BackgroundMicroRNAs are short regulatory RNAs that negatively modulate protein expression at a post-transcriptional and/or translational level and are deeply involved in the pathogenesis of several types of cancers. Specifically, microRNA-221 (miR-221) is overexpressed in many human cancers, wherein accumulating evidence indicates that it functions as an oncogene. However, the function of miR-221 in human osteosarcoma has not been totally elucidated. In the present study, the effects of miR-221 on osteosarcoma and the possible mechanism by which miR-221 affected the survival, apoptosis, and cisplatin resistance of osteosarcoma were investigated.Methodology/Principal FindingsReal-time quantitative PCR analysis revealed miR-221 was significantly upregulated in osteosarcoma cell lines than in osteoblasts. Both human osteosarcoma cell lines SOSP-9607 and MG63 were transfected with miR-221 mimic or inhibitor to regulate miR-221 expression. The effects of miR-221 were then assessed by cell viability, cell cycle analysis, apoptosis assay, and cisplatin resistance assay. In both cells, upregulation of miR-221 induced cell survival and cisplatin resistance and reduced cell apoptosis. In addition, knockdown of miR-221 inhibited cell growth and cisplatin resistance and induced cell apoptosis. Potential target genes of miR-221 were predicted using bioinformatics. Moreover, luciferase reporter assay and western blot confirmed that PTEN was a direct target of miR-221. Furthermore, introduction of PTEN cDNA lacking 3′-UTR or PI3K inhibitor LY294002 abrogated miR-221-induced cisplatin resistance. Finally, both miR-221 and PTEN expression levels in osteosarcoma samples were examined by using real-time quantitative PCR and immunohistochemistry. High miR-221 expression level and inverse correlation between miR-221 and PTEN levels were revealed in osteosarcoma tissues.Conclusions/SignificanceThese results for the first time demonstrate that upregulation of miR-221 induces the malignant phenotype of human osteosarcoma whereas knockdown of miR-221 reverses this phenotype, suggesting that miR-221 could be a potential target for osteosarcoma treatment.

Osteosarcoma, the most common primary tumor of the bones, causes many deaths due to its rapid proliferation and drug resistance. Recent studies have shown that cyclin D1 plays a key regulatory role during cell proliferation, and non-coding microRNAs (miRNAs) act as crucial modulators of cyclin D1 (CCND1). The aim of the current study was to determine the role of miRNAs in controlling CCND1 expression and inducing cell apoptosis. CCND1 has been found to be a target of miR-15a and miR-16-1 through analysis of complementary sequences between microRNAs and CCND1 mRNA. The upregulation of miR-15a and miR-16-1 in the cell line SOSP-9607 induces apoptosis and cell cycle arrest. Osteosarcoma cells transfected with miR-15a and miR-16-1 show slower proliferation curves. Moreover, the transcription of CCND1 is suppressed by miR-15a and miR-16-1 via direct binding to the CCND1 3'-untranslated region (3'-UTR). The data presented here demonstrate that the CCND1 contributes to osteosarcoma cell proliferation, suggesting that repression of CCND1 by miR-15a and miR-16-1 could be used for osteosarcoma therapy.

BackgroundCellular adaptation to a hypoxic microenvironment is essential for tumor progression and is largely mediated by HIF-1α through coordinated regulation of hypoxia-responsive genes. The chemokine SDF-1α and its unique receptor CXCR4 have been implicated in organ-specific metastases of many cancers. In this study, we investigated the response of osteosarcoma cells to hypoxia and the expression of CXCR4 and HIF-1α in human osteosarcoma specimens and explored the roles of CXCR4 and HIF-1α in the cell migration process.Methodology/Principal FindingsWe performed immunohistochemistry, immunocytochemistry, quantitative real-time PCR, Western blots and fluorescent reporter assays to evaluate the correlation between CXCR4 and HIF-1α expression in human osteosarcoma specimens or SOSP-9607 cells under normoxic and hypoxic conditions. Transwell assays were used to assess cell migration under different conditions. Exposure of SOSP-9607 cells to hypoxic conditions resulted in significantly increased migration. When SOSP-9607 cells were subjected to hypoxic conditions, the mRNA and protein levels of CXCR4 were significantly increased in a time-dependent manner. Moreover, siHIF-1α significantly decreased the mRNA and protein levels of CXCR4 under hypoxia, whereas pcDNA-HIF-1α significantly increased the mRNA and protein levels of CXCR4 under normoxia. A luciferase reporter gene study showed that siHIF-1α reduced pGL3-CXCR4 luciferase activity. Furthermore, coexpression of HIF-1α and CXCR4 was significantly higher in patients with distant metastasis compared with those without metastasis.Conclusions/SignificanceThe hypoxia-HIF-1α-CXCR4 pathway plays a crucial role during the migration of human osteosarcoma cells, and targeting this pathway might represent a novel therapeutic strategy for patients suffering from osteosarcoma.

Osteosarcoma is the most common primary malignancy of bone in teenagers and approximately 30% of patients develop lung metastasis, which is the leading cause of mortality. Recent studies suggest that the Ezrin protein is correlated with the metastatic potential of several malignant tumors. In our study, ectopic overexpression of miR-183 repressed the expression levels of Ezrin and significantly inhibited the motility and invasion of osteosarcoma cells. This suggests that miR-183 may possibly play a tumor suppressor role in the metastasis of osteosarcoma by downregulating Ezrin expression levels. These findings show that through inhibition of Ezrin expression levels, miR-183 is significantly involved in cell migration and invasion of osteosarcoma.

