Fibroblast growth factor (FGF) signaling in development and skeletal diseases

lncRNA Rmst acts as an important mediator of BMP9-induced osteogenic differentiation of mesenchymal stem cells (MSCs) by antagonizing Notch-targeting microRNAs

Understanding the bone and musculoskeletal system is essential to maintain the health and quality of life of our aging society. Mesenchymal stem cells (MSCs) can undergo self-renewal and differentiate into multiple tissue types including bone. We demonstrated that BMP9 is the most potent osteogenic factors although molecular mechanism underlying BMP9 action is not fully understood. Long noncoding RNAs (lncRNAs) play important regulatory roles in many physiological and/or pathologic processes. Here, we investigated the role of lncRNA Rmst in BMP9-induced osteogenic differentiation of MSCs. We found that Rmst was induced by BMP9 through Smad signaling in MSCs. Rmst knockdown diminished BMP9-induced osteogenic, chondrogenic and adipogenic differentiation in vitro, and attenuated BMP9-induced ectopic bone formation. Silencing Rmst decreased the expression of Notch receptors and ligands. Bioinformatic analysis predicted Rmst could directly bind to eight Notch-targeting miRNAs, six of which were downregulated by BMP9. Silencing Rmst restored the expression of four microRNAs (miRNAs). Furthermore, an activating Notch mutant NICD1 effectively rescued the decreased ALP activity caused by Rmst silencing. Collectively, our results strongly suggest that the Rmst-miRNA-Notch regulatory axis may play an important role in mediating BMP9-induced osteogenic differentiation of MSCs.

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.

Clinical application of injectable growth factor for bone regeneration: a systematic review

Bone regeneration has been the ultimate goal in the field of bone and joint medicine and has been evaluated through various basic research studies to date. Translational research of regenerative medicine has focused on three primary approaches, which are expected to increase in popularity: cell therapy, proteins, and artificial materials. Among these, the local injection of a gelatin hydrogel impregnated with the protein fibroblast growth factor (FGF)-2 is a biomaterial technique that has been developed in Japan. We have previously reported the efficacy of gelatin hydrogel containing injectable FGF-2 for the regenerative treatment of osteonecrosis of the femoral head. Injectable growth factors will probably be developed in the future and gain popularity as a medical approach in various fields as well as orthopedics. Several clinical trials have already been conducted and have focused on this technique, reporting its efficacy and safety. To date, reports of the clinical application of FGF-2 in revascularization for critical limb ischemia, treatment of periodontal disease, early bone union for lower limb fracture and knee osteotomy, and bone regeneration for osteonecrosis of the femoral head have been based on basic research conducted in Japan. In the present report, we present an extensive review of clinical applications using injectable growth factors and discuss the associated efficacy and safety of their administration.

Deleting Suppressor of Cytokine Signaling-3 in chondrocytes reduces bone growth by disrupting mitogen-activated protein kinase signaling

OBJECTIVE

To investigate the impact of deleting Suppressor of Cytokine Signaling (SOCS)-3 (SOCS3) in chondrocytes during murine skeletal development.

METHOD

Mice with a conditional Socs3 allele (Socs3^fl/fl) were crossed with a transgenic mouse expressing Cre recombinase under the control of the type II collagen promoter (Col2a1) to generate Socs3^Δ/Δcol2 mice. Skeletal growth was analyzed over the lifespan of Socs3^Δ/Δcol2 mice and controls by detailed histomorphology. Bone size and cortical bone development was evaluated by micro-computed tomography (micro-CT). Growth plate (GP) zone width, chondrocyte proliferation and apoptosis were assessed by immunofluorescence staining for Ki67 and TUNEL. Fibroblast growth factor receptor-3 (FGFR3) signaling in the GP was assessed by immunohistochemistry, while the effect of SOCS3 overexpression on FGFR3-driven pMAPK signaling in HEK293T cells was evaluated by Western blot.

RESULTS

Socs3^Δ/Δcol2 mice of both sexes were consistently smaller compared to littermate controls throughout life. This phenotype was due to reduced long bone size, poor cortical bone development, reduced Ki67⁺ proliferative chondrocytes and decreased proliferative zone (PZ) width in the GP. Expression of pMAPK, but not pSTAT3, was increased in the GPs of Socs3^Δ/Δcol2 mice relative to littermate controls. Overexpression of FGFR3 in HEK293T cells increased Fibroblast Growth Factor 18 (FGF18)-dependent Mitogen-activated protein kinase (MAPK) phosphorylation, while concomitant expression of SOCS3 reduced FGFR3 expression and abrogated MAPK signaling.

CONCLUSION

Our results suggest a potential role for SOCS3 in GP chondrocyte proliferation by regulating FGFR3-dependent MAPK signaling in response to FGF18.

Fgf8a mutation affects craniofacial development and skeletal gene expression in zebrafish larvae

Craniofacial development is tightly regulated and therefore highly vulnerable to disturbance by genetic and environmental factors. Fibroblast growth factors (FGFs) direct migration, proliferation and survival of cranial neural crest cells (CNCCs) forming the human face. In this study, we analyzed bone and cartilage formation in the head of five dpf fgf8a^ti282 zebrafish larvae and assessed gene expression levels for 11 genes involved in these processes. In addition, in situ hybridization was performed on 8 and 24 hours post fertilization (hpf) larvae (fgf8a, dlx2a, runx2a, col2a1a). A significant size reduction of eight out of nine craniofacial cartilage structures was found in homozygous mutant (6–36%, P<0.01) and heterozygous (7–24%, P<0.01) larvae. Also, nine mineralized structures were not observed in all or part of the homozygous (0–71%, P<0.0001) and heterozygous (33–100%, P<0.0001) larvae. In homozygote mutants, runx2a and sp7 expression was upregulated compared to wild type, presumably to compensate for the reduced bone formation. Decreased col9a1b expression may compromise cartilage formation. Upregulated dlx2a in homozygotes indicates impaired CNCC function. Dlx2a expression was reduced in the first and second stream of CNCCs in homozygous mutants at 24 hpf, as shown by in situ hybridization. This indicates an impairment of CNCC migration and survival by fgf8 mutation.

Summary: A function-blocking mutation in fgf8a causes craniofacial malformations in zebrafish larvae due to impaired cranial neural crest cell migration and survival.

The role of the fibroblast growth factor family in bone-related diseases

Fibroblast growth factor (FGF) family members are important regulators of cell growth, proliferation, differentiation, and regeneration. The abnormal expression of certain FGF family members can cause skeletal diseases, including achondroplasia, craniosynostosis syndrome, osteoarthritis, and Kashin-Beck disease. Accumulating evidence shows that FGFs play a crucial role in the growth and proliferation of bone and in the pathogenesis of certain bone-related diseases. Here, we review the involvement of FGFs in bone-related processes and diseases; FGF1 in the differentiation of human bone marrow mesenchymal stem cells and fracture repair; FGF2, FGF9, and FGF18 in osteoarthritis; FGF6 in bone and muscle injury; FGF8 in osteoarthritis and Kashin-Beck disease; and FGF21 and FGF23 on bone regulation. These findings indicate that FGFs are targets for novel therapeutic interventions for bone-related diseases.

