MicroRNA-34a modulates cytoskeletal dynamics through regulating RhoA/Rac1 cross-talk in chondroblasts

Receptor tyrosine kinase ROR1 ameliorates Aβ1-42 induced cytoskeletal instability and is regulated by the miR146a-NEAT1 nexus in Alzheimer's disease

Alzheimer’s disease (AD) involves severe cytoskeletal degradation and microtubule disruption. Here, we studied the altered dynamics of ROR1, a Receptor Tyrosine Kinase (RTK), and how it could counter these abnormalities. We found that in an Aβ_1–42 treated cell model of AD, ROR1 was significantly decreased. Over expressed ROR1 led to the abrogation of cytoskeletal protein degradation, even in the presence of Aβ_1–42, preserved the actin network, altered actin dynamics and promoted neuritogenesis. Bioinformatically predicted miRNAs hsa-miR-146a and 34a were strongly up regulated in the cell model and their over expression repressed ROR1. LncRNA NEAT1, an interactor of these miRNAs, was elevated in mice AD brain and cell model concordantly. RNA Immunoprecipitation confirmed a physical interaction between the miRNAs and NEAT1. Intuitively, a transient knock down of NEAT1 increased their levels. To our knowledge, this is the first instance which implicates ROR1 in AD and proposes its role in preserving the cytoskeleton. The signalling modalities are uniquely analyzed from the regulatory perspectives with miR-146a and miR-34a repressing ROR1 and in turn getting regulated by NEAT1.

MicroRNA-340 is involved in ultraviolet B-induced pigmentation by regulating the MITF/TYRP1 axis

Objective

There is growing evidence that ultraviolet B (UVB) irradiation can change the expression profile of microRNAs (miRNAs) in immortalized human epidermal melanocytes (Pig-1). We aimed to investigate the effect of miR-340 on regulating UVB-induced pigmentation.

Methods

Real-time quantitative PCR (qRT-PCR) was used to evaluate the expression of miR-340 in Pig-1 cells. Immunoblotting analysis, qRT-PCR, and luciferase reporter assays were used to detect the potential target of miR-340. The sodium hydroxide dissolution assay was used to assess the effect of miR-340 on changes in melanin content.

Results

Expression of miR-340 was reduced in human Pig-1 cells after UVB irradiation. We found a negative correlation between miR-340 and melanocyte inducing transcription factor (MITF) in Pig-1 cells after UVB irradiation. Knockdown and overexpression of MITF in Pig-1 cells down- and upregulated melanogenesis, respectively. Overexpression of miR-340 inhibited MITF expression, reduced the amount of melanin, and suppressed expression of multiple key molecules involved in the pigment synthesis pathway, whereas knockdown of miR-340 showed the opposite results.

Conclusions

Our results showed that miR-340 inhibited melanogenesis by regulating the downstream molecules of MITF and its signaling pathways, suggested that miRNA-340 may be a new target for the clinical treatment of UVB-induced pigmentation.

Chitosan/polycaprolactone multilayer hydrogel: A sustained Kartogenin delivery model for cartilage regeneration

Cartilage regeneration using biomaterial-guided delivery systems presents improved therapeutic efficacy of the biomolecules while minimizing side effects. Here, our hypothesis was to design a multilayer scaffold of chitosan (CS) hydrogel and polycaprolactone (PCL) mat to enhance the mechanical properties, integrity and stability of CS, especially for subsequent in vivo transplantation. After conjugation of the Kartogenin (KGN) into this structure, its gradual release can promote chondrogenesis of mesenchymal stem cells (MSCs). Initially, a thin electrospun PCL layer was sandwiched between two CS hydrogels. Subsequently, KGN was superficially immobilized onto the CS matrix. The successful conjugation was confirmed by scanning electron microscopy (SEM) and infrared spectroscopy. These novel KGN-conjugated scaffolds possessed lower swelling and higher compressive modulus and showed gradual release of KGN in longer retention times. Immunofluorescent and histological staining represented more cells located in lacunae as well as more Coll2 and Sox9 positive cells on KGN-conjugated scaffolds. Gene expression analysis also revealed that SOX9, COLL2 and ACAN expression levels were higher in the presence of KGN, while COLLX expression was down-regulated, indicating a hypertrophy phenomenon with synergistic effect of TGF-β. This multilayer structure not only facilitates the effective treatment, but also provides a proper mechanical structure for cartilage engineering.

Kartogenin hydrolysis product 4-aminobiphenyl distributes to cartilage and mediates cartilage regeneration

Rationale The small molecule Kartogenin (KGN) promotes cartilage regeneration in osteoarthritis (OA) by activating stem cells differentiation, but its pharmacological mode-of-action remains unclear. KGN can be cleaved into 4-aminobiphenyl (4-ABP) and phthalic acid (PA) following enzymolysis of an amide bond. Therefore, this study investigated whether 4-ABP or PA exerted the same action as KGN. Methods KGN, 4-ABP and PA were analyzed in cartilage of mice after oral, intravenous or intra-articular administration of KGN by liquid chromatography-mass spectrometry method. Their effect on proliferation and chondrogenic differentiation of mesenchymal stem cells (MSC) was evaluated in vitro. Furthermore, their effect on cartilage preservation was tested in mice OA model induced by destabilization of medial meniscus. OA severity was quantified using OARSI histological scoring. Transcriptional analysis was used to find the possible targets of the chemicals, which were further validated. Results We demonstrated that while oral or intra-articular KGN delivery effectively ameliorated OA phenotypes in mice, only 4-ABP was detectable in cartilage. 4-ABP could induce chondrogenic differentiation and proliferation of MSC in vitro and promote cartilage repair in OA mouse models mainly by increasing the number of CD44⁺/CD105⁺ stem-cell and prevention of matrix loss. These effect of 4-ABP was stronger than that of KGN. Transcriptional profiling of 4-ABP-stimulated MSC suggested that RPS6KA2 and the PI3K-Akt pathway were 4-ABP targets; 4-ABP could activate the PI3K-Akt pathway to promote MSC proliferation and repair OA injury, which was blocked in RPS6KA2-knockdown MSC or RPS6KA2-deficient mice. Conclusion 4-ABP bio-distribution in cartilage promotes proliferation and chondrogenic differentiation of MSC, and repairs osteoarthritic lesions via PI3K-Akt pathway activation.