Mechanical overloading is a major cause of tendinopathy, but the underlying pathogenesis of tendinopathy is unclear. Here we report that high mobility group box1 (HMGB1) is released to the tendon extracellular matrix and initiates an inflammatory cascade in response to mechanical overloading in a mouse model. Moreover, administration of glycyrrhizin (GL), a naturally occurring triterpene and a specific inhibitor of HMGB1, inhibits the tendon’s inflammatory reactions. Also, while prolonged mechanical overloading in the form of long-term intensive treadmill running induces Achilles tendinopathy in mice, administration of GL completely blocks the tendinopathy development. Additionally, mechanical overloading of tendon cells in vitro induces HMGB1 release to the extracellular milieu, thereby eliciting inflammatory and catabolic responses as marked by increased production of prostaglandin E2 (PGE2) and matrix metalloproteinase-3 (MMP-3) in tendon cells. Application of GL abolishes the cellular inflammatory/catabolic responses. Collectively, these findings point to HMGB1 as a key molecule that is responsible for the induction of tendinopathy due to mechanical overloading placed on the tendon.

Treatment of tendon-bone junction injuries is a challenge because tendon-bone interface often heals poorly and the fibrocartilage zone, which reduces stress concentration, at the interface is not formed. In this study, we used a compound called kartogenin (KGN) with platelet-rich plasma (PRP) to induce the formation of fibrocartilage zone in a rat tendon graft-bone tunnel model. The experimental rats received KGN-PRP or PRP injections in the tendon graft-bone tunnel interface. The control group received saline. After 4, 8 and 12 weeks, Safranin O staining of the tendon graft-bone tunnels revealed abundant proteoglycans in the KGN-PRP group indicating the formation of cartilage-like transition zone. Immunohistochemical and immuno-fluorescence staining revealed collagen types I (Col-I) and II (Col-II) in the newly formed fibrocartilage zone. Both fibrocartilage zone formation and maturation were healing time dependent. In contrast, the PRP and saline control groups had no cartilage-like tissues and minimal Col-I and Col-II staining. Some gaps were also present in the saline control group. Finally, pull-out strength in the KGN-PRP-treated group at 8 weeks was 1.4-fold higher than the PRP-treated group and 1.6-fold higher than the saline control group. These findings indicate that KGN, with PRP as a carrier, promotes the formation of fibrocartilage zone between the tendon graft and bone interface. Thus, KGN-PRP may be used as a convenient cell-free therapy in clinics to promote fibrocartilage zone formation in rotator calf repair and anterior cruciate ligament reconstruction, thereby enhancing the mechanical strength of the tendon-bone interface and hence the clinical outcome of these procedures. Copyright

15 Mechanical overloading is a major cause of tendinopathy, but the underlying pathogenesis of 16 tendinopathy is unclear. Here we report that high mobility group box1 (HMGB1) is released to 17 the tendon extracellular matrix and initiates an inflammatory cascade in response to mechanical 18 overloading in a mouse model. Moreover, administration of glycyrrhizin (GL), a naturally 19 occurring triterpene and a specific inhibitor of HMGB1, the tendon's inflammatory reactions.20 Also, while prolonged mechanical overloading in the form of long-term intensive treadmill 21 running induces Achilles tendinopathy in mice, administration of GL completely blocks the 22 tendinopathy development. Additionally, mechanical overloading of tendon cells in vitro induces 23 HMGB1 release to the extracellular milieu, thereby eliciting inflammatory and catabolic 24 responses as marked by increased production of prostaglandin E 2 (PGE 2 ) and matrix 25 metalloproteinase-3 (MMP-3) in tendon cells. Application of GL abolishes the cellular 26 inflammatory/catabolic responses. Collectively, these findings point to HMGB1 as a key 27 molecule that is responsible for the induction of tendinopathy due to mechanical overloading 28 placed on the tendon. 29 Keywords: Mechanical overloading, HMGB1, tendinopathy, tendon inflammation, tendon 30 degeneration, glycyrrhizin 31 32 Introduction 33 34Tendinopathy, a debilitating chronic tendon disorder, is manifested in clinical settings by 35 a combination of pain, swelling, compromised tendon structure, and rupture (1). Tendinopathy, 36 which involves tendon inflammation and degeneration, affects healthy individuals during their 37 active and productive years of life resulting in tremendous healthcare costs and economic impact 38 due to work-loss (2, 3). In particular, insertional tendinopathy, which is common in young 39 athletes, often occurs in the tendon proper proximal to the insertion into the heel bone and 40 accounts for about 20% of Achilles tendon disorders (4). It is well established that while normal 41 physiological loading is essential for tendon homeostasis, mechanical overloading induces the 42 development of tendinopathy, characterized by disorganized matrix, reduced numbers and 43 rounding of tendon cells, fibrocartilaginous change, and neovascularization (5, 6). A current 44 concept on the mechanisms of tendinopathy is that repetitive loading may lead to a 45 mechanobiological over-stimulation of tendon cells resulting in an imbalance between the 46 synthesis and breakdown of matrix proteins, especially collagen (7-9). The resulting mismatch is 47 a continuous loss of collagen in the tendon by repetitive loading with insufficient recovery time, 48 which initiates a catabolic degenerative response that leads to tendinopathy (6, 10). 50It is now recognized that inflammation is part of tendinopathy and could lead to tendon 51 degeneration that occurs at late stages of tendinopathy (11)(12)(13). Under excessive mechanical 52 loading, abnormal levels of proinflammatory mediators may be rel...

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