Betacellulin overexpression in transgenic mice causes disproportionate growth, pulmonary hemorrhage syndrome, and complex eye pathology

Fentanyl Overdose Causes Prolonged Cardiopulmonary Dysregulation in Male SKH1 Mice

Fentanyl overdose is a survivable condition that commonly resolves without chronic overt changes in phenotype. While the acute physiological effects of fentanyl overdose, such as opioid-induced respiratory depression (OIRD) and Wooden Chest Syndrome, represent immediate risks of lethality, little is known about longer-term systemic or organ-level impacts for survivors. In this study, we investigated the effects of a single, bolus fentanyl overdose on components of the cardiopulmonary system up to one week post. SKH1 mice were administered subcutaneous fentanyl at the highest non-lethal dose (62 mg/kg), LD10 (110 mg/kg), or LD50 (135 mg/kg), before euthanasia at 40 min, 6 h, 24 h, or 7 d post-exposure. The cerebral cortex, heart, lungs, and plasma were assayed using an immune monitoring 48-plex panel. The results showed significantly dysregulated cytokine, chemokine, and growth factor concentrations compared to time-matched controls, principally in hearts, then lungs and plasma to a lesser extent, for the length of the study, with the cortex largely unaffected. Major significant analytes contributing to variance included eotaxin-1, IL-33, and betacellulin, which were generally downregulated across time. The results of this study suggest that cardiopulmonary toxicity may persist from a single fentanyl overdose and have wide implications for the endurance of the expanding population of survivors.

TXNIP overexpression in mice enhances streptozotocin-induced diabetes severity

Thioredoxin-interacting protein (TXNIP) is a key player in the endocrine pancreas; it induces beta cell apoptosis, such that TXNIP deficiency promotes beta cell survival. To study its function in more detail, we generated transgenic mice with ubiquitous overexpression of TXNIP. CBA^TXNIP/+ mice were investigated under basal conditions and after being challenged in diet-induced obesity (DIO) and streptozotocin-induced type 1 diabetes mellitus (T1DM) models. TXNIP overexpression caused no effect in the DIO model, contrasting to the already reported TXNIP-deficient mice. However, in the T1DM background, CBA^TXNIP/+ animals showed significantly enhanced blood glucose and increased glucose levels in a glucose tolerance test. Finally, the beta cell mass of CBA^TXNIP/+ transgenic animals in the T1DM model was significantly reduced compared to control littermates. Our study demonstrates that overexpression of TXNIP doesn't affect blood glucose parameters under basal conditions. However, overexpression of TXNIP in a T1DM model enhances the severity of the disease.

Epidermal growth factor signalling pathway in endochondral ossification: an evidence-based narrative review

During endochondral bone development, a complex process that leads to the formation of the majority of skeletal elements, mesenchymal cells condense, differentiating into chondrocytes and producing the foetal growth plate. Chondrocytes progressively hypertrophy, induce angiogenesis and are then gradually replaced by bone. Epidermal Growth Factor (EGF), one of many growth factors, is the prototype of the EGF-ligand family, which comprises several proteins involved in cell proliferation, migration and survival. In bone, EGF pathway signalling finely tunes the first steps of chondrogenesis by maintaining mesenchymal cells in an undifferentiated stage, and by promoting hypertrophic cartilage replacement. Moreover, EGF signalling modulates bone homeostasis by stimulating osteoblast and osteoclast proliferation, and by regulating osteoblast differentiation under specific spatial and temporal conditions. This evidence-based narrative review describes the EGF pathway in bone metabolism and endochondral bone development. This comprehensive description may be useful in light of possible clinical applications in orthopaedic practice. A deeper knowledge of the role of EGF in bone may be useful in musculoskeletal conditions which may benefit from the modulation of this signalling pathway.Key messagesThe EGF pathway is involved in bone metabolism.EGF signalling is essential in the very early stages of limb development by maintaining cells in an undifferentiated stage.EGF pathway positively regulates chondrocyte proliferation, negatively modulates hypertrophy, and favours cartilage replacement by bone.EGF and EGF-like proteins finely tune the proliferation and differentiation of bone tissue cells, and they also regulate the initial phases of endochondral ossification.

BCG vaccination-induced emergency granulopoiesis provides rapid protection from neonatal sepsis

Death from sepsis in the neonatal period remains a serious threat for millions. Within 3 days of administration, bacille Calmette-Guérin (BCG) vaccination can reduce mortality from neonatal sepsis in human newborns, but the underlying mechanism for this rapid protection is unknown. We found that BCG was also protective in a mouse model of neonatal polymicrobial sepsis, where it induced granulocyte colony-stimulating factor (G-CSF) within hours of administration. This was necessary and sufficient to drive emergency granulopoiesis (EG), resulting in a marked increase in neutrophils. This increase in neutrophils was directly and quantitatively responsible for protection from sepsis. Rapid induction of EG after BCG administration also occurred in three independent cohorts of human neonates.

Unraveling ERBB network dynamics upon betacellulin signaling in pancreatic ductal adenocarcinoma in mice

Pancreatic ductal adenocarcinoma (PDAC) will soon belong to the top three cancer killers. The only approved specific PDAC therapy targets the epidermal growth factor receptor (EGFR). Although EGFR is a crucial player in PDAC development, EGFR-based therapy is disappointing. In this study, we evaluated the role of the EGFR ligand betacellulin (BTC) in PDAC. The expression of BTC was investigated in human pancreatic cancer specimen. Then, we generated a BTC knockout mouse model by CRISPR/Cas9 technology and a BTC overexpression model. Both models were crossed with the Ptf1aCre/+ ;KRASG12D/+ (KC) mouse model (B-/- KC or BKC, respectively). In addition, EGFR, ERBB2, and ERBB4 were investigated by the pancreas-specific deletion of each receptor using the Cre-loxP system. Tumor initiation and progression were analyzed in all mouse lines, and the underlying molecular biology of PDAC was investigated at different time points. BTC is expressed in human and murine PDAC. B-/- KC mice showed a decelerated PDAC progression, associated with decreased EGFR activation. BKC mice developed severe PDAC with a poor survival rate. The dramatically increased BTC-mediated tumor burden was EGFR-dependent, but also ERBB4 and ERBB2 were involved in PDAC development or progression, as depletion of EGFR, ERBB2, or ERBB4 significantly improved the survival rate of BTC-mediated PDAC. BTC increases PDAC tumor burden dramatically by enhanced RAS activation. EGFR signaling, ERBB2 signaling, and ERBB4 signaling are involved in accelerated PDAC development mediated by BTC indicating that targeting the whole ERBB family, instead of a single receptor, is a promising strategy for the development of future PDAC therapies.

The protective effect of betacellulin against acute pancreatitis is ERBB4 dependent

BACKGROUND

The EGFR ligand betacellulin (BTC) has been previously shown to protect mice against experimentally induced acute pancreatitis (AP). BTC binds both autonomous ERBB receptors EGFR and ERBB4. In this study, we evaluated the mechanism underlying the protection from AP-associated inflammation in detail.

METHODS

AP was induced with cerulein or L-arginine and investigated in a pancreas-specific ERBB4 knockout and in an EGFR knockdown mouse model (Egfr^Wa5/+). Pancreatitis was evaluated by scoring inflammation, necrosis, and edema, while microarrays were performed to analyze alterations in the transcriptome between mice with AP and animals which were protected against AP. The intracellular domain (ICD) of ERBB4 was analyzed in different cell compartments.

