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Abstract
Mesenchymal stem cells represent a multipotent adult stem cell population that is able to differentiate into different mesodermal, endodermal and ectodermal lineages. Human umbilical cord blood MSCs cells are good substitutes for bone marrow MSCs due to safe non-invasive sampling and the immaturity of newborn cells compared with adult cells. Furthermore, UCB provides no ethical problems for basic studies and clinical applications.In vitro culture-expansion of MSCs is mandatory to get desired cell number for therapeutic purpose. Replicative senescence in vitro after a certain number of cell divisions may dramatically affect their plasticity and therapeutic utility.The aim of this work was to study the effect of replicative senescence on umbilical cord mesenchymal stem cells mainly on neural differentiation power at different passages of in vitro culture.The present study was conducted at Clinical Pathology, Obstetric and Gynecology Departments- Menuofyia University and Immunology Research Lab- Clinical Pathology Department - Ain Shams University during the period from January 2009 to September 2010 and it included 20 umbilical cord blood samples collected from vaginal deliveries at Menuofyia University hospital.We successfully isolated UCB-MSCs with isolation success rate of 70%, identified by CD29 expression and PAS cytochemical analysis. Neural differentiation and senescence associated β-galactosidase stain were performed at both 1st passage (day 14) and 2nd passage (day 21). Senescence associated β-galactosidase stain was also done at day 28 of culture.UCB-MSCs have the ability to differentiate into neuronal phenotype; however the differentiation power decreased by culture time from 1st to 2nd passage, which corresponded to the appearance of senescence associated β-galactosidase stain at 2nd passage and increased intensity of staining with marked morphological changes in MSCs at day 28.