Genetic etiology and dental pulp cell deficiency of hypophosphatasia

Hypophosphatasia is caused by mutations of the tissue-non-specific alkaline phosphatase (TNSALP) gene with deficiency of dentin structure. The aim of this study was to examine whether TNSALP mutation in dental pulp cells contributes to dentin dysplasia in hypophosphatasia. Mutation analysis showed that compound heterozygous mutations of TNSALP were identified in three hypophosphatasia patients, including 3 novel mutation sites. Exfoliated teeth from the patients showed abnormal dentin mineralization and loss of cementum, as assessed by ground sections and scanning electron microscope analysis. Dental pulp cells isolated from one of the patients showed a significantly reduced TNSALP activity and mineralization capacity when compared with those in dental pulp cells from the unaffected individuals. Our results suggested that dentin dysplasia in hypophosphatasia may be associated with the decreased mineralization ability of dental pulp cells.