The effect of glycosaminoglycan loss on chondrocyte viability: A study on porcine cartilage explants

Abstract

Objective. Loss of glycosaminoglycan (GAG) is an early event in osteoarthritis. Recent findings showed increased cell death in arthritic cartilage and linkage with extracellular matrix degradation. The aim of this study was to analyze the direct effect of GAG loss on chondrocyte survival and cell death following mechanical injury.Methods. In full-thickness cartilage explants from porcine knee joints, GAG was depleted by digestion with chondroitinase ABC. Explants were subjected to single-impact mechanical injury. Cell viability and the types of cell death were analyzed by Live/Dead cell assay, staining for active caspase 3, and sensitivity to caspase inhibitor.Results. GAG depletion did not directly lead to increased cell death. In chondroitinase ABC-treated explants, but not in control explants, mechanical injury caused an immediate reduction in cell viability (from 84.6% to 71.0%); the reduction was prominent in the superficial zone. This immediate cell death was not inhibited by the pancaspase inhibitor Z-VAD-FMK, suggesting cell necrosis. During subsequent culture, viability in these explants decreased further, to 50.5% on day 3. The second wave of cell death was reduced by the addition of Z-VAD-FMK in chondroitinase ABC-treated explants and was also associated with activation of caspase 3, suggesting apoptotic mechanisms of cell death.Conclusion. These results indicate that GAG loss alone does not directly lead to chondrocyte death. In response to mechanical injury, there is an immediate induction of necrotic cell death that is seen only in GAG-depleted explants and primarily in the superficial zone. During subsequent culture, cell death spreads via apoptotic mechanisms.

Aging-related loss of the chromatin protein HMGB2 in articular cartilage is linked to reduced cellularity and osteoarthritis

“…Ϫ/Ϫ mice demonstrate an increased susceptibility to apoptosis, as induced by antibody to the CD95/Fas receptor, and the SZ is more susceptible to cell death induced by mechanical stress (7). These findings suggest that chromatin factor HMGB2 may facilitate survival of SZ chondrocytes.…”

“…Mechanical stress has been implicated in initiating the superficial lesions (6); the SZ is more susceptible to cell death induced by mechanical stress (7), but molecular mechanisms remain to be elucidated. The SZ of articular cartilage is unique in cell morphology and extracellular matrix composition.…”

Influence of Temporary Chondroitinase ABC-Induced Glycosaminoglycan Suppression on Maturation of Tissue-Engineered Cartilage

“…3,4 A number of studies have used chondroitinase ABC (CABC) to deplete cartilage of glycosaminoglycan (GAG) and to investigate the immediate effects on both mechanical properties and biologic responses to such perturbation of the tissue. [5][6][7] CABC specifically depolymerizes chondroitin and dermatan sulfate, 8 while collagen, the collagen network arrangement, keratan sulfate, and link protein remain unaffected by the enzyme. 9,10 It has been shown that the compressive Young's modulus obtained from an indentation test decreases significantly after treatment with collagenase and CABC.…”

Tougu Xiaotong capsule promotes chondrocyte autophagy by regulating the Atg12/LC3 conjugation systems

“…Therefore, in the present study, we sought to determine the efficacy of TXC on chondrocyte autophagy, as a chondroprotective agent. Excessive mechanical loading of articular cartilage causes damage to chondrocytes and the ECM, and initiates a pathogenetic process that occurs due to abnormal chondrocyte activation and results in the spreading of chondrocyte death and damage to the ECM beyond the initial area that was exposed to the highest mechanical load (24,25). The understanding of the mechanisms involved in these cellular changes may provide the potential to identify targets for pharmacological interventions in order to attenuate or prevent the subsequent development of OA.…”