Fibroblast growth factor and canonical WNT/β-catenin signaling cooperate in suppression of chondrocyte differentiation in experimental models of FGFR signaling in cartilage

Current Understanding of Crouzon Syndrome Pathophysiology and New Therapeutic Approaches

Crouzon syndrome (CS) is a rare genetic disorder characterized by the premature fusion of cranial sutures, leading to craniofacial abnormalities and potential neurological complications. CS is caused primarily by gain-of-function mutations in the FGFR2 gene and, less commonly, by mutations in the FGFR3 gene (specifically associated with CS with acanthosis nigricans). Managing CS requires a multidisciplinary approach, combining early and later surgical interventions to prevent intracranial hypertension and correct craniofacial deformities, along with ongoing care to address associated complications. Recent advancements in CS classification on the basis of cranial suture involvement have refined phenotype-genotype correlations, improving personalized therapeutic strategies. This review aims to provide a comprehensive and updated overview of CS, including detailed insights into molecular genetics and biological mechanisms underlying its pathophysiology, and a depiction of the clinical features, diagnosis, and surgical aspects of CS. In addition, we delve into innovative theranostic views, where molecular genetic testing allows the design of personalized noninvasive therapeutic approaches based on innovative biotechnologies, including RNA-interference molecules, pharmacological modulation of FGFR signaling pathways, and recombinant proteins. These advancements underscore the importance of integrating molecular studies into diagnostic and therapeutic protocols to increase the precision and effectiveness of nonsurgical treatments for CS.

Basic Fibroblast Growth Factor Supports the Function of Limbal Niche Cells via the Wnt/β-Catenin Pathway

Purpose: To test the effects and underlying mechanisms of basic fibroblast growth factor (bFGF) on the limbal niche cell (LNC) function ex vivo. Methods: By using different concentrations of bFGF (0, 4, 8, 12, and 16 ng/mL) and fibroblast growth factor receptor (FGFR) inhibitors, the effects of bFGF on LNC proliferation, expression of stem cell markers, and transcription levels of the β-catenin were investigated. Single-cell RNA sequencing (scRNA-seq) was used to analyze the action and mechanisms of FGFR subtypes and the Wnt/β-catenin pathway during LNC culture. An mature corneal epithelial cell (MCEC)/LNC three-dimensional model was constructed to verify whether bFGF activates the Wnt/β-catenin pathway in LNC by inhibiting FGFR or β-catenin targets. Results: scRNA-seq showed that FGFR1 is the main receptor in LNC, along with the molecules in the Wnt pathway, including WNT2, FZD7, LRP5, LRP6, and β-catenin. The 12 ng/mL bFGF treatment group showed higher LNC proliferation rate and transcription levels of OCT4, SOX2, NANOG, and β-catenin than any other groups (P < 0.001). In the MCEC/LNC co-culture model, MCEC/LNC treated with 12 ng/mL bFGF promoted the aggregation of the spheres than other groups, associated with increased transcription levels of P63α, WNT2, β-catenin, and a decreased transcription level of CK12 (P < 0.001). Wnt/β-catenin inhibitor LF3 treatment reversed the abovementioned effect of bFGF. Conclusions: bFGF could maintain and promote the stemness of LNC via the FGFR1/Wnt2/FZD7/LRP6 axis in a concentration-dependent manner.

Signalling interaction between β-catenin and other signalling molecules during osteoarthritis development

Osteoarthritis (OA) is the most prevalent disorder of synovial joint affecting multiple joints. In the past decade, we have witnessed conceptual switch of OA pathogenesis from a 'wear and tear' disease to a disease affecting entire joint. Extensive studies have been conducted to understand the underlying mechanisms of OA using genetic mouse models and ex vivo joint tissues derived from individuals with OA. These studies revealed that multiple signalling pathways are involved in OA development, including the canonical Wnt/β-catenin signalling and its interaction with other signalling pathways, such as transforming growth factor β (TGF-β), bone morphogenic protein (BMP), Indian Hedgehog (Ihh), nuclear factor κB (NF-κB), fibroblast growth factor (FGF), and Notch. The identification of signalling interaction and underlying mechanisms are currently underway and the specific molecule(s) and key signalling pathway(s) playing a decisive role in OA development need to be evaluated. This review will focus on recent progresses in understanding of the critical role of Wnt/β-catenin signalling in OA pathogenesis and interaction of β-catenin with other pathways, such as TGF-β, BMP, Notch, Ihh, NF-κB, and FGF. Understanding of these novel insights into the interaction of β-catenin with other pathways and its integration into a complex gene regulatory network during OA development will help us identify the key signalling pathway of OA pathogenesis leading to the discovery of novel therapeutic strategies for OA intervention.

Protein interaction networks characterizing the A549 cells Klotho transfected are associated with activated pro-apoptotic Bim and suppressed Wnt/β-catenin signaling pathway

Invasive assays and lung tumor-bearing mice models using a human lung adenocarcinoma cell line A549 cells transfected with the Klotho (KL) gene, A549/KL cells, have confirmed that KL suppresses invasive/metastatic potential. This study aimed to identify the co-expression protein networks and proteomic profiles associated with A549/KL cells to understand how Klotho protein expression affects molecular networks associated with lung carcinoma malignancy. A two-step application of a weighted network correlation analysis to the cells' quantitative proteome datasets of a total of 6,994 proteins, identified by mass spectrometry-based proteomic analysis with data-independent acquisition (DIA), identified one network module as most significantly associated with the A549/KL trait. Upstream analyses, confirmed by western blot, implicated the pro-apoptotic Bim (Bcl-2-like protein 11) as a master regulator of molecular networks affected by Klotho. GeneMANIA interaction networks and quantitative proteome data implicated that Klotho interacts with two signaling axes: negatively with the Wnt/β-catenin axis, and positively by activating Bim. Our findings might contribute to the development of future therapeutic strategies.

Unraveling the Mechanisms of Sensitivity to Anti-FGF Therapies in Imatinib-Resistant Gastrointestinal Stromal Tumors (GIST) Lacking Secondary KIT Mutations

We showed previously that inhibition of KIT signaling in GISTs activates FGFR-signaling pathway rendering cancer cells resistant to receptor tyrosine kinase inhibitor (RTKi) imatinib mesylate (IM) (Gleevec) despite of absence of secondary KIT mutations and thereby illustrating a rationale for the combined (e.g., KIT- and FGFR-targeted) therapies. We show here that long-term culture of IM-resistant GISTs (GIST-R1) with IM substantially down-regulates KIT expression and induces activation of the FGFR-signaling cascade, evidenced by increased expression of total and phosphorylated forms of FGFR1 and 2, FGF-2, and FRS-2, the well-known adaptor protein of the FGF-signaling cascade. This resulted in activation of both AKT- and MAPK-signaling pathways shown on mRNA and protein levels, and rendered cancer cells highly sensitive to pan-FGFR-inhibitors (BGJ 398, AZD 4547, and TAS-120). Indeed, we observed a significant decrease of IC50 values for BGJ 398 in the GIST subclone (GIST-R2) derived from GIST-R1 cells continuously treated with IM for up to 12 months. An increased sensitivity of GIST-R2 cells to FGFR inhibition was also revealed on the xenograft models, illustrating a substantial (>70%) decrease in tumor size in BGJ 398-treated animals when treated with this pan-FGFR inhibitor. Similarly, an increased intra-tumoral apoptosis as detected by immunohistochemical (IHC)-staining for cleaved caspase-3 on day 5 of the treatment was found. As expected, both BGJ 398 and IM used alone lacked the pro-apoptotic and growth-inhibitory activities on GIST-R1 xenografts, thereby revealing their resistance to these TKis when used alone. Important, the knockdown of FGFR2, and, in much less content, FGF-2, abrogated BGJ 398's activity against GIST-R2 cells both in vitro and in vivo, thereby illustrating the FGF-2/FGFR2-signaling axis in IM-resistant GISTs as a primary molecular target for this RTKi. Collectively, our data illustrates that continuous inhibition of KIT signaling in IM-resistant GISTs lacking secondary KIT mutations induced clonal heterogeneity of GISTs and resulted in accumulation of cancer cells with overexpressed FGF-2 and FGFR1/2, thereby leading to activation of FGFR-signaling. This in turn rendered these cells extremely sensitive to the pan-FGFR inhibitors used in combination with IM, or even alone, and suggests a rationale to re-evaluate the effectiveness of FGFR-inhibitors in order to improve the second-line therapeutic strategies for selected subgroups of GIST patients (e.g., IM-resistant GISTs lacking secondary KIT mutations and exhibiting the activation of the FGFR-signaling pathway).

