Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 2 2 2005 06 15 36 41 M Mohyeddin Bonab Hematology-Oncology & BMT Research Center, Shariati Hospital, Tehran University of Medical Sciences, Iran K Alimoghaddam Hematology-Oncology & BMT Research Center, Shariati Hospital, Tehran University of Medical Sciences, Iran F Talebian Hematology-Oncology & BMT Research Center, Shariati Hospital, Tehran University of Medical Sciences, Iran S.H Ghaffari Hematology-Oncology & BMT Research Center, Shariati Hospital, Tehran University of Medical Sciences, Iran A Ghavamzadeh Hematology-Oncology & BMT Research Center, Shariati Hospital, Tehran University of Medical Sciences, Iran B Nikbin Hematology-Oncology & BMT Research Center, Shariati Hospital, Tehran University of Medical Sciences, Iran 2015 10 01 Mesenchyml stem cell (MSC) are receiving much attention in treatment of various diseases. The low frequency of MSCs in bone marrow (BM) necessitates their in vitro expansion prior to clinical use. We evaluated the effect of long term culture on the senescence of these cells. BM cells were taken from 11 transplant donors with mean age of 25 years. In different passages, MSC were examined for different aging indicators including: telomere length assay, differentiation ability, immunophenotyping of CD13, CD44 and CD34 antigens, determination of cumulative population dou¬blings (CPDs), and study of morphological characteristics of MSC cultures. The mean long term culture was 118 day and the mean passage number was 9. The average number of PD decreased from 7.7 to 1.2 in the 10th passage. The mean telomere length decreased from 9.19 Kbp to 8.7 kbp in the 9th passage. Differentiation potential dropped from the 6th passage on. The culture's morphological abnormalities were typical of the Hayflick model of cellular aging. We believe that MSC enter senescence almost undetectably from the moment of in vitro culturing. Si¬multaneously these cells are losing their stem cell characteristics. Therefore, it is much better to con¬sider  them for cell and gene therapy early on. https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/190 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/190/183