RESULTS

While the pancreas of BTC transgenic mice in the background of Egfr^Wa5/+ is still protected against AP, the BTC-mediated protection is no longer present in the absence of ERBB4. We further demonstrate that BTC activates the ICD of ERBB4, and increases the expression of the extracellular matrix (ECM) proteins periostin and matrix gla protein as well as the ECM modulators matrix metalloproteinases 2 and 3, but only in the presence of ERBB4. Notably, the increased expression of these proteins is not accompanied by an increased ECM amount.

CONCLUSIONS

These findings suggest that BTC derivates, as a drug, or the ERBB4 receptor, as a druggable target protein, could play an important role in modulating the course of AP and even prevent AP in humans.

Secondary crest myofibroblast PDGFRα controls the elastogenesis pathway via a secondary tier of signaling networks during alveologenesis

Postnatal alveolar formation is the most important and the least understood phase of lung development. Alveolar pathologies are prominent in neonatal and adult lung diseases. The mechanisms of alveologenesis remain largely unknown. We inactivated Pdgfra postnatally in secondary crest myofibroblasts (SCMF), a subpopulation of lung mesenchymal cells. Lack of Pdgfra arrested alveologenesis akin to bronchopulmonary dysplasia (BPD), a neonatal chronic lung disease. The transcriptome of mutant SCMF revealed 1808 altered genes encoding transcription factors, signaling and extracellular matrix molecules. Elastin mRNA was reduced, and its distribution was abnormal. Absence of Pdgfra disrupted expression of elastogenic genes, including members of the Lox, Fbn and Fbln families. Expression of EGF family members increased when Tgfb1 was repressed in mouse. Similar, but not identical, results were found in human BPD lung samples. In vitro, blocking PDGF signaling decreased elastogenic gene expression associated with increased Egf and decreased Tgfb family mRNAs. The effect was reversible by inhibiting EGF or activating TGFβ signaling. These observations demonstrate the previously unappreciated postnatal role of PDGFA/PDGFRα in controlling elastogenic gene expression via a secondary tier of signaling networks composed of EGF and TGFβ.

Role of Epidermal Growth Factor Receptor (EGFR) and Its Ligands in Kidney Inflammation and Damage

Chronic kidney disease (CKD) is characterized by persistent inflammation and progressive fibrosis, ultimately leading to end-stage renal disease. Although many studies have investigated the factors involved in the progressive deterioration of renal function, current therapeutic strategies only delay disease progression, leaving an unmet need for effective therapeutic interventions that target the cause behind the inflammatory process and could slow down or reverse the development and progression of CKD. Epidermal growth factor receptor (EGFR) (ERBB1), a membrane tyrosine kinase receptor expressed in the kidney, is activated after renal damage, and preclinical studies have evidenced its potential as a therapeutic target in CKD therapy. To date, seven official EGFR ligands have been described, including epidermal growth factor (EGF) (canonical ligand), transforming growth factor-α, heparin-binding epidermal growth factor, amphiregulin, betacellulin, epiregulin, and epigen. Recently, the connective tissue growth factor (CTGF/CCN2) has been described as a novel EGFR ligand. The direct activation of EGFR by its ligands can exert different cellular responses, depending on the specific ligand, tissue, and pathological condition. Among all EGFR ligands, CTGF/CCN2 is of special relevance in CKD. This growth factor, by binding to EGFR and downstream signaling pathway activation, regulates renal inflammation, cell growth, and fibrosis. EGFR can also be “transactivated” by extracellular stimuli, including several key factors involved in renal disease, such as angiotensin II, transforming growth factor beta (TGFB), and other cytokines, including members of the tumor necrosis factor superfamily, showing another important mechanism involved in renal pathology. The aim of this review is to summarize the contribution of EGFR pathway activation in experimental kidney damage, with special attention to the regulation of the inflammatory response and the role of some EGFR ligands in this process. Better insights in EGFR signaling in renal disease could improve our current knowledge of renal pathology contributing to therapeutic strategies for CKD development and progression.

Betacellulin (BTC) Biases the EGFR To Dimerize with ErbB3

There are 13 known endogenous ligands for the epidermal growth factor receptor (EGFR) and its closely related ErbB receptor family members. We previously reported that betacellulin (BTC) is more efficacious than epidermal growth factor (EGF) in mediating corneal wound healing, although the molecular basis for this difference was unknown. For the most part, differences between ligands can be attributed to variability in binding properties, such as the unique rate of association and dissociation, pH sensitivity, and selective binding to individual ErbB family members of each ligand. However, this was not the case for BTC. Despite being better at promoting wound healing via enhanced cell migration, BTC has reduced receptor affinity and weaker induction of EGFR phosphorylation. These data indicate that the response of BTC is not due to enhanced affinity or kinase activity. Receptor phosphorylation and proximity ligation assays indicate that BTC treatment significantly increases ErbB3 phosphorylation and EGFR-ErbB3 heterodimers when compared with EGF treatment. We observed that EGFR-ErbB3 heterodimers contribute to cell migration, because the addition of an ErbB3 antagonist (MM-121) or RNA interference-mediated knockdown of ErbB3 attenuates BTC-stimulated cell migration compared with EGF. Thus, we demonstrate that, despite both ligands binding to the EGFR, BTC biases the EGFR to dimerize with ErbB3 to regulate the biologic response.

An EGFR ligand promotes EGFR-mutant but not KRAS-mutant lung cancer in vivo

EGFR ligands (e.g., EGF and TGFA) have been shown to be clinically associated with poor survival in lung cancer. Since TGFA itself initiates autochthonous tumors in liver, breast, and pancreas but not in the lung in transgenic mice in vivo, it would appear that an EGFR ligand may not initiate but rather promote lung cancer. However, it has not been proven in vivo whether lung cancer is promoted by an EGFR ligand. Using transgenic mouse models conditionally expressing EGFR^L858R or Kras^G12D with TGFA (an EGFR ligand) in lung epithelium, we determined that TGFA promoted the growth of EGFR^L858R-lung tumors in airway regions but not that of Kras^G12D-lung tumors. Analysis of TCGA datasets identified ΔNp63 and AGR2 as potential key tumor-promoting regulators, which were highly induced in the TGFA-induced EGFR^L858R-lung tumors. The expression of AGR2 was positively correlated with the expression of TGFA in human EGFR-mutant lung adenocarcinomas. The expression of TGFA in human EGFR-mutant lung adenocarcinomas but not in the EGFR wild-type lung adenocarcinoma was associated with poor survival. These results suggest that targeting EGFR ligands may benefit patients who carry EGFR-mutant lung tumors but will not benefit patients with KRAS-mutant lung tumors.

