Marrow stromal osteoblast function on a poly(propylene fumarate)/beta-tricalcium phosphate biodegradable orthopaedic composite

The objective of this study was to assess the osteoconductivity of a poly(p ropylene fumarate)/beta-tricalcium phosphate (PPF/beta-TCP) composite in vi tro. We examined whether primary rat marrow stromal cells would attach, pro liferate, and express differentiated osteoblastic function when seeded on P PF/beta-TCP substrates. Attachment studies showed that a confluent monolaye r of cells had adhered to the substrates within an 8 h time frame for marro w stromal cells seeded at confluent numbers. Proliferation and differentiat ed function of the cells were then investigated for a period of 4 weeks for an initial seeding density of 42 000 cells/cm(2). Rapid proliferation duri ng the first 24 h as determined by H-3-thymidine incorporation was mirrored by an initial rapid increase in total cell number by DNA assay. A lower pr oliferation rate and a gradual increase in cell number persisted for the re mainder of the study, resulting in a final cell number of 128 000 cells/cm( 2). Differentiated cell function was assessed by measuring alkaline phospha tase (ALP) activity and osteocalcin (OC) production throughout the time cou rse. Both markers of osteoblastic differentiation increased significantly o ver a 4-week period. By day 28, cells grown on PPF/beta-TCP reached a maxim al ALP activity of 11 (+/-1) x 10(-7) mu mol/min/cell, while the OC product ion reached 40 (+/-1) x 10(-6) ng/cell. These data show that a PPF/beta-TCP composite exhibits in vitro osteoconductivity similar to or better than th at of control tissue culture polystyrene. (C) 2000 Elsevier Science Ltd. Al l rights reserved.