Nanoparticle-Cell Interaction: A Cell Mechanics Perspective

Progress in the field of nanoparticles has enabled the rapid development of multiple products and technologies; however, some nanoparticles can pose both a threat to the environment and human health. To enable their safe implementation, a comprehensive knowledge of nanoparticles and their biological interactions is needed. In vitro and in vivo toxicity tests have been considered the gold standard to evaluate nanoparticle safety, but it is becoming necessary to understand the impact of nanosystems on cell mechanics. Here, the interaction between particles and cells, from the point of view of cell mechanics (i.e., bionanomechanics), is highlighted and put in perspective. Specifically, the ability of intracellular and extracellular nanoparticles to impair cell adhesion, cytoskeletal organization, stiffness, and migration are discussed. Furthermore, the development of cutting-edge, nanotechnology-driven tools based on the use of particles allowing the determination of cell mechanics is emphasized. These include traction force microscopy, colloidal probe atomic force microscopy, optical tweezers, magnetic manipulation, and particle tracking microrheology.

Regulation of RhoA GTPase and various transcription factors in the RhoA pathway

RhoA GTPase plays a variety of functions in regulation of cytoskeletal proteins, cellular morphology, and migration along with various proliferation and transcriptional activity in cells. RhoA activity is regulated by guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs), and the guanine nucleotide dissociation factor (GDI). The RhoA-RhoGDI complex exists in the cytosol and the active GTP-bound form of RhoA is located to the membrane. GDI displacement factors (GDFs) including IκB kinase γ (IKKγ) dissociate the RhoA-GDI complex, allowing activation of RhoA through GEFs. In addition, modifications of Tyr42 phosphorylation and Cys16/20 oxidation in RhoA and Tyr156 phosphorylation and oxidation of RhoGDI promote the dissociation of the RhoA-RhoGDI complex. The expression of RhoA is regulated through transcriptional factors such as c-Myc, HIF-1α/2α, Stat 6, and NF-κB along with several reported microRNAs. As the role of RhoA in regulating actin-filament formation and myosin-actin interaction has been well described, in this review we focus on the transcriptional activity of RhoA and also the regulation of RhoA message itself. Of interest, in the cytosol, activated RhoA induces transcriptional changes through filamentous actin (F-actin)-dependent ("actin switch") or-independent means. RhoA regulates the activity of several transcription regulators such as serum response factor (SRF)/MAL, AP-1, NF-κB, YAP/TAZ, β-catenin, and hypoxia inducible factor (HIF)-1α. Interestingly, RhoA also itself is localized to the nucleus by an as-yet-undiscovered mechanism.

Glucose enhances aggrecan expression in chondrocytes via the PKCα/p38-miR141-3p signaling pathway

Aggrecan is a high molecular weight proteoglycan that plays a critical role in cartilage structure and the function of joints, providing intervertebral disc and cartilage with the ability to resist compressive loads. Aggrecan degradation in articular cartilage is a significant event in early-stage osteoarthritis (OA). Currently, no effective treatment exists for OA other than pain relief. Dextrose (D-glucose) prolotherapy has shown promising activity in the treatment of different musculoskeletal disorders, including OA. However, little is known about the molecular mechanism of the glucose effect in OA and on the regulation of chondrogenesis. We show for the first time that glucose upregulates aggrecan expression and subsequent chondrogenesis in ATDC5 cells. Moreover, we found that glucose-induced aggrecan expression is mediated through the protein kinase Cα (PKCα)- and p38-dependent pathway. As demonstrated by microRNA (miR) and luciferase analyses, the glucose-induced PKCα/p38 signaling axis is responsible for downregulating miR141-3p which targets to the 3'untranslated region of aggrecan. In summary, we show that glucose enhances chondrogenesis by upregulating aggrecan expression via the PKCα-p38-miR141-3p signaling pathway. This result provides new insights into the mechanism of glucose on chondrogenesis.

Emerging potential of gene silencing approaches targeting anti-chondrogenic factors for cell-based cartilage repair

The field of cartilage repair has exponentially been growing over the past decade. Here, we discuss the possibility to achieve satisfactory regeneration of articular cartilage by means of human mesenchymal stem cells (hMSCs) depleted of anti-chondrogenic factors and implanted in the site of injury. Different types of molecules including transcription factors, transcriptional co-regulators, secreted proteins, and microRNAs have recently been identified as negative modulators of chondroprogenitor differentiation and chondrocyte function. We review the current knowledge about these molecules as potential targets for gene knockdown strategies using RNA interference (RNAi) tools that allow the specific suppression of gene function. The critical issues regarding the optimization of the gene silencing approach as well as the delivery strategies are discussed. We anticipate that further development of these techniques will lead to the generation of implantable hMSCs with enhanced potential to regenerate articular cartilage damaged by injury, disease, or aging.

