A novel fibroblast growth factor receptor 1 inhibitor protects against cartilage degradation in a murine model of osteoarthritis

Effects of circulating inflammatory proteins on spinal degenerative diseases: Evidence from genetic correlations and Mendelian randomization study

Background

Numerous investigations have suggested links between circulating inflammatory proteins (CIPs) and spinal degenerative diseases (SDDs), but causality has not been proven. This study used Mendelian randomization (MR) to investigate the causal associations between 91 CIPs and cervical spondylosis (CS), prolapsed disc/slipped disc (PD/SD), spinal canal stenosis (SCS), and spondylolisthesis/spondylolysis.

Methods

Genetic variants data for CIPs and SDDs were obtained from the genome-wide association studies (GWAS) database. We used inverse variance weighted (IVW) as the primary method, analyzing the validity and robustness of the results through pleiotropy and heterogeneity tests and performing reverse MR analysis to test for reverse causality.

Results

The IVW results with Bonferroni correction indicated that beta-nerve growth factor (β-NGF), C-X-C motif chemokine 6 (CXCL6), and interleukin-6 (IL-6) can increase the risk of CS. Fibroblast growth factor 19 (FGF19), sulfotransferase 1A1 (SULT1A1), and tumor necrosis factor-beta (TNF-β) can increase PD/SD risk, whereas urokinase-type plasminogen activator (u-PA) can decrease the risk of PD/SD. FGF19 and TNF can increase SCS risk. STAM binding protein (STAMBP) and T-cell surface glycoprotein CD6 isoform (CD6 isoform) can increase the risk of spondylolisthesis/spondylolysis, whereas monocyte chemoattractant protein 2 (MCP2) and latency-associated peptide transforming growth factor beta 1 (LAP-TGF-β1) can decrease spondylolisthesis/spondylolysis risk.

Conclusions

MR analysis indicated the causal associations between multiple genetically predicted CIPs and the risk of four SDDs (CS, PD/SD, SCS, and spondylolisthesis/spondylolysis). This study provides reliable genetic evidence for in-depth exploration of the involvement of CIPs in the pathogenic mechanism of SDDs and provides novel potential targets for SDDs.

Sympathetic Neurotransmitter, VIP, Delays Intervertebral Disc Degeneration via FGF18/FGFR2-Mediated Activation of Akt Signaling Pathway

Neuromodulation-related intervertebral disc degeneration (IVDD) is a novel IVDD pattern and are proposed recently. However, the mechanistic basis of neuromodulation and intervertebral disc (IVD) homeostasis remains unclear. Here, this study aimed to investigate the expression of postganglionic sympathetic nerve fiber-derived vasoactive intestinal peptide (VIP) system in human IVD tissue, and to assess the role of VIP-related neuromodulation in IVDD. Patient samples and in vitro cell experiments showed that the expression of receptors for VIP is negatively correlated with the severity of IVDD, and the administration of exogenous VIP can ameliorate interleukin 1β-induced nucleus pulposus (NP) cell apoptosis and inflammation. Further mRNA-seq analysis revealed that fibroblast growth factor 18- (FGF18)-mediated activation of V-akt murine thymoma viral oncogene homolog signaling pathway is involved in the protective effects of VIP on inflammation-induced NP cell degeneration. Further analysis identified VIP via its receptor vasoactive intestinal peptide receptor 2 can directly result in decreased expression of miR-15a-5p, which targeted FGF18. Finally, in vivo mice lumbar IVDD model confirmed that focally exogenous administration of VIP can effectively ameliorated the progression of IVDD, as shown by the radiological and histological analysis. In conclusion, these results indicated that sympathetic neurotransmitter, VIP, delayed IVDD via FGF18/FGFR2-mediated activation of V-akt murine thymoma viral oncogene homolog signaling pathway, which will broaden the horizon concerning how the neuromodulation correlates with IVDD and shed new light on novel therapeutical alternatives to IVDD.

