MINERALIZATION OF MARROW-STROMAL OSTEOBLASTS MBA-15 ON 3-DIMENSIONAL CARRIERS

The present study describes a new three-dimensional(3-D) culture syste m that enables the maintenance and phenotypic expression of bone marro w stromal osteoblasts. This culture substratum is advantageous in that it provides suitable conditions for attachment, growth, and different iation of cells forming 3-D layers. The MBA-15 cell line was grown in unlimited quantities on 3-D Fibro-Cel carriers. These cells mineralize d when exposed to ascorbic acid and P-glycerophosphate (beta GP). Unde r these mineralization conditions, mRNA expressions of procollagen alp ha(2)(I) and [H-3]-proline-labeled protein were increased. The express ion of mRNA for osteonectin and to a lesser extent, for osteopontin wa s increased, whereas alkaline phosphatase and biglycan remained unaffe cted under similar conditions. Exposure of mineralizing cultures to de xamethasone reduced mRNA of procollagen alpha(2) (I) and osteonectin t o control level. Scanning electron microscopy revealed that cells were grown along the fabric's fibers and produced collagen fiberils. Under appropriate conditions, extensive mineralization had taken place. The mineralization process involves the formation of calcospherites, and correlates with an increase in calcium content. The Fibro-Cel carriers enable formation of 3-D architecture and mineralized tissue in vitro.