Inhibition of microRNA-34a ameliorates murine collagen-induced arthritis

Rheumatoid arthritis (RA) is one of the most frequently occurring autoimmne diseases, with symptoms including synovium hyperplasia, immune disorder, cartilage damage and bone resorption. It has previously been demonstrated that microRNA-34a (miR-34a) may participate in cell apoptosis, immune activation and bone metabolism, therefore the present study investigated the effects of miR-34a on RA. Collagen-induced arthritic (CIA) mice were employed as a murine model of experimental arthritis, and it was demonstrated that the level of miR-34a in the spleens, lymph nodes and synovium was increased in the CIA mice compared with normal DBA/1j mice. Administration of miR-34a antagomir, the chemically modified inhibitor, ameliorated CIA and delayed the onset of symptoms. Arthritis scores decreased and joint swelling was alleviated with the miR-34a antagomir treatment and the expression of inflammatory cytokines was decreased. miR-34a antagomir delivery significantly decreased the percentage of T cells present including T helper (Th) 1, Th2, Th17 and regulatory T cells. Furthermore miR-34a antagomir-treated CIA mice demonstrated decreased inflammatory-induced bone loss. Overall, it was observed that inhibition of miR-34a ameliorated murine arthritis, downregulated T cell percentage and cytokine expression, and suppressed bone loss. The experimental results suggest that inhibition of miR-34a may offer a novel alternative for the treatment of RA.

Stromal cell-derived factor-1α and transforming growth factor-β1 synergistically facilitate migration and chondrogenesis of synovium-derived stem cells through MAPK pathways

The clinical translation of tissue engineering methods is confined by the limited external cell sources, which is hopefully to be addressed by the cell guidance approach as cytokine-induced homing and differentiation of the patients' autologous cells. Synovium-derived stem cells (SDSCs) are a potent cell source for cartilage restoration due to its intrinsic proximity and tissue-specific chondrogenic capacity. In this study, stromal cell-derived factor-1α (SDF-1α) in combination with transforming growth factor β₁ (TGF-β₁) were used to induce SDSCs migration and chondrogenesis in vitro. The migration capacity was evaluated by transwell assay and for chondrogenic evaluation, the expression of Sox9, ACAN and COL2A1 were assessed by quantitative RT-PCR while the expression of sulfated GAG and collagen II were evaluated by Alcian Blue stain and immunohistochemistry respectively. Our data showed that SDF-1α/CXC chemokine receptor 4 (CXCR4) was involved in SDSCs migration through phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. Exogenous TGF-β₁ enhanced SDF-1α-induced SDSCs migration in a concentration and time-dependent manner through CXCR4, evidenced as complete blockage by AMD3100, the CXCR4 antagonist and this effect was mediated by extracellular regulated protein kinases (ERK) activation. Moreover, the addition of SDF-1α augmented the TGF-β₁-induced SDSCs chondrogenesis, evidenced by the increased pellet sizes and the expressions of COL 2A1, ACAN and Sox9. This effect was related to c-Jun N-terminal kinase (JNK) activation. Collectively, these results suggest that SDF-1α and TGF-β₁ interacts with each other and synergistically enhance the SDSCs migration and chondrogenesis through MAPK pathways.

Functions of Rho family of small GTPases and Rho-associated coiled-coil kinases in bone cells during differentiation and mineralization

BACKGROUND

Members of Rho-associated coiled-coil kinases (ROCKs) are effectors of Rho family of small GTPases. ROCKs have multiple functions that include regulation of cellular contraction and polarity, adhesion, motility, proliferation, apoptosis, differentiation, maturation and remodeling of the extracellular matrix (ECM).

SCOPE OF THE REVIEW

Here, we focus on the action of RhoA and RhoA effectors, ROCK1 and ROCK2, in cells related to tissue mineralization: mesenchymal stem cells, chondrocytes, preosteoblasts, osteoblasts, osteocytes, lining cells and osteoclasts.

MAJOR CONCLUSIONS

The activation of the RhoA/ROCK pathway promotes stress fiber formation and reduces chondrocyte and osteogenic differentiations, in contrast to that in mesenchymal stem cells which stimulated the osteogenic and the chondrogenic differentiation. The effects of Rac1 and Cdc42 in promoting chondrocyte hypertrophy and of Rac1, Rac2 and Cdc42 in osteoclast are discussed. In addition, members of the Rho family of GTPases such Rac1, Rac2, Rac3 and Cdc42, acting upstream of ROCK and/or other protein effectors, may compensate the actions of RhoA, affecting directly or indirectly the actions of ROCKs as well as other protein effectors.

GENERAL SIGNIFICANCE

ROCK activity can trigger cartilage degradation and affect bone formation, therefore these kinases may represent a possible therapeutic target to treat osteoarthritis and osseous diseases. Inhibition of Rho/ROCK activity in chondrocytes prevents cartilage degradation, stimulate mineralization of osteoblasts and facilitate bone formation around implanted metals. Treatment with osteoprotegerin results in a significant decrease in the expression of Rho GTPases, ROCK1 and ROCK2, reducing bone resorption. Inhibition of ROCK signaling increases osteoblast differentiation in a topography-dependent manner.

MicroRNA-9 regulates the development of knee osteoarthritis through the NF-kappaB1 pathway in chondrocytes

