Synergistic effect of PTH on the mechanical responses of human alveolar osteocytes

The aim of this study is to characterize the response of alveolar osteocytes to stretching and parathyroid hormone, (1-34) PTH. Osteocytes from primary human alveolar bone were used in the study. Compared to osteoblasts, osteocytes were observed to express lower levels of alkaline phosphatase mRNA and higher levels of osteocalcin mRNA. We found that the effect of PTH and stretching on osteocalcin expression is synergistic. The upregulated steady-state level of osteocalcin mRNA is further upregulated in the presence of PTH (at 1 h after the initiation of stretching). On the other hand, the downregulated level of the message is further downregulated in the presence of PTH (at 3 h after the 3-h stretching). The synergy can be either way, positive or negative, in the course of the response. From this, we presume that related mechanisms are at work between the PTH signaling pathways and the mechanotransduction pathways activated by stretching.