Morphological alterations in dental and periodontal tissues in murine mucopolysaccharidosis type VII

Mucopolysaccharidoses (MPSs) in humans are frequently associated with tooth and periodontal aberrations. Although the cause is known, namely, enzyme deficiency, the pathophysiology of these alterations is not well defined. A murine MPS VII (beta-glucuronidase deficiency) model has earlier been identified with morphological, genetic, and biochemical characteristics that closely mimic those of human MPS VII. The present investigation describes the histopathological alterations in dental and periodontal tissues from such mutant mice. Homozygous animals were identified by external phenotypical features and as being beta-glucuronidase deficient by a fluorometric assay of liver samples. In the incisor and the periodontium, abnormalities were evident in both cells and the extracellular matrices. Mesenchyme-derived cells were more aberrant than epithelial cells. Moreover, undifferentiated cells appeared unaffected, whereas actively synthesizing and resorbing cells were distended by virtually empty or granular material-containing vacuoles, the content presumably being glycosaminoglycans. The cells most affected were those in which macromolecular turnover is normally the highest, namely, odontoblasts, postsecretory ameloblasts, and periodontal ligament fibroblasts. Extracellularly, predentin displayed abnormal collagen fibrils, whereas mineralization defects occurred in both dentin and enamel. This murine model of MPS VII provides a good tool for understanding the pathophysiology of this disease in bone, periodontium, and teeth.