Research Unit Analytical Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
Department of Biomedical Sciences, University of Veterinary Medicine, Vienna, Austria.
JCI Insight. 2022 Oct 24;7(20):e162138. doi: 10.1172/jci.insight.162138.
Patients with the renal phosphate-wasting disease X-linked hypophosphatemia (XLH) and Hyp mice, the murine homolog of XLH, are characterized by loss-of-function mutations in phosphate-regulating endopeptidase homolog X-linked (PHEX), leading to excessive secretion of the bone-derived phosphotropic hormone FGF23. The mineralization defect in patients with XLH and Hyp mice is caused by a combination of hypophosphatemia and local accumulation of mineralization-inhibiting molecules in bone. However, the mechanism by which PHEX deficiency regulates bone cell metabolism remains elusive. Here, we used spatial metabolomics by employing matrix-assisted laser desorption/ionization (MALDI) Fourier-transform ion cyclotron resonance mass spectrometry imaging (MSI) of undecalcified bone cryosections to characterize in situ metabolic changes in bones of Hyp mice in a holistic, unbiased manner. We found complex changes in Hyp bone metabolism, including perturbations in pentose phosphate, purine, pyrimidine, and phospholipid metabolism. Importantly, our study identified an upregulation of several biochemical pathways involved in intra- and extracellular production of the mineralization inhibitor pyrophosphate in the bone matrix of Hyp mice. Our data emphasize the utility of MSI-based spatial metabolomics in bone research and provide holistic in situ insights as to how Phex deficiency-induced changes in biochemical pathways in bone cells are linked to impaired bone mineralization.
患有肾脏磷酸盐丢失性疾病 X 连锁低磷血症 (XLH) 和 Hyp 小鼠的患者,其为 XLH 的鼠类同源物,其特征是磷酸盐调节内肽酶同源物 X 连锁 (PHEX) 的功能丧失性突变,导致骨源性磷酸化激素 FGF23 的过度分泌。XLH 和 Hyp 小鼠患者的矿化缺陷是由低磷血症和骨内矿化抑制分子的局部积累共同引起的。然而,PHEX 缺乏如何调节骨细胞代谢的机制仍不清楚。在这里,我们使用空间代谢组学,通过对未经脱钙的骨冷冻切片进行基质辅助激光解吸/电离 (MALDI) 傅里叶变换离子回旋共振质谱成像 (MSI),以整体、无偏倚的方式描述 Hyp 小鼠骨内原位代谢变化。我们发现 Hyp 骨代谢发生复杂变化,包括戊糖磷酸、嘌呤、嘧啶和磷脂代谢的紊乱。重要的是,我们的研究鉴定出矿化抑制剂焦磷酸盐在 Hyp 小鼠骨基质中细胞内和细胞外产生的几个生化途径的上调。我们的数据强调了基于 MSI 的空间代谢组学在骨研究中的应用,并提供了关于 Phex 缺乏诱导的骨细胞内生化途径变化如何与骨矿化受损相关的整体原位见解。