Studies of osteoclast pathogenesis of craniometaphyseal dysplasia (CMD) in a mouse model and in patient-specific IPS cells

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• 作者：I.-Ping Chen ; Liping Wang ; Keiichi Fukuda ; Noemi Fusaki ; Akihiro Iida ; Alexander Lichtler ; Ernst J. Reichenberger
• 刊名：Seminars in Arthritis and Rheumatism
• 出版年：2013
• 出版时间：April, 2013
• 年：2013
• 卷：42
• 期：5
• 页码：548-549
• 全文大小：56 K

文摘

Rare genetic bone disorders are of significant clinical relevance because of their number and their life-time debilitating impact on patients. Treatment options are often limited due to insufficient knowledge of their pathogenesis. Studies have been plagued by the unavailability of primary cells/tissues and suitable animal models. Patient-specific induced pluripotent stem (iPS) cells offer new avenues for studying bone cells from patients with rare diseases. We study craniometaphyseal dysplasia (CMD) utilizing a knock-in mouse model and patient-specific iPS cells. CMD is characterized by hyperostosis of craniofacial bones concurrent with widened metaphyses in long bones. Mutations for autosomal dominant CMD have been identified in the ANK gene (ANKH). A knock-in (KI) mouse model expressing a human Ank mutation (Phe377del) replicates many features of CMD. We observed defects in AnkKI/KI osteoclast (OC) cultures including (1) decreased OC formation; (2) reduced mineral resorption; (3) reduced OC migration shown by live-cell time-lapse imaging; and (4) altered podosome organization. The bone mass phenotype of AnkKI/KI mice is partially rescued by wild-type bone marrow transplants. We hypothesize that CMD-causing ANKH mutations decrease the osteoclast activity by negatively affecting the actin cytoskeleton. Our ultimate goal is to test this hypothesis in the human system using patient-specific inducible pluripotent stem cells (iPSCs). We derived iPSCs from peripheral blood mononuclear cells of CMD patients and healthy controls with four separate Sendai-virus vectors encoding OCT3/4, SOX2, KLF4, and c-MYC. The Sendai virus, a cytoplasmic RNA vector, can produce iPSCs free of vector integration into chromosomes. The pluripotency of these iPSCs is tested by (1) expression of hES cell markers; (2) embryoid body formation; and (3) teratoma formation and normal karyotypes are confirmed. iPSCs from a normal control have already been differentiated into multinucleated TRAP-positive OC-like cells. We are currently differentiating OCs from CMD iPSCs and comparing OCs derived from CMD to normal iPSCs. We expect that combining mouse data with findings from human iPS cells will significantly increase our understanding of the CMD pathology. If successful, I believe that this model can serve as paradigm to study other rare genetic skeletal disorders.