Roles of Local Soluble Factors in Maintaining the Growth Plate: An Update

The growth plate is a cartilaginous tissue found at the ends of growing long bones, which contributes to the lengthening of bones during development. This unique structure contains at least three distinctive layers, including resting, proliferative, and hypertrophic chondrocyte zones, maintained by a complex regulatory network. Due to its soft tissue nature, the growth plate is the most susceptible tissue of the growing skeleton to injury in childhood. Although most growth plate damage in fractures can heal, some damage can result in growth arrest or disorder, impairing leg length and resulting in deformity. In this review, we re-visit previously established knowledge about the regulatory network that maintains the growth plate and integrate current research displaying the most recent progress. Next, we highlight local secretary factors, such as Wnt, Indian hedgehog (Ihh), and parathyroid hormone-related peptide (PTHrP), and dissect their roles and interactions in maintaining cell function and phenotype in different zones. Lastly, we discuss future research topics that can further our understanding of this unique tissue. Given the unmet need to engineer the growth plate, we also discuss the potential of creating particular patterns of soluble factors and generating them in vitro.

Hyaline Cartilage Microtissues Engineered from Adult Dedifferentiated Chondrocytes: Safety and Role of WNT Signaling

The repair of damaged articular cartilage is an unmet medical need. Chondrocyte-based cell therapy has been used to repair cartilage for over 20 years despite current limitations. Chondrocyte dedifferentiation upon expansion in monolayer is well known and is the main obstacle to their use as cell source for cartilage repair. Consequently, current approaches often lead to fibrocartilage, which is biomechanically different from hyaline cartilage and not effective as a long-lasting treatment. Here, we describe an innovative 3-step method to engineer hyaline-like cartilage microtissues, named Cartibeads, from high passage dedifferentiated chondrocytes. We show that WNT5A/5B/7B genes were highly expressed in dedifferentiated chondrocytes and that a decrease of the WNT signaling pathway was instrumental for full re-differentiation of chondrocytes, enabling production of hyaline matrix instead of fibrocartilage matrix. Cartibeads showed hyaline-like characteristics based on GAG quantity and type II collagen expression independently of donor age and cartilage quality. In vivo, Cartibeads were not tumorigenic when transplanted into SCID mice. This simple 3-step method allowed a standardized production of hyaline-like cartilage microtissues from a small cartilage sample, making Cartibeads a promising candidate for the treatment of cartilage lesions.

Patient Selection Approaches in FGFR Inhibitor Trials-Many Paths to the Same End?

Inhibitors of fibroblast growth factor receptor (FGFR) signaling have been investigated in various human cancer diseases. Recently, the first compounds received FDA approval in biomarker-selected patient populations. Different approaches and technologies have been applied in clinical trials, ranging from protein (immunohistochemistry) to mRNA expression (e.g., RNA in situ hybridization) and to detection of various DNA alterations (e.g., copy number variations, mutations, gene fusions). We review, here, the advantages and limitations of the different technologies and discuss the importance of tissue and disease context in identifying the best predictive biomarker for FGFR targeting therapies.

Study on the Role of MicroRNA-214 in the Rehabilitation of Cartilage in Mice with Exercise-Induced Traumatic Osteoarthritis

This study aimed to explore the possible relationship between the expression of Micro RNA-214 (miR-214) and the pathogenesis and recovery in mice with post-traumatic osteoarthritis (PTOA). In this study, 40 male C57BL/6 mice were randomly divided into five groups: model control (MC) group, model (M) group, rehabilitation control (RC) group, model + rehabilitation (M + R) group, and model + convalescent (M + C) group. Four weeks of high-intensity treadmill exercise (HITE) and 4 weeks of moderate-intensity treadmill exercise (MITE) were implemented for PTOA modeling and rehabilitation, respectively. In vitro, 10% elongation mechanical strain was used for IL-1β stimulated chondrocytes. We found that compared with the MC group, there was a significant increase in the aspect of inflammation and catabolism while a dramatic fall in miR-214 expression was observed in the M group. After the 4 weeks of MITE, the level of inflammation and metabolism, as well as miR-214 expression, was partially reversed in the M + R group compared with the M + C group. The expression of miR-214 decreased dramatically after chondrocyte stimulation by IL-1β and then increased significantly after 10% strain was applied to IL-1β-treated cells. These results suggest that a suitable mechanical load can increase the expression of miR-214, and that miR-214 may play a chondroprotective effect in the development of OA.

A registry of achondroplasia: a 6-year experience from the Czechia and Slovak Republic

Background

Achondroplasia (ACH) is one of the most prevalent genetic forms of short-limbed skeletal dysplasia, caused by gain-of-function mutations in the receptor tyrosine kinase FGFR3. In August 2021, the C-type natriuretic peptide (CNP) analog vosoritide was approved for the treatment of ACH. A total of six other inhibitors of FGFR3 signaling are currently undergoing clinical evaluation for ACH. This progress creates an opportunity for children with ACH, who may gain early access to the treatment by entering clinical trials before the closure of their epiphyseal growth plates and cessation of growth. Pathophysiology associated with the ACH, however, demands a long observational period before admission to the interventional trial. Public patient registries can facilitate the process by identification of patients suitable for treatment and collecting the data necessary for the trial entry.

Results

In 2015, we established the prospective ACH registry in the Czechia and the Slovak Republic (http://www.achondroplasia-registry.cz). Patient data is collected through pediatric practitioners and other relevant specialists. After informed consent is given, the data is entered to the online TrialDB system and stored in the Oracle 9i database. The initial cohort included 51 ACH children (average age 8.5 years, range 3 months to 14 years). The frequency of selected neurological, orthopedic, or ORL diagnoses is also recorded. In 2015–2021, a total of 89 measurements of heights, weights, and other parameters were collected. The individual average growth rate was calculated and showed values without exception in the lower decile for the appropriate age. Evidence of paternal age effect was found, with 58.7% of ACH fathers older than the general average paternal age and 43.5% of fathers older by two or more years. One ACH patient had orthopedic limb extension and one patient received growth hormone therapy. Low blood pressure or renal impairment were not found in any patient.

Conclusion

The registry collected the clinical information of 51 pediatric ACH patients during its 6 years of existence, corresponding to ~ 60% of ACH patients living in the Czechia and Slovak Republic. The registry continues to collect ACH patient data with annual frequency to monitor the growth and other parameters in preparation for future therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02374-x.

The role of fibroblast growth factor 8 in cartilage development and disease

Fibroblast growth factor 8 (FGF‐8), also known as androgen‐induced growth factor (AIGF), is presumed to be a potent mitogenic cytokine that plays important roles in early embryonic development, brain formation and limb development. In the bone environment, FGF‐8 produced or received by chondrocyte precursor cells binds to fibroblast growth factor receptor (FGFR), causing different levels of activation of downstream signalling pathways, such as phospholipase C gamma (PLCγ)/Ca²⁺, RAS/mitogen‐activated protein kinase‐extracellular regulated protein kinases (RAS/MAPK‐MEK‐ERK), and Wnt‐β‐catenin‐Axin2 signalling, and ultimately controlling chondrocyte proliferation, differentiation, cell survival and migration. However, the molecular mechanism of FGF‐8 in normal or pathological cartilage remains unclear, and thus, FGF‐8 represents a novel exploratory target for studies of chondrocyte development and cartilage disease progression. In this review, studies assessing the relationship between FGF‐8 and chondrocytes that have been published in the past 5 years are systematically summarized to determine the probable mechanism and physiological effect of FGF‐8 on chondrocytes. Based on the existing research results, a therapeutic regimen targeting FGF‐8 is proposed to explore the possibility of treating chondrocyte‐related diseases.

Temporospatial regulation of intraflagellar transport is required for the endochondral ossification in mice

Ciliogenic components, such as the family of intraflagellar transport (IFT) proteins, are recognized to play key roles in endochondral ossification, a critical process to form most bones. However, the unique functions and roles of each IFT during endochondral ossification remain unclear. Here, we show that IFT20 is required for endochondral ossification in mice. Utilizing osteo-chondrocyte lineage-specific Cre mice (Prx1-Cre and Col2-Cre), we deleted Ift20 to examine its function. Although chondrocyte-specific Ift20 deletion with Col2-Cre mice did not cause any overt skeletal defects, mesoderm-specific Ift20 deletion using Prx1-Cre (Ift20:Prx1-Cre) mice resulted in shortened limb outgrowth. Primary cilia were absent on chondrocytes of Ift20:Prx1-Cre mice, and ciliary-mediated Hedgehog signaling was attenuated in Ift20:Prx1-Cre mice. Interestingly, loss of Ift20 also increased Fgf18 expression in the perichondrium that sustained Sox9 expression, thus preventing endochondral ossification. Inhibition of enhanced phospho-ERK1/2 activation partially rescued defective chondrogenesis in Ift20 mutant cells, supporting an important role for FGF signaling. Our findings demonstrate that IFT20 is a critical regulator of temporospatial FGF signaling that is required for endochondral ossification.

