Bonding of articular cartilage utilising a combination of biochemical degradation and surface cross-linking

After trauma, articular cartilage often does not heal due to incomplete bonding of the fractured surfaces. Within this study we investigated the ability of chem. cross-linkers to facilitate bonding of articular cartilage, either alone or in combination with a pre-treatment with surface-degrading agents. Articular cartilage blocks were harvested from the femoropatellar groove of bovine calves. Two cartilage blocks, either after pre-treatment or without, were assembled in a custom-designed chamber in partial apposition and subjected to crosslinking treatment. Subsequently, bonding of cartilage was measured as adhesive strength, i.e., the max. force at rupture of bonded cartilage blocks divided by the overlap area. In a first approach, bonding was investigated after treatment with crosslinking reagents only, employing (A) glutaraldehyde, (B) 1-ethyl-3-diaminopropylcarbodiimide (EDC)/N-hydroxysuccinimide (NHS), (C) genipin, or (D) transglutaminase. Expts. were conducted with or without compression of the opposing surfaces. Compression during crosslinking strongly enhanced bonding, esp. when applying EDC/NHS and glutaraldehyde. Therefore, all further expts. were performed under compressive conditions. When combining each of the four crosslinking agents with the degrading pre-treatments pepsin, trypsin, and guanidine, pre-treatment led to distinct improvement of bonding, as compared to the use of cross-linkers alone. The highest values in adhesive strength were achieved employing the combinations pepsin or guanidine with EDC/NHS, and guanidine with glutaraldehyde. The release of extracellular matrix components (ECM), i.e., glycosaminoglycans and total collagen, from cartilage blocks after pre-treatment was measured, but could not directly be correlated to the detd. adhesive strength. Cytotoxicity was detd. for all substances employed, i.e., surface degrading agents and cross-linkers, using the resazurin assay. Taking the favorable cell vitality after treatment with pepsin and EDC/NHS and the cytotoxic effects of guanidine and glutaraldehyde into account, the combination of pepsin and EDC/NHS appeared as the most advantageous treatment within this study. In conclusion, bonding of articular cartilage blocks was achieved by chem. fixation of their surface components using crosslinking reagents. Application of compressive forces and prior modulation of surface structures enhanced cartilage bonding significantly. Enzymic treatment in combination with cross-linkers may represent a promising addn. to current techniques for articular cartilage repair