title: Intercellular cytosolic transfer correlates with mesenchymal stromal cell rescue of umbilical cord blood cell viability during ex vivo expansion.
abstract: OBJECTIVE
  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.
authors: Department of Hematology, Singapore General Hospital, Singapore.
authors: Pat P Y
authors: PP
authors: Chu
authors: Sudipto
authors: S
authors: Bari
authors: Xiubo
authors: X
authors: Fan
authors: Florence P H
authors: FP
authors: Gay
authors: Justina M L
authors: JM
authors: Ang
authors: Gigi N C
authors: GN
authors: Chiu
authors: Sai K
authors: SK
authors: Lim
authors: William Y K
authors: WY
authors: Hwang
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D016923:Cell Death / Q000235:genetics; D002459:Cell Fusion; D049109:Cell Proliferation; D002470:Cell Survival; D054338:Cell Transdifferentiation; D018920:Coculture Techniques; D003600:Cytosol / Q000378:metabolism*; D005312:Fetal Blood / Q000166:cytology*; D049452:Green Fluorescent Proteins / Q000032:analysis; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology*; D053078:Membrane Potential, Mitochondrial; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D051379:Mice; D041681:NIH 3T3 Cells
chemical_list: D049452:Green Fluorescent Proteins