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Purpose: Exfoliation syndrome (XFS) is a systemic connective tissue disorder with elusive pathophysiology. We hypothesize that a mouse model with elastic fiber defects caused by lack of lysyl oxidase like 1 (LOXL1 encoded by Loxl1), combined with microfibril deficiency due to Fbn1 mutation (encoding fibrillin-1, Fbn1 C1041G/+ ) will display ocular and systemic phenotypes of XFS., Methods: Loxl1 -/- was crossed with Fbn1 C1041G/+ to create double mutant (dbm) mice. Intraocular pressure (IOP), visual acuity (VA), electroretinogram (ERG), and biometry were characterized in 4 genotypes (wt, Fbn1 C1041G/+ , Loxl1 -/- , dbm) at 16 weeks of age. Optic nerve (ON) area was measured by ImageJ, and axon counting was achieved by AxonJ. Deep whole-body phenotyping was performed in wt and dbm mice. Two-tailed Student t test was used for statistical analysis., Results: There was no difference in IOP between the 4 genotypes. VA was significantly reduced only in dbm mice. The majority of biometric parameters showed significant differences in all 3 mutant genotypes compared with wt, and dbm had exacerbated anomalies compared with single mutants. Dbm mice showed reduced retinal function and significantly enlarged ON area compared with wt. Dbm mice exhibited severe systemic phenotypes related to abnormal elastic fibers, such as pelvic organ prolapse and cardiovascular and pulmonary abnormalities., Conclusions: Ocular and systemic findings in dbm mice support functional overlap between fibrillin-1 and LOXL1, 2 prominent components of exfoliation material. Although no elevated IOP or reduction of axon numbers was detected in dbm mice at 16 weeks of age, their reduced retinal function and enlarged ON area indicate early retinal ganglion cell dysfunction. Dbm mice also provide insight on the link between XFS and systemic diseases in humans. NOTE: Publication of this article is sponsored by the American Ophthalmological Society., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background and Aims: Diagnosing end-stage primary cicatricial alopecia (PCA) on routine histology is challenging since the major diagnostic feature (inflammatory infiltrate) may be minimal or absent. This study aimed to assess various staining patterns and diagnostic utility of elastic tissue staining by Verhoeff-Van Gieson (VVG) method and trichoscopy in PCA., Study Design: Cross-sectional study., Methods: Fifty-three patients clinically diagnosed with PCA underwent biopsy and trichoscopy in this cross-sectional study. Clinically active edge, if present, was biopsied. Twenty serial tissue sections were stained using H&E and VVG stain. Clinicopathological diagnoses were lichen planopilaris (LPP), discoid lupus erythematosus (DLE), folliculitis decalvans and unclassified PCA (UPCA) in 30 (56.6%), 11 (20.75%), 1 (1.9%) and 11 (20.75%) patients, respectively. Utility of VVG stain was ascertained considering clincopathological correlation (CPC) as the reference standard. Association of characteristic trichoscopic and VVG staining patterns was ascertained., Results: Diagnostic definition was achieved on VVG staining in 19/30 sections of LPP (wedge-shaped pattern) with 63.33% sensitivity; 7/11 cases of DLE (absent upper and mid dermal elastic fibres) with 63.64% sensitivity and 7/11 cases of UPCA (wedge-shaped pattern-3/7; recoil pattern-4/7). Routine histology suggested diagnosis only in 13/53 sections (24.52%). However, diagnosis on VVG staining corresponded with diagnosis on CPC in 33/53 cases (62.3%). Comparison of H&E versus VVG stain both overall and in the LPP and UPCA cohorts proved utility of VVG staining using Fisher's exact test (p<0.05). Statistical significance was also noted when trichoscopy was correlated with patterns on VVG staining (p<0.05)., Conclusion: Increased diagnostic yield is noted with trichoscopy and VVG stain in PCA especially when routine histopathology is non-diagnostic., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Some colorectal cancers (CRCs) are clinically diagnosed as cT4a with　serosal invasion (SI). However, the cT4a is most often underdiagnosed pathologically as pT3 without SI by hematoxylin-eosin (H&E) staining alone. Using Elastica van Gieson (EVG) staining, some pT3 tumors invade the elastic lamina (EL), which extends just below the serosal layer. Recently, EL invasion (ELI) has been described as a poor prognostic factor for disease-free survival (DFS) and overall survival (OS) in patients with pStage II CRC. However, its clinicopathological significance remains unclear due to the limited number of studies and poor understanding of ELI., Objective: This study investigated the association between the ELI and patient prognosis., Methods: After 1982, pathological diagnosis was routinely performed using H&E and EVG staining methods, and long-term follow up was performed until 2016. All clinicopathological features including ELI were prospectively registered into our computer and 569 patients with pStage II CRC were collected from the database. Based on the ELI status, pT3 was divided into three pathological categories: pT3ELI - was defined as pT3a, pT3ELI + as pT3b and unidentified EL (pT3EL -) as pT3u., Results: Using H&E staining alone, gross cT4a was most often pathologically underdiagnosed as pT3 (93.8%) and very rarely as pT4a, resulting in a large diagnostic discrepancy. Using EVG staining, 60.7% of the cT4a tumors were diagnosed as pT3b. The 10-year DFS and OS rates were similar for pT3a and pT3u patients. However, the 10-year DFS and OS rates of pT3b patients were significantly lower than those of pT3a patients (75.6% vs. 95.6%, p < 0.0001 and 58.4% vs. 70.6%, p = 0.0024, respectively) but did not differ from those of pT4a patients (70.6%, p = 0.5799 and 52.0%, p = 0.1116, respectively). Multivariate analysis revealed that the ELI was the strongest independent risk factor for recurrence and CRC-specific death (p < 0.0001)., Conclusions: A better understanding of the ELI allows us to reconsider the diagnostic discrepancy of serosal invasion, i.e., pT3b should be considered pT4a. The ELI-based subclassification of pT3 is expected to be incorporated into the TNM staging system in the future. The ELI is a notable prognostic indicator in patients with pStage II CRC., (© 2024. The Author(s).)

Pulmonary emphysema involves progressive destruction of alveolar walls, leading to enlarged air spaces and impaired gas exchange. While the precise mechanisms responsible for these changes remain unclear, there is growing evidence that the extracellular matrix plays a critical role in the process. An essential feature of pulmonary emphysema is damage to the elastic fiber network surrounding the airspaces, which stores the energy needed to expel air from the lungs. The degradation of these fibers disrupts the mechanical forces involved in respiration, resulting in distension and rupture of alveolar walls. While the initial repair process mainly consists of elastin degradation and resynthesis, continued alveolar wall injury may be associated with increased collagen deposition, resulting in a mixed pattern of emphysema and interstitial fibrosis. Due to the critical role of elastic fiber injury in pulmonary emphysema, preventing damage to this matrix component has emerged as a potential therapeutic strategy. One treatment approach involves the intratracheal administration of hyaluronan, a polysaccharide that prevents elastin breakdown by binding to lung elastic fibers. In clinical trials, inhalation of aerosolized HA decreased elastic fiber injury, as measured by the release of the elastin-specific cross-linking amino acids, desmosine, and isodesmosine. By protecting elastic fibers from enzymatic and oxidative damage, aerosolized HA could alter the natural history of pulmonary emphysema, thereby reducing the risk of respiratory failure.

