The Characterization of the Rat Bone Sialoprotein Knockout Phenotype
Abstract
Bone sialoprotein (BSP) is an extracellular phosphoprotein that has been associated with mineralizing tissues, such as the periodontium, the fibrocartilaginous enthesis, and long bone formation. In this study, we characterized the phenotype of BSP-deficient rats. Histomorphometric analysis discovered a thinning of the acellular cementum in both 20 and 50 week-old Bsp-/- rats with no related periodontal defects and an organized periodontal ligament. Analysis of the mature quadriceps tendon (QCT) enthesis determined that BSP and osteopontin are present in the calcified fibrocartilage of wild-type rats at 14 weeks. The developing QCT enthesis of Bsp-/- rats appears similar in mineral content, collagen organization, and morphology when compared to wild-type counterparts. Digital measurements of rat tibiae show that bone length does not differ between wild-type and Bsp-/- rats at day of birth. The results of this study suggest that BSP is present in the periodontal and enthesis tissues of the rat, but the rat displays less severe phenotypes than the Bsp-/-mouse.