Wingless-type mouse mammary tumor virus integration site regulation of bovine theca cells

Ovarian paracrine mediation by components of the wingless-type mouse mammary tumor virus integration site ligands (WNT1 to 11) and their receptors, frizzled family members (FZD1 to 10), has been proposed. Secreted truncated forms of FZD proteins (e.g., secreted frizzled-related protein 4 [SFRP4]) block the action of WNT ligands. Dickkopf-1 (DKK1) is another WNT antagonist, and R-spondin-1 (RSPO1) is one of a group of four secreted proteins that enhance WNT/β-catenin signaling. Our hypothesis was that granulosa cells signal theca cells (TCs) via SFRP4, DKK1, RSPO1, and WNT secretion to regulate TC differentiation and proliferation. Therefore, in vitro experiments were conducted to study the effects of WNT family member 3A (WNT3A), WNT5A, RSPO1, DKK1, insulin-like growth factor 1 (IGF1), bone morphogenetic protein 7 (BMP7), Indian hedgehog (IHH), and fibroblast growth factor 9 (FGF9) on bovine TC proliferation and steroidogenesis. TCs of large (8 to 20 mm) and small (3 to 6 mm) follicles were collected from bovine ovaries; TC monolayers were established in vitro and treated with various doses of recombinant human WNT3A, WNT5A, RSPO1, DKK1, IGF1, FGF9, BMP7, IHH, and/or ovine luteinizing hormone (LH) in serum-free medium for 48 h. In experiment 1, using LH-treated TC, IGF1, IHH, and WNT3A increased (P < 0.05) cell numbers and androstenedione production, whereas WNT3A and BMP7 inhibited (P < 0.05) progesterone production. In experiment 2, FGF9 blocked (P < 0.05) the WNT3A-induced increase in androstenedione production in LH plus IGF1-treated TC. In experiment 3, RSPO1 further increased (P < 0.05) LH plus IGF1-induced progesterone and androstenedione production. In experiment 4, SFRP4 and DKK1 alone had no significant effect on TC proliferation or progesterone production of large-follicle TC but both blocked the inhibitory effect of WNT5A on androstenedione production. In contrast, DKK1 alone inhibited (P < 0.05) small-follicle TC androstenedione production whereas SFRP4 was without effect. We conclude that the ovarian TC WNT system is functional in cattle, with WNT3A increasing proliferation and androstenedione production of TC.

Co-transfection with BMP2 and FGF2 via chitosan nanoparticles potentiates osteogenesis in human adipose-derived stromal cells in vitro

OBJECTIVE

To investigate if co-transfection of human bone morphogenetic protein 2 (BMP-2, BMP2) and human fibroblast growth factor 2 (FGF2, FGF2) via chitosan nanoparticles promotes osteogenesis in human adipose tissue-derived stem cells (ADSCs) in vitro.

MATERIALS AND METHODS

Recombinant BMP2 and/or FGF2 expression vectors were constructed and packaged into chitosan nanoparticles. The chitosan nanoparticles were characterized by atomic force microscopy. Gene and protein expression levels of BMP-2 and FGF2 in ADSCs in vitro were evaluated by real-time polymerase chain reaction (PCR), western blot, and enzyme-linked immunosorbent assay. Osteocalcin (OCN) and bone sialoprotein (BSP) gene expression were also evaluated by real-time PCR to assess osteogenesis.

RESULTS

The prepared chitosan nanoparticles were spherical with a relatively homogenous size distribution. The BMP2 and FGF2 vectors were successfully transfected into ADSCs. BMP-2 and FGF2 mRNA and protein levels were significantly up-regulated in the co-transfection group compared with the control group. OCN and BSP mRNA levels were also significantly increased in the co-transfection group compared with cells transfected with BMP2 or FGF2 alone, suggesting that co-transfection significantly enhanced osteogenesis.

CONCLUSIONS

Co-transfection of human ADSCs with BMP2/FGF2 via chitosan nanoparticles efficiently promotes the osteogenic properties of ADSCs in vitro.

Research advances in cartilage stem cells markers and induced differentiation

Cartilage stem cells (CSCs) are cells that self-proliferate, have surface antigen expression, and have multidirectional differentiation potential in the articular cartilage. CSCs, as an ideal source of stem cells, has a good application prospect in stem cell therapy. This article reviews the CSCs markers, cartilage differentiation signaling pathway, and clinical treatment of osteoarthritis.

FGFR3 Alterations in the Era of Immunotherapy for Urothelial Bladder Cancer

FGFR3 is a prognostic and predictive marker and is a validated therapeutic target in urothelial bladder cancer. Its utility as a marker and target in the context of immunotherapy is incompletely understood. We review the role of FGFR3 in bladder cancer and discuss preclinical and clinical clues of its effectiveness as a patient selection factor and therapeutic target in the era of immunotherapy.

Wnt signaling in chondroprogenitors during long bone development and growth

Wnt signaling together with other signaling pathways governs cartilage development and the growth plate function during long bone formation and growth. β-catenin-dependent Wnt signaling is a specific lineage determinant of skeletal mesenchymal cells toward chondrogenic or osteogenic direction. Once cartilage forms and the growth plate organize, Wnt signaling continues to regulate proliferation and differentiation of the growth plate chondrocytes. Although chondrocytes in the growth plate have a high capacity to proliferate, new cells must be supplied to the growth plate from chondroprogenitor population. Advances in in vivo cell tracking techniques have demonstrated the importance of Wnt signaling in driving tissue renewal. The Wnt-responsive cells, genetically marked by the Wnt-reporter system, are found as stem cells in various tissues. Similarly, Wnt-responsive cells are found in the periphery of the growth plate and expanded to constitute entire column structure, indicating that Wnt signaling participates in the regulation of chondroprogenitors in the growth plate. This review will discuss advancements in research of progenitors in the growth plate, specifically focusing on Wnt/β-catenin signaling.

Fgfr3 mutation disrupts chondrogenesis and bone ossification in zebrafish model mimicking CATSHL syndrome partially via enhanced Wnt/β-catenin signaling

CATSHL syndrome, characterized by camptodactyly, tall stature and hearing loss, is caused by loss-of-function mutations of fibroblast growth factor receptors 3 (FGFR3) gene. Most manifestations of patients with CATSHL syndrome start to develop in the embryonic stage, such as skeletal overgrowth, craniofacial abnormalities, however, the pathogenesis of these phenotypes especially the early maldevelopment remains incompletely understood. Furthermore, there are no effective therapeutic targets for this skeleton dysplasia. Methods: We generated fgfr3 knockout zebrafish by CRISPR/Cas9 technology to study the developmental mechanisms and therapeutic targets of CATSHL syndrome. Several zebrafish transgenic lines labeling osteoblasts and chondrocytes, and live Alizarin red staining were used to analyze the dynamical skeleton development in fgfr3 mutants. Western blotting, whole mount in situ hybridization, Edu labeling based cell proliferation assay and Wnt/β-catenin signaling antagonist were used to explore the potential mechanisms and therapeutic targets. Results: We found that fgfr3 mutant zebrafish, staring from early development stage, showed craniofacial bone malformation with microcephaly and delayed closure of cranial sutures, chondroma-like lesion and abnormal development of auditory sensory organs, partially resembling the clinical manifestations of patients with CATSHL syndrome. Further studies showed that fgfr3 regulates the patterning and shaping of pharyngeal arches and the timely ossification of craniofacial skeleton. The abnormal development of pharyngeal arch cartilage is related to the augmented hypertrophy and disordered arrangement of chondrocytes, while decreased proliferation, differentiation and mineralization of osteoblasts may be involved in the delayed maturation of skull bones. Furthermore, we revealed that deficiency of fgfr3 leads to enhanced IHH signaling and up-regulated canonical Wnt/β-catenin signaling, and pharmacological inhibition of Wnt/β-catenin could partially alleviate the phenotypes of fgfr3 mutants. Conclusions: Our study further reveals some novel phenotypes and underlying developmental mechanism of CATSHL syndrome, which deepens our understanding of the pathogenesis of CATSHL and the role of fgfr3 in skeleton development. Our findings provide evidence that modulation of Wnt/β-catenin activity could be a potential therapy for CATSHL syndrome and related skeleton diseases.

