Transplanted Fat Adapts to the Environment of the Recipient: A Study to Investigate the Suitability of Donor Recipient Obesity Mismatch in Face Transplantation

Introduction: The primary goal of face transplantation is to restore normal face structure and improve function, offering patients with severe facial deformities a better quality of life and increased social integration. Research regarding factors affecting donor suitability remains lacking. There has been no investigation of the long-term effects of transplanting an obese donor face onto a normal recipient or vice versa. The aim of this study is to determine how an obesity mismatch between donor and recipient affects transplanted facial fat graft retention and cellular properties, potentially increasing the donor pool substantially.

Methods: 60 male mice were utilized in this study: 30 C57BL/6J wild-type (WT) and 30 diet-induced obese (DIO) mice. 175ug of fat was harvested from the perigonadal fat pads of 10 euthanized mice from each group. The 20 remaining mice in each group served as recipients. A small incision was made between the ears of each recipient mouse and a subcutaneous pocket formed. Harvested fat was implanted in this location and the incision closed. 10 DIO mice were implanted with fat from a DIO donor, 10 with fat from a WT donor. 10 WT mice were implanted with DIO fat and 10 with WT fat. Recipient mice underwent micro-CT scans at 2 days, 2, 4, 6, and 8 weeks postoperative. Scans were 3d reconstructed and fat transplant volume assessed. At 8 weeks, mice were euthanized and transplanted fat analyzed histologically.

Results: Volume retention of the facial fat graft was entirely dependent on the recipient phenotype, confirmed through ANOVA analysis and Student-Newman-Keuls Test. Volume of the graft when the recipient was DIO increased with both a DIO and WT donor (25.6% and 24.4% increase respectively). When the recipient was WT, the graft volume decreased when the donor was WT (-54.0%) and DIO (-53.0%). Average cellular volume also demonstrated the same trend, with a lower volume when the recipient was WT and higher volume when the recipient was DIO, regardless of the donor phenotype.

Conclusion: This study demonstrates that fat transplanted to the facial region responds to the surrounding microenvironment both macroscopically and microscopically. This indicates that adipose cells respond to the metabolic environment of the recipient. Furthermore, this study demonstrates that microscopically, fat cells adapt to their recipient host environment as well through cellular volume. This study has large implications in donor suitability in face transplant, as it indicates that a donor-recipient obesity mismatch may be acceptable.