Overactive Epidermal Growth Factor Receptor Signaling Leads to Increased Fibrosis after Severe Acute Respiratory Syndrome Coronavirus Infection

Severe acute respiratory syndrome coronavirus (SARS-CoV) is a highly pathogenic respiratory virus that causes morbidity and mortality in humans. After infection with SARS-CoV, the acute lung injury caused by the virus must be repaired to regain lung function. A dysregulation in this wound healing process leads to fibrosis. Many survivors of SARS-CoV infection develop pulmonary fibrosis (PF), with higher prevalence in older patients. Using mouse models of SARS-CoV pathogenesis, we have identified that the wound repair pathway, controlled by the epidermal growth factor receptor (EGFR), is critical to recovery from SARS-CoV-induced tissue damage. In mice with constitutively active EGFR [EGFR(DSK5) mice], we find that SARS-CoV infection causes enhanced lung disease. Importantly, we show that during infection, the EGFR ligands amphiregulin and heparin-binding EGF-like growth factor (HB-EGF) are upregulated, and exogenous addition of these ligands during infection leads to enhanced lung disease and altered wound healing dynamics. Our data demonstrate a key role of EGFR in the host response to SARS-CoV and how it may be implicated in lung disease induced by other highly pathogenic respiratory viruses.IMPORTANCE PF has many causative triggers, including severe respiratory viruses such as SARS-CoV. Currently there are no treatments to prevent the onset or limit the progression of PF, and the molecular pathways underlying the development of PF are not well understood. In this study, we identified a role for the balanced control of EGFR signaling as a key factor in progression to PF. These data demonstrate that therapeutic treatment modulating EGFR activation could protect against PF development caused by severe respiratory virus infection.

The role of epidermal growth factor receptor (EGFR) signaling in SARS coronavirus-induced pulmonary fibrosis

Many survivors of the 2003 outbreak of severe acute respiratory syndrome (SARS) developed residual pulmonary fibrosis with increased severity seen in older patients. Autopsies of patients that died from SARS also showed fibrosis to varying extents. Pulmonary fibrosis can be occasionally seen as a consequence to several respiratory viral infections but is much more common after a SARS coronavirus (SARS-CoV) infection. Given the threat of future outbreaks of severe coronavirus disease, including Middle East respiratory syndrome (MERS), it is important to understand the mechanisms responsible for pulmonary fibrosis, so as to support the development of therapeutic countermeasures and mitigate sequelae of infection. In this article, we summarize pulmonary fibrotic changes observed after a SARS-CoV infection, discuss the extent to which other respiratory viruses induce fibrosis, describe available animal models to study the development of SARS-CoV induced fibrosis and review evidence that pulmonary fibrosis is caused by a hyperactive host response to lung injury mediated by epidermal growth factor receptor (EGFR) signaling. We summarize work from our group and others indicating that inhibiting EGFR signaling may prevent an excessive fibrotic response to SARS-CoV and other respiratory viral infections and propose directions for future research.

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Patients who survived SARS coronavirus infection often developed pulmonary fibrosis.

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Mouse models of SARS-CoV infection recapitulate fibrotic lesions seen in humans.

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Epidermal growth factor receptor (EGFR) may modulate the wound healing response to SARS-CoV.

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The EGFR pathway is a prime target for therapeutic interventions to reduce fibrosis after respiratory virus infection.

Comparative aspects of rodent and nonrodent animal models for mechanistic and translational diabetes research

The prevalence of diabetes mellitus, which currently affects 387 million people worldwide, is permanently rising in both adults and adolescents. Despite numerous treatment options, diabetes mellitus is a progressive disease with severe comorbidities, such as nephropathy, neuropathy, and retinopathy, as well as cardiovascular disease. Therefore, animal models predictive of the efficacy and safety of novel compounds in humans are of great value to address the unmet need for improved therapeutics. Although rodent models provide important mechanistic insights, their predictive value for therapeutic outcomes in humans is limited. In recent years, the pig has gained importance for biomedical research because of its close similarity to human anatomy, physiology, size, and, in contrast to non-human primates, better ethical acceptance. In this review, anatomic, biochemical, physiological, and morphologic aspects relevant to diabetes research will be compared between different animal species, that is, mouse, rat, rabbit, pig, and non-human primates. The value of the pig as a model organism for diabetes research will be highlighted, and (dis)advantages of the currently available approaches for the generation of pig models exhibiting characteristics of metabolic syndrome or type 2 diabetes mellitus will be discussed.

EGFR Signaling in Liver Diseases

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase that is activated by several ligands leading to the activation of diverse signaling pathways controlling mainly proliferation, differentiation, and survival. The EGFR signaling axis has been shown to play a key role during liver regeneration following acute and chronic liver damage, as well as in cirrhosis and hepatocellular carcinoma (HCC) highlighting the importance of the EGFR in the development of liver diseases. Despite the frequent overexpression of EGFR in human HCC, clinical studies with EGFR inhibitors have so far shown only modest results. Interestingly, a recent study has shown that in human HCC and in mouse HCC models the EGFR is upregulated in liver macrophages where it plays a tumor-promoting function. Thus, the role of EGFR in liver diseases appears to be more complex than what anticipated. Further studies are needed to improve the molecular understanding of the cell-specific signaling pathways that control disease development and progression to be able to develop better therapies targeting major components of the EGFR signaling network in selected cell types. In this review, we compiled the current knowledge of EGFR signaling in different models of liver damage and diseases, mainly derived from the analysis of HCC cell lines and genetically engineered mouse models (GEMMs).

Osteoblast-specific overexpression of amphiregulin leads to transient increase in femoral cancellous bone mass in mice

The epidermal growth factor receptor ligand amphiregulin (AREG) has been implicated in bone physiology and in bone anabolism mediated by intermittent parathyroid hormone treatment. However, the functions of AREG in bone have been only incipiently evaluated in vivo. Here, we generated transgenic mice overexpressing AREG specifically in osteoblasts (Col1-Areg). pQCT analysis of the femoral metaphysis revealed increased trabecular bone mass at 4, 8, and 10weeks of age in Col1-Areg mice compared to control littermates. However, the high bone mass phenotype was transient and disappeared in older animals. Micro-CT analysis of the secondary spongiosa confirmed increased trabecular bone volume and trabecular number in the distal femur of 4-week-old AREG-tg mice compared to control littermates. Furthermore, μ-CT analysis of the primary spongiosa revealed unaltered production of new bone trabeculae in distal femora of Col1-Areg mice. Histomorphometric analysis revealed a reduced number of osteoclasts in 4-week-old Col1-Areg mice, but not at later time points. Cancellous bone formation rate remained unchanged in Col1-Areg mice at all time points. In addition, bone mass and bone turnover in lumbar vertebral bodies were similar in Col1-Areg and control mice at all ages examined. Proliferation and differentiation of osteoblasts isolated from neonatal calvariae did not differ between Col1-Areg and control mice. Taken together, these data suggest that AREG overexpression in osteoblasts induces a transient high bone mass phenotype in the trabecular compartment of the appendicular skeleton by a growth-related, non-cell autonomous mechanism, leading to a positive bone balance with unchanged bone formation and lowered bone resorption.

Alterations in gene expression and DNA methylation during murine and human lung alveolar septation

DNA methylation, a major epigenetic mechanism, may regulate coordinated expression of multiple genes at specific time points during alveolar septation in lung development. The objective of this study was to identify genes regulated by methylation during normal septation in mice and during disordered septation in bronchopulmonary dysplasia. In mice, newborn lungs (preseptation) and adult lungs (postseptation) were evaluated by microarray analysis of gene expression and immunoprecipitation of methylated DNA followed by sequencing (MeDIP-Seq). In humans, microarray gene expression data were integrated with genome-wide DNA methylation data from bronchopulmonary dysplasia versus preterm and term lung. Genes with reciprocal changes in expression and methylation, suggesting regulation by DNA methylation, were identified. In mice, 95 genes with inverse correlation between expression and methylation during normal septation were identified. In addition to genes known to be important in lung development (Wnt signaling, Angpt2, Sox9, etc.) and its extracellular matrix (Tnc, Eln, etc.), genes involved with immune and antioxidant defense (Stat4, Sod3, Prdx6, etc.) were also observed. In humans, 23 genes were differentially methylated with reciprocal changes in expression in bronchopulmonary dysplasia compared with preterm or term lung. Genes of interest included those involved with detoxifying enzymes (Gstm3) and transforming growth factor-β signaling (bone morphogenetic protein 7 [Bmp7]). In terms of overlap, 20 genes and three pathways methylated during mouse lung development also demonstrated changes in methylation between preterm and term human lung. Changes in methylation correspond to altered expression of a number of genes associated with lung development, suggesting that DNA methylation of these genes may regulate normal and abnormal alveolar septation.

