Targeting Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension (BPD-PH): Potential Role of the FGF Signaling Pathway in the Development of the Pulmonary Vascular System

More than 50 years after the first description of Bronchopulmonary dysplasia (BPD) by Northway, this chronic lung disease affecting many preterm infants is still poorly understood. Additonally, approximately 40% of preterm infants suffering from severe BPD also suffer from Bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH), leading to a significant increase in total morbidity and mortality. Until today, there is no curative therapy for both BPD and BPD-PH available. It has become increasingly evident that growth factors are playing a central role in normal and pathologic development of the pulmonary vasculature. Thus, this review aims to summarize the recent evidence in our understanding of BPD-PH from a basic scientific point of view, focusing on the potential role of Fibroblast Growth Factor (FGF)/FGF10 signaling pathway contributing to disease development, progression and resolution.

FGF9 and FGF10 activate distinct signaling pathways to direct lung epithelial specification and branching

Fibroblast growth factors (FGFs) 9 and 10 are essential during the pseudoglandular stage of lung development. Mesothelium-produced FGF9 is principally responsible for mesenchymal growth, whereas epithelium-produced FGF9 and mesenchyme-produced FGF10 guide lung epithelial development, and loss of either of these ligands affects epithelial branching. Because FGF9 and FGF10 activate distinct FGF receptors (FGFRs), we hypothesized that they would control distinct developmental processes. Here, we found that FGF9 signaled through epithelial FGFR3 to directly promote distal epithelial fate specification and inhibit epithelial differentiation. By contrast, FGF10 signaled through epithelial FGFR2b to promote epithelial proliferation and differentiation. Furthermore, FGF9-FGFR3 signaling functionally opposed FGF10-FGFR2b signaling, and FGFR3 preferentially used downstream phosphoinositide 3-kinase (PI3K) pathways, whereas FGFR2b relied on downstream mitogen-activated protein kinase (MAPK) pathways. These data demonstrate that, within lung epithelial cells, different FGFRs function independently; they bind receptor-specific ligands and direct distinct developmental functions through the activation of distinct downstream signaling pathways.

Mesenchymal stem cells maintain the stemness of colon cancer stem cells via interleukin-8/mitogen-activated protein kinase signaling pathway

Mesenchymal stem cells (MSCs) can act as a carrier in tumor therapy, and tumor suppressor gene-modified MSCs can reach and suppress the tumor. However, in the colon cancer microenvironment, MSCs could promote tumor growth and create the environment that is conducive to the survival of cancer stem cells (CSCs). This study discovered MSCs from three sources (bone marrow, adipose, placenta) could induce the stemness and epithelial–mesenchymal transition (EMT) of HCT116 in vitro, meanwhile adipose- and placenta-derived MSCs increase the proportion of CD133+/CD44+ HCT116. Then, we explored the interaction mechanism between CD133+/CD44+ HCT116 and MSCs by the bioinformatics and in vitro assays. After CD133+/CD44+ HCT116 were co-cultured with MSCs, many cytokines in MSCs were stimulated, including interleukin-8 (IL-8). The binding of IL-8/CXCR2 activates the downstream mitogen-activated protein kinase (MAPK) signaling pathway in colon CSCs, thereby promoting the stemness and EMT. However, inhibition of IL-8/CXCR2/Erk1/2 could reverse the effect of MSCs on CSC stemness. In addition, MSCs co-cultured with CD133+/CD44+ HCT116 produce a carcinoma-associated fibroblast phenotype via intracellular FGF10–PKA–Akt–β-catenin signaling, which can be attenuated by IL-8 peptide inhibitor. To conclude, IL-8 promotes the interaction between colon CSCs and MSCs, and activates the MAPK signaling pathway in colon CSCs, which provides a theoretical basis for the application of MSCs in clinical practice.

IMPACT STATEMENT

MSCs have the property of chemotaxis and they can migrate to the tumor site by paracrine pathway in the tumor environment, and then interact with tumor cells. Although a mass of studies have been conducted about the impact of MSCs on tumors, it is still controversial whether the exogenous MSCs promote or inhibit tumor growth. In this work, we evaluated the effects of MSCs from three sources (bone marrow, adipose, placenta) on the proliferation, stemness, and metastasis of the colon cancer cells both in vitro and in vivo. Then, we proved the IL-8/CXCR2/MAPK and FGF10–PKA–Akt–β-catenin signaling pathway which mediate the interplay between MSC and CD133+/CD44+ colon cancer cell. This research aims to provide a theoretical basis for the safe application of MSCs in the clinical treatment of colon cancer.

