Myocardial Mechanics and Collagen Structure in the Osteogenesis Imperfecta Murine ( oim )

Abstract —Because the amount and structure of type I collagen are thought to affect the mechanics of ventricular myocardium, we investigated myocardial collagen structure and passive mechanical function in the osteogenesis imperfecta murine ( oim ) model of pro-α2(I) collagen deficiency, previously shown to have less collagen and impaired biomechanics in tendon and bone. Compared with wild-type littermates, homozygous oim hearts exhibited 35% lower collagen area fraction ( P P P oim left ventricular (LV) collagen concentration was 45% lower ( P P oim than wild-type ( P =NS). Uniaxial stress-strain relations in resting right ventricular papillary muscles exhibited 60% greater strains ( P P =0.05), and 64% higher nonlinearity ( P oim . Mean opening angle, after relief of residual stresses in resting LV myocardium, was 121±9 degrees in oim compared with 45±4 degrees in wild-type ( P oim was 23±8 degrees greater than wild-type ( P oim is associated with significantly decreased fiber and chamber stiffness despite modestly increased collagen cross-linking. Altered myofiber angles and residual stress may be beneficial adaptations to these mechanical alterations to maintain uniformity of transmural fiber strain. In addition to supporting and organizing myocytes, myocardial collagen contributes directly to ventricular stiffness at high and low loads and can influence stress-free state and myofiber architecture.