Betacellulin ameliorates hyperglycemia in obese diabetic db/db mice

We found that administration of a recombinant adenovirus (rAd) expressing betacellulin (BTC) into obese diabetic db/db mice ameliorated hyperglycemia. Exogenous glucose clearance was significantly improved, and serum insulin levels were significantly higher in rAd-BTC-treated mice than rAd-β-gal-treated control mice. rAd-BTC treatment increased insulin/bromodeoxyuridine double-positive cells in the islets, and islets from rAd-BTC-treated mice exhibited a significant increase in the level of G1-S phase-related cyclins as compared with control mice. In addition, BTC treatment increased messenger RNA (mRNA) and protein levels of these cyclins and cyclin-dependent kinases in MIN-6 cells. BTC treatment induced intracellular Ca(2+) levels through phospholipase C-γ1 activation, and upregulated calcineurin B (CnB1) levels as well as calcineurin activity. Upregulation of CnB1 by BTC treatment was observed in isolated islet cells from db/db mice. When treated with CnB1 small interfering RNA (siRNA) in MIN-6 cells and isolated islets, induction of cell cycle regulators by BTC treatment was blocked and consequently reduced BTC-induced cell viability. As well as BTC's effects on cell survival and insulin secretion, our findings demonstrate a novel pathway by which BTC controls beta-cell regeneration in the obese diabetic condition by regulating G1-S phase cell cycle expression through Ca(2+) signaling pathways.

KEY MESSAGES

Administration of BTC to db/db mice results in amelioration of hyperglycemia. BTC stimulates beta-cell proliferation in db/db mice. Ca(2+) signaling was involved in BTC-induced beta-cell proliferation. BTC has an anti-apoptotic effect and potentiates glucose-stimulated insulin secretion.

Betacellulin transgenic mice develop urothelial hyperplasia and show sex-dependent reduction in urinary major urinary protein content

The epidermal growth factor (EGF)-like ligands and their cognate ERBB1-4 receptors represent important signaling pathways that regulate tissue and cell proliferation, differentiation and regeneration in a wide variety of tissues, including the urogenital tract. Betacellulin (BTC) can activate all four ERBB tyrosine kinase receptors and is a multifunctional EGF-like ligand with diverse roles in β cell differentiation, bone maturation, formation of functional epithelial linings and vascular permeability in different organs. Using transgenic BTC mice, we have studied the effect of constitutive systemic BTC over-expression on the urinary bladder. BTC was detected in microvascular structures of the stromal bladder compartment and in umbrella cells representing the protective apical lining of the uroepithelium. ERBB1 and ERBB4 receptors were co-localized in the urothelium. Mice transgenic for BTC and double transgenic for both BTC and the dominant kinase-dead mutant of EGFR (Waved 5) developed hyperplasia of the uroepithelium at 5months of age, suggesting that urothelial hyperplasia was not exclusively dependent on ERBB1/EGFR. Mass spectrometric analysis of urine revealed a significant down-regulation of major urinary proteins in female BTC transgenic mice, suggesting a novel role for systemic BTC in odor-based signaling in female transgenic BTC mice.

Knowledge Gaps in Rodent Pancreas Biology: Taking Human Pluripotent Stem Cell-Derived Pancreatic Beta Cells into Our Own Hands

In the field of stem cell biology and diabetes, we and others seek to derive mature and functional human pancreatic β cells for disease modeling and cell replacement therapy. Traditionally, knowledge gathered from rodents is extended to human pancreas developmental biology research involving human pluripotent stem cells (hPSCs). While much has been learnt from rodent pancreas biology in the early steps toward Pdx1(+) pancreatic progenitors, much less is known about the transition toward Ngn3(+) pancreatic endocrine progenitors. Essentially, the later steps of pancreatic β cell development and maturation remain elusive to date. As a result, the most recent advances in the stem cell and diabetes field have relied upon combinatorial testing of numerous growth factors and chemical compounds in an arbitrary trial-and-error fashion to derive mature and functional human pancreatic β cells from hPSCs. Although this hit-or-miss approach appears to have made some headway in maturing human pancreatic β cells in vitro, its underlying biology is vaguely understood. Therefore, in this mini-review, we discuss some of these late-stage signaling pathways that are involved in human pancreatic β cell differentiation and highlight our current understanding of their relevance in rodent pancreas biology. Our efforts here unravel several novel signaling pathways that can be further studied to shed light on unexplored aspects of rodent pancreas biology. New investigations into these signaling pathways are expected to advance our knowledge in human pancreas developmental biology and to aid in the translation of stem cell biology in the context of diabetes treatments.

Regulatory mechanisms of betacellulin in CXCL8 production from lung cancer cells

Background

Betacellulin (BTC), a member of the epidermal growth factor (EGF) family, binds and activates ErbB1 and ErbB4 homodimers. BTC was expressed in tumors and involved in tumor growth progression. CXCL8 (interleukin-8) was involved in tumor cell proliferation via the transactivation of the epidermal growth factor receptor (EGFR).

Materials and methods

The present study was designed to investigate the possible interrelation between BTC and CXCL8 in human lung cancer cells (A549) and demonstrated the mechanisms of intracellular signals in the regulation of both functions. Bio-behaviors of A549 were assessed using Cell-IQ Alive Image Monitoring System.

Results

We found that BTC significantly increased the production of CXCL8 through the activation of the EGFR-PI3K/Akt-Erk signal pathway. BTC induced the resistance of human lung cancer cells to TNF-α/CHX-induced apoptosis. Treatments with PI3K inhibitors, Erk1/2 inhibitor, or Erlotinib significantly inhibited BTC-induced CXCL8 production and cell proliferation and movement.

Conclusion

Our data indicated that CXCL8 production from lung cancer cells could be initiated by an autocrine mechanism or external sources of BTC through the EGFR–PI3K–Akt–Erk pathway to the formation of inflammatory microenvironment. BTC may act as a potential target to monitor and improve the development of lung cancer inflammation.

The ABC of BTC: structural properties and biological roles of betacellulin

Betacellulin was initially detected as a growth-promoting factor in the conditioned medium of a mouse pancreatic β-cell tumor cell line. Sequencing of the purified protein and of the cloned cDNA supported the assumption that betacellulin is a new ligand of the epidermal growth factor receptor (EGFR), which was later confirmed experimentally. As a typical EGFR ligand, betacellulin is expressed by a variety of cell types and tissues, and the soluble growth factor is proteolytically cleaved from a larger membrane-anchored precursor. Importantly, BTC can - in addition to the EGFR - bind and activate all possible heterodimeric combinations of the related ERBB receptors including the highly oncogenic ERBB2/3 dimer, as well as homodimers of ERBB4. While a large number of studies attest a role for betacellulin in the differentiation of pancreatic β-cells, the last decade witnessed the association of betacellulin with a large number of additional biological processes, ranging from reproduction to the control of neural stem cells.

