IADR Abstract Archives
Ectopic Calcification of the Mandibular Symphysis in Mice Lacking ENT1
Objectives: Equilibrative nucleoside transporter 1 (ENT1) transfers nucleosides, such as adenosine, across plasma membranes. We reported previously that mice lacking ENT1 (ENT1-KO) exhibit progressive ectopic calcification of spinal tissues – a phenotype resembling diffuse idiopathic skeletal hyperostosis (DISH) in humans. Our objective was to investigate the calcification of orofacial tissues in ENT1-KO mice.
Methods: Heads of male wild-type (WT) and ENT1-KO mice from 3 to 17 months of age were removed post-mortem, fixed in paraformaldehyde, and scanned using high-resolution micro-computed tomography (micro-CT). Some specimens were decalcified and processed for standard histological assessments. Calcified lesions in selected samples were examined using energy dispersive X-ray spectroscopy (EDX) and micro X-ray diffraction (µXRD).
Results: Using micro-CT, no obvious differences were observed between ENT1-KO and WT mice in the enamel, dentin, cementum, periodontal ligament or temporomandibular joint at all ages. In contrast, by 6 months of age, ENT1-KO mice showed dramatic ectopic calcification of the connective tissues within the mandibular symphysis. Lesions appeared expansile, enlarging with age and associated with apparent resorption of the adjacent alveolar bone. Histology showed disorganization and hyperplasia of the connective tissues within the symphysis evident as early as 3 months of age. EDX of lesions at 8 months of age revealed large amounts of calcium and phosphorous in a molar ratio of ~1.5, with hydroxyapatite detected by µXRD.
Conclusions: This is the first report that ENT1-KO mice develop progressive ectopic calcification of the mandibular symphysis. These lesions develop in a reproducible temporal pattern within a well-defined, localized anatomical site. Thus, further studies of the cellular and molecular events occurring within the mandibular symphysis of ENT1-KO mice may provide valuable insights into the pathogenesis of ectopic calcification in DISH and related disorders.
Methods: Heads of male wild-type (WT) and ENT1-KO mice from 3 to 17 months of age were removed post-mortem, fixed in paraformaldehyde, and scanned using high-resolution micro-computed tomography (micro-CT). Some specimens were decalcified and processed for standard histological assessments. Calcified lesions in selected samples were examined using energy dispersive X-ray spectroscopy (EDX) and micro X-ray diffraction (µXRD).
Results: Using micro-CT, no obvious differences were observed between ENT1-KO and WT mice in the enamel, dentin, cementum, periodontal ligament or temporomandibular joint at all ages. In contrast, by 6 months of age, ENT1-KO mice showed dramatic ectopic calcification of the connective tissues within the mandibular symphysis. Lesions appeared expansile, enlarging with age and associated with apparent resorption of the adjacent alveolar bone. Histology showed disorganization and hyperplasia of the connective tissues within the symphysis evident as early as 3 months of age. EDX of lesions at 8 months of age revealed large amounts of calcium and phosphorous in a molar ratio of ~1.5, with hydroxyapatite detected by µXRD.
Conclusions: This is the first report that ENT1-KO mice develop progressive ectopic calcification of the mandibular symphysis. These lesions develop in a reproducible temporal pattern within a well-defined, localized anatomical site. Thus, further studies of the cellular and molecular events occurring within the mandibular symphysis of ENT1-KO mice may provide valuable insights into the pathogenesis of ectopic calcification in DISH and related disorders.
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