Assembly of collagen fibers into contiguous dense and loose regions of subcutaneous fascia

This study aimed to investigate the collagen fiber structure of the subcutaneous fascia, a connective tissue layer between the skin and epimysium. Fascia samples with varying extensibility were examined using biochemical and microscopic methods. Loose fascia, the more extensible type, displayed sparsely distributed collagen fibers, while dense fascia showed tightly packed collagen fiber bundles. Elastase treatment, after urea pretreatment, caused the loosening of collagen fiber bundles and increased collagen fiber generation as the treatment time increased. This suggests that elastic fibers contribute to collagen fiber bundle formation. Additionally, elastase treatment stretched the fascia, indicating the presence of twodimensional tensile stress generated by elastic fibers. Either enzymes capable of cleaving elastic fibers may be activated or the stretching of elastic fibers accompanying tissue deformation may increase the enzyme sensitivity to elastic fibers, leading to the formation of localized collagen fibers in vivo. Tissue staining confirmed that loose and dense fascia corresponded to areas with sparse and dense collagen fibers, respectively. Some dense collagen fibers appeared to migrate and disperse into loose areas. These findings provide insights into the structural organization and functional significance of collagen fibers within the subcutaneous fascia. They particularly highlight the role of elastic fibers in maintaining tissue integrity and facilitating dynamic remodeling.