Transforming growth factor alpha controls the transition from hypertrophic cartilage to bone during endochondral bone growth

We have recently identified transforming growth factor alpha (TGFα) as a novel growth factor involved in the joint disease osteoarthritis. The role of TGFα in normal cartilage and bone physiology however, has not been well defined.

PURPOSE

The objective of this study was to determine the role of TGFα in bone development through investigation of the Tgfa knockout mouse.

METHODS

The gross skeletons as well as the cartilage growth plates of Tgfa knockout mice and their control littermates were examined during several developmental stages ranging from newborn to ten weeks old.

RESULTS

Knockout mice experienced skeletal growth retardation and expansion of the hypertrophic zone of the growth plate. These phenotypes were transient and spontaneously resolved by ten weeks of age. Tgfa knockout growth plates also had fewer osteoclasts along the cartilage/bone interface. Furthermore, knockout mice expressed less RUNX2, RANKL, and MMP13 mRNA in their cartilage growth plates than controls did.

CONCLUSIONS

Tgfa knockout mice experience a delay in bone development, specifically the conversion of hypertrophic cartilage to true bone. The persistence of the hypertrophic zone of the growth plate appears to be mediated by a decrease in MMP13 and RANKL expression in hypertrophic chondrocytes and a resulting reduction in osteoclast recruitment. Overall, TGFα appears to be an important growth factor regulating the conversion of cartilage to bone during the process of endochondral ossification.

Human TNF-related apoptosis-inducing ligand-expressing dendritic cells from transgenic pigs attenuate human xenogeneic T cell responses

BACKGROUND

Efficient and precise techniques for the genetic modification of pigs facilitate the generation of tailored donor animals for xenotransplantation. Numerous transgenic pig lines exist with the focus on inhibition of the complement system and of humoral immune responses. In addition, immune cell-based responses need to be controlled to prevent pig-to-primate xenograft rejection. Expression of human (hu) TNF-related apoptosis-inducing ligand (TRAIL) on porcine cells has the potential to ameliorate human T cell responses.

METHODS

We generated transgenic pigs expressing human tumor necrosis factor (TNF)-related apoptosis-inducing ligand (huTRAIL) under the control of either the mouse H2K(b) promoter or a CMV enhancer/chicken β-actin (CAG) promoter, the latter one (CAG-huTRAIL) on a GGTA1 knockout/huCD46 transgenic background. The biological activity of huTRAIL was demonstrated by its apoptosis-inducing effect on Jurkat lymphoma cells. To clarify whether huTRAIL affects also primary immune cells and whether its effects depend on the presence of co-stimulatory molecules, we exposed human peripheral blood mononuclear cells (PBMC) or isolated T cells to huTRAIL-expressing porcine fibroblasts or dendritic cells in vitro.

RESULTS

H2Kb-huTRAIL transgenic pigs express huTRAIL mainly in the spleen and secondary lymphoid tissues. The CAG-huTRAIL construct facilitated huTRAIL expression in multiple organs, the level being at least one order of magnitude higher than in H2Kb-huTRAIL transgenic pigs. Incubation with huTRAIL-expressing H2Kb-huTRAIL transgenic porcine dendritic cells decreased human T cell proliferation significantly without any signs of apoptosis. In spite of the high transgene expression level, CAG-huTRAIL transgenic fibroblasts did not affect proliferation of human PBMC, independent of their activation state.

CONCLUSIONS

These results suggest huTRAIL expression on porcine dendritic cells as a possible strategy to attenuate T cell responses against pig-to-primate xenografts.

Genetically determined heterogeneity of lung disease in a mouse model of airway mucus obstruction

Mucus clearance is an important airway innate defense mechanism. Airway-targeted overexpression of the epithelial Na(+) channel β-subunit [encoded by sodium channel nonvoltage gated 1, beta subunit (Scnn1b)] in mice [Scnn1b-transgenic (Tg) mice] increases transepithelial Na(+) absorption and dehydrates the airway surface, which produces key features of human obstructive lung diseases, including mucus obstruction, inflammation, and air-space enlargement. Because the first Scnn1b-Tg mice were generated on a mixed background, the impact of genetic background on disease phenotype in Scnn1b-Tg mice is unknown. To explore this issue, congenic Scnn1b-Tg mice strains were generated on C57BL/6N, C3H/HeN, BALB/cJ, and FVB/NJ backgrounds. All strains exhibited a two- to threefold increase in tracheal epithelial Na(+) absorption, and all developed airway mucus obstruction, inflammation, and air-space enlargement. However, there were striking differences in neonatal survival, ranging from 5 to 80% (FVB/NJ<BALB/cJ<C3H/HeN<C57BL/6N), which correlated with the incidence of upper airway mucus plugging and the levels of Muc5b in bronchoalveolar lavage. The strains also exhibited variable Clara cell necrotic degeneration in neonatal intrapulmonary airways and a variable incidence of pulmonary hemorrhage and lung atelectasis. The spontaneous occurrence of a high surviving BALB/cJ line, which exhibited delayed onset of Na(+) hyperabsorption, provided evidence that: 1) air-space enlargement and postnatal death were only present when Na(+) hyperabsorption occurred early, and 2) inflammation and mucus obstruction developed whenever Na(+) hyperabsorption was expressed. In summary, the genetic context and timing of airway innate immune dysfunction critically determines lung disease phenotype. These mouse strains may be useful to identify key modifier genes and pathways.

In vivo evidence for epidermal growth factor receptor (EGFR)-mediated release of prolactin from the pituitary gland

Members of the epidermal growth factor receptor (EGFR/ERBB) system are essential local regulators of mammary gland development and function. Emerging evidence suggests that EGFR signaling may also influence mammary gland activity indirectly by promoting the release of prolactin from the pituitary gland in a MAPK and estrogen receptor-α (ERα)-dependent manner. Here, we report that overexpression of the EGFR ligand betacellulin (BTC) causes a lactating-like phenotype in the mammary gland of virgin female mice including the major hallmarks of lactogenesis. BTC transgenic (BTC-tg) females showed reduced levels of prolactin in the pituitary gland and increased levels of the hormone in the circulation. Furthermore, treatment of BTC-tg females with bromocriptine, an inhibitor of prolactin secretion, blocked the development of the lactation-like phenotype, suggesting that it is caused by central release of prolactin rather than by local actions of BTC in the mammary gland. Introduction of the antimorphic Egfr allele Wa5 also blocked the appearance of the mammary gland alterations, revealing that the phenotype is EGFR-dependent. We detected an increase in MAPK activity, but unchanged phosphorylation of ERα in the pituitary gland of BTC-tg females as compared with control mice. These results provide the first functional evidence in vivo for a role of the EGFR system in regulating mammary gland activity by modulating prolactin release from the pituitary gland.

