Type I Collagen Homotrimer Alters the Intrinsic and Viscoelastic Tensile Properties of Tendon
Type I Collagen Homotrimer Alters the Intrinsic and Viscoelastic Tensile Properties of Tendon
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Original abstract
Type I collagen homotrimer accumulation is associated with human age-related musculoskeletal, cardiovascular and fibrotic diseases — in addition to cancer — due to over-production of the alpha-1(I) chain from COL1A1, or inactivation of COL1A2. Type I collagen homotrimer in the osteogenesis imperfecta model oim does not cause bone fragility but exacerbates the oim phenotype. Col1a2 null males have altered Mendelian inheritance and age-related deterioration. Here Col1a2 null and oim tail tendons were analysed to elucidate the role of collagen homotrimer in soft collagenous tissues. Homozygotes of both lines produced homotrimeric type I collagen, with evidence of type I collagen homotrimer in Col1a2 null heterozygotes. Collagen fibril diameters were thinner in oim homozygotes, but not in Col1a2 null. Tail tendons were thinner in Col1a2 null females at 8 and 18 weeks, and in oim homozygotes at 18 weeks. Failure stress and maximum modulus decreased in Col1a2 null homozygotes at 52 weeks old whilst failure strain increased. Strain at maximum modulus increased in oim heterozygotes and Col1a2 null homozygotes at 18 weeks, and in Col1a2 null heterozygotes and homozygotes at 52 weeks. Hysteresis was reduced in oim homozygotes at 8 weeks whilst a pronounced and consistent attenuation in the rate of change of stress was observed in oim homozygotes at 18 weeks and in Col1a2 null homozygotes and heterozygotes at 18 and 52 weeks. The results demonstrate that type I collagen heterotrimer modulates the time-dependent response to loading. There is a reduced resilience to mechanical loading beyond adolescence when the homotrimeric form is present.