New insights in osteoarthritis diagnosis and treatment: Nano-strategies for an improved disease management

Osteoarthritis (OA) is a common chronic joint pathology that has become a predominant cause of disability worldwide. Even though the origin and evolution of OA rely on different factors that are not yet elucidated nor understood, the development of novel strategies to treat OA has emerged in the last years. Cartilage degradation is the main hallmark of the pathology though alterations in bone and synovial inflammation, among other comorbidities, are also involved during OA progression. From a molecular point of view, a vast amount of signaling pathways are implicated in the progression of the disease, opening up a wide plethora of targets to attenuate or even halt OA. The main purpose of this review is to shed light on the recent strategies published based on nanotechnology for the early diagnosis of the disease as well as the most promising nano-enabling therapeutic approaches validated in preclinical models. To address the clinical issue, the key pathways involved in OA initiation and progression are described as the main potential targets for OA prevention and early treatment. Furthermore, an overview of current therapeutic strategies is depicted. Finally, to solve the drawbacks of current treatments, nanobiomedicine has shown demonstrated benefits when using drug delivery systems compared with the administration of the equivalent doses of the free drugs and the potential of disease-modifying OA drugs when using nanosystems. We anticipate that the development of smart and specific bioresponsive and biocompatible nanosystems will provide a solid and promising basis for effective OA early diagnosis and treatment. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Chondrocyte Hypertrophy in Osteoarthritis: Mechanistic Studies and Models for the Identification of New Therapeutic Strategies

Articular cartilage shows limited self-healing ability owing to its low cellularity and avascularity. Untreated cartilage defects display an increased propensity to degenerate, leading to osteoarthritis (OA). During OA progression, articular chondrocytes are subjected to significant alterations in gene expression and phenotype, including a shift towards a hypertrophic-like state (with the expression of collagen type X, matrix metalloproteinases-13, and alkaline phosphatase) analogous to what eventuates during endochondral ossification. Present OA management strategies focus, however, exclusively on cartilage inflammation and degradation. A better understanding of the hypertrophic chondrocyte phenotype in OA might give new insights into its pathogenesis, suggesting potential disease-modifying therapeutic approaches. Recent developments in the field of cellular/molecular biology and tissue engineering proceeded in the direction of contrasting the onset of this hypertrophic phenotype, but knowledge gaps in the cause-effect of these processes are still present. In this review we will highlight the possible advantages and drawbacks of using this approach as a therapeutic strategy while focusing on the experimental models necessary for a better understanding of the phenomenon. Specifically, we will discuss in brief the cellular signaling pathways associated with the onset of a hypertrophic phenotype in chondrocytes during the progression of OA and will analyze in depth the advantages and disadvantages of various models that have been used to mimic it. Afterwards, we will present the strategies developed and proposed to impede chondrocyte hypertrophy and cartilage matrix mineralization/calcification. Finally, we will examine the future perspectives of OA therapeutic strategies.

RORβ modulates a gene program that is protective against articular cartilage damage

Osteoarthritis (OA) is the most prevalent chronic joint disease which increases in frequency with age eventually impacting most people over the age of 65. OA is the leading cause of disability and impaired mobility, yet the pathogenesis of OA remains unclear. Treatments have focused mainly on pain relief and reducing joint swelling. Currently there are no effective treatments to slow the progression of the disease and to prevent irreversible loss of cartilage. Here we demonstrate that stable expression of RORβ in cultured cells results in alteration of a gene program that is supportive of chondrogenesis and is protective against development of OA. Specifically, we determined that RORβ alters the ratio of expression of the FGF receptors FGFR1 (associated with cartilage destruction) and FGFR3 (associated with cartilage protection). Additionally, ERK1/2-MAPK signaling was suppressed and AKT signaling was enhanced. These results suggest a critical role for RORβ in chondrogenesis and suggest that identification of mechanisms that control the expression of RORβ in chondrocytes could lead to the development of disease modifying therapies for the treatment of OA.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

The Extracellular Matrix of Articular Cartilage Controls the Bioavailability of Pericellular Matrix-Bound Growth Factors to Drive Tissue Homeostasis and Repair

