Inhibition of MLL1-menin interaction attenuates renal fibrosis in obstructive nephropathy.

Mixed lineage leukemia 1 (MLL1), a histone H3 lysine 4 (H3K4) methyltransferase, exerts its enzymatic activity by interacting with menin and other proteins. It is unclear whether inhibition of the MLL1-menin interaction influences epithelial-mesenchymal transition (EMT), renal fibroblast activation, and renal fibrosis. In this study, we investigated the effect of disrupting MLL1-menin interaction on those events and mechanisms involved in a murine model of renal fibrosis induced by unilateral ureteral obstruction (UUO), in cultured mouse proximal tubular cells and renal interstitial fibroblasts. Injury to the kidney increased the expression of MLL1 and menin and H3K4 monomethylation (H3K4me1); MLL1 and menin were expressed in renal epithelial cells and renal interstitial fibroblasts. Inhibition of the MLL1-menin interaction by MI-503 administration or siRNA-mediated silencing of MLL1 attenuated UUO-induced renal fibrosis, and reduced expression of α-smooth muscle actin (α-SMA) and fibronectin. These treatments also inhibited UUO-induced expression of transcription factors Snail and Twist and transforming growth factor ß1 (TGF-ß1) while expression of E-cadherin was preserved. Moreover, treatment with MI-503 and transfection with either MLL siRNA or menin siRNA inhibited TGF-ß1-induced upregulation of α-SMA, fibronectin and Snail, phosphorylation of Smad3 and AKT, and downregulation of E-cadherin in cultured renal epithelial cells. Finally, MI-503 was effective in abrogating serum or TGFß1-induced transformation of renal interstitial fibroblasts to myofibroblasts in vitro. Taken together, these results suggest that targeting disruption of the MLL1-menin interaction attenuates renal fibrosis through inhibition of partial EMT and renal fibroblast activation.

[Formulation of expert consensus on clinical application of external ethnic medicine: taking Baimai Ointment as an example].

The concept of ethnic medicine is divided into a broad sense and a narrow sense. The broad concept refers to the traditional medicine of the Chinese nation, and the narrow concept refers to the traditional medicine of Chinese ethnic minorities. The external medicine is one of the main forms of ethnic medicine, and it is also the important content of ethnic medicine for external use, which is widely used in clinical practice. As the theory of ethnic medicine is unique, the application methods have certain characteristics, which are the key technical parts of clinical practice. However, the existing traditional Chinese medicine consensus formulation me-thods cannot meet the needs of the consensus formulation of the external ethnic medicine. Therefore, the methods suitable for expert consensus on external ethnic medicine are required. This article took Expert opinion on clinical application of Baimai Ointment as an exa-mple, and explorde a reasonable, effective, multi-dimensional, and multi-stage method to formulate expert consensus on the external ethnic medicine. In this research, three-dimensional sources of information, including ancient classics, clinical research evidence, and expert application experiences, were systematically and scientifically collected. After organization and analysis, the information was formed into comprehensive evidence. In a formal consensus meeting, part of the recommendations reached consensus. As to the issues that did not reach agreement, in-depth interviews were used to explore the reasons for the differences and resolve the disagreements. Finally, unanimous recommendations were reached. There are common problems during the formulation process of Expert opinion on clinical application of Baimai Ointment. This study is expected to provide references for the formulation of expert consensus on other external ethnic medicine.

Critical roles of SMYD2 lysine methyltransferase in mediating renal fibroblast activation and kidney fibrosis.

SET and MYND domain protein 2 (SMYD2) is a lysine methyltransferase that mediates histone H3 lysine 36 trimethylation (H3K36me3) and acts as a regulator of tumorgenesis and cystic growth. However, its role in renal fibrosis remains unknown. In this study, we found that SMYD2 was highly expressed in the murine kidney of renal fibrosis induced by unilateral ureteral obstruction, and primarily located in interstitial fibroblasts and renal tubular epithelial cells. Pharmacological inhibition of SMYD2 with AZ505, a highly selective inhibitor of SMYD2, protected against renal fibrosis and inhibited activation/proliferation of renal interstitial fibroblasts and conversion of epithelial cells to a profibrotic phenotype in this model. In cultured renal interstitial fibroblasts, treatment with AZ505 or silencing of SMYD2 by specific siRNA also inhibited serum- or TGF-ß1-induced activation and proliferation of renal interstitial fibroblasts. Mechanistic studies showed that SMYD2 inhibition reduced phosphorylation of several profibrotic signaling molecules, including Smad3, extracellular signal-regulated kinase 1/2, AKT, signal transducer and activator of transcription-3 and nuclear factor-κB in both injured kidney and cultured renal fibroblasts. AZ505 was also effective in suppressing renal expression of Snail and Twist, two transcriptional factors that mediate renal partial epithelial-mesenchymal transition and fibrosis. Conversely, AZ505 treatment prevented downregulation of Smad7, a renoprotective factor in vivo and in vitro. These results indicate that SMYD2 plays a critical role in mediating conversion of epithelial cells to a profibrotic phenotype, renal fibroblast activation and renal fibrogenesis, and suggest that SMYD2 may be a potential target for the treatment of chronic fibrosis in kidney disease.

