Stem cells, mature adipocytes, and extracellular scaffold: What does each contribute to fat graft survival?

Background Soft tissue engineering offers new perspectives for improving fat graft survival, for which the appropriate association of cells and scaffold seems essential. This study aimed to analyze the survival of free-cell grafts compared with adipose-derived stem cells (ASCs) seeded on collagen scaffolds. Methods Adipose tissue from a single volunteer was used for the following preparations: purified adipose tissue, isolated mature adipocytes (free-cell graft), cultured ASCs without scaffold (free-cell graft), collagen scaffold only, cultured ASCs in collagen scaffold without and with bioactive factors, and freshly-isolated ASCs in collagen scaffold. These were grafted on 18 nude mice for 2 months, after which specimens were evaluated grossly and histologically using hematoxylin-phloxine-safran (HPS), Oil-Red-O, and antivimentin labeling. Specimens and animals were weighed before implantation and after explantation, and weight values were statistically analyzed. Results Free-cell grafts (mature adipocytes and free ASCs) showed complete resorption in 50 and 60% of the animals (remaining weight fraction was 22.5 and 5.3%, respectively). The survival of purified adipose tissue was 81.8% (statistically greater compared with free-cell grafts; p < 0.05). In the ASCs-scaffold association, the remaining weight fractions (87.3-70.4%) were statistically greater than in free-cell grafts (5.3-22.5%; p < 0.05), but the difference between ASC-scaffolds and fat grafts was not statistically significant. These results were confirmed by clinical and histologic observations. Conclusion Three-dimensional collagen scaffolds seem to improve survival of ASCs compared with free-cell grafts (adipocytes and free ASCs).