Regulation of Runx2 by MicroRNAs in osteoblast differentiation

Bone is one of the most dynamic organs in the body that continuously undergoes remodeling through bone formation and resorption. A cascade of molecules and pathways results in the osteoblast differentiation that is attributed to osteogenesis, or bone formation. The process of osteogenesis is achieved through participation of the Wnt pathway, FGFs, BMPs/TGF-β, and transcription factors such as Runx2 and Osx. The activity and function of the master transcription factor, Runx2, is of utmost significance as it can induce the function of osteoblast differentiation markers. A number of microRNAs [miRNAs] have been recently identified in the regulation of Runx2 expression/activity, thus affecting the process of osteogenesis. miRNAs that target Runx2 corepressors favor osteogenesis, while miRNAs that target Runx2 coactivators inhibit osteogenesis. In this review, we focus on the regulation of Runx2 by miRNAs in osteoblast differentiation and their potential for treating bone and bone-related diseases.

PIN1 is a new therapeutic target of craniosynostosis

Gain-of-function mutations in fibroblast growth factor receptors (FGFRs) cause congenital skeletal anomalies, including craniosynostosis (CS), which is characterized by the premature closure of craniofacial sutures. Apert syndrome (AS) is one of the severest forms of CS, and the only treatment is surgical expansion of prematurely fused sutures in infants. Previously, we demonstrated that the prolyl isomerase peptidyl-prolyl cis-trans isomerase interacting 1 (PIN1) plays a critical role in mediating FGFR signaling and that Pin1+/- mice exhibit delayed closure of cranial sutures. In this study, using both genetic and pharmacological approaches, we tested whether PIN1 modulation could be used as a therapeutic regimen against AS. In the genetic approach, we crossbred Fgfr2S252W/+, a mouse model of AS, and Pin1+/- mice. Downregulation of Pin1 gene dosage attenuated premature cranial suture closure and other phenotypes of AS in Fgfr2S252W/+ mutant mice. In the pharmacological approach, we intraperitoneally administered juglone, a PIN1 enzyme inhibitor, to pregnant Fgfr2S252W/+ mutant mice and found that this treatment successfully interrupted fetal development of AS phenotypes. Primary cultured osteoblasts from Fgfr2S252W/+ mutant mice expressed high levels of FGFR2 downstream target genes, but this phenotype was attenuated by PIN1 inhibition. Post-translational stabilization and activation of Runt-related transcription factor 2 (RUNX2) in Fgfr2S252W/+ osteoblasts were also attenuated by PIN1 inhibition. Based on these observations, we conclude that PIN1 enzyme activity is important for FGFR2-induced RUNX2 activation and craniofacial suture morphogenesis. Moreover, these findings highlight that juglone or other PIN1 inhibitors represent viable alternatives to surgical intervention for treatment of CS and other hyperostotic diseases.

Transcriptomic landscape regulated by the 14 types of bone morphogenetic proteins (BMPs) in lineage commitment and differentiation of mesenchymal stem cells (MSCs)

Mesenchymal stem cells (MSCs) are ubiquitously-existing multipotent progenitors that can self-renew and differentiate into multiple lineages including osteocytes, chondrocytes, adipocytes, tenocytes and myocytes. MSCs represent one of the most commonly-used adult progenitors and serve as excellent progenitor cell models for investigating lineage-specific differentiation regulated by various cellular signaling pathways, such as bone morphogenetic proteins (BMPs). As members of TGFβ superfamily, BMPs play diverse and important roles in development and adult tissues. At least 14 BMPs have been identified in mammals. Different BMPs exert distinct but overlapping biological functions. Through a comprehensive analysis of 14 BMPs in MSCs, we demonstrated that BMP9 is one of the most potent BMPs in inducing osteogenic differentiation of MSCs. Nonetheless, a global mechanistic view of BMP signaling in regulating the proliferation and differentiation of MSCs remains to be fully elucidated. Here, we conducted a comprehensive transcriptomic profiling in the MSCs stimulated by 14 types of BMPs. Hierarchical clustering analysis classifies 14 BMPs into three subclusters: an osteo/chondrogenic/adipogenic cluster, a tenogenic cluster, and BMP3 cluster. We also demonstrate that six BMPs (e.g., BMP2, BMP3, BMP4, BMP7, BMP8, and BMP9) can induce I-Smads effectively, while BMP2, BMP3, BMP4, BMP7, and BMP11 up-regulate Smad-independent MAP kinase pathway. Furthermore, we show that many BMPs can upregulate the expression of the signal mediators of Wnt, Notch and PI3K/AKT/mTOR pathways. While the reported transcriptomic changes need to be further validated, our expression profiling represents the first-of-its-kind to interrogate a comprehensive transcriptomic landscape regulated by the 14 types of BMPs in MSCs.

The laminin binding α3 and α6 integrins cooperate to promote epithelial cell adhesion and growth

Integrins, the major receptors for cell-extracellular matrix (ECM) interactions, regulate multiple cell biological processes including adhesion, migration, proliferation and growth factor-dependent signaling. The principal laminin (LM) binding integrins α3β1, α6β1 and α6β4 are usually co-expressed in cells and bind to multiple laminins with different affinities making it difficult to define their specific function. In this study, we generated kidney epithelial collecting duct (CD) cells that lack both the α3 and α6 integrin subunits. This deletion impaired cell adhesion and migration to LM-332 and LM-511 more than deleting α3 or α6 alone. Cell adhesion mediated by both α3β1 and α6 integrins was PI3K independent, but required K63-linked polyubiquitination of Akt by the ubiquitin-modifying enzyme TRAF6. Moreover, we provide evidence that glial-derived neurotrophic factor (GDNF) and fibroblast growth factor 10 (FGF10)- mediated cell signaling, spreading and proliferation were severely compromised in double integrin α3/α6- but not single α3- or α6-null CD cells. Interestingly, these growth factor-dependent cell functions required both PI3K- and TRAF6-dependent Akt activation. These data suggest that expression of the integrin α3 or α6 subunit is sufficient to mediate GDNF- and FGF10-dependent spreading, proliferation and signaling on LM-511. Thus, our study shows that α3 and α6 containing integrins promote distinct functions and signaling by CD cells on laminin substrata.

A pH-Triggered, Self-Assembled, and Bioprintable Hybrid Hydrogel Scaffold for Mesenchymal Stem Cell Based Bone Tissue Engineering

Effective bone tissue engineering can restore bone and skeletal functions that are impaired by traumas and/or certain medical conditions. Bone is a complex tissue and functions through orchestrated interactions between cells, biomechanical forces, and biofactors. To identify ideal scaffold materials for effective mesenchymal stem cell (MSC)-based bone tissue regeneration, here we develop and characterize a composite nanoparticle hydrogel by combining carboxymethyl chitosan (CMCh) and amorphous calcium phosphate (ACP) (designated as CMCh-ACP hydrogel). We demonstrate that the CMCh-ACP hydrogel is readily prepared by incorporating glucono δ-lactone (GDL) into an aqueous dispersion or rehydrating the acidic freeze-dried nanoparticles in a pH-triggered controlled-assembly fashion. The CMCh-ACP hydrogel exhibits excellent biocompatibility and effectively supports MSC proliferation and cell adhesion. Moreover, while augmenting BMP9-induced osteogenic differentiation, the CMCh-ACP hydrogel itself is osteoinductive and induces the expression of osteoblastic regulators and bone markers in MSCs in vitro. The CMCh-ACP scaffold markedly enhances the efficiency and maturity of BMP9-induced bone formation in vivo, while suppressing bone resorption occurred in long-term ectopic osteogenesis. Thus, these results suggest that the pH-responsive self-assembled CMCh-ACP injectable and bioprintable hydrogel may be further exploited as a novel scaffold for osteoprogenitor-cell-based bone tissue regeneration.

