GROWTH AND DIFFERENTIATION OF HUMAN BONE-MARROW OSTEOPROGENITORS ON NOVEL CALCIUM-PHOSPHATE CEMENTS

Materials that augment bone cell proliferation and osteogenic activity have important therapeutic implications for bone regeneration and for use in skeletal reconstruction and joint replacement. We have studied the growth and interactions of human bone marrow cells on a variety o f new cement composites in vitro. These cement materials are composed of calcium-deficient hydroxyapatites, carbonated apatite and amorphous calcium phosphate. Cell proliferation was significantly reduced and c ell differentiation increased in the presence of these cements compare d with cells cultured on tissue culture plastic. Alkaline phosphatase, one of the markers of the osteoblast phenotype, was dramatically stim ulated by 3 of the 4 cements examined between day 4 and day 10, above levels observed following culture of human osteoblasts on plastic alon e. Photomicroscopic examination demonstrated growth and close integrat ion of bone marrow cells and 3 of the composites. Longer term marrow c ultures (15 day) on the cements confirmed the stimulation of cell diff erentiation over proliferation. From these studies, enhanced osteoblas tic differentiation was observed on a 70% carbonated apatite, which ha s a composition similar to bone mineral, whereas, cell toxicity was ob served on cells grown on amorphous calcium phosphate. This in vitro cu lture system demonstrates the use of human bone marrow cells for the p otential evaluation of new biomaterials and the development of a novel carbonated apatite that may be of potential use in orthopaedic implan ts. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.