Regulating Osteoblast Proliferation and Differentiation

调节成骨细胞增殖和分化

• 批准号: 6824294
• 负责人: HYUN-DUCK NAH-CEDERQUIST
• 金额: $ 2.38万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 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 2004-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6824294
• 关键词: RNA interference; bone development; bone morphogenetic proteins; cell differentiation; cell growth regulation; cell proliferation; fibroblast growth factor; flow cytometry; gel mobility shift assay; genetically modified animals; in situ hybridization; laboratory mouse; light microscopy; northern blottings; osteoblasts; osteogenesis; phosphorylation; polymerase chain reaction; receptor expression

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）：正常骨量的获得和维持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。成骨细胞前体细胞群的减少或表现不佳的成骨细胞与骨骼的异常发育以及老年患者中受损的骨重建和骨折愈合相关。越来越多的人认识到，包括成纤维细胞生长因子（FGF）在内的局部因子是与成骨过程相关的细胞事件的关键调节因子。FGF的骨诱导作用通过四种高亲和力受体（FgfR 1 -4）介导，其中FgfR 1和2是骨中表达的主要受体。然而，FGF的骨诱导作用的机制以及每个FgfR在成骨中的具体功能仍然是不清楚的。在这项研究中，我们将测试的假设，暂时表达FgfR 1和FgfR 2协调成骨细胞增殖和分化，以促进骨生长。在发育中的骨中，FgfR 2的表达主要限于高度增殖的成骨细胞前体细胞，并随着成熟而降低。伴随着FgfR 2下调，细胞增殖减少，FgfR 1表达增加分化成骨细胞。来自我们初步的转基因小鼠和体外细胞培养研究的集体数据表明，FgfR 1和FgfR 2都对骨形成有积极贡献，但在骨细胞增殖和分化的调节中可能具有不同的作用。FgfR 2和FgfR 1功能的丧失导致小鼠的膜内和小梁骨量急剧减少，而FgfR 2功能的获得似乎刺激骨形成。我们在体外的初步数据表明，FgfR 2刺激细胞增殖，但抑制晚期分化，Rtmx 2，BMP-2和Stat 1可能是下游介质的FgfR 2功能。因此，我们认为FgfR 2通过Runx 2和/或BMP-2的增加和Stat 1的磷酸化刺激细胞增殖和早期成骨分化，在扩大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FgfR 2，也可能上调FgfR 1。我们的假设将在一组互补的体外和体内研究中进行测试，利用转基因和基因敲除方法选择性地调节FgfR 1或FgfR 2活性。