Funktionen der Tyrosinphosphatase Shp2 während des postnatalen Skelettmuskelwachstums und der Regeneration

Shp2 is a tyrosine phosphatase that mediates signals provided by many tyrosine kinase receptors. The experiments performed in this study revealed an important role for Shp2 in early postnatal muscle growth and adult muscle regeneration. Shp2 mutation in fetal myogenic progenitors and adult Satellite cells resulted in major changes in their proliferative capacities. I used pharmacological inhibitors, as well as genetics to show that Mapk/Erk activity depends on Shp2 in myogenic C2C12 cells or in neonatal and adult Satellite cells. I introduced a conditional Shp2 mutation using different Cre lines. When Shp2 was ablated during early fetal myogenesis, changes in proliferation were only observed in the postnatal period. Cultures of isolated Shp2 mutant Satellite cells demonstrated that the proliferative deficit is cell-autonomous and observed in postnatal but not fetal cells. This suggests that Satellite cell proliferation is regulated by distinct mechanisms in the pre- and postnatal period. I also introduced the conditional Shp2 mutation in adult Satellite cells and observed that these mutant Satellite cells are unable to repair muscle upon injury. In vivo, it can be difficult to follow the cells during the repair process. I therefore used cultures of myofibers and adherent Satellite cells to study the activation, proliferation and differentiation of adult Satellite cells in the absence of Shp2. This demonstrated that early steps in Satellite cell activation were Shp2-independent, but the cells were unable to proliferate and quickly withdrew from the cell cycle. I was able to rescue this proliferative deficit by expression of a constitutively active Mapkk (Mek1DD). This is in accordance with my biochemical analyses that had indicated that Shp2 is mainly necessary for Mapk/Erk activity. Various growth factors have been implicated in muscle regeneration. Several of these growth factors activate Mapk/Erk signaling by their tyrosine kinase receptors in Satellite cells. Nevertheless, mutations of single receptors in Satellite cells do not impair muscle regeneration as severe as mutation of Shp2. Thus, Shp2 likely regulates the converging inputs of several receptor tyrosine kinases into the Mapk/Erk cascade.Shp2 ist eine Tyrosinphosphatase, die die Signale vieler Rezeptor- Tyrosinkinasen vermittelt. In dieser Studie konnte gezeigt werden, dass Shp2 postnatales Muskelwachstums und Muskelregeneration im adulten Tier reguliert. Mutation von Shp2 in fötalen Muskelvorläuferzellen oder adulten Satellitenzellen führte zu stark reduzierter Proliferation. Mittels pharmakologischer Inhibitoren und mit genetischen Studien konnte ich zeigen, dass Shp2 den Mapk/Erk Signalweg in myogenen C2C12 Zellen sowie neonatalen und adulten Satellitenzellen kontrolliert. Ich setzte unterschiedliche Cre Linien ein, um Shp2 in Muskelvorläuferzellen in fötalen oder adulten Mäusen zu mutieren. Mutation von Shp2 in der fötalen Myogenese führte zu einem starken Proliferationsdefizit von Satellitenzellen im postnatalen Muskel. Kulturen isolierter myogener Vorläuferzellen zeigten, dass es sich um ein zell- autonomes Defizit handelt das in postnatalen, nicht aber in fötalen Zellen auftritt. Dies legt den Schluss nahe, dass unterschiedliche molekulare Mechanismen genutzt werden um Proliferation von prä- und postnatalen myogenen Vorläuferzellen zu steuern. Zusätzlich führte ich eine konditionelle Shp2 Mutation in adulten Satellitenzellen ein und konnte eine stark beeinträchtigte Muskelregeneration beobachten. Es ist sehr aufwändig, solche Effekte und die verantwortlichen Mechanismen in vivo zu untersuchen. Ich setze deshalb Kulturen isolierter Muskelfasern und der assoziierten Satellitenzellen ein, um Aktivierung, Proliferation und Differenzierung der Stammzellen im Detail zu untersuchen. Während die initialen Schritte der Aktivierung unabhängig von Shp2 sind, war die Proliferation der Satellitenzellen stark beeinträchtigt und die Zellen traten verfrüht aus dem Zellzyklus aus. Expression einer konstitutiv aktiven Mapkk (MEK1DD) glich die defizitäre Proliferation aus. Dies war in Übereinstimmung mit meinen biochemischen Analysen, die darauf hinwiesen, dass Shp2 hauptsächlich die Aktivierung des Mapk/Erk Signalwegs reguliert. Viele Wachstumsfaktoren regulieren die Muskelregeneration. Einige dieser Faktoren aktivieren Rezeptor-Tyrosinkinasen und den Mapk/Erk Signalweg. Die Mutationen dieser Rezeptoren führen allerdings zu weniger starken Defiziten in der Muskelregeneration als die Mutation von Shp2. Dies legt den Schluss nahe, das Shp2 die Signale verschiedener Rezeptoren während der Muskelregeneration weiterleite

