Effect of a continuously applied compressive pressure on mouse osteoblast‐like cells (MC3T3‐E1) in vitro

Abstract

Bone metabolism is often affected by a variety of mechanical forces, but the cytological basis of their action is not known. In this study, we examined the effect of a continuously applied compressive pressure (CCP) on the growth and differentiation of clonal mouse osteoblast-like cells (MC3T3-E1) cultured in a specifically devised culture chamber. The gas phase of the chamber was maintained at a pressure of 2 atmospheres (atm) above ambient (3 atm total, 3.1 kg/cm2; 3.0 x 10(5) Pa) by continuously infusing a compressed mixed gas (O2: N2:CO2 = 7.0%:91.3%:1.7%). The pO2, pCO2, and pH in the culture medium at 37 degrees C under 3 atm were maintained at the same levels as those under 1 atm. MC3T3-E1 cells were cultured in alpha-minimal essential medium containing 10% fetal bovine serum under either 3 atm in the CCP culture chamber or 1 atm in an ordinary CO2 incubator. Alkaline phosphatase activity, a marker of osteoblasts, was greatly suppressed by the CCP treatment. The inhibition of alkaline phosphatase activity was rapidly restored when the cells were transferred to an ordinary CO2 incubator under 1 atm, indicating that the inhibition of alkaline phosphatase activity by CCP is reversible. Cell growth was not altered under CCP. The CCP treatment greatly increased the production and secretion of prostaglandin E2 (PGE2). Adding either conditioned medium from the CCP culture or exogenous PGE2 to the control culture under 1 atm suppressed alkaline phosphatase activity dose-dependently. The CCP treatment also suppressed collagen synthesis and calcification. These results suggest that CCP causes the cells to produce and secrete PGE2, which, in turn, inhibits differentiation of osteoblasts and the concomitant calcification.

Osteoblastic differentiation of periosteum‐derived cells is promoted by the physical contact with the bone matrix in vivo

“…3), whereas bone formation was not observed under the filter. Previous study has reported that the continuously applied compressive pressure inhibits osteoblastic differentiation in vitro (Ozawa et al, 1990). Therefore, we assume that the continuously applied pressure from the filter to the bone surface might downregulate osteoblastic differentiation of cells under the membrane filter, whereas much less pressure under the pin hole might be favorable to the osteoblastic differentiation.…”

Molecular pathways mediating mechanical signaling in bone

“…Continuous hydrostatic pressure at physiologic levels decreased osteoclast formation in marrow cultures (Rubin et al, 1997), and increased production of PGE 2 and decreased collagen synthesis from osteoblast-like cells (Ozawa et al, 1990). Application of intermittent compressive force to fetal mouse calvariae was shown to increase bone formation and decrease bone resorption (Klein-Nulend et al, 1987).…”

Pathogenesis of Degenerative Joint Disease in the Human Temporomandibular Joint

“…The restoration of compressive loads to articular cartilage stimulates synthesis of GAGs and increases the thickness of cartilage (De Witt et al, 1984;Palmoski and Brandt, 1984;Slowman and Brandt, 1986;Kiviranta et al, 1987). The application of mechanical loads to bone has been shown to: (i) increase the percentage of cells synthesizing DNA (Hasegawa et al, 1985), (ii) alter the types of protein synthesized (Hasegawa et al, 1985), (iii) alter the rate of bone formation and resorption (Vargas and Raisz, 1990), (iv) alter calcification (Ozawa et al, 1990), and (v) inhibit osteoblast differentiation (Imamura et al, 1990;Ozawa et al, 1990;Vargas and Raisz, 1990). Both the condyle and the temporal bone undergo degenerative changes if the disk is deranged, perforated, or removed (Scapino, 1983;Ericsson and Westesson, 1985).…”