Pathogenesis of Multicentric Carpotarsal Osteolysis

摘要 多中心腕跗骨溶解综合征（MCTO）是一种常染色体显性遗传疾病， 使幼儿丧失能力，并在不久后导致危及生命的肾衰竭。由于它的变形， 它是一种使人衰弱，并经常危及生命的性质，可以理解为什么它经常自发出现。的 临床和放射学特征是腕骨-跗骨破坏。肩膀、肘部和膝盖的骨头 通常也会受到破坏性过程的影响。有时有全身性骨质减少。期间 在过去的30年里，我们已经照顾了11名无血缘关系的MCTO儿童。2012年，一个澳大利亚研究小组 已报告单外显子MAFB [v-maf肌肉腱膜纤维肉瘤癌基因直系同源物B]内的突变 （禽）]。不久之后，我们报告了我们患者队列的MAFB突变，证实了 所有导致MCTO的MAFB突变都定位于反式激活结构域的一个小区域。MAFB是一个 是MAF转录因子家族的成员，并驱动破骨细胞活性。然而，双膦酸盐， 抑制破骨细胞，不是MCTO的有效治疗方法，这表明其他骨细胞也是 涉案我们的初步数据显示，成骨细胞的血清生物标志物（骨钙素、SOST和DKK 1） MCTO组软骨细胞MMP 3和MMP 7表达明显降低， 年龄匹配的对照组。因此，我们认为成骨细胞和软骨细胞也是 受MCTO中MAFB突变的影响。我们假设MCTO是由以下因素的组合导致的：1）缺陷 在软骨内骨形成期间MMP驱动的细胞外基质降解和2）过度 骨重建过程中破骨细胞驱动的骨溶解。我们已经开发了三种患者衍生的 来自具有不同突变、种族和性别的患者的诱导多能干（iPS）细胞系。我们现在将 使用CRISPR技术开发和验证三种同基因对照细胞系，以纠正MAFB突变。 然后，我们将证明MAFB突变通过分化突变体来影响细胞分化和功能， iPSC和同基因对照细胞分化为OB、软骨细胞和OC，并评估细胞分化， 功能这将建立患者来源的iPSC方法作为阐明机制的可行方法。 关于MCTO这是特别重要的，因为MCTO小鼠模型不重现腕/跗骨 在人类疾病中看到的骨质流失。了解MCTO的作用机制，将有助于指导MCTO的发展， 治疗此外，患者来源的iPSC和同基因对照细胞可用于筛选药物文库或药物组合物。 测试新疗法

Abstract Multicentric carpotarsal osteolysis syndrome (MCTO) is an autosomal dominant disorder that incapacitates young children and leads to life-threatening renal failure soon after. Because of its deforming, debilitating, and frequently life-threatening nature, it is understandable why it often arises spontaneously. The clinical and radiographic hallmark is carpal–tarsal bone destruction. Bones in the shoulders, elbows, and knees are also commonly affected by the destructive process. Sometimes there is generalized osteopenia. During the past 30 years, we have cared for eleven unrelated children with MCTO. In 2012, an Australian research group reported mutations within single-exon MAFB [v-maf musculoaponeurotic fibrosarcoma oncogene ortholog B (avian)] in 13 probands with MCTO. Soon after, we reported MAFB mutations for our patient cohort confirming that all MAFB mutations causing MCTO localize to a small region of the transactivation domain. MAFB is a member of the MAF family of transcription factors, and drives osteoclast activity. However, bisphosphonates, which inhibit osteoclasts, are not an effective treatment for MCTO, suggesting other bone cells are also involved. Our preliminary data showed that serum biomarkers for osteoblasts (osteocalcin, SOST, and DKK1) were significantly decreased and MMP3 (expressed in chondrocytes) and MMP7 were elevated in MCTO patients vs. age-matched controls. Therefore, we believe that both osteoblasts and chondrocytes are also affected by MAFB mutation in MCTO. We hypothesize that MCTO results from a combination of 1) defective MMP-driven degradation of the extracellular matrix during endochondral bone formation and 2) excessive osteoclast-driven osteolysis during bone remodeling. We have already developed three patient-derived induced pluripotent stem (iPS) cell lines from patients with different mutations, race, and sex. We will now develop and validate three isogenic control cell lines using CRISPR technology to correct the MAFB mutations. We will then demonstrate that MAFB mutations impact cell differentiation and function by differentiating mutant iPSCs and isogenic control cells into OBs, chondrocytes, and OCs and assessing cell differentiation and function. This will establish the patient-derived iPSC approach as a viable method to elucidate the mechanism of MCTO. This is especially important because the MCTO mouse model does not recapitulate the carpal/tarsal bone loss seen in the human disease. Understanding the mechanism of MCTO will help guide development of therapies. Further, the patient-derived iPSCs and isogenic control cells can be used to screen drug libraries or test new therapies.