A Transcriptome Sequencing Study on Genome-Wide Gene Expression Differences of 3D Cultured Chondrocytes in Hydrogel Scaffolds with Different Gel Density

Hydrogel is considered as a promising cell delivery vehicle in cartilage tissue engineering, whose tunable microenvironments may influence the function and fate of encapsulated chondrocytes. Here, the transcriptomes of chondrocytes that are encapsulated and cultured in hydrogel constructs respectively made of 0.8% and 4% alginate solution are investigated. Differences in chondrocyte transcriptome are detected via RNA-sequencing from these two cultural conditions. The differentially expressed genes (DEGs) are reflected in extracellular matrix (ECM) secretion, cell cycle, proliferation, cartilage development, and so on. Significantly, the expression of DEGs associated with cartilage ECM and cell proliferation are upregulated in 0.8% constructs; whilst the expressions of DEGs involved in cell cycle and matrix degradation are upregulated in 4% constructs. Moreover, interestingly, the expressions of chondrocyte hypertrophy markers are upregulated in 0.8% constructs; while 4% constructs seemingly favor the long-term maintenance of chondrocyte phenotype. Taken together, this study confirms on transcriptomic level that gel density affects gene expression and phenotype of the encapsulated chondrocytes; therefore, it may provide guidance for future design and fabrication of cartilage tissue engineering scaffolds.

Effect of Ginsenoside Rg1 on the intervertebral disc degeneration rats and the degenerative pulposus cells and its mechanism

OBJECTIVE

To explore the effect of ginsenoside Rg1 on intervertebral disc degeneration (IVDD) in vivo and in vitro and its mechanism.

METHODS

60 rats were underwent surgery to construct rat models of IVDD and divided in the sham group, model group and gradient G-Rg1 groups (10 mg/kg/d, 20 mg/kg/d and 40 mg/kg/d).The change of histology was observed by HE staining, the water content and the expression of β-catenin in IVD were detected. Rat nucleus pulposus cells(NPCs) were isolated from IVDD rats and divided in D-NPCs group, and gradient G-Rg1 groups(20 μg/ml, 50 μg/ml and 100 μg/ml).The cell proliferation activity, cell apoptosis rate,the expression of proteins related to ECM and Wnt/β-catenin were detected respectively, Finally the agonist of Wnt/β-catenin pathway LiCl was used for reversed experiments.

RESULTS

In vivo, G-Rg1 treatment could improve the structural disorganization, low water content, NPCs number and aggrecan and collagenⅡ expression in IVD and down-regulate the expression of β-catenin. In vitro NPCs, G-Rg1 treatment could improve the low cell proliferation, high apoptosis rate and low expression of aggrecan and collagenⅡ in degenerative NPCs in a dose-dependent manner.G-Rg1 treatment could down-regulate the expression of proteins related to β-catenin signal and LiCl could reverse the increase of cell proliferation and ECM synthesis, decrease of apoptosis of degenerative NPCs induced by G-Rg1.

CONCLUSION

G-Rg1 could promote ECM synthesis of degenerative NPCs and inhibiting its apoptosis, improve the IVDD via inhibiting the Wnt/β-catenin pathway.

Inhibition of FGFR Signaling Partially Rescues Osteoarthritis in Mice Overexpressing High Molecular Weight FGF2 Isoforms

Fibroblast growth factor 2 (FGF2) and fibroblast growth factor receptors (FGFRs) are key regulatory factors in osteoarthritis (OA). HMWTg mice overexpress the high molecular weight FGF2 isoforms (HMWFGF2) in osteoblast lineage and phenocopy both Hyp mice (which overexpress the HMWFGF2 isoforms in osteoblasts and osteocytes) and humans with X-linked hypophosphatemia (XLH). We previously reported that, similar to Hyp mice and XLH subjects who develop OA, HMWTg mice also develop an OA phenotype associated with increased degradative enzymes and increased FGFR1 compared with VectorTg mice. Therefore, in this study, we examined whether in vivo treatment with the FGFR tyrosine kinase inhibitor NVP-BGJ398 (BGJ) would modulate development of the OA phenotype in knee joints of HMWTg mice. VectorTg and HMWTg mice (21 days of age) were treated with vehicle or BGJ for 13 weeks. Micro-computed tomography images revealed irregular shape and thinning of the subchondral bone with decreased trabecular number and thickness within the epiphyses of vehicle-treated HMWTg knees, which was partially rescued following BGJ treatment. Articular cartilage thickness was decreased in vehicle-treated HMWTg mice, and was restored to the cartilage thickness of VectorTg mice in the BGJ-treated HMWTg group. Increased OA degradative enzymes present in HMWTg vehicle-treated joints decreased after BGJ treatment. OA in HMWTg mice was associated with increased Wnt signaling that was rescued by BGJ treatment. This study demonstrates that overexpression of the HMWFGF2 isoforms in preosteoblasts results in osteoarthropathy that can be partially rescued by FGFR inhibitor via reduction in activated Wnt signaling.

Dog as a Model for Osteoarthritis: The FGF4 Retrogene Insertion May Matter

Osteoarthritis (OA) is a degenerative joint disease associated with chronic pain and disability in humans and companion animals. The canine species can be subdivided into non-chondrodystrophic (NCD) and chondrodystrophic (CD) dogs, the latter having disproportionally short limbs due to disturbance in endochondral ossification of long bones. This phenotype is associated with retrogene insertions of the fibroblast growth factor 4 (FGF4) gene, resulting in enhanced fibroblast growth factor receptor 3 (FGFR3) signaling. The effect on cartilage is unknown and in experimental studies with dogs, breeds are seemingly employed randomly. The aim of this study was to determine whether CD- and NCD-derived cartilage differs on a structural and biochemical level, and to explore the relationship between FGF4 associated chondrodystrophy and OA. Cartilage explants from CD and NCD dogs were cultured for 21 days. Activation of canonical Wnt signaling was assessed in primary canine chondrocytes. OA and synovitis severity from an experimental OA model were compared between healthy and OA samples from CD and NCD dogs. Release of glycosaminoglycans, DNA content, and cyclooxygenase 2 (COX-2) expression were higher in NCD cartilage explants. Healthy cartilage from NCD dogs displayed higher cartilage degeneration and synovitis scores, which was aggravated by the induction of OA. Dikkopf-3 gene expression was higher in NCD cartilage. No differences in other Wnt pathway read outs were found. To conclude, chondrodystrophy associated with the FGF4 retrogene seems to render CD dogs less susceptible to the development of OA when compared with NCD dogs. These differences should be considered when choosing a canine model to study the pathobiology and new treatment strategies of OA. © 2019 The Authors. Journal of Orthopaedic Research^® Published by Wiley Periodicals, Inc. J Orthop Res 37:2550-2560, 2019.

EFFECTS OF CONTUSION AND EXHAUSTIVE EXERCISE ON MG53, PTRF IN SKELETAL MUSCLE OF RATS

ABSTRACT Objectives To study the effects of contusion and exhaustive exercise on gene expression of MG53, PTRF, Pax7 and β-catenin in skeletal muscle of rats, and reveal the repair mechanism of skeletal muscle injury. Methods Forty-two male Wistar rats were randomly divided into 7 groups, with 6 rats in each group. All groups were euthanized at different time points after exhaustive exercise and contusion, respectively, while the control group was euthanized in resting state. The right gastrocnemius muscles were measured for mRNAs of MG53, PTRF, Pax7 and β-catenin by real time PCR. Results MG53 mRNA and PTRF mRNA of skeletal muscle in groups immediately after exhaustive exercise and after contusion increased significantly (p<0.05), while the two indices decreased constantly at 24 and 48 hours after injury with a similar change trend. Compared with the control group, Pax7 mRNA of skeletal muscle as a marker showed no significant difference in exhaustive exercise groups, but decreased at 48 hours after contusion (p<0.05). β-catenin mRNA of skeletal muscle down-regulated significantly over 24 hours after injury, then activated with an increased value at 48 hours after contusion (p<0.05). As a whole, the variations in the above indices in the contusion groups covered a wider range than in the exhaustive exercise groups. Conclusion The cytomembrane repair mechanism of MG53 and PTRF began immediately after the end of exhaustive exercise and contusion. Activation of Pax7 as the satellite cell marker took longer, and Wnt/β-catenin pathway showed first a decrease and then an increase resulting from the time-dependent gene expression during the repair of skeletal muscle injury. Level of evidence III, Therapeutic studies investigating the results of treatment.

