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We previously described restrictive allograft syndrome as a form of chronic lung allograft dysfunction, demonstrating restrictive pulmonary function decline. However, the histopathological correlates of restrictive allograft syndrome have yet to be satisfactorily described. We hypothesized that pulmonary pleuroparenchymal fibroelastosis, as has recently been described in bone marrow transplant recipients, may also be present in the lungs of patients with restrictive allograft syndrome. Retrospective review of 493 patients who underwent lung transplantation between 1 January 1996 and 30 June 2009, was conducted. Out of 47 patients with clinical features of restrictive allograft syndrome, 16 had wedge biopsy, re-transplant lung explant, or autopsy lung specimens available for review. All lungs showed varying degrees of pleural fibrosis. Fifteen of 16 showed parenchymal fibroelastosis, characterized by hypocellular collagen deposition with preservation and thickening of the underlying alveolar septal elastic network. The fibroelastosis was predominantly subpleural in distribution, with some cases also showing centrilobular and paraseptal distribution. A sharp demarcation was often seen between areas of fibroelastosis and unaffected lung parenchyma, with fibroblastic foci often present at this interface. Concurrent features of obliterative bronchiolitis were present in 14 cases. Another common finding was the presence of diffuse alveolar damage (13 cases), usually in specimens obtained <1 year after clinical onset of restrictive allograft syndrome. The single specimen in which fibroelastosis was not identified was obtained before the clinical onset of chronic lung allograft dysfunction, and showed features of diffuse alveolar damage. In conclusion, pleuroparenchymal fibroelastosis is a major histopathologic correlate of restrictive allograft syndrome, and was often found concurrently with diffuse alveolar damage. Our findings support a temporal sequence of diffuse alveolar damage followed by the development of pleuroparenchymal fibroelastosis in the histopathologic evolution of restrictive allograft syndrome.

We previously reported ocular phenotypes of 1-year-old 129S1/SvlmJ lysyl oxidase-like 1 null (Loxl1−/−) mice. Here we sought to characterize age-dependent changes in C57BL/6J Loxl1−/− mice in a longitudinal fashion. Retinal ganglion cell (RGC) function was assessed by electroretinography (ERG), and optic nerves were evaluated by histological analysis. Ocular biometric measurements were obtained by optical coherence tomography (OCT). We detected reduced RGC function, revealed by decreased amplitude and increased latency of ERG positive scotopic threshold responses (pSTRs) in Loxl1−/− mice compared to age-matched wt mice. In addition, there is significant inter-eye asymmetry of RGC function, as well as age-related RGC function loss observed only in Loxl1−/− mice. Histologically, we observed enlarged optic nerve areas in Loxl1−/− mice compared to wt mice. Significant ocular biometric differences between two groups were detected, most notably, age-related axial elongation of the globe, accompanied by deepening of anterior chamber depth (ACD). Though eyes elongate with age in both groups, this is more pronounced in Loxl1−/− mice, and the elongation of the globe correlated with decreased RGC function. The correlation of age-related reduction in RGC function with globe axial elongation may have implications for the association of axial myopia with glaucoma and aging in humans.

Aortic aneurysm and dissection are manifestations of Marfan syndrome (MFS), a disorder caused by mutations in the gene that encodes fibrillin-1. Selected manifestations of MFS reflect excessive signaling by the transforming growth factor-{szligbeta} (TGF-{szligbeta}) family of cytokines. We show that aortic aneurysm in a mouse model of MFS is associated with increased TGF-{szligbeta} signaling and can be prevented by TGF-{szligbeta} antagonists such as TGF-{szligbeta}-neutralizing antibody or the angiotensin II type 1 receptor (AT1) blocker, losartan. AT1 antagonism also partially reversed noncardiovascular manifestations of MFS, including impaired alveolar septation. These data suggest that losartan, a drug already in clinical use for hypertension, merits investigation as a therapeutic strategy for patients with MFS and has the potential to prevent the major life-threatening manifestation of this disorder.

Large artery stiffness, as measured by pulse wave velocity, is correlated with high blood pressure and may be a causative factor in essential hypertension. The extracellular matrix components, specifically the mix of elastin and collagen in the vessel wall, determine the passive mechanical properties of the large arteries. Elastin is organized into elastic fibers in the wall during arterial development in a complex process that requires spatial and temporal coordination of numerous proteins. The elastic fibers last the lifetime of the organism but are subject to proteolytic degradation and chemical alterations that change their mechanical properties. This review discusses how alterations in the amount, assembly, organization, or chemical properties of the elastic fibers affect arterial stiffness and blood pressure. Strategies for encouraging or reversing alterations to the elastic fibers are addressed. Methods for determining the efficacy of these strategies, by measuring elastin amounts and arterial stiffness, are summarized. Therapies that have a direct effect on arterial stiffness through alterations to the elastic fibers in the wall may be an effective treatment for essential hypertension.

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.

Pulmonary emphysema is a progressive and debilitating lung disease characterized by the destruction of alveolar walls and enlargement of airspaces, resulting in impaired gas exchange and reduced lung function. Central to this pathology is the degradation of the extracellular matrix (ECM), particularly the elastic fiber network containing elastin protein responsible for storing and releasing the energy that expels air from the lung. Both intrinsic and extrinsic mechanical stress play a pivotal role in ECM remodeling, influencing elastin degradation and the structural integrity of alveolar walls. This paper explores the interactions between mechanical forces and ECM components, emphasizing the role of increased elastin crosslinking in the pathogenesis and progression of emphysema. The molecular mechanisms responsible for this process are described in the context of emergent phenomena associated with alveolar wall distension and rupture, including the role of diagnostic biomarkers in the early detection of elastic fiber injury that may facilitate timely therapeutic interventions designed to preserve ECM integrity and improve patient outcomes.

Marfan syndrome is a connective tissue disorder caused by FBN1 mutations, leading to aortic wall fragility and increased susceptibility to aneurysm and dissection. This study investigated microstructural and molecular alterations in the thoracic aorta of Fbn1mgΔ lpn mice, with a focus on the tunica intima and media. Histological and ultrastructural analyses demonstrated elastic fiber fragmentation and reduced fibrillin-1 expression. In the intima, endothelial cells showed partial detachment and decreased levels of fibrillin-1, perlecan, collagen IV, and α5β1 integrins, suggesting compromised adhesion to the extracellular matrix. Serial block-face scanning electron microscopy revealed discontinuities in the internal elastic lamina. In the media, we observed reduced fibronectin, altered α5β1 integrin distribution, and increased α-smooth muscle actin, indicative of remodeling in elastin–contractile units. Second harmonic generation imaging revealed increased collagen deposition, and thickness in areas of elastic fiber disruption, along with reduced and disorganized type III collagen and increased type I collagen. Echocardiographic evaluation showed aortic root, and ascendant-aorta dilatation, altered blood flow, and diastolic dysfunction. Elastic fiber integrity correlated strongly with fibrillin-1 expression ( r  = 0.93, p  = 0.0003) and aortic blood flow ( r  = 0.77, p  = 0.0064). These results suggest that early alterations in matrix organization and endothelial–matrix interactions may contribute to aortic wall weakening in Fbn1mgΔ lpn mice.

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.

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.

Background and aimsDiagnosing 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 designCross-sectional study.MethodsFifty-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.ResultsDiagnostic 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).ConclusionIncreased diagnostic yield is noted with trichoscopy and VVG stain in PCA especially when routine histopathology is non-diagnostic.