Type 2 diabetes (T2D) constitutes a major public health problem, and despite prevention efforts, this pandemic disease is one of the deadliest diseases in the world. In 2022, 6.7 million patients with T2D died prematurely from vascular complications. Indeed, diabetes increases the risk of myocardial infarction or stroke eightfold. The identification of the molecular factors involved in the occurrence of cardiovascular complications and their prevention are therefore major axes. Our hypothesis is that factors brought into play during physiological aging appear prematurely with diabetes progression. Our study focused on the aging of the extracellular matrix (ECM), a major element in the maintenance of vascular homeostasis. We characterized the morphological and functional aspects of aorta, with a focus on the collagen and elastic fibers of diabetic mice aged from 6 mo to nondiabetic mice aged 6 mo and 20 mo. The comparison with the two nondiabetic models (young and old) highlighted an exacerbated activity of proteases, which could explain a disturbance in the collagen accumulation and an excessive degradation of elastic fibers. Moreover, the generation of circulating elastin-derived peptides reflects premature aging of the ECM. These extracellular elements contribute to the appearance of vascular rigidity, often the origin of pathologies such as hypertension and atherosclerosis. In conclusion, we show that diabetic mice aged 6 mo present the same characteristics of ECM wear as those observed in mice aged 20 mo. This accelerated aortic wall remodeling could then explain the early onset of cardiovascular diseases and, therefore, the premature death of patients with T2D. NEW & NOTEWORTHY Aortic elastic fibers of young (6-mo old) individuals with diabetes degrade prematurely and exhibit an appearance like that found in aged (20-mo old) nondiabetic mice. Exacerbated elastolysis and elastin-derived peptide production are characteristic elements, contributing to early aortic wall rigidity and hypertension development. Therefore, limiting this early aging could be a judicious therapeutic approach to reduce cardiovascular complications and premature death in patients with diabetes.

Marfan syndrome (MFS) is a hereditary condition accompanied by disorders in the structural and regulatory properties of connective tissue, including elastic fibers, due to a mutation in the gene encodes for fibrillin-1 protein (FBN1 gene) and the synthesis of abnormal fibrillin-1 glycoprotein. Despite the high potential of mast cells (MCs) to remodel the extracellular matrix (ECM), their pathogenetic significance in MFS has not been considered yet. The group of patients with Marfan syndrome included two mothers and five children (three girls aged 4, 11, and 11 and two boys aged 12 and 13). Normal skin was examined in two children aged 11 and 12. Histochemical, monoplex, and multiplex immunohistochemical techniques; combined protocols of simultaneous histochemical and immunohistochemical staining (the results of staining were assessed using light, epifluorescence, and confocal microscopy); and bioinformatics algorithms for the quantitative analysis of detected targets were used to evaluate mast cells and their relationship with other cells from extracellular structures in the skin dermis. Analysis of the skin MC population in children with Marfan syndrome revealed a considerably increased number of intra-organic populations with the preservation of the specific Tryptase + Chymase + CPA3 + protease profile typical of the skin. The features of the MC histotopography phenotype in MFS consisted of closer colocalization with elastic fibers, smooth muscle cells, and fibroblasts. MCs formed many intradermal clusters that synchronized the activity of cell functions in the stromal landscape of the tissue microenvironment with the help of spatial architectonics, including the formation of cell chains and the creation of fibrous niches. In MCs, the expression of specific proteases, TGF-β, and heparin increased, with targeted secretion of biologically active substances relative to the dermal elastic fibers, which had specific structural features in MFS, including abnormal variability in thickness along their entire length, alternating thickened and thinned areas, and uneven surface topography. This paper discusses the potential role of MCs in strain analysis (tensometry) of the tissue microenvironment in MFS. Thus, the quantitative and qualitative rearrangements of the skin MC population in MFS are aimed at altering the stromal landscape of the connective tissue. The results obtained should be taken into account when managing clinical signs of MFS manifested in other pathogenetically critical structures of internal organs, including the aorta, tendons, cartilage, and parenchymal organs.

In infantile abusive head injury (AHT), subdural haemorrhage (SDH) is commonly held to result from traumatic damage to bridging veins traversing from the surface of the brain to the dura and dural venous sinuses. However, there are limited published radiological or autopsy demonstrations of ruptured bridging veins and several authors also assert that bridging veins are too large to rupture due to the forces associated with AHT. There have been several studies on the size, locations and numbers of adult bridging veins and there is one small study of infant bridging veins. However, there are no microscopic studies of infant bridging veins and only a select few ultrastructural investigations of adult bridging veins. Hitherto, it has been assumed that bridging veins from infants and younger children will display the same anatomical characteristics as those in adulthood. At 19 neonatal, infant and young child post-mortem examinations, we macroscopically examined and sampled bridging veins for microscopy. We compared the histology of those samples with bridging veins from an older child and two adults. We demonstrate that adult bridging veins are usually surrounded by supportive meningeal tissue that appears to be lacking or minimally present around the bridging veins of younger children. Neonatal, infant and young children's veins had a free 'bridging' section. Neonatal and infant bridging veins had smaller diameter ranges and thinner walls (some only 5-7 µm) than those seen in older children and adults. Bridging vein walls contained both fine strands of elastic fibers and a more pronounced elastic lamina. The presence of an elastic lamina occurred more frequently in the older age groups These anatomical differences between the veins of adults and young children may help to explain apparent increased vulnerability of neonatal/infant bridging veins to the forces associated with a shaking-type traumatic event., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Two major constituents of exfoliation material, fibrillin-1 and lysyl oxidase-like 1 (encoded by FBN1 and LOXL1), are implicated in exfoliation glaucoma, yet their individual contributions to ocular phenotype are minor. To test the hypothesis that a combination of FBN1 mutation and LOXL1 deficiency exacerbates ocular phenotypes, the pan-lysyl oxidase inhibitor β-aminopropionitrile (BAPN) was used to treat adult wild-type (WT) mice and mice heterozygous for a missense mutation in Fbn1 (Fbn1 C1041G /+ ) for 8 weeks and their eyes were examined. Although intraocular pressure did not change and exfoliation material was not detected in the eyes, BAPN treatment worsened optic nerve and axon expansion in Fbn1 C1041G/+ mice, an early sign of axonal damage in rodent models of glaucoma. Disruption of elastic fibers was detected only in Fbn1 C1041G/+ mice, which increased with BAPN treatment, as shown by histologic and immunohistochemical staining of the optic nerve pia mater. Transmission electron microscopy showed that Fbn1 C1041G/+ mice had fewer microfibrils, smaller elastin cores, and a lower density of elastic fibers compared with WT mice in control groups. BAPN treatment led to elastin core expansion in both WT and Fbn1 C1041G/+ mice, but an increase in the density of elastic fiber was confined to Fbn1 C1041G/+ mice. LOX inhibition had a stronger effect on optic nerve and elastic fiber parameters in the context of Fbn1 mutation, indicating the Marfan mouse model with LOX inhibition warrants further investigation for exfoliation glaucoma pathogenesis., Competing Interests: Disclosure Statement None declared., (Copyright © 2024 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Background: Atrophic acne scarring is a common sequela of inflammatory acne, causing significant problems for affected patients. Although prolonged inflammation and subsequent aberrant tissue regeneration are considered the underlying pathogenesis, the role of epidermal stem cells, which are crucial to the regeneration of pilosebaceous units, remains unknown., Objectives: To examine the changes occurring in epidermal stem cells in atrophic acne scars., Methods: Changes in collagen, elastic fibre and human leukocyte antigen (HLA)-DR expression were analysed in normal skin and inflammatory acne lesions at days 1, 3 and 7 after development. The expression of epidermal stem cell markers and proliferation markers was compared between normal skin and mature atrophic acne scar tissue., Results: In acne lesions, inflammation had invaded into pilosebaceous units over time. Their normal structure had been destructed and replaced with a reduced amount of collagen and elastic fibre. Expression of stem cell markers including CD34, p63, leucine-rich repeat-containing G protein-coupled receptor (LGR)6 and LGR5, which are expressed in the interfollicular epidermis, isthmus and bulge of hair follicles, significantly decreased in atrophic acne scar tissue compared to normal skin. Epidermal proliferation was significantly reduced in scar tissue., Conclusions: These findings suggest that as inflammatory acne lesions progress, inflammation gradually infiltrates the pilosebaceous unit and affects the resident stem cells. This disruption impedes the normal regeneration of the interfollicular epidermis and adnexal structures, resulting in atrophic acne scars., (© 2024 Australasian College of Dermatologists.)

