Pathogenesis of Multicentric Carpotarsal Osteolysis

摘要 多中心腕关节骨溶解综合征(MCTO)是一种常染色体显性遗传性疾病 使幼儿丧失行为能力，并很快导致危及生命的肾功能衰竭。因为它的变形， 它使人虚弱，而且经常危及生命，这是可以理解的，为什么它经常自发出现。这个 临床和放射学特征是腕部和踝部骨质破坏。肩部、肘部和膝部的骨骼 通常也会受到破坏性过程的影响。有时会出现全身性骨量减少症。在.期间 在过去的30年里，我们照顾了11名患有MCTO的无血缘关系的儿童。2012年，澳大利亚的一个研究小组 已报道的单外显子MAFB[v-MAF肌筋膜纤维肉瘤癌基因同源B]突变 (禽类)在13例MCTO先证者中。不久之后，我们报告了MAFB突变，证实了我们的患者队列 所有引起MCTO的MAFB突变都定位在反式激活结构域的一小部分。MAFB是一种 MAF转录因子家族的成员，驱动破骨细胞活性。然而，双膦酸盐， 抑制破骨细胞，并不是治疗MCTO的有效方法，这表明其他骨细胞也是 牵涉其中。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Dkk1) 在MCTO中，MMP3(在软骨细胞中表达)和MMP7显著升高 患者与年龄匹配的对照组。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是由缺陷的组合造成的 基质金属蛋白酶在软骨内成骨过程中细胞外基质的降解和2)过度 骨重建过程中破骨细胞驱动的骨溶解作用。我们已经开发出三种由患者衍生的 来自不同突变、种族和性别患者的诱导多能干细胞(IPS)细胞系。我们现在就会 利用CRISPR技术建立并验证三个等基因对照细胞系，以纠正MAFB突变。 然后我们将通过区分突变株来证明MAFB突变对细胞分化和功能的影响 IPSCs和同基因控制细胞分化为OBS、软骨细胞和OCS，并评估细胞分化和 功能。这将使患者来源的IPSC方法成为阐明其机制的可行方法。 MCTO的。这一点尤其重要，因为MCTO小鼠模型不会重现腕骨/颧骨 人类疾病中出现的骨质丢失。了解MCTO的机制有助于指导MCTO的发展 治疗。此外，患者来源的IPSCs和同基因对照细胞可用于筛选药物文库或 测试新的治疗方法。

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.