A Novel Method of Human Adipose-Derived Stem Cell Isolation with Resultant Increased Cell Yield.

Abstract

Sir: We have read with great interest the article entitled “A Novel Method of Human Adipose-Derived Stem Cell Isolation with Resultant Increased Cell Yield.”1 In the article, Tevlin et al. developed a new method that allows a higher extraction rate of adipose-derived stem cells with similar differentiation capacities compared with the conventional method.2 We would like to thank the authors for the study because it is increasingly important to develop new techniques that can facilitate the extraction of adipose-derived stem cells for use in cell therapy. Nevertheless, some points raised questions and need some discussion. First, the percentage of adipose-derived stem cells present in the stromal vascular fraction obtained with the “conventional” method seems very low (1.95 percent). Indeed, in our experience and in the literature, the average proportion of adipose-derived stem cells present in the stromal vascular fraction is approximately 30 to 40 percent.3 Moreover, stromal vascular fraction is a heterogeneous mix of cells, and the percentage of immune cells modified the adipogenic differentiation capacities of stromal vascular fraction. Therefore, it would have been interesting to compare the percentage of erythrocytes, endothelial cells, and immune cells to determine whether this new method modified the extraction rate of other cells that could be responsible for the modification of the adipogenic differentiation capacities of the adipose-derived stem cells. Moreover, the authors said that they studied the function of the adipose-derived stem cells isolated with their new methods; however, it seems that they characterized the functions of the adipose-derived stem cells but also the function of all the cells that are present in the stromal vascular fraction. The authors demonstrated that the adipose-derived stem cells extracted with the new method expressed more bone morphogenetic protein (BMP) receptor 1a and 1b. It would be interesting to determine also the expression of BMP receptor 2, receptors of BMP4 and BMP7, inducers of osteogenic differentiation of adipose-derived stem cells. Moreover, it would be interesting to determine whether this new technique isolates a different population of adipose-derived stem cells based on this BMP receptor expression. A minor remark is that the study was realized with a human sample; therefore, it should be important to indicate the number of samples analyzed for this study knowing the interpatient variability. The authors claimed that their new method of stromal vascular fraction extraction is different with regard to two aspects compared with the conventional method. Foremost, this method uses a stronger and quicker shaking during digestion, and the modification of the digestion media. Indeed, the media are enriched with different products and thus it is really difficult to determine which product is responsible for the higher extraction rate. Moreover, the higher percentage of extracted adipose-derived stem cells could be simply linked to the concentration of collagenase, which is three times more important in the new digestion media compared with the conventional one. The development of rapid, simple, and enzyme-free procedures to isolate stromal vascular fraction is the new goal of cell therapy. Therefore, the use of digestion media containing more of the chemical products, even if they seem to not affect cell viability, could be a real issue for clinical use and from the regulatory framework point of view.4,5 DISCLOSURE None of the authors has a financial interest in any of the products, devices, or drugs mentioned in this communication. The authors received no funding support for this work. Jérôme Laloze, M.D.Department of Plastic and Reconstructive SurgeryRangueil University HospitalToulouse, FranceDepartment of Maxillofacial and Reconstructive Surgeryand StomatologyCHU DupuytrenLimoges, France Nicolas Bertheuil, M.D.Department of Plastic, Reconstructive and Aesthetic SurgeryHospital SudUniversity of Rennes 1Rennes, France Julie Usseglio-Grosso, M.D.Department of Maxillofacial and Reconstructive Surgeryand StomatologyCHU DupuytrenLimoges, France Audrey Varin, Ph.D.STROMAlabUMR5273 CNRS/UPS/EFS - INSERM U1031Rangueil University HospitalToulouse, France Benoit Chaput, M.D.Department of Plastic and Reconstructive SurgeryRangueil University HospitalToulouse, France