The extracellular matrix (ECM) has long been regarded as a packing material; supporting cells within the tissue and providing tensile strength and protection from mechanical stress. There is little surprise when one considers the dynamic nature of many of the individual proteins that contribute to the ECM, that we are beginning to appreciate a more nuanced role for the ECM in tissue homeostasis and disease. Articular cartilage is adapted to be able to perceive and respond to mechanical load. Indeed, physiological loads are essential to maintain cartilage thickness in a healthy joint and excessive mechanical stress is associated with the breakdown of the matrix that is seen in osteoarthritis (OA). Although the trigger by which increased mechanical stress drives catabolic pathways remains unknown, one mechanism by which cartilage responds to increased compressive load is by the release of growth factors that are sequestered in the pericellular matrix. These are heparan sulfate-bound growth factors that appear to be largely chondroprotective and displaced by an aggrecan-dependent sodium flux. Emerging evidence suggests that the released growth factors act in a coordinated fashion to drive cartilage repair. Thus, we are beginning to appreciate that the ECM is the key mechano-sensor and mechano-effector in cartilage, responsible for directing subsequent cellular events of relevance to joint health and disease.

Roles of the fibroblast growth factor signal transduction system in tissue injury repair

Following injury, tissue autonomously initiates a complex repair process, resulting in either partial recovery or regeneration of tissue architecture and function in most organisms. Both the repair and regeneration processes are highly coordinated by a hierarchy of interplay among signal transduction pathways initiated by different growth factors, cytokines and other signaling molecules under normal conditions. However, under chronic traumatic or pathological conditions, the reparative or regenerative process of most tissues in different organs can lose control to different extents, leading to random, incomplete or even flawed cell and tissue reconstitution and thus often partial restoration of the original structure and function, accompanied by the development of fibrosis, scarring or even pathogenesis that could cause organ failure and death of the organism. Ample evidence suggests that the various combinatorial fibroblast growth factor (FGF) and receptor signal transduction systems play prominent roles in injury repair and the remodeling of adult tissues in addition to embryonic development and regulation of metabolic homeostasis. In this review, we attempt to provide a brief update on our current understanding of the roles, the underlying mechanisms and clinical application of FGFs in tissue injury repair.

Blockade of Fgfr1 with PD166866 Protects Cartilage from the Catabolic Effects Induced by Interleukin-1β: A Genome-Wide Expression Profiles Analysis

OBJECTIVE

Previously we showed that genetic deletion of Fgfr1 in chondrocytes protected mice from progression of osteoarthritis (OA). The aim of this study is to evaluate the effect of PD166866, a potent selective inhibitor of Fgfr1, on cartilage degeneration induced by interleukin-1β (IL-1β) and to clarify underlying global gene expression pattern.

DESIGN

Cartilage explants and primary rat chondrocytes were stimulated with IL-1β to establish an inflammatory OA in vitro model. The effects of PD166866 were determined by measuring the release of glycosaminoglycans (GAG) in cartilage explants and primary rat chondrocytes, and the underlying molecular mechanism was analyzed by microarray and RT-PCR analysis in primary chondrocytes.

RESULTS

In cartilage explants, PD166866 significantly counteracts IL-β stimulated GAG release. In addition, PD166866 impede IL-1β-stimulated nuclear translocation of p65 in rat chondrocytes. Based on microarray analysis, a total of 67 and 132 genes with more than 1.5-fold changes were identified in IL-1β-treated versus control and PD166866 cotreatment versus IL-1β treatment alone, respectively. Only 19 thereof were coregulated by IL-1β and PD166866 simultaneously. GO and KEGG pathway analysis showed that some pathways, including "cytokine-cytokine receptor interaction," "chemokine signaling pathway," and "complement and coagulation cascades," as well as some key genes like chemokines, complement, and matrix metalloproteinases may relevant for therapeutic application of Fgfr1 blockade in IL-1β-stimulated chondrocytes.

CONCLUSION

Our results clearly demonstrated that blockade of Fgfr1 with PD166866 could effectively suppress the catabolic effects induced by IL-1β, and elucidated whole genomic targets of Fgfr1 inhibition responsible for the therapeutic effects of Fgfr1 blockade against inflammatory OA.

