Objective   To study the effect of recombinant human parathyroid hormone 1-34 (rhPTH 1-34) intermittent treatment on proliferation of bone marrow stromal cells (BMSC) and their differentiation to osteoblasts as well as its mechanism underlying bone formation.    Methods   BMSC

isolated from C3H male mice at the age of 6-8 weeks

were subcultured and treated with 10 nmol/L rhPTH 1-34 intermittently or with vehicle. Proliferation of BMSC was detected by MTT assay. BMSC were stained with alkaline phophatase (ALP) and ALP activity was assayed on days 3

6 and 9 after they were differentiated to osteoblasts.Expressions of core binding factor α 1 (Cbfα1)

osteocalcin(OC) and osteopontin (OP) were detected by RT-PCR. Erk1/2 and P38 signals were detected by Western blot analysis.    Results   rhPTH 1-34 intermittent treatment promoted the proliferation of BMSC

increased the ALP activity more significantly in treatment group than in control group on day 9 after BMSC were differentiated to osteoblasts (0.625±0.049 vs 0.543±0.038

P0.05)

and the expression levels of osteogenic markers including Cbfα1

OC and OP for 186.6%

210.5%

and 5.5%

respectively (P0.05). The p-Erk1/2 and p-P38 signals were activated after rhPTH1-34 treatment.    Conclusion   rhPTH 1-34 intermittent treatment can increase the proliferation of BMSC

differentiation of BMSC to osteoblasts

and the number and activity of osteoblasts by activating the p-Erk1/2 and p-P38 signals.