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.
Highlights
Mesenchymal stromal cells (MSC), known as multipotent mesenchymal stem cells, have been used in various clinical applications such as tissue engineering [1], regenerative medicine [2] and immunoregulatory therapy [3]
We have demonstrated that MSC co-culture supports the viability of frozen-thawed umbilical cord blood (UCB) cells, and this effect was best seen in the presence of cell– cell contact with MSC
We have shown that the transfer of cytosolic materials occurs between MSC and co-cultured UCB cells, and that a statistically significant positive correlation exists between cytosolic transfer and enhanced UCB cell viability
Summary
Mesenchymal stromal cells (MSC), known as multipotent mesenchymal stem cells, have been used in various clinical applications such as tissue engineering [1], regenerative medicine [2] and immunoregulatory therapy [3]. Mesenchymal stromal cells (MSC) have been observed to participate in tissue repair and to have growthpromoting effects on ex vivo co-culture with other stem cells. 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 Ͻ0.01). This was associated with significant enhancement of mitochondrial membrane potential (P Ͻ0.01). 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. The data suggest that intercellular transfer of cytosolic materials could be one novel mechanism for preventing UCB cell death in MSC co-culture
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