Tyrosine kinases regulate chondrocyte hypertrophy: promising drug targets for Osteoarthritis

Osteoarthritis (OA) is a major health problem worldwide that affects the joints and causes severe disability. It is characterized by pain and low-grade inflammation. However, the exact pathogenesis remains unknown and the therapeutic options are limited. In OA articular chondrocytes undergo a phenotypic transition becoming hypertrophic, which leads to cartilage damage, aggravating the disease. Therefore, a therapeutic agent inhibiting hypertrophy would be a promising disease-modifying drug. The therapeutic use of tyrosine kinase inhibitors has been mainly focused on oncology, but the Food and Drug Administration (FDA) approval of the Janus kinase inhibitor Tofacitinib in Rheumatoid Arthritis has broadened the applicability of these compounds to other diseases. Interestingly, tyrosine kinases have been associated with chondrocyte hypertrophy. In this review, we discuss the experimental evidence that implicates specific tyrosine kinases in signaling pathways promoting chondrocyte hypertrophy, highlighting their potential as therapeutic targets for OA.

Pathological mechanism of chondrocytes and the surrounding environment during osteoarthritis of temporomandibular joint

Temporomandibular joint (TMJ) osteoarthritis is a common chronic degenerative disease of the TMJ. In order to explore its aetiology and pathological mechanism, many animal models and cell models have been constructed to simulate the pathological process of TMJ osteoarthritis. The main pathological features of TMJ osteoarthritis include chondrocyte death, extracellular matrix (ECM) degradation and subchondral bone remodelling. Chondrocyte apoptosis accelerates the destruction of cartilage. However, autophagy has a protective effect on condylar chondrocytes. Degradation of ECM not only changes the properties of cartilage but also affects the phenotype of chondrocytes. The loss of subchondral bone in the early stages of TMJ osteoarthritis plays an aetiological role in the onset of osteoarthritis. In recent years, increasing evidence has suggested that chondrocyte hypertrophy and endochondral angiogenesis promote TMJ osteoarthritis. Hypertrophic chondrocytes secrete many factors that promote cartilage degeneration. These chondrocytes can further differentiate into osteoblasts and osteocytes and accelerate cartilage ossification. Intrachondral angiogenesis and neoneurogenesis are considered to be important triggers of arthralgia in TMJ osteoarthritis. Many molecular signalling pathways in endochondral osteogenesis are responsible for TMJ osteoarthritis. These latest discoveries in TMJ osteoarthritis have further enhanced the understanding of this disease and contributed to the development of molecular therapies. This paper summarizes recent cognition on the pathogenesis of TMJ osteoarthritis, focusing on the role of chondrocyte hypertrophy degeneration and cartilage angiogenesis.

Of mice and men: converging on a common molecular understanding of osteoarthritis

Despite an increasing burden of osteoarthritis in developed societies, target discovery has been slow and there are currently no approved disease-modifying osteoarthritis drugs. This lack of progress is due in part to a series of misconceptions over the years: that osteoarthritis is an inevitable consequence of ageing, that damaged articular cartilage cannot heal itself, and that osteoarthritis is driven by synovial inflammation similar to that seen in rheumatoid arthritis. Molecular interrogation of disease through ex-vivo tissue analysis, in-vitro studies, and preclinical models have radically reshaped the knowledge landscape. Inflammation in osteoarthritis appears to be distinct from that seen in rheumatoid arthritis. Recent randomised controlled trials, using treatments repurposed from rheumatoid arthritis, have largely been unsuccessful. Genome-wide studies point to defects in repair pathways, which accords well with recent promise using growth factor therapies or Wnt pathway antagonism. Nerve growth factor has emerged as a robust target in osteoarthritis pain in phase 2-3 trials. These studies, both positive and negative, align well with those in preclinical surgical models of osteoarthritis, indicating that pathogenic mechanisms identified in mice can lead researchers to valid human targets. Several novel candidate pathways are emerging from preclinical studies that offer hope of future translational impact. Enhancing trust between industry, basic, and clinical scientists will optimise our collective chance of success.

FGF/FGFR signaling in health and disease

Growing evidences suggest that the fibroblast growth factor/FGF receptor (FGF/FGFR) signaling has crucial roles in a multitude of processes during embryonic development and adult homeostasis by regulating cellular lineage commitment, differentiation, proliferation, and apoptosis of various types of cells. In this review, we provide a comprehensive overview of the current understanding of FGF signaling and its roles in organ development, injury repair, and the pathophysiology of spectrum of diseases, which is a consequence of FGF signaling dysregulation, including cancers and chronic kidney disease (CKD). In this context, the agonists and antagonists for FGF-FGFRs might have therapeutic benefits in multiple systems.

