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

The objective of this study was to assess the osteoconductivity of a poly(propylene fumarate)/β-tricalcium phosphate (PPF/β-TCP) composite in vitro. We examined whether primary rat marrow stromal cells would attach, proliferate, and express differentiated osteoblastic function when seeded on PPF/β-TCP substrates. Attachment studies showed that a confluent monolayer of cells had adhered to the substrates within an 8h time frame for marrow stromal cells seeded at confluent numbers. Proliferation and differentiated function of the cells were then investigated for a period of 4 weeks for an initial seeding density of 42 000cells/cm². Rapid proliferation during the first 24h as determined by ³H-thymidine incorporation was mirrored by an initial rapid increase in total cell number by DNA assay. A lower proliferation rate and a gradual increase in cell number persisted for the remainder of the study, resulting in a final cell number of 128 000cells/cm². Differentiated cell function was assessed by measuring alkaline phosphatase (ALP) activity and osteocalcin (OC) production throughout the time course. Both markers of osteoblastic differentiation increased significantly over a 4-week period. By day 28, cells grown on PPF/β-TCP reached a maximal ALP activity of 11 (±1)x10^-7μmol/min/cell, while the OC production reached 40 (±1)x10^-6ng/cell. These data show that a PPF/β-TCP composite exhibits in vitro osteoconductivity similar to or better than that of control tissue culture polystyrene. Copyright (C) 2000 Elsevier Science B.V.