Intercellular cytosolic transfer correlates with mesenchymal stromal cell rescue of umbilical cord blood cell viability during ex vivo expansion

• Published in: Cytotherapy (Oxford, England) England), 2012-10, Vol.14 (9), p.1064-1079
• Main Authors: Chu, Pat P.Y, Bari, Sudipto, Fan, Xiubo, Gay, Florence P.H, Ang, Justina M.L, Chiu, Gigi N.C, Lim, Sai K, Hwang, William Y.K
• Format: Article
• Language: English
• Subjects: Advanced Basic Science; Animals; Cell Culture Techniques; Cell Death - genetics; Cell Fusion; Cell Proliferation; Cell Survival; Cell Transdifferentiation; cell viability; Coculture Techniques; Cytosol - metabolism; Fetal Blood - cytology; Green Fluorescent Proteins - analysis; Humans; intercellular transfer; Leukocytes, Mononuclear - cytology; Membrane Potential, Mitochondrial; mesenchymal stromal cells; Mesenchymal Stromal Cells - cytology; Mice; NIH 3T3 Cells; Other; Review; umbilical cord blood
• ISSN: 1465-3249; 1477-2566
• DOI: 10.3109/14653249.2012.697146

Abstract Background aims Mesenchymal stromal cells (MSC) have been observed to participate in tissue repair and to have growth-promoting effects on ex vivo co-culture with other stem cells. Methods In order to evaluate the mechanism of MSC support on ex vivo cultures, we performed co-culture of MSC with umbilical cord blood (UCB) mononuclear cells (MNC) (UCB-MNC). Results Significant enhancement in cell growth correlating with cell viability was noted with MSC co-culture (defined by double-negative staining for Annexin-V and 7-AAD; P < 0.01). This was associated with significant enhancement of mitochondrial membrane potential ( P < 0.01). We postulated that intercellular transfer of cytosolic substances between MSC and UCB-MNC could be one mechanism mediating the support. Using MSC endogenously expressing green fluorescent protein (GFP) or labeled with quantum dots (QD), we performed co-culture of UCB-MNC with these MSC. Transfer of these GFP and QD was observed from MSC to UCB-MNC as early as 24 h post co-culture. Transwell experiments revealed that direct contact between MSC and UCB-MNC was necessary for both transfer and viability support. UCB-MNC tightly adherent to the MSC layer exhibited the most optimal transfer and rescue of cell viability. DNA analysis of the viable, GFP transfer-positive UCB-MNC ruled out MSC transdifferentiation or MSC-UCB fusion. In addition, there was statistical correlation between higher levels of cytosolic transfer and enhanced UCB-MNC viability ( P < 0.0001). Conclusions Collectively, the data suggest that intercellular transfer of cytosolic materials could be one novel mechanism for preventing UCB cell death in MSC co-culture.