title: Integrative cartilage repair: inhibition by beta-aminopropionitrile.
abstract: The effects of beta-aminopropionitrile, a known inhibitor of lysyl oxidase, on the extractability of newly synthesized collagen and integrative cartilage repair were determined in explant cultures of adult bovine articular cartilage. Dose-escalation studies indicated that treatment of cartilage explants for 6 days with beta-aminopropionitrile caused a dose-dependent inhibition of proteoglycan synthesis ([35S]sulfate incorporation) with a 50% inhibition at 2.2 mM. However, 0.25 mM beta-aminopropionitrile had no detectable effect on proteoglycan synthesis and was thus used for subsequent experiments. Treatment of cartilage with beta-aminopropionitrile for 14 days increased the extractability of newly synthesized collagen with 4 M guanidine-HCl while having little effect on proteoglycan synthesis, proteoglycan deposition, collagen synthesis (formation of [3H]hydroxyproline after labeling with [3H]proline), collagen deposition, or cartilage cellularity (DNA content). In untreated cultures, the percentage of radiolabeled collagen ([3H]hydroxyproline) that was extractable after 1 day of radiolabeling, 6 days of radiolabeling, or 6 days of label and 6 days of chase decreased from 81 to 25 and 9%, respectively. In beta-aminopropionitrile-treated cultures, the extractability was relatively higher (96, 62, and 47%, respectively). Treatment with beta-aminopropionitrile after radiolabeling with [14C]lysine also significantly inhibited the formation of the reducible crosslink [14C]dihydroxylysinonorleucine without affecting the overall deposition in cartilage of [14C]lysine and [14C]hydroxylysine. In functional repair studies, treatment with beta-aminopropionitrile caused an almost complete inhibition of integration between pairs of cartilage explants maintained in apposition for 2 weeks. These results indicate that beta-aminopropionitrile blocks the formation of collagen crosslinks in cartilage explants and suggest that such crosslinks are critical to integrative cartilage repair.
authors.affiliation: Department of Bioengineering, Institute for Biomedical Engineering, University of California-San Diego, La Jolla 92093-0412, USA.
authors.forename: T
authors.initials: T
authors.lastname: Ahsan
authors.forename: L M
authors.initials: LM
authors.lastname: Lottman
authors.forename: F
authors.initials: F
authors.lastname: Harwood
authors.forename: D
authors.initials: D
authors.lastname: Amiel
authors.forename: R L
authors.initials: RL
authors.lastname: Sah
mesh_terms: D000629:Aminopropionitrile / Q000494:pharmacology*; D000818:Animals; D001861:Bone Regeneration; D002358:Cartilage, Articular / Q000187:drug effects / Q000502:physiology*; D002417:Cattle; D003094:Collagen / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D005260:Female; D006909:Hydroxyproline / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D011509:Proteoglycans / Q000096:biosynthesis
chemical_list: D011509:Proteoglycans; D000629:Aminopropionitrile; D003094:Collagen; D008239:Lysine; D006909:Hydroxyproline