Suppression of osteoblast differentiation during weightlessness

It is pointed out that associated with weightlessness is a marked depression or arrest of bone formation. Although the mechanism of this effect is unknown, it probably involves a failure of osteogenic induction. The present study's objective is to determine if weightlessness alters osteoblast differentiation, as evidenced by a change in relative distribution of large to small nuclei in rat moral periodontal ligament of the maxilla. In conjunction with the U.S./USSR Biological Satellite Program, male Wistar rats were flown aboard a modified Soviet Vostok spacecraft (Cosmos 1129). The results of the study are discussed. Morphometric investigations suggest that depleted numbers of preosteoblasts may be an important factor in the inhibition of bone formation during weightlessness.