Structure and expression of the rat mRNA encoding a novel member of the fibroblast growth factor family

Effects of MEK1/2 inhibitor U0126 on FGF10-enhanced buffalo oocyte maturation in vitro

Fibroblast growth factor 10 (FGF10) plays critical roles in oocyte maturation and embryonic development; however, the specific pathway by which FGF10 promotes in vitro maturation of buffalo oocytes remains elusive. The present study was aimed at investigating the mechanism underlying effects of the FGF10-mediated extracellular regulated protein kinases (ERK) pathway on oocyte maturation and embryonic development in vitro. MEK1/2 (mitogen-activated protein kinase kinase) inhibitor U0126, alone or in combination with FGF10, was added to the maturation culture medium during maturation of the cumulus oocyte complex. Morphological observations, orcein staining, apoptosis detection, and quantitative real-time PCR were performed to evaluate oocyte maturation, embryonic development, and gene expression. U0126 affected oocyte maturation and embryonic development in vitro by substantially reducing the nuclear maturation of oocytes and expansion of the cumulus while increasing the apoptosis of cumulus cells. However, it did not have a considerable effect on glucose metabolism. These findings suggest that blocking the MEK/ERK pathway is detrimental to the maturation and embryonic development potential of buffalo oocytes. Overall, FGF10 may regulate the nuclear maturation of oocytes and cumulus cell expansion and apoptosis but not glucose metabolism through the MEK/ERK pathway. Our findings indicate that FGF10 regulates resumption of meiosis and expansion and survival of cumulus cells via MEK/ERK signaling during in vitro maturation of buffalo cumulus oocyte complexes. Elucidation of the mechanism of action of FGF10 and insights into oocyte maturation should advance buffalo breeding. Further studies should examine whether enhancement of MEK/ERK signaling improves embryonic development in buffalo.

The role of microglial activation on ischemic stroke: Modulation by fibroblast growth factors

Stroke is one of the devastating clinical conditions that causes death and permanent disability. Its occurrence causes the reduction of oxygen and glucose supply, resulting in events such as inflammatory response, oxidative stress, and apoptosis in the brain. Microglia are brain-resident immune cells in the central nervous system (CNS) that exert diverse roles and respond to pathological process after an ischemic insult. The discovery of fibroblast growth factors (FGFs) in mammals, resulted to the findings that they can treat experimental models of stroke in animals effectively. FGFs function as homeostatic factors that control cells and hormones involved in metabolism, and they also regulate the secretion of proinflammatory (M1) and anti-inflammatory (M2) cytokines after stroke. In this review, we outline current evidence of microglia activation in experimental models of stroke focusing on its ability to exacerbate damage or repair tissue. Also, our review sheds light on the pharmacological actions of FGFs on multiple targets to regulate microglial modulation and highlighted their theoretical molecular mechanisms to provide possible therapeutic targets, as well as their limitations for the treatment of stroke. DATA AVAILABILITY: Not applicable.

Fibroblast growth factor 10

Fibroblast growth factor 10 (FGF10) is a major morphoregulatory factor that plays essential signaling roles during vertebrate multiorgan development and homeostasis. FGF10 is predominantly expressed in mesenchymal cells and signals though FGFR2b in adjacent epithelia to regulate branching morphogenesis, stem cell fate, tissue differentiation and proliferation, in addition to autocrine roles. Genetic loss of function analyses have revealed critical requirements for FGF10 signaling during limb, lung, digestive system, ectodermal, nervous system, craniofacial and cardiac development. Heterozygous FGF10 mutations have been identified in human genetic syndromes associated with craniofacial anomalies, including lacrimal and salivary gland aplasia. Elevated Fgf10 expression is associated with poor prognosis in a range of cancers. In addition to developmental and disease roles, FGF10 regulates homeostasis and repair of diverse adult tissues and has been identified as a target for regenerative medicine.

KGF-2 Protects against Lung Ischemia-Reperfusion Injury by Inhibiting Inflammation-Induced Damage to Endothelial Barrier Function

Lung ischemia-reperfusion injury (LIRI), which has a mortality rate of approximately 50%, is a popular topic in critical care research. Keratinocyte growth factor-2 (KGF-2) is secreted by mesenchymal cells, and it is effective in promoting the proliferation, migration, and differentiation of various epithelial cells. To date, however, only a few reports on KGF-2-related regulators in LIRI have been published. In the current study, an LIRI rat model is constructed, and the upregulation of the fibroblast growth factor receptor 2 (FGFR2) is observed in the LIRI rat model. In addition, LIRI induces NLRP1 inflammasome activation in vivo and in vitro, and KGF-2 inhibits LIRI-induced damage to pulmonary microvascular endothelial cells. Mechanistically, KGF-2 inhibits NLRP1 inflammasome and NF-κB activity. KGF-2 inhibition attenuates LIRI injury-induced damage to endothelial integrity. In conclusion, KGF-2 protects against LIRI by inhibiting inflammation-induced endothelial barrier damage.

rhKGF-2 Attenuates Smoke Inhalation Lung Injury of Rats via Activating PI3K/Akt/Nrf2 and Repressing FoxO1-NLRP3 Inflammasome

Smoke inhalation injury is an acute pathological change caused by thermal stimulation or toxic substance absorption through respiratory epithelial cells. This study aims to probe the protective effect and mechanism of recombinant human keratinocyte growth factor 2 (rhKGF-2) against smoke inhalation-induced lung injury (SILI) in rats. The SILI was induced in rats using a smoke exposure model, which were then treated with rhKGF-2. The rat blood was collected for blood-gas analysis, and the levels of inflammatory factors and oxidative stress markers in the plasma were measured. The rat lung tissues were collected. The pathological changes and cell apoptosis were determined by hematoxylin-eosin (HE) staining and TdT-mediated dUTP nick end labeling (TUNEL) assay, and the PI3K/Akt/Nrf2/HO-1/NQO1, and FoxO1-NLRP3 inflammasome expression were verified by western blot (WB). Both of the human alveolar epithelial cell (HPAEpiC) and primary rat alveolar epithelial cell were exposed to lipopolysaccharide (LPS) for making in-vitro alveolar epithelial cell injury model. After treatment with rhKGF-2, GSK2126458 (PI3K inhibitor) and AS1842856 (FoxO1 inhibitor), the cell viability, apoptosis, inflammation, oxidative stress, reactive oxygen species (ROS), PI3K/Akt/Nrf2, HO-1/NQO1, and FoxO1-NLRP3 in HPAEpiC and primary rat alveolar epithelial cell were examined. The data suggested that rhKGF-2 reduced LPS-induced HPAEpiC cell and primary rat alveolar epithelial cell apoptosis and the expression of inflammatory factors and oxidative stress factors. Moreover, rhKGF-2 improved the blood gas and alleviated SILI-induced lung histopathological injury in vivo via repressing inflammation, NLRP3 inflammasome activation and oxidative stress. Mechanistically, rhKGF-2 activated PI3K/Akt pathway, enhanced Nrf2/HO-1/NQO1 expression, and attenuated FoxO1-NLRP3 inflammasome both in vitro and in vivo. However, pharmaceutical inhibition of PI3K/Akt pathway attenuated rhKGF-2-mediated protective effects against SILI, while suppressing FoxO1 promoted rhKGF-2-mediated protective effects. Taken together, this study demonstrated that rhKGF-2 mitigated SILI by regulating the PI3K/Akt/Nrf2 pathway and the FoxO1-NLRP3 axis, which provides new reference in treating SILI.

Characterization in mice of the resident mesenchymal niche maintaining AT2 stem cell proliferation in homeostasis and disease

Resident mesenchymal cells (rMCs defined as Cd31^Neg Cd45^Neg Epcam^Neg ) control the proliferation and differentiation of alveolar epithelial type 2 (AT2) stem cells in vitro. The identity of these rMCs is still elusive. Among them, Axin2^Pos mesenchymal alveolar niche cells (MANCs), which are expressing Fgf7, have been previously described. We propose that an additional population of rMCs, expressing Fgf10 (called rMC-Sca1^Pos Fgf10^Pos ) are equally important to maintain AT2 stem cell proliferation. The alveolosphere model, based on the AT2-rMC co-culture in growth factor-reduced Matrigel, was used to test the efficiency of different rMC subpopulations isolated by FACS from adult murine lung to sustain the proliferation and differentiation of AT2 stem cells. We demonstrate that rMC-Sca1^Pos Fgf10^Pos cells are efficient to promote the proliferation and differentiation of AT2 stem cells. Co-staining of adult lung for Fgf10 mRNA and Sftpc protein respectively, indicate that 28% of Fgf10^Pos cells are located close to AT2 cells. Co-ISH for Fgf7 and Fgf10 indicate that these two populations do not significantly overlap. Gene arrays comparing rMC-Sca1^Pos Axin2^Pos and rMC-Sca1^Pos Fgf10^Pos support that these two cell subsets express differential markers. In addition, rMC function is decreased in obese ob/ob mutant compared to WT mice with a much stronger loss of function in males compared to females. In conclusion, rMC-Sca1^Pos Fgf10^Pos cells play important role in supporting AT2 stem cells proliferation and differentiation. This result sheds a new light on the subpopulations of rMCs contributing to the AT2 stem cell niche in homeostasis and in the context of pre-existing metabolic diseases.

