Le Henaff Carole, Faria Da Cunha Mélanie, Hatton Aurélie, Tondelier Danielle, Marty Caroline, Collet Corinne, Zarka Mylène, Geoffroy Valérie, Zatloukal Kurt, Laplantine Emmanuel, Edelman Aleksander, Sermet-Gaudelus Isabelle, Marie Pierre J
INSERM UMR-1132, Paris, France, University Paris Diderot, Sorbonne Paris Cité, Paris, France.
INSERM U-1151, Team 2, University Paris Descartes, Paris, France.
Hum Mol Genet. 2016 Apr 1;25(7):1281-93. doi: 10.1093/hmg/ddw009. Epub 2016 Jan 13.
Patients with cystic fibrosis (CF) display low bone mass and alterations in bone formation. Mice carrying the F508del genetic mutation in the cystic fibrosis conductance regulator (Cftr) gene display reduced bone formation and decreased bone mass. However, the underlying molecular mechanisms leading to these skeletal defects are unknown, which precludes the development of an efficient anti-osteoporotic therapeutic strategy. Here we report a key role for the intermediate filament protein keratin 8 (Krt8), in the osteoblast dysfunctions in F508del-Cftr mice. We found that murine and human osteoblasts express Cftr and Krt8 at low levels. Genetic studies showed that Krt8 deletion (Krt8(-/-)) in F508del-Cftr mice increased the levels of circulating markers of bone formation, corrected the expression of osteoblast phenotypic genes, promoted trabecular bone formation and improved bone mass and microarchitecture. Mechanistically, Krt8 deletion in F508del-Cftr mice corrected overactive NF-κB signaling and decreased Wnt-β-catenin signaling induced by the F508del-Cftr mutation in osteoblasts. In vitro, treatment with compound 407, which specifically disrupts the Krt8-F508del-Cftr interaction in epithelial cells, corrected the abnormal NF-κB and Wnt-β-catenin signaling and the altered phenotypic gene expression in F508del-Cftr osteoblasts. In vivo, short-term treatment with 407 corrected the altered Wnt-β-catenin signaling and bone formation in F508del-Cftr mice. Collectively, the results show that genetic or pharmacologic targeting of Krt8 leads to correction of osteoblast dysfunctions, altered bone formation and osteopenia in F508del-Cftr mice, providing a therapeutic strategy targeting the Krt8-F508del-CFTR interaction to correct the abnormal bone formation and bone loss in cystic fibrosis.
囊性纤维化（CF）患者表现出低骨量和骨形成改变。在囊性纤维化跨膜传导调节因子（Cftr）基因中携带F508del基因突变的小鼠骨形成减少且骨量降低。然而，导致这些骨骼缺陷的潜在分子机制尚不清楚，这阻碍了有效的抗骨质疏松治疗策略的开发。在此，我们报告中间丝蛋白角蛋白8（Krt8）在F508del-Cftr小鼠成骨细胞功能障碍中起关键作用。我们发现小鼠和人类成骨细胞低水平表达Cftr和Krt8。遗传学研究表明，F508del-Cftr小鼠中Krt8缺失（Krt8(-/-)）可增加骨形成循环标志物水平，纠正成骨细胞表型基因的表达，促进小梁骨形成并改善骨量和微结构。从机制上讲，F508del-Cftr小鼠中Krt8缺失可纠正成骨细胞中由F508del-Cftr突变诱导的过度活跃的NF-κB信号传导并降低Wnt-β-连环蛋白信号传导。在体外，用化合物407处理可特异性破坏上皮细胞中的Krt8-F508del-Cftr相互作用，纠正F508del-Cftr成骨细胞中异常的NF-κB和Wnt-β-连环蛋白信号传导以及改变的表型基因表达。在体内，用407短期治疗可纠正F508del-Cftr小鼠中改变的Wnt-β-连环蛋白信号传导和骨形成。总体而言，结果表明对Krt8进行基因或药物靶向可导致F508del-Cftr小鼠中成骨细胞功能障碍、骨形成改变和骨质减少得到纠正，为针对Krt8-F508del-CFTR相互作用以纠正囊性纤维化中异常骨形成和骨质流失提供了一种治疗策略。
