Inhibition of Pim1 expression and activity impairs the proliferation of rat bone marrow mesenchymal stem cells

Abstract

Bone marrow mesenchymal stem cell (BMMSC) is one of the ideal seed cells in stem cell‐based regenerative medicine such as the myocardial infarction repairing; however, most of the infused BMMSCs would expire within 48h post cell transplantation. To further explore the mechanism involved in regulating the life span of BMMSC itself would be beneficial to understand the stem cell‐based regenerative medicine. Pim1 is one of the serine/threonine kinases involved in cell growth, however, little is known about the role of Pim1 in the proliferation of BMMSC. Here, Immunoblot and quantitative RT‐PCR revealed that Pim1 was decreased in SD rat BMMSCs induced by TGF¦Â1 (5 ng/ml) for 7 days while compared with the cells in the undifferentiated status. Treatment the cells with Pim1 inhibitor, quercetagetin (5.5 ¦ÌM), led to Pim1 changes in its activity but not expression; Transduction the cells with Pim1 shRNA resulted in obvious decrease of Pim1 expression and activity. Treatment with both the quercetagetin and Pim1 shRNA led to significant decrease in cell viability and cell numbers in day 7, and the proportion of G0/G1 in cell cycles also increased after such treatment for 7 days. Thus, our results indicate that the maintenance of Pim1 expression in rat BMMSC, though in a low level, is crucial for cell proliferation. Our results support the rational that Pim1 may be as a potential molecular target in stem cell‐based regenerative medicine.