Roles of Fibroblast Growth Factors and Their Therapeutic Potential in Treatment of Ischemic Stroke

Stroke is the leading cause of death worldwide, and its treatment remains a challenge. Complex pathological processes are involved in stroke, which causes a reduction in the supply of oxygen and energy to the brain that triggers subsequent cascade events, such as oxidative stress, inflammatory responses and apoptosis, resulting in brain injury. Stroke is a devastating disease for which there are few treatments, but physical rehabilitation can help improve stroke recovery. Although there are very few treatments for stroke patients, the discovery of fibroblast growth factors (FGFs) in mammals has led to the finding that FGFs can effectively treat stroke in animal models. As presented in this review, FGFs play essential roles by functioning as homeostatic factors and controlling cells and hormones involved in metabolism. They could be used as effective therapeutic agents for stroke. In this review, we will discuss the pharmacological actions of FGFs on multiple targets, including their ability to directly promote neuron survival, enhance angiogenesis, protect against blood-brain barrier (BBB) disruption, and regulate microglial modulation, in the treatment of ischemic stroke and their theoretical mechanisms and actions, as well as the therapeutic potential and limitations of FGFs for the clinical treatment of stroke.

MiR-26b-5p regulates the preadipocyte differentiation by targeting FGF21 in goats

MicroRNAs are a class of highly conserved and widely distributed non-coding RNAs. It is known that miR-26b has a high abundance in adipose tissue and is considered to be an effective regulator of adipogenesis. However, it is unclear whether miR-26b-5p, the product of miR-26b precursor, has the same effect as miR-26b. In the present study, we explored the potential role of miR-26b-5p in preadipocyte differentiation of goats. We found that the expression of miR-26b-5p had dramatic change during goat intramuscular preadipocyte differentiation. Transfection and RT-qPCR revealed that overexpression of miR-26b-5p increased the level of adipogenic marker genes and lipid accumulation in goat preadipocyte, suggesting that miR-26b-5p positively regulates goat preadipocyte differentiation. Furthermore, bioinformatics analysis and dual fluorescein reporter assays were performed to predict and validate the targets of miR-26b-5p. The results showed that miR-26b-5p has a binding site in the 3'UTR of FGF21 and overexpression of miR-26b-5p significantly down-regulated the expression of FGF21 mRNA. Luciferase activity assays confirmed that miR-26b-5p is a positive regulator of goat intramuscular preadipocyte via targeting FGF21. These findings provide reference for further revealing of the regulatory networks of goat fat metabolism and contribute to a better understanding of intramuscular fat deposition in goats.

An Essential Requirement for Fgf10 in Pinna Extension Sheds Light on Auricle Defects in LADD Syndrome

The pinna (or auricle) is part of the external ear, acting to capture and funnel sound toward the middle ear. The pinna is defective in a number of craniofacial syndromes, including Lacrimo-auriculo-dento-digital (LADD) syndrome, which is caused by mutations in FGF10 or its receptor FGFR2b. Here we study pinna defects in the Fgf10 knockout mouse. We show that Fgf10 is expressed in both the muscles and forming cartilage of the developing external ear, with loss of signaling leading to a failure in the normal extension of the pinna over the ear canal. Conditional knockout of Fgf10 in the neural crest fails to recapitulate this phenotype, suggesting that the defect is due to loss of Fgf10 from the muscles, or that this source of Fgf10 can compensate for loss in the forming cartilage. The defect in the Fgf10 null mouse is driven by a reduction in proliferation, rather than an increase in cell death, which can be partially phenocopied by inhibiting cell proliferation in explant culture. Overall, we highlight the mechanisms that could lead to the phenotype observed in LADD syndrome patients and potentially explain the formation of similar low-set and cup shaped ears observed in other syndromes.

Protective effects of FGF10 on neurovascular unit in a rat model of neonatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic (HI) brain injury remains a devastating clinical disease associated with high mortality and lifetime disability. Neonatal HI injury damages the architecture of neurovascular unit (NVU), thus, therapy targeting the NVU may provide effective neuroprotection against HI. This study was designed to investigate whether fibroblast growth factor 10 (FGF10) protected the NVU against HI and afforded observable neuroprotection in a rat model of neonatal HI brain injury. The results showed that FGF10 treatment significantly reduced brain damage post HI, characterized by reduction in brain infarct volume and tissue loss. Further interesting findings showed that FGF10 treatment exerted neuroprotective effects on HI brain injury in neonate rats through protecting the NVU against HI, evidenced by inhibition of neuronal cell apoptosis, suppression of gliosis, and amelioration of blood-brain barrier disruption. Collectively, our study indicates that FGF10 treatment exhibits great potential for protecting NVU against HI and attenuates neonatal brain injury, suggesting a potential novel therapeutic agent to this disease.

Fibroblast Growth Factors: A Controlling Mechanism of Skin Aging

Cutaneous aging is a complex and continuous biological process characterized by cellular and molecular alterations, with progressive reduction of the body's capacity to maintain the homeostasis, senescence, and/or apoptosis of the dermal cells. Fibroblast growth factors (FGF) have elicited studies to evaluate their role of repair and remodeling of the dermis during the skin anti-aging process, since they are regulatory proteins that mediate important signaling pathways and act on cell regeneration and repair processes. FGF acts primarily through binding to tyrosine kinase receptors through the autophosphorylation of their residues, promoting the phosphorylation of serine, threonine, and tyrosine residues of specific target proteins such as Raf-1, MAPK/Erk kinase, and extracellular signal-regulated kinase-1, which are part of the cascade of MAP kinases (mitogen-activated protein kinase). Then, FGF initiate signaling cascades inside the cell, where each kinase activates the following by phosphorylation, resulting in alterations of cellular functions. In addition, the FGF has a relevant role in anti-aging therapy because it is related to collagen and elastin synthesis activation responsible for skin resistance and elasticity, characteristics that are diminished with skin aging. Thus, the present article aims to review several scientific studies that demonstrated the cell signaling involved with the action of FGF on skin aging.

Comparative study on seasonal hair follicle cycling by analysis of the transcriptomes from cashmere and milk goats

Guard hair and cashmere undercoat are developed from primary and secondary hair follicle, respectively. Little is known about the gene expression differences between primary and secondary hair follicle cycling. In this study, we obtained RNA-seq data from cashmere and milk goats grown at four different seasons. We studied the differentially expressed genes (DEGs) during the yearly hair follicle cycling, and between cashmere and milk goats. WNT, NOTCH, MAPK, BMP, TGFβ and Hedgehog signaling pathways were involved in hair follicle cycling in both cashmere and milk goat. However, Milk goat DEGs between different months were significantly more than cashmere goat DEGs, with the largest difference being identified in December. Some expression dynamics were confirmed by quantitative PCR and western blot, and immunohistochemistry. This study offers new information sources related to hair follicle cycling in milk and cashmere goats, which could be applicable to improve the wool production and quality.

Bioactivity Determination of a Therapeutic Recombinant Human Keratinocyte Growth Factor by a Validated Cell-based Bioassay

The therapeutic recombinant human keratinocyte growth factor 1 (rhKGF-1) was approved by the FDA for oral mucositis resulting from hematopoietic stem cell transplantation for hematological malignancies in 2004. However, no recommended bioassay for rhKGF-1 bioactivity has been recorded in the U.S. Pharmacopoeia. In this study, we developed an rhKGF-1-dependent bioassay for determining rhKGF-1 bioactivity based on HEK293 and HaCat cell lines that stably expressed the luciferase reporter driven by the serum response element (SRE) and human fibroblast growth factor receptor (FGFR2) IIIb. A good responsiveness to rhKGF-1 and rhKGF-2 shared by target HEK293/HaCat cell lines was demonstrated. Our stringent validation was completely focused on specificity, linearity, accuracy, precision, and robustness according to the International Council for Harmonization (ICH) Q2 (R1) guidelines, AAPS/FDA Bioanalytical Workshop and the Chinese Pharmacopoeia. We confirmed the reliability of the method in determining rhKGF bioactivity. The validated method is highly timesaving, sensitive, and simple, and is especially valuable for providing information for quality control during the manufacture, research, and development of therapeutic rhKGF.

