Regulating Osteoblast Proliferation and Differentiation

调节成骨细胞增殖和分化

• 批准号: 7268812
• 负责人: HYUN-DUCK NAH-CEDERQUIST
• 金额: $ 31.16万
• 依托单位: CHILDREN'S HOSP OF PHILADELPHIA
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7268812
• 关键词: Affinity; Aging; Bone Growth; Bone Marrow; Bone remodeling; Calvaria; Candidate Disease Gene; Cell Proliferation; Cells; Commit; Craniosynostosis; Cultured Cells; Data; Development; Dominant-Negative Mutation; Down-Regulation; Ducks; Equilibrium; Event; Fibroblast Growth Factor; Fibroblast Growth Factor Receptors; Fracture Healing; Gene Expression; Genes; In Vitro; Knock-out; Knockout Mice; Maintenance; Mediating; Mediator of activation protein; Mus; Mutation; Numbers; Osteoblasts; Osteogenesis; Patients; Phenotype; Phosphorylation; Play; Population; Process; Production; Protein Isoforms; RNA Splicing; Rattus; Regulation; Role; Skeleton; Staging; Stem cells; Stromal Cells; Testing; Transcriptional Activation; Transgenic Mice; Transgenic Organisms; Up-Regulation; bone; bone cell; bone morphogenetic protein 2; bone morphogenetic protein receptors; in vivo; intramembranous bone formation; mineralization; mouse model; mutant; precursor cell; prevent; promoter; receptor; size; substantia spongiosa

DESCRIPTION (provided by applicant): Acquisition and maintenance of normal bone mass requires an adequate number of proliferative osteogenic precursor cells as well as the differentiated functions of osteoblasts. A reduction in the osteoblast precursor cell population or under-performing osteoblasts has been associated with abnormal development of the skeleton, as well as impaired bone remodeling and fracture healing in aging patients. Increasingly, it is being recognized that local factors, including fibroblast growth factors (FGFs), are crucial regulators of the cellular events associated with the osteogenic process. The bone-inducing effects of FGFs are mediated through four high affinity receptors (FgfR1-4), with FgfR1 and 2 being the major receptors expressed in bone. However the mechanisms of FGF's bone inducing effect as well as specific functions of each FgfR in osteogenesis remain elusive. In this study, we will test the hypothesis that temporally expressed FgfR1 and FgfR2 coordinates osteogenic cell proliferation and differentiation to promote bone growth. In developing bones, expression of FgfR2 is mainly restricted to highly proliferative osteoblast precursor cells and decreases with maturation. Concomitant with FgfR2 down-regulation, cell proliferation decreases and FgfR1 expression increases in differentiating osteoblasts. Collective data from our preliminary transgenic mouse and in vitro cell culture studies suggest that FgfR1 and FgfR2 both positively contribute to bone formation but may have differential roles in the regulation of bone cell proliferation and differentiation. The loss of FgfR2 and FgfR1 function results in drastically reduced intramembranous and trabecular bone mass in mice, while gain of FgfR2 function appears to stimulate bone formation. Our in vitro preliminary data suggest that FgfR2 stimulates cell proliferation but inhibits late differentiation and that Rtmx2, BMP-2 and Stat1 may be downstream mediators of FgfR2 functions. Therefore, we propose that FgfR2 plays a significant role in expanding the differentiation-competent early osteogenic cell population, by stimulating both cell proliferation and early osteogenic differentiation via increases in Runx2 and/or BMP-2 and phosphorylation of Stat1. We propose further that late osteogenic differentiation requires down-regulation of FgfR2 and perhaps also up-regulation ofFgfR1. Our hypothesis will be tested in a complementary set of in vitro and in vivo studies, utilizing transgenic and gene knock out approaches to selectively modulate either FgfR1 or FgfR2 activity.

描述（由申请人提供）：获得和维持正常骨量需要足够数量的增殖性成骨前体细胞以及成骨细胞的分化功能。在老年患者中，成骨前体细胞数量减少或成骨细胞表现不佳与骨骼发育异常以及骨重塑和骨折愈合受损有关。越来越多的人认识到，局部因子，包括成纤维细胞生长因子（FGFs），是与成骨过程相关的细胞事件的关键调节因子。FGFs的骨诱导作用是通过四种高亲和力受体（FgfR1-4）介导的，其中FgfR1和fgfr2是骨中表达的主要受体。然而，FGF诱导成骨作用的机制以及每种FgfR在成骨中的具体功能尚不清楚。在本研究中，我们将验证暂时表达的FgfR1和FgfR2协调成骨细胞增殖和分化以促进骨生长的假设。在发育中的骨骼中，FgfR2的表达主要局限于高度增殖的成骨细胞前体细胞，并随着成熟而降低。在分化成骨细胞中，伴随FgfR2下调，细胞增殖减少，FgfR1表达增加。我们的初步转基因小鼠和体外细胞培养研究的集体数据表明，FgfR1和FgfR2都积极促进骨形成，但在骨细胞增殖和分化的调节中可能具有不同的作用。FgfR2和FgfR1功能的丧失导致小鼠膜内和小梁骨量急剧减少，而FgfR2功能的增加似乎刺激骨形成。我们的体外初步数据表明，FgfR2刺激细胞增殖，但抑制晚期分化，Rtmx2、BMP-2和Stat1可能是FgfR2功能的下游介质。因此，我们提出FgfR2通过增加Runx2和/或BMP-2以及Stat1的磷酸化来刺激细胞增殖和早期成骨分化，在扩大具有分化能力的早期成骨细胞群中发挥重要作用。我们进一步提出，晚期成骨分化需要下调FgfR2，也可能需要上调fgfr1。我们的假设将在一组补充的体外和体内研究中得到验证，利用转基因和基因敲除方法选择性地调节FgfR1或FgfR2的活性。