Amino acid-balanced diets improved DSS-induced colitis by alleviating inflammation and regulating gut microbiota.

PURPOSE: Inflammatory bowel disease (IBD) is a multifactorial chronic disease of the gastrointestinal tract. Dietary intervention in the treatment of IBD has gradually attracted more attention. In this study, amino acid-balanced diets (AABD) based on grains were developed and their influences on the regulation of IBD were investigated. METHODS: Dextran sodium sulfate (DSS)-induced acute colitis mice model was employed to evaluate the effects of AABD. Pathological symptoms, intestinal inflammation, gut barrier proteins and gut microbiota were determined after AABD intake. RESULTS: It was shown that AABD alleviated the symptoms of colitis by reducing the histological scores of mice colon, suppressing the expression of pro-inflammatory cytokines (IL-1ß, IL-6 and TNF-α) and upregulating the expression of tight junction proteins. Analysis of gut microbiota revealed that AABD altered the structure of gut microbiota by decreasing the abundance and richness of harmful bacteria induced by DSS (Escherichia-Shigella, Parasutterella, etc.) and increasing that of beneficial bacteria (Akkermansia, etc.). Correlation analysis indicated that the alterations of pro-inflammatory factors were related with the change of microbiota, suggesting that the inhibitory effects of AABD on inflammation might be due to its regulation gut microbiota. CONCLUSION: The AABD could efficiently mitigate colitis, and this study indicated that AABD could be applied as a promising dietary regulation strategy of IBD.

Nonmalignant CD30+ Cells in Contralateral Peri-Implant Capsule of Patient With BIA-ALCL: A Premalignant Step?

CD30 lymphocyte activation antigen and phosphorylated STAT3 (pSTAT3) are consistent markers of tumor cells in breast implant-associated anaplastic large cell lymphoma (BIA-ALCL). We present a case of BIA-ALCL in a breast implant capsule containing clustered tumor cells expressing CD30, pSTAT3, pSTAT6, interleukin 9, and granzyme B tumor cell biomarkers. Remarkably, the contralateral breast contained many scattered large, atypical CD30+ cells surrounded by inflammatory cells, raising a suspicion of bilateral BIA-ALCL, known to occur in some patients. To clarify the diagnosis, immunohistochemistry and multilabel immunofluorescence were performed. Unlike the tumor cells, the atypical CD30+ cells of the contralateral breast lacked pSTAT3, pSTAT6, interleukin 9, and granzyme B, eliminating a diagnosis of bilateral BIA-ALCL. This case highlights the importance of interpreting CD30 staining in the context of other tumor cell biomarkers and histopathology to avoid an incorrect diagnosis of BIA-ALCL. We believe the findings also suggest the possibility of CD30 expression as an early event in the multistep pathogenesis of BIA-ALCL.

Human osteoarthritis cartilage-derived stromal cells activate joint degeneration through TGF-beta lateral signaling.

Human osteoarthritis cartilage contains chondrocytes (OAC) and mesenchymal stromal cells (OA-MSC). Here, we found that TGF-ß had different effects on OA-MSC and OAC, and revealed its lateral signaling mechanism in OA. RNAseq analysis indicated that OA-MSC expressed the same level of Bone Morphogenetic Protein (BMP) Receptor-1A as OAC but only 1/12 of Transforming Growth Factor beta (TGF-ß) Receptor-1. While TGF-ß specifically activated SMAD2 in OAC, it also activated BMP signaling-associated SMAD1 in OA-MSC. While TGF-ß stimulated chondrogenesis in OAC, it induced hypertrophy, mineralization, and MMP-13 in OA-MSC. Inhibiting TGF-ßR1 suppressed MMP-13 in OA-MSC but stimulated it in OAC. In contrast, by specifically targeting BMPR1A/ACVR1 in both cell types, LDN193189 inhibits cartilage degeneration through suppressing hypertrophy and MMP-13 in a mouse osteoarthritis model. Thus, LDN193189, a drug under development to inhibit constitutive BMP signaling during heterotopic ossification, may be re-purposed for OA treatment.