IM-12 activates the Wnt-β-catenin signaling pathway and attenuates rtPA-induced hemorrhagic transformation in rats after acute ischemic stroke

Hemorrhagic transformation (HT) is a devastating complication for patients with acute ischemic stroke (AIS) who are treated with tissue plasminogen activator (tPA). HT is associated with high morbidity and mortality, but no effective treatments are currently available to reduce the risk of HT. Therefore, methods to prevent HT are urgently needed. In this study, we used IM-12, an inhibitor of glycogen synthase kinase 3β (GSK-3β), to evaluate the role of the Wnt-β-catenin signaling pathway in recombinant tPA (rtPA)-induced HT. Sprague-Dawley rats were subjected to a middle cerebral artery occlusion (MCAO) model of ischemic stroke, and then were either administered rtPA, rtPA combined with IM-12, or the vehicle at 4 h after stroke was induced. Our results indicate that rats subjected to HT had more severe neurological deficits, brain edema, and blood-brain barrier (BBB) breakdown, and had a greater infarction volume than the control group. Rats treated with IM-12 had improved outcomes compared with those of rats treated with rtPA alone. Moreover, IM-12 increased the protein expression of β-catenin and downstream proteins while suppressing the expression of GSK-3β. These results suggest that IM-12 reduces rtPA-induced HT and attenuates BBB disruption, possibly through activation of the Wnt-β-catenin signaling pathway, and provides a potential therapeutic strategy for preventing tPA-induced HT after AIS.

Genome-wide DNA methylation profiling of hip articular cartilage identifies differentially methylated loci associated with osteonecrosis of the femoral head

OBJECTIVE

Recent studies demonstrated a critical role of hip articular cartilage destruction in the development of osteonecrosis of the femoral head (ONFH). The aim of this study was to characterize the genome-wide DNA methylation profile of hip cartilage obtained from patients with ONFH and healthy subjects.

METHODS

Hip articular cartilage specimens were collected from 15 ONFH patients (including 11 males and 4 females) and 15 control subjects (including 11 males and 4 females) with femoral neck fracture. The average ages of the ONFH patients and control subjects were 50.27 ± 5.27 years and 61.67 ± 3.38 years, respectively. Genome-wide DNA methylation profiles of 5 ONFH and 5 control cartilages were determined by Illumina HumanMethylation850 array. Differential methylation analysis of DNA methylation profiles were performed by the empirical Bayes moderated t-test of the limma package. Mass spectrograph (MS) analysis of 10 ONFH cartilages and 10 normal cartilages were performed to validate the results of genome-wide DNA methylation profiling. Immunohistochemistry (IHC) of 4 ONFH cartilages and 4 control cartilages were conducted to evaluate the expression levels of proteins encoded by identified differentially methylated genes. t-test was used to assess the significance of protein expression differences between ONFH patients and controls in IHC.

RESULTS

We identified a total of 2872 differentially methylated CpG sites, annotated to 480 hypermethylated genes and 1335 hypomethylated genes for ONFH. The results of MS validation were consistent with that of genome-wide DNA methylation profiling. IHC further confirmed the increased protein expression of CARS (mean and 95%CI of superficial zone 59.67% [48.46, 56.14], and deep zone 31% [25.85, 30.61]), PDE4D (superficial zone 50.33% [33.64, 40.68] and deep zone 28.67% [10.81, 36.47]), ADAMTS12 (superficial zone 53.67% [36.01, 40.93] and deep zone 34.67% [22.56, 37.18]), LRP5 (superficial zone 59.63% [27.32, 39.61] and deep zone 22.95% [5.28, 19.29]), RUNX2 (superficial zone 52.58% [11.64, 31.33] and deep zone 35.01% [10.03, 27.44]) in ONFH articular cartilage.

CONCLUSION

Our results suggest the implication of DNA methylation alterations in the development of ONFH, and provide novel clues for pathogenetic and therapeutic studies of ONFH.

The Autocrine FGF/FGFR System in both Skin and Uveal Melanoma: FGF Trapping as a Possible Therapeutic Approach

Fibroblast growth factors (FGFs) play non-redundant autocrine/paracrine functions in various human cancers. The Cancer Genome Atlas (TCGA) data mining indicates that high levels of FGF and/or FGF receptor (FGFR) expression are associated with reduced overall survival, chromosome 3 monosomy and BAP1 mutation in human uveal melanoma (UM), pointing to the FGF/FGFR system as a target for UM treatment. Here, we investigated the impact of different FGF trapping approaches on the tumorigenic and liver metastatic activity of liver metastasis-derived murine melanoma B16-LS9 cells that, similar to human UM, are characterized by a distinctive hepatic tropism. In vitro and in vivo experiments demonstrated that the overexpression of the natural FGF trap inhibitor long-pentraxin 3 (PTX3) inhibits the oncogenic activity of B16-LS9 cells. In addition, B16-LS9 cells showed a reduced tumor growth and liver metastatic activity when grafted in PTX3-overexpressing transgenic mice. The efficacy of the FGF trapping approach was confirmed by the capacity of the PTX3-derived pan-FGF trap small molecule NSC12 to inhibit B16-LS9 cell growth in vitro, in a zebrafish embryo orthotopic tumor model and in an experimental model of liver metastasis. Possible translational implications for these observations were provided by the capacity of NSC12 to inhibit FGF signaling and cell proliferation in human UM Mel285, Mel270, 92.1, and OMM2.3 cells. In addition, NSC12 caused caspase-3 activation and PARP cleavage followed by apoptotic cell death as well as β-catenin degradation and inhibition of UM cell migration. Together, our findings indicate that FGF trapping may represent a novel therapeutic strategy in UM.

Fibroblast growth factors in skeletal development

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are expressed throughout all stages of skeletal development. In the limb bud and in cranial mesenchyme, FGF signaling is important for formation of mesenchymal condensations that give rise to bone. Once skeletal elements are initiated and patterned, FGFs regulate both endochondral and intramembranous ossification programs. In this chapter, we review functions of the FGF signaling pathway during these critical stages of skeletogenesis, and explore skeletal malformations in humans that are caused by mutations in FGF signaling molecules.

Cenani-Lenz syndrome and other related syndactyly disorders due to variants in LRP4, GREM1/FMN1, and APC: Insight into the pathogenesis and the relationship to polyposis through the WNT and BMP antagonistic pathways

Cenani-Lenz (C-L) syndrome is characterized by oligosyndactyly, metacarpal synostosis, phalangeal disorganization, and other variable facial and systemic features. Most cases are caused by homozygous and compound heterozygous missense and splice mutations of the LRP4 gene. Currently, the syndrome carries one OMIM number (212780). However, C-L syndrome-like phenotypes as well as other syndactyly disorders with or without metacarpal synostosis/phalangeal disorganization are also known to be associated with specific LRP4 mutations, adenomatous polyposis coli (APC) truncating mutations, genomic rearrangements of the GREM1-FMN1 locus, as well as FMN1 mutations. Surprisingly, patients with C-L syndrome-like phenotype caused by APC truncating mutations have no polyposis despite the increased levels of β catenin. The LRP4 and APC proteins act on the WNT (wingless-type integration site family) canonical pathway, whereas the GREM-1 and FMN1 proteins act on the bone morphogenetic protein (BMP) pathway. In this review, we discuss the different mutations associated with C-L syndrome, classify its clinical features, review familial adenomatous polyposis caused by truncating APC mutations and compare these mutations to the splicing APC mutation associated with syndactyly, and finally, explore the pathophysiology through a review of the cross talks between the WNT canonical and the BMP antagonistic pathways.

Impact of Wnt signals on human intervertebral disc cell regeneration

Although preconditioning strategies are growing areas of interest for therapies targeting intervertebral discs (IVDs), it is unknown whether the Wnt signals previously implicated in chondrogenesis, Wnt3A, Wnt5A, and Wnt11, play key roles in the promotion of human nucleus pulposus (NP) cell redifferentiation. In this study, NP cells isolated from herniated disc patients were transduced with lentiviral vectors to overexpress the WNT3A, WNT5A, or WNT11 genes, or CRISPR associated protein 9 (Cas9)/single-guide RNA (sgRNA) vectors to knock out these genes. Following expansion, transduced NP cells were induced for redifferentiation toward the NP phenotype. The overexpression of specific WNT factors led to increases in both glycosaminoglycan (GAG) deposition and expression of redifferentiation genes. These effects were attenuated by knockout of the same WNT genes. These results indicate that specific WNT signals can regulate the expression of redifferentiation genes, unequally impact GAG deposition, and contribute to the redifferentiation of human NP cells. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3196-3207, 2018.