Fibroblast growth factor signalling in osteoarthritis and cartilage repair

Regulated fibroblast growth factor (FGF) signalling is a prerequisite for the correct development and homeostasis of articular cartilage, as evidenced by the fact that aberrant FGF signalling contributes to the maldevelopment of joints and to the onset and progression of osteoarthritis. Of the four FGF receptors (FGFRs 1-4), FGFR1 and FGFR3 are strongly implicated in osteoarthritis, and FGFR1 antagonists, as well as agonists of FGFR3, have shown therapeutic efficacy in mouse models of spontaneous and surgically induced osteoarthritis. FGF18, a high affinity ligand for FGFR3, is the only FGF-based drug currently in clinical trials for osteoarthritis. This Review covers the latest advances in our understanding of the molecular mechanisms that regulate FGF signalling during normal joint development and in the pathogenesis of osteoarthritis. Strategies for FGF signalling-based treatment of osteoarthritis and for cartilage repair in animal models and clinical trials are also introduced. An improved understanding of FGF signalling from a structural biology perspective, and of its roles in skeletal development and diseases, could unlock new avenues for discovery of modulators of FGF signalling that can slow or stop the progression of osteoarthritis.

Genome-wide analysis of DNA methylation profile identifies differentially methylated loci associated with human intervertebral disc degeneration

BACKGROUND

Environmental and endogenous factors under genetic predisposition are considered to initiate the human intervertebral disc (IVD) degeneration. DNA methylation is an essential mechanism to ensure cell-specific gene expression for normal development and tissue stability. Aberrant epigenetic alterations play a pivotal role in several diseases, including osteoarthritis. However, epigenetic alternations, including DNA methylation, in IVD degeneration have not been evaluated. The purpose of this study was to comprehensively compare the genome-wide DNA methylation profiles of human IVD tissues, specifically nucleus pulpous (NP) tissues, with early and advanced stages of disc degeneration.

METHODS

Human NP tissues were used in this study. The samples were divided into two groups: early stage degeneration (n = 8, Pfirrmann's MRI grade: I-III) and advanced stage degeneration (n = 8, grade: IV). Genomic DNA was processed for genome-wide DNA methylation profiling using the Infinium MethylationEPIC BeadChip array. Extraction of raw methylation data, clustering and scatter plot of each group values of each sample were performed using a methylation module in GenomeStudio software. The identification of differentially methylated loci (DMLs) and the Gene Ontology (GO) analysis were performed using R software with the ChAMP package.

RESULTS

Unsupervised hierarchical clustering revealed that early and advanced stage degenerated IVD samples segregated into two main clusters by their DNA methylome. A total of 220 DMLs were identified between early and advanced disc degeneration stages. Among these, four loci were hypomethylated and 216 loci were hypermethylated in the advanced disc degeneration stage. The GO enrichment analysis of genes containing DMLs identified two significant GO terms for biological processes, hemophilic cell adhesion and cell-cell adhesion.

CONCLUSIONS

We conducted a genome-wide DNA methylation profile comparative study and observed significant differences in DNA methylation profiles between early and advanced stages of human IVD degeneration. These results implicate DNA methylation in the process of human IVD degeneration.

A novel FGFR1-binding peptide attenuates the degeneration of articular cartilage in adult mice

OBJECTIVE

We previously reported that genetic ablation of (Fibroblast Growth Factors Receptors) FGFR1 in knee cartilage attenuates the degeneration of articular cartilage in adult mice, which suggests that FGFR1 is a potential targeting molecule for osteoarthritis (OA). Here, we identified R1-P1, an inhibitory peptide for FGFR1 and investigated its effect on the pathogenesis of OA in mice induced by destabilization of medial meniscus (DMM).

DESIGN

Binding ability between R1-P1 and FGFR1 protein was evaluated by enzyme-linked immuno sorbent assay (ELISA) and molecular docking. Alterations in cartilage were evaluated histologically. The expression levels of molecules associated with articular cartilage homeostasis and FGFR1 signaling were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR), Western blotting and immunohistochemistry (IHC). The chondrocyte apoptosis was detected by terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) assay.