Betacellulin overexpression in mesenchymal stem cells induces insulin secretion in vitro and ameliorates streptozotocin-induced hyperglycemia in rats

Betacellulin (BTC), a ligand of the epidermal growth factor receptor, has been shown to promote growth and differentiation of pancreatic β-cells and to improve glucose metabolism in experimental diabetic rodent models. Mesenchymal stem cells (MSCs) have been already proved to be multipotent. Recent work has attributed to rat and human MSCs the potential to differentiate into insulin-secreting cells. Our goal was to transfect rat MSCs with a plasmid containing BTC cDNA to guide MSC differentiation into insulin-producing cells. Prior to induction of cell MSC transfection, MSCs were characterized by flow cytometry and the ability to in vitro differentiate into mesoderm cell types was evaluated. After rat MSC characterization, these cells were electroporated with a plasmid containing BTC cDNA. Transfected cells were cultivated in Dulbecco's modified Eagle medium high glucose (H-DMEM) with 10 mM nicotinamide. Then, the capability of MSC-BTC to produce insulin in vitro and in vivo was evaluated. It was possible to demonstrate by radioimmunoassay analysis that 10(4) MSC-BTC cells produced up to 0.4 ng/mL of insulin, whereas MSCs transfected with the empty vector (negative control) produced no detectable insulin levels. Moreover, MSC-BTC were positive for insulin in immunohistochemistry assay. In parallel, the expression of pancreatic marker genes was demonstrated by molecular analysis of MSC-BTC. Further, when MSC-BTC were transplanted to streptozotocin diabetic rats, BTC-transfected cells ameliorated hyperglycemia from over 500 to about 200 mg/dL at 35 days post-cell transplantation. In this way, our results clearly demonstrate that BTC overabundance enhances glucose-induced insulin secretion in MSCs in vitro as well as in vivo.

Betacellulin protects from pancreatitis by activating stress-activated protein kinase

BACKGROUND & AIMS

Acute pancreatitis (AP) is a serious, unpredictable clinical problem, the pathophysiology of which is poorly understood. Here, we evaluate whether betacellulin (BTC), a ligand of the epidermal growth factor receptor also able to activate the proapoptotic ERBB4 receptor, can protect against experimental AP.

METHODS

AP was induced in transgenic mice overexpressing BTC (BTC-tg), control mice, or control mice after administration of recombinant BTC. The severity of pancreatitis was assessed by measurements of serum amylase and lipase and histologic grading. The involvement of the stress-activated protein kinase (SAPK) was evaluated by treating BTC-tg mice with an SAPK inhibitor before induction of AP.

RESULTS

BTC-tg mice showed increased apoptosis and proliferation in the exocrine pancreas, indicating an increased cell turnover. There was a marked, epidermal growth factor receptor-independent decrease in pancreas weight. After induction of AP by cerulein injection, BTC-tg mice showed a significantly lower increase in serum amylase and lipase levels as well as less pronounced tissue necrosis, edema, and inflammation, as compared to nontransgenic littermates. This protective effect, also confirmed in the L-arginine AP model, was associated with increased phosphorylation of SAPK and abrogated after treatment of BTC-tg mice with a SAPK inhibitor. Finally, the protective effect of BTC against AP was confirmed by treating nontransgenic mice with recombinant BTC.

CONCLUSIONS

These findings indicate a potential application of the BTC/ERBB4 pathway for modulating the course of AP.

Betacellulin inhibits osteogenic differentiation and stimulates proliferation through HIF-1alpha

Cellular signaling via epidermal growth factor (EGF) and EGF-like ligands can determine cell fate and behavior. Osteoblasts, which are responsible for forming and mineralizing osteoid, express EGF receptors and alter rates of proliferation and differentiation in response to EGF receptor activation. Transgenic mice over-expressing the EGF-like ligand betacellulin (BTC) exhibit increased cortical bone deposition; however, because the transgene is ubiquitously expressed in these mice, the identity of cells affected by BTC and responsible for increased cortical bone thickness remains unknown. We have therefore examined the influence of BTC upon mesenchymal stem cell (MSC) and pre-osteoblast differentiation and proliferation. BTC decreases the expression of osteogenic markers in both MSCs and pre-osteoblasts; interestingly, increases in proliferation require hypoxia-inducible factor-alpha (HIF-alpha), as an HIF antagonist prevents BTC-driven proliferation. Both MSCs and pre-osteoblasts express EGF receptors ErbB1, ErbB2, and ErbB3, with no change in expression under osteogenic differentiation. These are the first data that demonstrate an influence of BTC upon MSCs and the first to implicate HIF-alpha in BTC-mediated proliferation.

Betacellulin inhibits osteogenic differentiation and stimulates proliferation through HIF-1alpha

Cellular signaling via epidermal growth factor (EGF) and EGF-like ligands can determine cell fate and behavior. Osteoblasts, which are responsible for forming and mineralizing osteoid, express EGF receptors and alter rates of proliferation and differentiation in response to EGF receptor activation. Transgenic mice over-expressing the EGF-like ligand betacellulin (BTC) exhibit increased cortical bone deposition; however, because the transgene is ubiquitously expressed in these mice, the identity of cells affected by BTC and responsible for increased cortical bone thickness remains unknown. We have therefore examined the influence of BTC upon mesenchymal stem cell (MSC) and pre-osteoblast differentiation and proliferation. BTC decreases the expression of osteogenic markers in both MSCs and pre-osteoblasts; interestingly, increases in proliferation require hypoxia-inducible factor-alpha (HIF-α), as an HIF antagonist prevents BTC-driven proliferation. Both MSCs and pre-osteoblasts express EGF receptors ErbB1, ErbB2, and ErbB3, with no change in expression under osteogenic differentiation. These are the first data that demonstrate an influence of BTC upon MSCs and the first to implicate HIF-α in BTC-mediated proliferation.

Specific transgene expression in mouse pancreatic beta-cells under the control of the porcine insulin promoter

The availability of regulatory sequences directing tissue-specific expression of transgenes in genetically modified mice and large animals is a prerequisite for the development of adequate models for human diseases. The rat insulin 2 gene (Ins2) promoter, widely used to achieve transgene expression in pancreatic beta-cells of mice, also directs expression to extrapancreatic tissues and performs poorly in isolated pancreatic islets of human, mouse, and pig. To evaluate whether the full 5' untranslated region (UTR) of the porcine insulin gene (INS) confers robust and specific expression in beta-cells we generated an expression cassette containing 1500bp of the porcine INS 5' UTR and the 3' UTR of the bovine growth hormone gene (GH). The cassette was designed to allow easy exchange of the sequences to be expressed and easy removal of the vector backbone from the expression cassette. To evaluate the properties of the cassette, we initially inserted a cDNA encoding human betacellulin, a growth factor known to affect structural and functional parameters of beta-cells. After confirming the functionality and specificity of the construct in vitro, transgenic mouse lines were generated by pronuclear DNA microinjection. Using RT-PCR, immunohistochemistry and immunofluorescence, we show that transgenic mice expressed human betacellulin exclusively in beta-cells. Confirming the proposed insulinotropic effect of betacellulin, transgenic mice showed improved glucose tolerance. We conclude that the newly designed expression cassette containing 1500bp of the porcine insulin promoter 5' UTR confers robust and specific transgene expression to beta-cells in vitro and in transgenic mice.

The EGFR network in bone biology and pathology

The resorption, formation and maintenance of bone are coordinated by the action of several hormones, growth factors and transcription factors. Recent experiments based on genetically modified mouse models, gene microarrays and pharmacological intervention indicate that the epidermal growth factor receptor (EGFR) system plays important roles in skeletal biology and pathology. This network, including a family of seven growth factors - the EGFR ligands - and the related tyrosine kinase receptors EGFR (ERBB1), ERBB2, ERBB3 and ERBB4, regulates aspects such as proliferation and differentiation of osteoblasts, chondrocytes and osteoclasts, parathyroid hormone-mediated bone formation and cancer metastases in bone. Here, we summarize and discuss the role of the EGFR and its ligands in skeletal biology and pathology.

