The impact of parathyroid hormone treated mesenchymal stem cells on ex-vivo expansion of cord blood hematopoietic stem cells

Ex-vivo expansion of cord blood hematopoietic stem cells (CB-HSCs) may play a pivotal role in the process of hematopoietic stem cell transplantation (HSCT). Here, we investigated the expansion of CB-HSCs and hematopoietic precursor cells (HPCs) on a mesenchymal feeder layer treated with Parathyroid hormone (PTH) and compared them with the untreated feeder layer. Cord blood mesenchymal and hematopoietic stem cells were used in four culture conditions in order to assess the ability of PTH to maintain HSCs self-renewability: 1) Coculture with UC-MSCs treated feeder layer (CO + PTH), 2) Co-culture with untreated UC-MSCs feeder layer (COPTH), 3) Co-culture with cytokine cocktail and PTH without feeder layer (Cyto+PTH), 4) Co-culture with cytokine cocktail but without PTH and feeder layer (Cyto-PTH). After expansion, total nucleated cells (TNC) and CD34+ cells were quantified. In addition, colony-forming unit (CFU) assay and Long-Term Culture Initiating Cell (LTC-IC) were performed. Finally, expression of HES1 gene was assessed. In CO + PTH group HES1 gene, which is responsible for self-maintenance and self-renewal of CB-HSCs was over-expressed. Importantly, PTH treated cells could maintain both CFU and LTC-IC in CO + PTH group which reflects the impact of PTH treatment on UC-HSC expansion. Our study suggests that UC-MSCs feeder layer treated with PTH is able to expand CB-HSCs, which is critical for HSCT in adult patients.