Pseudoxanthoma elasticum (PXE) is a rare disease characterized by ectopic calcification, however, despite the widely spread effect of pro/anti-calcifying systemic factors associated with this genetic metabolic condition, it is not known why elastic fibers in the same patient are mainly fragmented or highly mineralized in clinically unaffected (CUS) and affected (CAS) skin, respectively. Cellular morphology and secretome are investigated in vitro in CUS and CAS fibroblasts. Here we show that, compared to CUS, CAS fibroblasts exhibit: a) differently distributed and organized focal adhesions and stress fibers; b) modified cell-matrix interactions (i.e., collagen gel retraction); c) imbalance between matrix metalloproteinases and tissue inhibitor of metalloproteinases; d) differentially expressed pro- and anti-calcifying proteoglycans and elastic-fibers associated glycoproteins. These data emphasize that in the development of pathologic mineral deposition fibroblasts play an active role altering the stability of elastic fibers and of the extracellular matrix milieu creating a local microenvironment guiding the level of matrix remodeling at an extent that may lead to degradation (in CUS) or to degradation and calcification (in CAS) of the elastic component. In conclusion, this study contributes to a better understanding of the mechanisms of the mineral deposition that can be also associated with several inherited or age-related diseases (e.g., diabetes, atherosclerosis, chronic kidney diseases)., (© 2024. The Author(s).)

Background: Microneedling is a technique of repeated puncturing or drilling of the skin to induce repair and collagen induction. There are many reported important factors determining the efficacy of microneedling treatment. The extent of injury needed to produce the desired effect in each condition is one of these important factors., Objectives: We designed the present split-face comparative study to evaluate the use and effectiveness of two different depths of penetration of Dermapen needles in the management of atrophic postacne scars., Patients and Methods: The present study involved 14 subjects with atrophic postacne scars. In each patient, both sides of the face were treated with six sessions of microneedling, using Dermapen at 2-week intervals. A split-face study design was performed. The right (Rt) side of the face was treated with Dermapen using 2.5 mm needle length, while the left (Lt) side was treated using 1.5 mm needle length., Results: There was a significantly better percentage of improvement of acne scars on the Rt side of the face compared to the Lt side (P = 0.02) after six sessions. Both sides of the face showed improvement of collagen bundles and elastic fibers characteristics after six sessions., Conclusions: The use of 2.5 mm depth proved to be more effective both clinically and histologically in the management of atrophic postacne scars., (© 2023 the International Society of Dermatology.)

Background: To evaluate the presence of myofibroblasts (MFs) in the development of lip carcinogenesis, through the correlation of clinical, histomorphometric and immunohistochemical parameters, in actinic cheilitis (ACs) and lower lip squamous cell carcinomas (LLSCCs)., Methods: Samples of ACs, LLSCCs, and control group (CG) were prepared by tissue microarray (TMA) for immunohistochemical TGF-β, α-SMA, and Ki-67 and histochemical hematoxylin and eosin, picrosirius red, and verhoeff van gieson reactions. Clinical and microscopic data were associated using the Mann-Whitney, Kruskal-Wallis/Dunn, and Spearman correlation tests (SPSS, p < 0.05)., Results: ACs showed higher number of α-SMA + MFs when compared to CG (p = 0.034), and these cells were associated with the vertical expansion of solar elastosis (SE) itself (p = 0.027). Areas of SE had lower deposits of collagen (p < 0.001), immunostaining for TGF-β (p < 0.001), and higher density of elastic fibers (p < 0.05) when compared to areas without SE. A positive correlation was observed between high-risk epithelial dysplasia (ED) and the proximity of SE to the dysplastic epithelium (p = 0.027). LLSCCs showed a higher number of α-SMA + MFs about CG (p = 0.034), as well as a reduction in the deposition of total collagen (p = 0.009) in relation to ACs and CG. There was also a negative correlation between the amount of α-SMA + cells and the accumulation of total collagen (p = 0.041). Collagen and elastic density loss was higher in larger tumors (p = 0.045) with nodal invasion (p = 0.047)., Conclusions: Our findings show the possible role of MFs, collagen fibers, and elastosis areas in the lip carcinogenesis process., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Varicose veins affect approximately 25% of people in industrialized countries., Methods: The study aimed at detecting apoptotic cells and histopathological changes in varicose vein walls. Patients (N.=41) with varicose veins and 30 control group patients were divided into two groups according to their age (younger and older than 50 years). Apoptosis was determined by the TUNEL assay, elastin and collagen IV expression by immunohistochemistry and ultrastructural changes by transmission electron microscopy., Results: The results show that the number of apoptotic cells in the layers of varicose veins increased, in particular in a group of patients aged over 50 years. In the varicose veins as compared to control veins the elastic fibers were found to be thinner, more fragmented and disorderly arranged. Elastin and collagen IV expression was found to decline in the intima and the media of varicose veins in both age groups. Electron microscopy demonstrated hypertrophy and degeneration of smooth muscle cells. Furthermore, cells with ultrastructural feature of apoptosis were noted. In the disorganized and expanded extracellular matrix membrane-bound vesicles, ghost bodies with different size and electron density were observed. Ghost bodies seem to bud off from smooth muscle cells and are likely to be involved in extracellular matrix remodeling as they are seen in close contact with collagen fibers., Conclusions: The study demonstrates increase of apoptotic cells in the wall of varicose veins along with vein wall structural abnormalities including alterations of smooth muscle cells and decline of elastin and collagen IV expression.