FGF signaling deregulation is associated with early developmental skeletal defects in animal models for mucopolysaccharidosis type II (MPSII)

Skeletal abnormalities represent a major clinical burden in patients affected by the lysosomal storage disorder mucopolysaccharidosis type II (MPSII, OMIM #309900). While extensive research has emphasized the detrimental role of stored glycosaminoglycans (GAGs) in the bone marrow (BM), a limited understanding of primary cellular mechanisms underlying bone defects in MPSII has hampered the development of bone-targeted therapeutic strategies beyond enzyme replacement therapy (ERT). We here investigated the involvement of key signaling pathways related to the loss of iduronate-2-sulfatase activity in two different MPSII animal models, D. rerio and M. musculus. We found that FGF pathway activity is impaired during early stages of bone development in IDS knockout mice and in a newly generated Ids mutant fish. In both models the FGF signaling deregulation anticipated a slow but progressive defect in bone differentiation, regardless of any extensive GAGs storage. We also show that MPSII patient fibroblasts harboring different mutations spanning the IDS gene exhibit perturbed FGF signaling-related markers expression. Our work opens a new venue to discover possible druggable novel key targets in MPSII.

A novel dominant-negative FGFR1 variant causes Hartsfield syndrome by deregulating RAS/ERK1/2 pathway

Hartsfield syndrome (HS) is an ultrarare developmental disorder mainly featuring holoprosencephaly and ectrodactyly. It is caused by heterozygous or biallelic variants in FGFR1. Recently, a dominant-negative effect was suggested for FGFR1 variants associated with HS. Here, exome sequencing analysis in a 12-year-old boy with HS disclosed a novel de novo heterozygous variant c.1934C>T in FGFR1 predicted to cause the p.(Ala645Val) amino-acid substitution. In order to evaluate whether the variant, changing a highly conserved residue of the kinase domain, affects FGFR1 function, biochemical studies were employed. We measured the FGFR1 receptor activity in FGF2-treated cell lines exogenously expressing wild-type or Ala645Val FGFR1 by monitoring the activation status of FGF2/FGFR1 downstream pathways. Our analysis highlighted that RAS/ERK1/2 signaling was significantly perturbed in cells expressing mutated FGFR1, in comparison with control cells. We also provided preliminary evidence showing a modulation of the autophagic process in cells expressing mutated FGFR1. This study expands the FGFR1 mutational spectrum associated with HS, provides functional evidence further supporting a dominant-negative effect of this category of FGFR1 variants and offers initial insights on dysregulation of autophagy in HS.

Signaling Mechanisms Underlying Genetic Pathophysiology of Craniosynostosis

Craniosynostosis, is the premature fusion of one or more cranial sutures which is the second most common cranial facial anomalies. The premature cranial sutures leads to deformity of skull shape and restricts the growth of brain, which might elicit severe neurologic damage. Craniosynostosis exhibit close correlations with a varieties of syndromes. During the past two decades, as the appliance of high throughput DNA sequencing techniques, steady progresses has been made in identifying gene mutations in both syndromic and nonsyndromic cases, which allow researchers to better understanding the genetic roles in the development of cranial vault. As the enrichment of known mutations involved in the pathogenic of premature sutures fusion, multiple signaling pathways have been investigated to dissect the underlying mechanisms beneath the disease. In addition to genetic etiology, environment factors, especially mechanics, have also been proposed to have vital roles during the pathophysiological of craniosynostosis. However, the influence of mechanics factors in the cranial development remains largely unknown. In this review, we present a brief overview of the updated genetic mutations and environmental factors identified in both syndromic and nonsyndromic craniosynostosis. Furthermore, potential molecular signaling pathways and its relations have been described.

Identification of a novel mutation of FGFR3 gene in a large Chinese pedigree with hypochondroplasia by next-generation sequencing: A case report and brief literature review

RATIONALE

Hypochondroplasia (HCH) is the mildest form of chondrodysplasia characterized by disproportionate short stature, short extremities, and variable lumbar lordosis. It is caused by mutations in fibroblast growth factor receptor 3 (FGFR3) gene. Up to date, at least thirty mutations of FGFR3 gene have been found to be related to HCH. However, mutational screening of the FGFR3 gene is still far from completeness. Identification of more mutations is particularly important in diagnosis of HCH and will gain more insights into the molecular basis for the pathogenesis of HCH.

PATIENT CONCERNS

A large Chinese family consisting of 53 affected individuals with HCH phenotypes was examined.

DIAGNOSES

A novel missense mutation, c.1052C>T, in FGFR3 gene was identified in a large Chinese family with HCH. On the basis of this finding and clinical manifestations, the final diagnosis of HCH was made.

INTERVENTIONS

Next-generation sequencing (NGS) of DNA samples was performed to detect the mutation in the chondrodysplasia-related genes on the proband and her parents, which was confirmed by Sanger sequencing in the proband and most of other living affected family members.

OUTCOMES

A novel missense mutation, c.1052C>T, in the extracellular, ligand-binding domain of FGFR3 was identified in a large Chinese family with HCH. This heterozygous mutation results in substitution of serine for phenylalanine at amino acid 351 (p.S351F) and co-segregates with the phenotype in this family. Molecular docking analysis reveals that this unique FGFR3 mutation results in an enhancement of ligand-binding affinity between FGFR3 and its main ligand, fibroblast growth factor 9.

LESSONS

This novel mutation is the first mutation displaying an increase in ligand-binding affinity, therefore it may serve as a model to investigate ligand-dependent activity of FGF-FGFR complex. Our data also expanded the mutation spectrum of FGFR3 gene and facilitated clinic diagnosis and genetic counseling for this family with HCH.

Structure, activation and dysregulation of fibroblast growth factor receptor kinases: perspectives for clinical targeting

The receptor tyrosine kinase family of fibroblast growth factor receptors (FGFRs) play crucial roles in embryonic development, metabolism, tissue homeostasis and wound repair via stimulation of intracellular signalling cascades. As a consequence of FGFRs' influence on cell growth, proliferation and differentiation, FGFR signalling is frequently dysregulated in a host of human cancers, variously by means of overexpression, somatic point mutations and gene fusion events. Dysregulation of FGFRs is also the underlying cause of many developmental dysplasias such as hypochondroplasia and achondroplasia. Accordingly, FGFRs are attractive pharmaceutical targets, and multiple clinical trials are in progress for the treatment of various FGFR aberrations. To effectively target dysregulated receptors, a structural and mechanistic understanding of FGFR activation and regulation is required. Here, we review some of the key research findings from the last couple of decades and summarise the strategies being explored for therapeutic intervention.

Therapeutic targeting of angiogenesis molecular pathways in angiogenesis-dependent diseases

Angiogenesis is a critical step in the progression of almost all human malignancies and some other life-threatening diseases. Anti-angiogenic therapy is a novel and effective approach for treatment of angiogenesis-dependent diseases such as cancer, diabetic retinopathy, and age-related macular degeneration. In this article, we will review the main strategies developed for anti-angiogenic therapies beside their clinical applications, the major challenges, and the latest advances in the development of anti-angiogenesis-based targeted therapies.

