Osteogenic disorder shionogi (ODS) rats carry a hereditary defect in
ascorbic acid synthesis, mimicking human
scurvy when fed with an
ascorbic acid-deficient (aa-
def) diet. As aa-
def ODS rats were shown to feature disordered bone formation, we have examined the bone mineralization in this rat model. A fibrous tissue layer surrounding the trabeculae of tibial metaphyses was found in aa-
def ODS rats, and this layer showed intense
alkaline phosphatase activity and
proliferating cell nuclear antigen-immunopositivity. Many osteoblasts detached from the bone surfaces and were characterized by round-shaped rough endoplasmic reticulum (rER), suggesting accumulation of malformed
collagen inside the rER. Accordingly, fine, fragile fibrillar collagenous structures without evident striation were found in aa-
def bones, which may result from misassembling of the triple helices of collagenous α-chains. Despite a marked reduction in bone formation,
ascorbic acid deprivation seemed to have no effect on mineralization: while reduced in number, normal matrix vesicles and mineralized nodules could be seen in aa-
def bones. Fine needle-like
mineral crystals extended from these mineralized nodules, and were apparently bound to collagenous fibrillar structures. In summary,
collagen mineralization seems unaffected by
ascorbic acid deficiency in spite of the fine, fragile collagenous fibrils identified in the bones of our animal model.