Systemic Administration of Adipose-Derived Stromal Cells Concurrent with Fat Grafting

Sir: We have read with interest Hong et al.’s article entitled “Systemic Administration of Adipose-Derived Stromal Cells Concurrent with Fat Grafting,” in which they describe improved retention of fat grafts when the grafts are supplemented with adipose-derived stromal cells.1 The authors injected ex vivo–expanded adipose-derived stromal cells intravenously after fat grafting in wild-type B6 mice. The use of three mice strains [i.e., green fluorescence protein–expressing C57BL/6J (B6) mice (adipose donors), wild-type B6 mice (recipient of adipose and adipose-derived stromal cells), and DsRed-expressing B6 mice (source of adipose-derived stromal cells)] is highly appreciated for performing such studies. Previous reports regarding pre-enrichment of fat grafts with adipose-derived stromal cells are different in that the authors had directly mixed ex vivo–expanded adipose-derived stromal cells before grafting of autologous fat.2,3 In the current study by Hong et al., the cells were injected intravenously after fat grafting.1 The cells need a signal, such as some sort of injury or inflammation, to home at some site inside the body. It is interesting to know that by what mechanism did the intravenously injected cells move to the fat-grafted site? It is also important to record the percentage of cells that relocated to the grafted site, as a similar signal (expression of DsRed) was also observed in controls in Hong et al.’s study. The authors used 1 × 105 cells for intravenous injection, which seems low as compared to cell numbers used by others for pre-enrichment of adipose tissue grafts.2 The potential of cells is severely compromised in vitro with passaging; however, the authors used the cells at passages 3 to 7, which raises questions about the consistency of results.4 In addition, it is equally important to evaluate other routes, such as the tail vein, besides the supraperiosteal plane of the skull for transplantation of adipose-derived stromal cells and to track their homing. Fat grafting is considered an ideal procedure for the augmentation of soft tissues, especially for breast reconstruction, severe burn scars, rejuvenation of aged skin, congenital abnormalities, posttraumatic malformations, contour deformities, and so on. Although the practice of fat grafting is not new, and it is a safe and natural method of soft-tissue augmentation, the major impediment is an unpredictable result due to the low survival rate of the transplanted graft.5 This low survival rate and abridged reliability of transplanted fat grafts may affect the clinical outcomes. This lack of inconsistency of final clinical outcomes is often associated with absorption of grafted tissue of up to 80 percent.2 Due to this absorption of grafted tissue, often multiple tissue-grafting procedures are required to obtain satisfactory results. Multiple procedures, however, make autologous fat grafting an expensive process. My colleagues and I have recently evaluated the effect of direct supplementation of adipose-derived stromal cells on fat graft retention. We directly compared the traditional fat graft with fat grafts pre-enriched with adipose-derived stromal cells in patients with contour deformities of the face. Even after 24 weeks, there was significantly lower fat absorption in the cell-enriched group (5 ± 4.4 percent) as compared with the group in which only fat grafts were injected (31 ± 13 percent). Mean physician and patient satisfaction scores were significantly improved after pre-enrichment of fat with adipose-derived stromal cells. Significantly lower graft absorption due to the use of adipose-derived stromal cells improves the clinical outcomes of conventional fat grafting for facial contour deformities in our study. DISCLOSURE The author has no financial conflicts of interest to disclose.