[Systematic review of efficacy and safety of Ginkgo biloba extract 50 in treatment of ischemic stroke].

The present study aimed to systematically evaluate the efficacy and safety of Ginkgo biloba extract 50(GBE50) in the treatment of ischemic stroke. The databases including CNKI, Wanfang, VIP, SinoMed, PubMed, EMbase, and Cochrane Library were searched for randomized controlled trial(RCT) of GBE50 for the treatment of ischemic stroke reported between database inception and May 2020. The methodological quality of the included RCTs was evaluated via the Cochrane risk of bias tool. The RevMan 5.4 was used for Meta-analysis. Sixteen RCTs were included, involving 1 615 patients with acute ischemic stroke. Most of the included RCTs reported the methods of random sequence generation, but only two performed the concealment of random sequence. All RCTs failed in blinding. Two RCTs reported the information of cases lost to follow-up and drop-outs. Since the number was small, the baselines of groups remained balanced. All RCTs reported key outcomes of ischemic stroke, which made selective reporting bias in a low risk. Meta-analysis results revealed that GBE50 combined with routine therapies could effectively lower the score of the National Institutes of Health stroke scale(NIHSS) and restore cognitive function and daily activity in ischemic stroke patients. Compared with routine therapies, the combination is advantageous in treating patients with ischemic stroke. However, high-quality multicenter RCTs with large sample sizes are still required for verification.

Selective inhibition of class IIa histone deacetylases alleviates renal fibrosis.

In this study, we examined the effect of MC1568, a selective class IIa histone deacetylase (HDAC) inhibitor, on the development and progression of renal fibrosis in a murine model of renal fibrosis induced by unilateral ureteral obstruction (UUO). All 4 class IIa HDAC isoforms, in particular HDAC4, were up-regulated in renal epithelial cells of the injured kidney. Administration of MC1568 immediately after UUO injury reduced expression of α-smooth muscle actin (α-SMA), fibronectin, and collagen 1. MC1568 treatment or small interfering RNA-mediated silencing of HDAC4 also suppressed expression of those proteins in cultured renal epithelial cells. Mechanistically, MC1568 abrogated UUO-induced phosphorylation of Smad3, NF-κB, and up-regulation of integrin ɑVß6 in the kidney and inhibited TGF-ß1-induced responses in cultured renal epithelial cells. MC1568 also increased renal expression of klotho, bone morphogenetic protein 7, and Smad7. Moreover, delayed administration of MC1568 at 3 d after ureteral obstruction reversed the expression of α-SMA, fibronectin, and collagen 1 and increased expression of matrix metalloproteinase (MMP)-2 and -9. Collectively, these results suggest that selectively targeting class IIa HDAC isoforms (in particular HDAC4) may inhibit development and progression of renal fibrosis by suppressing activation and expression of multiple profibrotic molecules and increasing expression of antifibrotic proteins and MMPs.-Xiong, C., Guan, Y., Zhou, X., Liu, L., Zhuang, M. A., Zhang, W., Zhang, Y., Masucci, M. V., Bayliss, G., Zhao, T. C., Zhuang, S. Selective inhibition of class IIa histone deacetylases alleviates renal fibrosis.

Blocking the histone lysine 79 methyltransferase DOT1L alleviates renal fibrosis through inhibition of renal fibroblast activation and epithelial-mesenchymal transition.

