Differential effects of static and dynamic compression on meniscal cell gene expression

Cells of the meniscus are exposed to a wide range of time-varying mechanical stimuli that may regulate their metabolic activity in vivo. In this study, the biological response of the meniscus to compressive stimuli was evaluated in vitro, using a well-controlled explant culture system. Gene expression for relevant extracellular matrix proteins was quantified using real-time RT-PCR following a 24 h period of applied static (0.1 MPa compressive stress) or dynamic compression (0.08-0.16 MPa). Static and dynamic compression were found to differentially regulate mRNA levels for specific proteins of the extracellular matrix. Decreased mRNA levels were observed for decorin (similar to2.1 fold-difference) and type II collagen (similar to4.0 fold-difference) following 24 It of dynamic compression. Decorin mRNA levels also decreased following static compression (similar to4.5 fold-difference), as did mRNA levels for both types I (similar to3.3 fold-difference) and II collagen (similar to4.0 fold-difference). Following either static or dynamic compression, mRNA levels for aggrecan, biglycan and cytoskeletal proteins were unchanged. It is noteworthy that static compression was associated with a 2.6 fold-increase in mRNA levels for collagenase, or MMP-1, suggesting that the homeostatic balance between collagen biosynthesis and catabolism was altered by the mechanical stimuli. These findings demonstrate that the biosynthetic response of the meniscus to compression is regulated, in part, at the transcriptional level and that transcription of types I and 11 collagen as well as decorin may be regulated by common mechanical stimuli. (C) 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.