Candidate Heterotaxy Gene FGFR4 Is Essential for Patterning of the Left-Right Organizer in Xenopus

Congenital heart disease (CHD) is the most common birth defect, yet its genetic causes continue to be obscure. Fibroblast growth factor receptor 4 (FGFR4) recently emerged in a large patient exome sequencing study as a candidate disease gene for CHD and specifically heterotaxy. In heterotaxy, patterning of the left-right (LR) body axis is compromised, frequently leading to defects in the heart's LR architecture and severe CHD. FGF ligands like FGF8 and FGF4 have been previously implicated in LR development with roles ranging from formation of the laterality organ [LR organizer (LRO)] to the transfer of asymmetry from the embryonic midline to the lateral plate mesoderm (LPM). However, much less is known about which FGF receptors (FGFRs) play a role in laterality. Here, we show that the candidate heterotaxy gene FGFR4 is essential for proper organ situs in Xenopus and that frogs depleted of fgfr4 display inverted cardiac and gut looping. Fgfr4 knockdown causes mispatterning of the LRO even before cilia on its surface initiate symmetry-breaking fluid flow, indicating a role in the earliest stages of LR development. Specifically, fgfr4 acts during gastrulation to pattern the paraxial mesoderm, which gives rise to the lateral pre-somitic portion of the LRO. Upon fgfr4 knockdown, the paraxial mesoderm is mispatterned in the gastrula and LRO, and crucial genes for symmetry breakage, like coco, xnr1, and gdf3 are subsequently absent from the lateral portions of the organizer. In summary, our data indicate that FGF signaling in mesodermal LRO progenitors defines cell fates essential for subsequent LR patterning.

Up-regulation of fibroblast growth factor receptor 1 due to prenatal tobacco exposure can lead to developmental defects in new born

Introduction: Tobacco-smoking is one of the most important risk factor for preterm delivery, pregnancy loss, low birth weight, and fetal growth restriction. It is estimated that approximately 30% of growth-restricted neonates could be independently associated with maternal smoking.Methods: In this study, gene expression profile, GSE11798, was chosen from GEO database with an aim to perceive change in gene expression signature in new born due to maternal smoking. Enrichment analysis was performed to annotate differentially expressed genes (DEGs) through gene ontology and pathway analysis using DAVID. Protein-protein interactions and module detection of these DEGs were carried out using cytoscape v3.6.0. Thirty umbilical cord tissue samples from 15 smokers and 15 non-smokers pregnant women were included in this analysis.Results: Twenty-six differentially expressed genes (DEGs) between two groups were selected using GEO2R tool. The DEGs were observed to be participating in biological processes/pathways related to growth releasing hormone, angiogenesis, embryonic skeletal, and cardiac development. Fibroblast growth factor receptor-1 (FGFR1) was identified to be the hub node with 348 interacting partners, which regulates transcription, cell growth, differentiation, and apoptosis. The up-regulation of FGFR1 in umbilical cord tissue may lead to reproductive and developmental complications such as encephalocraniocutaneous lipomatosis, osteoglophonic dysplasia, and Pfeiffer syndrome in new-borns.Conclusion: The findings manifests the possibility of overcoming these adverse health effects in new born through FGFR1 modulating treatments during pregnancy.

Like a hole in the head: Development, evolutionary implications and diseases of the cranial foramina

Cranial foramina are holes in the skull through which nerves and blood vessels pass to reach both deep and superficial tissues. They are often overlooked in the literature; however they are complex structures that form within the developing cranial bones during embryogenesis and then remain open throughout life, despite the bone surrounding them undergoing constant remodelling. They are invaluable in assigning phylogeny in the fossil record and their size has been used, by some, to imply function of the nerve and/or blood vessel that they contained. Despite this, there are very few studies investigating the development or normal function of the cranial foramina. In this review, we will discuss the development of the cranial foramina and their subsequent maintenance, highlighting key gaps in the knowledge. We consider whether functional interpretations can be made from fossil material given a lack of knowledge regarding their contents and maintenance. Finally, we examine the significant role of malformation of foramina in congenital diseases such as craniosynostosis.

Crouzon syndrome: Genetic and intervention review

Crouzon syndrome exhibits considerable phenotypic heterogeneity, in the aetiology of which genetics play an important role. FGFR2 mediates extracellular signals into cells and the mutations in the FGFR2 gene cause this syndrome occurrence. Activated FGFs/FGFR2 signaling disrupts the balance of differentiation, cell proliferation, and apoptosis via its downstream signal pathways. However, very little is known about the cellular and molecular factors leading to severity of this phenotype. Revealing the molecular pathology of craniosynostosis will be a great value for genetic counselling, diagnosis, prognosis and early intervention programs. This mini-review summarizes the fundamental and recent scientific literature on genetic disorder of Crouzon syndrome and presents a graduated strategy for the genetic approach, diagnosis and the management of this complex craniofacial defect.

Developmental pathways in the pathogenesis of lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and terminal lung disease with no known cure. IPF is a disease of aging, with median age of diagnosis over 65 years. Median survival is between 3 and 5 years after diagnosis. IPF is characterized primarily by excessive deposition of extracellular matrix (ECM) proteins by activated lung fibroblasts and myofibroblasts, resulting in reduced gas exchange and impaired pulmonary function. Growing evidence supports the concept of a pro-fibrotic environment orchestrated by underlying factors such as genetic predisposition, chronic injury and aging, oxidative stress, and impaired regenerative responses may account for disease development and persistence. Currently, two FDA approved drugs have limited efficacy in the treatment of IPF. Many of the genes and gene networks associated with lung development are induced or activated in IPF. In this review, we analyze current knowledge in the field, gained from both basic and clinical research, to provide new insights into the disease process, and potential approaches to treatment of pulmonary fibrosis.

Thermoresponsive Citrate-Based Graphene Oxide Scaffold Enhances Bone Regeneration from BMP9-Stimulated Adipose-Derived Mesenchymal Stem Cells

Effective bone tissue engineering is important to overcome the unmet clinical challenges as more than 1.6 million bone grafts are done annually in the United States. Successful bone tissue engineering needs minimally three critical constituents: osteoprogenitor cells, osteogenic factors, and osteoinductive/osteoconductive scaffolds. Osteogenic progenitors are derived from multipotent mesenchymal stem cells (MSCs), which can be prepared from numerous tissue sources, including adipose tissue. We previously showed that BMP9 is the most osteogenic BMP and induces robust bone formation of immortalized mouse adipose-derived MSCs entrapped in a citrate-based thermoresponsive hydrogel referred to as PPCNg. As graphene and its derivatives emerge as promising biomaterials, here we develop a novel thermosensitive and injectable hybrid material by combining graphene oxide (GO) with PPCNg (designated as GO-P) and characterize its ability to promote bone formation. We demonstrate that the thermoresponsive behavior of the hybrid material is maintained while effectively supporting MSC survival and proliferation. Furthermore, GO-P induces early bone-forming marker alkaline phosphatase (ALP) and potentiates BMP9-induced expression of osteogenic regulators and bone markers as well as angiogenic factor VEGF in MSCs. In vivo studies show BMP9-transduced MSCs entrapped in the GO-P scaffold form well-mineralized and highly vascularized trabecular bone. Thus, these results indicate that GO-P hybrid material may function as a new biocompatible, injectable scaffold with osteoinductive and osteoconductive activities for bone regeneration.