It has been suggested that microRNA-9 (miR-9) is associated with the development of knee osteoarthritis (OA). This study was aimed to investigate the association between the mechanism of miR-9 targeting nuclear factor kappa-B1 (NF-κB1) and the proliferation and apoptosis of knee OA chondrocytes.Cartilage samples were collected from 25 patients with knee OA and 10 traumatic amputees, and another 15 OA rat models, together with 15 rats without knee OA lesions were also established. MiR-9 expressions in both knee OA cartilage and normal cartilage samples were detected using quantitative real-time PCR. The expressions of related genes (NF-κB1, IL-6, and MMP-13) in the two groups were also detected. Dual luciferase reporter gene assay was employed to examine the effect of miR-9 on the luciferase activity of NF-κB1 3'UTR. Knee OA chondrocytes were transfected with miR-9 mimics, miR-9 inhibitor, and NF-κB1 siRNA, respectively, and changes in cellular proliferation and apoptosis were detected via MTT assay and flow cytometric analysis, respectively. Western blotting assay was used to detect the expressions of NF-κB1, interleukin-6 (IL-6), and matrix metalloproteinase-13 (MMP-13).According to results from human OA samples and rat OA models, miR-9 was significantly downregulated in knee OA cartilage tissues compared with normal cartilage tissues (P < 0.01). The expressions of NF-κB1, IL-6, and MMP-13 in knee OA cartilage tissues were significantly higher than those in normal cartilage tissues (P < 0.01). Dual luciferase reporter gene assay showed that miR-9 could bind to the 3'UTR of NF-κB1 and significantly inhibit the luciferase activity by 37% (P < 0.01). Upregulation of miR-9 or downregulation of NF-κB1 could promote cell proliferation and suppress cell apoptosis.Conclusively, downregulated miR-9 can facilitate proliferation and antiapoptosis of knee OA chondrocytes by directly binding to NF-kB1, implying that stimulating miR-9 expressions might assist in treatment of knee OA.

Epigenetic dynamics of monocyte-to-macrophage differentiation

Background

Monocyte-to-macrophage differentiation involves major biochemical and structural changes. In order to elucidate the role of gene regulatory changes during this process, we used high-throughput sequencing to analyze the complete transcriptome and epigenome of human monocytes that were differentiated in vitro by addition of colony-stimulating factor 1 in serum-free medium.

Results

Numerous mRNAs and miRNAs were significantly up- or down-regulated. More than 100 discrete DNA regions, most often far away from transcription start sites, were rapidly demethylated by the ten eleven translocation enzymes, became nucleosome-free and gained histone marks indicative of active enhancers. These regions were unique for macrophages and associated with genes involved in the regulation of the actin cytoskeleton, phagocytosis and innate immune response.

Conclusions

In summary, we have discovered a phagocytic gene network that is repressed by DNA methylation in monocytes and rapidly de-repressed after the onset of macrophage differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13072-016-0079-z) contains supplementary material, which is available to authorized users.

Modeling the Transitions between Collective and Solitary Migration Phenotypes in Cancer Metastasis

Cellular plasticity during cancer metastasis is a major clinical challenge. Two key cellular plasticity mechanisms —Epithelial-to-Mesenchymal Transition (EMT) and Mesenchymal-to-Amoeboid Transition (MAT) – have been carefully investigated individually, yet a comprehensive understanding of their interconnections remains elusive. Previously, we have modeled the dynamics of the core regulatory circuits for both EMT (miR-200/ZEB/miR-34/SNAIL) and MAT (Rac1/RhoA). We now extend our previous work to study the coupling between these two core circuits by considering the two microRNAs (miR-200 and miR-34) as external signals to the core MAT circuit. We show that this coupled circuit enables four different stable steady states (phenotypes) that correspond to hybrid epithelial/mesenchymal (E/M), mesenchymal (M), amoeboid (A) and hybrid amoeboid/mesenchymal (A/M) phenotypes. Our model recapitulates the metastasis-suppressing role of the microRNAs even in the presence of EMT-inducing signals like Hepatocyte Growth Factor (HGF). It also enables mapping the microRNA levels to the transitions among various cell migration phenotypes. Finally, it offers a mechanistic understanding for the observed phenotypic transitions among different cell migration phenotypes, specifically the Collective-to-Amoeboid Transition (CAT).

miR-34/449 control apical actin network formation during multiciliogenesis through small GTPase pathways

Vertebrate multiciliated cells (MCCs) contribute to fluid propulsion in several biological processes. We previously showed that microRNAs of the miR-34/449 family trigger MCC differentiation by repressing cell cycle genes and the Notch pathway. Here, using human and Xenopus MCCs, we show that beyond this initial step, miR-34/449 later promote the assembly of an apical actin network, required for proper basal bodies anchoring. Identification of miR-34/449 targets related to small GTPase pathways led us to characterize R-Ras as a key regulator of this process. Protection of RRAS messenger RNA against miR-34/449 binding impairs actin cap formation and multiciliogenesis, despite a still active RhoA. We propose that miR-34/449 also promote relocalization of the actin binding protein Filamin-A, a known RRAS interactor, near basal bodies in MCCs. Our study illustrates the intricate role played by miR-34/449 in coordinating several steps of a complex differentiation programme by regulating distinct signalling pathways.

MicroRNAs of the miR-34/449 family initiate formation of multiciliated cells through the suppression of cell cycle genes and Notch. Here the authors show that miR-34/449 also regulate the assembly of an apical actin network necessary for basal body anchoring by regulating the expression of R-Ras.

Implications of the Hybrid Epithelial/Mesenchymal Phenotype in Metastasis

Transitions between epithelial and mesenchymal phenotypes – the epithelial to ­mesenchymal transition (EMT) and its reverse the mesenchymal to epithelial transition (MET) – are hallmarks of cancer metastasis. While transitioning between the epithelial and mesenchymal phenotypes, cells can also attain a hybrid epithelial/mesenchymal (E/M) (i.e., partial or intermediate EMT) phenotype. Cells in this phenotype have mixed epithelial (e.g., adhesion) and mesenchymal (e.g., migration) properties, thereby allowing them to move collectively as clusters. If these clusters reach the bloodstream intact, they can give rise to clusters of circulating tumor cells (CTCs), as have often been seen experimentally. Here, we review the operating principles of the core regulatory network for EMT/MET that acts as a “three-way” switch giving rise to three distinct phenotypes – E, M and hybrid E/M – and present a theoretical framework that can elucidate the role of many other players in regulating epithelial plasticity. Furthermore, we highlight recent studies on partial EMT and its association with drug resistance and tumor-initiating potential; and discuss how cell–cell communication between cells in a partial EMT phenotype can enable the formation of clusters of CTCs. These clusters can be more apoptosis-resistant and have more tumor-initiating potential than singly moving CTCs with a wholly mesenchymal (complete EMT) phenotype. Also, more such clusters can be formed under inflammatory conditions that are often generated by various therapies. Finally, we discuss the multiple advantages that the partial EMT or hybrid E/M phenotype have as compared to a complete EMT phenotype and argue that these collectively migrating cells are the primary “bad actors” of metastasis.

