of stem cell-based therapy and determining the utility of stem cells in downstream experiments.

Stem cell therapy offers promising solutions to diseases and injuries that traditional medicines and therapies can't effectively cure. To get and explain their full therapeutic potentials, the survival, viability, integration, homing, and differentiation of stem cells after transplant must be clearly understood. To meet these urgent needs, noninvasive stem cell imaging and tracking technologies have been developed. Metabolic labeling technique is one of the most powerful tools for live cell imaging and tracking. In addition, it has many advantages for in vivo live cell imaging and tracking such as low background, correlation of survival, and very toxic and nontoxic by-products. Herein, we described the fundamental information and process of metabolic labeling techniques and suggested optimal condition for in vitro and in vivo imaging and tracking of human umbilical cord blood-derived endothelial progenitor cells (hUCB-EPCs). Based on this study, metabolic labeling techniques can be helpful for understanding the safety and effectiveness of stem cell-based therapy and determining the utility of stem cells in downstream experiments.

Human embryonic stem cells-derived endothelial progenitor cells (hEPCs) were utilized as cell therapeutics for the treatment of ischemic diseases. However, in vivo tracking of hEPCs for predicting their therapeutic efficacy is very difficult. Herein, we developed bioorthogonal labeling strategy of hEPCs that could non-invasively track them after transplantation in hind limb ischemia models. First, hEPCs were treated with tetraacylated N-azidomannosamine (Ac4ManNAz) for generating unnatural azide groups on the hEPCs surface. Second, near-infrared fluorescence (NIRF) dye, Cy5, conjugated dibenzocylooctyne (DBCO-Cy5) was chemically conjugated to the azide groups on the hEPC surface via copper-free click chemistry, resulting Cy5-hEPCs. The bioorthogonally labeled Cy5-hEPCs showed strong NIRF signal without cytotoxicity and functional perturbation in tubular formation, oxygen consumption and paracrine effect of hEPCs in vitro. In hind limb ischemia models, the distribution and migration of transplanted Cy5-hEPCs were successfully monitored via fluorescence molecular tomography (FMT) for 28 days. Notably, blood reperfusion and therapeutic neovascularization effects were significantly correlated with the initial transplantation forms of Cy5-hEPCs such as 'condensed round shape' and 'spread shape' in the ischemic lesion. The condensed transplanted Cy5-hEPCs substantially increased the therapeutic efficacy of hind limb ischemia, compared to that of spread Cy5-hEPCs. Therefore, our new stem cell labeling strategy can be used to predict therapeutic efficacy in hind limb ischemia and it can be applied a potential application in developing cell therapeutics for regenerative medicine.

Bleeding is largely unavoidable following syringe needle puncture of biological tissues and, while inconvenient, this typically causes little or no harm in healthy individuals. However, there are certain circumstances where syringe injections can have more significant side effects, such as uncontrolled bleeding in those with haemophilia, coagulopathy, or the transmission of infectious diseases through contaminated blood. Herein, we present a haemostatic hypodermic needle able to prevent bleeding following tissue puncture. The surface of the needle is coated with partially crosslinked catechol-functionalized chitosan that undergoes a solid-to-gel phase transition in situ to seal punctured tissues. Testing the capabilities of these haemostatic needles, we report complete prevention of blood loss following intravenous and intramuscular injections in animal models, and 100% survival in haemophiliac mice following syringe puncture of the jugular vein. Such self-sealing haemostatic needles and adhesive coatings may therefore help to prevent complications associated with bleeding in more clinical settings.

Many researchers have focused on the role of adipocytes in increasing efficient bone tissue engineering and osteogenic differentiation of stem cells. Previous reports have not reached a definite consensus on whether adipocytes positively influence in vitro osteogenic differentiation and in vivo bone formation. We investigated the adipocyte influence on osteogenic differentiation from adipose-derived stromal cells (ADSCs) and bone formation through histological analysis in vitro and in vivo. Using the direct co-culture system, we analyzed the influence of adipocytes to promote the differentiation fate of ADSCs. Using co-transplantation of ADSC-derived adipocytes and osteoblasts into the dorsal region of mice, the osteogenesis and bone quality were determined by histological morphology, radiography, and the measurement of the Ca2+ concentration. The adipocyte negatively affected the osteoblast differentiation of ADSCs in the in vitro system and induced osteogenesis of osteoblasts in the in vivo system through co-transplantation. Interestingly, in the co-transplanted adipocytes and osteoblasts, the bone formation areas decreased in the osteoblast only group compared with the mixed adipocytes and osteoblast group 6 weeks after transplantation. Conversely, co-transplantation and osteoblast transplantation had similar degrees of calcification as observed from radiography analysis and the measurement of the Ca2+ concentrations. Our results revealed that adipocytes inhibited osteoblast differentiation in vitro but enhanced the efficacy of osteogenesis in vivo. In addition, the adipocytes controlled the activity of osteoclasts in the newly formed bone tissue. Our approach can be used to reconstruct bone using stem cell-based tissue engineering and to enhance the understanding of the role adipocytes play.

The major limitations of typical thermogelling polymers for practical applications are low gel stability and weak mechanical properties under physiological conditions. In this study, we have synthesized a new polysaccharide-based thermogelling polymer that can be photo-crosslinked by UV irradiation to form a mechanically resilient and elastic hydrogel. Methacrylated hexanoyl glycol chitosan (M-HGC), was synthesized by a series of chemical modifications, N-hexanoylation and N-methacrylation, of glycol chitosan (GC). Various M-HGC polymers with different methacryl group contents were synthesized and their thermogelling and photo-crosslinkable properties were evaluated. The M-HGCs demonstrated a thermo-reversible sol-gel transition behavior in aqueous solutions. The thermally-induced hydrogels could be chemically crosslinked by UV-triggered photo-crosslinking. From the cytotoxicity studies using MTT and the live/dead assay, the M-HGC hydrogels showed non-cytotoxicity. These photo-crosslinkable thermogelling M-HGC polymers may hold great promises for various biomedical applications, such as an injectable delivery system and 3D cell culture.