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.

Regeneration of partially decellularized tracheal scaffolds in a mouse model of orthotopic tracheal replacement.

Decellularized tracheal scaffolds offer a potential solution for the repair of long-segment tracheal defects. However, complete decellularization of trachea is complicated by tracheal collapse. We created a partially decellularized tracheal scaffold (DTS) and characterized regeneration in a mouse model of tracheal transplantation. All cell populations except chondrocytes were eliminated from DTS. DTS maintained graft integrity as well as its predominant extracellular matrix (ECM) proteins. We then assessed the performance of DTS in vivo. Grafts formed a functional epithelium by study endpoint (28 days). While initial chondrocyte viability was low, this was found to improve in vivo. We then used atomic force microscopy to quantify micromechanical properties of DTS, demonstrating that orthotopic implantation and graft regeneration lead to the restoration of native tracheal rigidity. We conclude that DTS preserves the cartilage ECM, supports neo-epithelialization, endothelialization and chondrocyte viability, and can serve as a potential solution for long-segment tracheal defects.

Transplantation of a Human Tissue-Engineered Bowel in an Athymic Rat Model.

Intestinal failure is a serious clinical condition characterized by loss of motility, absorptive function, and malnutrition. Current treatments do not provide the optimal solution for patients due to the numerous resulting complications. A bioengineered bowel that contains the necessary cellular components provides a viable option for patients. In this study, human tissue-engineered bowel (hTEB) was developed using a technique, whereby human-sourced smooth muscle cells were aligned and neoinnervated using human-sourced neural progenitor cells, resulting in the formation of intrinsically innervated smooth muscle sheets. The sheets were then rolled around hollow tubular chitosan scaffolds and implanted in the omentum of athymic rats for neovascularization. Four weeks later, biopsies of hTEB showed vascularization, normal cell alignment, phenotype, and function. During the biopsy procedure, hTEB was transplanted into the same rat's native intestine. The rats gained weight and 6 weeks later, hTEB was harvested for studies. hTEB was healthy in color with normal diameter and with digested food in the lumen, indicating propulsion of luminal content through the hTEB. Histological studies indicated neomucosa with evidence of crypts and villi structures. This study provides proof of concept that hTEB could provide a viable treatment to lengthen the gut for patients with gastrointestinal disorders.