Bone marrow stroma-derived miRNAs as regulators, biomarkers and therapeutic targets of bone metastasis

MicroRNAs (miRNAs) are short, endogenous RNA molecules that have essential roles in regulating gene expression. They control numerous physiological and cellular processes, including normal bone organogenesis and homeostasis, by enhancing or inhibiting bone marrow cell growth, differentiation, functional activity and crosstalk of the multiple cell types within the bone. Hence, elucidating miRNA targets in bone marrow stromal cells has revealed novel regulations during bone development and maintenance. Moreover, recent studies have detailed the capacity for bone stromal miRNAs to influence bone metastasis from a number of primary carcinomas by interfering with bone homeostasis or by directly influencing metastatic tumor cells. Owing to the current lack of good diagnostic biomarkers of bone metastases, such changes in bone stromal miRNA expression in the presence of metastatic lesions may become useful biomarkers, and may even serve as therapeutic targets. In particular, cell-free and exosomal miRNAs shed from bone stromal cells into circulation may be developed into novel biomarkers that can be routinely measured in easily accessible samples. Taken together, these findings reveal the significant role of bone marrow stroma-derived miRNAs in the regulation of bone homeostasis and bone metastasis.

Toward decoding the principles of cancer metastasis circuits

Understanding epithelial-mesenchymal transitions (EMT) during cancer metastasis remains a major challenge in modern biology. Recent observations of cell behavior together with progress in mapping the underlying regulatory genetic networks led to new understandings of carcinoma metastasis. It is now established that the genetic network that regulates the EMT also enables an epithelial-mesenchymal hybrid phenotype. These hybrid cells possess mixed carcinoma epithelial and mesenchymal characteristics that enable specialized capabilities such as collective cell migration. On the gene network perspective, a four-component decision unit composed of two highly interconnected chimeric modules--the miR34/SNAIL and the miR200/ZEB mutual-inhibition feedback circuits--regulates the coexistence of and transitions between the different phenotypes. Here, we present a new tractable theoretical framework to model and decode the underlying principles governing the operation of the regulatory unit. Our approach connects the knowledge about intracellular pathways with observations of cellular behavior and advances toward understanding the logic of cancer decision-making. We found that the miR34/SNAIL module acts as an integrator while the miR200/ZEB module acts as a three-way switch. Consequently, the combined unit can give rise to three phenotypes (stable states): (i) a high miR200 and low ZEB, or (1, 0) state; (ii) a low miR200 and high ZEB, or (0, 1) state; and (iii) a medium miR200 and medium ZEB, or (½, ½) state. We associate these states with the epithelial, mesenchymal, and hybrid phenotypes, respectively. We reflect on the consistency between our theoretical predictions and recent observations in several types of carcinomas and suggest new testable predictions. See all articles in this Cancer Research section,

PEGylated-thymoquinone-nanoparticle mediated retardation of breast cancer cell migration by deregulation of cytoskeletal actin polymerization through miR-34a

Thymoquinone (TQ), a major active constituent of black seeds of Nigella sativa, has potential medical applications including spectrum of therapeutic properties against different cancers. However, little is known about their effect on breast cancer cell migration, which is the cause of over 90% of deaths worldwide. Herein, we have synthesized TQ-encapsulated nanoparticles using biodegradable, hydrophilic polymers like polyvinylpyrrolidone (PVP) and polyethyleneglycol (PEG) to overcome TQ's poor aqueous solubility, thermal and light sensitivity as well as consequently, minimal systemic bioavailability which can greatly improve the cancer treatment efficiency. Sizes of synthesized TQ-Nps were found to be below 50 nm and they were mostly spherical in shape with smooth surface texture. Estimation of the zeta potential also revealed that all the three TQ-Nps were negatively charged which also facilitated their cellular uptake. In the present investigation, we provide direct evidence that TQ-Nps showed more efficiency in killing cancer cells as well as proved to be less toxic to normal cells at a significantly lower dose than TQ. Interestingly, evaluation of the anti-migratory effect of the TQ-Nps, revealed that PEG4000-TQ-Nps showed much potent anti-migratory properties than the other types. Further studies indicated that PEG4000-TQ-Nps could significantly increase the expression of miR-34a through p53. Moreover, NPs mediated miR-34a up-regulation directly down-regulated Rac1 expression followed by actin depolymerisation thereby disrupting the actin cytoskeleton which leads to significant reduction in the lamellipodia and filopodia formation on cell surfaces thus retarding cell migration. Considering the biodegradability, non-toxicity and effectivity of PEG4000-TQ-Nps against cancer cell migration, TQ-Nps may provide new insights into specific therapeutic approach for cancer treatment.

Cytokine networking of chondrocyte dedifferentiation in vitro and its implications for cell-based cartilage therapy

Autologous chondrocyte implantation (ACI) is a golden treatment for large defects of the knee joint without osteoarthritis or other complications. Despite notable progresses, generation of a stable chondrocyte phenotype using progenitor cells remains a main obstacle for chondrocyte-based cartilage treatment. Monolayer chondrocyte expansion in vitro is accompanied by chondrocyte dedifferentiation, which produces a non-specific mechanically inferior extracellular matrix (ECM) unsuitable for ACI. In-depth understanding of the molecular events during chondrocyte dedifferentiation is required to maintain the capacity of in vitro expanded chondrocytes to produce hyaline cartilage-specific ECM. This review discusses key cytokines and signaling pathways involved in chondrocyte dedifferentiation from the standpoint of catabolism and anabolism. Some potential therapeutic strategies are also presented to counteract chondrocyte dedifferentiation for cell-based cartilage therapy.

