Regulating Osteoblast Proliferation and Differentiation

调节成骨细胞增殖和分化

• 批准号: 6929127
• 负责人: HYUN-DUCK NAH-CEDERQUIST
• 金额: $ 32.87万
• 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/6929127
• 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）：正常骨骼质量的获取和维持需要足够数量的增生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或表现不佳的成骨细胞的减少与骨骼的异常发育以及衰老患者的骨骼重塑和骨折愈合受损有关。人们越来越认识到，包括成纤维细胞生长因子（FGF）在内的局部因素是与成骨过程相关的细胞事件的关键调节剂。 FGF的骨诱导作用是通过四个高亲和受体（FGFR1-4）介导的，而FGFR1和2是骨骼中的主要受体。但是，FGF骨诱导效果的机制以及每个FGFR在成骨中的特定功能仍然难以捉摸。在这项研究中，我们将检验以下假设：暂时表达的FGFR1和FGFR2坐在成骨细胞的增殖和分化以促进骨骼生长。在发育的骨骼中，FGFR2的表达主要局限于高度增殖成骨细胞前体细胞，并随成熟而降低。与FGFR2下调相关，细胞增殖降低，而FGFR1表达在分化成骨细胞中增加。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都积极地有助于骨骼形成，但在调节骨细胞增殖和分化的调节中可能具有差异作用。 FGFR2和FGFR1功能的丧失导致小鼠的膜内和小梁骨量大大降低，而FGFR2功能的增益似乎刺激了骨形成。我们的体外初步数据表明，FGFR2刺激细胞增殖，但抑制晚分化，RTMX2，BMP-2和STAT1可能是FGFR2功能的下游介体。因此，我们建议FGFR2通过增加runx2和/或bmp-2和STAT1的磷酸化来刺激细胞增殖和早期成骨分化，在扩展竞争力的早期成骨细胞群中起重要作用。我们进一步提出，较晚的成骨分化需要下调FGFR2，也许还需要上调OFFGFR1。我们的假设将在一组互补的体外和体内研究中进行检验，利用转基因和基因敲除方法来选择性调节FGFR1或FGFR2活性。