Attenuated Fgf Signaling Underlies the Forelimb Heterochrony in the Emu Dromaius novaehollandiae

Powered flight was fundamental to the establishment and radiation of birds. However, flight has been lost multiple times throughout avian evolution. Convergent losses of flight within the ratites (flightless paleognaths, including the emu and ostrich) often coincide with reduced wings. Although there is a wealth of anatomical knowledge for several ratites, the genetic mechanisms causing these changes remain debated. Here, we use a multidisciplinary approach employing embryological, genetic, and genomic techniques to interrogate the mechanisms underlying forelimb heterochrony in emu embryos. We show that the initiation of limb formation, an epithelial to mesenchymal transition (EMT) in the lateral plate mesoderm (LPM) and myoblast migration into the LPM, occur at equivalent stages in the emu and chick. However, the emu forelimb fails to subsequently proliferate. The unique emu forelimb expression of Nkx2.5, previously associated with diminished wing development, initiates after this stage (concomitant with myoblast migration into the LPM) and is therefore unlikely to cause this developmental delay. In contrast, RNA sequencing of limb tissue reveals significantly lower Fgf10 expression in the emu forelimb. Artificially increasing Fgf10 expression in the emu LPM induces ectodermal Fgf8 expression and a limb bud. Analyzing open chromatin reveals differentially active regulatory elements near Fgf10 and Sall-1 in the emu wing, and the Sall-1 enhancer activity is dependent on a likely Fgf-mediated Ets transcription factor-binding site. Taken together, our results suggest that regulatory changes result in lower expression of Fgf10 and a concomitant failure to express genes required for limb proliferation in the early emu wing bud.

Tanycyte-Like Cells Derived From Mouse Embryonic Stem Culture Show Hypothalamic Neural Stem/Progenitor Cell Functions

Tanycytes have recently been accepted as neural stem/progenitor cells in the postnatal hypothalamus. Persistent retina and anterior neural fold homeobox (Rax) expression is characteristic of tanycytes in contrast to its transient expression of whole hypothalamic precursors. In this study, we found that Rax+ residual cells in the maturation phase of hypothalamic differentiation in mouse embryonic stem cell (mESC) cultures had similar characteristics to ventral tanycytes. They expressed typical neural stem/progenitor cell markers, including Sox2, vimentin, and nestin, and differentiated into mature neurons and glial cells. Quantitative RT-PCR analysis showed that Rax+ residual cells expressed Fgf-10, Fgf-18, and Lhx2, which are expressed by ventral tanycytes. They highly expressed tanycyte-specific genes Dio2 and Gpr50 compared with Rax+ early hypothalamic progenitor cells. Therefore, Rax+ residual cells in the maturation phase of hypothalamic differentiation were considered to be more differentiated and similar to late progenitor cells and tanycytes. They self-renewed and formed neurospheres when cultured with exogenous FGF-2. Additionally, these Rax+ neurospheres differentiated into three neuronal lineages (neurons, astrocytes, and oligodendrocytes), including neuropeptide Y+ neuron, that are reported to be differentiated from ventral tanycytes toward the arcuate nuclei. Thus, Rax+ residual cells were multipotent neural stem/progenitor cells. Rax+ neurospheres were stably passaged and retained high Sox2 expression even after multiple passages. These results suggest the successful induction of Rax+ tanycyte-like cells from mESCs [induced tanycyte-like (iTan) cells]. These hypothalamic neural stem/progenitor cells may have potential in regenerative medicine and as a research tool.

