| COL3A1 encodes the pro‑α1(III) chain of type III collagen, a fibrillar collagen that assembles as a homotrimer and integrates into branched fibrils within the extracellular matrix of extensible soft tissues such as skin, lung, intestine, uterus, and the vascular wall, where it frequently co‑localizes with type I collagen and contributes to tissue elasticity and tensile strength. The α1(III) chain contains the characteristic long triple‑helical domain based on uninterrupted Gly‑X‑Y repeats flanked by non‑helical N‑ and C‑terminal propeptides; intracellular assembly of three α1(III) chains into procollagen triple helices is followed by extracellular N‑ and C‑propeptide cleavage and incorporation of mature type III collagen into heterotypic fibrils that interact with proteoglycans, other collagens, and cell‑surface receptors. Type III collagen functions as a structural scaffold and as a regulator of collagen I fibrillogenesis, and genetic ablation or functional deficiency alters the diameter and organization of collagen I–containing fibrils, compromises the architecture of the adventitia and myocardium, and disrupts normal cardiovascular development, highlighting a mechanistic role for COL3A1 in coordinating fibril assembly and biomechanical behavior of arteries and heart tissue. In the arterial wall, type III collagen localizes predominantly to the adventitia and media, where it participates in load‑bearing networks that accommodate cyclic stretch and maintain vessel stability; altered abundance or quality of collagen III changes vessel compliance and predisposes to structural failure under hemodynamic stress. Heterozygous pathogenic variants in COL3A1 that substitute glycine residues within the triple‑helical region or truncate the chain underlie vascular Ehlers–Danlos syndrome, a condition characterized by fragile arteries, spontaneous arterial dissection or rupture, and vulnerability of hollow organs such as bowel and uterus, reflecting the dependence of these tissues on intact type III collagen networks for mechanical integrity. Patient‑derived extracellular matrix generated from fibroblasts carrying COL3A1 mutations shows altered collagen composition, increased glycosaminoglycan content, and modified viscoelastic properties, including slower stress relaxation, which affect endothelial cell migration on the matrix and demonstrate a direct link between COL3A1 status, ECM mechanical behavior, and vascular cell interactions. Across fibrotic diseases, elevated COL3A1 expression and increased type III collagen deposition accompany matrix remodeling in organs such as the lung, liver, kidney, and skin, contributing to thickened interstitial scaffolds and altered tissue stiffness that influence resident cell proliferation, migration, and differentiation. In cancer, COL3A1 expression in tumor and stromal compartments associates with extracellular matrix remodeling, angiogenic signaling, and altered tumor cell behavior, and COL3A1‑positive endothelial subpopulations in lung adenocarcinoma display distinct metabolic and immune signaling features that shape communication with malignant cells through VEGF and PI3K–AKT pathway activity. Recombinant human COL3A1 applied to dermal fibroblasts promotes cell proliferation, collagen biosynthesis, and wound closure and supports ECM deposition, indicating a functional role in skin repair and highlighting the protein as a candidate biomaterial for enhancing dermal regeneration and modulating skin aging–related matrix decline. |
