Abstract
Background
CD140a /PDGFRα + human oligodendrocyte precursor cells (OPCs) are a lineage of OPCs with proven potential for use in cell therapy against demyelinating diseases. However, little is known about the contribution of human endothelial cells in the biology of PDGFRα + human OPCs in the stem cell niche.
Methods
Transwell co-culture technique with human umbilical vein endothelial cells (HUVECs) was adopted under proliferative or differentiating conditions to understand the role of endothelial cells in these processes within OPCs. Proliferation was followed by measuring OPC sphere size, count, sphere dissociation followed by cell count and 3H-methyl thymidine incorporation. Differentiation was followed by immunocytochemistry. Taqman gene expression assay for selective soluble factors was performed for the two co-culture partner cells to determine the expression of these factors on the biology of the OPCs in presence of the endothelial cells.
Results
In co-culture with HUVECs, under proliferative conditions, OPCs show increased proliferation and sphere formation. In contrast, under differentiating conditions, OPCs show increased differentiation to astrocytes, with a concomitant decrease in differentiation to oligodendrocytes, compared to no co-culture controls. Transcript assay for selected humoral factors in the OPCs and HUVECs revealed bone morphogenic proteins (BMPs), endothelin1, growth arrest specific 6 (GAS6), and interleukin 6 (IL6) to be in higher abundance in HUVECs than OPCs. Whereas the OPCs show higher expression for pleiotrophin (PTN), fibroblast growth factor 9 (FGF9), ciliary neurotrophic factor (CNTF), and leukemia inhibitory factor (LIF) compared to the endothelial cells. Among the transcripts analyzed, BMP4 transcripts were the highest in relative abundance in the endothelial cells indicating possibilities of BMPs being the critical mediator of endothelial cell-mediated effects. In agreement to this, Noggin effectively attenuated HUVEC mediated astrocytic differentiation of CD140a /PDGFRα + fetal human OPCs.
Conclusion
Based on the above results, the study concludes that human endothelial cells can significantly alter the biology of PDGFαR + fetal human OPCs mediated by humoral factors to induce increased proliferation and BMP mediated astrocytic differentiation. It can be secondarily inferred from these conclusions that using pharmacological inhibitors of BMP signaling along with the PDGFRα + fetal OPC transplantation may make these cells more effective in remyelination therapy.
Extracellular Vesicles from Vascular Endothelial Cells Promote Survival, Proliferation and Motility of Oligodendrocyte Precursor Cells