Development of the basal hypothalamus through anisotropic growth

The adult hypothalamus is subdivided into distinct domains: pre-optic, anterior, tuberal and mammillary. Each domain harbours an array of neurones that act together to regulate homeostasis. The embryonic origins and the development of hypothalamic neurones, however, remain enigmatic. Here, we summarise recent studies in model organisms that challenge current views of hypothalamic development, which traditionally have attempted to map adult domains to correspondingly located embryonic domains. Instead, new studies indicate that hypothalamic neurones arise from progenitor cells that undergo anisotropic growth, expanding to a greater extent than other progenitors, and grow in different dimensions. We describe in particular how a multipotent Shh/ Fgf10-expressing progenitor population gives rise to progenitors throughout the basal hypothalamus that grow anisotropically and sequentially: first, a subset displaced rostrally give rise to anterior-ventral/tuberal neuronal progenitors; then a subset displaced caudally give rise to mammillary neuronal progenitors; and, finally, a subset(s) displaced ventrally give rise to tuberal infundibular glial progenitors. As this occurs, stable populations of Shh+ive and Fgf10+ive progenitors form. We describe current understanding of the mechanisms that induce Shh+ive /Fgf10+ive progenitors and begin to direct their differentiation to anterior-ventral/tuberal neuronal progenitors, mammillary neuronal progenitors and tuberal infundibular progenitors. Taken together, these studies suggest a new model for hypothalamic development that we term the "anisotropic growth model". We discuss the implications of the model for understanding the origins of adult hypothalamic neurones.

Wnt/Fgf crosstalk is required for the specification of basal cells in the mouse trachea

Basal progenitor cells are crucial for the establishment and maintenance of the tracheal epithelium. However, it remains unclear how these progenitor cells are specified during foregut development. Here, we found that ablation of the Wnt chaperone protein Gpr177 (also known as Wntless) in mouse tracheal epithelium causes a significant reduction in the number of basal progenitor cells accompanied by cartilage loss in Shh-Cre;Gpr177^loxp/loxp mutants. Consistent with the association between cartilage and basal cell development, Nkx2.1⁺p63⁺ basal cells are co-present with cartilage nodules in Shh-Cre;Ctnnb1^DM/loxp mutants, which maintain partial cell-cell adhesion but not the transcription regulation function of β-catenin. More importantly, deletion of Ctnnb1 in the mesenchyme leads to the loss of basal cells and cartilage, concomitant with reduced transcript levels of Fgf10 in Dermo1-Cre;Ctnnb1^loxp/loxp mutants. Furthermore, deletion of Fgf receptor 2 (Fgfr2) in the epithelium also leads to significantly reduced numbers of basal cells, supporting the importance of Wnt/Fgf crosstalk in early tracheal development.

Complex Compound Inheritance of Lethal Lung Developmental Disorders Due to Disruption of the TBX-FGF Pathway

Primary defects in lung branching morphogenesis, resulting in neonatal lethal pulmonary hypoplasias, are incompletely understood. To elucidate the pathogenetics of human lung development, we studied a unique collection of samples obtained from deceased individuals with clinically and histopathologically diagnosed interstitial neonatal lung disorders: acinar dysplasia (n = 14), congenital alveolar dysplasia (n = 2), and other lethal lung hypoplasias (n = 10). We identified rare heterozygous copy-number variant deletions or single-nucleotide variants (SNVs) involving TBX4 (n = 8 and n = 2, respectively) or FGF10 (n = 2 and n = 2, respectively) in 16/26 (61%) individuals. In addition to TBX4, the overlapping ∼2 Mb recurrent and nonrecurrent deletions at 17q23.1q23.2 identified in seven individuals with lung hypoplasia also remove a lung-specific enhancer region. Individuals with coding variants involving either TBX4 or FGF10 also harbored at least one non-coding SNV in the predicted lung-specific enhancer region, which was absent in 13 control individuals with the overlapping deletions but without any structural lung anomalies. The occurrence of rare coding variants involving TBX4 or FGF10 with the putative hypomorphic non-coding SNVs implies a complex compound inheritance of these pulmonary hypoplasias. Moreover, they support the importance of TBX4-FGF10-FGFR2 epithelial-mesenchymal signaling in human lung organogenesis and help to explain the histopathological continuum observed in these rare lethal developmental disorders of the lung.

Engineering innervated secretory epithelial organoids by magnetic three-dimensional bioprinting for stimulating epithelial growth in salivary glands