Fibroblast growth factor 10 (FGF10) promotes the adipogenesis of intramuscular preadipocytes in goat

Fibroblast growth factor 10 (FGF10) is an adipokine that is found to participate in the regulation of adipogenesis. However, its function remains to be elucidated in intramuscular fat (IMF) deposition of goat. The purpose of this study was to explore the role of FGF10 in goat IMF deposition. Here, we investigated the expression of FGF10 in goat intramuscular adipocytes inducing 0, 2, 4, 6 and 8 days. Effect of FGF10 on adipogenesis was investigated by gaining and losing function of FGF10 in vitro. And then, we examined several lipid metabolism-related genes, including peroxisome proliferator activated receptor γ (PPARγ), sterol regulatory element binding protein 1 (SREBP1), preadipocyte factor-1 (Pref-1), CCAAT/enhancer binding protein-α (C/EBPα) and CCAAT/enhancer binding protein-β (C/EBPβ), as well as, Krüppel-like factor (KLF) family. We found that the sharp expression of FGF10 appeared at 2 days. Overexpression of FGF10 mediated by adenovirus promotes lipid accumulation, accompanied by up-regulating of LPL and C/EBPα with the down-regulating of C/EBPβ. Conversely, the expression of LPL, C/EBPα and SREBP1 was significantly decreased by the siRNAs of FGF10. Meanwhile, we showed that FGF10 regulated the expression of many KLFs members and interacted synergistically or antagonistically with them. Thus, our results demonstrated a key role of FGF10 as a positively factor in the regulation of adipogenic differentiation of intramuscular preadipocyte in goat.

A miR-327-FGF10-FGFR2-mediated autocrine signaling mechanism controls white fat browning

Understanding the molecular mechanisms regulating beige adipocyte formation may lead to the development of new therapies to combat obesity. Here, we report a miRNA-based autocrine regulatory pathway that controls differentiation of preadipocytes into beige adipocytes. We identify miR-327 as one of the most downregulated miRNAs targeting growth factors in the stromal-vascular fraction (SVF) under conditions that promote white adipose tissue (WAT) browning in mice. Gain- and loss-of-function experiments reveal that miR-327 targets FGF10 to prevent beige adipocyte differentiation. Pharmacological and physiological β-adrenergic stimulation upregulates FGF10 levels and promotes preadipocyte differentiation into beige adipocytes. In vivo local delivery of miR-327 to WATs significantly compromises the beige phenotype and thermogenesis. Contrarily, systemic inhibition of miR-327 in mice induces browning and increases whole-body metabolic rate under thermoneutral conditions. Our data provide mechanistic insight into an autocrine regulatory signaling loop that regulates beige adipocyte formation and suggests that the miR-327-FGF10-FGFR2 signaling axis may be a therapeutic targets for treatment of obesity and metabolic diseases.

Neuron and microglia/macrophage-derived FGF10 activate neuronal FGFR2/PI3K/Akt signaling and inhibit microglia/macrophages TLR4/NF-κB-dependent neuroinflammation to improve functional recovery after spinal cord injury

Therapeutics used to treat central nervous system (CNS) injury were designed to repair neurites and inhibit cell apoptosis. Previous studies have shown that neuron-derived FGF10 exerts potential neuroprotective effects after cerebral ischemia injury. However, little is known about the role of endogenous FGF10 in the recovery process after spinal cord injury (SCI). In this study, we found that FGF10 is mainly produced by neuron and microglia/macrophages, and its expression is increased after SCI. Exogenous treatment of FGF10 improved functional recovery after injury by reducing apoptosis, as well as repairing neurites via FGFR2/PI3K/Akt pathway. On another hand, inhibiting the PI3K/Akt pathway with LY294002 partially reversed the therapeutic effects of FGF10. In addition, small interfering RNA knockdown of FGFR2 suppressed PI3K/Akt pathway activation by FGF10 and abolished its anti-apoptotic and neurite repair effects in vitro. Furthermore, FGF10 treatment inhibited the activation and proliferation of microglia/macrophages through regulation of TLR4/NF-κB pathway, and attenuated the release of pro-inflammatory cytokines after SCI. Thus, the increased expression of FGF10 after acute SCI is an endogenous self-protective response, suggesting that FGF10 could be a potential treatment for CNS injury.

FGF and EDA pathways control initiation and branching of distinct subsets of developing nasal glands

Hypertrophy, hyperplasia and altered mucus secretion from the respiratory submucosal glands (SMG) are characteristics of airway diseases such as cystic fibrosis, asthma and chronic bronchitis. More commonly, hyper-secretion of the nasal SMGs contributes to allergic rhinitis and upper airway infection. Considering the role of these glands in disease states, there is a significant dearth in understanding the molecular signals that regulate SMG development and patterning. Due to the imperative role of FGF signalling during the development of other branched structures, we investigated the role of Fgf10 during initiation and branching morphogenesis of murine nasal SMGs. Fgf10 is expressed in the mesenchyme around developing SMGs while expression of its receptor Fgfr2 is seen within glandular epithelial cells. In the Fgf10 null embryo, Steno's gland and the maxillary sinus gland were completely absent while other neighbouring nasal glands showed normal duct elongation but defective branching. Interestingly, the medial nasal glands were present in Fgf10 homozygotes but missing in Fgfr2b mutants, with expression of Fgf7 specifically expressed around these developing glands, indicating that Fgf7 might compensate for loss of Fgf10 in this group of glands. Intriguingly the lateral nasal glands were only mildly affected by loss of FGF signalling, while these glands were missing in Eda mutant mice, where the Steno's and maxillary sinus gland developed as normal. This analysis reveals that regulation of nasal gland development is complex with different subsets of glands being regulated by different signalling pathways. This analysis helps shed light on the nasal gland defects observed in patients with hypohidrotic ectodermal dysplasia (HED) (defect EDA pathway) and LADD syndrome (defect FGFR2b pathway).

Interrogation of a lacrimo-auriculo-dento-digital syndrome protein reveals novel modes of fibroblast growth factor 10 (FGF10) function

Heterozygous mutations in the gene encoding fibroblast growth factor 10 (FGF10) or its cognate receptor, FGF-receptor 2 IIIb result in two human syndromes - LADD (lacrimo-auriculo-dento-digital) and ALSG (aplasia of lacrimal and salivary glands). To date, the partial loss-of-FGF10 function in these patients has been attributed solely to perturbed paracrine signalling functions between FGF10-producing mesenchymal cells and FGF10-responsive epithelial cells. However, the functioning of a LADD-causing G138E FGF10 mutation, which falls outside its receptor interaction interface, has remained enigmatic. In the present study, we interrogated this mutation in the context of FGF10's protein sequence and three-dimensional structure, and followed the subcellular fate of tagged proteins containing this or other combinatorial FGF10 mutations, in vitro We report that FGF10 harbours two putative nuclear localization sequences (NLSs), termed NLS1 and NLS2, which individually or co-operatively promote nuclear translocation of FGF10. Furthermore, FGF10 localizes to a subset of dense fibrillar components of the nucleolus. G138E falls within NLS1 and abrogates FGF10's nuclear translocation whilst attenuating its progression along the secretory pathway. Our findings suggest that in addition to its paracrine roles, FGF10 may normally play intracrine role/s within FGF10-producing cells. Thus, G138E may disrupt both paracrine and intracrine function/s of FGF10 through attenuated secretion and nuclear translocation, respectively.

