Histopathologic Evaluation of Adipose Autografts in a Rabbit Ear Model

Abstract

Injection of autologous adipose tissue removed via liposuction has been used clinically for facial contouring, the aging face, furrows, facial atrophy, acne scars, nasolabial folds, chin, and various other surgical defects. Survival rates for autografts of fat have been quoted anywhere from 30% to 80%. Our study uses a reproducible rabbit animal model for autotransplantation of adipose tissue and examines the histopathologic changes that occur to the graft over time. Autogenous subcutaneous fat was removed from a dorsal scapular donor site, treated to stimulate cannula damage as in liposuction, then reinjected at the base of the ear. Histologic examination of the grafts were made at 5, 10, 15, 20, 40, and 100 days after transplantation. Hematoxylin-eosin sections were graded on degree of fibrosis present (0 to 4+), viable fat (1 to 10), degree of inflammation (0 to 4+), and neovascularization (+ or -). Viability of fat decreased from 8.5 to 10 at 5 days to 2 viability at 40 days. Acute inflammation peaked at 10 days, followed by the chronic inflammatory response with macrophages and multinucleated giant cells scavenging the dying fat graft. Neovascularization began at 5 days, peaked at 10 days, and remained constant thereafter only at the edge of the graft. Microcysts appeared at 15 days and increased in number in proportion to the decrease in viable fat. In summary, the temporal histologic events are progressive fibrosis; decreased amount of viable fat; inflammation beginning with a neutrophilic response, later a macrophage and giant cell response; and neovascularization at the periphery of the graft insufficient to maintain graft viability. In our animal model, autografts of fat appear to have limited long-term viability and are replaced by fibrous tissue. This may have clinical implications in autografting of fat in facial plastic and reconstructive surgery.