Current saliva-based stimulation therapies for radiotherapy-induced xerostomia are not fully effective due to the presence of damaged secretory epithelia and nerves in the salivary gland (SG). Hence, three-dimensional bio-engineered organoids are essential to regenerate the damaged SG. Herein, a recently validated three-dimensional (3D) biofabrication system, the magnetic 3D bioprinting (M3DB), is tested to generate innervated secretory epithelial organoids from a neural crest-derived mesenchymal stem cell, the human dental pulp stem cell (hDPSC). Cells are tagged with magnetic nanoparticles (MNP) and spatially arranged with magnet dots to generate 3D spheroids. Next, a SG epithelial differentiation stage was completed with fibroblast growth factor 10 (4-400 ng/ml) to recapitulate SG epithelial morphogenesis and neurogenesis. The SG organoids were then transplanted into ex vivo model to evaluate their epithelial growth and innervation. M3DB-formed spheroids exhibited both high cell viability rate (>90%) and stable ATP intracellular activity compared to MNP-free spheroids. After differentiation, spheroids expressed SG epithelial compartments including secretory epithelial, ductal, myoepithelial, and neuronal. Fabricated organoids also produced salivary α-amylase upon FGF10 stimulation, and intracellular calcium mobilization and trans-epithelial resistance was elicited upon neurostimulation with different neurotransmitters. After transplantation, the SG-like organoids significantly stimulated epithelial and neuronal growth in damaged SG. It is the first time bio-functional innervated SG-like organoids are bioprinted. Thus, this is an important step towards SG regeneration and the treatment of radiotherapy-induced xerostomia.

Canonical WNT Signaling Regulates the Pituitary Organizer and Pituitary Gland Formation

The pituitary organizer is a domain within the ventral diencephalon that expresses Bmp4, Fgf8, and Fgf10, which induce the formation of the pituitary precursor, Rathke's pouch, from the oral ectoderm. The WNT signaling pathway regulates this pituitary organizer such that loss of Wnt5a leads to an expansion of the pituitary organizer and an enlargement of Rathke's pouch. WNT signaling is classified into canonical signaling, which is mediated by β-CATENIN, and noncanonical signaling, which operates independently of β-CATENIN. WNT5A is typically classified as a noncanonical WNT; however, other WNT family members are expressed in the ventral diencephalon and nuclear localized β-CATENIN is observed in the ventral diencephalon. Therefore, we sought to determine whether canonical WNT signaling is necessary for regulation of pituitary organizer function. Using a conditional loss-of-function approach, we deleted β-catenin within the mouse ventral diencephalon. Mutant embryos have a smaller Rathke's pouch, resulting from a reduced pituitary organizer, especially Fgf8. This result suggests that canonical WNT signaling promotes pituitary organizer function, instead of inhibiting it. To test this hypothesis, we stimulated canonical WNT signaling in the ventral diencephalon using an inducible gain-of-function allele of β-catenin and found that stimulating canonical WNT signaling expands the domain of Fgf8 and results in a dysmorphic Rathke's pouch. These results demonstrate that canonical WNT signaling in the ventral diencephalon is necessary for proper expression of pituitary organizer genes and suggests that a balance of both canonical and noncanonical WNT signaling is necessary to ensure proper formation of Rathke's pouch.

Two-Way Conversion between Lipogenic and Myogenic Fibroblastic Phenotypes Marks the Progression and Resolution of Lung Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a form of progressive interstitial lung disease with unknown etiology. Due to a lack of effective treatment, IPF is associated with a high mortality rate. The hallmark feature of this disease is the accumulation of activated myofibroblasts that excessively deposit extracellular matrix proteins, thus compromising lung architecture and function and hindering gas exchange. Here we investigated the origin of activated myofibroblasts and the molecular mechanisms governing fibrosis formation and resolution. Genetic engineering in mice enables the time-controlled labeling and monitoring of lipogenic or myogenic populations of lung fibroblasts during fibrosis formation and resolution. Our data demonstrate a lipogenic-to-myogenic switch in fibroblastic phenotype during fibrosis formation. Conversely, we observed a myogenic-to-lipogenic switch during fibrosis resolution. Analysis of human lung tissues and primary human lung fibroblasts indicates that this fate switching is involved in IPF pathogenesis, opening potential therapeutic avenues to treat patients.

HIF-1α in Myeloid Cells Promotes Adipose Tissue Remodeling Toward Insulin Resistance

