COLLAGEN FROM THE OSTEOGENESIS IMPERFECTA MOUSE MODEL (OIM) SHOWS REDUCED RESISTANCE AGAINST TENSILE-STRESS

Osteogenesis imperfecta (OI) is a disease attributable to any of a lar ge number of possible mutations of type I collagen, The disease is cli nically characterized in part by highly brittle bone, the cause of thi s feature being unknown. Recently a mouse model of OI, designated as o steogenesis imperfecta murine (oim) and having a well defined genetic mutation, has been studied and found to contain mineral crystals diffe rent in their alignment with respect to collagen and in their size, Th ese observations are consistent with those reported in human OI and th e unusual crystal alignment and size undoubtedly contribute to the red uced mechanical properties of OI bone, While the mineral has been inve stigated, no information is available on the tensile properties of oim collagen. In this study, the mechanical properties of tendon collagen under tension have been examined for homozygous (oim/oim), heterozygo us (+/oim), and control (+/+) mice under native wet conditions, The ul timate stress and strain found for oim/oim collagen were only about ha lf the values for control mice, Assuming that prestrained collagen mol ecules carry most of the tensile load in normal bone while the mineral confers rigidity and compression stability, the reported results sugg est that the brittleness of OI bone in the mouse model may be related to a dramatic reduction of the ultimate tensile strain of the collagen .