Comparisons of the effects of silk elastin and collagen sponges on wound healing in murine models

Introductions: Silk elastin, a recombinant protein with repeats of elastin and silk fibroin, possesses a self-gelling ability and is a potential wound dressing material. The aim of this study is to elucidate the mechanism of the wound healing-promoting effect of silk elastin by comparing its in vivo behavior in a mouse wound model with that of a collagen sponge. Methods: Skin defects (8 mm in diameter) were created on the backs of C57BL/6J and BKS.Cg- + Lepr/+Lepr db male mice. Silk elastin sponges of 2.5 or 5.0 mm thickness, as well as collagen sponges, were placed on the wounds and secured with a polyurethane film. In the control group, only the polyurethane film was applied. The remaining wound area was grossly evaluated, and tissue samples were collected after 7, 14, and 21 days for histological evaluation, including neoepithelialization, wound contraction, granulation tissue formation, newly formed capillaries, and macrophages. Genetic analysis was conducted using real-time polymerase chain reaction. Results: In the study with C57BL/6J, there were no significant differences between the silk elastin and collagen sponge groups. Similarly, in the study using BKS.Cg- + Lepr/+Lepr db, no significant differences were found in the remaining wound area and granulation tissue formation between the silk elastin and collagen sponge groups. However, on day 14, the 5.0-mm-thick silk elastin sponge group showed increased macrophages, longer neoepithelialization, and more frequent angiogenesis compared to other groups. Gene expression of inducible nitric oxide synthase and arginase-1 was also higher in the 5.0 mm thick silk elastin sponge group. Conclusions: Silk elastin sponges demonstrated superior neoepithelialization and angiogenesis compared to collagen sponges. The results suggest that silk elastin and collagen sponges promote wound healing through different mechanisms, with silk elastin possibly enhancing wound healing by facilitating increased macrophage migration. Further studies are needed, but silk elastin shows great potential as a versatile wound dressing material.