Impaired 1,25-dihydroxyvitamin D3 action underlies enthesopathy development in the Hyp mouse model of X-linked hypophosphatemia
Rakshya Rana, … , Shaza Almardini, Eva S. Liu
Rakshya Rana, … , Shaza Almardini, Eva S. Liu
Published July 25, 2023
Citation Information: JCI Insight. 2023;8(17):e163259. https://doi.org/10.1172/jci.insight.163259.
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Research Article Endocrinology

Impaired 1,25-dihydroxyvitamin D3 action underlies enthesopathy development in the Hyp mouse model of X-linked hypophosphatemia

Abstract

X-linked hypophosphatemia (XLH) is characterized by high serum fibroblast growth factor 23 (FGF23) levels, resulting in impaired 1,25-dihydroxyvitamin D3 (1,25D) production. Adults with XLH develop a painful mineralization of the tendon-bone attachment site (enthesis), called enthesopathy. Treatment of mice with XLH (Hyp) with 1,25D or an anti–FGF23 Ab, both of which increase 1,25D signaling, prevents enthesopathy. Therefore, we undertook studies to determine a role for impaired 1,25D action in enthesopathy development. Entheses from mice lacking vitamin D 1α-hydroxylase (Cyp27b1) (C–/–) had a similar enthesopathy to Hyp mice, whereas deletion of Fgf23 in Hyp mice prevented enthesopathy, and deletion of both Cyp27b1 and Fgf23 in mice resulted in enthesopathy, demonstrating that the impaired 1,25D action due to high FGF23 levels underlies XLH enthesopathy development. Like Hyp mice, enthesopathy in C–/– mice was observed by P14 and was prevented, but not reversed, with 1,25D therapy. Deletion of the vitamin D receptor in scleraxis-expressing cells resulted in enthesopathy, indicating that 1,25D acted directly on enthesis cells to regulate enthesopathy development. These results show that 1,25D signaling was necessary for normal postnatal enthesis maturation and played a role in XLH enthesopathy development. Optimizing 1,25D replacement in pediatric patients with XLH is necessary to prevent enthesopathy.

Authors

Rakshya Rana, Jiana T. Baker, Melissa Sorsby, Supriya Jagga, Shreya Venkat, Shaza Almardini, Eva S. Liu

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Figure 8

1,25D blocks rhGDF5 induced expression of BMP and IHH genes and p-SMAD1/5 and VDR expression is decreased in Hyp entheses by P14.

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1,25D blocks rhGDF5 induced expression of BMP and IHH genes and p-SMAD1/...
(A) Primary murine chondrocytes were pretreated for 0.5, 1, 4, or 18 hours with or without (–) 1 × 10–8 M 1,25D prior to incubation with (+) or without (–) 100 ng/mL rhGDF5 (for 30 minutes) and subjected to Western blot analyses for p-SMAD1/5/9, SMAD1, and β-actin. Data are representative of those obtained from 3 independent experiments. (B) Primary murine chondrocytes were pretreated for 18 hours with 1 × 10–8 M 1,25D followed by treatment with 200 ng/mL rhGDF5 (for 4 hours). Gene expression analyses were performed for BMP and IHH target genes. Data are representative of those obtained from 5–7 independent experiments. One-way ANOVA followed by Fisher’s least significant difference test was used to analyze significance between all genotype groups. *P < 0.05 versus WT; #P < 0.05 versus rhGDF5; a indicates P < 0.05 versus rhGDF5 plus 1,25D. (C) IHC for VDR was performed on P7, P14, P30, and P60 entheses from WT, Hyp, and C–/– mice. In all representative pictures, the enthesis region is outlined with a black box. Scale bar: 20 μm. Data are representative of 6 mice per age or genotype group.