Circulating osteogenic cells in aging and disease

背景：与年龄相关的病理性骨化，包括终末期钙化瓣膜病和髋关节置换术后异位骨形成，在老年人群中发病率很高。具有成骨潜能的细胞可以在多种组织中发现，最近在循环中被证明是一种可以在体内产生骨的单核血源性贴壁细胞（bdac）。事实上，成骨bdac可能与循环纤维细胞有关，最初是在伤口修复的背景下描述的，但随后发现参与肉芽肿形成和各种纤维化疾病。目的：阐明bdac在成骨和骨化病理状态中的生理作用。[2]目的探讨bdac与成骨细胞和成纤维细胞的表型关系。假设：[1]成骨性bdac是来源于骨髓的循环纤维细胞，在体外可产生矿化基质，在体内可形成骨。bdac参与年龄相关性异位骨化（HO）。特定目的和研究设计：[1]通过表型标记来表征bdac，表明bdac是纤维细胞，与成骨细胞和成纤维细胞区分开来。[2]通过在体外生命周期的不同阶段进行的体外矿化和体内骨形成试验证明bdac的成骨潜力。通过检测从女性性别不匹配的骨髓移植受者分离的细胞中的Y染色体特异性DNA，证实bdac的推定组织起源是骨髓。[4]利用表型标记物的免疫荧光检测终末期钙化性瓣膜性心脏病和髋关节置换术后等固定条件下HO病变中bdac的存在。长期目标：确定bdac作为成骨细胞的作用，在诊断检测、细胞替代治疗或基因治疗的靶群体中具有潜在的应用价值。

DESCRIPTION (provided by applicant): BACKGROUND: Age-related conditions of pathologic ossification, including end-stage calcific valvular disease and ectopic bone formation post-hip arthroplasty, account for great morbidity in the geriatric population. Cells with osteogenic potential can be found in a variety of tissues, and more recently have been demonstrated in the circulation as a population of mononuclear blood-derived adherent cells (BdACs) that can produce bone in vivo. Osteogenic BdACs may, in fact, be related to circulating fibrocytes, initially described in the context of wound repair, but subsequently found to participate in granuloma formation and various fibrosing disorders. OBJECTIVES: [1] To elucidate the physiologic role of BdACs in osteogenesis and in pathological states of ossification. [2] To determine the phenotypic relationship of BdACs to osteoblasts and fibroblasts. HYPOTHESES: [1] Osteogenic BdACs are circulating fibrocytes derived from bone marrow that can produce a mineralized matrix in vitro and form bone in vivo. [2] BdACs are involved in age-related heterotopic ossification (HO). SPECIFIC AIMS and RESEARCH DESIGN: [1] Characterize BdACs by phenotypic markers to show that BdACs are fibrocytes, and distinguishable from osteoblasts and fibroblasts. [2] Demonstrate the osteogenic potential of BdACs by assays of in vitro mineralization and in vivo bone formation performed at various stages of their in vitro life span. [3] Confirm the presumptive tissue origin of BdACs as bone marrow by detecting Y chromosome-specific DNA in these cells isolated from female sex-mismatched bone marrow transplant recipients. [4] Detect the presence of BdACs in lesions of HO occurring in end-stage calcific valvular heart disease and in conditions of immobilization such as post-hip arthroplasty using immunofluorescence of phenotypic markers. LONG-TERM OBJECTIVES: To define the role of BdACs as osteogenic cells with potential for use in diagnostic testing, cell replacement therapy, or as a target population for gene therapy.