Running Inhibits the Reversal of Atrophic Changes in Canine Knee Cartilage After Removal of a Leg Cast

Abstract

The effect of vigorous exercise on the reversibility of canine knee cartilage atrophy produced by immobilization OF the leg was studied. In comparison to cartilage from the contralateral control knees, cartilage from knees which had been immobilized in a cast For 6 weeks showed an increase in water content and decreases in thickness, Safranin 0 staining of the matrix, uronic acid content, and net proteoglycan synthesis. In addition, the ability OF both newly synthesized (3'S) and total tissue proteoglycans to interact with hyaluronic acid to Form aggregates was diminished; this was apparently due to an abnormality in the hyaluronate-binding region of the core proteins. If the casts were removed and the animals were then allowed to ambulate ad libitum for 3 weeks, a11 of these changes were reversed. However, knee cartilage from 3 dogs which had been run daily on a treadmill (6 miledday) for 3 weeks after removal of the casts exhibited continuing decreases in thickness, Safranin 0 staining, and uronic acid content (mean 31%), even though net proteoglycan synthesis was increased (mean 16%) in comparison to that in control cartilage from the contralateral (nonimmobilized) knee. Further- more, the abnormality in both 35!3-and total tissue proteoglycans which precluded their interaction with high molecular weight hyaluronic acid persisted. In this respect, the proteoglycans were indistinguishable from those obtained from knee cartilage immediately following 6 weeks in a cast.A number of reports have detailed the morphologic features of the degeneration that occurs in articular cartilage with immobilization of a limb (1-5). Few studies, on the other hand, have focused on the alterations in articular cartilage proteoglycans (PG) that result from immobility (6-7). In normal joint cartilage, most PG exist in large aggregates, in which a number of PG are noncovalently associated with a single filamentous molecule of hyaluronic acid (HA) in a linkage stabilized by tissue glycoproteins (8). PG account for most of the elasticity ofjoint cartilage and for its ability to resist compression (9). The biologic function of the aggregate has yet to be defined, but by virtue of its enormous size (over50 x ddtons) (lo), it presumably serves to contain the PG within the collagen meshwork of the cartilage.We have recently shown that the atrophy of knee cartilage which develops when the hind limb of a normal adult dog is immobilized in a cast for 6 weeks is accompanied by decreases in uronic acid content and net PG synthesis (7). Furthermore, newly synthesized PG from cartilage of the immobilized limb did not aggregate in vitro, due to an apparent abnormality in the HA-binding region of the PG core protein (7). All of these effects of immobilization were rapidly reversible if the casts were removed and the dogs were then allowed to ambulate ad libitum "on all fours" for 3 MATERIALS AND METHODSSource of tissue and procedure for immobilization and exercise. The right hind limbs of 7 adult mongrel dogs (25-30 kg) were immobilized against t...

Comparison of novel clinically applicable methodology for sensitive diagnostics of cartilage degeneration

“…1) and biochemical properties could be established. An optimal way of assessing the degree of OA can be debated (Pritzker et al, 2006). In this study, we utilized the traditional Mankin score to judge structural integrity of cartilage.…”

“…This leads to softening of the tissue (Armstrong and Mow, 1982). Softened articular cartilage fails to resist impact forces during normal loading and this endangers the tissue to fissures and fibrillation (Palmoski and Brandt, 1981). Tissue degeneration leads to inflow of water and, thereby, to an increase in water content of the tissue.…”

Análise termogravimétrica da cartilagem articular de ratos exercitados após imobilização

“…Vários experimentos descreveram que o exercício de carga moderada na cartilagem articular gera aumento da síntese e da concentração de proteoglicanas e de glicosaminoglicana 18,19 . Além disso, ele promove aumento do volume da cartilagem e adaptação da mesma ao esforço 20 e estimulando os condrócitos a produzir os elementos que compõem a matriz extracelular 13,21,22 .…”

Intra-articular Injection of Hyaluronan Diminishes Loss of Chondrocytes in a Rat Immobilized-Knee Model

“…These contradictory results may be explained by the difference in rigidity of immobilization. Some reported that the articular cartilage was thickened (Sood 1971), others reported that it was thinned (Palmoski and Brandt 1981), and even others reported no change in thickness (O'Connor 1997;Trudel et al 2005). These contradictory results may be explained by a lack of standard measurement sites, use of young or old animals, or use of contralateral knees as controls (O'Connor 1997).…”