Objective Several microRNA, which are ∼22‐nucleotide noncoding RNAs, exhibit tissue‐specific or developmental stage–specific expression patterns and are associated with human diseases. The objective of this study was to identify the expression pattern of microRNA‐146 (miR‐146) in synovial tissue from patients with rheumatoid arthritis (RA). Methods The expression of miR‐146 in synovial tissue from 5 patients with RA, 5 patients with osteoarthritis (OA), and 1 normal subject was analyzed by quantitative reverse transcription–polymerase chain reaction (RT‐PCR) and by in situ hybridization and immunohistochemistry of tissue sections. Induction of miR‐146 following stimulation with tumor necrosis factor α (TNFα) and interleukin‐1β (IL‐1β) of cultures of human rheumatoid arthritis synovial fibroblasts (RASFs) was examined by quantitative PCR and RT‐PCR. Results Mature miR‐146a and primary miR‐146a/b were highly expressed in RA synovial tissue, which also expressed TNFα, but the 2 microRNA were less highly expressed in OA and normal synovial tissue. In situ hybridization showed primary miR‐146a expression in cells of the superficial and sublining layers in synovial tissue from RA patients. Cells positive for miR‐146a were primarily CD68+ macrophages, but included several CD3+ T cell subsets and CD79a+ B cells. Expression of miR‐146a/b was markedly up‐regulated in RASFs after stimulation with TNFα and IL‐1β. Conclusion This study shows that miR‐146 is expressed in RA synovial tissue and that its expression is induced by stimulation with TNFα and IL‐1β. Further studies are required to elucidate the function of miR‐146 in these tissues.

Paracrine signaling by bone-marrow-derived mesenchymal stem cells (MSCs) plays a major role in tissue repair. Although the production of regulatory cytokines by MSC transplantation is a critical modulator of tissue regeneration, we focused on exosomes, which are extracellular vesicles that contain proteins and nucleic acids, as a novel additional modulator of cell-to-cell communication and tissue regeneration. To address this, we used radiologic imaging, histological examination, and immunohistochemical analysis to evaluate the role of exosomes isolated from MSC-conditioned medium (CM) in the healing process in a femur fracture model of CD9 2/2 mice, a strain that is known to produce reduced levels of exosomes. We found that the bone union rate in CD9 2/2 mice was significantly lower than wild-type mice because of the retardation of callus formation. The retardation of fracture healing in CD9 2/2 mice was rescued by the injection of exosomes, but this was not the case after the injection of exosomes-free conditioned medium (CM-Exo). The levels of the bone repairrelated cytokines, monocyte chemotactic protein-1 (MCP-1), MCP-3, and stromal cell-derived factor-1 in exosomes were low compared with levels in CM and CM-Exo, suggesting that bone repair may be in part mediated by other exosome components, such as microRNAs. These results suggest that exosomes in CM facilitate the acceleration of fracture healing, and we conclude that exosomes are a novel factor of MSC paracrine signaling with an important role in the tissue repair process. STEM CELLS TRANSLATIONAL MEDICINE 2016;5:1620-1630 SIGNIFICANCEThis work focuses on exosomes, which are extracellular vesicles, as a novel additional modulator of cell-to-cell communication. This study evaluated the role of exosomes isolated from mesenchymal stem cell (MSC)-conditioned medium (MSC-CM) in the fracture-healing process of CD9 2/2 mice, a strain that is known to produce reduced levels of exosomes. Retardation of fracture healing in CD9 2/2 mice was rescued by the injection of MSC exosomes, but this was not the case after the injection of exosome-free CM. This study finds that MSC exosomes are a novel factor of MSC paracrine signaling, with an important role in the tissue repair process.

a b s t r a c tMesenchymal stem cell (MSC) transplantation is used for treatment of many diseases. The paracrine role of MSCs in tissue regeneration is attracting particular attention. We investigate the role of MSC exosomes in skeletal muscle regeneration. MSC exosomes promote myogenesis and angiogenesis in vitro, and muscle regeneration in an in vivo model of muscle injury. Although MSC exosomes had low concentrations of muscle-repair-related cytokines, a number of repair-related miRNAs were identified. This study suggests that the MSC-derived exosomes promote muscle regeneration by enhancing myogenesis and angiogenesis, which is at least in part mediated by miRNAs such as miR-494.

