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Mechanistic and Therapeutic Studies of Autosomal Dominant Osteopetrosis

常染色体显性骨石症的机制和治疗研究

基本信息

批准号：
10088411
负责人：
Michael J Econs
金额：
$ 33.61万
依托单位：
INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
依托单位国家：
美国
项目类别：
财政年份：
2017
资助国家：
美国
起止时间：
2017-02-01 至 2023-01-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10088411
关键词：
Adenylate Cyclase Adult Affect Age Age-Months Albers-Schonberg disease Back Blindness Bone Density Bone Diseases Bone Marrow Cell Transplantation Bone Marrow Transplantation Bone Resorption Bone necrosis Cell Surface Proteins Cell membrane Cells Chloride Channels Chloroquine Clinical Cyclic AMP Cyclophosphamide Defect Development Disease Disease model Dominant-Negative Mutation Dose Family Forskolin Fracture Functional disorder Gene Mutation Genes Human Impairment In Vitro Individual Jaw Knock-in Mouse Lead Lysosomes Maxilla Measures Missense Mutation Modeling Monitor Mus Mutant Strains Mice Mutation Osteoclasts Osteomyelitis Pancytopenia Pathway interactions Patients Pharmacology Phenotype Recycling Serum Severities Severity of illness Sorting - Cell Movement Testing Therapeutic Therapeutic Effect Therapeutic Studies bone bone resorbing activity disease phenotype experimental study genetic strain human disease improved in vivo inhibitor/antagonist insight late endosome mouse model mutant novel phosphodiesterase IV skeletal success trafficking young adult

项目摘要

Abstract Autosomal dominant osteopetrosis type 2 (ADO2) is an osteosclerotic disorder resulting from missense mutations in the Chloride Channel 7 gene (CLCN7), which cause defects in osteoclastic bone resorption by a dominant negative mechanism. Disease severity varies widely, even within the same family, and one third of individuals with mutations are asymptomatic carriers. However, of the two thirds who are affected by the disease (ADO2 patients), all have high bone mineral density with at least one clinical manifestation including fracture, osteonecrosis (particularly of the jaw and/or maxilla), osteomyelitis, blindness, and/or bone marrow failure. To investigate the pathophysiology of the disease and to perform “proof of principle” experiments to treat the disease we created a novel ADO2 “knock-in” mouse with a disease causing G213R mutation in the Clcn7 gene. We found that phenotypic severity differs among genetic strains and the ADO2 mouse on the129 background (used in this proposal) is an excellent model of moderate disease [bone volume per total volume (BV/TV) 2-fold over WT at 12 weeks of age, due primarily to osteoclast dysfunction]. To begin to understand the mechanism, we examined intracellular trafficking in WT and ADO2 osteoclasts which revealed defects in early endosomal trafficking, which is necessary for sorting internalized cell surface proteins into late endosomes and lysosomes, or recycling them back to the plasma membrane. In addition, we found that the pharmacologic agents, chloroquine, which modulates early endosomal trafficking, and forskolin and roflumilast, which increase intracellular cAMP by different mechanisms, enhance the bone-degrading activity of ADO2 osteoclasts. Our hypotheses are: 1) The bone-resorbing activity of ADO2 osteoclasts can be functionally restored by modulating either endosomal trafficking or increasing intracellular cAMP levels; 2) Chloroquine treatment will rescue the phenotype of the ADO2 mouse in young (6 weeks) and adult (9 months) mice; 3) Discontinuation of chloroquine therapy in ADO2 mice will result in an increase in BV/TV, as measured by in vivo µCT, but not at an accelerated rate and not to a degree similar to that of age-matched vehicle treated mutant mice; and 4) Bone marrow transplantation (BMT) will reverse the skeletal defects in ADO2 mice when performed either early (6 weeks of age) or late (9 months of age) in the disease course. Successful completion of the proposed aims may provide proof of principle that low dose chloroquine and BMT will substantially improve or fully rescue the ADO2 phenotype in a mouse model that mimics the human disease. Young and adult mice will be used to more closely align our studies with questions that occur in the treatment of ADO2 patients. Our studies will also provide important insight into the underlying mechanism of how Clcn7 dysfunction in osteoclasts leads to the development of ADO2 in patients.

摘要