Hydrostatic fluid pressure enhances matrix synthesis and accumulation by bovine chondrocytes in three-dimensional culture

Monolayer cell cultures and cartilage tissue fragments have been used to examine the effects of hydrostatic fluid pressure (HFP) on the anabolic and catabolic functions of chondrocytes. In this study, bovine articular chondrocytes (bACs) were grown in porous three-dimensional (3-D) collagen sponges, to which constant or cyclic (0.015 Hz) HFP was applied at 2.8 MPa for up to 15 days. The effects of HFP were evaluated histologically, immunohistochemically, and by quantitative biochemical measures. Metachromatic matrix accumulated around the cells within the collagen sponges during the culture period. There was intense intracellular, pericellular, and extracellular immunoreactivity for collagen type II throughout the sponges in all groups. The incorporation of [(35)S]-sulfate into glycosaminoglycans (GAGs) was 1.3-fold greater with constant HFP and 1.4-fold greater with cyclic HFP than in the control at day 5 (P < 0.05). At day 15, the accumulation of sulfated-GAG was 3.1-fold greater with constant HFP and 2.7-fold with cyclic HFP than the control (0.01). Quantitative immunochemical analysis of the matrix showed significantly greater accumulation of chondroitin 4-sulfate proteoglycan (C 4-S PG), keratan sulfate proteoglycan (KS PG), and chondroitin proteoglycan (chondroitin PG) than the control (P < 0.01). With this novel HFP culture system, 2.8 MPa HFP stimulated synthesis of cartilage-specific matrix components in chondrocytes cultured in porous 3-D collagen sponges.