The Proteoglycan Metabolism of Articular Cartilage in Joint-Scale Culture

Abstract

Understanding and controlling chondrocyte and cartilage metabolism in osteochondral tissues may facilitate ex vivo maintenance and application, both for allografts and tissue-engineered grafts. The hypothesis of this study was that maintenance of chondrocyte viability and matrix content and release of sulfated glycosaminoglycan (sGAG) in the articular cartilage of joint-scale osteochondral fragments are temperature and metabolism dependent. The aims were to assess, for adult goat joints, the effects of incubation temperature (378C vs. 48C) on cartilage chondrocyte viability and tissue matrix content and mechanical function, and the effects of temperature and cellular biosynthesis on sGAG release. Chondrocyte viability was maintained with 378C incubation for 28 days, but decreased by *30% with 48C incubation. Concomitantly, with 378C incubation, cartilage sGAG was depleted by *52% with the lost sGAG predominantly unable to aggregate with hyaluronan, whereas collagen content, tissue thickness, and tissue stiffness were maintained. The depletion of sGAG was diminished by slowing metabolism, with 48C decreasing release by *79% compared with 378C incubation, and cycloheximide inhibition of cell metabolism at 378C decreasing release by *47%. These results indicate that the articular cartilage of joint-scale grafts have enhanced chondrocyte viability with incubation at 378C, but may need anabolic stimuli or catabolic inhibitors to maintain sGAG content.

The In Vivo Performance of Osteochondral Allografts in the Goat Is Diminished With Extended Storage and Decreased Cartilage Cellularity

“…Alternatively, osteochondral allograft storage at 37°C may be one option to support long-term viability of chondrocyte in vitro , especially at the articular surface. 5,22,26 Grafts stored at 37°C may also have better biological performance than 4°C-stored grafts, by providing lubricating molecules such as proteoglycan-4 (PRG4) to maintain a low-friction articulating surface. 35,36 Since some 4°C-stored allografts maintained relatively high surface cellularity, an alternative biological marker of superficial zone health may be useful to screen grafts prior to implantation.…”

Osteochondral allograft transplantation in cartilage repair: Graft storage paradigm, translational models, and clinical applications

“…). Through the in vitro storage studies, we determined (1) that OCA stored traditionally in lactated Ringer's solution should be implanted within seven days of donor death (as appropriate for the empirical university model); (2) the cartilage matrix is preserved during storage in tissue culture medium (TCM) at 4°C for 28 days, but the chondrocytes necessary to maintain the matrix after transplantation decreases over time; (3) chondrocyte viability was higher after storage at 4°C for 28 days when additional nutrients (i.e., serum) were added to the media and the superficial zone was a target for decreased viability after 14 days; (4) chondrocyte death during storage is likely mediated by apoptosis and modifications to the apoptotic response by adding a TNF inhibitor to TCM can improve chondrocyte viability during 4°C storage for up to 28 days (5) 37°C storage of OCA supports long‐term (≥4 weeks) chondrocyte viability, especially at the articular surface, but cartilage of joint‐scale OCAs may need additional anabolic stimuli or catabolic inhibitors to maintain matrix (e.g., GAG) content; and (6) the results of in vitro storage data in human and goat tissue was consistent with that of clinical practice: 4°C stored grafts have lower chondrocyte viability at the time of OCA transplantation versus fresh grafts …”

Treatment of Articular Cartilage Defects in the Goat with Frozen Versus Fresh Osteochondral Allografts: Effects on Cartilage Stiffness, Zonal Composition, and Structure at Six Months

“…With use of a benchtop mechanical tester (v500cs, BioSyntech Canada, Laval, Quebec, Canada), samples were compressed rapidly, by 100 mm, at three sites that were 0.5 mm apart (proximal to distal) 25 . The peak load was divided by the indentation depth, normalized to cartilage thickness and indenter tip area, and three points averaged to determine the indentation material stiffness, expressed in units of MPa.…”