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Articular cartilage regeneration by activated skeletal stem cells

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE151303 | GEO | 2020/06/24

REPOSITORIES: GEO

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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:Mechanical Stimuli are arguably the most important aetiolgical factors in osteoarthritis (OA) development. Not only do we see disease arising from joints where the cartilage has sustained direct (e.g. intraarticular fracture) or indirect (e.g. meniscal injury) trauma, but mechanical factors are considered, at least partly, to explain the disease associations with aging and obesity. It is now well established that OA is not simply due to repeated wear and tear, leading to attrition of the articular surfaces, but that it requires activation of a number of inflammatory genes, which drive catabolic protease activity in the joint. These enzymes lead to breakdown of the major extracellular matrix components of cartilage, namely type II collagen, and the proteoglycan, aggrecan. Although it is unclear precisely which enzymes are responsible for matrix breakdown in human OA, Glasson et al showed that deletion of the aggrecan degrading enzyme, ADAMTS5 substantially protected the joint from surgically induced murine OA suggesting that it is a major aggrecanase in the mouse. This study was part of a wider study using the surgical model of murine OA, induced by destabilising the medial meniscus (DMM), to confirm the dependence of joint loading on disease progression and to reveal mechanosensitive genes within the joint which may be involved in the development of OA. Using this model we, and others, have shown that there is a robust degradation of articular cartilage over 4-12wks in male C57B/6 mice. We identified the gene response in joints early following induction of OA, prior to cartilage degradation, by extracting RNA from whole joints (after skin and muscle had been removed) 6hrs, 3 days and 7 days following sham and DMM surgery. An Affymetrix ST1 gene array was performed. Significantly regulated genes (>1.4 fold above naive and sham samples at any timepoint), or those considered to have a putative role in OA pathogenesis were selected for quantitative validation using Taqman low density microfluidic card arrays (TLDA). Gene expression in whole knee joints at 3 early time points post DMM surgery (before cartilage loss), 6hrs, 3days and 7days was examined. Two controls were identified, the first control consisted of age matched naïve mice that had undergone 15 minutes of anaesthesia but were not operated on (0hrs post surgery). The second control included mice which had undergone sham surgery (capsulotomy alone). For this RNA was taken at the same time points post surgery as DMM samples (6hrs, 3days and 7days). There were three biological replicates per condition (total of 21 samples). The right (ipsilateral) knee joint was taken and RNA extracted and processed for microarray analysis using the Affymetrix Mouse Gene 1.0 st v1 platform.

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Articular cartilage regeneration by activated skeletal stem cells

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