Evaluation and Immunolocalization of BMP4 and FGF8 in Odontogenic Cyst and Tumors

Growth factors like bone morphogenetic protein 4 (BMP4) and fibroblast growth factor 8 (FGF8) play a major role in organogenesis and specifically in odontogenesis. They are also believed to have a role in oncogenesis. Thus, any discrepancies in their standard behavior and activity would lead to serious abnormalities including odontogenic cyst and tumors. The present research work investigated the expression of BMP4 and FGF8 in odontogenic tumors (OT) and cyst as well as developing tooth germs to elucidate their roles. Dental organs of various odontogenic stages and 30 OTs including solid multicystic ameloblastomas (SMA, 10 cases), ameloblastic fibroma (AF, 10 cases), odontogenic myxoma (OM, 10 cases), and odontogenic cysts: odontogenic keratocyst (OKC, 10 cases) were evaluated in both epithelial and mesenchymal components for the expression of BMP4 and FGF8 using immunohistochemistry. The epithelial nuclear expression of BMP4 was highest in OKC (9 cases) while FGF8 was highest in SMA (10 cases). The mesenchymal nuclear expression of both BMP4 (8 cases) (p = 0.001) and FGF8 (9 cases) (p = 0.045) were significantly high in OMs among all OTs. Both growth factors were actively expressed in different stages of tooth development. The expression of BMP4 and FGF8 corelates well with the proliferative component of the pathologies, indicating a possible role in the pathogenesis and progression.

FGF Family: From Drug Development to Clinical Application

Fibroblast growth factor (FGF) belongs to a large family of growth factors. FGFs use paracrine or endocrine signaling to mediate a myriad of biological and pathophysiological process, including angiogenesis, wound healing, embryonic development, and metabolism regulation. FGF drugs for the treatment of burn and ulcer wounds are now available. The recent discovery of the crucial roles of the endocrine-acting FGF19 subfamily in maintaining homeostasis of bile acid, glucose, and phosphate further extended the activity profile of this family. Here, the applications of recombinant FGFs for the treatment of wounds, diabetes, hypophosphatemia, the development of FGF receptor inhibitors as anti-neoplastic drugs, and the achievements of basic research and applications of FGFs in China are reviewed.

Increased FGF8 signaling promotes chondrogenic rather than osteogenic development in the embryonic skull

The bones of the cranial vault are formed directly from mesenchymal cells through intramembranous ossification rather than via a cartilage intermediate. Formation and growth of the skull bones involves the interaction of multiple cell-cell signaling pathways, with fibroblast growth factors (FGFs) and their receptors exerting a prominent influence. Mutations within the FGF signaling pathway are the most frequent cause of craniosynostosis, which is a common human craniofacial developmental abnormality characterized by the premature fusion of the cranial sutures. Here, we have developed new mouse models to investigate how different levels of increased FGF signaling can affect the formation of the calvarial bones and associated sutures. Whereas moderate Fgf8 overexpression resulted in delayed ossification followed by craniosynostosis of the coronal suture, higher Fgf8 levels promoted a loss of ossification and favored cartilage over bone formation across the skull. By contrast, endochondral bones were still able to form and ossify in the presence of increased levels of Fgf8, although the growth and mineralization of these bones were affected to varying extents. Expression analysis demonstrated that abnormal skull chondrogenesis was accompanied by changes in the genes required for Wnt signaling. Moreover, further analysis indicated that the pathology was associated with decreased Wnt signaling, as the reduction in ossification could be partially rescued by halving Axin2 gene dosage. Taken together, these findings indicate that mesenchymal cells of the skull are not fated to form bone, but can be forced into a chondrogenic fate through the manipulation of FGF8 signaling. These results have implications for evolution of the different methods of ossification as well as for therapeutic intervention in craniosynostosis.

Characterization of the essential role of bone morphogenetic protein 9 (BMP9) in osteogenic differentiation of mesenchymal stem cells (MSCs) through RNA interference

Mesenchymal stem cells (MSCs) are multipotent stem cells and capable of differentiating into multiple cell types including osteoblastic, chondrogenic and adipogenic lineages. We previously identified BMP9 as one of the most potent BMPs that induce osteoblastic differentiation of MSCs although exact molecular mechanism through which BMP9 regulates osteogenic differentiation remains to be fully understood. Here, we seek to develop a recombinant adenovirus system to optimally silence mouse BMP9 and then characterize the important role of BMP9 in osteogenic differentiation of MSCs. Using two different siRNA bioinformatic prediction programs, we design five siRNAs targeting mouse BMP9 (or simB9), which are expressed under the control of the converging H1 and U6 promoters in recombinant adenovirus vectors. We demonstrate that two of the five siRNAs, simB9-4 and simB9-7, exhibit the highest efficiency on silencing exogenous mouse BMP9 in MSCs. Furthermore, simB9-4 and simB9-7 act synergistically in inhibiting BMP9-induced expression of osteogenic markers, matrix mineralization and ectopic bone formation from MSCs. Thus, our findings demonstrate the important role of BMP9 in osteogenic differentiation of MSCs. The characterized simB9 siRNAs may be used as an important tool to investigate the molecular mechanism behind BMP9 osteogenic signaling. Our results also indicate that recombinant adenovirus-mediated expression of siRNAs is efficient and sustained, and thus may be used as an effective delivery vehicle of siRNA therapeutics.

Growth factors FGF8 and FGF2 and their receptor FGFR1, transcriptional factors Msx-1 and MSX-2, and apoptotic factors p19 and RIP5 participate in the early human limb development

The expression pattern of fibroblast growth factors FGF8 and FGF2 and their receptor FGFR1, transcription factors MSX-1 and MSX-2, as well as cell proliferation (Ki-67) and cell death associated caspase-3, p19 and RIP5 factors were analyzed in histological sections of eight 4th-9th-weeks developing human limbs by immunohistochemistry and semi-thin sectioning. Increasing expression of all analyzed factors (except FGF8) characterized both the multilayered human apical ectodermal ridge (AER), sub-ridge mesenchyme (progress zone) and chondrocytes in developing human limbs. While cytoplasmic co-expression of MSX-1 and MSX-2 was observed in both limb epithelium and mesenchyme, p19 displayed strong cytoplasmic expression in non-proliferating cells. Nuclear expression of Ki-67 proliferating cells, and partly of MSX-1 and MSX-2 was detected in the whole limb primordium. Strong expression of factors p19 and RIP5, both in the AER and mesenchyme of human developing limbs indicates their possible involvement in control of cell senescence and cell death. In contrast to animal studies, expression of FGFR1 in the surface ectoderm and p19 in the whole limb primordium might reflect interspecies differences in limb morphology. Expression of FGF2 and downstream RIP5 gene, and transcription factors Msx-1 and MSX-2 did not show human-specific changes in expression pattern. Based on their spatio-temporal expression during human limb development, our study indicates role of FGFs and Msx genes in stimulation of cell proliferation, limb outgrowth, digit elongation and separation, and additionally MSX-2 in control of vasculogenesis. The cascade of orchestrated gene expressions, including the analyzed developmental factors, jointly contribute to the complex human limb development.

