RESUMO
Stem cells are considered as ideal model for assessment of environmental toxins on proliferation, multipotency and differentiation. The aim of this study was to investigate the effect of lead as harmaful environmental pollutant on proliferation and neural differentiation of murine bone marrow-MSCs. In this experimental study, MSC cells were exposed to different concentrations of lead [0 to 100 micro M] for 24h, and the level of cell proliferation was determined by 3-[4, 5-dimethyl-2-thiazolyl]-2, 5-dipheny-2H-tetrazolium bromide [MTT] reduction assay. In addition, DNA fragmentation was evaluated with comet assay at a single cell level. To induce the neural phenotype, MSCs were cultured for 2 days in the presence of 50 micro Pb[2+] for 48 h. At the end of this period, the medium was replaced by fresh medium supplemented with 1 mM beta-ME for 24 hr and then fresh medium supplemented with 7 mM beta-ME for 4 hours respectively. The expression of neural marker such as nestin, MAP2, and tau was assessed by immunocytochemistry, while the expression of neuronal specific genes such as Neur-1, Nestin, and beta-tubulin III was determined by RT-PCR analysis. Exposure to lead reduced the level of cell proliferation in a dose-dependent manner. The comet assay of cells exposed to lead showed varying degrees of DNA damaged. Change in cell morphology was observed 1 to 4 hr post neural exposure. The percentage of the MAP2 positive cells was reduced significantly at greater than 40 micro M lead concentration. This observation was further verified by assessment of the expression of neural markers. This study clearly indicated lead is highly cytotoxic to MSCs and these cells appear to be an excellent choice for establishment of guidelines for environmental hazards and drugs on cell proliferation and differentiation