Objective: To compare the collagen, elastic fibers, and smooth muscle content of the clitoris and the glans penis in young adults., Materials and Methods: The clitoris and the glans penis of six women and six men (mean age 25±3) who died as a result of accidents were excised. The samples were placed under a formaldehyde solution and histologically processed. Masson's trichrome and Weigert's resorcin-fuchsin stain was used to highlight the elastic fibers, smooth muscle, and collagen. Stereological analysis was conducted in 5 random fields of 5 slides for each sample. For statistical analysis, the unpaired t-test was used to compare values between groups, and a value of P<0.05 was considered as significant for all analyses., Results: Stereology revealed a mean smooth muscle content of 35.84±6.46% and 31.64±4.74% for the clitoris and glans penis, respectively, while it also revealed collagen content of 26.11±7.41% and 28.44±3.55% and elastic fibers content of 24.12±4.34% and 30.97±6.13% for the clitoris and glans penis, respectively. The statistical analysis showed no significant differences between them., Conclusion: Regardless of anatomical differences, the volumetric density of collagen, elastic fibers, and smooth muscle were similar for the clitoris and glans penis in young adults, a feature possibly explained by their embryology., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

Moyamoya disease (MMD) is a cerebrovascular disease which is characterized by the chronic progression of steno-occlusive changes at the terminal portion of internal carotid arteries and the development of "moyamoya vessels." Dysregulation of the extracellular matrix is regarded as a key pathophysiology underlying unique vascular remodeling. Here, we measured the concentration of elastin crosslinkers desmosine and isodesmosine in the plasma of MMD patients. We aimed to reveal its diagnostic values of desmosines in the progression of steno-occlusive lesions. The concentrations of plasma desmosines were determined by liquid chromatography-tandem mass spectrometry. The temporal profiles of steno-occlusive lesions on magnetic resonance angiography were retrospectively evaluated, and the correlation between the progression of steno-occlusive changes in intracranial arteries and plasma desmosines concentrations was further analyzed. Plasma desmosines were significantly higher in MMD patients with disease progression compared to MMD patients without disease progression. Also, the incidence of disease progression was higher in MMD patients with plasma desmosines levels over limit of quantitation (LOQ) than those with plasma desmosines levels below LOQ. In conclusion, plasma desmosines could be potential biomarkers to predict the progression of steno-occlusive changes in MMD patients., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Oral submucous fibrosis (OSMF) is a habit related potentially malignant disorder seen mainly in South Asian people. The malignancy arising from OSMF has been regarded as low grade with better outcome. The present study was orchestrated to histochemically analyze collagen and elastic fibres in OSMF without dysplasia, OSMF with dysplasia and OSMF turning malignant., Materials and Methods: 100 cases (80 cases and 20 healthy controls) were included after obtaining clearance from ethical committee. All cases were subjected to Van Gieson staining for collagen and a novel simple method for elastic fibres (Orcein staining). Data were analyzed using SPSS software., Results: Controls showed haphazard arrangement of collagen and elastic fibres. The collagen bundles were parallelly arranged in OSMF without dysplasia and OSMF with dysplasia; the collagen was however haphazard in cases of OSMF turning malignant. As with collagen, elastic fibres were also haphazardly arranged in the control group; in contrast, the elastic fibres were predominantly arranged in a criss-cross pattern in the other study groups. The difference in orientation and density among the groups was statistically significant., Conclusion: With advancement of stage there is increased collagenization of OSMF, as the condition acquires dysplastic changes and turns malignant, microenvironment alters resulting in increased activity of collagenases. However, the arrangement of more resistant elastic fibres depicts the better outcome, once OSMF shows malignant transformation, limiting locoregional and distant spread., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder caused by mutations in fibrillin 1 (FBN1) gene. These mutations result in defects in the skeletal, ocular, and cardiovascular systems. Aortic aneurysm is the leading cause of premature mortality in untreated MFS patients. Elastic fiber fragmentation in the aortic vessel wall is a hallmark of MFS-associated aortic aneurysms. FBN1 mutations result in FBN1 fragments that also contribute to elastic fiber fragmentation. Although recent research has advanced our understanding of MFS, the contribution of elastic fiber fragmentation to the pathogenesis of aneurysm formation remains poorly understood. This review provides a comprehensive overview of the molecular mechanisms of elastic fiber fragmentation and its role in the pathogenesis of aortic aneurysm progression. Increased comprehension of elastic fragmentation has significant clinical implications for developing targeted interventions to block aneurysm progression, which would benefit not only individuals with Marfan syndrome but also other patients with aneurysms. Moreover, this review highlights an overlooked connection between inhibiting aneurysm and the restoration of elastic fibers in the vessel wall with various aneurysm inhibitors, including drugs and chemicals. Investigating the underlying molecular mechanisms could uncover innovative therapeutic strategies to inhibit elastin fragmentation and prevent the progression of aneurysms., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest., (Copyright © 2023 Elsevier Inc. All rights reserved.)

This study aimed to determine whether the abnormal deep layer of dartos fascia plays an important role in buried penis. Forty-nine patients with buried penis were treated with anatomical resection of the deep layer of dartos fascia under a microscope. Penile length was measured before and after completely resecting the deep layer to investigate the role of this layer in penile retraction. The superficial and deep layers of dartos fascia were collected from 49 patients with buried penis, the normal superficial layers were collected from 25 children/adults who underwent circumcision for nonmedical reasons, and the normal deep layers were collected from 20 adult cadavers. The penile fascia samples were stained with hematoxylin-eosin, Masson's trichrome, Sirius red, and Verhoeff's Van Gieson, and subjected to immunohistochemical examination and scanning electron microscopy. The penile shaft (mean ± standard deviation) was found to be significantly elongated after resecting the deep layer compared with that before resection (6.8 ± 1.9 cm vs 6.0 ± 1.6 cm, P < 0.001). An abnormal deep layer of dartos fascia characterized by disordered and fragmented elastic fibers was observed in 87.8% (43/49) of buried penis samples, whereas no abnormal deep layer was observed in normal penises from cadavers (0/20, P < 0.001). Thus, the abnormal deep layer of dartos fascia plays an important role in the buried penis. Its resection is helpful for avoiding recurrence., (Copyright © 2023 Copyright: © The Author(s)(2023).)