RESULTS

R1-P1 had highly binding affinities to human FGFR1 protein, and efficiently inhibited extracellular signal-regulated kinase (ERK)1/2 pathway in mouse primary chondrocytes. In addition, R1-P1 attenuated the IL-1β induced significant loss of proteoglycan in full-thickness cartilage tissue from human femur head. Moreover, this peptide can significantly restore the IL-1β mediated loss of proteoglycan and type II collagen (Col II) and attenuate the expression of matrix metalloproteinase-13 (MMP13) in mouse primary chondrocytes. Finally, intra-articular injection of R1-P1 remarkably attenuated the loss of proteoglycan and the destruction of articular cartilage and decreased the expressions of extracellular matrix (ECM) degrading enzymes and apoptosis in articular chondrocytes of mice underwent DMM surgery.

CONCLUSIONS

R1-P1, a novel inhibitory peptide for FGFR1, attenuates the degeneration of articular cartilage in adult mice, which is a potential leading molecule for the treatment of OA.

Design, synthesis and biological evaluation of 4-bromo-N-(3,5-dimethoxyphenyl)benzamide derivatives as novel FGFR1 inhibitors for treatment of non-small cell lung cancer

A series of 4-bromo-N-(3,5-dimethoxyphenyl)benzamide derivatives were designed and synthesised as novel fibroblast growth factor receptor-1 (FGFR1) inhibitors. We found that one of the most promising compounds, C9, inhibited five non-small cell lung cancer (NSCLC) cell lines with FGFR1 amplification, including NCI-H520, NCI-H1581, NCI-H226, NCI-H460 and NCI-H1703. Moreover, the IC₅₀ values for the compound C9 were 1.36 ± 0.27 µM, 1.25 ± 0. 23 µM, 2.31 ± 0.41 µM, 2.14 ± 0.36 µM and 1.85 ± 0.32 µM, respectively. The compound C9 arrested the cell cycle at the G2 phase in NSCLC cell lines. The compound C9 also induced cellular apoptosis and inhibited the phosphorylation of FGFR1, PLCγ1 and ERK in a dose-dependent manner. In addition, molecular docking experiments showed that compound C9 binds to FGFR1 to form six hydrogen bonds. Taken together, our data suggested that the compound C9 represented a promising lead compound-targeting FGFR1.

JNK pathway in osteoarthritis: pathological and therapeutic aspects

CONTEXT

Osteoarthritis (OA) is a common chronic degenerative joint disease resulting in physical disability and reduced quality of life. Different biochemical signaling pathways are involved in the progression of OA, including the c-Jun NH2-terminal kinase (JNK) signal transduction pathway.

OBJECTIVE

In this study, we have reviewed the recent updates on the association of JNK pathway with OA.

METHODS

In this review, we have explored the databases like PubMed, Google Scholar, Medline, Scopus, etc., and collected the most relevant papers of JNK signaling pathway involved in the pathogenesis and therapeutics of OA Results: JNK has been shown by scientific studies to be activated (phosphorylated) in OA that can play a key role in the cartilage destruction. Activation of JNK causes the phosphorylation of c-Jun that causes decreased proteoglycan synthesis and enhanced production of matrix metalloproteinase 13 (MMP-13). Overproduction of MMP-13 by chondrocytes plays a central role in cartilage degeneration in OA. Thus, targeting JNK pathway might be a promising therapeutic application for the prevention and treatment of OA. A number of JNK-inhibitors have been used in vitro and in vivo studies; however, not yet been translated into human use.

CONCLUSIONS

This review study indicates that JNK pathway plays an important role in development and progression of OA, and targeting the JNK pathway might be a potential approach for the treatment of OA in future.