Adipose tissue hypoxia is an important feature of pathological adipose tissue expansion. Hypoxia-inducible factor-1α (HIF-1α) in adipocytes reportedly induces oxidative stress and fibrosis, rather than neoangiogenesis via vascular endothelial growth factor (VEGF)-A. We previously reported that macrophages in crown-like structures (CLSs) are both hypoxic and inflammatory. In the current study, we examined how macrophage HIF-1α is involved in high-fat diet (HFD)-induced inflammation, neovascularization, hypoxia, and insulin resistance using mice with myeloid cell-specific HIF-1α deletion that were fed an HFD. Myeloid cell-specific HIF-1α gene deletion protected against HFD-induced inflammation, CLS formation, poor vasculature development in the adipose tissue, and systemic insulin resistance. Despite a reduced expression of Vegfa in epididymal white adipose tissue (eWAT), the preadipocytes and endothelial cells of HIF-1α-deficient mice expressed higher levels of angiogenic factors, including Vegfa, Angpt1, Fgf1, and Fgf10 in accordance with preferable eWAT remodeling. Our in vitro study revealed that lipopolysaccharide-treated bone marrow-derived macrophages directly inhibited the expression of angiogenic factors in 3T3-L1 preadipocytes. Thus, macrophage HIF-1α is involved not only in the formation of CLSs, further enhancing the inflammatory responses, but also in the inhibition of neoangiogenesis in preadipocytes. We concluded that these two pathways contribute to the obesity-related physiology of pathological adipose tissue expansion, thus causing systemic insulin resistance.

Evidence that the 5p12 Variant rs10941679 Confers Susceptibility to Estrogen-Receptor-Positive Breast Cancer through FGF10 and MRPS30 Regulation

Genome-wide association studies (GWASs) have revealed increased breast cancer risk associated with multiple genetic variants at 5p12. Here, we report the fine mapping of this locus using data from 104,660 subjects from 50 case-control studies in the Breast Cancer Association Consortium (BCAC). With data for 3,365 genotyped and imputed SNPs across a 1 Mb region (positions 44,394,495-45,364,167; NCBI build 37), we found evidence for at least three independent signals: the strongest signal, consisting of a single SNP rs10941679, was associated with risk of estrogen-receptor-positive (ER+) breast cancer (per-g allele OR ER+ = 1.15; 95% CI 1.13-1.18; p = 8.35 × 10-30). After adjustment for rs10941679, we detected signal 2, consisting of 38 SNPs more strongly associated with ER-negative (ER-) breast cancer (lead SNP rs6864776: per-a allele OR ER- = 1.10; 95% CI 1.05-1.14; p conditional = 1.44 × 10-12), and a single signal 3 SNP (rs200229088: per-t allele OR ER+ = 1.12; 95% CI 1.09-1.15; p conditional = 1.12 × 10-05). Expression quantitative trait locus analysis in normal breast tissues and breast tumors showed that the g (risk) allele of rs10941679 was associated with increased expression of FGF10 and MRPS30. Functional assays demonstrated that SNP rs10941679 maps to an enhancer element that physically interacts with the FGF10 and MRPS30 promoter regions in breast cancer cell lines. FGF10 is an oncogene that binds to FGFR2 and is overexpressed in ∼10% of human breast cancers, whereas MRPS30 plays a key role in apoptosis. These data suggest that the strongest signal of association at 5p12 is mediated through coordinated activation of FGF10 and MRPS30, two candidate genes for breast cancer pathogenesis.

Regulators of genetic risk of breast cancer identified by integrative network analysis

Genetic risk for breast cancer is conferred by a combination of multiple variants of small effect. To better understand how risk loci might combine, we examined whether risk-associated genes share regulatory mechanisms. We created a breast cancer gene regulatory network comprising transcription factors and groups of putative target genes (regulons) and asked whether specific regulons are enriched for genes associated with risk loci via expression quantitative trait loci (eQTLs). We identified 36 overlapping regulons that were enriched for risk loci and formed a distinct cluster within the network, suggesting shared biology. The risk transcription factors driving these regulons are frequently mutated in cancer and lie in two opposing subgroups, which relate to estrogen receptor (ER)(+) luminal A or luminal B and ER(-) basal-like cancers and to different luminal epithelial cell populations in the adult mammary gland. Our network approach provides a foundation for determining the regulatory circuits governing breast cancer, to identify targets for intervention, and is transferable to other disease settings.

Regulatory Mechanisms Driving Salivary Gland Organogenesis

Salivary glands develop as highly branched structures designed to produce and secrete saliva. Advances in mouse genetics, stem cell biology, and regenerative medicine are having a tremendous impact on our understanding of salivary gland organogenesis. Understanding how submandibular gland (SMG) initiation, branching morphogenesis, and cell differentiation occur, as well as defining the progenitor/stem cells and cell and tissue interactions that drive SMG development will help guide regenerative approaches for patients suffering from loss of salivary gland function. This review focuses on recent literature from the past 5 years investigating the regulatory mechanisms driving SMG organogenesis.

