Unraveling the function of FGF signaling in human hypoblast specialization.

Dattani et al.1 developed a method for inducing hypoblast-like cells from human naive pluripotent stem cells. They elucidated the requirement for FGF signaling in human hypoblast specialization at a specific time window, which was previously controversial.

Molecular Interaction of Soluble Klotho with FGF23 in the Pathobiology of Aortic Valve Lesions Induced by Chronic Kidney Disease.

Chronic kidney disease (CKD) is linked to greater prevalence and rapid progression of calcific aortic valve disease (CAVD) characterized by valvular leaflet fibrosis and calcification. Fibroblast growth factor 23 (FGF23) level is elevated, and anti-aging protein Klotho is reduced in CKD patients. However, the roles of FGF23 and Klotho in the mechanism of aortic valve fibrosis and calcification remain unclear. We hypothesized that FGF23 mediates CKD-induced CAVD by enhancing aortic valve interstitial cell (AVIC) fibrosis and calcification, while soluble Klotho inhibits FGF23 effect. Methods and Results: In an old mouse model of CKD, kidney damages were accompanied by aortic valve thickening and calcification. FGF23 levels in plasma and aortic valve were increased, while Klotho levels were decreased. Recombinant FGF23 elevated the inflammatory, fibrogenic, and osteogenic activities in AVICs. Neutralizing antibody or shRNA targeting FGF23 suppressed the pathobiological activities in AVICs from valves affected by CAVD. FGF23 exerts its effects on AVICs via FGF receptor (FGFR)/Yes-associated protein (YAP) signaling, and inhibition of FGFR/YAP reduced FGF23's potency in AVICs. Recombinant Klotho downregulated the pathobiological activities in AVICs exposed to FGF23. Incubation of FGF23 with Klotho formed complexes and decreased FGF23's potency. Further, treatment of CKD mice with recombinant Klotho attenuated aortic valve lesions. Conclusion: This study demonstrates that CKD induces FGF23 accumulation, Klotho insufficiency and aortic valve lesions in old mice. FGF23 upregulates the inflammatory, fibrogenic and osteogenic activities in AVICs via the FGFR/YAP signaling pathway. Soluble Klotho suppresses FGF23 effect through molecular interaction and is capable of mitigating CKD-induced CAVD.

Expression and secretion of SPARC, FGF-21 and DCN in bovine muscle cells: Effects of age and differentiation.

Skeletal muscle growth is an economically important trait in the cattle industry. Secreted muscle-derived proteins, referred to as myokines, have important roles in regulating the growth, metabolism, and health of skeletal muscle in human and biomedical research models. Accumulating evidence supports the importance of myokines in skeletal muscle and whole-body health, though little is known about the potential presence and functional significance of these proteins in cattle. This study evaluates and confirms that secreted proteins acidic and rich in cysteine (SPARC), fibroblast growth factor 21 (FGF-21), myostatin (MSTN), and decorin (DCN) are expressed and SPARC, FGF-21, and DCN are secreted by primary bovine satellite cells from 3- (BSC3; n = 3) and 11- (BSC11; n = 3) month -old commercial angus steers. Cells were cultured and collected at zero, 12, 24, and 48 hours to characterize temporal expression and secretion from undifferentiated and differentiated cells. The expression of SPARC was higher in the undifferentiated (p = 0.04) and differentiated (p = 0.07) BSC11 than BSC3. The same was observed with protein secretion from undifferentiated (p <0.0001) BSC11 compared to BSC3. Protein secretion of FGF-21 was higher in undifferentiated BSC11 (p < 0.0001) vs. BSC3. DCN expression was higher in differentiated BSC11 (p = 0.006) vs. BSC3. Comparing undifferentiated vs. differentiated BSC, MSTN expression was higher in differentiated BSC3 (p ≤ 0.001) for 0, 12, and 24 hours and in BSC11 (p ≤ 0.03) for 0, 12, 24, and 48 hours. There is also a change over time for SPARC expression (p ≤ 0.03) in undifferentiated and differentiated BSC and protein secretion (p < 0.0001) in undifferentiated BSC, as well as FGF-21 expression (p = 0.007) in differentiated BSC. This study confirms SPARC, FGF-21, and DCN are secreted, and SPARC, FGF-21, MSTN, and DCN are expressed in primary bovine muscle cells with age and temporal differences.