Regulation of ciliary function by fibroblast growth factor signaling identifies FGFR3-related disorders achondroplasia and thanatophoric dysplasia as ciliopathies

Cilia project from almost every cell integrating extracellular cues with signaling pathways. Constitutive activation of FGFR3 signaling produces the skeletal disorders achondroplasia (ACH) and thanatophoric dysplasia (TD), but many of the molecular mechanisms underlying these phenotypes remain unresolved. Here, we report in vivo evidence for significantly shortened primary cilia in ACH and TD cartilage growth plates. Using in vivo and in vitro methodologies, our data demonstrate that transient versus sustained activation of FGF signaling correlated with different cilia consequences. Transient FGF pathway activation elongated cilia, while sustained activity shortened cilia. FGF signaling extended primary cilia via ERK MAP kinase and mTORC2 signaling, but not through mTORC1. Employing a GFP-tagged IFT20 construct to measure intraflagellar (IFT) speed in cilia, we showed that FGF signaling affected IFT velocities, as well as modulating cilia-based Hedgehog signaling. Our data integrate primary cilia into canonical FGF signal transduction and uncover a FGF-cilia pathway that needs consideration when elucidating the mechanisms of physiological and pathological FGFR function, or in the development of FGFR therapeutics.

Glycosylation as a Main Regulator of Growth and Death Factor Receptors Signaling

Glycosylation is a very frequent and functionally important post-translational protein modification that undergoes profound changes in cancer. Growth and death factor receptors and plasma membrane glycoproteins, which upon activation by extracellular ligands trigger a signal transduction cascade, are targets of several molecular anti-cancer drugs. In this review, we provide a thorough picture of the mechanisms bywhich glycosylation affects the activity of growth and death factor receptors in normal and pathological conditions. Glycosylation affects receptor activity through three non-mutually exclusive basic mechanisms: (1) by directly regulating intracellular transport, ligand binding, oligomerization and signaling of receptors; (2) through the binding of receptor carbohydrate structures to galectins, forming a lattice thatregulates receptor turnover on the plasma membrane; and (3) by receptor interaction with gangliosides inside membrane microdomains. Some carbohydrate chains, for example core fucose and β1,6-branching, exert a stimulatory effect on all receptors, while other structures exert opposite effects on different receptors or in different cellular contexts. In light of the crucial role played by glycosylation in the regulation of receptor activity, the development of next-generation drugs targeting glyco-epitopes of growth factor receptors should be considered a therapeutically interesting goal.

MicroRNA-567 inhibits cell proliferation, migration and invasion by targeting FGF5 in osteosarcoma

MicroRNAs (miRNAs) have been widely reported to have important regulatory roles in various human tumors, including osteosarcoma (OS). The aim of this study was to focus on the role of less well-known miRNA-567 (miR-567) in OS. We found the expression of miR-567 was significantly reduced in OS tissues and cell lines (MG-63, U2OS and Saos-2) compared with the adjacent normal tissues and normal osteoblastic cells (hFOB), respectively. Moreover, exogenous miR-567 overexpression inhibited OS cell proliferation, migration and invasion by CCK-8, Transwell assays, respectively. We further explored the mechanism underlying the suppressive effects of miR-567 on OS cells and identified a potential target of miR-567 binds to the 3'UTR of fibroblast growth factor 5 (FGF5) using TargetScan program. Furthermore, enforced expression of miR-567 decreased the expression of FGF5 in both MG-63 and U2OS cells using luciferase reporter assay and Western blotting. We also showed that overexpression of FGF5 could partially antagonize the suppressive effects of miR-567 on OS cell proliferation, migration and invasion. Taken together, our data indicated that miR-567 may function as a tumor suppressor by negatively regulating FGF5 and be potential therapeutic targets for the treatment of OS.

CRISPR/Cas9-mediated reversibly immortalized mouse bone marrow stromal stem cells (BMSCs) retain multipotent features of mesenchymal stem cells (MSCs)

Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic progenitor cells that can undergo self-renewal and differentiate into multi-lineages. Bone marrow stromal stem cells (BMSCs) represent one of the most commonly-used MSCs. In order to overcome the technical challenge of maintaining primary BMSCs in long-term culture, here we seek to establish reversibly immortalized mouse BMSCs (imBMSCs). By exploiting CRISPR/Cas9-based homology-directed-repair (HDR) mechanism, we target SV40T to mouse Rosa26 locus and efficiently immortalize mouse BMSCs (i.e., imBMSCs). We also immortalize BMSCs with retroviral vector SSR #41 and establish imBMSC41 as a control line. Both imBMSCs and imBMSC41 exhibit long-term proliferative capability although imBMSC41 cells have a higher proliferation rate. SV40T mRNA expression is 130% higher in imBMSC41 than that in imBMSCs. However, FLP expression leads to 86% reduction of SV40T expression in imBMSCs, compared with 63% in imBMSC41 cells. Quantitative genomic PCR analysis indicates that the average copy number of SV40T and hygromycin is 1.05 for imBMSCs and 2.07 for imBMSC41, respectively. Moreover, FLP expression removes 92% of SV40T in imBMSCs at the genome DNA level, compared with 58% of that in imBMSC41 cells, indicating CRISPR/Cas9 HDR-mediated immortalization of BMSCs can be more effectively reversed than that of retrovirus-mediated random integrations. Nonetheless, both imBMSCs and imBMSC41 lines express MSC markers and are highly responsive to BMP9-induced osteogenic, chondrogenic and adipogenic differentiation in vitro and in vivo. Thus, the engineered imBMSCs can be used as a promising alternative source of primary MSCs for basic and translational research in the fields of MSC biology and regenerative medicine.

Mutant FGFR3 associated with SADDAN disease causes cytoskeleton disorganization through PLCγ1/Src-mediated paxillin hyperphosphorylation

K650M/E substitutions in the Fibroblast growth factor receptor 3 (FGFR3) are associated with Severe Achondroplasia with Developmental Delay and Acanthosis Nigricans (SADDAN) and Thanatophoric Dysplasia type II (TDII), respectively. Both SADDAN and TDII present with affected endochondral ossification marked by impaired chondrocyte functions and growth plate disorganization. In vitro, K650M/E substitutions confer FGFR3 constitutive kinase activity leading to impaired biosynthesis and accumulation of immature receptors in endoplasmic reticulum (ER)/Golgi. From those compartments, both SADDAN-FGFR3 and TDII-FGFR3 receptors engender uncontrolled signalling, activating PLCγ1, signal transducer and activator of transcription 1, 3 and 5 (STAT1/3/5) and ERK1/2 effectors. Here, we investigated the impact of SADDAN-FGFR3 and TDII-FGFR3 signalling on cytoskeletal organization. We report that SADDAN-FGFR3, but not TDII-FGFR3, affects F-actin organization by inducing tyrosine hyperphosphorylation of paxillin, a key regulator of focal adhesions and actin dynamics. Paxillin phosphorylation was upregulated at tyrosine 118, a functional target of Src and FAK kinases. By using Src-deficient cells and a Src kinase inhibitor, we established a role played by Src activation in paxillin hyperphosphorylation. Moreover, we found that SADDAN-FGFR3 induced FAK phosphorylation at tyrosines 576/577, suggesting its involvement as a Src co-activator in paxillin phosphorylation. Interestingly, paxillin hyperphosphorylation by SADDAN-FGFR3 caused paxillin mislocalization and partial co-localization with the mutant receptor. Finally, the SADDAN-FGFR3 double mutant unable to bind PLCγ1 failed to promote paxillin hyperphosphorylation, pointing to PLCγ1 as an early player in mediating paxillin alterations. Overall, our findings contribute to elucidate the molecular mechanism leading to cell dysfunctions caused by SADDAN-FGFR3 signalling.

