Project description:Steroid and xenobiotic receptor (SXR) and its murine ortholog pregnane X receptor (PXR) are nuclear receptors that are expressed mainly in the liver and the intestine. They function as xenobiotic sensors by inducing genes involved in detoxification and drug excretion. Recent evidence showed that SXR and PXR are also expressed in bone tissue where they mediate bone metabolism. Here we report that systemic deletion of PXR results in aging-dependent wearing of articular cartilage of knee joints. Histomorphometrical analysis showed remarkable reduction of width and an enlarged gap between femoral and tibial articular cartilage in PXR knockout mice. We hypothesized that genes induced by SXR in chondrocytes have a protective effect on articular cartilage and identified Fam20a (family with sequence similarity 20a) as an SXR-dependent gene induced by the known SXR ligands, rifampicin and vitamin K2. Lastly, we demonstrated the biological significance of Fam20a expression in chondrocytes by evaluating osteoarthritis-related gene expression of primary articular chondrocytes. Consistent with epidemiological findings, our findings indicate that SXR/PXR protects against aging-dependent wearing of articular cartilage and that ligands for SXR/PXR have potential role in preventing osteoarthritis caused by aging.
Project description:Steroid and xenobiotic receptor (SXR) and its murine ortholog pregnane X receptor (PXR) are nuclear receptors that are expressed mainly in the liver and the intestine. They function as xenobiotic sensors by inducing genes involved in detoxification and drug excretion. Recent evidence showed that SXR and PXR are also expressed in bone tissue where they mediate bone metabolism. Here we report that systemic deletion of PXR results in aging-dependent wearing of articular cartilage of knee joints. Histomorphometrical analysis showed remarkable reduction of width and an enlarged gap between femoral and tibial articular cartilage in PXR knockout mice. We hypothesized that genes induced by SXR in chondrocytes have a protective effect on articular cartilage and identified Fam20a (family with sequence similarity 20a) as an SXR-dependent gene induced by the known SXR ligands, rifampicin and vitamin K2. Lastly, we demonstrated the biological significance of Fam20a expression in chondrocytes by evaluating osteoarthritis-related gene expression of primary articular chondrocytes. Consistent with epidemiological findings, our findings indicate that SXR/PXR protects against aging-dependent wearing of articular cartilage and that ligands for SXR/PXR have potential role in preventing osteoarthritis caused by aging. ADC5 cells were infected with adeno-SXR or adeno-DsRed and cultured in phenol red-free DMEM with charcoal/dextran-treated FCS (5%) containing rifampicin (10 μM), vitamin K2 (10 μM), or ethanol. Total RNA was extracted from the cells using the ToTALLY RNA Kit (Ambion, Austin, TX). Profiling of mRNA was performed on Affymetrix Mouse Gene 1.0 ST arrays (Affymetrix Inc., Santa Clara, USA) according to the Gene Chip labeling assay manual version 4.
Project description:As the most common degenerative joint disease, osteoarthritis (OA) contributes significantly to pain and disability during aging. Several genes of interest involved in articular cartilage damage in OA have been identified. However, the direct causes of OA are poorly understood. Evaluating the public human RNA-seq dataset showed that Cbfβ, (subunit of a heterodimeric Cbfβ/Runx1,Runx2, or Runx3 complex) expression is decreased in the cartilage of patients with OA. Here, we found that the chondrocyte-specific deletion of Cbfβ in tamoxifen-induced Cbfβf/fCol2α1-CreERT mice caused a spontaneous OA phenotype, worn articular cartilage, increased inflammation, and osteophytes. RNA-sequencing analysis showed that Cbfβ deficiency in articular cartilage resulted in reduced cartilage regeneration, increased canonical Wnt signaling and inflammatory response, and decreased Hippo/YAP signaling and TGF-β signaling. Immunostaining and western blot validated these RNA-seq analysis results. ACLT surgery-induced OA decreased Cbfβ and Yap expression and increased active β-catenin expression in articular cartilage, while local AAV-mediated Cbfβ overexpression promoted Yap expression and diminished active β-catenin expression in OA lesions. Remarkably, AAV-mediated Cbfβ overexpression in knee joints of mice with OA showed the significant protective effect of Cbfβ on articular cartilage in the ACLT OA mouse model. Overall, this study, using loss-of-function and gain-of-function approaches, uncovered that low expression of Cbfβ may be the cause of OA. Moreover, Local admission of Cbfβ may rescue and protect OA through decreasing Wnt/β-catenin signaling, and increasing Hippo/Yap signaling and TGFβ/Smad2/3 signaling in OA articular cartilage, indicating that local Cbfβ overexpression could be an effective strategy for treatment of OA. Using unbiased genome-wide RNA-seq data from Cbfβf/f;Col2α1-Cre hip joint articular cartilage and Cbfβf/f;Aggrecan-cre knee joint articular cartilage and their controls, we examined Cbfβ-mediated transcriptional targets for articular cartilage regeneration in OA.
