IN-VITRO EXPRESSION OF OSTEOBLASTIC MARKERS IN CELLS ISOLATED FROM NORMAL FETAL AND POSTNATAL HUMAN BONE AND FROM BONE OF PATIENTS WITH OSTEOGENESIS IMPERFECTA

We studied the expression of osteoblastic markers in cultured cells is olated from the bone of 15 patients with different clinical forms of o steogenesis imperfecta (OI) and of seven fetal and postnatal controls. Cultured bone cells of ten OI patients produced abnormal collagen typ e I. Similar to controls, OI bone cells produced predominantly collage n type I with traces of collagen types III and V. The 1,25(OH)2 vitami n D3-stimulated synthesis of osteocalcin, a specific osteoblastic mark er protein, was similar in OI bone cells and age-matched controls. Bon e cells from fetal controls and from patients with the perinatal letha l OI type II produced less osteocalcin than bone cells from postnatal controls and surviving OI patients. OI bone cells responded to parathy roid hormone (PTH) by increased production of cAMP similar to controls . Bone cells from fetal controls and from OI type II donors showed a d ecreased response to PTH. Activity of the bone-liver-kidney isoenzyme alkaline phosphatase (AP) was detected in all control and OI bone cell s. The expression of all osteoblastic markers was similar in bone cell s producing abnormal collagen type I. These observations show that OI bone cells in vitro express a pattern of osteoblastic markers similar to age-matched control bone cells indicating that osteoblastic differe ntiation is not altered by the underlying defects of collagen type I m etabolism in OI bone cells. (C) 1993 Wiley-Liss, Inc.