A gut-brain axis regulating glucose metabolism mediated by bile acids and competitive fibroblast growth factor actions at the hypothalamus

OBJECTIVE

Bile acids have been implicated as important regulators of glucose metabolism via activation of FXR and GPBAR1. We have previously shown that FGF19 can modulate glucose handling by suppressing the activity of hypothalamic AGRP/NPY neurons. As bile acids stimulate the release of FGF19/FGF15 into the circulation, we pursued the potential of bile acids to improve glucose tolerance via a gut-brain axis involving FXR and FGF15/FGF19 within enterocytes and FGF receptors on hypothalamic AGRP/NPY neurons.

METHODS

A 5-day gavage of taurocholic acid, mirroring our previous protocol of a 5-day FGF19 treatment, was performed. Oral glucose tolerance tests in mice with genetic manipulations of FGF signaling and melanocortin signaling were used to define a gut-brain axis responsive to bile acids.

RESULTS

The taurocholic acid gavage led to increased serum concentrations of taurocholic acid as well as increases of FGF15 mRNA in the ileum and improved oral glucose tolerance in obese (ob/ob) mice. In contrast, lithocholic acid, an FXR antagonist but a potent agonist for GPBAR1, did not improve glucose tolerance. The positive response to taurocholic acid is dependent upon an intact melanocortinergic system as obese MC4R-null mice or ob/ob mice without AGRP did not show improvements in glucose tolerance after taurocholate gavage. We also tested the FGF receptor isoform necessary for the bile acid response, using AGRP:Fgfr1-/- and AGRP:Fgfr2-/- mice. While the absence of FGFR1 in AGRP/NPY neurons did not alter glucose tolerance after taurocholate gavage, manipulations of Fgfr2 caused bidirectional changes depending upon the experimental model. We hypothesized the existence of an endogenous hypothalamic FGF, most likely FGF17, that acted as a chronic activator of AGRP/NPY neurons. We developed two short peptides based on FGF8 and FGF17 that should antagonize FGF17 action. Both of these peptides improved glucose homeostasis after a 4-day course of central and peripheral injections. Significantly, daily average blood glucose from continuous glucose monitoring was reduced in all tested animals but glucose concentrations remained in the euglycemia range.

CONCLUSIONS

We have defined a gut-brain axis that regulates glucose metabolism mediated by antagonistic fibroblast growth factors. From the intestine, bile acids stimulate FGF15 secretion, leading to activation of the FGF receptors in hypothalamic AGRP/NPY neurons. FGF receptor intracellular signaling subsequently silences AGRP/NPY neurons, leading to improvements of glucose tolerance that are likely mediated by the autonomic nervous system. Finally, short peptides that antagonize homodimeric FGF receptor signaling within the hypothalamus have beneficial effects on glucose homeostasis without inducing hypoglycemia. These peptides could provide a new mode of regulating glucose metabolism.

Novel chromosomal microduplications associated with dolichocephaly craniosynostosis: A case report

INSTRUCTION

Craniosynostosis is a human disorder characterized by the premature fusing of the cranial sutures in infants. Point mutations in hotspot genes such as FGFRs are the well-recognized causes of syndromic craniosynostosis, but chromosomal abbreviations may also play an important role in developing this disease. Here, we report the case in China of a 2-year-boy dolichocephaly craniosynostosis. Karyotyping by both G-bind staining and array-based DNA hybridization identified microduplications on Chromosomes 8p11.22 q12.1 and 16q11.2 q21, but none of the known pathogenic mutations was detected.

CONCLUSIONS

This finding not only expands knowledge on the genetic mechanism of craniosynostosis but also provides a new target for the early diagnosis of this rare disease.

Friends Turned Foes: Angiogenic Growth Factors beyond Angiogenesis

Angiogenesis, the formation of new blood vessels from pre-existing ones is a biological process that ensures an adequate blood flow is maintained to provide the cells with a sufficient supply of nutrients and oxygen within the body. Numerous soluble growth factors and inhibitors, cytokines, proteases as well as extracellular matrix proteins and adhesion molecules stringently regulate the multi-factorial process of angiogenesis. The properties and interactions of key angiogenic molecules such as vascular endothelial growth factors (VEGFs), fibroblast growth factors (FGFs) and angiopoietins have been investigated in great detail with respect to their molecular impact on angiogenesis. Since the discovery of angiogenic growth factors, much research has been focused on their biological actions and their potential use as therapeutic targets for angiogenic or anti-angiogenic strategies in a context-dependent manner depending on the pathologies. It is generally accepted that these factors play an indispensable role in angiogenesis. However, it is becoming increasingly evident that this is not their only role and it is likely that the angiogenic factors have important functions in a wider range of biological and pathological processes. The additional roles played by these molecules in numerous pathologies and biological processes beyond angiogenesis are discussed in this review.

Genetics of clubfoot; recent progress and future perspectives

Clubfoot or talipes equinovarus (TEV) is an inborn three-dimensional deformity of leg, ankle and foot. It results from structural defects of several tissues of foot and lower leg leading to abnormal positioning of foot and ankle joints. TEV can lead to long-lasting functional disability, malformation and discomfort if left untreated. Substantial progress has been achieved in the management and diagnosis of limb defects; however, not much is known about the molecular players and signalling pathways underlying TEV disorder. The homeostasis and development of the limb depends on the complex interactions between the lateral plate mesoderm cells and outer ectoderm. These complex interactions include HOX signalling and PITX1-TBX4 pathways. The susceptibility to develop TEV is determined by a number of environmental and genetic factors, although the nature and level of interplay between them remains unclear. Familial occurrence and inter and intra phenotypic variability of TEV is well documented. Variants in genes that code for contractile proteins of skeletal myofibers might play a role in the aetiology of TEV but, to date, no strong candidate genes conferring increased risk have emerged, although variants in TBX4, PITX1, HOXA, HOXC and HOXD clusters genes, NAT2 and others have been shown to be associated with TEV. The mechanisms by which variants in these genes confer risk and the nature of the physical and genetic interaction between them remains to be determined. Elucidation of genetic players and cellular pathways underlying TEV will certainly increase our understanding of the pathophysiology of this deformity.

The Relationship between Brachycephalic Head Features in Modern Persian Cats and Dysmorphologies of the Skull and Internal Hydrocephalus

Background

Cat breeders observed a frequent occurrence of internal hydrocephalus in Persian cats with extreme brachycephalic head morphology.

Objective

To investigate a possible relationship among the grade of brachycephaly, ventricular dilatation, and skull dysmorphologies in Persian cats.

Animals

92 Persian‐, 10 Domestic shorthair cats.

Methods

The grade of brachycephaly was determined on skull models based on CT datasets. Cranial measurements were examined with regard to a possible correlation with relative ventricular volume, and cranial capacity. Persians with high (peke‐face Persians) and lower grades of brachycephaly (doll‐face Persians) were investigated for the presence of skull dysmorphologies.

