PTH resistance and marrow adipogenesis

PTH 抵抗和骨髓脂肪生成

基本信息

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
项目类别：
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

项目摘要

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.

年龄相关性骨质疏松症的特点是骨骼脆性增强、骨量低、继发性增加在 PTH 中，高骨吸收和骨髓肥胖在以前的动物模型中没有这种疾病。然而，我们开发了一种 PTH 功能受损的小鼠模型。出生后不久就会出现与年龄相关的骨质流失，例如，我们发现 PTH1R 的条件性缺失。使用 Prx1Cre 重组酶导致骨髓脂肪组织 (MAT) 显着增加 3 周年龄伴随着骨吸收增加、骨量低和 RANKL 表达高。骨髓和血清，即使没有功能性 PTH 活性，骨细胞也没有变化我们还注意到，对 PTH1Rfl/fl 对照小鼠的 PTH 给药减少了。在突变小鼠中，MAT 体积减少了 50%，但 MAT 没有改变，在接受治疗的男性中也发现了类似的结果。为了进一步阐明 RANKL 的起源，我们随后分离了骨髓脂肪细胞。来自 Prx1cre;PTH1Rfl/fl 小鼠及其对照，并发现与脂肪相关的持续高表达基因；例如 Pparγ、Cebp α、β、Δ、Fabp4 和脂联素以及来自骨髓的上清液。显示去除祖细胞的 Prx1cre;PTH1Rfl/fl 突变小鼠中 RANKL 蛋白增加（p<0.03）。来自突变小鼠的旋转骨髓底层的细胞显示出增强的脂肪形成分化， MSC 中 RANKL 表达增加，脂联素和番茄红共定位。注意到Rankl mRNA 在骨髓外的任何脂肪库中均检测不到。我们还发现了锌。手指蛋白 467 (Zfp467)，一种早期间充质转录因子，可上调 Rankl，但下调受 PTH 调节，突变脂肪细胞中的 Zfp467 含量高出 8 倍，而 PTH 处理则抑制 Zfp467 对照皮质骨中的 mRNA 增加了 70%，而突变体中则没有。在本提案中，我们追求的是 PTH。通过抑制 Zfp467 调节骨髓脂肪生成，并且通过抑制 Zfp467 诱导骨髓脂肪细胞 PTH 信号传导的丧失是独特的，由间充质祖细胞引起，该祖细胞表达脂肪形成和成骨标志物。我们提出两个具体目标来检验这一假设：1）确定 PTH1R 在细胞命运决定中的作用使用遗传小鼠模型的间充质祖细胞，定义了 PTH1R 的下游介质调节骨髓脂肪生成，并进行生物能分析2)确定是否骨髓；在缺乏 PTH1R 信号传导的情况下，脂肪细胞是通过 RANKL 增强骨吸收的驱动力利用新技术：1-谱系追踪、2-分选骨髓脂肪细胞、3-用 OPG 处理和 4- 这些实验的结果可能会产生新的治疗靶标。骨质疏松症。