The inositol phosphatase SHIP2 enables sustained ERK activation downstream of FGF receptors by recruiting Src kinases

Sustained activation of extracellular signal-regulated kinase (ERK) drives pathologies caused by mutations in fibroblast growth factor receptors (FGFRs). We previously identified the inositol phosphatase SHIP2 (also known as INPPL1) as an FGFR-interacting protein and a target of the tyrosine kinase activities of FGFR1, FGFR3, and FGFR4. We report that loss of SHIP2 converted FGF-mediated sustained ERK activation into a transient signal and rescued cell phenotypes triggered by pathologic FGFR-ERK signaling. Mutant forms of SHIP2 lacking phosphoinositide phosphatase activity still associated with FGFRs and did not prevent FGF-induced sustained ERK activation, demonstrating that the adaptor rather than the catalytic activity of SHIP2 was required. SHIP2 recruited Src family kinases to the FGFRs, which promoted FGFR-mediated phosphorylation and assembly of protein complexes that relayed signaling to ERK. SHIP2 interacted with FGFRs, was phosphorylated by active FGFRs, and promoted FGFR-ERK signaling at the level of phosphorylation of the adaptor FRS2 and recruitment of the tyrosine phosphatase PTPN11. Thus, SHIP2 is an essential component of canonical FGF-FGFR signal transduction and a potential therapeutic target in FGFR-related disorders.

Deletion of Axin1 in condylar chondrocytes leads to osteoarthritis-like phenotype in temporomandibular joint via activation of β-catenin and FGF signaling

Osteoarthritis (OA) in the temporomandibular joint (TMJ) is a degenerative disease in the adult, which is characterized by the pathological degeneration of condylar cartilage. Axin1 plays a critical role in the regulation of cartilage development and homeostasis. To determine the role of Axin1 in TMJ tissue at the adult stage, we generated Axin1^Agc1ER mice, in which Axin1 was deleted in aggrecan-expressing chondrocytes at 2 months of age. Histology, histomorphometry, and immunostaining analyses were performed using TMJ tissues harvested from 4- and 6-month-old mice after tamoxifen administration. Total RNA isolated from TMJ cartilage of 6-month-old mice was used for gene expression analysis. Progressive OA-like degeneration was observed in condylar cartilage in Axin1 knockout (KO) mice with loss of surface continuity and the formation of vertical fissures. In addition, reduced alcian blue staining in condylar cartilage was also found in Axin1 KO mice. Immunostaining and reverse transcription quantitative polymerase chain reaction (qRT-PCR) assays revealed disturbed homeostasis in condylar cartilage with increased expressions of MMP13 and Adamts5 and decreased lubricin expression in Axin1-deficient chondrocytes. Less proliferative cells with increased hypertrophic and apoptotic activities were presented in the condylar cartilage of Axin1^Agc1ER KO mice. As a scaffolding protein, the deletion of Axin1 stimulated not only the β-catenin but also the fibroblast growth factor (FGF) signaling via extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) activation. The qRT-PCR results showed an increased expression of Fgfr1 in Axin1 KO cartilage. Overall, the deletion of Axin1 in condylar chondrocytes altered the β-catenin and FGF/ERK1/2 signaling pathways, thus cooperatively contribute to the cartilage degeneration.

FGF23 Regulates Wnt/β-Catenin Signaling-Mediated Osteoarthritis in Mice Overexpressing High-Molecular-Weight FGF2

Although humans with X-linked hypophosphatemia (XLH) and the Hyp mouse, a murine homolog of XLH, are known to develop degenerative joint disease, the exact mechanism that drives the osteoarthritis (OA) phenotype remains unclear. Mice that overexpress high-molecular-weight fibroblast growth factor (FGF) 2 isoforms (HMWTg mice) phenocopy both XLH and Hyp, including OA with increased FGF23 production in bone and serum. Because HMWTg cartilage also has increased FGF23 and there is cross-talk between FGF23-Wnt/β-catenin signaling, the purpose of this study was to determine if OA observed in HMWTg mice is due to FGF23-mediated canonical Wnt signaling in chondrocytes, given that both pathways are implicated in OA pathogenesis. HMWTg OA joints had decreased Dkk1, Sost, and Lrp6 expression with increased Wnt5a, Wnt7b, Lrp5, Axin2, phospho-GSK3β, Lef1, and nuclear β-catenin, as indicated by immunohistochemistry or quantitative PCR analysis. Chondrocytes from HMWTg mice had enhanced alcian blue and alkaline phosphatase staining as well as increased FGF23, Adamts5, Il-1β, Wnt7b, Wnt16, and Wisp1 gene expression and phospho-GSK3β protein expression as indicated by Western blot, compared with chondrocytes of vector control and chondrocytes from mice overexpressing the low-molecular-weight isoform, which were protected from OA. Canonical Wnt inhibitor treatment rescued some of those parameters in HMWTg chondrocytes, seemingly delaying the initially accelerated chondrogenic differentiation. FGF23 neutralizing antibody treatment was able to partly ameliorate OA abnormalities in subchondral bone and reduce degradative/hypertrophic chondrogenic marker expression in HMWTg joints in vivo. These results demonstrate that osteoarthropathy of HMWTg is at least partially due to FGF23-modulated Wnt/β-catenin signaling in chondrocytes.

[Resveratrol regulate the extracellular matrix expression via Wnt/β-catenin pathway in nucleus pulposus cells]

Objective

To investigate the regulatory effect of resveratrol (RES) on the extracellular matrix (ECM) expression of nucleus pulposus cells (NPC), and its relative molecular mechanism.

Methods

Ten patients receiving discectomy were collected, of which 5 patients were young with spinal burst fracture, classified as control group; the rest 5 patients were senile with lumbar disc herniation, classified as degenerative group. The nucleus pulposus tissue of 2 groups were collected, the in situexpression of β-catenin was detected by immunohistochemistry, and the protein expressions of collagen type Ⅱ and Aggrecan were detected by Western blot. The NPC were isolated and cultured from degenerative nucleus pulposus tissues. RES treated the third-passage NPC with (group B) or without IL-1β (group C), to further determine the protein expressions of collagen type Ⅱ and Aggrecan by Western blot, the unstimulated cells were set up as blank control group (group A). Moreover, NPC treated with small interfering RNA (siRNA) targeted silent SIRT1 or β-catenin were used to determine the protein and gene expressions of β-catenin and SIRT1 by Western blot and real-time fluorescence quantitative PCR. In addition, the third-passage NPC treated with complete medium (group 1), IL-1β (group 2), RES+IL-1β (group 3), and SIRT1-siRNA+RES+IL-1β (group 4) for 24 hours were used to detect the nuclear translocation of β-catenin by cell immunofluorescence staining. Finally, the third-passage NPC treated with complete medium (group Ⅰ), IL-1β (group Ⅱ), IL-1β+β-catenin-siRNA (group Ⅲ), IL-1β+RES (group Ⅳ), and IL-1β+RES+SIRT1-siRNA (group Ⅴ) for 24 hours were used to detect the protein expressions of collagen type Ⅱ and Aggrecan by Western blot.

Results

Immunohistochemical staining and Western blot detection showed that when compared with control group, the cell proportion of expression of β-catenin were significantly increased in degenerative group ( t=4.616, P=0.010); the protein expression of β-catenin was also significantly increased and the protein expressions of collagen type Ⅱ and Aggrecan were significantly decreased ( P<0.05). In cytology experiments, the protein expression of β-catenin in group B was significantly higher than that in groups A and C, and the protein expressions of collagen type Ⅱ and Aggrecan in group B were significantly lower than those in groups A and C ( P<0.05). After transfection of siRNA, the protein expressions of SIRT1 and β-catenin significantly decreased ( P<0.05). The results of cell immunofluorescence staining further confirmed that when compared with group 3, after the SIRT1 was silenced by siRNA in group 4, the attenuated nuclear translocation of β-catenin by RES treatment was aggravated. Western blot results showed that the protein expressions of collagen type Ⅱ and Aggrecan in group Ⅱ were significantly lower than those in group Ⅰ( P<0.05); after transfection of β-catenin-siRNA in group Ⅲ, the degradation of ECM by IL-1β was obviously inhibited, the protein expressions of collagen type Ⅱ and Aggrecan were significantly increased when compared with group Ⅱ ( P<0.05); after transfection of SIRT1-siRNA in group Ⅴ, the protective effect of RES on the degradation of ECM was inhibited, the protein expressions of collagen type Ⅱ and Aggrecan were significantly decreased when compared with group Ⅳ ( P<0.05).

