1. Disruption of biomineralization pathways in spinal tissues of a mouse model of diffuse idiopathic skeletal hyperostosis.
- Author
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Ii H, Warraich S, Tenn N, Quinonez D, Holdsworth DW, Hammond JR, Dixon SJ, and Séguin CA
- Subjects
- 2-Chloroadenosine metabolism, Alkaline Phosphatase metabolism, Animals, Annulus Fibrosus, Calcinosis genetics, Calcinosis pathology, Cells, Cultured, Disease Models, Animal, Equilibrative Nucleoside Transporter 1 metabolism, Female, Gene Expression Regulation, Hyperostosis, Diffuse Idiopathic Skeletal diagnostic imaging, Intervertebral Disc diagnostic imaging, Intervertebral Disc pathology, Intervertebral Disc physiopathology, Male, Mice, Inbred C57BL, Sex Characteristics, Spine diagnostic imaging, X-Ray Microtomography, Calcification, Physiologic genetics, Hyperostosis, Diffuse Idiopathic Skeletal pathology, Hyperostosis, Diffuse Idiopathic Skeletal physiopathology, Spine pathology, Spine physiopathology
- Abstract
Equilibrative nucleoside transporter 1 (ENT1) mediates passage of adenosine across the plasma membrane. We reported previously that mice lacking ENT1 (ENT1(-/-)) exhibit progressive ectopic mineralization of spinal tissues resembling diffuse idiopathic skeletal hyperostosis (DISH) in humans. Here, we investigated mechanisms underlying aberrant mineralization in ENT1(-/-) mice. Micro-CT revealed ectopic mineralization of spinal tissues in both male and female ENT1(-/-) mice, involving the annulus fibrosus of the intervertebral discs (IVDs) of older mice. IVDs were isolated from wild-type and ENT1(-/-) mice at 2months of age (prior to disc mineralization), 4, and 6months of age (disc mineralization present) and processed for real-time PCR, cell isolation, or histology. Relative to the expression of ENTs in other tissues, ENT1 was the primary nucleoside transporter expressed in wild-type IVDs and mediated the functional uptake of [(3)H]2-chloroadenosine by annulus fibrosus cells. No differences in candidate gene expression were detected in IVDs from ENT1(-/-) and wild-type mice at 2 or 4months of age. However, at 6months of age, expression of genes that inhibit biomineralization Mgp, Enpp1, Ank, and Spp1 were reduced in IVDs from ENT1(-/-) mice. To assess whether changes detected in ENT1(-/-) mice were cell autonomous, annulus fibrosus cell cultures were established. Compared to wild-type cells, cells isolated from ENT1(-/-) IVDs at 2 or 6months of age demonstrated greater activity of alkaline phosphatase, a promoter of biomineralization. Cells from 2-month-old ENT1(-/-) mice also showed greater mineralization than wild-type. Interestingly, altered localization of alkaline phosphatase activity was detected in the inner annulus fibrosus of ENT1(-/-) mice in vivo. Alkaline phosphatase activity, together with the marked reduction in mineralization inhibitors, is consistent with the mineralization of IVDs seen in ENT1(-/-) mice at older ages. These findings establish that both cell-autonomous and systemic mechanisms contribute to ectopic mineralization in ENT1(-/-) mice., (Copyright © 2016 Elsevier Inc. All rights reserved.)
- Published
- 2016
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