Fate of Adipose-Derived Stromal Vascular Fraction Cells after Co-implantation with Fat Grafts: Evidence of Cell Survival and Differentiation in Ischemic Adipose Tissue

Background: Some studies have suggested that adipose-derived stromal vascular fraction is a potential cell source responsible for the improved quality and long-term retention of fat grafts, but studies that have clearly demonstrated the survival and differentiation potential of the implanted stromal vascular fraction cells as being dynamic phenomena have not been widely reported. Methods: The authors isolated stromal vascular fraction cells from C57BL/6J-GFP mice. Green fluorescence protein-positive stromal vascular fraction cells were mixed with minced inguinal adipose tissue harvested from C57BL/6J mice and then co-implanted into BALB/c nude mice. The survival of implanted green fluorescence protein-positive stromal vascular fraction cells was tracked by in vivo fluorescence imaging for 56 days. Immunofluorescence staining was used to analyze the differentiation of green fluorescence protein-positive stromal vascular fraction cells occurring in ischemic adipose tissue at 7, 14, 28, 35, 42, or 56 days. Results: The fluorescence signal intensity fell drastically within the first 14 days after co-implantation and continued to decrease thereafter, with 17.3 percent signal intensity (relative to day 1) at 56 days. Immunofluorescence staining revealed that some green fluorescence protein-positive cells can spontaneously differentiate into adipocytes from day 7, and some of the implanted stromal vascular fraction cells can incorporate into new blood vessels. Conclusions: The authors show convincing evidence for dynamic changes of stromal vascular fraction cells after co-implantation with fat grafts. The results prove the principle that implanted stromal vascular fraction cells can survive in the ischemic microenvironment of fat grafts and participate in the process of adipogenesis and angiogenesis.