MicroRNAs are potential prognostic and therapeutic targets in diabetic osteoarthritis

Osteoarthritis is an aging-related degenerative disease that severely influences the elders' life quality. However, there have been few clinical approaches available until now. Currently, more knowledge of the pathology of osteoarthritis has been illustrated. Especially, diabetes can be the only predictor of osteoarthritis. Due to its outstanding characteristics, MicroRNA has been considered as an efficient target in treating diseases. In this review, we will discuss a new insight focusing on the roles of microRNA in the progression of osteoarthritis-induced by diabetes, especially type II diabetes mellitus.

Ser/Thr-phosphoprotein phosphatases in chondrogenesis: neglected components of a two-player game

Protein phosphorylation plays a determining role in the regulation of chondrogenesis in vitro. While signalling pathways governed by protein kinases including PKA, PKC, and mitogen-activated protein kinases (MAPK) have been mapped in great details, published data relating to the specific role of phosphoprotein phosphatases (PPs) in differentiating chondroprogenitor cells or in mature chondrocytes is relatively sparse. This review discusses the known functions of Ser/Thr-specific PPs in the molecular signalling pathways of chondrogenesis. PPs are clearly equally important as protein kinases to counterbalance the effect of reversible protein phosphorylation. Of the main Ser/Thr PPs, some of the functions of PP1, PP2A and PP2B have been characterised in the context of chondrogenesis. While PP1 and PP2A appear to negatively regulate chondrogenic differentiation and maintenance of chondrocyte phenotype, calcineurin is an important stimulatory mediator during chondrogenesis but becomes inhibitory in mature chondrocytes. Furthermore, PPs are implicated to be mediators during the pathogenesis of osteoarthritis that makes them potential therapeutic targets to be exploited in the close future. Among the many yet unexplored targets of PPs, modulation of plasma membrane ion channel function and participation in mechanotransduction pathways are emerging novel aspects of signalling during chondrogenesis that should be further elucidated. Besides the regulation of cellular ion homeostasis, other potentially significant novel roles for PPs during the regulation of in vitro chondrogenesis are discussed.

MicroRNAs as regulators of bone homeostasis and bone metastasis

MicroRNAs (miRNAs) are short, endogenous RNAs that have essential roles in regulating gene expression through the disruption of target genes. The miRNA-induced suppression can occur through Argonaute-mediated cleavage of target mRNAs or by translational inhibition. System-wide studies have underscored the integral role that miRNAs play in regulating the expression of essential genes within bone marrow stromal cells. The miRNA expression has been shown to enhance or inhibit cell differentiation and activity, and elucidating miRNA targets within bone marrow cells has revealed novel regulations during normal bone development. Importantly, multiple studies have shown that miRNA misexpression mediates the progression of bone-related pathologies, including osteopetrosis and osteoporosis, as well as the development and progression of osteosarcoma. Furthermore, recent studies have detailed the capacity for miRNAs to influence bone metastasis from a number of primary carcinomas. Taken together, these findings reveal the significant clinical potential for miRNAs to regulate bone homeostasis, as well as to mediate bone-related pathologies.

MicroRNA 340 is involved in UVB-induced dendrite formation through the regulation of RhoA expression in melanocytes

The influence of UV irradiation on pigmentation is well established, but the molecular and cellular mechanisms controlling dendrite formation remain incompletely understood. MicroRNAs (miRNAs) are a class of small RNAs that participate in various cellular processes by suppressing the expression of target mRNAs. In this study, we investigated the expression of miRNAs in response to UVB irradiation using a microarray screen and then identified potential mRNA targets for differentially expressed miRNAs among the genes governing dendrite formation. We subsequently determined the ability of miRNA 340 (miR-340) to suppress the expression of RhoA, which is a predicted miR-340 target gene that regulates dendrite formation. The overexpression of miR-340 promoted dendrite formation and melanosome transport, and the downregulation of miR-340 inhibited UVB-induced dendrite formation and melanosome transport. Moreover, a luciferase reporter assay demonstrated direct targeting of RhoA by miR-340 in the immortalized human melanocyte cell line Pig1. In conclusion, this study has established an miRNA associated with UVB irradiation. The significant downregulation of RhoA protein and mRNA expression after UVB irradiation and the modulation of miR-340 expression suggest a key role for miR-340 in regulating UVB-induced dendrite formation and melanosome transport.

MicroRNA-127-5p regulates matrix metalloproteinase 13 expression and interleukin-1β-induced catabolic effects in human chondrocytes

OBJECTIVE

MicroRNAs (miRNAs), small noncoding RNA molecules, are involved in the pathogenesis of various diseases such as cancer and arthritis. The aim of this study was to determine whether miR-127-5p regulates interleukin-1β (IL-1β)-induced expression of matrix metalloproteinase 13 (MMP-13) and other catabolic factors in human chondrocytes.

METHODS

Expression of miR-127-5p and MMP-13 by normal and osteoarthritic (OA) human cartilage was determined using real-time polymerase chain reaction. The effect of miR-127-5p on MMP-13 expression was evaluated using transient transfection of human chondrocytes or chondrogenic SW-1353 cells with miR-127-5p or its antisense inhibitor (anti-miR-127-5p). MMP-13 protein production was quantified by enzyme-linked immunosorbent assay, and the involvement of miR-127-5p in IL-1β-mediated catabolic effects was examined by immunoblotting. MicroRNA-127-5p binding with the putative site in the 3'-untranslated region (3'-UTR) of MMP-13 messenger RNA (mRNA) was validated by luciferase reporter assay.

