title: Effects of compression on the loss of newly synthesized proteoglycans and proteins from cartilage explants.
abstract: The effects of mechanical compression of calf cartilage explants on the catabolism and loss into the medium of proteoglycans and proteins radiolabeled with [35S]sulfate and [3H]proline were examined. A single 2- or 12-h compression of 3-mm diameter cartilage disks from a thickness of 1.25 to 0.50 mm, or slow cyclic compression (2 h on/2 h off) from 1.25 mm to 1.00, 0.75, or 0.50 mm for 24 h led to transient alterations and/or sustained increases in loss of radiolabeled macromolecules. The effects of imposing or removing loads were consistent with several compression-induced physical mediators including fluid flow, diffusion, and matrix disruption. Cyclic compression induced convective fluid flow and enhanced the loss of 35S- and 3H-labeled macromolecules from tissue into medium. In contrast, prolonged static compression induced matrix consolidation and appeared to hinder the diffusional transport and loss of 35S- and 3H-labeled macromolecules. Since high amplitude cyclic compression led to a sustained increase in the rate of loss of 3H- and 35S-labeled macromolecules that was accompanied by an increase in the rate of loss of [3H]hydroxyproline residues and an increase in tissue hydration, such compression may have caused disruption of the collagen meshwork. The 35S-labeled proteoglycans lost during such cyclic compression were of smaller average size than those from controls, but contained a similarly low proportion (approximately 15%) that could form aggregates with excess hyaluronate and link protein. The size distribution and aggregability of the remaining tissue proteoglycans and 35S-labeled proteoglycans were not markedly affected. The loss of tissue proteoglycan paralleled the loss of 35S-labeled macromolecules. This study provides a framework for elucidating the biophysical mechanisms involved in the redistribution, catabolism, and loss of macromolecules during cartilage compression.
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology & Harvard-M.I.T., Cambridge.
authors.forename: R L
authors.initials: RL
authors.lastname: Sah
authors.forename: J Y
authors.initials: JY
authors.lastname: Doong
authors.forename: A J
authors.initials: AJ
authors.lastname: Grodzinsky
authors.forename: A H
authors.initials: AH
authors.lastname: Plaas
authors.forename: J D
authors.initials: JD
authors.lastname: Sandy
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism*; D002417:Cattle; D006909:Hydroxyproline / Q000032:analysis; D007700:Kinetics; D009924:Organ Culture Techniques; D011312:Pressure; D011392:Proline / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins / Q000302:isolation & purification; D011509:Proteoglycans / Q000096:biosynthesis* / Q000302:isolation & purification; D013314:Stress, Mechanical; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes; D014316:Tritium
chemical_list: D011506:Proteins; D011509:Proteoglycans; D013431:Sulfates; D013462:Sulfur Radioisotopes; D014316:Tritium; D011392:Proline; D006909:Hydroxyproline