Project description:Endochondral ossification forms and grows the majority of the mammalian skeleton and is tightly controlled through gene regulatory networks. The forkhead box transcription factors Foxc1 and Foxc2 have been demonstrated to regulate aspects of osteoblast function in the formation of the skeleton but their roles in chondrocytes to control endochondral ossification are less clear. We demonstrate that Foxc1 expression is directly regulated by SOX9 activity, one of the earliest transcription factors to specify the chondrocyte lineages. Moreover we demonstrate that elevelated expression of Foxc1 promotes chondrocyte differentiation in mouse embryonic stem cells and loss of Foxc1 function inhibits chondrogenesis in vitro. Using chondrocyte-targeted deletion of Foxc1 and Foxc2 in mice, we reveal a role for these factors in chondrocyte differentiation in vivo. Loss of both Foxc1 and Foxc2 caused a general skeletal dysplasia predominantly affecting the vertebral column. The long bones of the limb were smaller and mineralization was reduced and organization of the growth plate was disrupted. In particular, the stacked columnar organization of the proliferative chondrocyte layer was reduced in size and cell proliferation in growth plate chondrocytes was reduced. Differential gene expression analysis indicated disrupted expression patterns in chondrogenesis and ossification genes throughout the entire process of endochondral ossification in Col2-cre;Foxc1Δ/Δ;Foxc2Δ/Δ embryos. Our results suggest that Foxc1 and Foxc2 are required for correct chondrocyte differentiation and function. Loss of both genes results in disorganization of the growth plate, reduced chondrocyte proliferation and delays in chondrocyte hypertrophy that prevents correct ossification of the endochondral skeleton.
Project description:A variety of cell cultures models and in vivo approaches have been used to study gene expression during chondrocyte differentiation. The extent to which the in vitro models reflect bona fide gene regulation in the growth plate has not been quantified. In addition, studies that evaluate global gene expression changes among different growth plate zones are limited. To address these issues, we completed a microarray screen of three growth plate zones derived from manually segmented embryonic mouse tibiae. Classification of genes differentially expressed between each respective growth plate zone, functional categorization as well as characterization of gene expression patterns, cytogenetic loci, signaling pathways and functional motifs confirmed documented data and pointed to novel aspects of chondrocyte differentiation. Parallel comparisons of the microdissected tibiae data set to our previously completed micromass culture screen further corroborated the suitability of micromass cultures for modeling gene expression in chondrocyte development. The micromass culture system demonstrated striking similarities to the in vivo microdissected tibiae screen; however, the micromass system was unable to accurately distinguish gene expression differences in the hypertrophic and mineralized zones of the growth plate. These studies will allow us to better understand zone-specific gene expression patterns in the growth plate. Ultimately, this work will help define both the genomic context in which genes are expressed in the long bones and the extent to which the micromass culture system is able to recapitulate chondrocyte development in endochondral ossification. Keywords: Growth plate microdissection
Project description:Axial growth of long bones occurs through a coordinated process of growth plate chondrocyte proliferation and differentiation. This maturation of chondrocytes is reflected in a zonal change in gene expression and cell morphology from resting to proliferative, prehypertrophic, and hypertrophic chondrocytes of the growth plate followed by ossification. A major experimental limitation in understanding growth plate biology and pathophysiology is the lack of a robust technique to isolate cells from the different zones, particularly from small animals. Here, we report on a new strategy for separating distinct chondrocyte populations from mouse growth plates. By transcriptome profiling of microdissected zones of growth plates, we identified novel, zone-specific cell surface markers and used these for flow cytometry and immunomagnetic cell separation to quantify, enrich, and characterize chondrocytes populations with respect to their differentiation status. This approach provides a novel platform to study cartilage development and characterize mouse growth plate chondrocytes to reveal unique cellular phenotypes of the distinct subpopulations within the growth plate.
Project description:A variety of cell cultures models and in vivo approaches have been used to study gene expression during chondrocyte differentiation. The extent to which the in vitro models reflect bona fide gene regulation in the growth plate has not been quantified. In addition, studies that evaluate global gene expression changes among different growth plate zones are limited. To address these issues, we completed a microarray screen of three growth plate zones derived from manually segmented embryonic mouse tibiae. Classification of genes differentially expressed between each respective growth plate zone, functional categorization as well as characterization of gene expression patterns, cytogenetic loci, signaling pathways and functional motifs confirmed documented data and pointed to novel aspects of chondrocyte differentiation. Parallel comparisons of the microdissected tibiae data set to our previously completed micromass culture screen further corroborated the suitability of micromass cultures for modeling gene expression in chondrocyte development. The micromass culture system demonstrated striking similarities to the in vivo microdissected tibiae screen; however, the micromass system was unable to accurately distinguish gene expression differences in the hypertrophic and mineralized zones of the growth plate. These studies will allow us to better understand zone-specific gene expression patterns in the growth plate. Ultimately, this work will help define both the genomic context in which genes are expressed in the long bones and the extent to which the micromass culture system is able to recapitulate chondrocyte development in endochondral ossification. Experiment Overall Design: Tibiae from 15.5 day old mouse embryos were isolated and partitioned into three distinct zones. Total RNA was isolated from each segment and the individual segments pooled within a litter. Experiment Overall Design: Samples were hybridized to Affymetrix MOE 430 2.0 mouse chips for analysis. Four independent trials were executed for each zone. Experiment Overall Design: Number of time points: 1 Experiment Overall Design: Number of treatments: 0 Experiment Overall Design: Number of Samples: 4 replicates per zone Experiment Overall Design: Affymetrix chip: MOE 430 2.0 Experiment Overall Design: Tissue or origin: Tibiae Experiment Overall Design: Species E15.5 mice Experiment Overall Design: Samples: Total RNA
Project description:Idiopathic short stature is diagnosed by a standing height of less than two standard deviation scores in a specific population adjusted for age and gender and the exclusion of identifiable diseases. A series of studies have confirmed that noncoding RNAs can regulate the chondrocyte proliferation, hypertrophy, and endochondral ossification in the growth plate. In order to analyze and find differentially expressed ceRNAs (lncRNAs, circRNAs and mRNAs in peripheral blood exosomes of idiopathic short stature and healthy controls, we aimed to explore whether differentially expressed ceRNAs (lncRNAs, circRNAs and mRNAs) in peripheral blood exosomes of idiopathic short stature. Three pairs of peripheral blood exosomes samples were subjected to microarray analysis using the SBC human ceRNA Microarray.