Geranylgeranyl Diphosphate Synthase Modulates Fetal Lung Branching Morphogenesis Possibly through Controlling K-Ras Prenylation

G proteins play essential roles in regulating fetal lung development, and any defects in their expression or function (eg, activation or posttranslational modification) can lead to lung developmental malformation. Geranylgeranyl diphosphate synthase (GGPPS) can modulate protein prenylation that is required for protein membrane-anchoring and activation. Here, we report that GGPPS regulates fetal lung branching morphogenesis possibly through controlling K-Ras prenylation during fetal lung development. GGPPS was continuously expressed in lung epithelium throughout whole fetal lung development. Specific deletion of geranylgeranyl diphosphate synthase 1 (Ggps1) in lung epithelium during fetal lung development resulted in neonatal respiratory distress syndrome-like disease. The knockout mice died at postnatal day 1 of respiratory failure, and the lungs showed compensatory pneumonectasis, pulmonary atelectasis, and hyaline membranes. Subsequently, we proved that lung malformations in Ggps1-deficient mice resulted from the failure of fetal lung branching morphogenesis. Further investigation revealed Ggps1 deletion blocked K-Ras geranylgeranylation and extracellular signal-related kinase 1 or 2/mitogen-activated protein kinase signaling, which in turn disturbed fibroblast growth factor 10 regulation on fetal lung branching morphogenesis. Collectively, our data suggest that GGPPS is essential for maintaining fetal lung branching morphogenesis, which is possibly through regulating K-Ras prenylation.

Fibroblast Growth Factor-10 (FGF-10) Mobilizes Lung-resident Mesenchymal Stem Cells and Protects Against Acute Lung Injury

FGF-10 can prevent or reduce lung specific inflammation due to traumatic or infectious lung injury. However, the exact mechanisms are poorly characterized. Additionally, the effect of FGF-10 on lung-resident mesenchymal stem cells (LR-MSCs) has not been studied. To better characterize the effect of FGF-10 on LR-MSCs, FGF-10 was intratracheally delivered into the lungs of rats. Three days after instillation, bronchoalveolar lavage was performed and plastic-adherent cells were cultured, characterized and then delivered therapeutically to rats after LPS intratracheal instillation. Immunophenotyping analysis of FGF-10 mobilized and cultured cells revealed expression of the MSC markers CD29, CD73, CD90, and CD105, and the absence of the hematopoietic lineage markers CD34 and CD45. Multipotency of these cells was demonstrated by their capacity to differentiate into osteocytes, adipocytes, and chondrocytes. Delivery of LR-MSCs into the lungs after LPS injury reduced the inflammatory response as evidenced by decreased wet-to-dry ratio, reduced neutrophil and leukocyte recruitment and decreased inflammatory cytokines compared to control rats. Lastly, direct delivery of FGF-10 in the lungs of rats led to an increase of LR-MSCs in the treated lungs, suggesting that the protective effect of FGF-10 might be mediated, in part, by the mobilization of LR-MSCs in lungs.

Neuron-derived FGF10 ameliorates cerebral ischemia injury via inhibiting NF-κB-dependent neuroinflammation and activating PI3K/Akt survival signaling pathway in mice

FGF10 is a member of fibroblast growth factors (FGFs). We previously showed that FGF10 protects neuron against oxygen-glucose deprivation injury in vitro; however, the effect of FGF10 in ischemic stroke in vivo is unknown. In the present study, we showed that FGF10 was mainly expressed in neurons but not astrocytes, and detected FGF10 in mouse cerebrospinal fluid. The FGF10 levels in neurons culture medium and cell lysate were much higher than those in astrocytes. FGF10 expression in brain tissue and FGF10 level in CSF were increased in mouse middle cerebral artery occlusion (MCAO) model. Administration of FGF10 into lateral cerebroventricle not only decreased MCAO-induced brain infarct volume and neurological deficit, but also reduced the number of TUNEL-positive cells and activities of Caspases. Moreover, FGF10 treatment depressed the triggered inflammatory factors (TNF-α and IL-6) and NF-κB signaling pathway, and increased phosphorylation of PI3K/Akt signaling pathway. Blockade of PI3K/Akt signaling pathway by wortmannin and Akt1/2-kinase inhibitor, partly compromised the neuroprotection of FGF10. However, blockade of PI3K/Akt signaling pathway did not impair the anti-inflammation action of FGF10. Collectively, our results demonstrate that neuron-derived FGF10 ameliorates cerebral ischemia injury via inhibiting NF-κB-dependent neuroinflammation and activating PI3K/Akt survival signaling pathway in mice.

Fibroblast growth factors, old kids on the new block

The fibroblast growth factors (FGFs) are a family of cell intrinsic regulatory peptides that control a broad spectrum of cellular activities. The family includes canonic FGFs that elicit their activities by activating the FGF receptor (FGFR) tyrosine kinase and non-canonic members that elicit their activities intracellularly and via FGFR-independent mechanisms. The FGF signaling axis is highly complex due to the existence of multiple isoforms of both ligands and receptors, as well as cofactors that include the chemically heterogeneous heparan sulfate (HS) cofactors, and in the case of endocrine FGFs, the Klotho coreceptors. Resident FGF signaling controls embryonic development, maintains tissue homeostasis, promotes wound healing and tissue regeneration, and regulates functions of multiple organs. However, ectopic or aberrant FGF signaling is a culprit for various diseases, including congenital birth defects, metabolic disorder, and cancer. The molecular mechanisms by which the specificity of FGF signaling is achieved remain incompletely understood. Since its application as a druggable target has been gradually recognized by pharmaceutical companies and translational researchers, understanding the determinants of FGF signaling specificity has become even more important in order to get into the position to selectively suppress a particular pathway without affecting others to minimize side effects.

Keratinocyte growth factor-2 inhibits bacterial infection with Pseudomonas aeruginosa pneumonia in a mouse model

To determine protective effects of concurrent administration of Keratinocyte growth factor-2 (KGF-2) with Pseudomonas aeruginosa (P. aeruginosa) inoculation on the induced pneumonia. KGF-2 (5 mg/kg) was concurrently administered into the left lobe of 55 mice with P. aeruginosa PAO1 (5 × 10(6) CFU, half-lethal dose); 55 mice in the control group were concurrently administered PBS with the PAO1. We detected and analyzed: body temperature; amount of P. aeruginosa in homogenates; count of total number of nucleated cells and of mononuclear macrophages; protein concentration in bronchoalveolar lavage fluid (BALF); lung wet-to-dry weight ratio; cytokines in BALF and blood; and lung morphology. To study survival rate, concurrent administration of KGF-2 (experimental group) versus PBS (control) with a lethal dose of PAO1 (1 × 10(7) CFU was performed, and survivorship was documented for 7 days post-inoculation. The bacterial CFU in lung homogenates was significantly decreased in the KGF-2 group compared to the control group. There were significantly more mononuclear macrophages in the BALF from the KGF-2 group than from the control group (p < 0.05). KGF-2 increased the surfactant protein and GM-CSF mRNA in lung at 6 h and 72 h after inoculation. Significant reduction of lung injury scores, protein concentrations, lung wet-to-dry weight ratio, and IL-6 and TNF-α levels was noted in the KGF-2 treated rats at 72 h after inoculation (p < 0.05). The 7-day survival rate of the KGF-2 group was significantly higher than that of the control group (p < 0.05). Concurrent administration of KGF-2 facilitates the clearance of P. aeruginosa from the lungs, attenuates P. aeruginosa-induced lung injury, and extends the 7-day survival rate in mice model with P. aeruginosa pneumonia.

FGF10: A multifunctional mesenchymal-epithelial signaling growth factor in development, health, and disease

The FGF family comprises 22 members with diverse functions in development and health. FGF10 specifically activates FGFR2b in a paracrine manner with heparan sulfate as a co-factor. FGF10and FGFR2b are preferentially expressed in the mesenchyme and epithelium, respectively. FGF10 is a mesenchymal signaling molecule in the epithelium. FGF10 knockout mice die shortly after birth due to the complete absence of lungs as well as fore- and hindlimbs. FGF10 is also essential for the development of multiple organs. The phenotypes of Fgf10 knockout mice are very similar to those of FGFR2b knockout mice, indicating that FGF10 acts as a ligand that is specific to FGFR2b in mouse multi-organ development. FGF10 also plays roles in epithelial-mesenchymal transition, the repair of tissue injury, and embryonic stem cell differentiation. In humans, FGF10 loss-of-function mutations result in inherited diseases including aplasia of lacrimal and salivary gland, lacrimo-auriculo-dento-digital syndrome, and chronic obstructive pulmonary disease. FGF10 is also involved in the oncogenicity of pancreatic and breast cancers. Single nucleotide polymorphisms in FGF10 are also potential risk factors for limb deficiencies, cleft lip and palate, and extreme myopia. These findings indicate that FGF10 is a crucial paracrine signal from the mesenchyme to epithelium for development, health, and disease.