Project description:Articular cartilage exhibits regional and depth-dependent biomechanical differences, which influence the transduction of load to chondrocytes and throughout the tissue matrix. One such mechanism is the biophysical release of proteins from the matrix. This study conducted proteomic analysis of rested porcine articular cartilage to assess regional protein abundance throughout distinct depths of porcine knee articular cartilage.
Project description:Osteoarthritis (OA) is a degenerative disease resulting in irreversible, progressive destruction of articular cartilage1. The etiology of OA is complex and involves a variety of factors, including genetic predisposition, acute injury and chronic inflammation2-4. Here we investigate the ability of resident skeletal stem-cell (SSC) populations to regenerate cartilage in relation to age, a possible contributor to the development of osteoarthritis. We demonstrate that aging is associated with progressive loss of SSCs and diminished chondrogenesis in the joints of both mice and humans. However, a local expansion of SSCs could still be triggered in the chondral surface of adult limb joints in mice by stimulating a regenerative response using microfracture (MF) surgery. Although MF-activated SSCs tended to form fibrous tissues, localized co-delivery of BMP2 and soluble VEGFR1 (sVEGFR1), a VEGF receptor antagonist, in a hydrogel skewed differentiation of MF-activated SSCs toward articular cartilage. These data indicate that following MF, a resident stem-cell population can be induced to generate cartilage for treatment of localized chondral disease in OA.
Project description:We used laser capture microdissection to isolate different zones of the articular cartilage from proximal tibiae of 1-week old mice, and used microarray to analyze global gene expression. Bioinformatic analysis corroborated previously known signaling pathways, such as Wnt and Bmp signaling, and implicated novel pathways, such as ephrin and integrin signaling, for spatially associated articular chondrocyte differentiation and proliferation. In addition, comparison of the spatial regulation of articular and growth plate cartilage revealed unexpected similarities between the superficial zone of the articular cartilage and the hypertrophic zone of the growth plate. Collecte five biological replications in three superficial, mid zone and deep zones of Articular Cartilage Assessed by Laser Captured Microdissection and Microarray(Superficial Zone vs Mid Zone vs Deep Zone)
Project description:Osteoarthritis is a common joint disorder that causes debilitating conditions among the elderly. Risk factors of osteoarthritis include age, which is often associated with the thinning of articular cartilage. We generated conditional knockout mice that lack salt-inducible kinase 3 (Sik3) specifically in chondrocytes after birth by tamoxifen administration. Deletion of Sik3 at 2 or 8 weeks after birth increased the thickness of articular cartilage by increasing the chondrocyte population. Additionally, Sik3 deletion protected cartilage against osteoarthritis development. We identified the edible Pteridium aquilinum ingredient, pterosin B, as a compound that inhibits the Sik3 pathway. Intraarticular injection of pterosin B protected cartilage against osteoarthritis development. Sik3 deletion or pterosin B treatment inhibited activation of the hypertrophic program through the histone deacetylase 4 (Hdac4) pathway, increased Prg4 expression in chondrocytes, and protected cartilage against osteoarthritic attack. Collectively, our results suggest Sik3 is a regulator that regulates homeostasis of articular cartilage thickness and a target for treatment of osteoarthritis, and that pterosin B can be the lead compound for relevant drugs.
Project description:Osteoarthritis (OA) is characterised by an irreversible degeneration of articular cartilage. Here we show that the BMP-antagonist Gremlin 1 (Grem1) marks a bipotent chondrogenic and osteogenic progenitor cell population within the articular surface. Notably, these progenitors are depleted by injury-induced OA and increasing age. OA is also caused by ablation of Grem1 cells in mice. Transcriptomic and functional analysis in mice found that articular surface Grem1-lineage cells are dependent on Foxo1 and ablation of Foxo1 in Grem1-lineage cells caused OA. FGFR3 signalling was confirmed as a promising therapeutic pathway by administration of pathway activator, FGF18, resulting in Grem1-lineage chondrocyte progenitor cell proliferation, increased cartilage thickness and reduced OA. These findings suggest that OA, in part, is caused by mechanical, developmental or age-related attrition of Grem1 expressing articular cartilage progenitor cells. These cells, and the FGFR3 signalling pathway that sustains them, may be effective future targets for biological management of OA.