The peripheral benzodiazepine receptor (PBR) has been known to have many functions such as a role in cell proliferation, cell differentiation, steroidogenesis, calcium flow, cellular respiration, cellular immunity, malignancy, and apoptosis. However, the presence of PBR has not been examined in mesenchymal stem cells. In this study, we demonstrated the expression of PBR in human bone marrow stromal cells (hBMSCs) and human adipose stromal cells (hATSCs) by RT-PCR and immunocytochemistry. To determine the roles of PBR in cellular functions of human mesenchymal stem cells (hMSCs), effects of diazepam, PK11195, and Ro5-4864 were examined. Adipose differentiation of hMSCs was decreased by high concentration of PBR ligands (50 microM), whereas it was increased by low concentrations of PBR ligands (<10 microM). PBR ligands showed a biphasic effect on glycerol-3-phosphate dehydrogenase (GPDH) activity. High concentration of PBR ligands (from 25 to 75 microM) inhibited proliferation of hMSCs. However, clonazepam, which does not have an affinity to PBR, did not affect adipose differentiation and proliferation of hMSCs. The PBR ligands did not induce cell death in hMSCs. PK11195 (50 microM) and Ro5-5864 (50 microM) induced cell cycle arrest in the G(2)/M phase. These results indicate that PBR ligands play roles in adipose differentiation and proliferation of hMSCs.

SUMMARY Embryonic stem (ES) cells, which have pluripotency in differentiation,have been considered as an excellent source for cell replacement therapy of damaged tissues. Although neurotrophic factors induce neural differentiation in neural precursor cells, their actions in ES cells are not clear. This study was designated to examine the effect of brain-derived neurotrophic factor (BDNF) on neural differentiation in mouse ES cells. Undifferentiated mouse ES cells were maintained at suspension culture in the presence of leukemia inhibitory factor (LIF), and neural precursor cells were isolated from the subventricular zone (SVZ) of the 2-3 day old mice brain. Ott-4 was expressed in undifferentiated ES cells and neural precursor cells, of which expression was markedly decreased by induction of differentiation.RT-PCR analysis showed that neural differentiation of ES cells induced expression of various neural markers, and that BDNF increased their expression.Western blot analysis demonstrated that BDNF induced expression of synaptophysin, a neuronal marker, and inhibited expression of glial fibrillary acidic protein, a glial marker. Undifferentiated ES cells expressed TrkA, TrkB and TrkC, of which expressions were increased during differentiation. Neural differentiation increased their expression, and BDNF further increased them. The treatment of BDNF during differentiation decreased expression of Notchl. These results indicated that BDNF induces neural differentiation and inhibits glial differentiation in ES cells as well as neuronal precursor cells.