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The article discusses the role of microRNAs in chondrogenesis and osteoarthritis (OA). It states that chondrocytes are responsible for the production and maintenance of the extracellular matrix (ECM) which gives the load-bearing function of tissues. It mentions that microRNAs play an important role in chondrogenic differentiation. It adds that understanding microRNA gene expression can help in treatments of OA.

Objective To identify microRNAs (miRNAs) in human T cells that can explain known antiinflammatory properties of steroids. Methods Activated human CD4+ T cells from healthy donors were exposed to 1 μ M methylprednisolone (MP) in vitro and then subjected to miRNA and messenger RNA microarray analyses. Changes in expression profiles were recorded. Using quantitative polymerase chain reaction (qPCR), flow cytometry, and enzyme-linked immunosorbent assay (ELISA), we confirmed the suppression of predicted targets, and through miRNA transfection experiments, we could suggest mechanistic links. Results We identified numerous steroid-responsive genes and miRNAs-many known and some novel-including multiple previously unknown proinflammatory genes suppressed by MP. Further studies using qPCR, flow cytometry, and ELISA demonstrated that methylprednisolone increased the expression of miRNA-98 (miR-98) and suppressed the levels of predicted targets, including interleukin-13 and 3 tumor necrosis factor receptors (TNFRs): Fas, FasL, and TNFR superfamily member 1B. Forced expression of miR-98 in T cells resulted in suppression of the same targets. Conclusion The findings of this study demonstrate a link between miR-98 expression and the effects of MP and provide evidence suggesting that MP acts through miR-98 to inhibit specific proinflammatory targets. Identification of this antiinflammatory mechanism of glucocorticoids is important, since it may pave the way toward the elusive goal of dissociating adverse effects from therapeutic effects. [ABSTRACT FROM AUTHOR]

Objective To investigate why the level of Lyn is significantly decreased in B cells from a majority of patients with systemic lupus erythematosus (SLE) and to determine the role of microRNA-30a (miR-30a) in SLE B cell hyperactivity. Methods Luciferase reporter gene assays were performed to identify the interaction between miR-30a and the 3′-untranslated region (3′-UTR) of Lyn. Levels of miR-30a in B cells were determined by TaqMan quantitative polymerase chain reaction (qPCR), Lyn messenger RNA levels were tested with real-time qPCR, and protein levels of Lyn were determined using Western blotting. The quantity of IgG was determined by enzyme-linked immunosorbent assay. The proliferation of B cells was measured using 3H-thymidine incorporation. Results In B cell lines, miR-30a, but not miR-30b, miR-30c, miR-30d, or miR-30e, could specifically bind the 3′-UTR of Lyn, and overexpression of miR-30a inhibited the levels of Lyn. The level of miR-30a in B cells was significantly higher in SLE patients compared to healthy donors. The level of miR-30a was negatively associated with the level of Lyn in B cells. Overexpression of miR-30a was found to promote B cell proliferation and the production of IgG antibodies. The effect of miR-30a could be abrogated by inducing overexpression of Lyn in B cells. Conclusion These results reveal that elevated expression of miR-30a is responsible for the reduction in levels of Lyn in B cells from patients with SLE, suggesting that miR-30a plays an important role in B cell hyperactivity. [ABSTRACT FROM AUTHOR]

Objective To examine the role of microRNA-142-3p/5p (miR-142-3p/5p) in the development of autoimmunity in patients with systemic lupus erythematosus (SLE). Methods MicroRNA-142-3p/5p expression levels were determined by real-time quantitative polymerase chain reaction, and potential target genes were verified using luciferase reporter gene assays. The effects of miR-142-3p/5p on T cell function were assessed by transfection with miR-142-3p/5p inhibitors or mimics. Histone modifications and methylation levels within a putative regulatory region of the miR-142 locus were detected by chromatin immunoprecipitation assay and bisulfite sequencing, respectively. Results We confirmed that miR-142-3p and miR-142-5p were significantly down-regulated in SLE CD4+ T cells compared with healthy controls and observed that miR-142-3p/5p levels were inversely correlated with the putative SLE-related targets signaling lymphocytic activation molecule-associated protein (SAP), CD84, and interleukin-10 (IL-10). We demonstrated that miR-142-3p and miR-142-5p directly inhibit SAP, CD84, and IL-10 translation, and that reduced miR-142-3p/5p expression in CD4+ T cells can significantly increase protein levels of these target genes. Furthermore, inhibiting miR-142-3p/5p in healthy donor CD4+ T cells caused T cell overactivation and B cell hyperstimulation, whereas overexpression of miR-142-3p/5p in SLE CD4+ T cells had the opposite effect. We also observed that the decrease in miR-142 expression in SLE CD4+ T cells correlated with changes to histone modifications and DNA methylation levels upstream of the miR-142 precursor sequence. Conclusion The results of this study indicate that reduced expression of miR-142-3p/5p in the CD4+ T cells of patients with SLE causes T cell activity and B cell hyperstimulation. [ABSTRACT FROM AUTHOR]

Objective To use an in vitro model of chondrogenesis to identify microRNAs (miRNAs) with a functional role in cartilage homeostasis. Methods The expression of miRNAs was measured in the ATDC5 cell model of chondrogenesis using microarray and was verified using quantitative reverse transcription-polymerase chain reaction. MicroRNA expression was localized by in situ hybridization. Predicted miRNA target genes were validated using 3′-untranslated region-Luc reporter plasmids containing either wild-type sequences or mutants of the miRNA target sequence. Signaling through the Smad pathway was measured using a (CAGA)12-Luc reporter. Results The expression of several miRNAs was regulated during chondrogenesis. These included 39 miRNAs that are coexpressed with miRNA-140 (miR-140), which is known to be involved in cartilage homeostasis and osteoarthritis (OA). Of these miRNAs, miR-455 resides within an intron of COL27A1 that encodes a cartilage collagen. When human OA cartilage was compared with cartilage obtained from patients with femoral neck fractures, the expression of both miR-140-5p and miR-455-3p was increased in OA cartilage. In situ hybridization showed miR-455-3p expression in the developing limbs of chicks and mice and in human OA cartilage. The expression of miR-455-3p was regulated by transforming growth factor β (TGFβ) ligands, and miRNA regulated TGFβ signaling. ACVR2B, SMAD2, and CHRDL1 were direct targets of miR-455-3p and may mediate its functional impact on TGFβ signaling. Conclusion MicroRNA-455 is expressed during chondrogenesis and in adult articular cartilage, where it can regulate TGFβ signaling, suppressing the Smad2/3 pathway. Diminished signaling through this pathway during the aging process and in OA chondrocytes is known to contribute to cartilage destruction. We propose that the increased expression of miR-455 in OA exacerbates this process and contributes to disease pathology. [ABSTRACT FROM AUTHOR]

The article discusses a study which revealed that MicroRNA-146a (miR-146a) expression stops osteoclastogenesis, and administration of miR-146a prevents joint destruction in mice with collagen-induced arthritis (CIA). Methods included quantitative reverse transcriptase–polymerase chain reaction (RT-PCR), and radiographic and histologic examinations. Details related to the study results are also presented.