Vascular Remodeling Is a Crucial Event in the Early Phase of Hepatocarcinogenesis in Rodent Models for Liver Tumorigenesis

The investigation of hepatocarcinogenesis is a major field of interest in oncology research and rodent models are commonly used to unravel the pathophysiology of onset and progression of hepatocellular carcinoma. HCC is a highly vascularized tumor and vascular remodeling is one of the hallmarks of tumor progression. To date, only a few detailed data exist about the vasculature and vascular remodeling in rodent models used for hepatocarcinogenesis. In this study, the vasculature of HCC and the preneoplastic foci of alteration (FCA) of different mouse models with varying genetic backgrounds were comprehensively characterized by using immunohistochemistry (CD31, Collagen IV, αSMA, Desmin and LYVE1) and RNA in situ hybridization (VEGF-A). Computational image analysis was performed to evaluate selected parameters including microvessel density, pericyte coverage, vessel size, intratumoral vessel distribution and architecture using the Aperio ImageScope and Definiens software programs. HCC presented with a significantly lower number of vessels, but larger vessel size and increased coverage, leading to a higher degree of maturation, whereas FCA lesions presented with a higher microvessel density and a higher amount of smaller but more immature vessels. Our results clearly demonstrate that vascular remodeling is present and crucial in early stages of experimental hepatocarcinogenesis. In addition, our detailed characterization provides a strong basis for further angiogenesis studies in these experimental models

Evening Telegram (St. John's, N.L.), 1912-10-16

The Evening Telegram began publication in St. John's on 3 April 1879 and remains in print today under the title The Telegram. It was published daily except Sunday through to 1958, the frequency changing thereafter. -- The total collection has been split into several parts; this portion contains from 1900 - 28 February 1913, and covers the years of the First World War from 2 March 1914 - 1918. -- Missing issues: 19 January - 18 February 1910

Oscillations of MyoD and Hes1 proteins regulate the maintenance of activated muscle stem cells

International audienc

TRAIL receptor targeting agents potentiate PARP inhibitor efficacy in pancreatic cancer independently of BRCA2 mutation status

Chemotherapy, the standard treatment for pancreatic ductal adenocarcinoma (PDAC), has only a modest effect on the outcome of patients with late-stage disease. Investigations of the genetic features of PDAC have demonstrated a frequent occurrence of mutations in genes involved in homologous recombination (HR), especially in the breast cancer susceptibility gene 2 (BRCA2). Olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor, is approved as a maintenance treatment for patients with advanced PDAC with germline BRCA1/2 mutations following a platinum-containing first-line regimen. Limitations to the use of PARP inhibitors are represented by the relatively small proportion of patients with mutations in BRCA1/2 genes and the modest capability of these substances of inducing objective response. We have previously shown that pancreatic cancer with BRCA2 mutations exhibits a remarkably enhanced sensitivity towards tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL) receptor-stimulating agents. We thus aimed to investigate the effect of combined treatment with PARP inhibitors and TRAIL receptor-stimulating agents in pancreatic cancer and its dependency on the BRCA2 gene status. The respective effects of TRAIL-targeting agents and the PARP inhibitor olaparib or of their combination were assessed in pancreatic cancer cell lines and patient-derived organoids. In addition, BRCA2-knockout and -complementation models were investigated. The effects of these agents on apoptosis, DNA damage, cell cycle, and receptor surface expression were assessed by immunofluorescence, Western blot, and flow cytometry. PARP inhibition and TRAIL synergized to cause cell death in pancreatic cancer cell lines and PDAC organoids. This effect proved independent of BRCA2 gene status in three independent models. Olaparib and TRAIL in combination caused a detectable increase in DNA damage and a concentration-dependent cell cycle arrest in the G2/M and S cell cycle phases. Olaparib also significantly increased the proportion of membrane-bound death receptor 5. Our results provide a preclinical rationale for the combination of PARP inhibitors and TRAIL receptor agonists for the treatment of pancreatic cancer and suggest that the use of PARP inhibitors could be extended to patients without BRCA2 mutations if used in combination with TRAIL agonists