This paper describes a methodology to differentiate morphea from lichen sclerosus based on examination with multiphoton microscopy (MPM) composed of two-photon excited fluorescence (TPEF) and second harmonic generation (SHG). Subcellular-resolution images were acquired by MPM from unstained lesion tissues then process spectral analysis to quantify the TPEF and SHG signals. Moreover, U-Net was employed to segment elastic fiber in TPEF images to combine with collagen fiber in SHG images for precise fiber quantification. Predictions of segmentation showed excellent performance on several evaluation indicators. The mIoU, mPA, and F1 score reach 0.8516, 0.9281, and 0.941. The quantitative analysis demonstrated the increase of collagen fibers in morphea compared to that in lichen sclerosus cases. Meanwhile, the great diminution of elastic fiber in the dermis of lichen sclerosus was depicted based on MPM imaging. Thus, MPM was comparable to the histopathological examination and our experimental results accurately distinguish between morphea and lichen sclerosus., (© 2023 Wiley-VCH GmbH.)

Linear focal elastosis (LFE) is an uncommon, benign, acquired elastotic condition with uncertain pathogenesis. It is characterized clinically by asymptomatic, multiple, yellowish, elevated, irregularly indurated, striae-like lines or bands distributed horizontally across the lower and middle part of the posterior trunk. The histopathological hallmark of LFE is a focal increase of elastic fibres in the dermis. The differential diagnosis is varied, and striae distensae is the closest mimic of LFE. Response of LFE to treatment is often poor. The focus of this article is to provide insights into this condition for dermatologists., Competing Interests: Conflict of interest: The authors declare that they have no conflict of interest., (© The Author(s) 2022. Published by Oxford University Press on behalf of British Association of Dermatologists. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Abdominal aortic aneurysm (AAA) is a fatal vascular disease. Vascular smooth muscle cells (VSMCs) play a crucial role in the pathogenesis of AAA. Increasing evidence has shown that Yes-associated protein (YAP) is involved in diverse vascular diseases. However, the role of YAP in AAA remains unclear. The current study aimed to determine the role of YAP in AAA formation and the underlying mechanism. We found that YAP expression in VSMCs was markedly decreased in human and experimental AAA samples. Furthermore, VSMC-specific YAP overexpression prevented several pathogenic factor-induced AAA. Mechanistically, YAP overexpression in VSMCs promoted latent transforming growth factor-β binding protein 4 (LTBP4) expression, an important factor in elastic fiber assembly. Finally, silencing of LTBP4 in VSMCs abolished the protective role of YAP in AAA formation in vivo. Our results suggest that YAP promotes LTBP4-mediated elastic fibril assembly in VSMCs, which mitigates elastin degradation and AAA formation., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Abstract: Elastic fibers are present as a thin line around the normal secretory coil of eccrine and apocrine glands, although they are virtually imperceptible with hematoxylin-eosin staining. Skin aging is a consequence of intrinsic and extrinsic factors, and glycation and ultraviolet irradiation are involved in this process favoring elastosis. We report an unusual and prominent perieccrine elastosis on the left temple in the vicinity of a basal cell carcinoma in a 78-year old man with type 2 diabetes, dyslipidemia, and hypertension. Very thick multilamellar and tortuous elastic fibers surrounded the eccrine coils. This increased amount of elastic fibers was confirmed by orcein staining as well as amyloid-P and lysozyme immunostaining. Perieccrine coil elastosis is a very unusual phenomenon that to the best of our knowledge has not been reported. Similar to dermal actinic elastosis, the presence of perieccrine coil elastosis in a skin cancer microenvironment might hypothetically promote tumor growth because of the release of elastin-derived peptides., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Objective: To raise the awareness of idiopathic pleuroparenehymal fibroelastosis (iPPFE) through investigating the clinical, radiographic and pathological features. Methods: Five cases of iPPFE proved by pathology. The clinical data were studied respectively, and the relevant literature was reviewed. Results: All the cases of iPPFE were manifested by cough and dyspnea. The patients including 3 males and 2 females, aged from 30 to 70 years Chest CT scan showed pleural thickening, subpleural consolidation in both upper lungs complicated with tractive bronchiectasis.Computed tomography-guided percutaneous lung biopsy or surgical lung were performed and the same pathological showed pleura and subpleural dense elastic and collagen fibers. The elastic fibers stain was also positive,which was consistent with PPFE. One patient received low-dose corticosteroid, two received pirfenidone therapy, the others received no treatment. Three patients were stable during the follow-up. Conclusions: iPPFE has characteristic pathological features. However, the number of clinically reported cases is low due to missed diagnosis or misdiagnosed. Improving the understanding of features of iPPFE is helpful for the dianosis, therapy, and prognosis of this disease.

Elastolytic giant cell granuloma, an idiopathic granulomatous dermatosis, is characterized by annular plaques on sun-exposed areas, and has been termed actinic granuloma or annular elastolytic giant cell granuloma. Many atypical clinical manifestations and lesions involving sun-protected areas have been reported. The aims of this retrospective study of 105 patients were to summarize the clinical and histological features of patients with this condition; to provide evidence for the viewpoint that elastolytic giant cell granuloma is a better term to include all clinical morphological types presenting with elastolysis, elastophagocytosis, and an infiltrate of multinucleated giant cells histologically; and to establish a new clinical classification. The varying clinical manifestations were further categorized into annular, papular, giant, mixed and generalized forms. The pathological manifestations were classified into giant cell, necrobiotic, histiocytic, sarcoidal and mixed patterns. Diabetes mellitus or impaired glucose tolerance were the most commonly identified comorbidities. Oral low-dose corticosteroid may be an effective treatment.

Many extensible tissues such as skin, lungs, and blood vessels require elasticity to function properly. The recoil of elastic energy stored during a stretching phase is provided by elastic fibers, which are mostly composed of elastin and fibrillin-rich microfibrils. In arteries, the lack of elastic fibers leads to a weakening of the vessel wall with an increased risk to develop cardiovascular defects such as stenosis, aneurysms, and dissections. The development of new therapeutic molecules involves preliminary tests in animal models that recapitulate the disease and whose response to drugs should be as close as possible to that of humans. Due to its superior in vivo imaging possibilities and the broad tool kit for forward and reverse genetics, the zebrafish has become an important model organism to study human pathologies. Moreover, it is particularly adapted to large scale studies, making it an attractive model in particular for the first steps of investigations. In this review, we discuss the relevance of the zebrafish model for the study of elastic fiber-related vascular pathologies. We evidence zebrafish as a compelling alternative to conventional mouse models.