Wnt4 is essential to normal mammalian lung development

Wnt signaling is essential to many events during organogenesis, including the development of the mammalian lung. The Wnt family member Wnt4 has been shown to be required for the development of kidney, gonads, thymus, mammary and pituitary glands. Here, we show that Wnt4 is critical for proper morphogenesis and growth of the respiratory system. Using in situ hybridization in mouse embryos, we identify a previously uncharacterized site of Wnt4 expression in the anterior trunk mesoderm. This expression domain initiates as early as E8.25 in the mesoderm abutting the tracheoesophageal endoderm, between the fusing dorsal aortae and the heart. Analysis of Wnt4(-/-) embryos reveals severe lung hypoplasia and tracheal abnormalities; however, aortic fusion and esophageal development are unaffected. We find decreased cell proliferation in Wnt4(-/-) lung buds, particularly in tip domains. In addition, we observe reduction of the important lung growth factors Fgf9, Fgf10, Sox9 and Wnt2 in the lung bud during early stages of organogenesis, as well as decreased tracheal expression of the progenitor factor Sox9. Together, these data reveal a previously unknown role for the secreted protein Wnt4 in respiratory system development.

Zebrafish fgf10b has a complementary function to fgf10a in liver and pancreas development

Fgf10 is a critical growth factor in mammals for development of endodermal organs such as the liver, pancreas, lung, and gut. Due to whole genome duplication, the zebrafish has two fgf10 orthologs, fgf10a and fgf10b. While fgf10a has a role in development of the esophagus and swimbladder, we found in the present study that fgf10b had a complementary expression pattern in the liver, pancreas, and gut. Morpholino knockdown of Fgf10b further confirmed its essential role in the normal development of liver and pancreas. Thus, our data provide another example of functional partition of two duplicated othologous genes during evolution.

Estrogen mediated epithelial proliferation in the uterus is directed by stromal Fgf10 and Bmp8a

To define endometrial stromal-derived paracrine mediators that participate in estradiol-17β (E2)-induced epithelial proliferation, microarray analysis of gene expression was carried out in mouse uterine epithelial-stromal co-culture systems under the condition of E2 or vehicle (control). Our results demonstrated gene alteration by E2: in epithelial cells, we found up-regulation of 119 genes and down-regulation of 28 genes, while in stroma cells we found up-regulation of 144 genes and down-regulation of 184 genes. A functional enrichment analysis of the upregulated epithelial genes implicated them for proliferation, while upregulated stromal genes were associated with extracellular functions. Quantitative RT-PCR and in situ hybridization results confirmed differential gene expression in both cell cultures and ovariectomized uteri after the above treatments. Based on our identification of stromal secretory factors, we found evidence that suppression by siRNA specifically for Bmp8a and/or Fgf10 in the stromal layer caused significant inhibition of proliferation by E2 in the co-culture system, suggesting Bmp8a and Fgf10 act as paracrine mediators during E2-dependent control of uterine proliferation. The localization of receptors and receptor activation signaling in epithelial cells in both the co-culture system and uteri was consistent with their involvement in ligand-receptor signaling. Interestingly, loss of Bmp8a or Fgf10 also caused abrogation of E2-regulated epithelial receptor signaling in co-culture systems, suggesting that stroma-derived Fgf10 and Bmp8a are responsible for epithelial communication. Overall, stromal Fgf10 and Bmp8a serve as potential paracrine factors for E2-dependent regulation of epithelial proliferation in the uterus.

Salivary Gland Dysplasia in Fgf10 Heterozygous Mice: A New Mouse Model of Xerostomia

Xerostomia, or chronic dry mouth, is a common syndrome caused by a lack of saliva that can lead to severe eating difficulties, dental caries and oral candida infections. The prevalence of xerostomia increases with age and affects approximately 30% of people aged 65 or older. Given the large numbers of sufferers, and the potential increase in incidence given our aging population, it is important to understand the complex mechanisms that drive hyposalivation and the consequences for the dentition and oral mucosa. From this study we propose the Fgf10 +/- mouse as a model to investigate xerostomia. By following embryonic salivary gland development, in vivo and in vitro, we show that a reduction in Fgf10 causes a delay in branching of salivary glands. This leads to hypoplasia of the glands, a phenotype that is not rescued postnatally or by adulthood in both male and female Fgf10 +/- mice. Histological analysis of the glands showed no obvious defect in cellular differentiation or acini/ductal arrangements, however there was a significant reduction in their size and weight. Analysis of saliva secretion showed that hypoplasia of the glands led to a significant reduction in saliva production in Fgf10 +/- adults, giving rise to a reduced saliva pellicle in the oral cavity of these mice. Mature mice were shown to drink more and in many cases had severe tooth wear. The Fgf10 +/- mouse is therefore a useful model to explore the causes and effects of xerostomia.

