The Biochemical Pathway Mediating the Proliferative Response of Bone Cells to a Mechanical Stimulus

• Published in: Journal of bone and joint surgery. American volume 1996-09, Vol.78 (9), p.1337-47
• Main Authors: BRIGHTON, CARL T, FISHER, J. RUSH S, LEVINE, STUART E, CORSETTI, JOHN R, REILLY, THOMAS, LANDSMAN, ADAM S, WILLIAMS, JOHN L, THIBAULT, LAWRENCE E
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Bone and Bones - cytology; Bone and Bones - drug effects; Bone and Bones - metabolism; Bone and Bones - physiology; Calcium - analysis; Calcium - metabolism; Calmodulin - analysis; Calmodulin - antagonists & inhibitors; Calmodulin - biosynthesis; Cell Division - drug effects; Culture Techniques; Cyclooxygenase Inhibitors - administration & dosage; Cyclooxygenase Inhibitors - pharmacology; Cytoskeleton - drug effects; Cytoskeleton - metabolism; Cytosol - drug effects; Cytosol - metabolism; Dinoprostone - analysis; Dinoprostone - antagonists & inhibitors; Dinoprostone - biosynthesis; DNA - analysis; DNA - biosynthesis; Fluorescent Dyes; Fundamental and applied biological sciences. Psychology; Fura-2 - analogs & derivatives; Hydrostatic Pressure; Indomethacin - administration & dosage; Indomethacin - pharmacology; Inositol Phosphates - antagonists & inhibitors; Neomycin - pharmacology; Protein Synthesis Inhibitors - pharmacology; Rats; Signal Transduction - drug effects; Skeleton and joints; Skull; Space life sciences; Stress, Mechanical; Sulfonamides - administration & dosage; Sulfonamides - pharmacology; Thymidine - metabolism; Time Factors; Tritium; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 0021-9355; 1535-1386
• DOI: 10.2106/00004623-199609000-00007

Calvarial bone cells of rats were subjected to either a cyclic biaxial strain of 0.17 per cent (1700 microstrain) or a hydrostatic pressure of 2.5, five, or ten pounds per square inch (17.2, 34.5, or sixty-nine kilopascals). The frequency was held constant at one hertz for both types of mechanical stimulation. When cultured bone cells that had been subjected to a cyclic biaxial strain for two hours were harvested twenty-two hours later, it was found that the level of prostaglandin E2 had increased significantly (p < 0.01) as had cellular proliferation (p < 0.01), as indicated by the incorporation of [H]-thymidine. The addition to the medium of indomethacin, an inhibitor of prostaglandin synthesis, at a ten-micromolar concentration significantly inhibited (p < 0.01) the increase in prostaglandin E2 synthesis but had no effect on the strain-induced increase in cellular proliferation, as indicated by the incorporation of [H]-thymidine. Twenty-four hours after exposure to the same cyclic biaxial strain for thirty seconds, other cultured bone cells showed a significant increase in the level of cytoskeletal calmodulin (p < 0.05) and in the DNA content (p < 0.05). N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7), a calmodulin antagonist, was added to the medium at a one-micromolar concentration, which had been shown to have no effect on the increase in the DNA content of control cells; W-7 completely blocked the increase in the level of cytoskeletal calmodulin and in the DNA content in the cells that were subjected to a cyclic biaxial strain. The bone cells subjected to a hydrostatic pressure showed a dose-dependent increase in the concentration of cytosolic Ca, as measured with Fura 2-AM, a fluorescent indicator of intracellular calcium. With a pressure of ten pounds per square inch (sixty-nine kilopascals), the increase in the concentration of cytosolic Ca was nearly eight times greater than that at 2.5 pounds per square inch (17.2 kilopascals) (126 ± 15.2 compared with 16 ± 8.0 nanomolar, mean and standard deviation). The addition to the medium of neomycin, an inhibitor of the inositol phosphate cascade, at a ten-millimolar concentration completely blocked the increase in the concentration of cytosolic Ca in these cells; this concentration of neomycin had been shown to have no effect on proliferation in control bone cells. There was also a dose-dependent relationship between the duration of the stimulus and the cellular proliferation. Remarkably, one