Background: We aimed to investigate the formation and self-healing process of rabbit abdominal aortic aneurysm (AAA) by focus on the degeneration and regeneration of smooth muscle cells (SMCs) in elastase-induced AAA model and enlarging AAA model in rabbits., Methods: Sixty rabbits were equally divided into 2 aneurysm groups (Group A and Group B). Rabbits received a 10-min incubation of elastase in Group A (10 units/µL) and Group B (1 unit/µL). Rabbits underwent aortic stenosis above the incubated segment in Group B. Aortic diameter was measured and rabbits were sacrificed for histopathological and immunohistochemical studies., Results: The incubated aorta dilated immediately and ran up to maxima by day 21 in Group A. All aneurysms formed by day 21 and enlarged progressively in Group B. SMCs content, elastin content and intima-media thickness decreased significantly by day 0 in Group A. SMCs and elastic fibers were destroyed gradually in Group B, however, SMCs content was significantly lower than Group A by day 70. Intimal thickness increased significantly by day 70 in the Aneurysm groups. MMP2 maintained moderate expression in Group A, which decreased significantly by day 3 in Group B. MMP9 and RAM11 expressions were higher by day 1, but decreased significantly by day 3 in Group B., Conclusions: Irreversible degeneration of SMCs is critical to a rapid formation of elastase-induced rabbit AAA model, and SMCs excessive regeneration accounts for the selfhealing process. SMCs degradation and regeneration remain relatively stable in an enlarging AAA model. SMCs should be the key target for studying the mechanism of AAA and intervention therapy., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Introduction: Microvascular remodelling is a symptom of cardiovascular disease. Despite the mechanical environment being recognized as a major contributor to the remodelling process, it is currently only understood in a rudimentary way., Objective: A morphological and mechanical evaluation of the resistance vasculature in health and diabetes mellitus., Methods: The cells and extracellular matrix of human subcutaneous resistance arteries from abdominal fat biopsies were imaged using two-photon fluorescence and second harmonic generation at varying transmural pressure. The results informed a two-layer mechanical model., Results: Diabetic resistance arteries reduced in wall area as pressure was increased. This was attributed to the presence of thick, straight collagen fibre bundles that braced the outer wall. The abnormal mechanical environment caused the internal elastic lamina and endothelial and vascular smooth muscle cell arrangements to twist., Conclusions: Our results suggest diabetic microvascular remodelling is likely to be stress-driven, comprising at least 2 stages: (1) Laying down of adventitial bracing fibres that limit outward distension, and (2) Deposition of additional collagen in the media, likely due to the significantly altered mechanical environment. This work represents a step towards elucidating the local stress environment of cells, which is crucial to build accurate models of mechanotransduction in disease., (© 2021 The Author(s) Published by S. Karger AG, Basel.)

The association between penile lichen sclerosus and striking accumulation of elastic fibers in deep dermis has been described in rare reports, mostly in vulvar lesions. We describe one case of severe balanopreputial adhesions related to lichen sclerosus and this form of elastosis, with no concomitant neoplasia. Aggregates of elastic fibers were seen in deep dermis and in blood vessels. The lesion mirrors nevus elasticus and nevus elasticus vascularis - a well described cutaneous lesion with no known association with lichen sclerosus., (© 2021 S. Karger AG, Basel.)

Abstract: Amyloid elastosis is an exceedingly rare form of amyloidosis characterized by amyloid material deposited on dermal elastic fibers. Most reported cases have been associated with systemic amyloid light-chain amyloidosis. A single previously reported case of amyloid elastosis showed evidence that the amyloid material was derived from light-chain proteins and was associated with a monoclonal plasma cell infiltrate but failed to demonstrate systemic involvement. As a result, the case was felt to represent localized cutaneous amyloid elastosis. We present a case of localized cutaneous amyloid elastosis that is not associated with a definitive monotypic plasma cell population or with systemic amyloidosis. We also review the clinical and histopathologic features of reported cases of amyloid elastosis and discuss possible etiologic considerations. Because amyloid elastosis can be either localized to the skin or associated with systemic involvement, additional workup to exclude an underlying plasma cell dyscrasia or hematologic malignancy is warranted., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Evaluate the effect of 12 wks of concurrent training (CT) in the extracellular matrix (ECM) of subcutaneous adipose tissue (SAT) in people living with HIV/AIDS (PLWHA). In the non-randomized clinical trial, 19 participants, 11 healthy (HIV-) and 18 PLWHA under the use of highly active antiretroviral therapy (HAART) for at least 1 year (HIV+). All participants engaged in a moderate-intensity CT program for 12 weeks, 3 times a week. Before and after CT, aerobic and strength performance were assessed, as well as anthropometric and biochemical blood profiles. In addition, SAT biopsies were performed for histologic and morphometric analyses. Statistical analysis was carried out with R Studio, using descriptive and inferential analysis, ANOVA test, and mixed-effect model ( P < 0.05). HIV+ showed higher levels of very-low-density lipoproteins and triglycerides and lower levels of high-density lipoproteins at baseline than HIV- ( P < 0.05). All groups showed improved aerobic and strength performances ( P < 0.05). Both groups showed reduced adipocyte sizes after CT ( P < 0.05). Lastly, HIV+ presented smaller adipocytes and higher elastic fiber deposition at baseline and decreased after training only in HIV+, similar to the HIV group. Thus, CT in PLWHA promoted a decrease in the size heterogeneity of adipocytes and elastic fiber deposition, remodeling the ECM, and improving the SAT fibrosis profile. Brazilian Clinical Trials Registry (ensaiosclinicos.gov.br - UTN: U1111-1214-3022). Novelty: Adipose tissue fibrosis is improved by training in people living with HIV. Concurrent training remodels adipose tissue extracellular matrix.

Abstract: Papillary dermal elastolysis has been described in the setting of experimental combination nivolumab and cabiralizumab immunotherapy. We report a third patient with distinctive, generalized atrophic macules that developed after a morbilliform eruption during a clinical trial for treatment of metastatic pancreatic adenocarcinoma. Histopathological findings demonstrated diminished elastic fibers in the papillary dermis, associated with a histiocyte-rich infiltrate and increased dermal mucin, features that should clue the dermatopathologist to this condition., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Diagnosis of fibrous tumors can be challenging and expensive due to the use of special stains., Objective: Determine the usefulness of fluorescence microscopy in the evaluation of elastic tissue patterns on hematoxylin-eosin-stained slides., Methods: In total, 228 slides representing different fibrous tumors were evaluated for their elastic tissue patterns by fluorescence microscopy, and sensitivity and specificity were determined for relevant comparisons., Results: Fluorescence microscopy was found to be useful, especially for distinguishing dermatofibroma from dermatofibrosarcoma protuberans and dermatomyofibroma from other fibrous tumors., Limitations: In some cases, excessive background staining made patterns difficult to interpret., Conclusion: Evaluation of elastic tissue patterns by fluorescence microscopy in fibrous tumors is a cheap and efficient means to further delineate these often challenging tumors., (Copyright © 2018 American Academy of Dermatology, Inc. All rights reserved.)

