Ex vivo expansion of hematopoietic stem and progenitor cells: Recent advances

Co-culture of mesenchymal stem cell spheres with hematopoietic stem cells under hypoxia: a cost-effective method to maintain self-renewal and homing marker expression

BACKGROUND

Hematopoietic stem cell (HSC) transplantation is considered a possible treatment option capable of curing various diseases. The aim of this study was the co-culturing of mesenchymal stem cell (MSC) spheres with HSCs under hypoxic condition to enhance the proliferation, self-renewal, stemness, and homing capacities of HSCs.

METHODS AND RESULTS

HSCs were expanded after being subjected to different conditions including cytokines without feeder (Cyto), co-culturing with adherent MSCs (MSC), co-culturing with adherent MSCs + hypoxia (MSC + Hyp), co-culturing with MSCs spheres (Sph-MSC), co-culturing with MSCs spheres + hypoxia (Sph-MSC + Hyp), co-culturing with MSC spheres + cytokines (Sph-MSC + Cyto). After 10 days, total nucleated cell (TNC) and CD34⁺/CD38^- cell counts, colony-forming unit assay (CFU), long-term culture initiating cell (LTC-IC), the expression of endothelial protein C receptor (EPCR), nucleostemin (NS), nuclear factor I/X (Nfix) CXCR4, and VLA-4 were evaluated. The TNC, CD34⁺/CD38^- cell count, CFU, and LTC-IC were higher in the Sph-MSC + Hyp and Sph-MSC + Cyto groups as compared with those of the MSC + Hyp group (P < 0.001). The expanded HSCs co-cultured with MSC spheres in combination with hypoxia expressed more EPCR, CXCR4, VLA-4, NS, and Nfix mRNA. The protein expression was also more up-regulated in the Sph-MSC + Cyto and Sph-MSC + Hyp groups.

CONCLUSION

Co-culturing HSCs with MSC spheres under hypoxic condition not only leads to higher cellular yield but also increases the expression of self-renewal and homing genes. Therefore, we suggest this approach as a simple and non-expensive strategy that might improve the transplantation efficiency of HSCs.

Molecular Modulation of Fetal Liver Hematopoietic Stem Cell Mobilization into Fetal Bone Marrow in Mice

Development of hematopoietic stem cells is a complex process, which has been extensively investigated. Hematopoietic stem cells (HSCs) in mouse fetal liver are highly expanded to prepare for mobilization of HSCs into the fetal bone marrow. It is not completely known how the fetal liver niche regulates HSC expansion without loss of self-renewal ability. We reviewed current progress about the effects of fetal liver niche, chemokine, cytokine, and signaling pathways on HSC self-renewal, proliferation, and expansion. We discussed the molecular regulations of fetal HSC expansion in mouse and zebrafish. It is also unknown how HSCs from the fetal liver mobilize, circulate, and reside into the fetal bone marrow niche. We reviewed how extrinsic and intrinsic factors regulate mobilization of fetal liver HSCs into the fetal bone marrow, which provides tools to improve HSC engraftment efficiency during HSC transplantation. Understanding the regulation of fetal liver HSC mobilization into the fetal bone marrow will help us to design proper clinical therapeutic protocol for disease treatment like leukemia during pregnancy. We prospect that fetal cells, including hepatocytes and endothelial and hematopoietic cells, might regulate fetal liver HSC expansion. Components from vascular endothelial cells and bones might also modulate the lodging of fetal liver HSCs into the bone marrow. The current review holds great potential to deeply understand the molecular regulations of HSCs in the fetal liver and bone marrow in mammals, which will be helpful to efficiently expand HSCs in vitro.