Disruptor of telomeric silencing-1 like (DOT1L) protein specifically catalyzes the methylation of histone H3 on Lys79 (H3K79) and is implicated in tumors. But its role in tissue fibrosis remains unclear. Here we demonstrated that injury to the kidney increased DOT1L expression and H3K79 dimethylation in renal tubular epithelial cells and myofibroblasts in a murine model of unilateral ureteral obstruction. Administration of EPZ5676, a highly selective inhibitor of DOT1L, attenuated renal fibrosis. Treatment with EPZ5676 or DOT1L small interfering RNA also inhibited TGF-ß1 and serum-induced activation of renal interstitial fibroblasts and epithelial-mesenchymal transition (EMT) in vitro. Moreover, blocking DOT1L abrogated injury-induced epithelial G2/M arrest; reduced expression of Snail, Twist, and Notch1; and inactivated several profibrotic signaling molecules in the injured kidney, including Smad3, epidermal growth factor receptor, platelet-derived growth factor receptor, signal transducer and activator of transcription 3, protein kinase B, and NF-κB. Conversely, DOT1L inhibition increased expression of phosphatase and tensin homolog, a protein associated with dephosphorylation of tyrosine kinase receptors, and prevented decline in levels of Klotho and Smad7, 2 renoprotective factors. Thus, our data indicate that targeting DOT1L attenuates renal fibrosis through inhibition of renal fibroblasts and EMT by suppressing activation of multiple profibrotic signaling pathways while retaining expression of renoprotective factors.-Liu, L., Zou, J., Guan, Y., Zhang, Y., Zhang, W., Zhou, X., Xiong, C., Tolbert, E., Zhao, T. C., Bayliss, G., Zhuang, S. Blocking the histone lysine 79 methyltransferase DOT1L alleviates renal fibrosis through inhibition of renal fibroblast activation and epithelial-mesenchymal transition.

[Systematic review on clinical efficacy and safety of Cheezheng Pain Relieving Plaster for soft tissue injury].

To systematically evaluate the clinical efficacy and safety of Cheezheng Pain Relieving Plaster in the treatment of soft tissue injury. Four Chinese databases(namely CNKI, WanFang, VIP, CBM) and 2 English databases(namely PubMed, Cochrane Library) were retrieved from the establishment of each database to March 2019. The randomized controlled trials of Cheezheng Pain Relieving Plaster compared with routine therapy in treatment of soft tissue injury were included. The quality of the included studies was assessed using the Cochrane Risk Assessment Tool. Five studies were included, and 367 patients were enrolled. None of the included studies reported randomized concealment, blinding, follow-up and dropping off. The results showed that Cheezheng Pain Relieving Plaster may have advantages in alleviating joint pain, swelling, tenderness and dysfunction and other symptoms, with no serious adverse reaction. Compared with routine therapy, Cheezheng Pain Relieving Plaster may have advantages in the treatment of soft tissue injury. However, due to the quality of the included RCTs, the conclusions of this study were limited. In addition, to produce high-quality evidences for the clinical application of Cheezheng Pain Relieving Plaster, the conclusions of this study shall be further verified with large-sample, scientifically designed and strictly implemented clinical trials.

[Consideration on establishing evaluation system of clinical practice guidelines in traditional Chinese medicine].

Standardization is the technical support for the development of traditional Chinese medicine(TCM), and the guidelines have become the main component of the core standards of TCM technology. With the rise and development of evidence-based medicine in China, more than 500 guidelines have been issued in China, and the number is still increasing, but the quality of guidelines still lags far behind the international level. Similarly, the formulation of evidence-based clinical practice guidelines for TCM has gradually attracted the attention of the industry, but the quality is not so good, and most guidelines are not really evidence-based guidelines. Only reliable guidelines can fully and effectively play the role of clinical guidance. In order to comprehensively improve the scientificity and credibility of the guidelines, guideline evaluation can be used as a means to improve the quality of the guidelines. For the development of traditional Chinese medicine, it has become an urgent task to establish a complete evaluation standard system of guidelines, especially the evaluation standard system that conforms to the technical characteristics of traditional Chinese medicine. In this paper, the advantages and limitations of a series of domestic and foreign guideline evaluation tools were systematically analyzed, and the thinking and difficulties to establish the evaluation system of TCM guidelines were put forward, with a purpose to further improve the quality of TCM clinical practice guidelines, so that they can be better applied in clinical practice to enhance the clinical efficacy of TCM and ensure the quality of medical services.

[Quality evaluation recommendation list and interpretation of traditional Chinese medicine clinical practice guidelines].

