Abstract
Background and Objectives
The low number of hematopoietic stem cells (HSCs) in each unit of UCB is a limitation for clinical application of this source of HSCs. Ex vivo expansion of HSCs to obtain a sufficient number for therapeutic purposes is necessary. The sympathetic nervous system (SNS) and neurotransmitters regulate HSCs self-renewality, proliferation and differentiation in the bone marrow. The aim of this study was to evaluate the proliferative effect of NPY on the CB-HSCs in ex vivo condition.   
 
Materials and Methods
After isolation of HSCs, the comparison of HSCs Ex vivo expansion using 1 µM NPY and cytokine as test group with cytokine as control group was performed . TNC number and CD34⁺ cell number were calculated on day 7. Colony formation assay was performed in methylcelloluse medium. LTC-IC assay was performed to investigate colonization potential of expanded cells in long time culture.
 
Results
Ex vivo expansion of CB-HSCs after 7 days resulted in significant increase in the number of total nucleated cells and CD34⁺ cells in NPY-treated groups in comparison to control group. The formation of different cell colonies identified as erythrocytic, granulocytic and mix colonies in CFU assay reflect the differentiation potential of expanded CD34 cells. Treated group with NPY also retained their ability to formate colonies in long term culture.
 
Conclusions 
Our study demonstrated that Neuropeptide Y can successfully support expansion of CD34⁺ hematopoietic stem cells while retaining their potential of  being differentiated into various cell lineages after 7-day culture period with cytokine supplementation.