Fibroblast growth factor signaling in macrophage polarization: impact on health and diseases.

Fibroblast growth factors (FGFs) are a versatile family of peptide growth factors that are involved in various biological functions, including cell growth and differentiation, embryonic development, angiogenesis, and metabolism. Abnormal FGF/FGF receptor (FGFR) signaling has been implicated in the pathogenesis of multiple diseases such as cancer, metabolic diseases, and inflammatory diseases. It is worth noting that macrophage polarization, which involves distinct functional phenotypes, plays a crucial role in tissue repair, homeostasis maintenance, and immune responses. Recent evidence suggests that FGF/FGFR signaling closely participates in the polarization of macrophages, indicating that they could be potential targets for therapeutic manipulation of diseases associated with dysfunctional macrophages. In this article, we provide an overview of the structure, function, and downstream regulatory pathways of FGFs, as well as crosstalk between FGF signaling and macrophage polarization. Additionally, we summarize the potential application of harnessing FGF signaling to modulate macrophage polarization.

Molecular signaling directing neural plate border formation.

During embryonic development, the vertebrate embryonic epiblast is divided into two parts including neural and superficial ectoderm. The neural plate border (NPB) is a narrow transitional area which locates between these parts and contains multipotent progenitor cells. Despite its small size, the cellular heterogeneity in this region produces specific differentiated cells. Signaling pathways, transcription factors, and the expression/repression of certain genes are directly involved in these differentiation processes. Different factors such as the Wnt signaling cascade, fibroblast growth factor (FGF), bone morphogenetic protein (BMP) signaling, and Notch, which are involved in various stages of the growth, proliferation, and differentiation of embryonic cells, are also involved in the determination and differentiation of neural plate border stem cells. Therefore, it is essential to consider the interactions and temporospatial coordination related to cells, tissues, and adjacent structures. This review examines our present knowledge of the formation of the neural plate border and emphasizes the requirement for interaction between different signaling pathways, including the BMP and Wnt cascades, the expression of its special target genes and their regulations, and the precise tissue crosstalk which defines the neural crest fate in the ectoderm at the early human embryonic stages.

Fibroblast growth factor 23 inhibition attenuates steroid-induced osteonecrosis of the femoral head through pyroptosis.

Steroid-induced osteonecrosis of the femoral head (SONFH) is the predominant cause of non-traumatic osteonecrosis of the femoral head (ONFH). Impaired blood supply and reduced osteogenic activity of the femoral head are the key pathogenic mechanisms of SONFH. Fibroblast growth factor 23 (FGF23) levels are not only a biomarker for early vascular lesions caused by abnormal mineral metabolism, but can also act directly on the peripheral vascular system, leading to vascular pathology. The aim of this study was to observe the role of FGF23 on bone microarchitecture and vascular endothelium, and to investigate activation of pyroptosis in SONFH. Lipopolysaccharide (LPS) combined with methylprednisolone (MPS) was applied for SONFH mouse models, and adenovirus was used to increase or decrease the level of FGF23. Micro-CT and histopathological staining were used to observe the structure of the femoral head, and immunohistochemical staining was used to observe the vascular density. The cells were further cultured in vitro and placed in a hypoxic environment for 12 h to simulate the microenvironment of vascular injury during SONFH. The effect of FGF23 on osteogenic differentiation was evaluated using alkaline phosphatase staining, alizarin red S staining and expression of bone formation-related proteins. Matrigel tube formation assay in vitro and immunofluorescence were used to detect the ability of FGF23 to affect endothelial cell angiogenesis. Steroids activated the pyroptosis signaling pathway, promoted the secretion of inflammatory factors in SONFH models, led to vascular endothelial dysfunction and damaged the femoral head structure. In addition, FGF23 inhibited the HUVECs angiogenesis and BMSCs osteogenic differentiation. FGF23 silencing attenuated steroid-induced osteonecrosis of the femoral head by inhibiting the pyroptosis signaling pathway, and promoting osteogenic differentiation of BMSCs and angiogenesis of HUVECs in vitro.