Enhanced Expression of Fibroblast Growth Factor Receptor 3 IIIc Promotes Human Esophageal Carcinoma Cell Proliferation

Deregulated expression of fibroblast growth factor receptors (FGFRs) and their ligands plays critical roles in tumorigenesis. The gene expression of an alternatively spliced isoforms of FGFR3, FGFR3IIIc, was analyzed by RT-PCR in samples from patients with esophageal carcinoma (EC), including esophageal squamous cell carcinoma (ESCC) and adenocarcinoma (EAC). The incidence of FGFR3IIIc was higher in EC [12/16 (75%); p=0.073] than in non-cancerous mucosa (NCM) [6/16 (38%)]. Indeed, an immunohistochemical analysis of early-stage ESCC showed that carcinoma cells expressing FGFR3IIIc stained positively with SCC-112, a tumor marker, and Ki67, a cell proliferation marker, suggesting that the expression of FGFR3IIIc promotes cell proliferation. We used EC-GI-10 cells endogenously expressing FGFR3IIIc as a model of ESCC to provide mechanistic insight into the role of FGFR3IIIc in ESCC. The knockdown of endogenous FGFR3 using siRNA treatment significantly abrogated cell proliferation and the overexpression of FGFR3IIIc in cells with enhanced cell proliferation. EC-GI-10 cells and ESCC from patients with EC showed endogenous expression of FGF2, a specific ligand for FGFR3IIIc, suggesting that the upregulated expression of FGFR3IIIc may create autocrine FGF signaling in ESCC. Taken together, FGFR3IIIc may have the potential to be an early-stage tumor marker and a molecular target for ESCC therapy.

Role of fibroblast growth factors in organ regeneration and repair

In its broad sense, regeneration refers to the renewal of lost cells, tissues or organs as part of the normal life cycle (skin, hair, endometrium etc.) or as part of an adaptive mechanism that organisms have developed throughout evolution. For example, worms, starfish and amphibians have developed remarkable regenerative capabilities allowing them to voluntarily shed body parts, in a process called autotomy, only to replace the lost parts afterwards. The bizarre myth of the fireproof homicidal salamander that can survive fire and poison apple trees has persisted until the 20th century. Salamanders possess one of the most robust regenerative machineries in vertebrates and attempting to draw lessons from limb regeneration in these animals and extrapolate the knowledge to mammals is a never-ending endeavor. Fibroblast growth factors are potent morphogens and mitogens that are highly conserved among the animal kingdom. These growth factors play key roles in organogenesis during embryonic development as well as homeostatic balance during postnatal life. In this review, we provide a summary about the current knowledge regarding the involvement of fibroblast growth factor signaling in organ regeneration and repair. We also shed light on the use of these growth factors in previous and current clinical trials in a wide array of human diseases.

Expression of bioactive recombinant human fibroblast growth factor 10 in Carthamus tinctorius L. seeds

Fibroblast growth factor 10 (FGF10) is a member of the FGF superfamily. It exhibits diverse biological functions, and is extensively used for fundamental research and clinical applications involving hair growth, tissue repair, and burn wounds. Oil bodies, obtained from oil seeds, have been exploited for a variety of biotechnology applications. The use of oil bodies reduces purification steps and costs associated with the production of heterogonous proteins. Here, recombinant human FGF10 (rhFGF10) was expressed in safflower (Carthamus tinctorius L.) seeds using oilbody-oleosin technology. A plant expression vector, pOTBar-oleosin-rhFGF10, was constructed and introduced into safflower using Agrobacterium tumefaciens transformation, and mature safflower plants were obtained by grafting. Oleosin-rhFGF10 was successfully transformed and expressed in safflower seeds and inherited to the T₃ generation. Moreover, MTT assays demonstrated that oil bodies expressed oleosin-FGF10 had a dose-dependent effect on cellular proliferation. In conclusion, this may provide a method of producing oleosin-rhFGF10, and help us meet the increasing pharmacological demands for the protein.

Fibroblast growth factor 10 protects neuron against oxygen-glucose deprivation injury through inducing heme oxygenase-1

Fibroblast growth factors (FGFs) are a family of structurally related heparin-binding proteins with diverse biological functions. FGFs participate in mitogenesis, angiogenesis, cell proliferation, development, differentiation and cell migration. Here, we investigated the potential effect of FGF10, a member of FGFs, on neuron survival in oxygen-glucose deprivation (OGD) model. In primary cultured mouse cortical neurons upon OGD, FGF10 treatment (100 and 1000 ng/ml) attenuated the decrease of cell viability and rescued the LDH release. Tuj-1 immunocytochemistry assay showed that FGF10 promoted neuronal survival. Apoptosis assay with Annexin V+PI by flow cytometry demonstrated that FGF10 treatment reduced apoptotic cell proportion. Moreover, immunoblotting showed that FGF10 alleviated the cleaved caspase-3 upregulation caused by OGD. FGF10 treatment also depressed the OGD-induced increase of caspase-3, -8 and -9 activities. At last, we found FGF10 triggered heme oxygenase-1 (HO-1) protein expression rather than hypoxia-inducible factor-1 (HIF-1), AMP-activated protein kinase (AMPK) signaling and extracellular signal-regulated kinases 1/2 (ERK1/2) signaling. Knockdown of HO-1 by siRNA partly abolished the neuroprotection of FGF10 in OGD model. In summary, our observations provide the first evidence for the neuroprotective function of FGF10 against ischemic neuronal injury and suggest that FGF10 may be a promising agent for treatment of ischemic stroke.

Protective effects of keratinocyte growth factor-2 on ischemia-reperfusion-induced lung injury in rats

Ischemia-reperfusion (I/R) is a common cause to compromise tissue injury via endothelial and epithelial barrier dysfunction and damage. Keratinocyte growth factor (KGF)-2 could play an important role in the repair of alveolar epithelial damage and maintain the capillary barrier function. The present study aimed to investigate the potential effects of KGF-2 on I/R-induced lung injury in rats and the related mechanisms. KGF-2 (2.5-10 mg/kg) was administered intratracheally in rats 3 days before the left lobe with ischemia for 60 minutes followed by reperfusion for 180 minutes. Lung injury was evaluated by measuring lung morphology, blood gas analysis, total cell number, and protein concentration in the bronchoalveolar lavage fluid. The protective effects of KGF-2 on human pulmonary microvascular endothelial cells and related mechanisms were evaluated. Pretreatment with KGF-2 significantly prevented I/R-induced lung edema, inflammatory cell infiltration, protein exudation, and the release of inflammatory cytokines in rats, or I/R-induced endothelial cell apoptosis, migration, and barrier dysfunction. Phosphoinositide 3-kinase or epidermal growth factor receptor inhibitors attenuated the protective effect of KGF-2 in endothelial cells. Our results evidence that the local administration of KGF-2 may be an alternative to prophylactic or adjunct drug therapies for I/R-induced lung injury.

Keratinocyte growth factor-2 is protective in lipopolysaccharide-induced acute lung injury in rats

Keratinocyte growth factor-2 (KGF-2) plays a key role in lung development, but its role in acute lung injury has not been well characterized. Lipopolysaccharide instillation caused acute lung injury, which significantly elevated lung wet-to-dry weight ratio, protein and neutrophils in bronchoalveolar lavage fluid (BALF), inhibited surfactant protein A and C expression in lung tissue, and increased pathological injury. Pretreatment with KGF-2 improved the above lung injury parameters, partially restored surfactant protein A and C expression, and KGF-2 given 2-3 days before LPS challenge showed maximum lung injury improvement. Pretreatment with KGF-2 also markedly reduced the levels of TNF-α, MIP-2, IL-1β and IL-6 in BALF and the levels of IL-1β and IL-6 in lung tissue. Histological analysis showed there was increased proliferation of alveolar type II epithelial cells in lung parenchyma, which reached maximal 2 days after KGF-2 instillation. Intratracheal administration of KGF-2 attenuates lung injury induced by LPS, suggesting KGF-2 may be potent in the intervention of acute lung injury.

Keratinocyte growth factor-2 intratracheal instillation significantly attenuates ventilator-induced lung injury in rats

Preservation or restoration of normal alveolar epithelial barrier function is crucial for pulmonary oedema resolution. Keratinocyte growth factor-2 (KGF-2), a potent epithelial cell mitogen, may have a role in preventing ventilator-induced lung injury (VILI), which occurs frequently in mechanically ventilated patients. The aim of the study was to test the role of KGF-2 in VILI in rats. Forty healthy adult male Sprague-Dawley rats were randomly allocated into four groups, where rats in Groups HVZP (high-volume zero positive end-expiratory pressure) and HVZP+KGF-2 were given intratracheally equal PBS and 5 mg/kg KGF-2 72 hrs before 4 hrs HVZP ventilation (20 ml/kg), respectively, while PBS and KGF-2 were administered in the same manner in Groups Control and KGF-2, which underwent tracheotomy only with spontaneous breathing. Inflammatory cytokines (tumour necrosis factor-α, macrophage inflammatory protein 2), neutrophil and total protein levels in bronchoalveolar lavage fluid and surfactant protein mRNA expression in lung tissue were detected; the number of alveolar type II cells, lung water content and lung morphology were also evaluated. The results indicate that pre-treatment with KGF-2 showed dramatic improvement in lung oedema and inflammation compared with HVZP alone, together with increased surfactant protein mRNA and alveolar type II cells. Our results suggest that KGF-2 might be considered a promising prevention for human VILI or other acute lung injury diseases.

