Comparative integumentary fascial anatomy in mice, rats, and humans: homologies and implications for translational wound healing research.

In mice, native fascia and surrounding tissues have been shown to mobilize into wounds during healing, particularly during the proliferative phase. However, comparative descriptions of integumentary fascial anatomy across commonly used research species remain limited. This study aimed to characterize and compare the fascial layers of the integumentary system in mice, rats, and humans, identify structural homologies across species, and discuss the implications of these findings for wound healing research. Histological analysis of skin specimens from mice, rats, and humans was performed using microscopy to identify epidermal, dermal, adipose, fascial, and muscular tissue planes. Gross anatomical dissections of human pannus specimens were additionally used to identify subcutaneous fascial compartments. Tissue layers were systematically identified, described, and compared across species. Mice demonstrated the most complex fascial architecture, comprising multiple distinct sublayers within the stratum fibrosum. Rats displayed a simpler, more homogeneous stratum fibrosum with a comparatively greater tissue thickness between fascial planes and the overlying dermis. In humans, the subcutaneous space was involving the superficial (Camper's fascia), centered Scarpa's fascia, and Deep adipose layer were exposed for comparison. Cross-species homologies were identified within the integumentary and fascial layers. Integumentary fascia demonstrates both conservation and important species-specific structural divergence. The distinctive multi-layered fascial organization and shallow fascial depth in mice may facilitate unique wound-healing dynamics that are not fully replicated in rats or humans. These anatomical differences should be carefully considered and experimentally tested prior to extrapolating murine fascia-related wound-healing mechanisms onto rats and humans.