title: Bonding of articular cartilage using a combination of biochemical degradation and surface cross-linking.
abstract: After trauma, articular cartilage often does not heal due to incomplete bonding of the fractured surfaces. In this study we investigated the ability of chemical 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 cross-linking treatment. Subsequently, bonding of cartilage was measured as adhesive strength, that is, the maximum force at rupture of bonded cartilage blocks divided by the overlap area. In a first approach, bonding was investigated after treatment with cross-linking reagents only, employing glutaraldehyde, 1-ethyl-3-diaminopropyl-carbodiimide (EDC)/N-hydroxysuccinimide (NHS), genipin, or transglutaminase. Experiments were conducted with or without compression of the opposing surfaces. Compression during cross-linking strongly enhanced bonding, especially when applying EDC/NHS and glutaraldehyde. Therefore, all further experiments were performed under compressive conditions. Combinations of each of the four cross-linking agents with the degrading pre-treatments, pepsin, trypsin, and guanidine, led to distinct improvements in bonding compared to the use of cross-linkers alone. The highest values of adhesive strength were achieved employing combinations of pepsin or guanidine with EDC/NHS, and guanidine with glutaraldehyde. The release of extracellular matrix components, that is, glycosaminoglycans and total collagen, from cartilage blocks after pre-treatment was measured, but could not be directly correlated to the determined adhesive strength. Cytotoxicity was determined for all substances employed, that is, surface degrading agents and cross-linkers, using the resazurin assay. Taking the favourable 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 to be the most advantageous treatment in this study. In conclusion, bonding of articular cartilage blocks was achieved by chemical fixation of their surface components using cross-linking reagents. Application of compressive forces and prior modulation of surface structures enhanced cartilage bonding significantly. Enzymatic treatment in combination with cross-linkers may represent a promising addition to current techniques for articular cartilage repair.
authors.affiliation: Department of Trauma Surgery, University Medical Centre Regensburg, Franz-Josef-Strauss-Allee, 93053 Regensburg, Germany. carsten.englert@klinik.uni-regensburg.de
authors.forename: Carsten
authors.initials: C
authors.lastname: Englert
authors.forename: Torsten
authors.initials: T
authors.lastname: Blunk
authors.forename: Rainer
authors.initials: R
authors.lastname: Müller
authors.forename: Sabine Schulze
authors.initials: SS
authors.lastname: von Glasser
authors.forename: Julia
authors.initials: J
authors.lastname: Baumer
authors.forename: Johann
authors.initials: J
authors.lastname: Fierlbeck
authors.forename: Iris M
authors.initials: IM
authors.lastname: Heid
authors.forename: Michael
authors.initials: M
authors.lastname: Nerlich
authors.forename: Joachim
authors.initials: J
authors.lastname: Hammer
mesh_terms: D000268:Adhesiveness; D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects*; D002417:Cattle; D003094:Collagen / Q000032:analysis; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D006025:Glycosaminoglycans / Q000032:analysis; D019791:Guanidine / Q000494:pharmacology; D008422:Materials Testing; D010434:Pepsin A / Q000494:pharmacology; D033081:Shear Strength; D014014:Tissue Adhesives / Q000494:pharmacology*; D014357:Trypsin / Q000494:pharmacology
chemical_list: D003432:Cross-Linking Reagents; D006025:Glycosaminoglycans; D014014:Tissue Adhesives; D003094:Collagen; D014357:Trypsin; D010434:Pepsin A; D019791:Guanidine