Chondroitin sulfate is a critical component ofarticular cartilage due to its contribution to the tissue's resistance tocompressive deformation. Alterations inthe biosynthesis of this molecule over time could impact the ability of the tissue to perform its necessary functions. Several factors have been shown to alter the biosynthesis of chondroitin sulfate in cartilage; among them are age, disease, depth of tissue, and mechanical compression. Specifically, mechanical compression has been shown to have a significant effect on the sulfation pattern and chain length and number in cartilage explant studies. The mechanisms that govern these alterations, however, have not been determined. The purpose of this study is to examine the effects of mechanical compression on chondroitin sulfate biosynthesis and analyze the roles of two possible mechanisms; enzyme transcription ad organelle deformation.
The effects of mechanical compression on the transcription rates of enzymes associated with the biosynthesis ofchondroitin sulfate have not been previously studied. To perform this study in a bovine model, portions of the bovine genome had to be sequenced, PCR primers designed, and bulk expression levels determined. Static compression resulted in the significant up-regulationf two genes of interest: chondroitin sulfate and GalNAc 4S,6-sulfotransferase. Dynamicompression resulted in the significant up-regulationf the three sulfotransferases responsible for the bulk of sulfation in cartilage tissue. These results indicate atransient mechanotransduction reaction that differs based on the load regime.
The effect of mechanical loading on the biosynthesis ofchondroitin sulfate has been studied previously, however, this study seeks to examine more comprehensive loading regimes. Static compression and release resulted in an increase in 6-sulfation and a decrease in 4-sulfation that lasted to 48 hours after release of compression. Dynamic compression and release had the oppositeffect on sulfation ratio, with an increase in 4- sulfation compared to 6-sulfation. The transcription changes seen in this study do not indicate the changes that occur in the end products of synthesis. Other factors may play a larger role, such as precursor availability or transport through the Golgi apparatus.
Intracellular organelles reacto static compression of the surrounding tissue in one of two manners. The majority of organelles deform much as the nucleus, proportionally in volume and shape to the cell. The Golgi apparatus appears to retain a significant portion of its volume relative to the cell and other organelles. In addition, it reformstructurally into a highly ordered stacked appearance. Osmotic forces within the Golgi may allow it to balance the osmotic load in the cytoplasm and resist compression and altered trafficking of the Golgi may in turn produce the altered appearance. Recent microscopy experiments on the Golgi apparatustilizing two-photon microscopy have allowed us to examine the reaction of live tissue to static compression.
These results illustrate the significant, but differing, effects of static and dynamic compression on the biosynthesis ofchondroitin sulfate. The effects of these compression types on the transcriptionf enzymes responsible for this biosynthesis cannot fully explain the changes seen in newly synthesized chondroitin sulfate. Organelle reorganization has been shown to occur in response to static load and it is possible that altered organelle trafficking plays a role in this altered biosynthesis. Further studies are necessary todetermine the final effect of the altered transcription ad organelle structure on the manufacture of this important cartilage molecule
|1999||Buschmann MD, Kim Y-J, Wong M, Frank E, Hunziker EB, Grodzinsky AJ. Stimulation of aggrecan synthesis in cartilage explants by cyclic loading is localized to regions of high interstitial fluid flow1. Arch Biochem Biophys. June 1, 1999;366(1):1-7.|
|1999||Herberhold C, Faber S, Stammberger T, Steinlechner M, Putz R, Englmeier K, Reiser M, Eckstein F. In situ measurement of articular cartilage deformation in intact femoropatellar joints under static loading. J Biomech. December 1999;32(12):1287-1295.|
|2003||Ng L, Grodzinsky AJ, Patwari P, Sandy J, Plaas A, Ortiz C. Individual cartilage aggrecan macromolecules and their constituent glycosaminoglycans visualized via atomic force microscopy. J Struct Biol. September 2003;143(3):242-257.|