Based on the idea of establishing a complete guideline evaluation system applicable to the field of traditional Chinese medicine(TCM), the author believes that a complete guideline evaluation system of traditional Chinese medicine clinical practice should be divided into three parts: quality evaluation, clinical applicability evaluation and clinical application investigation. According to the different purposes, different evaluators, different evaluation methods and different evaluation time points in the guideline evaluation, the quality evaluation recommendation list, the clinical applicability evaluation recommendation list and the clinical application questionnaire were formed. Among them, the purpose of quality evaluation is to evaluate the methodological quality in the guideline development process, in order to measure whether the entire guideline development process is scientifically rigorous. The evaluators must be the methodologists with an evidence-based medicine background. Therefore, a logical, detailed and comprehensive guideline quality evaluation list will provide good evaluation tools for the TCM guideline formulation team and play an important role in promoting the quality and application of the guidelines. By referring to the internationally recognized development process and methods of evaluation tools, as well as the proof by authoritative TCM clinical experts and methodologists, the author worked out the quality evaluation list of clinical practice guidelines applicable to the field of TCM by considering the characteristics of TCM field. In this paper, the author introduces the whole list of quality evaluation recommendations, and interprets each item in details, hoping to provide reference for the standardization of TCM clinical practice guidelines in the future.

[Applicability evaluation recommendation list and interpretation of traditional Chinese medicine clinical practice guidelines].

The development of the guidelines should not only meet the rigorous methodological requirements, but also ensure the credibility or enforceability of the guideline recommendations when they are applied in clinical practice. Based on the idea of establi-shing a perfect guideline evaluation system applicable to the field of traditional Chinese medicine(TCM), the author believed that a complete evaluation system of clinical practice guidelines in the field of TCM shall be divided into three parts: quality evaluation, applicability evaluation and clinical application investigation. Among them, applicability evaluation refers to the evaluation of the degree of fit between the guideline and clinical practice, that is, whether the guidelines have good readability and clinical applicability to promote clinical application. The evaluators are clinical experts in the related fields of TCM. Therefore, a logical, detailed and comprehensive guideline quality evaluation list will provide good evaluation tools for the TCM guideline formulation team and play an important role in promoting the quality and application of the guidelines. Based on the internationally recognized development process and methods of evaluation tools, as well as the proof by authoritative TCM clinical experts and methodologists, the author worked out the quality evaluation list of clinical practice guidelines applicable to the field of TCM. In this paper, the author introduces the whole list of quality evaluation, and interprets each item in details, hoping to provide reference for the standardization of TCM clinical practice guidelines in the future.

[Bibliometric analysis and quality assessment of clinical evidence on Xiaotong Tiegao].

Many clinical studies on Cheezheng Xiaotong Tiegao have been accumulated since it was launched in 1993,but they have not been comprehensively analyzed and evaluated. This study systematically retrieved relevant studies in six databases at home and abroad as of December 2017. This study analyzed the statistics of the included studies in several aspects,including publication time,region,fund,disease category and type of study. In this study,various tools were used to evaluate the methodological quality of included studies,such as the Cochrane collaboration's tool for assessing the risk of bias in randomized trials,MINORS,IHE,AMSTAR2.The results showed that the literatures were mainly published from 2010 to 2011,and a total of 28 projects were financially supported.The most involved disease was arthropathy. The randomized controlled trials were the majority in the included studies,but the quality was low,and most of the literatures didn't report the allocation concealment and blinding. This study comprehensively reflected the current situations and shortcomings of the clinical studies of Cheezheng Xiaotong Tiegao,and put forward several suggestions,in the expectation of providing a reference for the future clinical research direction of Cheezheng Xiaotong Tiegao.

5,7,3',4'-Tetramethoxyflavone protects chondrocytes from ER stress-induced apoptosis through regulation of the IRE1α pathway.

AIM OF THE STUDY: To investigate the roles of endoplasmic reticulum (ER) transmembrane sensor inositol-requiring enzyme-1 (IRE1)α signaling in ER stress-induced chondrocyte apoptosis, and to determine the molecular mechanisms underlying chondroprotective activity of 5,7,3',4'-tetramethoxyflavone (TMF) from Murraya exotica. MATERIALS AND METHODS: IRE1α was knocked down by siRNA transfection in chondrocytes, which were harvested from rats' knee cartilages. Chondrocytes with IRE1α deficiency were administrated with tunicamycin (TM) and TMF. Chondrocyte apoptosis was quantified by flow cytometry and DAPI/TUNEL staining. Expression of mRNA and proteins was quantified by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western-blot, respectively. RESULTS: IRE1α deficiency significantly increased the rate of TM-induced chondrocyte apoptosis, down-regulated the expression of pro-survival factors XBP1S and Bcl-2, and up-regulated pro-apoptotic factors CHOP, p-JNK, and caspase-3. TMF suppressed TM-induced chondrocyte apoptosis by activating the expression of IRE1α, which reversed the expression patterns of downstream pro-survival and pro-apoptotic factors due to IRE1α deficiency. CONCLUSION: The mechanism of TMF in protecting chondrocytes against ER stress-induced apoptosis might be associated with regulating the activity of ER sensor IRE1α and its downstream pathway.