RESULTS

There was a significant reduction in miR-127-5p expression in OA cartilage compared with normal cartilage. Up-regulation of MMP-13 expression by IL-1β was correlated with down-regulation of miR-127-5p expression in human chondrocytes. MicroRNA-127-5p suppressed IL-1β-induced MMP-13 production as well as the activity of a reporter construct containing the 3'-UTR of human MMP-13 mRNA. In addition, mutation of the miR-127-5p binding site in the 3'-UTR of MMP-13 mRNA abolished miR-127-5p-mediated repression of reporter activity. Conversely, treatment with anti-miR-127-5p remarkably increased reporter activity and MMP-13 production. Interestingly, the IL-1β-induced activation of JNK, p38, and NF-κB and expression of MMP-1 and cyclooxygenase 2 were significantly inhibited by miR-127-5p.

CONCLUSION

MicroRNA-127-5p is an important regulator of MMP-13 in human chondrocytes and may contribute to the development of OA.

Regulation of chondrogenesis by protein kinase C: Emerging new roles in calcium signalling

During chondrogenesis, complex intracellular signalling pathways regulate an intricate series of events including condensation of chondroprogenitor cells and nodule formation followed by chondrogenic differentiation. Reversible phosphorylation of key target proteins is of particular importance during this process. Among protein kinases known to be involved in these pathways, protein kinase C (PKC) subtypes play pivotal roles. However, the precise function of PKC isoenzymes during chondrogenesis and in mature articular chondrocytes is still largely unclear. In this review, we provide a historical overview of how the concept of PKC-mediated chondrogenesis has evolved, starting from the first discoveries of PKC isoform expression and activity. Signalling components upstream and downstream of PKC, leading to the stimulation of chondrogenic differentiation, are also discussed. Although it is evident that we are only at the beginning to understand what roles are assigned to PKC subtypes during chondrogenesis and how they are regulated, there are many yet unexplored aspects in this area. There is evidence that calcium signalling is a central regulator in differentiating chondroprogenitors; still, clear links between intracellular calcium signalling and prototypical calcium-dependent PKC subtypes such as PKCalpha have not been established. Exploiting putative connections and shedding more light on how exactly PKC signalling pathways influence cartilage formation should open new perspectives for a better understanding of healthy as well as pathological differentiation processes of chondrocytes, and may also lead to the development of novel therapeutic approaches.

The microRNA networks of TGFβ signaling in cancer

In metazoans, the transforming growth factor β (TGFβ) signaling regulates a host of activities ranging from embryonic development to tissue homeostasis. The normal as well as tumor cells respond to this cytokine signaling pathway in a highly context-dependent manner. It acts as a potent tumor suppressor initially by inducing cell cycle arrest and apoptosis. But advanced tumors often misuse TGFβ signaling for tumor progression by selectively disabling the tumor suppressor arm and using other properties of TGFβ signaling such as induction of angiogenesis, epithelial to mesenchymal transition, and metastases. This dual role of TGFβ in cancer remained a mystery until recently. But recent advances in the field of microRNA provided a deeper understanding about this dual nature of TGFβ signaling in cancers. In the present review, we present an account of the role of microRNAs in deregulating TGFβ signaling and modulating cancer cell behavior during tumor initiation and cancer progression. This review also includes a discussion on the recent advances in the deregulation of TGFβ signaling in carcinogenesis.

Roles of microRNAs in prenatal chondrogenesis, postnatal chondrogenesis and cartilage-related diseases

Cartilage has limited repair and regeneration capacity, thus damage of cartilage often results in its dysfunction and even chronic diseases like osteoarthritis (OA). Chondrogenesis induced by tissue-engineering methods is essential to treating cartilage-related diseases. MicroRNAs (miRNAs) are a class of small non-coding single-stranded RNAs which exert their biological effects by binding to the target messenger RNAs (mRNAs), resulting in decay or translation suppression of target mRNAs. There are emerging evidence indicating that miRNAs may play important roles in regulating both prenatal and postnatal chondrogenesis. During embryonic skeletal development, prenatal chondrogenesis is thought to be a precondition for formation of cartilage in developing limbs. Plenty of studies on different types of stem cells have undoubtedly proven their capacity of differentiating into chondrocytes. MiRNAs are found to comprehensively modulate these processes by establishing an interaction network with target genes, transcription factors and cytokines et al. In addition, translational application of miRNA technology has also been explored. In this review, we focus on the up-dated progress on regulatory mechanisms of miRNAs in prenatal and postnatal chondrogenesis. In addition, several miRNA target genes and roles of miRNAs in cartilage-related diseases are also discussed. This will contribute to studies of chondrogenesis mechanisms and development of new treating methods.

Repression of choroidal neovascularization through actin cytoskeleton pathways by microRNA-24

Actin cytoskeleton is critical for cell motility and division, both of which are important for angiogenesis. MicroRNAs (miRNA/miR) are emerging as pivotal modulators of vascular development and disease. How miRNAs regulate actin cytoskeleton dynamics in endothelial cells (EC) and neovascularization is still unclear. Here, we report that miR-24 regulates actin dynamics in ECs through targeting multiple members downstream of Rho signaling, including Pak4, Limk2, and Diaph1 proteins. Overexpression of miR-24 in ECs blocks stress fiber and lamellipodia formation, represses EC migration, proliferation, and tube formation in vitro, as well as angiogenesis in an ex vivo aortic ring assay. Moreover, subretinal delivery of miR-24 mimics represses laser-induced choroidal neovascularization (CNV) in vivo. Mechanistically, knockdown of miR-24 target protein LIMK2 or PAK4 inhibits stress fiber formation and tube formation in vitro, mimicking miR-24 overexpression phenotype in angiogenesis, while overexpression of LIMK2 and PAK4 by adenoviruses partially rescued the tube formation defects in miR-24 overexpressing ECs. Taken together, these findings suggest that miR-24 represses angiogenesis by simultaneously regulating multiple components in the actin cytoskeleton pathways. Manipulation of actin cytoskeleton pathways by miR-24 may represent an attractive therapeutic solution for the treatment of wet age-related macular degeneration (AMD) and other vascular diseases.

