IN-VITRO CULTURE CHARACTERISTICS OF YOUNG AND OLD RAT MESENCHYMAL STEM CELLS

Mesenchymal stem cells are a small number of undifferentiated cells located in various tissues of the body. They have the ability to self-renew and differentiate into lineages of mesenchymal origin. They serve as most promising candidates for various regenerative medicine and tissue engineering applications. Their use in various clinical applications depend on their proliferative capacity to expand cell population. One of the key challenge to expansion is decline in proliferation and differentiation capacity of cells isolated from older individuals. In the present study, we have compared cellular characteristics of bone marrow-derived mesenchymal stem cells isolated from young (4 – 6 weeks age) and old (60-64 weeks age) rats. The two rat groups were compared for proliferation kinetics, differentiation potential and senescence markers SA- βgal, reactive oxygen species (ROS), as well as expression ofP16^INK4A, P21 and telomerase genes. A significant decrease in frequency, population doubling time, and cell yield associated with increase in age were observed. A decline in differentiation potential for osteogenic and chondrogenic lineages, and an enhancement in adipogenic lineage correlating with increase in age were noted. A significant proportion of old MSCs was SA β- galactosidase positive and had enhanced levels of ROS. The gene expression studies showed an up-regulation of senescence specific p16 ^INK4a, p21 genes and down-regulation of telomerase gene in aged cells. Our findings determine the culture characteristics of old and senescent MSCs. It may be of value in developing strategies for retrieval of optimum functioning cells among the population undergoing cellular senescence.