FGF10 Signaling differences between type I pleuropulmonary blastoma and congenital cystic adenomatoid malformation

Background

Type I pleuropulmonary blastoma (PPB) and congenital cystic adenomatoid malformation of the lung (CCAM) are cystic lung diseases of childhood. Their clinical and radiological presentations are often similar, and pathologic discrimination remains difficult in many cases. As a consequence, type I PPB and CCAM are frequently confused, leading to delayed adequate management for type I PPB. Recent studies have suggested a role for fibroblast growth factor (FGF) 10 signal pathway in CCAM pathogenesis. The objective of our study was to determine whether FGF10 signaling differs between CCAM and type I PPB.

Methods

Immunohistochemical studies were performed for expression of FGF10, its receptor FGFR2b, and its inhibitor sonic hedgehog (SHH) in focal type I PPB (n=6), CCAM type I (n=7), CCAM type II (n=7), and control lungs (n=5).

Results

FGF10, FGFR2b, and SHH expressions differed markedly between type I PPB and both types of CCAM. Type I and type II CCAM cystic walls expressed FGF10, FGFR2b, and SHH, whereas staining was absent or poor in type I PBB cystic walls. Expression of FGF10, FGFR2b, and SHH did not differ between CCAM cystic walls and control airway walls.

Conclusions

These findings show that immunohistochemistry with FGF10, FGFR2b, or SHH could be useful in differentiating CCAM from type I PPB, when a child presents with a focal cystic lung lesion. The absence of strong expression of FGF10, FGFR2b, and/or SHH makes the diagnosis of CCAM very doubtful.

Expression and functions of fibroblast growth factor 10 in the mouse mammary gland

Fibroblast growth factor 10 (FGF10) is important as a mesenchymal mediator of epithelial growth and morphogenesis. In this study, the expression and localization of the FGF10 protein were detected by laser scanning confocal microscopy during mouse postnatal mammary gland development. Mammary explants were cultured to investigate the functions of FGF10. The results revealed that FGF10 localizes mainly in the mesenchyme near the ductal epithelial cells and the alveolar epithelial cells of the mammary gland. Peak FGF10 expression levels were observed at lactation day 10. FGF10 induced FGFR2-IIIb expression in the mammary epithelium, except in virgin or pregnant mice. FGF10 promoted the proliferation of mammary gland epithelial cells and reduced apoptosis. FGF10 is important during the mouse mammary gland growth, development, and reconstruction, and its effects are mediated by FGFR2-IIIb.

Potential clinical application of KGF-2 (FGF-10) for acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is an acute life-threatening form of hypoxemic respiratory failure with a high mortality rate, and there is still a great need for more effective therapies for such a severe and lethal disease. Dysfunction of endothelial and epithelial barriers is one of the most important mechanisms in hypoxia-associated ALI/ARDS. The acceleration of the epithelial repair process in the injured lung may provide an effective therapeutic target. KGF-2, a potent alveolar epithelial cell mitogen, plays an important role in organ morphogenesis and epithelial differentiation, and modulates a variety of mechanisms recognized to be important in alveolar repair and resolution in ALI/ARDS. Preclinical and clinical studies have suggested that KGF-2 may be the candidate of novel therapies for alveolar epithelial damage during ALI/ARDS.

Hairy tale of signaling in hair follicle development and cycling

Hair follicles (HFs) is an appendage from the vertebrate skin epithelium, and is critical for environmental sensing, animal appearance, and body heat maintenance. HFs arise from the embryonic ectoderm and regenerate cyclically during adult life. Distinct morphological and functional stages from development through homeostasis have been extensively studied for the past decades to dissect the critical molecular mechanisms. Accumulating work suggests that different signaling cascades, such as Wnt, Bmp, Shh, and Notch, together with specific combinations of transcription factors are at work at different stages. Here we provide a comprehensive review of mouse genetics studies, which include lineage tracing along with knockout and over-expression of core genes from key signaling pathways, to paint an updated view of the molecular regulatory network that govern each stage of hair follicle development and adult cycling.

FGF10 inhibits dominant follicle growth and estradiol secretion in vivo in cattle

Fibroblast growth factors (FGFs) are involved in paracrine control of follicle development. It was previously demonstrated that FGF10 decreases estradiol (E2) secretion in granulosa cell culture and that theca cell FGF10 mRNA expression is decreased in healthy follicles from abattoir ovaries. The main objectives of this study were to evaluate FGF10 and FGFR2b mRNA expression during follicular development in vivo, to evaluate the effect of FGF10 on follicle growth using Bos taurus taurus cows as a model, and to gain more insight into the mechanisms through which FGF10 inhibits steroidogenesis. Messenger RNA encoding both FGF10 and FGFR2b (main FGF10 receptor) was significantly more expressed in subordinate follicles (SFs) than in dominant follicles (DFs). The intrafollicular injection of FGF10 into the largest growing follicle at 7–8 mm in diameter interrupted the DF growth in a dose-dependent manner (11±0.4, 8.3±1 and 5.9±0.3 mm for 0, 0.1, and 1 μg/ml FGF10, respectively, at 72 h after treatment; P<0.05). In a third experiment, follicles were obtained 24 h after FGF10 (1 μg/ml) or PBS treatment through ovariectomy. In theca cells, FGF10 treatment did not affect mRNA encoding steroidogenic enzymes, LHCGR and IGFBPs, but significantly upregulated FGF10 mRNA expression. The expression of CYP19A1 mRNA in granulosa cells was downregulated by FGF10 treatment, which was accompanied by a 50-fold decrease in E2 production, and decreased cyclin D2 mRNA. These results have shown that FGF10 and its receptor FGFR2b are more expressed in SFs and provide solid in vivo evidence that FGF10 acts as an important regulator of follicular growth in cattle.

Exogenous fibroblast growth factor-10 induces cystic lung development with altered target gene expression in the presence of heparin in cultures of embryonic rat lung

OBJECTIVES

Signaling by fibroblast growth factor (FGF) receptor (FGFR) 2IIIb regulates branching morphogenesis in the mammalian lung. FGFR2IIIb is primarily expressed in epithelial cells, whereas its ligands, FGF-10 and keratinocyte growth factor (KGF; FGF-7), are expressed in mesenchymal cells. FGF-10 null mice lack lungs, whereas KGF null animals have normal lung development, indicating that FGF-10 regulates lung branching morphogenesis. In this study, we determined the effects of FGF-10 on lung branching morphogenesis and accompanying gene expression in cultures of embryonic rat lungs.

METHODS

Embryonic day 14 rat lungs were cultured with FGF-10 (0-250 ng/ml) in the absence or presence of heparin (30 ng/ml) for 4 days. Gene expression profiles were analyzed by Affymetrix microchip array including pathway analysis. Some of these genes, functionally important in FGF-10 signaling, were further analyzed by Northern blot, real-time PCR, in situ hybridization and immunohistochemistry.

RESULTS

Exogenous FGF-10 inhibited branching and induced cystic lung growth only in cultures containing heparin. In total, 252 upregulated genes and 164 downregulated genes were identified, and these included Spry1 (Sprouty-1), Spry2 (Sprouty-2), Spred-1, Bmp4 (bone morphogenetic protein-4, BMP-4), Shh (sonic hedgehog, SHH), Pthlh (parathyroid hormone-related protein, PTHrP), Dusp6 (MAP kinase phosphatase-3, MKP-3) and Clic4 (chloride intracellular channel-4, CLIC-4) among the upregulated genes and Igf1 (insulin-like growth factor-1, IGF-1), Tcf21 (POD), Gyg1 (glycogenin 1), Sparc (secreted protein acidic and rich in cysteine, SPARC), Pcolce (procollagen C-endopeptidase enhancer protein, Pro CEP) and Lox (lysyl oxidase) among the downregulated genes. Gsk3β and Wnt2, which are involved in canonical Wnt signaling, were up- and downregulated, respectively.

