Frozen Fat Grafts Maintain Vascular Endothelial Growth Factor Expression and Mediate Angiogenesis During Adipose-Derived Stem Cell Enrichment for Soft Tissue Augmentation

Abstract

Background: Fresh fat grafts are commonly used in both esthetic and reconstructive surgeries, but the graft resorption rate varies. Cryopreservation of unused fat for later touch-up is one option to resolve this variation. In our previous studies, we found that fat cryopreservation may be a practical strategy for storing fat tissue. To explore the cryopreservation method, we evaluated the role of vascular endothelial growth factor (VEGF) in human frozen fat grafts.

Methods: The concentration of VEGF in human frozen fat grafts subjected to different preservation times was determined using Western blotting and enzyme-linked immunosorbent assay. The angiogenic effect of frozen fat grafts was evaluated using a chorioallantoic membrane assay. Furthermore, the impact of adding human adipose-derived stem cells (hADSCs) or different concentrations of avastin (bevacizumab) to frozen fat grafts on angiogenesis was assessed. The viability of frozen fat grafts with or without hADSCs was evaluated using a nude mouse implantation study. Explanted fat tissues were examined on days 1, 4, 7, 14, 28, and 90, and morphological and histological analyses, immunohistochemistry, and enzyme-linked immunosorbent assay (VEGF concentration) were carried out.

Results: No significant difference in VEGF concentration between fresh and frozen fat was observed with respect to preservation duration. In the chorioallantoic membrane assay, frozen fat grafts with hADSCs displayed significantly enhanced angiogenesis. Avastin was found to decrease angiogenesis in frozen fat grafts. However, in the nude mouse implantation study, frozen fat grafts displayed VEGF maintenance, with the highest concentration observed on day 7. Adding hADSCs to the graft further increased the VEGF concentration and CD31 expression. Fat graft viability was found to be higher in the frozen fat grafts containing hADSCs than in grafts without hADSCs.

Conclusions: Human fat grafts can maintain VEGF expression under frozen conditions for at least 12 months. The addition of hADSCs to the frozen fat graft could further enhance angiogenesis, VEGF expression, and fat cell viability.