Pelvic organ prolapse (POP) is common among older women who have delivered children vaginally. While the pathophysiology is not fully delineated, POP can occur in part from insufficient repair of disrupted elastic matrix fibers. Quantification of structural changes to elastic fibers has not been described previously for POP. The goal of this paper is to present a validated technique for morphometric analysis of elastic fibers in vaginal tissue cultures from lysyl oxidase like-1 knock out (LOXL1 KO) mice with POP. The effect of LOXL1 KO, effect of POP, effect of culture, and effect of elastogenic treatment on the changes in elastin fiber characteristics were tested using vaginal tissues from wild type multiparous (WT), LOXL1 KO multiparous prolapsed (POP) and LOXL1 KO multiparous non-prolapsed (NP) mice. Our results show significantly higher mean aspect ratio, maximum diameter and perimeter length in POP compared to NP after 3 weeks of tissue culture. Further, treatment of POP tissues in culture with growth factors with previously documented elastogenic effects caused a significant increase in the mean area and perimeter length of elastic fibers. This technique thus appears to be useful in quantifying structural changes and can be used to assess the pathophysiology of POP and the effect of elastogenic treatments with potential for POP., (© 2021. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.)

The histological distinction between acute and chronic liver injury is a challenging aspect of liver histopathology. It is traditionally based on the interpretation of morphological changes to the extracellular matrix (ECM) at sites of hepatocyte loss using histochemical stains. Our aim was to investigate whether immunohistochemistry and multiplexing for collagen type (I & III) and elastic fibres and a modified Victoria blue method could be helpful. We studied 43 livers removed at transplantation for acute liver failure (ALF, 20 cases) or cirrhosis (23) plus 8 normal controls. In ALF the periportal ECM was normal in 2 cases, contained mainly collagen I associated with a ductular reaction in 6 cases, and delicate elastic strands in 11 cases. Periportal deposition of mainly collagen I and mature elastic fibres was observed in cirrhosis. In ALF the perisinusoidal ECM was intact in 4 cases, collapsed or condensed but of normal composition (predominantly collagen III) in 2 cases, and collapsed and condensed containing mostly collagen I in 17 cases (7 including delicate immature elastic strands). In contrast, bridging fibrous septa of cirrhosis contained abundant collagen 1 and bundles of mature elastin. We propose the use of a scale and the use of immunohistochemistry and multiplexing in additional to histochemical stains to characterise the ECM changes in acute and chronic liver injury., (© 2021. The Author(s).)

Protein kinase C-delta (PKCδ) has a caspase-3 recognition sequence in its structure, suggesting its involvement in apoptosis. In addition, PKCδ was recently reported to function as an anti-cancer factor. The generation of a PKCδ knockout mouse model indicated that PKCδ plays a role in B cell homeostasis. However, the Pkcrd gene, which is regulated through complex transcription, produces multiple proteins via alternative splicing. Since gene mutations can result in the loss of function of molecular species required for each tissue, in the present study, conditional PKCδ knockout mice lacking PKCδI, II, IV, V, VI, and VII were generated to enable tissue-specific deletion of PKCδ using a suitable Cre mouse. We generated PKCδ-null mice that lacked whole-body expression of PKCδ. PKCδ+/- parental mice gave birth to only 3.4% PKCδ-/- offsprings that deviated significantly from the expected Mendelian ratio (χ2(2) = 101.7, P < 0.001). Examination of mice on embryonic day 11.5 (E11.5) showed the proportion of PKCδ-/- mice implanted in the uterus in accordance with Mendelian rules; however, approximately 70% of the fetuses did not survive at E11.5. PKCδ-/- mice that survived until adulthood showed enlarged spleens, with some having cardiac and pulmonary abnormalities. Our findings suggest that the lack of PKCδ may have harmful effects on fetal development, and heart and lung functions after birth. Furthermore, our study provides a reference for future studies on PKCδ deficient mice that would elucidate the effects of the multiple protein variants in mice and decipher the roles of PKCδ in various diseases., Competing Interests: The authors have declared that no competing interests exist.

Background: The aim of this study was to evaluate the accuracy of three combination staining approaches, each composed of pancytokeratin immunostaining with an elastic-fiber staining method of choice, in diagnosing visceral pleural invasion (VPI) in lung adenocarcinoma patients., Methods: Tissue samples were resected from 23 lung adenocarcinoma patients, for whom neither hematoxylin and eosin nor Gomori's aldehyde-fuchsin (GAF) staining accurately detected the presence of VPI. Three slices were prepared from each sample and examined by immunohistochemical staining of cytokeratin AE1/AE3 and one of the following methods for elastic-fiber staining, including Victoria blue (VB), GAF, or Weigert's resorcin-fuchsin (WRF). The staining scores and slider view time were compared among the three staining protocols with tumor extension beyond the elastic layer of the visceral pleura as the diagnostic criterion for VPI., Results: Conclusive diagnoses were achieved for all 23 tissue samples stained with VB, 18 with GAF, and 17 with WRF. VB staining was the fastest of the three methods, and produced significantly brighter, clearer color, and better contrast between the elastic fibers and tumor cells, thus facilitating slide review., Conclusions: The combination of VB elastic fiber and cytokeratin AE1/AE3 staining is a user-friendly, fast, and highly effective method that produces bright stains, favorable color contrast against the background, and high tumor localization accuracy. Hence, this method can improve the accuracy of VPI diagnosis and the corresponding staging of lung adenocarcinoma. We recommend the combined use of VB and pancytokeratin immunostaining when VPI is suspected.

Abstract: In vulvar biopsies, we have observed histopathologic abnormalities of elastic fibers identical to solar elastosis, with thick, curled, and irregular pale grey fibers in the dermis. In severe cases, changes resemble nodular solar elastosis. We retrospectively evaluated 238 vulvar biopsies with the goal of defining and characterizing changes of vulvar elastosis. Of 238 vulvar biopsies reviewed, 107 (45%) exhibited vulvar elastosis. Patients with vulvar elastosis were older (mean = 65 years old) compared to those without (mean = 44 years old). Sixty-six (62%) were graded as mild, 27 (25%) moderate, and 14 (13%) severe. Vulvar elastosis was significantly more common in women ≥45 years old (P-value < 0.001). There was moderate correlation between age and severity (correlation coefficient = 0.55, P-value < 0.001). Vulvar elastosis was observed in a variety of inflammatory and non-inflammatory pathologies. In 5 cases, the sole pathology was vulvar elastosis presenting clinically as either a pruritic or painful white to white-yellow papule or plaque, or vulvar pain or burning without a clinical lesion. Vulvar elastosis is a novel diagnostic entity occurring in a sun-protected site and its pathogenesis may be a degenerative phenomenon possibly related to advancing age and/or hormonal changes., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Competing Interests: The authors declare no conflicts of interest.

