Päivi J. Miettinen

EGF-R regulates MMP function in fibroblasts through MAPK and AP-1 pathways

EGF‐R regulates cell proliferation, migration, and invasion in fibroblasts. However, the connection of EGF‐R with downstream signaling pathways mediating these responses has remained elusive. Here we provide genetic and biochemical evidence that EGF‐R‐ and AP‐1‐mediated signals are required for MMP expression and collagen contraction in fibroblasts. In EGF‐R (−/−) mouse embryonal fibroblasts, basal and inducible expression of several MMPs, including MMP‐2, ‐3, and ‐14 is impaired in comparison to wild‐type counterparts. The loss of MMP expression is associated with a suppression of EGF‐induced Erk and Jnk activities, and AP‐1 DNA‐binding and transactivation capacities. While inhibition of Jnk mainly prevents EGF‐induced phosphorylation of c‐Jun, inhibition of Erk pathway suppresses both the expression and phosphorylation of c‐Jun and c‐Fos proteins. Moreover, the expression of MMP‐3 and ‐14, and collagen contraction is partially prevented by Mek/Erk and Jnk inhibitors. However, Jnk inhibitor also suppresses cell growth independently of EGF‐R activity. The central role of AP‐1 as a mediator of EGF‐R signaling in fibroblasts is emphasized by the finding that expression of a dominant negative c‐Jun downregulates the expression of MMP‐3. Conversely, expression of a constitutively active Mek1 can induce MMP‐3 expression independently of upstream signals. The results indicate that ERK pathway and AP‐1 are downstream effectors of the EGF‐R‐mediated MMP‐3 expression and collagen contraction in fibroblasts. J. Cell. Physiol. 212: 489–497, 2007.

Transforming growth factor-α and epidermal growth factor expression in human fetal gastrointestinal tract

ABSTRACT: Epidermal growth factor (EGF) and transforming growth factor-α (TGF-α) are mitogenic to the intestinal epithelium. To further clarify their role in the developing human fetal gut, their expression was studied in fetuses at 15 to 20 wk of gestation. TGF-α mRNA was present throughout the gastrointestinal tract, most abundantly in the duodenum. EGF mRNA could be detected only with ribonuclease protection assay and reverse transcription-polymerase chain reaction analysis. The effect of EGF and TGF-α on TGF-α mRNA expression was studied by culturing explants of fetal jejunum, ileum, and colon for 7 d in Leibowitz L-15 medium supplemented with 100 μg/L of either EGF or TGF-α. EGF receptor-like immunoreactivity was detected in both the villi and the crypts. In the jejunum, exogenous EGF up-regulated TGF-α mRNA 3-fold. However, exogenous TGF-α reduced its own mRNA by 40%. No mature 6-kD TGF-α was detected in the culture medium by Western blotting, but precursor forms of approximately 30 and 68 kD were present. The ileum and colon did not respond to either growth factor. Besides the gut, TGF-α was expressed in the gallbladder, salivary gland, adrenals, brain, kidney, liver, and placenta. The data imply an important role for TGF-α and EGF in the developing intestine.

Sexual Function and Attitudes Toward Surgery After Feminizing Genitoplasty

PURPOSE Sexual function and attitudes toward surgery were evaluated in females who had undergone feminizing genitoplasty in childhood. MATERIALS AND METHODS Sexual function and attitudes toward surgery were assessed by a questionnaire in 24 females who had undergone genitoplasty in childhood. Of 16 females who were prenatally exposed to androgens 15 had congenital adrenal hyperplasia and 8 had androgen insensitivity. A total of 18 patients who had reached adulthood were compared with 900 age matched normal controls by using the Female Sexual Function Index questionnaire. RESULTS Of the 24 patients 19 had undergone clitoral reduction and 21 had undergone reconstruction of the vaginal introitus. Sigmoid bowel had been used in vaginal reconstruction in 5 patients. There were 17 patients who believed that the genital operation was performed at a proper age, 3 who thought it was done too late while none thought it was performed at too young an age. Two patients regretted the operation, 1 of whom had undergone clitoral resection without nerve preservation and the other had a sigmoid vagina. The control group had more often and earlier (median age 17 vs 19 years) experiences with sexual intercourse. Overall sexual function was similar in the sexually active controls and patients. Decreased sexual desire and problems in achieving orgasm were common but severe pain experiences during penetrative sex were rare in both groups. CONCLUSIONS Sexual intercoital relationships started later in females who underwent genital reconstruction in childhood. Early surgery is preferred by the patients and satisfactory sex life is possible in adulthood.

EGF receptor in pancreatic β-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.

EGF- and TGF-|[alpha]|-Like Peptides in Human Fetal Gut

ABSTRACT: The presence of epidermal growth factor (EGF) and transforming growth factor-α (TGFα) immunoreactivities in fetal human tissues was studied immunohistochemically at different gestational ages. EGF and TGFα immunoreactivities were detected from the 20th gestational wk. EGF immunoreactivity was limited to the small intestine, but TGFα immunoreactive cells were present in the colon also. According to radioreceptor assay, the intestine of a 19-wk-old human fetus contained 10 times more EGF receptor-binding substance than EGF, as measured by immunofluorometric assay. Chromatographic analysis suggests that TGFα-like peptides account for at least part of this activity, as so argues in favor of the presence of TGFα- and EGF-like peptides in the human fetal gut. Whether they are synthesized in the fetus is yet unknown.

