Stadien- und gewebespezifische pränatale Expression des porzinen cystic fibrosis transmembrane conductance regulator in Trachea, Lunge und Dickdarm – Hinweise auf seine Rolle in der Organogenese?

Beschreibung

The stage and tissue specific expression pattern of the porcine cystic fibrosis transmembrane conductance regulator in porcine fetuses as well as newborn and adult pigs in the trachea, lung and colon. Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes for an epithelial chloride channel. CF is still an incompletely understood, multisystemic disease leading to exocrinopathies in various organs. Despite improved treatment methods, affected patients die at an average age of 50 years, predominantly due to progressive pneumonia. Structural changes in the respiratory tract are already present at birth, such as the deformation of the trachea and wall thickening of large bronchi, long before pneumonia develops. Identical malformations have also been found in pig models of CF, in which porcine CFTR (pCFTR) has been genetically deleted or functionally impaired by genetical modifications. The significance of this innate phenotype for the pathogenesis of CF is still unclear. However, these observations suggest a role of CFTR already in prenatal organ development. Anyhow, only few data regarding prenatal CFTR expression are available to date. The aim of this study was to characterize the time-dependent tissue and cellular expression patterns of CFTR during prenatal development in the lower respiratory and large intestinal tract of healthy wild type pigs. The results were compared with available data concerning prenatal CFTR expression in humans. These analyses included fetuses at different gestation periods, newborn piglets, and adult sows. The tissue expression of CFTR was quantified at the mRNA level by reverse transcriptase quantitative polymerase chain reaction, the cellular expression pattern was determined by immunohistochemistry. Furthermore, the tissue expression of the sodium channel pSCNN1B, which also plays a role in the pathogenesis of CF, as well as cellular markers for goblet cells (pCLCA1) and other epithelial cells (pCLCA4a) were analyzed. With one exception, all investigated genes could be detected at the mRNA level at any time from the end of the first trimenon to 24 hours post partum and in adult sows. Only in the alveolar-rich main lobe of the lung pCLCA4a could not be detected in all fetuses in the second trimenon, which is probably related to a too low expression. The expression analysis of pCFTR and pSCNN1B revealed significant time points, as in humans. For example, an increased expression of pCFTR and pSCNN1B was observed in the lower respiratory tract and colon in the second trimenon. In addition, there was a noticeable reduction in the expression of pCFTR in the alveolar-rich main lobe and an increase in the expression of pSCNN1B in the bronchus-rich lung lobe at birth. The mRNA of the two analysed marker genes pCLCA1 and pCLCA4a were also found to be increased in the second trimenon, which is probably related to the differentiation of the individual cell types at this time. pCFTR was detectable via immunohistochemistry in epithelial cells of the colon at any time. In the trachea, however, the pCFTR signal could only be detected in newborn piglets and adult sows, but not in prenatal stages. This may be due to the lack of sensitivity of the antibody. Prenatal pCFTR expression thus showed a characteristic, time-dependent expression pattern comparable to human CFTR, characterized by increased expression in the second trimenon in the respiratory tract and colon. Therefore, CFTR may be relevant for organogenesis at this specific developmental stage. Future studies at this specific timepoint should be performed in CF pig fetuses to determine if the onset of congenital organ malformations starts at this time.

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Stefanie Binder

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Dickdarm Embryologie Luftröhre Lunge Mukoviszidose Schweine Tiermodelle Transmembranleitfähigkeitsregulator (MeSH) animal models colon cystic fibrosis embryology lungs pigs reverse transkriptase pcr

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