|1999||Mow VC, Wang CC, Hung CT. The extracellular matrix, interstitial fluid and ions as a mechanical signal transducer in articular cartilage. Osteoarthritis Cartilage. January 1999;7(1):41-58.|
|2001||Erickson GR, Alexopoulos LG, Guilak F. Hyper-osmotic stress induces volume change and calcium transients in chondrocytes by transmembrane, phospholipid, and G-protein pathways. J Biomech. December 2001;34(12):1527-1535.|
|1989||Urban JPG, Bayliss MT. Regulation of proteoglycan synthesis rate in cartilage in vitro: influence of extracellular ionic composition. Biochim Biophys Acta. July 21, 1989;992(1):59-65.|
|1986||Schneiderman R, Keret D, Maroudas A. Effects of mechanical and osmotic pressure on the rate of glycosaminoglycan synthesis in the human adult femoral head cartilage: an in vitro study. J Orthop Res. 1986;4(4):393-408.|
|1989||Sah RL-Y, Kim Y-J, Doong J-YH, Grodzinsky AJ, Plass AHK, Sandy JD. Biosynthetic response of cartilage explants to dynamic compression. J Orthop Res. 1989;7(5):619-636.|
|2000||Guilak F, Tedrow JR, Burgkart R. Viscoelastic properties of the cell nucleus. Biochem Biophys Res Commun. March 24, 2000;269(3):781-786.|
|1996||Buschmann MD, Hunziker EB, Kim YJ, Grodzinsky AJ. Altered aggrecan synthesis correlates with cell and nucleus structure in statically compressed cartilage. J Cell Sci. February 1996;109(2):499-508.|
|2004||Fitzgerald JB, Jin M, Dean D, Wood DJ, Zheng MH, Grodzinsky AJ. Mechanical compression of cartilage explants induces multiple time-dependent gene expression patterns and involves intracellular calcium and cyclic AMP. J Biol Chem. May 7, 2004;279(19):19502-19511.|
|1996||Smith RL, Rusk SF, Ellison BE, Wessells P, Tsuchiya K, Carter DR, Caler WE, Sandell LJ, Schurman DJ. In vitro stimulation of articular chondrocyte mRNA and extracellular matrix synthesis by hydrostatic pressure. J Orthop Res. 1996;14(1):53-60.|
|1999||Guilak F, Jones WR, Ting-Beall HP, Lee GM. The deformation behavior and mechanical properties of chondrocytes in articular cartilage. Osteoarthritis Cartilage. January 1999;7(1):59-70.|
|1985||Eisenberg SR, Grodzinsky AJ. Swelling of articular cartilage and other connective tissues: electromechanochemical forces. J Orthop Res. 1985;3(2):148-159.|
|1998||Quinn TM, Grodzinsky AJ, Buschmann MD, Kim YJ, Hunziker EB. Mechanical compression alters proteoglycan deposition and matrix deformation around individual cells in cartilage explants. J Cell Sci. March 1998;111(5):573-583.|
|2000||Frank EH, Jin M, Loening AM, Levenston ME, Grodzinsky AJ. A versatile shear and compression apparatus for mechanical stimulation of tissue culture explants. J Biomech. November 2000;33(11):1523-1527.|
|1988||Gundersen HJG, Bendtsen TF, Korbo L, Marcussen N, Møller A, Nielsen K, Nyengaard JR, Pakkenberg B, Sørensen FB, Vesterby A, West MJ. Some new, simple and efficient stereological methods and their use in pathological research and diagnosis. AMPIS. May 1988;96(5):379-394.|
|2001||Jin M, Frank EH, Quinn TM, Hunziker EB, Grodzinsky AJ. Tissue shear deformation stimulates proteoglycan and protein biosynthesis in bovine cartilage explants. Arch Biochem Biophys. November 1, 2001;395(1):41-48.|
|1986||Hodge WA, Fijan RS, Carlson KL, Burgess RG, Harris WH, Mann RW. Contact pressures in the human hip joint measured in vivo. Proc Natl Acad Sci USA. May 1986;83(9):2879-2883.|
|1995||Guilak F. Compression-induced changes in the shape and volume of the chondrocyte nucleus. J Biomech. December 1995;28(12):1529-1541.|
|1996||Sah RL, Trippel SB, Grodzinsky AJ. Differential effects of serum, insulin-like growth factor-I, and fibroblast growth factor-2 on the maintenance of cartilage physical properties during long-term culture. J Orthop Res. January 1996;14(1):44-52.|
|1991||Hall AC, Urban JPG, Gehl KA. The effects of hydrostatic pressure on matrix synthesis in articular cartilage. J Orthop Res. January 1991;9(1):1-10.|
|2001||Kurz B, Jin M, Patwari P, Cheng DM, Lark MW, Grodzinsky AJ. Biosynthetic response and mechanical properties of articular cartilage after injurious compression. J Orthop Res. 2001;19(6):1140-1146.|
|1996||Kim Y-J, Grodzinsky AJ, Plaas AHK. Compression of cartilage results in differential effects on biosynthetic pathways for aggrecan, link protein, and hyaluronan. Arch Biochem Biophys. April 15, 1996;328(2):331-340.|