Objective. A role of microRNA, which are ϳ22-nucleotide noncoding RNAs, has recently been recognized in human diseases. The objective of this study was to identify the expression pattern of microRNA-146a (miR-146a) in cartilage from patients with osteoarthritis (OA).Methods. The expression of miR-146a in cartilage from 15 patients with OA was analyzed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) and by in situ hybridization. Induction of the expression of miR-146a by cultures of normal human articular chondrocytes following stimulation with interleukin-1␤ (IL-1␤) was examined by quantitative RT-PCR.Results. All cartilage samples were divided into 3 groups according to a modification of the Mankin score (grade I ‫؍‬ mild OA scored 0-5, grade II ‫؍‬ moderate OA scored 6-10, and grade III ‫؍‬ severe OA scored 11-14). In grade I OA cartilage samples, the expression of miR-146a and COL2A1 was significantly higher than that in the other groups (P < 0.05). In grades II and III OA cartilage, the expression of miR-146a and COL2A1 was decreased, whereas the expression of matrix metalloproteinase 13 (MMP-13) was elevated in grade II OA cartilage. These data showed that miR-146a is expressed intensely in cartilage with a low Mankin grade and that miR-146a expression decreases in parallel with the level of MMP-13 expression. Tissue section in situ hybridization of primary miR-146a (pri-miR-146a) revealed that pri-miR-146a was expressed in chondrocytes residing in all tissue layers, especially in the superficial layer, where it was intensely expressed. The expression of miR-146 was markedly elevated by IL-1␤ stimulation in human chondrocytes in vitro. Conclusion. This study shows that miR-146 is intensely expressed in low-grade OA cartilage and that its expression is induced by stimulation of IL-1␤. Thus, miR-146 might play a role in OA cartilage pathogenesis.Osteoarthritis (OA) is a highly prevalent disease that is characterized by progressive degeneration of articular cartilage (1-4). Although little is known about the pathogenesis of OA, an imbalance between anabolic and catabolic factors that maintain the homeostasis of cartilage is thought to lead to cartilage degradation. While there is a delicate balance between anabolism and catabolism in the strict regulation of matrix turnover in normal cartilage, catabolism becomes dominant over anabolism in OA cartilage, leading to the degradation of cartilage. Several studies have demonstrated an interaction between anabolic factors, such as transforming growth factor ␤, and catabolic factors, such as matrix metalloproteinases (MMPs) and aggrecanases, in chondrocytes; however, the molecular mechanisms involved in OA remain unclear (5).MicroRNA (miRNA) are a family of ϳ22-nucleotide noncoding RNAs identified in organisms ranging from nematodes to humans (6-8). Many miRNA are evolutionarily conserved across phyla, regulating gene expression by posttranscriptional gene repression. The miRNA regulate gene expression by binding the 3Ј-untranslated region of...

In 52 patients we compared the accuracy of standard anteroposterior (AP) radiography, mortise radiography and MRI with arthroscopy of the ankle for the diagnosis of a tear of the tibiofibular syndesmosis. In comparison with arthroscopy, the sensitivity, specificity and accuracy were 44.1%, 100% and 63.5% for standard AP radiography and 58.3%, 100% and 71.2% for mortise radiography. For MRI they were 100%, 93.1% and 96.2% for a tear of the anterior inferior tibiofibular ligament and 100%, 100% and 100% for a tear of the posterior inferior tibiofibular ligament. Standard AP and mortise radiography did not always provide a correct diagnosis. MRI was useful although there were two-false positive cases. We suggest that arthroscopy of the ankle is indispensable for the accurate diagnosis of a tear of the tibiofibular syndesmosis.