Role of signaling pathways in age-related orthopedic diseases: focus on the fibroblast growth factor family.

Fibroblast growth factor (FGF) signaling encompasses a multitude of functions, including regulation of cell proliferation, differentiation, morphogenesis, and patterning. FGFs and their receptors (FGFR) are crucial for adult tissue repair processes. Aberrant FGF signal transduction is associated with various pathological conditions such as cartilage damage, bone loss, muscle reduction, and other core pathological changes observed in orthopedic degenerative diseases like osteoarthritis (OA), intervertebral disc degeneration (IVDD), osteoporosis (OP), and sarcopenia. In OA and IVDD pathologies specifically, FGF1, FGF2, FGF8, FGF9, FGF18, FGF21, and FGF23 regulate the synthesis, catabolism, and ossification of cartilage tissue. Additionally, the dysregulation of FGFR expression (FGFR1 and FGFR3) promotes the pathological process of cartilage degradation. In OP and sarcopenia, endocrine-derived FGFs (FGF19, FGF21, and FGF23) modulate bone mineral synthesis and decomposition as well as muscle tissues. FGF2 and other FGFs also exert regulatory roles. A growing body of research has focused on understanding the implications of FGF signaling in orthopedic degeneration. Moreover, an increasing number of potential targets within the FGF signaling have been identified, such as FGF9, FGF18, and FGF23. However, it should be noted that most of these discoveries are still in the experimental stage, and further studies are needed before clinical application can be considered. Presently, this review aims to document the association between the FGF signaling pathway and the development and progression of orthopedic diseases. Besides, current therapeutic strategies targeting the FGF signaling pathway to prevent and treat orthopedic degeneration will be evaluated.

Double promoter and tandem gene strategy for efficiently expressing recombinant FGF21.

BACKGROUND: Fibroblast growth factor 21 (FGF21) is a promising candidate for treating metabolic disorder diseases and has been used in phase II clinical trials. Currently, metabolic diseases are prevalent worldwide, underscoring the significant market potential of FGF21. Therefore, the production of FGF21 must be effectively improved to meet market demand. RESULTS: Herein, to investigate the impact of vectors and host cells on FGF21 expression, we successfully engineered strains that exhibit a high yield of FGF21. Surprisingly, the data revealed that vectors with various copy numbers significantly impact the expression of FGF21, and the results showed a 4.35-fold increase in expression levels. Furthermore, the performance of the double promoter and tandem gene expression construction design surpassed that of the conventional construction method, with a maximum difference of 2.67 times. CONCLUSION: By exploring engineered vectors and host cells, we successfully achieved high-yield production of the FGF21 strain. This breakthrough lays a solid foundation for the future industrialization of FGF21. Additionally, FGF21 can be easily, quickly and efficiently expressed, providing a better tool and platform for the research and application of more recombinant proteins.

FGF signaling modulates mechanotransduction/WNT signaling in progenitors during tooth root development.