The C-terminal cytoplasmic domain of human proEGF is a negative modulator of body and organ weights in transgenic mice

We generated transgenic mice to study the in vivo role of the cytoplasmic domain of human proEGF (proEGFcyt). Post-pubertal proEGFcyt transgenic (tg) mice displayed an up to 15% reduction in body weight, including smaller kidney and brain weights as compared to control littermates. Renal histology, gene expression profiles, and functional parameters were normal. In both sexes, serum levels of IGFBP-3 were reduced. Circulating IGF-I/IGF-II levels were unchanged. Histomorphological analysis revealed isolated foci of liver necrosis specific to proEGFcyt tg mice. In conclusion, we identified proEGF cytoplasmic domain as a novel modulator of whole body and organ-specific growth in mice.

Betacellulin overexpression in transgenic mice improves glucose tolerance and enhances insulin secretion by isolated islets in vitro

Betacellulin (BTC), a ligand of the epidermal growth factor receptor, has been shown to promote growth and differentiation of pancreatic beta-cells and to improve glucose metabolism in experimental diabetic rodent models. We employed transgenic mice (BTC-tg) to investigate the effects of long-term BTC overabundance on islet structure and glucose metabolism. Expression of BTC is increased in transgenic islets, which show normal structure and distribution of the different endocrine cell types, without pathological alterations. BTC-tg mice exhibit lower fasted glucose levels and improved glucose tolerance associated with increased glucose-induced insulin secretion. Surprisingly, quantitative stereological analyses revealed that, in spite of increased cell proliferation, the islet and beta-cell volumes were unchanged in BTC-tg mice, suggesting enhanced cell turnover. Insulin secretion in vitro was significantly higher in transgenic islets in medium containing high glucose (11.2 or 16.7mM) as compared to control islets. Our results demonstrate that long-term BTC overabundance does not alter pancreatic islet structure and beta-cell mass, but enhances glucose-induced insulin secretion in vivo as well as in vitro.

The epidermal growth factor receptor ligands at a glance

The epidermal growth factor receptor (EGFR) regulates key processes of cell biology, including proliferation, survival, and differentiation during development, tissue homeostasis, and tumorigenesis. Canonical EGFR activation involves the binding of seven peptide growth factors. These ligands are synthesized as transmembrane proteins comprising an N-terminal extension, the EGF module, a short juxtamembrane stalk, a hydrophobic transmembrane domain, and a carboxy-terminal fragment. The central structural and functional feature is the EGF module, a sequence containing six cysteines in a conserved spacement which is responsible for binding to the EGFR. While the membrane-anchored peptide can be biologically active by juxtacrine signaling, in most cases the EGF module is proteolytically cleaved (a process termed ectodomain shedding) to release the soluble growth factor, which may act in an endocrine, paracrine, or autocrine fashion. This review summarizes the structural and functional properties of these fascinating molecules and presents selected examples to illustrate their roles in development, physiology, and pathology.

EGF receptor in pancreatic beta-cell mass regulation

Pancreatic islet development is impaired in mice lacking EGFRs (epidermal growth factor receptors). Even partial tissue-specific attenuation of EGFR signalling in the islets leads to markedly reduced beta-cell proliferation and development of diabetes during the first weeks after birth. Out of the many EGFR ligands, betacellulin has been specifically associated with positive effects on beta-cell growth, through both increased proliferation and neogenesis. EGFR action is also necessary for the beta-cell mitogenic activity of the gut hormone GLP-1 (glucagon-like peptide 1). Finally, in vitro models demonstrate a central role for EGFR in transdifferentiation of pancreatic acinar and ductal cells into endocrine islet cells. EGFR thus plays an essential role in beta-cell mass regulation, but its mechanisms of action remain poorly understood.

Betacellulin stimulates growth of the mouse intestinal epithelium and increases adenoma multiplicity in Apc+/Min mice

We employed transgenic mice overexpressing betacellulin (BTC) to study its effects in the gut. BTC stimulated crypt cell proliferation and markedly increased intestinal size, while the crypt-villus architecture was preserved. Introduction of a dominant negative epidermal growth factor receptor (EGFR) completely abolished the intestinal hyperplasia. BTC increased polyp multiplicity but did not change the mean size or the histological quality of intestinal polyps in Apc(+/Min) mice. Analysis of intact and cleaved caspase-3 levels indicated that BTC has anti-apoptotic effects in the intestinal epithelium. We conclude that increased BTC levels support the survival of nascent adenomas in Apc(+/Min) mice, resulting in a larger total polyp number at later stages.

Betacellulin Overexpression in the Mouse Ovary Leads to MAPK3/MAPK1 Hyperactivation and Reduces Litter Size by Impairing Fertilization1

The epidermal growth factor receptor (EGFR) and its ligands are emerging as key molecules in regulating female reproduction. Here, we used a transgenic mouse model to evaluate whether and at which level of the reproduction cascade higher-than-normal levels of the EGFR ligand betacellulin (BTC) in the reproductive organs affect fertility. Western blots and immunohistochemistry revealed increased BTC levels in uterus and ovaries from transgenic females, particularly evident in granulosa cells of antral follicles. Onset of puberty, estrous cyclicity, and the anatomy and histology of reproductive organs at puberty were not altered as compared to control females. Fertility tests revealed a reduction (~50%) in litter size as the major reproductive deficit of transgenic females. Embryo implantation was delayed in transgenic females, but this was not the reason for the reduced litter size. Transgenic females produced a normal number of oocytes after natural ovulation. The in vivo fertilization rate was significantly reduced in untreated transgenic females but returned to normal levels after superovulation. Impaired oocyte fertilization in the absence of superovulation treatment was associated with MAPK3/MAPK1 hyperactivation in BTC transgenic ovaries, whereas similar levels of MAPK3/MAPK1 activation were detected in transgenic and control ovaries after superovulation treatment. Thus, tight regulation of MAPK3/MAPK1 activity appears to be essential for appropriate granulosa cell function during oocyte maturation. Our study identified hitherto unknown effects of BTC overabundance in reproduction and suggests BTC as a novel candidate protein for the modulation of fertility.

Systemic overexpression of growth hormone (GH) in transgenic FVB/N inbred mice: an optimized model for holistic studies of molecular mechanisms underlying GH-induced kidney pathology

Transgenic mice overexpressing growth hormone (GH) display a plethora of phenotypic alterations and provide unique models for studying and influencing consequences of chronic GH excess. Since the first report on GH transgenic mice was published in 1982, many different mouse models overexpressing GH from various species at different levels and with different tissue specificities were established, most of them on random-bred or hybrid genetic background. We have generated a new transgenic mouse model on FVB/N inbred background, expressing bovine (b) GH under the control of the chicken beta-actin promoter (cbetaa). cbetaa-bGH transgenic mice exhibit ubiquitous expression of bGH mRNA and protein and circulating bGH levels in the range of several microg/ml, resulting in markedly stimulated growth and the characteristic spectrum of pathological lesions which were described in previous GH overexpressing mouse models. Importantly, a consistent sequence of renal alterations is observed, mimicking progressive kidney disease in human patients. The novel, genetically standardized GH transgenic mouse model is ideal for holistic transcriptome and proteome studies aiming at the identification of the molecular mechanisms underlying GH-induced pathological alterations especially in the kidney. Moreover, genetically defined cbetaa-bGH mice facilitate random mutagenesis screens for modifier genes which influence the effects of chronic GH excess and associated pathological lesions.

