Three-Dimensional Culture Promotes Secretion of Extracellular Matrix Structure Fat Flap with Lipoaspirates in Vitro

Adipose tissue engineering represents a possible solution for large-volume soft-tissue reconstruction. Although there have been several reports on the construction of tissue-engineered fat (TEF) flaps in vivo and in vitro, each condition has various limitations. Thus, we developed a novel approach for engineering fat tissue using a three-dimensional culture system. We used different volumes of lipoaspirates to fill the same tissue engineering chamber (30%, 50%, 80%, and 100% volume/space ratio) for different periods (3, 5, 7, and 14 days) to determine whether lipoaspirates can form structural fat tissue in vitro. We then studied the histological structure and extracellular matrix (ECM) of the tissue formed in vitro. We selected engineering tissue-like fat of the 80% volume/space ratio group cultured for 7 days to be subcutaneously implanted into mice for up to 3 months, and lipoaspirates without structure in vitro were used as a control. The lipoaspirates from the 80% volume/space ratio group cultured in vitro formed TEF-like tissue, which increased in small adipocytes and ECM with time until becoming stable on day 7. The live/dead test showed that the tissue cultured in vitro remained viable until day 7. Immunofluorescence staining results revealed that the collagen I and IV content increased over time. Moreover, after grafting, "self-assembly" fat had higher volume retention, better vascularization, fewer oil droplets, and less fibrosis than the lipoaspirates without structure in vitro. Therefore, our results demonstrate that lipoaspirates filled in tissue engineering chamber can be cultured in vitro and can "self-assemble" into TEF-like tissue. Furthermore, the "self-assembly" fat tissue produced better grafting results than those of lipoaspirates without structure in vitro.