Adipose Tissue Transplant Impregnated with Collagen Increases Engraftment by Promoting Cell Proliferation, Neovascularization, and Macrophage Activity in a Rat

Objectives: To clarify the effect of impregnating transplanted adipose tissue with collagen on angiogenesis, cell proliferation, and tissue remodeling process and to reveal whether collagen impregnation contributes to improving the engraftment of transplanted adipose tissue in rats.Methods: Adipose tissue was harvested from the inguinal and injected into the back of the rat, in addition to collagen. Engraftment tissue was harvested, semi-quantitatively evaluated and underwent HE or Perilipin staining. Moreover, we evaluated viable adipocyte counts and neovascularization. Macrophages were evaluated using flow cytometry, and the adiponectin or VEGF mRNA was detected using real-time PCR. Results: By impregnating transplanted adipose tissue with collagen, higher engraftment rate semi-quantitatively and a greater number of new blood vessels histologically were identified. Perilipin staining revealed a higher adipocyte number. The total cell, M1 macrophage, and M2 macrophage count were higher. There was increased adiponectin mRNA significantly at week 4 compared to that at week 1 after transplantation. Note that the expression levels of VEGF mRNA increased.Discussion: In rats, collagen impregnation enhanced cell proliferation, induced M2 macrophages, which are involved in wound healing, and promoted adipocytes and neovascularization. Therefore, impregnating transplanted adipose tissue with collagen could increase the engraftment rate of adipose tissue.