Response of young and aged Mesenchymal Stem Cells to Dexamethasone

To explore the molecular events that underline skeletal physiology during aging we catalogued the profile of gene expression in ex vivo cultured MSCs derived from 3 and 15 month old rats and challenged with dexamethasone (Dex). RNA retrieved from these cells was analyzed using Affymetrix Gene Chips to compare the effect of Dex on gene expression. Keywords: age effect, treatment Mesenchymal Stem Cells were collected in the following manner: the bone marrow cells were flushed from the long bones, collected and prepared for single cells suspension. Cell pooled from six rats in each group were cultured in 75 cm2 flasks (Falcon, USA) containing 20 ml of growth medium, Dulbecco’s Modified Essential Medium (DMEM) containing 10% heat-inactivated fetal calf serum (FCS). Under these conditions, the hematopoietic cells died and the cultures finally remained only with cells forming the adherent stromal fibroblast-like layer. Cells were plated and after one week of culturing were trypsinized, single cell suspensions were re-cultured for 7 days and were grown in absence or presence of 10-8 M Dexamethasone (Dex). On day 14 cells were harvested for RNA extraction. The groups included: young (3 month) untreated females, young (3 month) untreated males, young treated (Dex) females, old (15 month) untreated rats, old treated (Dex) rats. Total RNAs were extracted from the four experimental groups using the TRIzol and cRNA prepared according to Affymetrix protocols. Gene expression was measured by hybridization to Affymetrix RAE230A Gene Chip DNA microarrays .