Results

The mean cranial index of the peke‐face Persians (0.97 ± 0.14) was significantly higher than the mean cranial index of doll‐face Persians (0.66 ± 0.04; P < 0.001). Peke‐face Persians had a lower relative nasal bone length (0.15 ± 0.04) compared to doll‐face (0.29 ± 0.08; P < 0.001). The endocranial volume was significantly lower in doll‐face than peke‐face Persians (89.6 ± 1.27% versus 91.76 ± 2.07%; P < 0.001). The cranial index was significantly correlated with this variable (Spearman's r: 0.7; P < 0.0001). Mean ventricle: Brain ratio of the peke‐face group (0.159 ± 0.14) was significantly higher compared to doll‐face Persians (0.015 ± 0.01; P < 0.001).

Conclusion and Clinical Relevance

High grades of brachycephaly are also associated with malformations of the calvarial and facial bones as well as dental malformations. As these dysmorphologies can affect animal welfare, the selection for extreme forms of brachycephaly in Persian cats should be reconsidered.

lncRNA H19 mediates BMP9-induced osteogenic differentiation of mesenchymal stem cells (MSCs) through Notch signaling

Mesenchymal stem cells (MSCs) are multipotent progenitor cells that can undergo self-renewal and differentiate into multiple lineages. Osteogenic differentiation from MSCs is a well-orchestrated process and regulated by multiple signaling pathways. We previously demonstrated that BMP9 is one of the most potent osteogenic factors. However, molecular mechanism through which BMP9 governs osteoblastic differentiation remains to be fully understood. Increasing evidence indicates noncoding RNAs (ncRNAs) may play important regulatory roles in many physiological and/or pathologic processes. In this study, we investigate the role of lncRNA H19 in BMP9-regulated osteogenic differentiation of MSCs. We demonstrated that H19 was sharply upregulated at the early stage of BMP9 stimulation of MSCs, followed by a rapid decease and gradual return to basal level. This process was correlated with BMP9-induced expression of osteogenic markers. Interestingly, either constitutive H19 expression or silencing H19 expression in MSCs significantly impaired BMP9-induced osteogenic differentiation in vitro and in vivo, which was effectively rescued by the activation of Notch signaling. Either constitutive H19 expression or silencing H19 expression led to the increased expression of a group of miRNAs that are predicted to target Notch ligands and receptors. Thus, these results indicate that lncRNA H19 functions as an important mediator of BMP9 signaling by modulating Notch signaling-targeting miRNAs. Our findings suggest that the well-coordinated biphasic expression of lncRNA H19 may be essential in BMP9-induced osteogenic differentiation of MSCs, and that dysregulated H19 expression may impair normal osteogenesis, leading to pathogenic processes, such as bone tumor development.

Genetics of Short Stature

Short stature is a common and heterogeneous condition that is often genetic in etiology. For most children with genetic short stature, the specific molecular causes remain unknown; but with advances in exome/genome sequencing and bioinformatics approaches, new genetic causes of growth disorders have been identified, contributing to the understanding of the underlying molecular mechanisms of longitudinal bone growth and growth failure. Identifying new genetic causes of growth disorders has the potential to improve diagnosis, prognostic accuracy, and individualized management, and help avoid unnecessary testing for endocrine and other disorders.

Decrease of miR-195 Promotes Chondrocytes Proliferation and Maintenance of Chondrogenic Phenotype via Targeting FGF-18 Pathway

Slow growth and rapid loss of chondrogenic phenotypes are the major problems affecting chronic cartilage lesions. The role of microRNA-195 (miR-195) and its detailed working mechanism in the fore-mentioned process remains unknown. Fibroblastic growth factor 18 (FGF-18) plays a key role in cartilage homeostasis; whether miR-195 could regulate FGF-18 and its downstream signal pathway in chondrocyte proliferation and maintenance of chondrogenic phenotypes still remains unclear. The present research shows elevated miR-195 but depressed FGF-18 expressed in joint fluid specimens of 20 patients with chronic cartilage lesions and in CH1M and CH3M chondrocytes when compared with that in joint fluid specimens without cartilage lesions and in CH1W and CH2W chondrocytes, respectively. The following loss of function test revealed that downregulation of miR-195 by transfection of miR-195 inhibitors promoted chondrocyte proliferation and expression of a type II collagen α I chain (Col2a1)/aggrecan. Through the online informatics analysis we theoretically predicted that miR-195 could bind to a FGF-18 3' untranslated region (3'UTR), also, we verified that a miR-195 could regulate the FGF-18 and its downstream pathway. The constructed dual luciferase assay further confirmed that FGF-18 was a direct target of miR-195. The executed anti-sense experiment displayed that miR-195 could regulate chondrocyte proliferation and Col2a1/aggrecan expression via the FGF-18 pathway. Finally, through an in vivo anterior cruciate ligament transection (ACLT) model, downregulation of miR-195 presented a significantly protective effect on chronic cartilage lesions. Evaluating all of the outcomes of the current research revealed that a decrease of miR-195 protected chronic cartilage lesions by promoting chondrocyte proliferation and maintenance of chondrogenic phenotypes via the targeting of the FGF-18 pathway and that the miR-195/FGF-18 axis could be a potential target in the treatment of cartilage lesions.

BMP9 induces osteogenesis and adipogenesis in the immortalized human cranial suture progenitors from the patent sutures of craniosynostosis patients

The cranial suture complex is a heterogeneous tissue consisting of osteogenic progenitor cells and mesenchymal stem cells (MSCs) from bone marrow and suture mesenchyme. The fusion of cranial sutures is a highly coordinated and tightly regulated process during development. Craniosynostosis is a congenital malformation caused by premature fusion of cranial sutures. While the progenitor cells derived from the cranial suture complex should prove valuable for studying the molecular mechanisms underlying suture development and pathogenic premature suture fusion, primary human cranial suture progenitors (SuPs) have limited life span and gradually lose osteoblastic ability over passages. To overcome technical challenges in maintaining sufficient and long-term culture of SuPs for suture biology studies, we establish and characterize the reversibly immortalized human cranial suture progenitors (iSuPs). Using a reversible immortalization system expressing SV40 T flanked with FRT sites, we demonstrate that primary human suture progenitor cells derived from the patent sutures of craniosynostosis patients can be efficiently immortalized. The iSuPs maintain long-term proliferative activity, express most of the consensus MSC markers and can differentiate into osteogenic and adipogenic lineages upon BMP9 stimulation in vitro and in vivo. The removal of SV40 T antigen by FLP recombinase results in a decrease in cell proliferation and an increase in the endogenous osteogenic and adipogenic capability in the iSuPs. Therefore, the iSuPs should be a valuable resource to study suture development, intramembranous ossification and the pathogenesis of craniosynostosis, as well as to explore cranial bone tissue engineering.

Ectoderm-mesoderm crosstalk in the embryonic limb: The role of fibroblast growth factor signaling

In this commentary we focus on the function of FGFs during limb development and morphogenesis. Our goal is to understand, interpret and, when possible, reconcile the interesting findings and conflicting results that remain unexplained. For example, the cell death pattern observed after surgical removal of the AER versus genetic removal of the AER-Fgfs is strikingly different and the field is at an impasse with regard to an explanation. We also discuss the idea that AER function may involve signaling components in addition to the AER-FGFs and that signaling from the non-AER ectoderm may also have a significant contribution. We hope that a re-evaluation of current studies and a discussion of outstanding questions will motivate new experiments, especially considering the availability of new technologies, that will fuel further progress toward understanding the intricate ectoderm-to-mesoderm crosstalk during limb development. Developmental Dynamics 246:208-216, 2017. © 2016 Wiley Periodicals, Inc.