Calvarial and limb bone cells in organ and monolayer culture do not show the same early responses to dynamic mechanical strain
Open Access
- 1 August 1995
- journal article
- research article
- Published by Oxford University Press (OUP) in Journal of Bone and Mineral Research
- Vol. 10 (8), 1225-1232
- https://doi.org/10.1002/jbmr.5650100813
Abstract
Responses to mechanical strain in calvaria and limb bone organ cultures were compared by measuring cellular glucose 6-phosphate dehydrogenase (G6PD) activity in situ and prostaglandin release. Normal functional strains were recorded in the ulnae (1000 μϵ) and calvarium (30 μϵ) in vivo in 110 g rats. Organ cultures of ulnae and calvaria from similar animals were loaded to produce dynamic strains (600 cycles, 1 Hz) of 1000 μϵ in the ulna, and 100 or 1000 μϵ in calvaria. In ulnae, both PGE2 and PGI2 were released and resident osteocytes and osteoblasts showed increased G6PD activity. Neither response was seen in calvaria. However, exogenous PGI2 (10−5−10−9 M) stimulated G6PD activity in osteocytes and osteoblasts in organ cultures of both calvaria and ulnae. In ulnar cells the response was linear, in calvarial cells it was biphasic with maximum activity at 10−7 M. Osteoblasts derived from ulnae and cultured on plastic plates subjected to dynamic strain (600 cycles, 1 Hz, 4000 μϵ) showed increased G6PD activity. There was no such response in similarly treated calvarial-derived cells. Calvarial bone cells differ from those of the ulna in that they do not respond to physiological strains in their locality with increased prostanoid release or G6PD activity either in situ or when seeded onto dynamically strained plastic plates. Cells from both sites in organ culture show increased G6PD activity in response to exogenous PGI2, but their dose: Responses differ in shape. These differences may reflect the extent to which functional loading influences bone architecture in these two sites.Keywords
Funding Information
- Wellcome Trust and the MRC
This publication has 26 references indexed in Scilit:
- Mechanical stimulation of rat tail vertebrae induces indomethacin-sensitive expression of insulin-like growth factor-1 mRNA in osteocytesBone, 1995
- Estrogen enhances the stimulation of bone collagen synthesis by loading and exogenous prostacyclin, but not prostaglandin E2, in organ cultures of rat ulnaeJournal of Bone and Mineral Research, 1994
- Exogenous prostacyclin, but not prostaglandin E2, produces similar responses in both G6PD activity and RNA production as mechanical loading, and increases IGF-II release, in adult cancellous bone in cultureCalcified Tissue International, 1993
- Systematic assessment of bone resorption, collagen synthesis, and calcification in chick embryonic calvaria in vitro: Effects of prostaglandin E2Bone, 1993
- Early strain-related changes in cultured embryonic chick tibiotarsi parallel those associated with adaptive modeling in vivoJournal of Bone and Mineral Research, 1993
- Osteoporosis after spinal cord injuryJournal of Orthopaedic Research, 1992
- The inositol phosphate pathway as a mediator in the proliferative response of rat calvarial bone cells to cyclical biaxial mechanical strainJournal of Orthopaedic Research, 1992
- Early strain-related changes in enzyme activity in osteocytes following bone loading in vivoJournal of Bone and Mineral Research, 1989
- Regulation of bone mass by mechanical strain magnitudeCalcified Tissue International, 1985
- Mechanically adaptive bone remodellingJournal of Biomechanics, 1982