Stem/progenitor cells differentiate into different cell lineages during organ development and morphogenesis. Signaling pathway networks and mechanotransduction are important factors to guide the lineage commitment of stem/progenitor cells during craniofacial tissue morphogenesis. Here, we used tooth root development as a model to explore the roles of FGF signaling and mechanotransduction as well as their interaction in regulating the progenitor cell fate decision. We show that Fgfr1 is expressed in the mesenchymal progenitor cells and their progeny during tooth root development. Loss of Fgfr1 in Gli1+ progenitors leads to hyperproliferation and differentiation, which causes narrowed periodontal ligament (PDL) space with abnormal cementum/bone formation leading to ankylosis. We further show that aberrant activation of WNT signaling and mechanosensitive channel Piezo2 occurs after loss of FGF signaling in Gli1-CreER;Fgfr1fl/fl mice. Overexpression of Piezo2 leads to increased osteoblastic differentiation and decreased Piezo2 leads to downregulation of WNT signaling. Mechanistically, an FGF/PIEZO2/WNT signaling cascade plays a crucial role in modulating the fate of progenitors during root morphogenesis. Downregulation of WNT signaling rescues tooth ankylosis in Fgfr1 mutant mice. Collectively, our findings uncover the mechanism by which FGF signaling regulates the fate decisions of stem/progenitor cells, and the interactions among signaling pathways and mechanotransduction during tooth root development, providing insights for future tooth root regeneration.

FGF21 attenuates salt-sensitive hypertension via regulating HNF4α/ACE2 axis in the hypothalamic paraventricular nucleus of mice.

BACKGROUND: Fibroblast growth factor 21 (FGF21) has a protective effect against cardiovascular disease. However, the role of FGF21 in hypertension remains elusive. METHODS: Ten-week-old male C57BL/6 mice were randomly divided into normal-salt (NS) group, NS+FGF21 group, deoxycorticosterone acetate-salt (DOCA) group and DOCA+FGF21 group. The mice in NS group underwent uninephrectomy without receiving DOCA and 1% NaCl and the mice in DOCA group were subjected to uninephrectomy and DOCA-salt (DOCA and 1% NaCl) treatment for 6 weeks. At the same time, the mice were infused with vehicle (artificial cerebrospinal fluid, aCSF) or FGF21 (1 mg/kg) into the bilateral paraventricular nucleus (PVN) of mice. RESULTS: Here, we showed that FGF21 treatment lowered DOCA salt-induced inflammation and oxidative stress in the PVN, which reduced sympathetic nerve activity and hypertension. Mechanistically, FGF21 treatment decreased the expression of HNF4α and inhibited the binding activity of HNF4α to the promoter region of ACE2 in the PVN of DOCA salt-treated mice, which further up-regulated ACE2/Ang (1-7) signals in the PVN. In addition, ACE2 deficiency abolished the protective effect of FGF21 in DOCA salt-treated mice, suggesting that FGF21-mediated antihypertensive effect was dependent on ACE2. CONCLUSIONS: The results demonstrate that FGF21 protects against salt-sensitive hypertension via regulating HNF4α/ACE2/Ang (1-7) axis in the PVN of DOCA salt-treated mice via multi-organ crosstalk between liver, brain and blood vessels.

Naive pluripotent stem cell-based models capture FGF-dependent human hypoblast lineage specification.

The hypoblast is an essential extraembryonic tissue set aside within the inner cell mass in the blastocyst. Research with human embryos is challenging. Thus, stem cell models that reproduce hypoblast differentiation provide valuable alternatives. We show here that human naive pluripotent stem cell (PSC) to hypoblast differentiation proceeds via reversion to a transitional ICM-like state from which the hypoblast emerges in concordance with the trajectory in human blastocysts. We identified a window when fibroblast growth factor (FGF) signaling is critical for hypoblast specification. Revisiting FGF signaling in human embryos revealed that inhibition in the early blastocyst suppresses hypoblast formation. In vitro, the induction of hypoblast is synergistically enhanced by limiting trophectoderm and epiblast fates. This finding revises previous reports and establishes a conservation in lineage specification between mice and humans. Overall, this study demonstrates the utility of human naive PSC-based models in elucidating the mechanistic features of early human embryogenesis.

Exerkines: Benign adaptation for exercise and benefits for non-alcoholic fatty liver disease.

