عواقب ژنتیکی پاساژ های متوالی در سلول های بنیادی مزانشیمال انسانی

Introduction & Objective: Stem cells are determined by their unique features. One of them is high proliferation ability and the other is potency of differentiation to various tissues. The results of new works in various countries around the world including Iran show the growing momentum of works on stem cell therapy. Working with stem cells from different origins including the cells originated from fetal and adult origin (such as bone marrow, dental root, cord , etc) is in progress. The goal of this work was to clear the maintenance and stability of genetic materials of human mesenchymal stem cells through consecutive subcultures in our lab conditions in Hamadan Uni-versity of Medical Sciences. Materials & Methods: In an experimental work, human umbilical cord was used as a rich source of stem cells. Isolated stem cells, after proliferation phase, increased and filled the bottom of the flasks in consecutive passages. After some successive consecutive subcultures, stem cells aged and this may cause damages to genetic material that is evaluated in primary passages (passages number 1-5), middle passages (passages number 8-12) and late passages (passages number 15-18) by the single cell gel electrophoresis assay (comet assay). Also their karyotypes were ex-amined Solid technique and G-banding staining for chromosome analysis in the stem cells were employed. Several microscopic slides from each passage were prepared. Then 20 cells were ran-domly selected from the slides related to each group. In all selected cells, damages were exam-ined and their degree of damages were scored based on the standard patterns, from 0 to 4. The averages were compared by Kruskal–Wallis test in different groups. Results: Average scores related to three studied cell groups, primary, middle and late passages, were 0.4, 2.8 and 3.6, respectively. Prepared karyotypes from the cells belonging to passages 1-5 were normal but in the aged passages they were abnormal numerically and structurally. Our results showed that the aging phenomenon and its consequences such as DNA damages should be considered in the work with consecutive passages of stem cells. Conclusion: We concluded that in our laboratory conditions, the stem cells taken from human umbilical cord blood are only usable for research purposes in early passages (below passage five).We recommend using passages more than five only for educational purposes in our labora-tory and it is better to do the same work in such research centers.