The Effects of CFTR Dysfunction on Bone Formation

描述（由申请人提供）：囊性纤维化（CF）患者的中位生存期已增加至35岁。随着越来越多的CF患者存活到成年，骨质质量差已经成为这种慢性疾病的一个具有挑战性的负担。CF的低骨密度和骨折率增高有充分的文献记载，但对其了解甚少。尽管CFBD（囊性纤维化骨病）的患病率在成人中很高，但它也存在于儿童中。尽管其流行，CFBD的特征仍然很少，对其发病机制的了解仍然有限。我们的主要目标是在小鼠囊性纤维化模型中在结构和细胞水平上充分表征CFBD，因为它有可能为CFBD的发病机制提供更深入的了解。CF的小鼠模型对于评估CFTR在骨骼稳态中的直接作用特别有用，因为这些动物没有严重的肺部或胰腺疾病。产生的初步数据表明，从3周龄到成年期，这些cftr-/-动物的骨量减少，其特征是小梁变薄，皮质骨变薄，以及骨体积和强度下降，从而提供了类似于人类疾病的模型。我们假设该CF模型将表现出与CF患者相似的复杂的骨病变，骨密度低，骨脆性增加。在许多骨细胞系中，CFTR功能的改变可能在人类CFBD中起核心作用。然而，根据我们的初步研究，我们认为成骨细胞中缺乏CFTR可能是破骨细胞功能改变的主要问题，而破骨细胞功能改变是炎症的继发后果。通过原位杂交，RT-PCR，免疫组织化学以及标准膜片钳技术，CFTR在成骨细胞和破骨细胞中的功能作用将被检查。此外，将在体外检查成骨细胞和破骨细胞，以确定哪种细胞类型是导致原发性病变的原因。最后，我们将使用重复雾化LPS模型来确定慢性炎症是否会增加小鼠模型中CFBD的骨骼表型，方法是使用静态和动态骨组织形态学和骨转换的血清标志物来量化骨密度和微结构细胞活性。通过明确低骨密度的确切性质和演变，并阐明是否存在骨细胞活性的原发性缺陷，可以开展更多基于证据的干预试验，以解决CFBD的预防和管理问题。有了更强壮、更健康的骨骼，CF患者的生活质量就可以得到改善。

DESCRIPTION (provided by applicant): Median survival for people with Cystic Fibrosis (CF) has increased to >35 years of age. As more CF patients survive well into adulthood poor bone quality has emerged as a challenging burden of this chronic disease. Low bone density and increased fracture rates in CF are well-documented but poorly understood. Although the prevalence for CFBD (Cystic Fibrosis bone disease) is high in adults, it is also present in children. Despite its prevalence, CFBD remains minimally characterized and an understanding of its pathogenesis remains limited. Our major objective is to fully characterize CFBD in a murine model of cystic fibrosis at the structural and cellular level, as it has the potential to provide a deeper understanding of the pathogenesis of CFBD. Murine models of CF are particularly useful for assessing the direct role of CFTR in skeletal homeostasis as these animals do not have severe pulmonary or pancreatic disease. Preliminary data generated demonstrate that from as early as 3 weeks of age through adulthood, these cftr-/- animals have decreased bone mass which is characterized by thinner trabeculae, and thinner cortical bone, as well as, decreased bone volume and strength thus providing a model similar to human disease. We hypothesize that this CF model will manifest a complex bone lesion with low bone density and increased bone fragility similar to that which is observed in CF patients. It is likely that altered CFTR function in a number of bone cell lineages plays a central role in CFBD in humans. However, based on our initial studies we believe the lack of CFTR in the osteoblast is likely to be the primary problem with alterations in osteoclast function a secondary consequence of inflammation. By employing in situ hybridization, RT-PCR, and immunohistochemistry as well as standard patch clamp techniques, the functional role of CFTR in osteoblasts and osteoclasts will be examined. In addition osteoblasts and osteoclasts will be examined in vitro to determine which cell type is responsible for the primary lesion. Lastly we will use a repetitive aerosolized LPS model to determine if chronic inflammation augments the skeletal phenotype of CFBD in the murine model by quantifying bone density and micro-architecture cellular activity using static and dynamic bone histomorphometry and serum markers of bone turnover. By clarifying the exact nature and evolution of the low BMD, and elucidating whether there is a primary defect in bone cell activity, more evidence-based intervention trials can be undertaken to address prevention and management of CFBD. With a stronger, healthier skeleton, the quality of life of patients with CF can be improved.