Epidermal growth factor (EGF)-receptor signalling is needed for murine beta cell mass expansion in response to high-fat diet and pregnancy but not after pancreatic duct ligation

Aims/hypothesisEpidermal growth factor receptor (EGFR) signalling is essential for the proper fetal development of pancreatic islets and in the postnatal formation of an adequate beta cell mass. In this study we investigated the role of EGFR signalling in the physiological states of beta cell mass expansion in adults during metabolic syndrome and pregnancy, as well as in regeneration after pancreatic duct ligation.MethodsHeterozygous Pdx1-EGFR-dominant-negative (E1-DN) mice, which have a kinase-negative EGFR under the Pdx1 promoter, and wild-type mice were both subjected to a high-fat diet, pregnancy and pancreatic duct ligation.ResultsThe beta cell mass of wild-type mice fed the high-fat diet increased by 70% and the mice remained normoglycaemic; the E1-DN mice became diabetic and failed to show any compensatory beta cell mass expansion. Similarly, pregnant wild-type mice had four times more proliferating beta cells and a 75% increase in beta cell mass at mid-gestation, in contrast to the pregnant E1-DN mice, which did not show any significant beta cell compensation and were hyperglycaemic in an intraperitoneal glucose tolerance test. However, after pancreatic duct ligation, both the wild-type and E1-DN mice showed similar expression of Ngn3 (also known as Neurog3) and beta cell proliferation increased to a similar level in the ligated part of pancreas.Conclusions/interpretationsEGFR signalling is essential in beta cell mass expansion during a high-fat diet and pregnancy where replication is the primary mechanism for compensatory beta cell mass expansion. In contrast, EGFR signalling appears not to be crucial to increased beta cell proliferation after pancreatic duct ligation.

Weighing up β-cell mass in mice and humans: Self-renewal, progenitors or stem cells?

Understanding how beta-cells maintain themselves in the adult pancreas is important for prioritizing strategies aimed at ameliorating or ideally curing different forms of diabetes. There has been much debate over whether beta-cell proliferation, as a means of self-renewal, predominates over the existence and differentiation of a pancreatic stem cell or progenitor cell population. This article describes the two opposing positions based largely on research in laboratory rodents and its extrapolation to humans.

EGF-receptor regulates salivary gland branching morphogenesis by supporting proliferation and maturation of epithelial cells and survival of mesenchymal cells.

Epidermal growth factor receptor (EGF-R) regulates epithelial morphogenesis during development and is important for the proper branching of the lung, mammary gland, and pancreas. We analyzed the salivary gland phenotype of EGF-R-deficient mice and showed impaired growth, branching, and maturation of the epithelium. Furthermore, treatment of wild-type E13 salivary glands with gefitinib, a small molecular inhibitor of EGF-R, led to apoptosis of the mesenchyme. Interestingly, MMP2 and plasminogen activators were upregulated upon inhibition of EGF-R signaling. To summarize, we show that EGF-R is a physiological regulator of salivary gland development and its main function is to support the proliferation and maturation of the epithelium and the survival of the mesenchyme.

Prevalence and characteristics of diabetes among Somali children and adolescents living in Helsinki, Finland

Oilinki T, Otonkoski T, Ilonen J, Knip M, Miettinen PJ. Prevalence and characteristics of diabetes among Somali children and adolescents living in Helsinki, Finland.

EGFR Signaling Promotes β-Cell Proliferation and Survivin Expression during Pregnancy

Placental lactogen (PL) induced serotonergic signaling is essential for gestational β-cell mass expansion. We have previously shown that intact Epidermal growth factor –receptor (EGFR) function is a crucial component of this pathway. We now explored more specifically the link between EGFR and pregnancy-induced β-cell mass compensation. Islets were isolated from wild-type and β-cell-specific EGFR-dominant negative mice (E1-DN), stimulated with PL and analyzed for β-cell proliferation and expression of genes involved in gestational β-cell growth. β-cell mass dynamics were analyzed both with traditional morphometrical methods and three-dimensional optical projection tomography (OPT) of whole-mount insulin-stained pancreata. Insulin-positive volume analyzed with OPT increased 1.4-fold at gestational day 18.5 (GD18.5) when compared to non-pregnant mice. Number of islets peaked by GD13.5 (680 vs 1134 islets per pancreas, non-pregnant vs. GD13.5). PL stimulated beta cell proliferation in the wild-type islets, whereas the proliferative response was absent in the E1-DN mouse islets. Serotonin synthesizing enzymes were upregulated similarly in both the wild-type and E1-DN mice. However, while survivin (Birc5) mRNA was upregulated 5.5-fold during pregnancy in the wild-type islets, no change was seen in the E1-DN pregnant islets. PL induced survivin expression also in isolated islets and this was blocked by EGFR inhibitor gefitinib, mTOR inhibitor rapamycin and MEK inhibitor PD0325901. Our 3D-volumetric analysis of β-cell mass expansion during murine pregnancy revealed that islet number increases during pregnancy. In addition, our results suggest that EGFR signaling is required for lactogen-induced survivin expression via MAPK and mTOR pathways.