Validation of HB-EGF and amphiregulin as targets for human cancer therapy

Aberrant expression levels of epidermal growth factor receptor (EGFR) and its cognate ligands have been recognized as one of the causes of cancer progression. To investigate the validity of EGFR ligands as targets for cancer therapy, we examined the expression of EGFR ligands and in vitro anti-tumor effects of small interference RNA (siRNA) for EGFR ligands in various cancer cells. HB-EGF expression was dominantly elevated in ovarian, gastric, and breast cancer, melanoma and glioblastoma cells, whereas amphiregulin was primarily expressed in pancreatic, colon, and prostate cancer, renal cell carcinoma and cholangiocarcinoma cells. Transfection of siRNAs for HB-EGF or amphiregulin into these cells significantly increased the numbers of apoptotic cells with attenuation of EGFR and ERK activation. In lung cancer cells, any EGFR ligand was not recognized as a validated target for cancer therapy. These results suggest that HB-EGF and amphiregulin are promising targets for cancer therapy.

Betacellulin regulates hair follicle development and hair cycle induction and enhances angiogenesis in wounded skin

Betacellulin (BTC) belongs to the EGF family, whose members play important roles in skin morphogenesis, homeostasis, and repair. However, the role of BTC in skin biology is still unknown. We employed transgenic mice overexpressing BTC ubiquitously to study its role in skin physiology. Immunohistochemistry revealed increased levels of BTC especially in the hair follicles and in the epidermis of transgenic animals. Expression of key markers of epithelial differentiation was unaltered, but keratinocyte proliferation was significantly increased. At post-natal day 1 (P1), transgenic mice displayed a significant retardation of hair follicle morphogenesis. At P17, when most follicles in control mice had initiated hair follicle cycling and had already entered into their first late catagen or telogen phase, all follicles of transgenic mice were still at the mid- to late catagen phases, indicating retarded initiation of hair follicle cycling. Healing of full-thickness excisional wounds and bursting strength of incisional wounds were similar in control and transgenic mice. However, an increase in the area covered by blood vessels at the wound site was detected in transgenic animals. These results provide evidence for a role of BTC in the regulation of epidermal homeostasis, hair follicle morphogenesis and cycling, and wound angiogenesis.

Betacellulin inhibits amylase and glucagon production and promotes beta cell differentiation in mouse embryonic pancreas

AIMS/HYPOTHESIS

Betacellulin, a member of the epidermal growth factor family, is expressed in the pancreas and is thought to regulate differentiation of beta cells during development. The aim of the present study was to investigate the effects of exogenous betacellulin on the development of the mouse embryonic pancreas.

MATERIALS AND METHODS

We used an in vitro culture model system based on the isolation and culture of the dorsal embryonic pancreas from day 11.5 embryos. Cultures were treated for up to 10 days with 10 ng/ml betacellulin and then analysed for changes in the expression of pancreatic exocrine, endocrine and ductal markers.

RESULTS

Pancreases developed in culture and expressed the full complement of exocrine (both acinar and ductal) and endocrine cell types. Betacellulin enhanced branching morphogenesis and the proliferation of mesenchyme, increased Pdx1 and insulin production and inhibited the production of the exocrine cell marker amylase and the endocrine hormone glucagon.

CONCLUSIONS/INTERPRETATION

These results suggest betacellulin has distinct and separate effects on exocrine, endocrine and ductal differentiation. In the future, betacellulin could perhaps be utilised to increase the production of beta cells from embryonic pancreatic tissue for therapeutic transplantation.

EGF-like ligands stimulate osteoclastogenesis by regulating expression of osteoclast regulatory factors by osteoblasts: implications for osteolytic bone metastases

Epidermal growth factor (EGF)-like ligands and their receptors constitute one of the most important signaling networks functioning in normal tissue development and cancer biology. Recent in vivo mouse models suggest this signaling network plays an essential role in bone metabolism. Using a coculture system containing bone marrow macrophage and osteoblastic cells, here we report that EGF-like ligands stimulate osteoclastogenesis by acting on osteoblastic cells. This stimulation is not a direct effect because osteoclasts do not express functional EGF receptors (EGFRs). Further studies reveal that EGF-like ligands strongly regulate the expression of two secreted osteoclast regulatory factors in osteoblasts by decreasing osteoprotegerin (OPG) expression and increasing monocyte chemoattractant protein 1 (MCP1) expression in an EGFR-dependent manner and consequently stimulate TRAP-positive osteoclast formation. Addition of exogenous OPG completely inhibited osteoclast formation stimulated by EGF-like ligands, while addition of a neutralizing antibody against MCP-1 exhibited partial inhibition. Coculture with bone metastatic breast cancer MDA-MB-231 cells had similar effects on the expression of OPG and MCP1 in the osteoblastic cells, and those effects could be partially abolished by the EGFR inhibitor PD153035. Because a high percentage of human carcinomas express EGF-like ligands, our findings suggest a novel mechanism for osteolytic lesions caused by cancer cells metastasizing to bone.

Roles of epidermal growth factor family in the regulation of postnatal somatic growth

Ligands of the epidermal growth factor receptor (EGF-R), known to be important for supporting tissue development particularly in the gut and brain, have also been implicated in regulating postnatal somatic growth. Although optimal levels of both milk-borne and endogenous EGF-R ligands are important for supporting postnatal somatic growth through regulating gastrointestinal growth and maturation, supraphysiological levels of EGF-R ligands can cause retarded and disproportionate growth and alter body composition because they can increase growth of epithelial tissues but decrease masses of muscle, fat, and bone. Apart from their indirect roles in influencing growth, possibly via regulating levels of IGF-I and IGF binding proteins, EGF-R ligands can regulate bone growth and modeling directly because they can enhance proliferation but suppress maturation of growth plate chondrocytes (for building a calcified cartilage scaffold for bone deposition), stimulate proliferation but inhibit differentiation of osteoblasts (for depositing bone matrix), and promote formation and function of osteoclasts (for resorption of calcified cartilage or bone). In addition, EGF-like ligands, particularly amphiregulin, can be strongly regulated by PTH, an important regulatory factor in bone modeling and remodeling. Finally, EGF-R ligands can regulate bone homeostasis by regulating a pool of progenitor cells in the bone marrow through promoting proliferation but suppressing differentiation of bone marrow mesenchymal stem cells.

Neogenesis and proliferation of beta-cells induced by human betacellulin gene transduction via retrograde pancreatic duct injection of an adenovirus vector

Betacellulin (BTC) has been shown to have a role in the differentiation and proliferation of beta-cells both in vitro and in vivo. We administered a human betacellulin (hBTC) adenovirus vector to male ICR mice via retrograde pancreatic duct injection. As a control, we administered a beta-galactosidase adenovirus vector. In the mice, hBTC protein was mainly overexpressed by pancreatic duct cells. On immunohistochemical analysis, we observed features of beta-cell neogenesis as newly formed insulin-positive cells in the duct cell lining or islet-like cell clusters (ICCs) closely associated with the ducts. The BrdU labeling index of beta-cells was also increased by the betacellulin vector compared with that of control mice. These results indicate that hBTC gene transduction into adult pancreatic duct cells promoted beta-cell differentiation (mainly from duct cells) and proliferation of pre-existing beta-cells, resulting in an increase of the beta-cell mass that improved glucose tolerance in diabetic mice.