CONCLUSIONS

Unlike FGF-7, FGF-10 effects on lung branching morphogenesis are heparin-dependent. Sprouty-2, BMP-4, SHH, IGF-1, SPARC and POD are known to regulate branching morphogenesis; however, potential roles of CLIC-4 and MKP-3 in lung branching morphogenesis remain to be investigated. FGF-10 may also function in regulating branching morphogenesis or inducing cystic lung growth by inhibiting Wnt2/β-catenin signaling.

Birthdating studies reshape models for pituitary gland cell specification

The intermediate and anterior lobes of the pituitary gland are derived from an invagination of oral ectoderm that forms Rathke's pouch. During gestation proliferating cells are enriched around the pouch lumen, and they appear to delaminate as they exit the cell cycle and differentiate. During late mouse gestation and the postnatal period, anterior lobe progenitors re-enter the cell cycle and expand the populations of specialized, hormone-producing cells. At birth, all cell types are present, and their localization appears stratified based on cell type. We conducted a birth dating study of Rathke's pouch derivatives to determine whether the location of specialized cells at birth is correlated with the timing of cell cycle exit. We find that all of the anterior lobe cell types initiate differentiation concurrently with a peak between e11.5 and e13.5. Differentiation of intermediate lobe melanotropes is delayed relative to anterior lobe cell types. We discovered that specialized cell types are not grouped together based on birth date and are dispersed throughout the anterior lobe. Thus, the apparent stratification of specialized cells at birth is not correlated with cell cycle exit. Thus, the currently popular model of cell specification, dependent upon timing of extrinsic, directional gradients of signaling molecules, needs revision. We propose that signals intrinsic to Rathke's pouch are necessary for cell specification between e11.5 and e13.5 and that cell-cell communication likely plays an important role in regulating this process.

Developmental origins of precocial forelimbs in marsupial neonates

Marsupial mammals are born in an embryonic state, as compared with their eutherian counterparts, yet certain features are accelerated. The most conspicuous of these features are the precocial forelimbs, which the newborns use to climb unaided from the opening of the birth canal to the teat. The developmental mechanisms that produce this acceleration are unknown. Here we show that heterochronic and heterotopic changes early in limb development contribute to forelimb acceleration. Using Tbx5 and Tbx4 as fore- and hindlimb field markers, respectively, we have found that, compared with mouse, both limb fields arise notably early during opossum development. Patterning of the forelimb buds is also accelerated, as Shh expression appears early relative to the outgrowth of the bud itself. In addition, the forelimb fields and forelimb myocyte allocation are increased in size and number, respectively, and migration of the spinal nerves into the forelimb bud has been modified. This shift in the extent of the forelimb field is accompanied by shifts in Hox gene expression along the anterior-posterior axis. Furthermore, we found that both fore- and hindlimb fields arise gradually during gastrulation and extension of the embryonic axis, in contrast to the appearance of the limb fields in their entirety in all other known cases. Our results show a surprising evolutionary flexibility in the early limb development program of amniotes and rule out the induction of the limb fields by mature structures such as the somites or mesonephros.

cAMP and fibroblast growth factor 2 regulate bone sialoprotein gene expression in human prostate cancer cells

Bone sialoprotein (BSP) is a noncollagenous protein of the extracellular matrix in mineralized connective tissues that has been implicated in the nucleation of hydroxyapatite. Forskolin (FSK), an activator of adenylate cyclase, increased the intracellular cAMP level, which stimulates the proliferation and differentiation of osteoblasts. Fibroblast growth factor 2 (FGF2) is a potent mitogen in many cell types, including osteoblasts. In human prostate cancer DU145 cells, FSK (1 μM) and FGF2 (10 ng/ml) increased BSP and Runx2 mRNA and protein levels at 3 and 12h, respectively. Transient transfection analyses were performed using chimeric constructs of the human BSP gene promoter linked to a luciferase reporter gene. Treatment of DU145 cells with FSK (1 μM) and FGF2 (10 ng/ml) increased the luciferase activities of constructs between -60LUC to -927LUC and -108LUC to -927LUC, including the human BSP gene promoter. Effects of FSK and FGF2 abrogated in constructs included 2bp mutations in the two cAMP response elements (CRE1 and CRE2). Luciferase activities induced by FSK and FGF2 were blocked by protein kinase A and tyrosine kinase inhibitors. Gel mobility shift analyses showed that FSK and FGF2 increased the binding of CRE1 and CRE2. CRE1-protein complexes were supershifted by phospho-CREB1 and c-Fos antibodies, and disrupted by CREB1, c-Jun, JunD, Fra2, p300, Runx2, Dlx5 and Smad1 antibodies. CRE2-protein complexes were disrupted by CREB1, phospho-CREB1, c-Fos, c-Jun, JunD, Fra2, p300, Runx2, Dlx5 and Smad1 antibodies. These studies demonstrate that FSK and FGF2 stimulate BSP transcription in DU145 human prostate cancer cells by targeting the CRE1 and CRE2 elements in the human BSP gene promoter.

Fibroblast growth factor 10 plays a causative role in the tracheal cartilage defects in a mouse model of Apert syndrome

Patients with Apert syndrome (AS) display a wide range of congenital malformations including tracheal stenosis, which is a disease characterized by a uniform cartilaginous sleeve in place of a normally ribbed cartilagenous trachea. We have studied the cellular and molecular basis of this phenotype in a mouse model of AS (Fgfr2c(+/Delta) mice), which shows ectopic expression of Fgfr2b in mesenchymal tissues. Here we report that tracheal stenosis is associated with increased proliferation of mesenchymal cells, where the expression of Fgf10 and its upstream regulators Tbx4 and Tbx5 are abnormally elevated. We show that Fgf10 has a critical inductive role in tracheal stenosis, as genetic knockdown of Fgf10 in Fgfr2c(+/Delta) mice rescues this phenotype. These novel findings demonstrate a regulatory role for Fgf10 in tracheal development and shed more light on the underlying cause of tracheal defects in AS.

Induction of fibroblast growth factor 10 (FGF10) in the ileal crypt epithelium after massive small bowel resection suggests a role for FGF10 in gut adaptation

We have previously reported that fibroblast growth factor 10 (FGF10) is crucial for the survival and proliferation of progenitor cells during embryonic gastrointestinal development. We sought to characterize the potential role of FGF10 signaling in the adaptive response following small bowel resection. Adult wild-type and Fgf10(LacZ) mice underwent 50% small bowel resection (SBR) or sham operation. Tissues were harvested 24 or 48 hr after surgery for histology, immunohistochemistry, and in situ hybridization. After SBR, Fgf10 expression was demonstrated in the epithelium at the base of the crypts. Moreover, there was a statistically significant increase in proliferating cells and goblet cells after SBR. In vitro studies using rat intestinal epithelial crypt (IEC-6) cells exposed to medium with or without recombinant FGF10 showed increased proliferation and phosphorylation of Raf and AKT with the addition of FGF10. Our results suggest that FGF10 may play a therapeutic role in diseases involving intestinal failure.

Aberrant receptor internalization and enhanced FRS2-dependent signaling contribute to the transforming activity of the fibroblast growth factor receptor 2 IIIb C3 isoform

Alternative splice variants of fibroblast growth factor receptor 2 (FGFR2) IIIb, designated C1, C2, and C3, possess progressive reduction in their cytoplasmic carboxyl termini (822, 788, and 769 residues, respectively), with preferential expression of the C2 and C3 isoforms in human cancers. We determined that the progressive deletion of carboxyl-terminal sequences correlated with increasing transforming potency. The highly transforming C3 variant lacks five tyrosine residues present in C1, and we determined that the loss of Tyr-770 alone enhanced FGFR2 IIIb C1 transforming activity. Because Tyr-770 may compose a putative YXXL sorting motif, we hypothesized that loss of Tyr-770 in the 770YXXL motif may cause disruption of FGFR2 IIIb C1 internalization and enhance transforming activity. Surprisingly, we found that mutation of Leu-773 but not Tyr-770 impaired receptor internalization and increased receptor stability and activation. Interestingly, concurrent mutations of Tyr-770 and Leu-773 caused 2-fold higher transforming activity than caused by the Y770F or L773A single mutations, suggesting loss of Tyr and Leu residues of the 770YXXL773 motif enhances FGFR2 IIIb transforming activity by distinct mechanisms. We also determined that loss of Tyr-770 caused persistent activation of FRS2 by enhancing FRS2 binding to FGFR2 IIIb. Furthermore, we found that FRS2 binding to FGFR2 IIIb is required for increased FRS2 tyrosine phosphorylation and enhanced transforming activity by Y770F mutation. Our data support a dual mechanism where deletion of the 770YXXL773 motif promotes FGFR2 IIIb C3 transforming activity by causing aberrant receptor recycling and stability and persistent FRS2-dependent signaling.

