The amounts of RNAs were higher in early stages of gestation. == Conclusions == E-cadherin is widely expressed in bronchial and alveolar epithelial cells. during pseudo-glandular period and to a lesser degree also in the canalicular period. -catenin was positive in pretype II cells as well as in type I and type II pneumocytes within alveoli. RT-PCR analyses revealed detectable amounts of RNAs of E- and N-cadherin and -catenin in all cases studied. The amounts of RNAs were higher in early stages of gestation. == Conclusions == E-cadherin is widely expressed in bronchial and alveolar epithelial cells. N-cadherin exhibit extensive epithelial positivity in bronchial epithelial cells during early lung development. The presence of -catenin was observed in several cell types with a distinct location in tissue and cells in various gestational stages, indicating that it possesses several roles during lung development. The expressions of protein and mRNAs of E- and N-cadherin and -catenin were higher in early gestation compared to of the end. Moreover, the expressions of ETC-1002 these factors were higher during the lung development than in the adult human lung. == Background == There is still little detailed knowledge of how cells differentiate during ontogenesis in the lung as well as in pulmonary diseases. It has been assumed that signalling processes occuring during pulmonary fibrosis and lung cancer may share similarities with the various stages of human lung development, thus by studying lung development it might be possible to acquire valuable information that may be useful when researching fibrotic and neoplastic lung diseases [1]. The epithelial changes are regulated by the extracellular matrix (ECM), which is an essential element in the process of branching morphogenesis, and also participating in the control of cell phenotype expression. In our previous studies, we have observed that the levels of several ECM proteins e.g. tenascin-C and precursors of collagen I and III are increased in certain localizations during human lung development as well as in fibrotic lung disorders when compared to the healthy adult normal lung [2-5]. Cells are connected with each other or the ECM in different ways but it is clear that adhesion molecules are extremely important in cellular junctions. The cadherins represent an important subclass of adhesion molecules [6]. The cytoplasmic domain of cadherins interacts with catenins, and this complex associates with actin filaments [7]. The cadherin superfamily consists of MAT1 several members and one of these, E-cadherin is expressed in epithelial cells and it is nowadays a commonly used marker of cell epithelial phenotype in studies focusing on the epithelial-mesenchymal transition (EMT) [8]. N-cadherin was originally found to be expressed in neural and muscle cells, but subsequently it is observed be an element of mesenchymal cells [9]. In studies investigating the EMT, N-cadherin has been used as a marker of mesenchymal differentiation [8]. Specific cadherins have been shown to directly stimulate cellular differentiation into certain types of tissue [10]. Recently, expression of N-cadherin has been observed to be present in epithelial lung tumors in addition of E-cadherin and -catenin [11]. -catenin serves many roles in the maintenance of cell architecture, for example it can bind to the cytoplasmic tail of E-cadherin. The WNT/-catenin signal transduction pathway has been shown to control embryonic patterning [12]. The cell specific expression profile of E- and N-cadherin during developing human lung is still unclear, though the role of -catenin in lung organogenesis has been evaluated more extensively [13]. A previous study indicated that -catenin signalling was required for the formation of the distal, but not the proximal, airways, and that the excision of -catenin in epithelial cells caused respiratory failure and death [14]. The aim of the immunohistochemical study was to examine the cell-specific expression of E- and N-cadherin and -catenin in normal human developing lung at different gestational ages i.e. from week 12 to week 40 during the pseudoglandular, ETC-1002 canalicular, saccular and alveolar periods. We hypothesized that the expression and localization of these factors could ETC-1002 vary during the different developmental periods. In addition to protein localization by immunohistochemistry, the amounts of RNAs were evaluated in some cases by quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR). == Methods == == Patients and handling of specimens == Samples of lung.