Conclusion

RES regulates the ECM expression of NPC via Wnt/β-catenin signaling pathway, which provide a new idea for intervertebral disc degeneration disease treatment.

Clinical and next-generation sequencing findings in a Chinese family exhibiting severe familial exudative vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary retinal disorder characterized by the premature arrest of vascularization in the peripheral retina. The aim of the present study was to characterize the clinical presentations of a Chinese family affected by bilateral severe FEVR, and to identify the underlying genetic variations. One family that presented with bilateral FEVR was recruited for this study. Comprehensive ophthalmic examinations, including best‑corrected visual acuity, slit‑lamp examination, fundus photography, fundus fluorescein angiography imaging and electroretinogram were performed. Genomic DNA was extracted from leukocytes of the peripheral blood collected from the affected and unaffected family members, as well as 200 unrelated control subjects from the same population. Next‑generation sequencing of the candidate genes associated with ocular diseases was performed, and the identified mutations were validated by conventional polymerase chain reaction‑based sequencing. The functional effects of the mutations were analyzed by polymorphism phenotyping (PolyPhen) and sorting intolerant from tolerant (SIFT). One heterozygous ATP binding cassette subfamily A member 4 (ABCA4) c.5693G>A (p.R1898H) mutation in exon 40 and one heterozygous LDL receptor related protein 5 (LRP5) c.260T>G (p.I87S) mutation in exon 2 were identified in this family. To the best of our knowledge, the ABCA4 c.5693G>A (p.R1898H) mutation has not been reported in FEVR, and the LRP5 c.260T>G (p.I87S) mutation is a novel mutation. PolyPhen and SIFT predicted that the amino acid substitution R1898H in protein ABCA4 is benign, whereas the amino acid substitution I87S in protein LRP5 is damaging. A single nucleotide polymorphism c.266A>G (p.Q89R, rs41494349) was identified in exon 2 of LRP5. These findings expand the mutation spectrums of ABCA4 and LRP5, and will be valuable for genetic counseling and development of therapeutic interventions for patients with FEVR.

ARQ 087 inhibits FGFR signaling and rescues aberrant cell proliferation and differentiation in experimental models of craniosynostoses and chondrodysplasias caused by activating mutations in FGFR1, FGFR2 and FGFR3

Tyrosine kinase inhibitors are being developed for therapy of malignancies caused by oncogenic FGFR signaling but little is known about their effect in congenital chondrodysplasias or craniosynostoses that associate with activating FGFR mutations. Here, we investigated the effects of novel FGFR inhibitor, ARQ 087, in experimental models of aberrant FGFR3 signaling in cartilage. In cultured chondrocytes, ARQ 087 efficiently rescued all major effects of pathological FGFR3 activation, i.e. inhibition of chondrocyte proliferation, loss of extracellular matrix and induction of premature senescence. In ex vivo tibia organ cultures, ARQ 087 restored normal growth plate architecture and eliminated the suppressing FGFR3 effect on chondrocyte hypertrophic differentiation, suggesting that it targets the FGFR3 pathway specifically, i.e. without interference with other pro-growth pathways. Moreover, ARQ 087 inhibited activity of FGFR1 and FGFR2 mutants associated with Pfeiffer, Apert and Beare-Stevenson craniosynostoses, and rescued FGFR-driven excessive osteogenic differentiation in mouse mesenchymal micromass cultures or in ex vivo calvarial organ cultures. Our data warrant further development of ARQ 087 for clinical use in skeletal disorders caused by activating FGFR mutations.

Inducible Activation of FGFR2 in Adult Mice Promotes Bone Formation After Bone Marrow Ablation

Apert syndrome is one of the most severe craniosynostoses, resulting from gain-of-function mutations in fibroblast growth factor receptor 2 (FGFR2). Previous studies have shown that gain-of-function mutations of FGFR2 (S252W or P253R) cause skull malformation of human Apert syndrome by affecting both chondrogenesis and osteogenesis, underscoring the key role of FGFR2 in bone development. However, the effects of FGFR2 on bone formation at the adult stage have not been fully investigated. To investigate the role of FGFR2 in bone formation, we generated mice with tamoxifen-inducible expression of mutant FGFR2 (P253R) at the adult stage. Mechanical bone marrow ablation (BMX) was performed in both wild-type and Fgfr2 mutant (MT) mice. Changes in newly formed trabecular bone were assessed by micro-computed tomography and bone histomorphometry. We found that MT mice exhibited increased trabecular bone formation and decreased bone resorption after BMX accompanied with a remarkable increase in bone marrow stromal cell recruitment and proliferation, osteoblast proliferation and differentiation, and enhanced Wnt/β-catenin activity. Furthermore, pharmacologically inhibiting Wnt/β-catenin signaling can partially reverse the increased trabecular bone formation and decreased bone resorption in MT mice after BMX. Our data demonstrate that gain-of-function mutation in FGFR2 exerts a Wnt/β-catenin-dependent anabolic effect on trabecular bone by promoting bone formation and inhibiting bone resorption at the adult stage. © 2017 American Society for Bone and Mineral Research.

Dephosphorylation is the mechanism of fibroblast growth factor inhibition of guanylyl cyclase-B

Activating mutations in fibroblast growth factor receptor 3 (FGFR3) and inactivating mutations of guanylyl cyclase-B (GC-B, also called NPRB or NPR2) cause dwarfism. FGF exposure inhibits GC-B activity in a chondrocyte cell line, but the mechanism of the inactivation is not known. Here, we report that FGF exposure causes dephosphorylation of GC-B in rat chondrosarcoma cells, which correlates with a rapid, potent and reversible inhibition of C-type natriuretic peptide-dependent activation of GC-B. Cells expressing a phosphomimetic mutant of GC-B that cannot be inactivated by dephosphorylation because it contains glutamate substitutions for all known phosphorylation sites showed no decrease in GC-B activity in response to FGF. We conclude that FGF rapidly inactivates GC-B by a reversible dephosphorylation mechanism, which may contribute to the signaling network by which activated FGFR3 causes dwarfism.

Statins do not inhibit the FGFR signaling in chondrocytes

OBJECTIVE

Statins are widely used drugs for cholesterol lowering, which were recently found to counteract the effects of aberrant fibroblast growth factor receptor (FGFR3) signaling in cell and animal models of FGFR3-related chondrodysplasia. This opened an intriguing therapeutic possibility for human dwarfing conditions caused by gain-of-function mutations in FGFR3, although the mechanism of statin action on FGFR3 remains unclear. Here, we determine the effect of statins on FGFR signaling in chondrocytes.

DESIGN

Cultured chondrocyte cell lines, mouse embryonic tibia cultures and limb bud micromasses were treated with FGF2 to activate FGFR signaling. The effects of atorvastatin, fluvastatin, lovastatin and pravastatin on FGFR3 protein stability and on FGFR-mediated chondrocyte growth-arrest, loss of extracellular matrix (ECM), induction of premature senescence and hypertrophic differentiation were evaluated.

RESULTS

Statins did not alter the level of FGFR3 protein expression nor produce any effect on FGFR-mediated inhibition of chondrocyte proliferation and hypertrophic differentiation in cultured chondrocyte cell lines, mouse tibia cultures or limb bud micromasses.

CONCLUSION

We conclude that statins do not inhibit the FGFR signaling in chondrocytes. Therefore the statin-mediated rescue of FGFR3-related chondrodysplasia, described before, is likely not intrinsic to the growth plate cartilage.

A Novel Role for the BMP Antagonist Noggin in Sensitizing Cells to Non-canonical Wnt-5a/Ror2/Disheveled Pathway Activation

Mammalian limb development is driven by the integrative input from several signaling pathways; a failure to receive or a misinterpretation of these signals results in skeletal defects. The brachydactylies, a group of overlapping inherited human hand malformation syndromes, are mainly caused by mutations in BMP signaling pathway components. Two closely related forms, Brachydactyly type B2 (BDB2) and BDB1 are caused by mutations in the BMP antagonist Noggin (NOG) and the atypical receptor tyrosine kinase ROR2 that acts as a receptor in the non-canonical Wnt pathway. Genetic analysis of Nog and Ror2 functional interaction via crossing Noggin and Ror2 mutant mice revealed a widening of skeletal elements in compound but not in any of the single mutants, thus indicating genetic interaction. Since ROR2 is a non-canonical Wnt co-receptor specific for Wnt-5a we speculated that this phenotype might be a result of deregulated Wnt-5a signaling activation, which is known to be essential for limb skeletal elements growth and patterning. We show that Noggin potentiates activation of the Wnt-5a-Ror2-Disheveled (Dvl) pathway in mouse embryonic fibroblast (MEF) cells in a Ror2-dependent fashion. Rat chondrosarcoma chondrocytes (RCS), however, are not able to respond to Noggin in this fashion unless growth arrest is induced by FGF2. In summary, our data demonstrate genetic interaction between Noggin and Ror2 and show that Noggin can sensitize cells to Wnt-5a/Ror2-mediated non-canonical Wnt signaling, a feature that in cartilage may depend on the presence of active FGF signaling. These findings indicate an unappreciated function of Noggin that will help to understand BMP and Wnt/PCP signaling pathway interactions.

