Cell-free fat extract accelerates diabetic wound healing in db/db mice

Cell-free fat extract (CEFFE), the liquid fraction derived from fat tissues, is enriched with a variety of growth factors and possesses pro-angiogenic, anti-apoptotic, and anti-oxidative properties. The aim of this study was to determine if CEFFE could accelerate chronic wound healing in mice with diabetes and investigate its underlying mechanisms. A model of circular full-thickness wound (6 mm diameter) was produced in the central dorsal region of spontaneous type 2 diabetes mellitus db/db mice. The mice were divided to three groups depending on dosage of CEFFE administered for the study; high dose CEFFE group (CEFFE^high; administered 2.5 ml/kg/day via subcutaneous injection for six days), low dose CEFFE group (CEFFE^low; administered 2.5 ml/kg/day via subcutaneous injection for three days), and a control group receiving phosphate buffer solution. Wound closure was evaluated on day 3, 7, 10, and 14 post-operation. Histological analyses, including hematoxylin-eosin staining and Masson's trichrome staining and immunohistological staining of anti-CD31 and anti-CD68, were also performed. Moreover, the effects of CEFFE on proliferation, migration, and tube formation of human immortal keratinocyte cells (HaCaT) and human vascular endothelial cells (HUVEC) were tested in vitro. The results showed that the local injection of CEFFE significantly accelerated wound healing in mice with diabetes. CEFFE improved re-epithelization and collagen secretion, promoted angiogenesis, and inhibited inflammatory macrophage infiltration in vivo. CEFFE also promoted HaCaT proliferation and migration and enhanced tubular formation in cultured HUVEC. It was concluded that CEFFE accelerates wound healing through pro-angiogenic and anti-inflammatory activities.