SPATIOTEMPORAL ASSESSMENT OF FETAL BOVINE OSTEOBLAST CULTURE DIFFERENTIATION INDICATES A ROLE FOR BSP IN PROMOTING DIFFERENTIATION

Fetal bovine mandible-derived osteoblasts were cultured for the purpos e of obtaining a spatiotemporal assessment of bone matrix protein expr ession during in vitro differentiation, The results obtained from elec tron microscopic, immunohistological, biochemical, and molecular biolo gical analyses indicated that these primary cultured osteoblasts produ ce an abundant extracellular matrix which mineralizes during a 14-day culture period, During this process, a restricted, spatiotemporal patt ern of bone sialoprotein expression was indicated by immunohistologica l and molecular evaluations, To test the possibility that bone sialopr otein promoted the continued morphodifferentiation of osteoblastic cel ls, cultures were grown in the presence of anti-bone sialoprotein anti bodies known to interfere with cell-bone sialoprotein attachment, Comp ared with cultures grown in the presence of normal rabbit serum (1:150 ), cultures grown in the media containing anti-bone sialoprotein antib ody (1:150) failed to mineralize as demonstrated by von Kossa staining and failed to express osteocalcin and osteopontin as shown by the rev erse transcription polymerase chain reaction, These results contribute to the growing evidence that bone sialoprotein Is an important determ inant of osteoblast differentiation and bane formation, Matrix protein -cell interactions may be examined using this spatiotemporally defined model.