Exercise has multiple beneficial effects on human metabolic health and is regarded as a "polypill" for various diseases. At present, the lack of physical activity usually causes an epidemic of chronic metabolic syndromes, including obesity, cardiovascular diseases, and non-alcoholic fatty liver disease (NAFLD). Remarkably, NAFLD is emerging as a serious public health issue and is associated with the development of cirrhosis and hepatocellular carcinoma. Unfortunately, specific drug therapies for NAFLD and its more severe form, non-alcoholic steatohepatitis (NASH), are currently unavailable. Lifestyle modification is the foundation of treatment recommendations for NAFLD and NASH, especially for exercise. There are under-appreciated organs that crosstalk to the liver during exercise such as muscle-liver crosstalk. Previous studies have reported that certain exerkines, such as FGF21, GDF15, irisin, and adiponectin, are beneficial for liver metabolism and have the potential to be targeted for NAFLD treatment. In addition, some of exerkines can be modified for the new proteins and get enhanced functions, like IL-6/IC7Fc. Another importance of exercise is the physiological adaptation that combats metabolic diseases. Thus, this review aims to summarize the known exerkines and utilize a multi-omics mining tool to identify more exerkines for the future research. Overall, understanding the mechanisms by which exercise-induced exerkines exert their beneficial effects on metabolic health holds promise for the development of novel therapeutic strategies for NAFLD and related diseases.

Modulation of FGF pathway signaling and vascular differentiation using designed oligomeric assemblies.

Many growth factors and cytokines signal by binding to the extracellular domains of their receptors and driving association and transphosphorylation of the receptor intracellular tyrosine kinase domains, initiating downstream signaling cascades. To enable systematic exploration of how receptor valency and geometry affect signaling outcomes, we designed cyclic homo-oligomers with up to 8 subunits using repeat protein building blocks that can be modularly extended. By incorporating a de novo-designed fibroblast growth factor receptor (FGFR)-binding module into these scaffolds, we generated a series of synthetic signaling ligands that exhibit potent valency- and geometry-dependent Ca2+ release and mitogen-activated protein kinase (MAPK) pathway activation. The high specificity of the designed agonists reveals distinct roles for two FGFR splice variants in driving arterial endothelium and perivascular cell fates during early vascular development. Our designed modular assemblies should be broadly useful for unraveling the complexities of signaling in key developmental transitions and for developing future therapeutic applications.

Fibroblast growth factor 21 alleviates idiopathic pulmonary fibrosis by inhibiting PI3K-AKT-mTOR signaling and stimulating autophagy.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive pulmonary disease with an unclear pathogenesis and no available specific drug treatment. The principal etiological factors are lung inflammation caused by environmental factors, damage to alveolar epithelial cells, leading to epithelial-mesenchymal transition (EMT), and the abnormal proliferation of fibroblasts. Here, we have demonstrated that fibroblast growth factor 21 (FGF21) ameliorates IPF via the autophagy pathway. We administered FGF21 to bleomycin (BLM)-treated mice, which ameliorated their defects in lung function, reduced the accumulation of collagen, restored tissue structure, reduced the deposition of hydroxyproline, reduced the expression of collagen I and α-SMA and increased the expression of E-cadherin. The expression of LC3BII and the number of autophagosomes were significantly higher in the lungs. The expression of AKT and mTOR was significantly reduced by FGF21 treatment. We also determined the effects of FGF21 in A549 cells treated with TGF-ß, and found that FGF21 significantly inhibits activation of the AKT signaling pathway, thereby reducing TGF-ß-induced EMT and preventing the uncontrolled proliferation of fibroblasts. We conclude that FGF21 ameliorates IPF by inhibiting the PI3K-AKT-mTOR signaling pathway and activating autophagy, which provides a theoretical basis for FGF21 to be used for the treatment of IPF.

Specification and survival of post-metamorphic branchiomeric neurons in a non-vertebrate chordate.

