αv and β1 integrins regulate dynamic compression-induced proteoglycan synthesis in 3D gel culture by distinct complementary pathways

Objective Our goal was to test the hypothesis that specific integrin receptors regulate chondrocyte biosynthetic response to dynamic compression at early times in 3D gel culture, during initial evolution of the pencellular matrix, but prior to significant accumulation of further-removed matrix The study was motivated by increased use of dynamic loading, in vitro, for early stimulation of tissue engineered cartilage, and the need to understand the effects of loading, in vivo, at early times after implantation of constructs. Methods. Bovine articular chondrocytes were seeded in 2% agarose gels (15 x 10(6) cells/mL) and incubated for 18 h with and without the presence of specific integrin blockers (small-molecule peptidomimetics. function-blocking antibodies, and RGD-containing disintegrins). Samples were then subjected to a 24-h dynamic compression regime found previously to stimulate chondrocyte biosynthesis in 3D gel as well as cartilage explant culture (1 Hz, 2 5% dynamic strain amplitude, 7% static offset strain). At the end of loading, proteoglycan (PG) synthesis (S-35-sulfate incorporation), protein synthesis (H-3-proline incorporation), DNA content (Hoechst dye 33258) and total glycosaminoglycan (GAG) content (dimethyl methylene blue (DMMB) dye binding) were assessed Results: Consistent with previous studies, dynamic compression increased PG synthesis and total GAG accumulation compared to free-swelling controls Blocking alpha v beta 3 abolished this response, independent of effects on controls, while blocking (31 abolished the relative changes in synthesis when changes in free-swelling synthesis rates were observed Conclusions This study suggests that both alpha v0 beta 3 and beta 1 play a role in pathways that regulate stimulation of PG synthesis and accumulation by dynamic compression, but through distinct complementary mechanisms (C) 2009 Osteoarthrotis Research Society International Published by Elsevier Ltd All rights reserved.