Disruption of endogenous perlecan function improves differentiation of rat articular chondrocytes in vitro

Abstract

Heparan sulfate (HS) and heparan sulfate proteoglycans (HSPG) are necessary for normal cartilage development and chondrocyte differentiation. However, recent studies demonstrated that HSPG accelerate dedifferentiation and catabolism in chondrocytes from degenerative cartilage. In this study, we investigated the inhibitory effect of HSPG on chondrocyte differentiation in vitro. Rat articular chondrocytes were cultured at low (0.3 × 10(4) cells/cm(2) ) and high (1.5 × 10(5) cells/cm(2) ) density in the presence or absence of heparitinase I, an HS degrading enzyme. Cells cultured at low density dedifferentiated and exhibited an elongated morphology, and treatment with heparitinase I precluded cell elongation. Conversely, populations of chondrocytes cultured at high density exhibited either a dedifferentiated or differentiated phenotype. Glycosaminoglycan accumulation increased in heparitinase I-treated cells. To determine the function of perlecan, an important HSPG for cartilage development, in chondrocyte differentiation, rat chondrocyte cultures were exposed to an anti-perlecan antiserum to inhibit perlecan function. Western blotting analysis indicated that preventing perlecan activity increased type II collagen synthesis. Our results suggest that HSPG are negative regulators of chondrocyte differentiation in vitro and that perlecan contributes to chondrocyte dedifferentiation in vitro.

Perlecan: Roles in osteoarthritis and potential treating target

“…Furthermore, perlecan can also result in a significant increase in elasticity [39], whereas deficiency leads to reduced cellular and ECM stiffness in vivo. In addition to its inhibitory effect on COLII synthesis [40], perlecan knockdown also resulted in a decrease in the PCM component and an increase in the bulk matrix, suggesting that the ability of newly synthesized ECM to incorporate into the matrix was impaired without influencing the components of ECM.…”

Regulation of FGF-2, FGF-18 and Transcription Factor Activity by Perlecan in the Maturational Development of Transitional Rudiment and Growth Plate Cartilages and in the Maintenance of Permanent Cartilage Homeostasis

“…Basement membranes are structures which finely tune cellular function and cell–matrix interactions. In chondrocyte monolayer cultures where HS levels are depleted by inclusion of heparanase in the culture medium, increased chondrocyte proliferative rates and GAG deposition occurs compared to control cultures [ 119 ].…”