Loss of Fgfr1 in chondrocytes inhibits osteoarthritis by promoting autophagic activity in temporomandibular joint

Temporomandibular joint osteoarthritis (TMJ OA) is a common degenerative disease with few effective disease-modifying treatments in the clinic. Fibroblast growth factor (FGF) signaling is implicated in articular cartilage homeostasis, but the functional roles of FGFR1 in TMJ OA remain largely unknown. In this study, we report that deletion of Fgfr1 in TMJ chondrocytes delayed TMJ OA progression in the age-associated spontaneous OA model and the abnormal dental occlusion OA model. Immunohistochemical staining revealed that Fgfr1 deficiency decreased the expressions of MMP13 (matrix metalloproteinase-13), ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5), and COL10A1 but increased aggrecan expression level in two TMJ OA models. Furthermore, our data show that inactivation of FGFR1 signaling may promote autophagic activity in TMJ. FGFR1 inhibitor decreased the expressions of Mmp13, Adamts5, and Runx2 in IL-1β-stimulated condylar chondrocytes, whereas autophagy inhibitors abrogated the protective effects of the FGFR1 inhibitor. Thus, our study indicates inactivated FGFR1 signaling ameliorates TMJ OA progression partially by promoting autophagic activity. Manipulation of this signaling may be a potential therapeutic approach to modify TMJ OA.

Recent Insights into the Contribution of the Changing Hypertrophic Chondrocyte Phenotype in the Development and Progression of Osteoarthritis

Osteoarthritis (OA) is an extremely prevalent age-related condition. The economic and societal burden due to the cost of symptomatic treatment, inability to work, joint replacement, and rehabilitation is huge and increasing. Currently, there are no effective medical therapies that delay or reverse the pathological manifestations of OA. Current treatment options are, without exception, focused on slowing down progression of the disease to postpone total joint replacement surgery for as long as possible and keeping the associated pain and joint immobility manageable. Alterations in the articular cartilage chondrocyte phenotype might be fundamental in the pathological mechanisms of OA development. In many ways, the changing chondrocyte phenotype in osteoarthritic cartilage resembles the process of endochondral ossification as seen, for instance, in developing growth plates. However, the relative contribution of endochondral ossification to the changing chondrocyte phenotype in the development and progression of OA remains poorly described. In this review, we will discuss the current knowledge regarding the cartilage endochondral phenotypic changes occurring during OA development and progression, as well as the molecular and environmental effectors driving these changes. Understanding how these molecular mechanisms determine the chondrocyte cell fate in OA will be essential in enabling cartilage regenerative approaches in future treatments of OA.

Increased Activity of the Chondrocyte Translational Apparatus Accompanies Osteoarthritic Changes in Human and Rodent Knee Cartilage

OBJECTIVE

Degeneration of articular cartilage is central to the pathology of osteoarthritis (OA). However, the molecular mechanisms leading to these irreversible changes are still poorly understood. This study was undertaken to investigate how changes in the chondrocyte translational apparatus may contribute to the development and progression of knee OA.

METHODS

Articular cartilage from the knees of normal healthy subjects and patients with OA was used to analyze the activity of different components of the translational machinery. Chondrocytes isolated from lesional and nonlesional areas of the human OA cartilage were used to estimate the relative rate of protein synthesis by metabolic labeling. Experimental OA was induced by transection of the anterior cruciate ligament of rats to investigate changes in the translational apparatus associated with OA. The role of interleukin-1β (IL-1β) signaling was assessed in vitro using rat articular chondrocytes. In human or rodent knee cartilage, messenger RNA expression was analyzed by quantitative polymerase chain reaction, and protein levels were determined by immunohistochemistry and Western blotting.

RESULTS

Several novel traits of OA chondrocytes were identified, including up-regulation of the serine/threonine kinases Akt-2 and Akt-3 at the posttranscriptional level and an increased rate of total protein synthesis, likely attributable to inactivation of eukaryotic initiation factor 4E binding protein 1 (4E-BP1), a known repressor of cap-dependent translation. Inactivation of 4E-BP1 was dependent on the activity of mechanistic target of rapamycin and was crucial for the up-regulation of protein synthesis in general and expression of matrix metalloproteinase 13 and ADAMTS-5 in particular. In addition, treatment of articular chondrocytes with IL-1β led to inactivation of 4E-BP1 and up-regulation of protein synthesis.

CONCLUSION

Precise control of protein synthesis is vital for cartilage homeostasis, and its dysregulation contributes to the molecular pathology of OA. The results of this study therefore identify a novel set of potential therapeutic targets to ameliorate the effects of knee OA.