Biological and Chemical Removal of Primary Cilia Affects Mechanical Activation of Chondrogenesis Markers in Chondroprogenitors and Hypertrophic Chondrocytes.

Chondroprogenitors and hypertrophic chondrocytes, which are the first and last stages of the chondrocyte differentiation process, respectively, are sensitive to mechanical signals. We hypothesize that the mechanical sensitivity of these cells depends on the cell surface primary cilia. To test this hypothesis, we removed the primary cilia by biological means with transfection with intraflagellar transport protein 88 (IFT88) siRNA or by chemical means with chloral hydrate treatment. Transfection of IFT88 siRNA significantly reduced the percentage of ciliated cells in both chondroprogenitor ATDC5 cells as well as primary hypertrophic chondrocytes. Cyclic loading (1 Hz, 10% matrix deformation) of ATDC5 cells in three-dimensional (3D) culture stimulates the mRNA levels of chondrogenesis marker Type II collagen (Col II), hypertrophic chondrocyte marker Type X collagen (Col X), and a molecular regulator of chondrogenesis and chondrocyte hypertrophy bone morphogenetic protein 2 (BMP-2). The reduction of ciliated chondroprogenitors abolishes mechanical stimulation of Col II, Col X, and BMP-2. In contrast, cyclic loading stimulates Col X mRNA levels in hypertrophic chondrocytes, but not those of Col II and BMP-2. Both biological and chemical reduction of ciliated hypertrophic chondrocytes reduced but failed to abolish mechanical stimulation of Col X mRNA levels. Thus, primary cilia play a major role in mechanical stimulation of chondrogenesis and chondrocyte hypertrophy in chondroprogenitor cells and at least a partial role in hypertrophic chondrocytes.

Mechanical and IL-1ß Responsive miR-365 Contributes to Osteoarthritis Development by Targeting Histone Deacetylase 4.

Mechanical stress plays an important role in the initiation and progression of osteoarthritis. Studies show that excessive mechanical stress can directly damage the cartilage extracellular matrix and shift the balance in chondrocytes to favor catabolic activity over anabolism. However, the underlying mechanism remains unknown. MicroRNAs (miRNAs) are emerging as important regulators in osteoarthritis pathogenesis. We have found that mechanical loading up-regulated microRNA miR-365 in growth plate chondrocytes, which promotes chondrocyte differentiation. Here, we explored the role of the mechanical responsive microRNA miR-365 in pathogenesis of osteoarthritis (OA). We found that miR-365 was up-regulated by cyclic loading and IL-1ß stimulation in articular chondrocytes through a mechanism that involved the transcription factor NF-κB. miR-365 expressed significant higher level in rat anterior cruciate ligament (ACL) surgery induced OA cartilage as well as human OA cartilage from primary OA patients and traumatic OA Patients. Overexpression of miR-365 in chondrocytes increases gene expression of matrix degrading enzyme matrix metallopeptidase 13 (MMP13) and collagen type X (Col X). The increase in miR-365 expression in OA cartilage and in response to IL-1 may contribute to the abnormal gene expression pattern characteristic of OA. Inhibition of miR-365 down-regulated IL-1ß induced MMP13 and Col X gene expression. We further showed histone deacetylase 4 (HDAC4) is a direct target of miR-365, which mediates mechanical stress and inflammation in OA pathogenesis. Thus, miR-365 is a critical regulator of mechanical stress and pro-inflammatory responses, which contributes cartilage catabolism. Manipulation of the expression of miR-365 in articular chondrocytes by miR-365 inhibitor may be a potent therapeutic target for the prevention and treatment of osteoarthritis.

Matrilin-3 inhibits chondrocyte hypertrophy as a bone morphogenetic protein-2 antagonist.

