Treatment with hydrogen sulfide donor attenuates bone loss induced by modeled microgravity.

The present study was undertaken to explore the therapeutic potential of hydrogen sulfide (H2S) against bone loss induced by modeled microgravity. Hind-limb suspension (HLS) and rotary wall vessel bioreactor (RWVB) were applied to model microgravity in vivo and in vitro, respectively. Treatment of rats with GYY4137 (a water soluble donor of H2S, 25mg/kg/day, i.p.) attenuated HLS-induced reduction of bone mineral density in tibiae, and preserved bone structure in tibiae and mechanical strength in femurs. In HLS group, GYY4137 treatment significantly increased levels of osteocalcin in sera. Interestingly, Treatment of HLS rats with GYY4137 enhanced osteoblast surface, but had no significant effect on osteoclast surface of proximal tibiae. In MC3T3-E1 cells exposed to modeled microgravity, GYY4137 stimulated transcriptional levels of Runx2 and enhanced osteoblastic differentiation, as evidenced by increased mRNA expression and activity of alkaline phosphatase. HLS in rats led to enhanced levels of IL-6 in sera, skeletal muscle and tibiae, which could be attenuated by GYY4137 treatment. In conclusion, GYY4137 preserved bone structure in rats exposed to HLS and promoted osteoblastic differentiation in MC3T3-E1 cells under modeled microgravity.