Tunicates are the sister group to the vertebrates, yet most species have a life cycle split between swimming larva and sedentary adult phases. During metamorphosis, larval neurons are replaced by adult-specific ones. The regulatory mechanisms underlying this replacement remain largely unknown. Using tissue-specific CRISPR/Cas9-mediated mutagenesis in the tunicate Ciona, we show that orthologs of conserved hindbrain and branchiomeric neuron regulatory factors Pax2/5/8 and Phox2 are required to specify the 'neck', a cellular compartment set aside in the larva to give rise to cranial motor neuron-like neurons post-metamorphosis. Using bulk and single-cell RNA-sequencing analyses, we characterize the transcriptome of the neck downstream of Pax2/5/8. We present evidence that neck-derived adult ciliomotor neurons begin to differentiate in the larva and persist through metamorphosis, contrary to the assumption that the adult nervous system is formed after settlement and the death of larval neurons during metamorphosis. Finally, we show that FGF signaling during the larval phase alters the patterning of the neck and its derivatives. Suppression of FGF converts neck cells into larval neurons that fail to survive metamorphosis, whereas prolonged FGF signaling promotes an adult neural stem cell-like fate.

A common flanking variant is associated with enhanced stability of the FGF14-SCA27B repeat locus.

The factors driving or preventing pathological expansion of tandem repeats remain largely unknown. Here, we assessed the FGF14 (GAA)·(TTC) repeat locus in 2,530 individuals by long-read and Sanger sequencing and identified a common 5'-flanking variant in 70.34% of alleles analyzed (3,463/4,923) that represents the phylogenetically ancestral allele and is present on all major haplotypes. This common sequence variation is present nearly exclusively on nonpathogenic alleles with fewer than 30 GAA-pure triplets and is associated with enhanced stability of the repeat locus upon intergenerational transmission and increased Fiber-seq chromatin accessibility.

Knockdown of vitamin D receptor affects early stages of pectoral fin development in zebrafish.

The vitamin D receptor (VDR) signalling has been implicated in vertebrate limb or fin formation. However, the involvement of VDR signalling in the early stages of limb/fin development remains to be elucidated. In this study, the role of VDR signalling in pectoral fin development was investigated in zebrafish embryos. Knockdown of vdr induced the severe impairment of pectoral fin development. The zebrafish larvae lacking vdr exhibited reduced pectoral fins with no skeletal elements. In situ hybridization revealed depletion of vdr downregulated fibroblast growth factor 24 (fgf24), a marker of early pectoral fin bud mesenchyme, in the presumptive fin field even before fin buds were visible. Moreover, a perturbed expression pattern of bone morphogenetic protein 4 (bmp4), a marker of the pectoral fin fold, was observed in the developing fin buds of zebrafish embryos that lost the vdr function. These findings suggest that VDR signalling is crucial in the early stages of fin development, potentially influencing the process by regulating other signalling molecules such as Fgf24 and Bmp4.

Non-Classical Effects of FGF23: Molecular and Clinical Features.

This article reviews the role of fibroblast growth factor 23 (FGF23) protein in phosphate metabolism, highlighting its regulation of vitamin D, parathyroid hormone, and bone metabolism. Although it was traditionally thought that phosphate-calcium homeostasis was controlled exclusively by parathyroid hormone (PTH) and calcitriol, pathophysiological studies revealed the influence of FGF23. This protein, expressed mainly in bone, inhibits the renal reabsorption of phosphate and calcitriol formation, mediated by the α-klotho co-receptor. In addition to its role in phosphate metabolism, FGF23 exhibits pleiotropic effects in non-renal systems such as the cardiovascular, immune, and metabolic systems, including the regulation of gene expression and cardiac fibrosis. Although it has been proposed as a biomarker and therapeutic target, the inhibition of FGF23 poses challenges due to its potential side effects. However, the approval of drugs such as burosumab represents a milestone in the treatment of FGF23-related diseases.