Elastic fibers are the main components of the extracellular matrix of the large arterial wall. Elastic fiber remodeling is an intricate process of synthesis and degradation of the core elastin protein and microfibrils accompanied by the assembly and disassembly of accessory proteins. Age-related morphological, structural, and functional proinflammatory remodeling within the elastic fiber has a profound effect upon the integrity, elasticity, calcification, amyloidosis, and stiffness of the large arterial wall. An age-associated increase in arterial stiffness is a major risk factor for the pathogenesis of diseases of the large arteries such as hypertensive and atherosclerotic vasculopathy. This mini review is an update on the key molecular, cellular, functional, and structural mechanisms of elastic fiber proinflammatory remodeling in large arteries with aging. Targeting structural and functional integrity of the elastic fiber may be an effective approach to impede proinflammatory arterial remodeling with advancing age., (Published by Elsevier B.V.)

Study Design: Experimental animal study., Objective: The aim of this study was to clarify chronological effects of mechanical stress on ligamentum flavum (LF) using a long-term fusion rabbit model., Summary of Background Data: LF hypertrophy is a major pathology of lumbar spinal stenosis (LSS), but its mechanism remains unclear. We previously demonstrated mechanical-stress-induced LF hypertrophy with a rabbit model. However, we only investigated LFs at a single time point in the short-term; the effects of long-term mechanical stress have not been elucidated., Methods: Eighteen-week-old male New Zealand White rabbits were randomly divided into two groups: the mechanical stress group underwent L2-3 and L4-5 posterolateral fusion and resection of the L3-4 supraspinal muscle, whereas the control group underwent only surgical exposure. Rabbits were sacrificed 16 and 52 weeks after the procedure. Axial specimens of LFs at L3-4 were evaluated histologically. Immunohistochemistry for alpha-smooth muscle actin (α-SMA) was performed to assess the numbers of vessels and myofibroblasts., Results: In the mechanical stress group, LFs at the L3-4 level exhibited hypertrophy with elastic fiber disruption and cartilage matrix production at 16 and 52 weeks. A trend test indicated that mechanical stress induced LF hypertrophy, elastic fiber disruption, and cartilage matrix production in a time-dependent manner, with the lowest levels before treatment and the highest at 52 weeks. Immunostaining for α-SMA showed similar numbers of vessels in both groups, whereas the percentage of myofibroblasts was significantly larger at 16 and 52 weeks in the mechanical stress group than in the control group., Conclusion: We demonstrated that long-term mechanical stress caused LF hypertrophy with progressive elastic fiber disruption and cartilage matrix production accompanied by enhanced myofibroblasts. In addition, the reported rabbit model could be extended to elucidate the mechanism of LF hypertrophy and to develop new therapeutic strategies for LSS by preventing LF hypertrophy.Level of Evidence: SSSSS., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Elastic fibers are essential components of the arterial extracellular matrix. They consist of the protein elastin and an array of microfibrils that support the protein and connect it to the surrounding matrix. The elastin gene encodes tropoelastin, a protein that requires extensive cross-linking to become elastin. Tropoelastin is expressed throughout human life, but its expression levels decrease with age, suggesting that the potential to synthesize elastin persists during lifetime although declines with aging. The initial abnormality documented in human atherosclerosis is fragmentation and loss of the elastic network in the medial layer of the arterial wall, suggesting an imbalance between elastic fiber injury and restoration. Damaged elastic structures are not adequately repaired by synthesis of new elastic elements. Progressive collagen accumulation follows medial elastic fiber disruption and fibrous plaques are formed, but advanced atherosclerosis lesions do not develop in the absence of prior elastic injury. Aging is associated with arterial extracellular matrix anomalies that evoke those present in early atherosclerosis. The reduction of elastic fibers with subsequent collagen accumulation leads to arterial stiffening and intima-media thickening, which are independent predictors of incident hypertension in prospective community-based studies. Arterial stiffening precedes the development of hypertension. The fundamental role of the vascular elastic network to arterial structure and function is emphasized by congenital disorders caused by mutations that disrupt normal elastic fiber production. Molecular changes in the genes coding tropoelastin, lysyl oxidase (tropoelastin cross-linking), and elastin-associated microfibrils, including fibrillin-1, fibulin-4, and fibulin-5 produce severe vascular injury due to absence of functional elastin.

Significance: Cardiovascular disorders are the most important cause of morbidity and mortality in the Western world. Monogenic developmental disorders of the heart and vessels are highly valuable to study the physiological and pathological processes in cardiovascular system homeostasis. The arterial tortuosity syndrome (ATS) is a rare, autosomal recessive connective tissue disorder showing lengthening, tortuosity, and stenosis of the large arteries, with a propensity for aneurysm formation. In histopathology, it associates with fragmentation and disorganization of elastic fibers in several tissues, including the arterial wall. ATS is caused by pathogenic variants in SLC2A10 encoding the facilitative glucose transporter (GLUT)10. Critical Issues: Although several hypotheses have been forwarded, the molecular mechanisms linking disrupted GLUT10 activity with arterial malformations are largely unknown. Recent Advances: The vascular and systemic manifestations and natural history of ATS patients have been largely delineated. GLUT10 was identified as an intracellular transporter of dehydroascorbic acid, which contributes to collagen and elastin cross-linking in the endoplasmic reticulum, redox homeostasis in the mitochondria, and global and gene-specific methylation/hydroxymethylation affecting epigenetic regulation in the nucleus. We revise here the current knowledge on ATS and the role of GLUT10 within the compartmentalization of ascorbate in physiological and diseased states. Future Directions: Centralization of clinical, treatment, and outcome data will enable better management for ATS patients. Establishment of representative animal disease models could facilitate the study of pathomechanisms underlying ATS. This might be relevant for other forms of vascular dysplasia, such as isolated aneurysm formation, hypertensive vasculopathy, and neovascularization. Antioxid. Redox Signal . 34, 875-889.

Hypertrophy of the ligamentum flavum (LF) is a major cause of lumbar spinal stenosis (LSS), and the pathology involves disruption of elastic fibers, fibrosis with increased cellularity and collagens, and/or calcification. Previous studies have implicated the increased expression of the proteoglycan family in hypertrophied LF. Furthermore, the gene expression profile in a rabbit experimental model of LF hypertrophy revealed that biglycan (BGN) is upregulated in hypertrophied LF by mechanical stress. However, the expression and function of BGN in human LF has not been well elucidated. To investigate the involvement of BGN in the pathomechanism of human ligamentum hypertrophy, first we confirmed increased expression of BGN by immunohistochemistry in the extracellular matrix of hypertrophied LF of LSS patients compared to LF without hypertrophy. Experiments using primary cell cultures revealed that BGN promoted cell proliferation. Furthermore, BGN induces changes in cell morphology and promotes myofibroblastic differentiation and cell migration. These effects are observed for both cells from hypertrophied and non-hypertrophied LF. The present study revealed hyper-expression of BGN in hypertrophied LF and function of increased proteoglycan in LF cells. BGN may play a crucial role in the pathophysiology of LF hypertrophy through cell proliferation, myofibroblastic differentiation, and cell migration.