Increased chondrocyte hypertrophy is often associated with cartilage joint degeneration in human osteoarthritis patients. Matrilin-3 knock-out (Matn3 KO) mice exhibit these features. However, the underlying mechanism is unknown. In this study, we sought a molecular explanation for increased chondrocyte hypertrophy in the mice prone to cartilage degeneration. We analyzed the effects of Matn3 on chondrocyte hypertrophy and bone morphogenetic protein (Bmp) signaling by quantifying the hypertrophic marker collagen type X (Col X) gene expression and Smad1 activity in Matn3 KO mice in vivo and in Matn3-overexpressing chondrocytes in vitro. The effect of Matn3 and its specific domains on BMP activity were quantified by Col X promoter activity containing the Bmp-responsive element. Binding of MATN3 with BMP-2 was determined by immunoprecipitation, solid phase binding, and surface plasmon resonance assays. In Matn3 KO mice, Smad1 activity was increased more in growth plate chondrocytes than in wild-type mice. Conversely, Matn3 overexpression in hypertrophic chondrocytes led to inhibition of Bmp-2-stimulated, BMP-responsive element-dependent Col X expression and Smad1 activity. MATN3 bound BMP-2 in a dose-dependent manner. Multiple epidermal growth factor (EGF)-like domains clustered together by the coiled coil of Matn3 is required for Smad1 inhibition. Hence, as a novel BMP-2-binding protein and antagonist in the cartilage extracellular matrix, MATN3 may have the inherent ability to inhibit premature chondrocyte hypertrophy by suppressing BMP-2/Smad1 activity.

Mechanical activation of mammalian target of rapamycin pathway is required for cartilage development.

Mechanical stress regulates development by modulating cell signaling and gene expression. However, the cytoplasmic components mediating mechanotransduction remain unclear. In this study, elimination of muscle contraction during chicken embryonic development resulted in a reduction in the activity of mammalian target of rapamycin (mTOR) in the cartilaginous growth plate. Inhibition of mTOR activity led to significant inhibition of chondrocyte proliferation, cartilage tissue growth, and expression of chondrogenic genes, including Indian hedgehog (Ihh), a critical mediator of mechanotransduction. Conversely, cyclic loading (1 Hz, 5% matrix deformation) of embryonic chicken growth plate chondrocytes in 3-dimensional (3D) collagen scaffolding induced sustained activation of mTOR. Mechanical activation of mTOR occurred in serum-free medium, indicating that it is independent of growth factor or nutrients. Treatment of chondrocytes with Rapa abolished mechanical activation of cell proliferation and Ihh gene expression. Cyclic loading of chondroprogenitor cells deficient in SH2-containing protein tyrosine phosphatase 2 (Shp2) further enhanced mechanical activation of mTOR, cell proliferation, and chondrogenic gene expression. This result suggests that Shp2 is an antagonist of mechanotransduction through inhibition of mTOR activity. Our data demonstrate that mechanical activation of mTOR is necessary for cell proliferation, chondrogenesis, and cartilage growth during bone development, and that mTOR is an essential mechanotransduction component modulated by Shp2 in the cytoplasm.

MicroRNA-1 regulates chondrocyte phenotype by repressing histone deacetylase 4 during growth plate development.

MicroRNAs (miRs) are noncoding RNAs (17-25 nt) that control translation and/or mRNA degradation. Using Northern blot analysis, we identified that miR-1 is specifically expressed in growth plate cartilage in addition to muscle tissue, but not in brain, intestine, liver, or lung. We obtained the first evidence that miR-1 is highly expressed in the hypertrophic zone of the growth plate, with an 8-fold increase compared with the proliferation zone; this location coincides with the Ihh and Col X expression regions in vivo. MiR-1 significantly induces chondrocyte proliferation and differentiation. We further identified histone deacetylase 4 (HDAC4) as a target of miR-1. HDAC4 negatively regulates chondrocyte hypertrophy by inhibiting Runx2, a critical transcription factor for chondrocyte hypertrophy. MiR-1 inhibits both endogenous HDAC4 protein by 2.2-fold and the activity of a reporter gene bearing the 3'-untranslated region (UTR) of HDAC4 by 3.3-fold. Conversely, knockdown of endogenous miR-1 relieves the repression of HDAC4. Deletion of the miR-1 binding site in HDAC4 3'-UTR or mutated miR-1 abolishes miR-1-mediated inhibition of the reporter gene activity. Overexpression of HDAC4 reverses miR-1 induction of chondrocyte differentiation markers Col X and Ihh. HDAC4 inhibits Runx2 promoter activity in a dosage-dependent manner. Thus, miR-1 plays an important role in the regulation of the chondrocyte phenotype during the growth plate development via direct targeting of HDAC4.