Feedback, receptor clustering, and receptor restriction to single cells yield large Turing spaces for ligand-receptor-based Turing models

Turing mechanisms can yield a large variety of patterns from noisy, homogenous initial conditions and have been proposed as patterning mechanism for many developmental processes. However, the molecular components that give rise to Turing patterns have remained elusive, and the small size of the parameter space that permits Turing patterns to emerge makes it difficult to explain how Turing patterns could evolve. We have recently shown that Turing patterns can be obtained with a single ligand if the ligand-receptor interaction is taken into account. Here we show that the general properties of ligand-receptor systems result in very large Turing spaces. Thus, the restriction of receptors to single cells, negative feedbacks, regulatory interactions among different ligand-receptor systems, and the clustering of receptors on the cell surface all greatly enlarge the Turing space. We further show that the feedbacks that occur in the FGF10-SHH network that controls lung branching morphogenesis are sufficient to result in large Turing spaces. We conclude that the cellular restriction of receptors provides a mechanism to sufficiently increase the size of the Turing space to make the evolution of Turing patterns likely. Additional feedbacks may then have further enlarged the Turing space. Given their robustness and flexibility, we propose that receptor-ligand-based Turing mechanisms present a general mechanism for patterning in biology.

Effect of FGF10 monoclonal antibody on psoriasis-like model in guinea pigs

OBJECTIVE

To investigate the therapeutical effect of topical application of FGF10 monoclonal antibody on the guinea pig model with psoriasis.

METHODS

Blank group, model group, hydrocortisone butyrate treatment group and high-dose (0.188 mg/ml), middle-dose (0.094 mg/ml) and low-dose (0.063 mg/ml) FGF10 antibody group were set, respectively. After two-week treatment, pathological changes of psoriasis-like models were observed by HE staining, and the difference in VEGF and PCNA expression levels among different groups was observed by immunohistochemical staining.

RESULTS

All the test indicators of each treatment group were lower than those of the model group, and there was a significant difference (P<0.05). The inflammatory cell count of the high-dose FGF10 antibody group was not statistically different from those of the blank group (t=0.77, P=0.443), and the counts of the rest treatment groups were significantly higher than those of the blank group and the high-dose FGF10 antibody group (P<0.05). The epidermal thickness of each FGF10 antibody treatment group was significantly higher than that of hydrocortisone butyrate treatment group (P<0.05), while no statistical difference was found in the epidermal thickness among the FGF10 antibody treatment groups (P>0.05). FGF10 monoclonal antibodies can reduce the PCNA and VEGF expression in psoriasis-like model of guinea pig's ear.

CONCLUSION

FGF10 monoclonal antibodies can affect keratinocyte proliferation and division and can also significantly inhibit the inflammatory response in the psoriasis model. Meanwhile, FGF10 monoclonal antibodies can produce a therapeutic effect on psoriatic lesions by inhibiting the abnormal epidermis cell proliferation and neovascularization of the dermis in the psoriasis model.

Fgf3 and Fgf10a work in concert to promote maturation of the epibranchial placodes in zebrafish

Essential cellular components of the paired sensory organs of the vertebrate head are derived from transient thickenings of embryonic ectoderm known as cranial placodes. The epibranchial (EB) placodes give rise to sensory neurons of the EB ganglia that are responsible for relaying visceral sensations form the periphery to the central nervous system. Development of EB placodes and subsequent formation of EB ganglia is a multistep process regulated by various extrinsic factors, including fibroblast growth factors (Fgfs). We discovered that two Fgf ligands, Fgf3 and Fgf10a, cooperate to promote EB placode development. Whereas EB placodes are induced in the absence of Fgf3 and Fgf10a, they fail to express placode specific markers Pax2a and Sox3. Expression analysis and mosaic rescue experiments demonstrate that Fgf3 signal is derived from the endoderm, whereas Fgf10a is emitted from the lateral line system and the otic placode. Further analyses revealed that Fgf3 and Fgf10a activities are not required for cell proliferation or survival, but are required for placodal cells to undergo neurogenesis. Based on these data, we conclude that a combined loss of these Fgf factors results in a failure of the EB placode precursors to initiate a transcriptional program needed for maturation and subsequent neurogenesis. These findings highlight the importance and complexity of reiterated Fgf signaling during cranial placode formation and subsequent sensory organ development.

