Sensitivity of osteocytes to biomechanical stress in vitro

TLDR

Bone tissue adapts to functional stress by altering structure and mass, but the cellular mechanism translating mechanical stress into bone formation and resorption remains unknown. The study aimed to determine how isolated embryonic chicken calvarial osteocytes respond to intermittent hydrostatic compression and pulsating fluid flow compared to osteoblasts and periosteal fibroblasts. The authors exposed isolated osteocytes, osteoblasts, and periosteal fibroblasts to intermittent hydrostatic compression and pulsating fluid flow in vitro to assess their mechanosensitive responses. Osteocytes released prostaglandin E2 after 1‑hour pulsating fluid flow and, to a lesser extent, after intermittent hydrostatic compression, whereas osteoblasts and periosteal fibroblasts did not; these results demonstrate that osteocytes are the most mechanosensitive bone cells and support the hypothesis that mechanical stress induces fluid flow that activates osteocytes to produce bone‑regulating factors. Published in FASEB Journal, volume 9, pages 441–445 (1995).

Abstract

It has been known for more than a century that bone tissue adapts to functional stress by changes in structure and mass. However, the mechanism by which stress is translated into cellular activities of bone formation and resorption is unknown. We studied the response of isolated osteocytes derived from embryonic chicken calvariae to intermittent hydrostatic compression as well as pulsating fluid flow, and compared their response to osteoblasts and periosteal fibroblasts. Osteocytes, but not osteoblasts or periosteal fibroblasts, reacted to 1 h pulsating fluid flow with a sustained release of prostaglandin E2. Intermittent hydrostatic compression stimulated prostaglandin production to a lesser extent: after 6 and 24 h in osteocytes and after 6 h in osteoblasts. These data provide evidence that osteocytes are the most mechanosensitive cells in bone involved in the transduction of mechanical stress into a biological response. The results support the hypothesis that stress on bone causes fluid flow in the lacunar-canalicular system, which stimulates the osteocytes to produce factors that regulate bone metabolism.—Klein-Nulend, J., van der Plas, A., Semeins, C. M., Ajubi, N. E., Frangos, J. A., Nijweide, P. J., Burger, E. H. Sensitivity of osteocytes to biomechanical stress in vitro. FASEB J. 9, 441–445 (1995)