Importance of mesenchymal stem cells in autologous fat grafting: a systematic review of existing studies.

Autologous fat grafting (lipofilling) enables repair and augmentation of soft tissues and is increasingly used both in aesthetic and reconstructive surgery. Autologous fat has several advantages, including biocompatibility, versatility, natural appearance, and low donor site morbidity. The main limitation is unpredictable graft resorption, which ranges from 25%-80%, probably as a result of ischaemia and lack of neoangiogenesis. To obviate these disadvantages, several studies have searched for new ways of increasing the viability of the transplanted tissue. One promising approach has been to enrich the fat graft with adipose tissue-derived mesenchymal stem cells (ASC) before transplantation. We have reviewed original studies published on fat transplantation enriched with ASC. We found four murine and three human studies that investigated the subject after a sensitive search of publications. In the human studies, so-called cell assisted lipotransfer (CAL) increased the ASC concentration 2-5 times compared with non-manipulated fat grafts, which caused a questionable improvement in survival of fat grafts, compared with that of traditional lipofilling. In contrast, in two of the murine studies ASC-concentrations were increased 1250 and 6250 times, respectively, by ASC ex vivo expansion, which resulted in considerably improved fat transplant survival as well as quality. This effect of high-level enrichment with ASC is thought to have been caused by paracrine signalling, cellular differentiation, or both. The surgical and tissue handling techniques used in lipofilling are well proved, but the added effect of high-level enrichment with ex vivo expanded ASC still needs to be investigated properly in human lipofilling studies, combined with a thorough follow up and matched control groups. In conclusion, ASC-enriched lipofilling theoretically has the potential for transforming lipofilling from a relatively unpredictable intervention into one in which the resorption rate, quality of tissue, and safety can be predicted, and possibly superior to prosthetic implantation.