Cell-autonomous and non-cell-autonomous roles for IRF6 during development of the tongue

Interferon regulatory factor 6 (IRF6) encodes a highly conserved helix-turn-helix DNA binding protein and is a member of the interferon regulatory family of DNA transcription factors. Mutations in IRF6 lead to isolated and syndromic forms of cleft lip and palate, most notably Van der Woude syndrome (VWS) and Popliteal Ptyerigium Syndrome (PPS). Mice lacking both copies of Irf6 have severe limb, skin, palatal and esophageal abnormalities, due to significantly altered and delayed epithelial development. However, a recent report showed that MCS9.7, an enhancer near Irf6, is active in the tongue, suggesting that Irf6 may also be expressed in the tongue. Indeed, we detected Irf6 staining in the mesoderm-derived muscle during development of the tongue. Dual labeling experiments demonstrated that Irf6 was expressed only in the Myf5+ cell lineage, which originates from the segmental paraxial mesoderm and gives rise to the muscles of the tongue. Fate mapping of the segmental paraxial mesoderm cells revealed a cell-autonomous Irf6 function with reduced and poorly organized Myf5+ cell lineage in the tongue. Molecular analyses showed that the Irf6−/− embryos had aberrant cytoskeletal formation of the segmental paraxial mesoderm in the tongue. Fate mapping of the cranial neural crest cells revealed non-cell-autonomous Irf6 function with the loss of the inter-molar eminence. Loss of Irf6 function altered Bmp2, Bmp4, Shh, and Fgf10 signaling suggesting that these genes are involved in Irf6 signaling. Based on these data, Irf6 plays important cell-autonomous and non-cell-autonomous roles in muscular differentiation and cytoskeletal formation in the tongue.

Imparting regenerative capacity to limbs by progenitor cell transplantation

The frog Xenopus can normally regenerate its limbs at early developmental stages but loses the ability during metamorphosis. This behavior provides a potential gain-of-function model for measures that can enhance limb regeneration. Here, we show that frog limbs can be caused to form multidigit regenerates after receiving transplants of larval limb progenitor cells. It is necessary to activate Wnt/β-catenin signaling in the cells and to add Sonic hedgehog, FGF10, and thymosin β4. These factors promote survival and growth of the grafted cells and also provide pattern information. The eventual regenerates are not composed solely of donor tissue; the host cells also make a substantial contribution despite their lack of regeneration competence. Cells from adult frog legs or from regenerating tadpole tails do not promote limb regeneration, demonstrating the necessity for limb progenitor cells. These findings have obvious implications for the development of a technology to promote limb regeneration in mammals.

Fibroblast growth factor 10-fibroblast growth factor receptor 2b mediated signaling is not required for adult glandular stomach homeostasis

The signaling pathways that are essential for gastric organogenesis have been studied in some detail; however, those that regulate the maintenance of the gastric epithelium during adult homeostasis remain unclear. In this study, we investigated the role of Fibroblast growth factor 10 (FGF10) and its main receptor, Fibroblast growth factor receptor 2b (FGFR2b), in adult glandular stomach homeostasis. We first showed that mouse adult glandular stomach expressed Fgf10, its receptors, Fgfr1b and Fgfr2b, and most of the other FGFR2b ligands (Fgf1, Fgf7, Fgf22) except for Fgf3 and Fgf20. Fgf10 expression was mesenchymal whereas FGFR1 and FGFR2 expression were mostly epithelial. Studying double transgenic mice that allow inducible overexpression of Fgf10 in adult mice, we showed that Fgf10 overexpression in normal adult glandular stomach increased epithelial proliferation, drove mucous neck cell differentiation, and reduced parietal and chief cell differentiation. Although a similar phenotype can be associated with the development of metaplasia, we found that Fgf10 overexpression for a short duration does not cause metaplasia. Finally, investigating double transgenic mice that allow the expression of a soluble form of Fgfr2b, FGF10's main receptor, which acts as a dominant negative, we found no significant changes in gastric epithelial proliferation or differentiation in the mutants. Our work provides evidence, for the first time, that the FGF10-FGFR2b signaling pathway is not required for epithelial proliferation and differentiation during adult glandular stomach homeostasis.