Abstract
Evaluation of the skin phenotype in osteogenesis imperfecta (OI) typically involves biochemical measurements, such as histologic or biochemical assessment of the collagen produced from biopsy-derived dermal fibroblasts. As an alternative, the current study utilized non-invasive magnetic resonance imaging (MRI) microscopy and optical spectroscopy to define biophysical characteristics of skin in an animal model of OI. MRI of skin harvested from control, homozygous oim/oim and heterozygous oim/+ mice demonstrated several differences in anatomic and biophysical properties. Fourier transform infrared imaging spectroscopy (FT-IRIS) was used to interpret observed MRI signal characteristics in terms of chemical composition. Differences between wild-type and OI mouse skin included the appearance of a collagen-depleted lower dermal layer containing prominent hair follicles in the oim/oim mice, accounting for 55% of skin thickness in these. The MRI magnetization transfer rate was lower by 50% in this layer as compared to the upper dermis, consistent with lower collagen content. The MRI transverse relaxation time, T2, was greater by 30% in the dermis of the oim/oim mice compared to controls, consistent with a more highly hydrated collagen network. Similarly, an FT-IRIS-defined measure of collagen integrity was 30% lower in the oim/oim mice. We conclude that characterization of phenotypic differences between the skin of OI and wild-type mice by MRI and FT-IRIS is feasible, and that these techniques provide powerful complementary approaches for the analysis of the skin phenotype in animal models of disease.