Differentiation of umbilical cord blood derived- mesenchymal stem cells to brown adipocytes

Mitochondria-enriched brown fat cells provides energy consumption by burning "stored triglycerides" and converting th energy to heat, therefore they are potentially useful cells for the treatment of diabetes, obesity and various metabolic diseases associated with obesity. Umbilical Cord Blood derived-Mesenchymal Stem Cells (UCB-MSC) are less immunogenic than other SC sources such as Bone Marrow derived- Mesenchymal Stem Cells (BM-MSC), and can be used for allogenic and autologous transplantation. There is not any study in the literature available to demonstrate differentiation of UCB-MSC to brown adipocytes until now. In this study we aimed to perform in vitro differentiation of UCB-MSC to brown adipocytes and compare their differentiation capacity and efficiency with AD-MSCs. In this study, the UCB-MSCs were collected from 10 placenta and umbilical cord blood samples which are routinely discarded after a normal birth in Ege University Faculty of Medicine, Department of Gynecology and Obstetrics, AD-MSCs were collected from 6 voluntary patients who undergo Liposuction / lipectomy surgery at Ege University Faculty of Medicine Department of Plastic and Reconstructive Surgery. Differentiation ability of UCB-MSCs to white and brown adipocytes was compared with AD-MSCs. Isolated MSCs were characterized by flow cytometry analysis. According to the results of flow cytometry both UCB-MSCs and AD-MSCs showed high rate of positivity for CD90 and CD105 surface markers while they were negative for CD34 and CD45. MSCs in the 3rd passage were differentiated to white and brown adipocytes by culturing them in two different differentiation mediums, for white and brown adipocyte differentiation. MSCs were cultured in differentiation medium containing recombinant bone morphogenic protein7 (BMP7) to give brown adipocytes. The results of Oil Red O staining used for characterizing white and brown adipocytes demonstrated that white and brown adipocytes obtained from AD-MSCs showing 85% and 61% of red pixels, respectively, while it was 3% and 1.9%, respectively for white and brwon adipocytes obtained from UCB-MSCs. Brown adipocyte-specific UCP1 protein content, was determined by fluorescence microscopy and Western blot analysis. According to the results of the fluorescence analysis, brown adipocytes obtained from both UCB-MSCs and AD-MSCs contain more UCP1 protein than undifferentiated control cells but round shining bodies were only seen in cytoplasm of brown adipocytes obtained from AD-MSCs. According to the literature, they can be clustered mitochondria formed from large numbers of mitochondria that come together. The results of Western blot analysis show that brown adipocytes obtained from UCB-MSCs and AD-MSCs express UCP1 protein 4 and 10.64 times, respectively, more than undifferentiated MSCs (P<0.004). As a result, while AD-MSCs differentiated to white and brown adipocytes abundantly and efficiently, UCB-MSCs showed only a little differentiation tendency to adipocytes. According to the results obtained from this study, UCB-MSCs are not appropriate SC type to be differentiated to both white and brown adipocytes. So, they may not give positive results similar to AD-MSCs during treatment with adipocyte cell transplantation or in reconstructive surgery. In contrast, AD-MSCs may be a new promising therapeutic approach for treatment of diabetes, obesity and its related metabolic disorders because of their high efficiency in differentiation capacity to brown adipocytes. Further in vivo and clinical studies are needed in this regard.