MINERAL CHANGES IN A TRANSGENIC MOUSE MODEL FOR OSTEOGENESIS IMPERFECTA

A line of transgenic mice has been investigated that expressed moderat e levels of an internally human gene for the pro alpha 1(I) chain of t ype I procollagen to determine if they would make a good model for ost eogenesis imperfecta (brittle bone disease). Previous workers have rep orted extensive fracturing in these mice, with femurs that were shorte r and bone that had decreased ash weight, mineral and collagen content . These workers demonstrated increased brittleness in the bone by biom echanical measurements. The molar calcium to phosphorus ratio in bone from patients with osteogenesis imperfecta. Bone from both transgenic and normal littermate mice was examined to determine if any similarity with the data for human osteogenesis imperfecta could be drawn. X-ray microanalysis of bone mineral demonstrated a lower calcium to phospho rus molar ratio in transgenic mouse bone than in normal littermates. F ourier-transform infra-red spectroscopy confirmed that the mineral pre sent was apatitic in nature despite the lower calcium to phosphorus mo lar ratio. Multiple fracture calluses were present on the ribs and on the long bones of the transgenic mice; this was absent in normal litte rmates. This mouse model may lead to a better understanding of the und erlying pathology resulting in fragile bones in osteogenesis imperfect a.