Calcified Tissue International

, Volume 67, Issue 3, pp 241–246

Parathyroid Hormone Modulates the Response of Osteoblast-Like Cells to Mechanical Stimulation

  • K. D.  Ryder
  • R. L.  Duncan
Article

DOI: 10.1007/s002230001115

Cite this article as:
Ryder, K. & Duncan, R. Calcif Tissue Int (2000) 67: 241. doi:10.1007/s002230001115
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Abstract

Mechanical loading stimulates many responses in bone and osteoblasts associated with osteogenesis. Since loading and parathyroid hormone (PTH) activate similar signaling pathways in osteoblasts, we postulate that PTH can potentiate the effects of mechanical stimulation. Using an in vitro four-point bending device, we found that expression of COX-2, the inducible isoform of cyclooxygenase, was dependent on fluid forces generated across the culture plate, but not physiologic levels of strain in MC3T3-E1 osteoblast-like cells. Addition of 50 nM PTH during loading increased COX-2 expression at both subthreshold and threshold levels of fluid forces compared with either stimuli alone. We also demonstrated that application of fluid shear to MC3T3-E1 cells induced a rapid increase in [Ca2+]i. Although PTH did not significantly change [Ca2+]i levels, flow and PTH did produce a significantly greater [Ca2+]i response and increased the number of responding cells than is found in fluid shear alone. The [Ca2+]i response to these stimuli was significantly decreased when the mechanosensitive channel inhibitor, gadolinium, was present. These studies indicate that PTH increases the cellular responses of osteoblasts to mechanical loading. Furthermore, this response may be mediated by alterations in [Ca2+]i by modulating the mechanosensitive channel.

Key words: Osteoblasts — PTH — Prostaglandin — COX-2 — Mechanical loading.

Copyright information

© Springer-Verlag New York 2000

Authors and Affiliations

  • K. D.  Ryder
    • 1
  • R. L.  Duncan
    • 2
  1. 1.Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis, Indiana 46202, USAUS
  2. 2.Department of Orthopaedic Surgery, Indiana University School of Medicine, 541 Clinical Dr., Rm 600, Indianapolis, Indiana 46202-5111, USAUS