CELLULAR-RESPONSES TO CHEMICAL AND MORPHOLOGIC ASPECTS OF BIOMATERIALSURFACES .2. THE BIOSYNTHETIC AND MIGRATORY RESPONSE OF BONE CELL-POPULATIONS

The biosynthetic and migratory response of bone cells to changes in bo th surface composition and morphology of polystyrene (PS) substrates w as examined. A system was devised wherein micromachined silicon wafers were used as templates to solvent-cast PS replicas [using 0, 1, or 2 wt % styrene (S) monomer additions] with either 0.5- or 5.0-mu m-deep surface grooves. Smooth replicas (0% S) served as the control surfaces . The chemical and morphologic characteristics of the nine unique mode l biomaterial surfaces (MBSs) produced using this system were document ed and were found to be distinct. For the biosynthetic studies, bone c ells isolated from neonatal rat calvaria were plated onto the MBSs and labeled at postconfluence with [C-14]proline for 24 h. Total DNA per surface, total newly synthesized collagenous (CP), and noncollagenous protein (NCP) (cell associated and secreted) were determined. Cell-ass ociated CP was found to increase significantly for the bone cells cult ured on the substrates with 0.5-mu m grooves and 2% S (P <.05). Cell-a ssociated NCP was found to be elevated for all 2% S substrates and for the 0.5-mu m grooves substrates with 1% S. For the migration studies, bone cells were plated first onto 5-mm nitrocellulose disks that were attached to standard Petri dishes using a plasma clot. At confluence, the disks were removed aseptically and placed on the replicas. The ce llular area occupied as a result of the outward migration of the bone cells was measured after 4 days of culture using an image analysis sys tem. An average velocity for the leading edge of bone cell populations on each of the nine MBSs was calculated: Cells on surfaces with eithe r 1% S or 5.0-mu m grooves displayed significantly higher velocities t han did the control cultures. A significant interaction effect between chemistry and morphology was observed. The biosynthetic and migratory responses of in vitro cultures of bone cells were not predictable fro m the observations of the cellular responses to the individual feature s, but appeared to depend on cellular responses to more than one subst rate factor. (C) 1995 John Wiley and Sons, Inc.