Quality and Quantity-Cultured Human Mononuclear Cells Improve Human Fat Graft Vascularization and Survival in an In Vivo Murine Experimental Model.

Abstract

Autologous fat grafting is becoming an increasingly popular technique used by plastic surgeons to correct volume-lacking or deformed areas. The survival rate of grafted fat is a major concern of autologous fat grafting. Cell-assisted lipotransfer has been widely used because it can increase the fat survival rate and grafts are easy to obtain. With the great respect and appreciation, we read the recently published article entitled “Quality and Quantity–Cultured Human Mononuclear Cells Improve Human Fat Graft Vascularization and Survival in an In Vivo Murine Experimental Model,” by Geeroms et al.1 By presenting quality and quantity–cultured mononuclear cells (MNC-QQ) containing endothelial progenitor cells, they provide a totally new choice that can stimulate vascularization of fat grafts and improve graft survival rates. Previous studies have paid more attention to the role of stromal vascular fraction, which may assist graft survival through a range of mechanisms, including increased angiogenesis. Because stromal vascular fraction is a heterogeneous population, a tremendous barrier is the inability to readily isolate sufficient functionally distinct cell subpopulations, such as endothelial cells, from stromal vascular fraction.2,3 In an effort to expand a large number of endothelial progenitor cells, the quality and quantity culture was developed. The quality and quantity culture not only overcomes the limitation of the low number of endothelial progenitor cells in the peripheral blood but also obtains a highly vasculogenic cell population, which improves fat graft quality. Although this protocol is marvelous, the evidence provided by the authors is somewhat inadequate and should be further improved before clinical application. Although stromal vascular fraction is one of the most commonly used cells for cell-assisted lipotransfer, the selection of stromal vascular fraction as the control group in this study may interfere with the experimental results to some extent. As the result showed in the article, the graft weight persistence showed no significant difference in the stromal vascular fraction and MNC-QQ groups. However, MNC-QQ had a significantly higher vessel density compared with stromal vascular fraction to the fat grafts. Excluding experimental errors, the factors influencing the persistence of fat grafting are not fully understood. As a previous study reported, oxygen diffusion capability is one of the factors that influences fat graft survival.4 There may be some limitations to the conclusion that the high graft survival rate was a consequence of the rich vascular network. In addition, we failed to find detailed information regarding gross view and histological analysis of the grafted fat, which are of vital importance to the reader. Because the vascularization is closely related to the central thickness of the fat grafts, the shape of the graft is important. Fat graft volume is often used to assess adipocyte viability, whereas using the explanted graft weight may cause a large error. As the authors mentioned in their article, postoperative edema or incomplete resorption of phosphate-buffered saline may cause errors in experimental results. This may account for the inconsistent trend in vascular density and graft weight persistence in the result. We believe a more detailed analysis will increase its clinical reference value in future studies. DISCLOSURE Neither author has a financial disclosure to report. No funding was received for this communication. Danying Wang, M.D.Bo Chen, M.D., Ph.D.Department of Plastic and Reconstructive SurgeryPlastic Surgery HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing, People’s Republic of China