Transplanted fat adapts to the environment of the recipient: An animal study using a murine model to investigate the suitability of recipient obesity mismatch in face transplantation.

Introduction: Face transplantation can offer patients with severe facial deformities a better quality of life, but questions of donor suitability remain unanswered. The aim of this study is to determine how an obesity mismatch between donor and recipient affects facial fat graft retention and cellular properties, potentially increasing the donor pool substantially. We hypothesized that facial fat would respond to the microenvironment of the recipient and developed an animal model to evaluate this hypothesis.

Methods: This study utilized 30 C57BL/6J wild-type (WT) and 30 diet-induced obese (DIO), immunologically identical mice. One hundred seventy-five micrograms of perigonadal fat was harvested from 10 mice from each group and transplanted to the subcutaneous scalp of the remaining mice. Ten DIO mice were implanted with DIO donor fat and 10 with WT donor fat. The 10 WT mice were implanted with DIO fat and 10 with WT fat. Recipients underwent micro-CT scans at 2 days and 2, 4, 6, 8, 10, and 12 weeks postoperation. Scans were 3D-reconstructed to assess transplanted fat volume. At 12 weeks, the transplanted fat was analyzed by hematoxylin-eosin staining.

Results: Volume retention of the transplanted fat depended on recipient phenotype, which was confirmed through ANOVA and Student-Newman-Keuls test. Graft volume with a DIO recipient increased with both a DIO (25.6%) and a WT (24.4%) donor from 2 days to 12 weeks postoperation. In a WT recipient, graft volume decreased when the donor was WT (54.0%) and DIO (53.0%). Average cellular volume was also dependent on the recipient phenotype.

Conclusion: This study demonstrates that fat transplanted to the facial region responds to the surrounding microenvironment both macroscopically and microscopically. This study has large implications in donor suitability in face transplant, as it indicates that a donor-recipient obesity mismatch may be acceptable.