en Medical Biology Medical Biology مقاله پژوهشی Original Research Article <span style="font-size:11pt"><span style="line-height:150%"><span style="font-family:Calibri,sans-serif"><b><span style="font-size:12.0pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times="">Background and objective: </span></span></span></b><span style="font-size:12.0pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times="">Exosomes derived from umbilical cord blood mesenchymal stem cells (UCB-MSCs) may enhance hematopoietic stem cells (HSCs) proliferation while preserving their undifferentiated state. This study evaluates the potential of UCB-MSC-derived exosomes as a cell-free strategy to expand HSCs, addressing the limitation of low HSC numbers for hematological disorder therapies.</span></span></span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><span style="font-family:Calibri,sans-serif"><b><span style="font-size:12.0pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times="">Methods</span></span></span></b><span style="font-size:12.0pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times="">: In this in vitro study, MSC-derived exosomes (MSC-EXOs) were isolated and characterized. Subsequently, three umbilical cord blood samples were collected, and CD34+ HSCs were purified using magnetic-activated cell sorting (MACS). To identify the optimal exosome concentration, CD34+ cells were cultured with MSC-EXOs at four different concentrations (1, 5, 10, and 100 ng/mL). Gene expression levels of CXCR4, VLA-4, VLA-5, hTERT, and HOXA9 were assessed using quantitative RT-PCR, while colony-forming cell (CFC) assays were performed to evaluate the clonogenic potential of HSCs.</span></span></span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><span style="font-family:Calibri,sans-serif"><b><span style="font-size:12.0pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times=""><span style="color:black"><span style="letter-spacing:.3pt">Results</span></span></span></span></span></b><span style="font-size:12.0pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times=""><span style="color:black"><span style="letter-spacing:.3pt">: After 7 days of co-culture, an increase in mononuclear cells (MNCs) was observed across all groups. Notably, the expression of the CD34 marker was significantly highest in Group III (71%) and Group IV (approximately 48%), exceeding levels seen in the other groups. Gene expression analysis revealed a significant upregulation of target genes in Group IV. Consistent with these findings, the CFC assay showed that Group IV had a significantly higher colonization rate than the other experimental conditions.</span></span></span></span></span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><span style="font-family:Calibri,sans-serif"><b><span style="font-size:12.0pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times=""><span style="color:black"><span style="letter-spacing:.3pt">Conclusion</span></span></span></span></span></b><span style="font-size:12.0pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times=""><span style="color:black"><span style="letter-spacing:.3pt">: The results demonstrate that MSC-derived exosomes can effectively mimic the supportive functions of their parent cells in vitro, thereby significantly enhancing HSC proliferation.</span></span></span></span></span></span></span></span><br> &nbsp; Differentiation, Extracellular vesicle, Hematopoietic stem cell, Mesenchymal stem cell, Proliferation 37 37 http://journal.zums.ac.ir/browse.php?a_code=A-10-7315-1&slc_lang=en&sid=1 Aama Javadi Rad asmajavadi1993@gmail.com 5200319475328460090332 5200319475328460090332 No Department of Hematology and Blood Transfusion, School of Allied Medical Sciences, Tehran University of Medical Sciences, Tehran, Iran. Mohammad Khani-Eshratabdi Lskhani@yahoo.com 5200319475328460090333 5200319475328460090333 No Department of Medical Laboratory Sciences, Kashmar School of Nursing, Mashhad University of Medical sciences (MUMS), Mashhad, Iran. Morteza Zarrabi m.zarrabi@rsct.it 5200319475328460090334 5200319475328460090334 No Department of Regenerative Medicine, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran. Narjes Seddighi narjes.seddighi80@gmail.com 5200319475328460090335 5200319475328460090335 No Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran Seyed Hadi Mousavi hmousavi@tums.ac.ir 5200319475328460090336 5200319475328460090336 Yes 6. Department of Hematology and Blood Transfusion, School of Allied Medical Sciences, Tehran University of Medical Sciences, Tehran, Iran.