Lizandre Keren Ramos da Silveira

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by progressive fibrosis and immune dysregulation, with lung involvement being a major cause of morbidity and mortality. Type V collagen (COLV), a cryptic self-antigen, has been implicated in the pathogenesis of fibrosis in both SSc and lung allograft dysfunction. To characterize the early histological, molecular, and immunological events associated with lung remodeling following immunization with COLV in a murine model (IMU-COLV), and to establish a temporal framework for fibrosis progression. Using a time-course design, lung tissue from IMU-COLV mice was analyzed at multiple intervals post-immunization. Histopathological assessment, immunohistochemistry, and gene expression analysis were performed to evaluate inflammation, endothelial activation, extracellular matrix remodeling, and collagen composition. We observed a progressive and spatially organized pattern of lung remodeling, beginning with peribronchovascular immune infiltration and culminating in airway-centered fibrosis. These changes were accompanied by dynamic endothelial activation, increased expression of profibrotic markers, and alterations in collagen architecture particularly involving COLV. The remodeling pattern closely mirrors histological features observed in early SSc-associated interstitial lung disease and other fibrotic conditions, such as idiopathic pulmonary fibrosis and chronic lung allograft dysfunsion. The IMU-COLV model recapitulates key early features of SSc-related lung fibrosis, highlighting COLV’s potential role as a driver of immune-mediated tissue remodeling. These findings provide a valuable platform for investigating the mechanisms underlying fibrogenesis and for testing targeted interventions in the early phases of pulmonary fibrosis.

Type V collagen (Col V) has been implicated in the development of fibrosis in systemic sclerosis (SSc). In this study, we aimed to investigate the role of Col V in fibrillar matrix remodeling and fibroblast differentiation using an experimental SSc model. Skin fibroblasts from healthy C57BL/6 mice were stimulated in vitro with 25 and 50 μg of Col V to assess fibrillar collagen expression. An SSc model was induced in C57BL/6 mice by immunization with Col V emulsified in Freund’s adjuvant (IMU-COLV), with animals assigned to 15-, 30-, and 45-day IMU-COLV or control groups. In vitro, Col V stimulation caused a dose-dependent increase in myofibroblast markers (α-SMA, Col I, and Col V) and altered fibrillar collagen structure. Immunofluorescence revealed thickened Col V and Col III fibrils around myofibroblasts and the formation of a spiderweb-like matrix. In vivo, fibrosis progressed over time, characterized by increased myofibroblast accumulation and elevated Col I and Col V levels. Histological analysis revealed fibrillar disorganization and aggregated collagen fibers resembling early-stage human SSc. These findings suggest that enhanced Col V synthesis disrupts the fibrillar matrix, promoting myofibroblast differentiation and collagen deposition, which are hallmarks of SSc-related fibrosis.

Dietary sodium restriction increases plasma triglycerides (TG) and total cholesterol (TC) concentrations as well as causing insulin resistance and stimulation of the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system. Stimulation of the angiotensin II type-1 receptor (AT1) is associated with insulin resistance, inflammation, and the inhibition of adipogenesis. The current study investigated whether aerobic exercise training (AET) mitigates or inhibits the adverse effects of dietary sodium restriction on adiposity, inflammation, and insulin sensitivity in periepididymal adipose tissue. LDL receptor knockout mice were fed either a normal-sodium (NS; 1.27% NaCl) or a low-sodium (LS; 0.15% NaCl) diet and were either subjected to AET for 90 days or kept sedentary. Body mass, blood pressure (BP), hematocrit, plasma TC, TG, glucose and 24-hour urinary sodium (U_Na) concentrations, insulin sensitivity, lipoprotein profile, histopathological analyses, and gene and protein expression were determined. The results were evaluated using two-way ANOVA. Differences were not observed in BP, hematocrit, diet consumption, and TC. The LS diet was found to enhance body mass, insulin resistance, plasma glucose, TG, LDL-C, and VLDL-TG and reduce U_Na, HDL-C, and HDL-TG, showing a pro-atherogenic lipid profile. In periepididymal adipose tissue, the LS diet increased tissue mass, TG, TC, AT1 receptor, pro-inflammatory macro-phages contents, and the area of adipocytes; contrarily, the LS diet decreased anti-inflammatory macrophages, protein contents and the transcription of genes related to insulin sensitivity. The AET prevented insulin resistance, but did not protect against dyslipidemia, adipose tissue pro-inflammatory profile, increased tissue mass, AT1 receptor expression, TG, and TC induced by the LS diet.