MicroRNA-9 regulates survival of chondroblasts and cartilage integrity by targeting protogenin

Background

Studies have shown the roles of miR-9 and its validated target, protogenin (PRTG) in the differentiation of chondroblasts to chondrocyte and in the pathogenesis of osteoarthritis (OA). We hypothesized that miR-9 plays a distinct role in endochondral ossification and OA pathogenesis and the present study was undertaken to identify this role. In the studies, chondroblasts were isolated from limb bud of chick and mouse embryos and articular chondrocytes were isolated from rabbit and human cartilage. Osteoarthritic chondrocytes were isolated from cartilage from patients undergoing total knee replacement. Using these cells, we analyzed the changes in the expression of genes and proteins, tested the expression level of miR-9, and applied a target validation system. We also performed functional study of miR-9 and PRTG.

Results

With the progression of chondrogenesis, decreased miR-9 level was observed at the time of numerous apoptotic cell deaths. And chondrocytes isolated from normal human articular cartilage expressed miR-9, and this expression was significantly reduced in OA chondrocytes, especially decreased its expression in parallel with the degree of cartilage degradation. Over-expression of PRTG induced the activation of caspase-3 signaling and increased apoptosis. However, the co-treatment with the miR-9 precursor or PRTG-specific siRNA blocked this apoptotic signaling.

Conclusion

This study shows that PRTG is regulated by miR-9, plays an inhibitory action on survival of chondroblasts and articular chondrocytes during chondrogenesis and OA pathogenesis.

Molecular mechanisms of asymmetric division in oocytes

In contrast to symmetric division in mitosis, mammalian oocyte maturation is characterized by asymmetric cell division that produces a large egg and a small polar body. The asymmetry results from oocyte polarization, which includes spindle positioning, migration, and cortical reorganization, and this process is critical for fertilization and the retention of maternal components for early embryo development. Although actin dynamics are involved in this process, the molecular mechanism underlying this remained unclear until the use of confocal microscopy and live cell imaging became widespread in recent years. Information obtained through a PubMed database search of all articles published in English between 2000 and 2012 that included the phrases "oocyte, actin, spindle migration," "oocyte, actin, polar body," or "oocyte, actin, asymmetric division" was reviewed. The actin nucleation factor actin-related protein 2/3 complex and its nucleation-promoting factors, formins and Spire, and regulators such as small GTPases, partitioning-defective/protein kinase C, Fyn, microRNAs, cis-Golgi apparatus components, myosin/myosin light-chain kinase, spindle stability regulators, and spindle assembly checkpoint regulators, play critical roles in asymmetric cell division in oocytes. This review summarizes recent findings on these actin-related regulators in mammalian oocyte asymmetric division and outlines a complete signaling pathway.

MicroRNAs in farm animals

MicroRNAs (miRNAs) are a class of ~22 nucleotide-long small noncoding RNAs that target mRNAs for translational repression or degradation. miRNAs target mRNAs by base-pairing with the 3'-untranslated regions (3'-UTRs) of mRNAs. miRNAs are present in various species, from animals to plants. In this review, we summarize the identification, expression, and function of miRNAs in four important farm animal species: cattle, chicken, pig and sheep. In each of these species, hundreds of miRNAs have been identified through homology search, small RNA cloning and next generation sequencing. Real-time RT-PCR and microarray experiments reveal that many miRNAs are expressed in a tissue-specific or spatiotemporal-specific manner in farm animals. Limited functional studies suggest that miRNAs have important roles in muscle development and hypertrophy, adipose tissue growth, oocyte maturation and early embryonic development in farm animals. Increasing evidence suggests that single-nucleotide polymorphisms in miRNA target sites or miRNA gene promoters may contribute to variation in production or health traits in farm animals.

miRNAs regulate expression and function of extracellular matrix molecules

MicroRNAs (miRNAs) are a family of small non-coding RNA molecules that are made up of 18-25 nucleotides that function in post-transcriptional gene regulation. The expression of miRNAs is highly conserved and essential in regulating many cellular processes including formation, maintenance and the remodelling of the extracellular matrix (ECM). In this review, we examine different ECM molecules and the miRNAs involved in regulating their abundance and how these changes influence cell phenotype. For example, miRNAs and their target messenger RNAs (mRNAs) are involved in cell adhesion, by regulating the synthesis and turnover of key ECM adhesion molecules and their receptors including cadherins, integrins and other non-integrin ECM receptors. Other miRNAs regulate the abundance of cytokines and growth factors which in turn stimulate cells to synthesize and secrete specialized ECMs. For example, miR-125a/b and miR-146a and their downstream target mRNAs influence the production of the epidermal growth factor family which has a significant impact on the nature of the ECM formed. miRNAs affect structural ECM proteins important in the assembly, composition and organization of the ECM. Proteins such as collagen, fibronectin, versican, and nephronectin are targeted by several miRNAs. miRNAs can also control the expression of proteins such as matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs), which are involved in ECM remodelling and are important for tissue development, cell motility and wound healing. It has become clear that many different miRNAs control the balance in ECM composition that determines normal tissue function and alterations in the expression of these miRNAs can lead to pathological consequences.