ADHESION, GROWTH AND DIFFERENTIATION OF HUMAN BONE-MARROW STROMAL CELLS ON NONPOROUS CALCIUM-CARBONATE AND PLASTIC SUBSTRATA - EFFECTS OF DEXAMETHASONE AND 1,25DIHYDROXYVITAMIN D3

Bone marrow contains stromal fibroblastic stem cells which have the po tential to differentiate into bone-forming cells. Therefore addition o f bone marrow to porous bone substitutes such as coral or coralline hy droxyapatite may be expected to enhance bone ingrowth into these impla nts. This study was designed to evaluate the possibility of growing hu man bone marrow stromal fibroblastic cells (HBMC) on a calcium carbona te substrate. For this purpose, HBMC were cultured for 20 days on plas tic or calcium carbonate and cell adhesion, growth, and differentiatio n were studied. It was concluded that calcium carbonate is a highly co mpatible material for the growth of HBMC. Cells were capable of adhesi on within 30 min and were spread within 24 h on this material. However , plating efficiency was decreased in comparison to plastic. Populatio n doubling times (PDT) showed that they were similar when the cells we re grown on plastic or calcium carbonate as substratum (PDT = 4, 5.5 d ays). Early protein synthesis included collagen I, collagen III, osteo pontin and bone sialoprotein. To induce differentiation of HBMC on pla stic and calcium carbonate the influence of dexamethasone (Dex) and 1, 25dihydroxyvitamin D3 (1,25(OH)(2)D-3) o alkaline phosphatase (ALP) ex pression was studied. Basic ALP activity was similar when cells were g rown on plastic or calcium carbonate. However, Dex and 1,25(OH)(2)D-3 increased ALP activity of HBMC which could be driven best towards oste ogenesis in the presence of Dex and 1,25(OH)(2)D-3.