Enhancing fat graft retention through adipose tissue browning: a systematic review.

Background: Recently, existing researches have gradually recognized the critical biological behaviour played by spontaneous or exogenous-induced browning conversion in fat transplantation. However, no comprehensive review explored the fat grafts remodeling process toward browning and such role in fat graft retention.

Aims: This study aimed to elucidate the behavioral characteristics of browning changes following fat grafting, as well as its benefits and mechanisms on the survival of transplanted fat.

Methods: Databases including Web of science, PubMed, Ovid medline, and Embase were searched from inception through September 2024. Studies related to fat grafts browning in fat transplantation were systematically reviewed, in accordance with the inclusion and exclusion criteria.

Results: We evaluated 14 studies including 13 animal works and one clinical report. Five studies directly transplanted fat without any browning induction, while others utilized either beige fat or pre-treated grafts with browning stimuli.Data shown that around the periphery of fat grafts (predominantly in survival zone), early accumulations of graft browning can be observed, dynamically accompanying the stable remodeling of the graft. Post-transplantation spontaneous browning typically begins around day 7, stabilizes after approximately 3 months, and may revert to white adipose tissue. The favorable browning up-regulation behavior of fat graft can enhance graft retention by promoting early angiogenesis, reducing inflammation, and upregulating adipogenesis. The origin of beige adipocytes, whether from the conversion of white adipocytes or the regeneration of progenitor cells, remains underdiscussed.

Conclusions: Notwithstanding the relatively limited sample and study levels, this work offers valuable insights into the benefits of browning behavior on enhancing fat graft retention. The in-depth understanding of the underlying mechanism of browning and manipulating its switching in fat grafting will contribute in several ways to achieving desired clinical outcomes.