Local Subcutaneous Injection of Erythropoietin Might Improve Fat Graft Survival, Whereas Continuous Infusion Using an Osmotic Pump Device Was Harmful by Provoking an Overwhelming Foreign Body Reaction in a Nude Mouse Model

ABSTRACT

BACKGROUND: Since the survival of grafted fat requires successful revascularization, we hypothesized that local delivery of erythropoietin (EPO), a hemangiogenic and antiapoptotic factor, might enhance the survival of fat grafts in a nude mouse model. METHODS: Our experiment consisted of 2 parts. The first involved direct injection of EPO or saline at the grafting site before fat grafting and for 4 days afterwards. In the second part, EPO or saline was delivered continuously for 1 week via an osmotic pump device, and a group without an implantable pump represented the control group. After 16 weeks, the surviving fat grafts were weighed and subjected to histomorphometry. RESULTS: In the first experiment, fat graft survival was higher in the EPO-injected group, but not statistically significant (69.2% vs. 59.2%; P=0.21). Histomorphometry showed significantly higher levels of microvessel formation and less cystic degeneration in the EPO-injected group. In the second experiment, the survival rate was significantly lower in both pump groups than in the control group (40.7% in the EPO pump group, 7.7% in the saline pump group, and 66.7% in the control group). CONCLUSIONS: Local injection of EPO into the fat graft site appeared to improve graft survival, with increased angiogenesis, suppressed inflammation, and decreased degeneration. However, the insertion of an osmotic pump exerted detrimental effects on graft survival and the histomorphometric profiles of the fat graft compared with the control group due to the overwhelming foreign body reaction.