PTH resistance and marrow adipogenesis

PTH 抵抗和骨髓脂肪生成

• 批准号: 9979845
• 负责人: ROLAND E BARON
• 金额: $ 55.24万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9979845
• 关键词: Adipocytes; Adipose tissue; Age; Age-Related Bone Loss; Age-Related Osteoporosis; Animal Model; Antibodies; Area; Bioenergetics; Biopsy; Birth; Bone Marrow; Bone Resorption; Bone remodeling; Cell Differentiation process; Cell Separation; Cells; Characteristics; Complex; Data; Development; Disease model; Endocytosis; Exhibits; Fatty acid glycerol esters; Female; GTP-Binding Protein alpha Subunits, Gs; Gene Expression Profile; Genes; Genetic; Genetic Models; Glycolysis; Goals; Histologic; Histology; Impairment; In Vitro; Individual; Knockout Mice; Lead; Light; Marrow; Mediating; Mediator of activation protein; Mesenchymal; Mesenchymal Differentiation; Mesenchymal Stem Cells; Messenger RNA; Mus; Mutant Strains Mice; Obesity; Osmium; Osteoblasts; Osteocytes; Osteogenesis; Osteoporosis; Oxidative Phosphorylation; PPAR gamma; PTH gene; Pathway interactions; Peptides; Peripheral; Phenotype; Population; Production; Proteins; Role; Serum; Signal Transduction; Signaling Protein; Skeletal bone; Skeleton; Small Interfering RNA; Sorting - Cell Movement; Sum; TNFSF11 gene; Techniques; Technology; Testing; Tomatoes; Work; Zinc Fingers; adiponectin; bone; bone mass; cortical bone; driving force; experimental study; hormonal signals; hormone resistance; in vivo; lipid biosynthesis; male; men; mesenchymal stromal cell; microCT; mouse model; mutant; new technology; novel; osteogenic; osteoprogenitor cell; parathyroid hormone (1-34); parathyroid hormone-related protein; progenitor; recombinase; recruit; rosiglitazone; skeletal; stem cells; transcription factor

Age-related osteoporosis is characterized by enhanced skeletal fragility, low bone mass, secondary increases in PTH, high bone resorption and marrow adiposity. Previous animal models for this disorder did not recapitulate all these features. However, we developed a mouse model of impaired PTH function that develops age-related bone loss relatively soon after birth. For example, we found that conditional deletion of the PTH1R using the Prx1Cre recombinase led to a substantial increase in marrow adipose tissue (MAT) by 3 weeks of age. This was accompanied by increased bone resorption, low bone mass and high RANKL expression in the bone marrow and serum, even in the absence of functional PTH activity, and no change in osteocyte number/area or lacunar area. Also we noted that PTH administration to the PTH1Rfl/fl control mice reduced MAT volume by 50% but did not change MAT in the mutant mice. Similar findings were noted in men treated with PTH for osteoporosis. To further delineate the origin of RANKL, we then isolated bone marrow adipocytes from the Prx1cre;PTH1Rfl/fl mice and their controls, and found consistently high expression of adipose-related genes; e.g., Pparγ, Cebp α,β,Δ, Fabp4 and Adiponectin as well as Rankl. Supernatant from spun marrow showed an increase in RANKL protein (p<0.03) in the Prx1cre;PTH1Rfl/fl mutant mice. Progenitor cells removed from the bottom layer of spun marrow in the mutant mice showed enhanced adipogenic differentiation, increased RANKL expression, and co-localization of adiponectin and tomato red in the MSCs. Further, we noted that Rankl mRNA was undetectable in any adipose depot outside the marrow. We also found that zinc finger protein 467 (Zfp467), an early mesenchymal transcription factor that up-regulates Rankl, but is down regulated by PTH, was 8 fold higher in mutant adipocytes, whereas treatment with PTH suppressed Zfp467 mRNA by 70% in cortical bone of controls but not in mutants. In this proposal we hypothesize that PTH regulates marrow adipogenesis through suppression of Zfp467 and that the marrow adipocytes induced by loss of PTH signaling are unique, arising from a mesenchymal progenitor, which expresses both adipogenic and osteogenic markers. We propose two specific aims to test this hypothesis: 1) Determine the role of PTH1R in cell fate decisions of mesenchymal progenitor cells using genetic mouse models, define the downstream mediator of PTH1R in regulating bone marrow adipogenesis, and perform bioenergetic analyses; 2) Determine whether bone marrow adipocytes are the driving force via RANKL to enhance bone resorption in the absence of PTH1R signaling exploiting new technology for: 1-lineage tracing, 2-sorting marrow adipocytes, 3-treating with OPG and 4- generating a novel mouse model. The results of these experiments could lead to new targets for treating osteoporosis.

与年龄相关的骨质疏松症的特征是骨骼脆弱性增强，骨骼低，次级增加 在PTH中，高骨分辨率和骨髓肥胖。以前的动物模型没有 概括所有这些功能。但是，我们开发了一种开发PTH功能受损的鼠标模型 出生后相对较快的与年龄相关的骨质流失。例如，我们发现PTH1R的条件缺失 使用PRX1CRE重组酶，导致骨髓脂肪组织（MAT）大幅增加3周 年龄。这是通过增加骨骼分辨率，低骨骼质量和高度表达来实现的 骨髓和血清，即使没有功能性PTH活性，骨细胞也没有变化 数字/区域或空隙区域。我们还注意到，PTH给予PTH1RFL/FL控制小鼠减少了 MAT体积占50％，但没有改变突变小鼠的MAT。在接受治疗的男人中也注意到了类似的发现 pth用于骨质疏松症。为了进一步描述RANKL的起源，我们隔离了骨髓脂肪细胞 从prx1cre; pth1rfl/fl小鼠及其对照，并发现脂肪相关的高表达始终如一 基因；例如，PPARγ，CEBPα，β，δ，Fabp4和脂联素以及RANKL。 Spun Marrow的上清液 在PRX1CRE中显示RANKL蛋白（P <0.03）的增加； PTH1RFL/FL突变体小鼠。去除祖细胞 从突变小鼠的旋转骨髓的底层显示出增强的掺杂分化， 在MSC中，脂联素和番茄红的共定位RANKL表达增加。此外，我们 指出，Rankl mRNA在骨髓外的任何脂肪仓库中都是无法检测的。我们还发现锌 Finger蛋白467（ZFP467），一种早期的间充质转录因子，可上调RANKL，但下降了 由PTH调节，突变脂肪细胞中高8倍，而用PTH治疗抑制了ZFP467 mRNA在对照的皮质骨中为70％，而在突变体中则不在。在此提案中，我们假设PTH 通过抑制ZFP467来调节骨髓脂肪形成，并指出骨髓脂肪细胞由 PTH信号的损失是由间充质祖细胞引起的，它表达了两种脂肪 和成骨标记。 我们提出了两个特定的目的来检验这一假设：1）确定PTH1R在细胞脂肪决策中的作用 使用遗传小鼠模型的间充质祖细胞，定义了PTH1R的下游介体 调节骨髓脂肪形成并进行生物能分析； 2）确定骨髓是否 脂肪细胞是通过RANKL的驱动力，可以在没有PTH1R信号的情况下增强骨骼分辨率 利用新技术进行：1 linege跟踪，2级骨髓脂肪细胞，使用OPG和4-- 生成新的鼠标模型。这些实验的结果可能导致治疗的新目标 骨质疏松症。