Fibroblast Growth Factor Receptor 3 Inhibits Osteoarthritis Progression in the Knee Joints of Adult Mice

OBJECTIVE

Fibroblast growth factor (FGF) signaling is involved in articular cartilage homeostasis. This study was undertaken to investigate the role and mechanisms of FGF receptor 3 (FGFR-3) in the pathogenesis of osteoarthritis (OA) caused by surgery and aging in mice.

METHODS

FGFR-3 was conditionally deleted or activated in articular chondrocytes in adult mice subjected to surgical destabilization of the medial meniscus (DMM). A mouse model of human achondroplasia was also used to assess the role of FGFR-3 in age-associated spontaneous OA. Knee joint cartilage was histologically evaluated and scored using the Osteoarthritis Research Society International system. The expression of genes associated with articular cartilage maintenance was quantitatively evaluated in hip cartilage explants. The effect of inhibiting Indian hedgehog (IHH) signaling in Fgfr3-deficient explants was analyzed.

RESULTS

Conditional Fgfr3 deletion in mice aggravated DMM-induced cartilage degeneration. Matrix metalloproteinase 13 and type X collagen levels were up-regulated, while type II collagen levels were down-regulated, in the articular cartilage of these mice. Conversely, FGFR-3 activation attenuated cartilage degeneration induced by DMM surgery and age. IHH signaling and runt-related transcription factor 2 levels in mouse articular chondrocytes were up-regulated in the absence of Fgfr3, while inhibition of IHH signaling suppressed the increases in the expression of Runx2, Mmp13, and other factors in Fgfr3-deficient mouse cartilage explants.

CONCLUSION

Our findings indicate that FGFR-3 delays OA progression in mouse knee joints at least in part via down-regulation of IHH signaling in articular chondrocytes.

Age-dependent Changes in the Articular Cartilage and Subchondral Bone of C57BL/6 Mice after Surgical Destabilization of Medial Meniscus

Age is the primary risk factor for osteoarthritis (OA), yet surgical OA mouse models such as destabilization of the medial meniscus (DMM) used for evaluating disease-modifying OA targets are frequently performed on young adult mice only. This study investigates how age affects cartilage and subchondral bone changes in mouse joints following DMM. DMM was performed on male C57BL/6 mice at 4 months (4 M), 12 months (12 M) and 19+ months (19 M+) and on females at 12 M and 18 M+. Two months after surgery, operated and unoperated contralateral knees were harvested and evaluated using cartilage histology scores and μCT quantification of subchondral bone plate thickness and osteophyte formation. The 12 M and 19 M+ male mice developed more cartilage erosions and thicker subchondral bone plates after DMM than 4 M males. The size of osteophytes trended up with age, while the bone volume fraction was significantly higher in the 19 M+ group. Furthermore, 12 M females developed milder OA than males as indicated by less cartilage degradation, less subchondral bone plate sclerosis and smaller osteophytes. Our results reveal distinct age/gender-dependent structural changes in joint cartilage and subchondral bone post-DMM, facilitating more thoughtful selection of murine age/gender when using this surgical technique for translational OA research.

A FGFR1 inhibitor patent review: progress since 2010

INTRODUCTION

FGFR1 is a well known molecular target for anticancer therapy. Many studies have proved that the regulation of FGFR1 activity is a promising therapeutic approach to treat a series of cancers. Therefore, the development of potent inhibitors has consequently become a key focus in the present drug discovery, and it is encouraging that several highly selective FGFR1 inhibitors have been identified from various sources in recent years. Areas covered: This article reviews patents and patent applications related to selective FGFR1 inhibitors published from 2010 to 2016. This summary highlights about 15 patents from different pharmaceutical companies and academic research groups. We used Baidu and NCBI search engines to find relevant patents as a search term. Expert opinion: In the past few years, considerable progress has been made in the identification and development of selective FGFR1 inhibitors in use. At present, at least 10 inhibitors of FGFR1 are in clinical trials, and several agents have shown encouraging results under experimental conditions. Given the fact that FGFR1 plays a crucial role in the regulation of cancer and other diseases, we hope that it will gain further attraction from pharmaceutical companies and encourage development of more novel, safe and efficient FGFR1 inhibitors in the future.