Runx1 is involved in the fusion of the primary and the secondary palatal shelves

Runx1 is expressed in medial edge epithelial (MEE) cells of the palatal shelf. Conditionally rescued Runx1(-/-) mice showed limited clefting in the anterior junction between the primary and the secondary palatal shelves, but not in the junction between the secondary palates. In wild type mice, the fusing epithelial surface exhibited a rounded cobblestone-like appearance, while such cellular prominence was less evident in the Runx1 mutants. We also found that Fgf18 was expressed in the mesenchyme underlying the MEE and that locally applied FGF18 induced ectopic Runx1 expression in the epithelium of the palatal explants, indicating that Runx1 was induced by mesenchymal Fgf18 signaling. On the other hand, unpaired palatal explant cultures revealed the presence of anterior-posterior (A-P) differences in the MEE fates and fusion mechanism. Interestingly, the location of anterior clefting in Runx1 mutants corresponded to the region with different MEE behavior. These data showed a novel function of Runx1 in morphological changes in the MEE cells in palatal fusion, which is, at least in part, regulated by the mesenchymal Fgf signaling via an epithelial-mesenchymal interaction.

Functional evolutionary history of the mouse Fgf gene family

Fibroblast Growth Factors (FGFs) are polypeptides with diverse activities in development and physiology. The mammalian Fgf family can be divided into the intracellular Fgf11/12/13/14 subfamily (iFGFs), the hormone-like Fgf15/21/23 subfamily (hFGFs), and the canonical Fgf subfamilies, including Fgf1/2/5, Fgf3/4/6, Fgf7/10/22, Fgf8/17/18, and Fgf9/16/20. However, all Fgfs are evolutionarily related. We propose that an Fgf13-like gene is the ancestor of the iFgf subfamily and the most likely evolutionary ancestor of the entire Fgf family. Potential ancestors of the canonical and hFgf subfamilies, Fgf4-, Fgf5-, Fgf8-, Fgf9-, Fgf10-, and Fgf15-like, appear to have derived from an Fgf13-like ancestral gene. Canonical FGFs function in a paracrine manner, while hFGFs function in an endocrine manner. We conclude that the ancestral Fgfs for these subfamilies acquired this functional diversity before the evolution of vertebrates. During the evolution of early vertebrates, the Fgf subfamilies further expanded to contain three or four members in each subfamily.

Tracheal occlusion increases the rate of epithelial branching of embryonic mouse lung via the FGF10-FGFR2b-Sprouty2 pathway

Tracheal occlusion during lung development accelerates growth in response to increased intraluminal pressure. In order to investigate the role of internal pressure on murine early lung development, we cauterized the tip of the trachea, to occlude it, and thus to increase internal pressure. This method allowed us to evaluate the effect of tracheal occlusion on the first few branch generations and on gene expression. We observed that the elevation of internal pressure induced more than a doubling in branching, associated with increased proliferation, while branch elongation speed increased 3-fold. Analysis by RT-PCR showed that Fgf10, Vegf, Sprouty2 and Shh mRNA expressions were affected by the change of intraluminal pressure after 48h of culture, suggesting mechanotransduction via internal pressure of these key developmental genes. Tracheal occlusion did not increase the number of branches of Fgfr2b-/- mice lungs nor of wild type lungs cultured with Fgfr2b antisense RNA. Tracheal occlusion of Fgf10(LacZ/-) hypomorphic lungs led to the formation of fewer branches than in wild type. We conclude that internal pressure regulates the FGF10-FGFR2b-Sprouty2 pathway and thus the speed of the branching process. Therefore pressure levels, fixed both by epithelial secretion and boundary conditions, can control or modulate the branching process via FGF10-FGFR2b-Sprouty2.

AP1 binding site is another target of FGF2 regulation of bone sialoprotein gene transcription

Bone sialoprotein (BSP) is an early marker of osteoblast differentiation. We previously reported that fibroblast growth factor 2 (FGF2) regulates BSP gene transcription via FGF2 response element (FRE) in the proximal promoter of rat BSP gene. We here report that activator protein 1 (AP1) binding site overlapping with glucocorticoid response element (GRE) AP1/GRE in the rat BSP gene promoter is another target of FGF2. Using the osteoblastic cell line ROS17/2.8, we determined that BSP mRNA levels increased by 10 ng/ml FGF2 at 6 and 12 h. Runx2 protein levels increased by FGF2 (10 ng/ml) at 3 h. Treatment of ROS17/2.8 cells with FGF2 (10 ng/ml, 12 h) increased luciferase activities of constructs including -116 to +60 and -938 to +60 of the rat BSP gene promoter. Effects of FGF2 abrogated in constructs included 2 bp mutations in the FRE and AP1/GRE elements. Luciferase activities induced by FGF2 were blocked by tyrosine kinase inhibitor herbimycin A, src-tyrosine kinase inhibitor PP1 and MAP kinase kinase inhibitor U0126. Gel shift analyses showed that FGF2 increased binding of FRE and AP1/GRE elements. Notably, the AP1/GRE-protein complexes were supershifted by Smad1 and c-Fos antibodies, c-Jun and Dlx5 antibodies disrupted the complexes formation, on the other hand AP1/GRE-protein complexes did not change by Runx2 antibody. These studies demonstrate that FGF2 stimulates BSP gene transcription by targeting the FRE and AP1/GRE elements in the rat BSP gene promoter.

The Fgf families in humans, mice, and zebrafish: their evolutional processes and roles in development, metabolism, and disease

Fibroblast growth factors (Fgfs) were originally isolated as growth factors for fibroblasts. However, Fgfs are now recognized as polypeptide growth factors of ca. 150-250 amino acid residues with diverse biological activities and expression profiles. The Fgf signaling system has been identified in multicelluar but not in unicellular organisms. In contrast to the only two Fgf genes and one Fgf receptor (Fgfr) gene in Caenorhabditis elegans, both the human and mouse Fgf and Fgfr gene families comprise twenty-two and four members, respectively. Their evolutional processes indicate that the Fgf and Fgfr gene families greatly co-expanded during the evolution of early vertebrates. The expansion of the Fgf and Fgfr gene families has enabled this signaling system to acquire diversity of function and a nearly ubiquitous involvement in many developmental and physiological processes. The zebrafish fgf gene family comprises twenty-seven members with several paralogs generated by an additional genome duplication. The mouse and zebrafish are useful models for studying gene functions. Fgf knockout mice have been generated. Several Fgf knockout mice die in the embryonic or early postnatal stages, indicating crucial roles for these genes in various developmental processes. However, other Fgf knockout mice survive with subtle phenotypic alterations. Their functions might be redundant. Studies using zebrafish embryos with mutated or knockdown fgfs also indicate that fgfs play crucial roles in development in that species. Although most Fgfs act in development in a paracrine and/or autocrine manner, some have potential roles in metabolism in an endocrine manner. In humans, Fgf signaling disorders result in hereditary diseases and cancers.

Expression and function of fibroblast growth factor 10 and its receptor, fibroblast growth factor receptor 2B, in bovine follicles

Some fibroblast growth factors (FGFs) affect ovarian follicle cell growth and/or differentiation. Whereas many FGFs activate several FGF receptors, FGF7 and FGF10 primarily activate only one, FGFR2B. As FGF7 is produced by bovine theca cells and acts on granulosa cells, we tested the hypothesis that FGF10 may also play a role in folliculogenesis in cattle. Reverse transcription-polymerase chain reaction demonstrated the presence of FGF10 mRNA in the oocytes and theca cells of the antral follicles, as well as in the preantral follicles. FGF10 protein was detected by immunohistochemistry in the oocytes of the preantral and antral follicles, and in the granulosa and theca cells of the antral follicles. FGF10 expression in theca cells changed during follicle development; mRNA abundance decreased with increasing follicular estradiol concentration in healthy follicles, and was lowest in highly atretic follicles. Culturing of granulosa cells in serum-free medium revealed FSH regulation of FGF10 receptor expression. The addition of FGF10 to cultured granulosa cells decreased the level of estradiol but did not alter cell proliferation. These data support a role for FGF10 in signaling to granulosa cells from theca cells and/or the oocyte.