Project description:Endochondral ossification is the process by which the appendicular skeleton, facial bones, vertebrae and medial clavicles are formed and relies on the tight control of chondrocyte maturation. Fibroblast growth factor receptor (FGFR)3 plays a role in bone development and maintenance and belongs to a family of proteins which differ in their ligand affinities and tissue distribution. Activating mutations of the FGFR3 gene lead to craniosynostosis and multiple types of skeletal dysplasia with varying degrees of severity: thanatophoric dysplasia (TD), achondroplasia and hypochondroplasia. Despite progress in the characterization of FGFR3-mediated regulation of cartilage development, many aspects remain unclear. The aim and the novelty of our study was to examine whole gene expression differences occurring in primary human chondrocytes isolated from normal cartilage or pathological cartilage from TD-affected fetuses, using Affymetrix technology. The phenotype of the primary cells was confirmed by the high expression of chondrocytic markers. Altered expression of genes associated with many cellular processes was observed, including cell growth and proliferation, cell cycle, cell adhesion, cell motility, metabolic pathways, signal transduction, cell cycle process and cell signaling. Most of the cell cycle process genes were down-regulated and consisted of genes involved in cell cycle progression, DNA biosynthesis, spindle dynamics and cytokinesis. About eight percent of all modulated genes were found to impact extracellular matrix (ECM) structure and turnover, especially glycosaminoglycan (GAG) and proteoglycan biosynthesis and sulfation. Altogether, the gene expression analyses provide new insight into the consequences of FGFR3 mutations in cell cycle regulation, onset of pre-hypertrophic differentiation and concomitant metabolism changes. Moreover, impaired motility and ECM properties may also provide clues about growth plate disorganization. These results also suggest that many signaling pathways may be directly or indirectly altered by FGFR3 and confirm the crucial role of FGFR3 in the control of growth plate development.
Project description:Idiopathic short stature is diagnosed by a standing height of less than two standard deviation scores in a specific population adjusted for age and gender and the exclusion of identifiable diseases. A series of studies have confirmed that noncoding RNAs can regulate the chondrocyte proliferation, hypertrophy, and endochondral ossification in the growth plate. In order to analyze and find differentially expressed circRNAs in Idiopathic short stature and healthy controls, we aimed to explore whether differentially expressed circRNAs in idiopathic short stature. Four pairs of blood samples were subjected to microarray analysis using the Arraystar Human CircRNAs Microarray v2 (Arraystar, USA). Compared to normal individuals, in ISS patients, the expression levels of 83 circRNAs were upregulated and those of 62 were downregulated.
Project description:C-type natriuretic peptide (CNP) has been recently identified as an important anabolic regulator of endochondral bone growth, but the molecular mechanism mediating these effects are not completely understood. Here we demonstrate that CNP activates the p38 MAP kinase pathway in chondrocytes and that pharmacological inhibition of p38 blocks the anabolic effects of CNP in a tibia organ culture system. We further show that CNP stimulates endochondral bone growth largely through expansion of the hypertrophic zone of the growth plate, while delaying mineralization. Both effects are reversed by p38 inhibition. We performed Affymetrix microarray analyses to identify CNP target genes in the organ culture system. These studies confirmed that hypertrophic chondrocytes are the main targets of CNP signaling in the growth plate, potentially because cGMP-dependent kinases I and II, important transducers of CNP signaling and are expressed at much higher levels in these cells than in other areas of the tibia. One of the genes most strongly induced by CNP was the Ptgs2 gene, encoding Cox2. Real-time PCR confirmed that Cox2 expression was induced by CNP in hypertrophic chondrocytes, but surprisingly in a p38-independent manner. Moreover, Cox2 inhibition – in contrast to p38 inhibition - did not block the anabolic effects of CNP. In summary, our data identify novel target genes of CNP and demonstrate that the p38 pathway is a novel, essential mediator of CNP effects on endochondral ossification, with potential implications for numerous skeletal diseases. Keywords: Growth plate zone comparison and treatment response analysis
Project description:Histone deacetylase inhibitors are efficacious epigenetic-based therapies for some cancers and neurological disorders; however, these drugs inhibit multiple Hdacs and have detrimental effects on the pre- and post-natal skeleton. To better understand how Hdac inhibitors affect the skeleton, we focused on understanding the role of one of their targets, Hdac3, in endochondral bone formation by deleting it in immature murine chondrocyte micro masses with Adeno-Cre. Hdac3-deficient chondrocytes expressed higher levels of pro-inflammatory and matrix degrading genes (e.g., Il-6, Mmp3, Mmp13, Saa3) and lower levels of genes related to the extracellular matrix production, bone development and ossification (e.g., Acan, Col2a1, Ihh, Col10a1). Histone acetylation was increased in and around genes with elevated expression. High Throughput RNA sequencing and Chromatin immunopreciptation sequencing experiments were performed in chondrocyte cultures. Differential analysis was conducted on ChIP-seq and RNA-seq data to identify H3K27Ac profile for up and down regulated genes in Hdac3-deficient murine chondrocytes.