One reporter for in-cell activity profiling of majority of protein kinase oncogenes

In-cell profiling enables the evaluation of receptor tyrosine activity in a complex environment of regulatory networks that affect signal initiation, propagation and feedback. We used FGF-receptor signaling to identify EGR1 as a locus that strongly responds to the activation of a majority of the recognized protein kinase oncogenes, including 30 receptor tyrosine kinases and 154 of their disease-associated mutants. The EGR1 promoter was engineered to enhance trans-activation capacity and optimized for simple screening assays with luciferase or fluorescent reporters. The efficacy of the developed, fully synthetic reporters was demonstrated by the identification of novel targets for two clinically used tyrosine kinase inhibitors, nilotinib and osimertinib. A universal reporter system for in-cell protein kinase profiling will facilitate repurposing of existing anti-cancer drugs and identification of novel inhibitors in high-throughput screening studies.

DOI:http://dx.doi.org/10.7554/eLife.21536.001

Lung development requires an active ERK/MAPK pathway in the lung mesenchyme

BACKGROUND

Reciprocal epithelial-mesenchymal communications are critical throughout lung development, dictating branching morphogenesis and cell specification. Numerous signaling molecules are involved in these interactions, but the way epithelial-mesenchymal crosstalk is coordinated remains unclear. The ERK/MAPK pathway transduces several important signals in lung formation. Epithelial inactivation of both Mek genes, encoding ERK/MAPK kinases, causes lung agenesis and death. Conversely, Mek mutation in mesenchyme results in lung hypoplasia, trachea cartilage malformations, kyphosis, omphalocele, and death. Considering the negative impact of kyphosis and omphalocele on intrathoracic space and, consequently, on lung growth, the exact role of ERK/MAPK pathway in lung mesenchyme remains unresolved.

RESULTS

To address the role of the ERK/MAPK pathway in lung mesenchyme in absence of kyphosis and omphalocele, we used the Tbx4^Cre deleter mouse line, which acts specifically in lung mesenchyme. These Mek mutants did not develop kyphosis and omphalocele but they presented lung hypoplasia, tracheal defects, and neonatal death. Tracheal cartilage anomalies suggested a role for the ERK/MAPK pathway in the control of chondrocyte hypertrophy. Moreover, expression data indicated potential interactions between the ERK/MAPK and canonical Wnt pathways during lung formation.

CONCLUSIONS

Lung development necessitates a functional ERK/MAPK pathway in the lung mesenchymal layer in order to coordinate efficient epithelial-mesenchymal interactions. Developmental Dynamics 246:72-82, 2017. © 2016 Wiley Periodicals, Inc.

Wnt/β-catenin signaling pathway activation is required for proliferation of chicken primordial germ cells in vitro

Here, we investigated the role of the Wnt/β-catenin signaling pathway in chicken primordial germ cells (PGCs) in vitro. We confirmed the expression of Wnt signaling pathway-related genes and the localization of β-catenin in the nucleus, revealing that this pathway is potentially activated in chicken PGCs. Then, using the single-cell pick-up assay, we examined the proliferative capacity of cultured PGCs in response to Wnt ligands, a β-catenin-mediated Wnt signaling activator (6-bromoindirubin-3′-oxime [BIO]) or inhibitor (JW74), in the presence or absence of basic fibroblast growth factor (bFGF). WNT1, WNT3A, and BIO promoted the proliferation of chicken PGCs similarly to bFGF, whereas JW74 inhibited this proliferation. Meanwhile, such treatments in combination with bFGF did not show a synergistic effect. bFGF treatment could not rescue PGC proliferation in the presence of JW74. In addition, we confirmed the translocation of β-catenin into the nucleus by the addition of bFGF after JW74 treatment. These results indicate that there is signaling crosstalk between FGF and Wnt, and that β-catenin acts on PGC proliferation downstream of bFGF. In conclusion, our study suggests that Wnt signaling enhances the proliferation of chicken PGCs via the stabilization of β-catenin and activation of its downstream genes.

Effect of the achondroplasia mutation on FGFR3 dimerization and FGFR3 structural response to fgf1 and fgf2: A quantitative FRET study in osmotically derived plasma membrane vesicles

The G380R mutation in the transmembrane domain of FGFR3 is a germline mutation responsible for most cases of Achondroplasia, a common form of human dwarfism. Here we use quantitative Fӧster Resonance Energy Transfer (FRET) and osmotically derived plasma membrane vesicles to study the effect of the achondroplasia mutation on the early stages of FGFR3 signaling in response to the ligands fgf1 and fgf2. Using a methodology that allows us to capture structural changes on the cytoplasmic side of the membrane in response to ligand binding to the extracellular domain of FGFR3, we observe no measurable effects of the G380R mutation on FGFR3 ligand-bound dimer configurations. Instead, the most notable effect of the achondroplasia mutation is increased propensity for FGFR3 dimerization in the absence of ligand. This work reveals new information about the molecular events that underlie the achondroplasia phenotype, and highlights differences in FGFR3 activation due to different single amino-acid pathogenic mutations.

The pathogenesis of congenital radial head dislocation/subluxation

The pathogenesis of congenital radial head dislocation/subluxation is unknown and has not been previously investigated. In this review, we explore the pathogenesis and define five different primary insults: collagen abnormalities, abnormal endochondral ossification of the developing growth plate, abnormalities of forearm ossification outside the growth plate, disproportionate growth of the radius and ulna, and altered HOX D expression/activity. Finally, the clinical relevance of our review is discussed.

Multikinase activity of fibroblast growth factor receptor (FGFR) inhibitors SU5402, PD173074, AZD1480, AZD4547 and BGJ398 compromises the use of small chemicals targeting FGFR catalytic activity for therapy of short-stature syndromes

Activating mutations in the fibroblast growth factor receptor 3 (FGFR3) cause the most common genetic form of human dwarfism, achondroplasia (ACH). Small chemical inhibitors of FGFR tyrosine kinase activity are considered to be viable option for treating ACH, but little experimental evidence supports this claim. We evaluated five FGFR tyrosine kinase inhibitors (TKIs) (SU5402, PD173074, AZD1480, AZD4547 and BGJ398) for their activity against FGFR signaling in chondrocytes. All five TKIs strongly inhibited FGFR activation in cultured chondrocytes and limb rudiment cultures, completely relieving FGFR-mediated inhibition of chondrocyte proliferation and maturation. In contrast, TKI treatment of newborn mice did not improve skeletal growth and had lethal toxic effects on the liver, lungs and kidneys. In cell-free kinase assays as well as in vitro and in vivo cell assays, none of the tested TKIs demonstrated selectivity for FGFR3 over three other FGFR tyrosine kinases. In addition, the TKIs exhibited significant off-target activity when screened against a panel of 14 unrelated tyrosine kinases. This was most extensive in SU5402 and AZD1480, which inhibited DDR2, IGF1R, FLT3, TRKA, FLT4, ABL and JAK3 with efficiencies similar to or greater than those for FGFR. Low target specificity and toxicity of FGFR TKIs thus compromise their use for treatment of ACH. Conceptually, different avenues of therapeutic FGFR3 targeting should be investigated.

Fibroblast growth factor signaling in skeletal development and disease

Fibroblast growth factor (FGF) signaling pathways are essential regulators of vertebrate skeletal development. FGF signaling regulates development of the limb bud and formation of the mesenchymal condensation and has key roles in regulating chondrogenesis, osteogenesis, and bone and mineral homeostasis. This review updates our review on FGFs in skeletal development published in Genes & Development in 2002, examines progress made on understanding the functions of the FGF signaling pathway during critical stages of skeletogenesis, and explores the mechanisms by which mutations in FGF signaling molecules cause skeletal malformations in humans. Links between FGF signaling pathways and other interacting pathways that are critical for skeletal development and could be exploited to treat genetic diseases and repair bone are also explored.