The research program involves investigation of the regulation of endochondral ossification, the formation of bone through mineralization of cartilage. This process is essential to bone formation and development in children, and is a fundamental element of fracture healing. Cartilage mineralization also occurs pathologically in degenerative arthritis and in heterotopic bone formation after surgery or trauma ma. Endochondral ossification is under control of systemic hormones such as parathyroid hormone, vitamin D, and growth hormone, as well as regulatory molecules synthesized by chondrocytes which have autocrine or paracrine effects. The complex interactions of these growth factors regulate the orderly sequence of biochemical events associated with chondrocyte proliferation, hypertrophy, and matrix mineralization. Growth plate chondrocytes are isolated in specific states of maturation using counter-current centrifugal elutriation, and the progression of biochemical and cellular characteristics leading to mineralization can be studied. Among the more important growth factors under investigation are the transforming growth factor-betas, acidic and basic fibroblast growth factor, and the insulin-like growth factors. These factors have major effects on chondrocyte proliferation and differentiation, and are produced by the cells as autocrine regulators. Studies of growth factor effects, message regulation, synthesis and secretion, and receptor expression in chondrocytes in various stages of maturation are currently underway in our laboratory, and should provide insight into the control of mineralization, as well as some means of manipulating this process.

The figure demonstrates the levels of TGF-b synthesized by growth plate chondrocytes m different maturational stages (F1 -- smallest resting cells; F5 -- largest hypertrophic cells), indicating increasing TGF-b synthesis as the cells hypertrophy and prepare for matrix mineralization.

Research Grants, Principal Investigator

Current Active Support:
4/97-3/01	NIH Grant RO1 CA71603: Growth plate radiation response: mechanism and therapy, $686,591
12/97-11/01	NIH Grant RO1 AR40325: Autocrine and ionic regulation of chondrocyte phenotype, $802,998

Rosier, RN, D.G.Hicks, L.A.Teot, J.E.Puzas, R.J.O'Keefe: Mechanisms of metastasis, Am. J. Hospice Care (in press).

Reynolds, SD, Zuscik, MJ, Gunter, TE, O'Keefe, RJ, Puzas, JE, Rosier, RN, Reynolds, PR: PTH and PTHrP effects on growth plate chondrocytes: an overview. Cells and Materials, (in press).

Blaine, TA, Pollice, PF, Rosier, RN, Reynolds, PR, Puzas, JE, O'Keefe, RJ: Modulation of cytokine production in titanium stimulated human monocytes by pharmacological agents: the role of cAMP mediated signalling mechanisms. J Bone Joint Surg, (in press).

Rosier, RN, O'Keefe, RJ, Teot, LA, Fox, EJ, Nester, TA, Puzas, JE, Reynolds, PR, Hicks, DG: P-glycoprotein in cartilaginous tumors, J Surg Oncol, 65:95-105, 1997.

O'Keefe, RJ, Teot, LA, Singh, D, Puzas, JE, Rosier, RN, Hicks, DG: Osteoclasts condtitutively express regulators of bone resorption: an immunohistochemical and in situ hybridization study. Lab Investigation, 76(4):457-465, 1997.

Zuscik, MJ, Gunter, TE, Puzas, JE, Rosier, RN: Characterization of voltage-sensitive calcium channels in growth plate chondrocytes. Biochem Biophys Res Comm, 234:432-438, 1997.

O'Keefe, RJ, Loveys, LS, Hicks, DG, Reynolds, PR, Crabb, ID, Puzas, JE, Rosier, RN: Differential regulation of type-II and type-X collagen synthesis by parathyroid hormone-related protein in chick growth-plate chondrocytes. J Ortho Res, 15(2):162-174, 1997.

Blaine, TA, Rosier, RN, Looney, RJ, Reynolds, PR, Reynolds, SD, Puzas, JE, O'Keefe, RJ: Increased levels of tumor necrosis factor-a and interleukin-6 protein and messenger RNA in human peripheral blood monocytes due to titanium particles. J Bone Joint Surg 78A:1181-1192, 1996.