Morphogenesis Of Epithelial Cells And Developmental Expression Of Toll-like Receptor Signaling Of Guinea Pig Lung

The guinea pig is one of ideal experimental animal models for pulmonary diseases, such as asthma and tuberculosis. Additionally, the guinea pig is a commonly used model for understanding the molecular mechanisms of innate immunity and pathogenesis of respiratory diseases. Therefore, the developmental expression of toll-like receptors (TLRs) signaling, as well as the formation of epithelial cells in guinea lung were explored in this study.Histochemistry and immunohistochemistry staining were used for evaluation of the morphogenesis and the composition of epithelial cell types during lung development in guinea pig, and a quantitative revised transcription PCR (qRT-PCR) and immunoblotting (WB) assays were used to access the developmental expression of TLR signaling. Our results showed that the basal cells and type â…¡ pneumonocyte could be observed at prenatal stage of embryonic day45(E45d), and ciliated cells and clara cells could be formed on E52d, which implicated that the guinea ping lung was in pseudoglandular and canalicular stages on E45d and E52d, respectively; the lung was morphologically in the terminalsaccular stage from E59d to new born; and were in the alveolar stage from7d afterward.In addition, by using quantitative RT-PCR, TLR signaling TLR1, TLR2, TLR3, TLR4, TLR6, TLR7, TLR8, TLR9, TLR10, MyD88and TRAF6were detected in the lung of guinea pig at all evaluated stages in this study, including prenatal stages of E59d, E52d, E45d, and postnatal stages of0d (newborn), day7(7d),14d,28d, and adult (postnatal3months). Although various expression levels of each TLR signaling were found in different stages of the lung, the overall levels of expression for all examined TLR signaling molecules in prenatal stages were higher relative to that in postnatal animals. In this regard, the overall expressions of TLR1-10were gradually increased along with the development of lung; the highest expression of TLR4was observed on E52d, and followed by E45d; similarly, the highest expressions of MyD88and TRAF6were detected on E52d and E59d prenatal stages; while the expression of TLRs was significantly lower in the lungs of postnatal animals those from new born to3-month old, in comparison with the prenatal lungs. However, there was no statistical difference of the expression of a distinct TLR signaling was observed between the lungs from different postnatal stages. Additionally, the expression of TLR signaling was further validated by Western blot (WB) assay at protein level using appropriate antibodies.The results presented this study suggested that the lung of guinea pig was morphologically and functionally maturated with the proliferation and differentiation of epithelial cells during embryonic development; the relative higher levels of TLR signaling molecules in the prenatal lungs might imply the morphological and functional maturity of guinea pig lung with a well established ability of immune response; while a relative lower expression of TLR signaling in postnatal lungs might be beneficial to the body for preventing auto-injury from excessive immune responses, and being in a state of immunogenic recognition and triggering of a innate and/or acquired immune response. In conclusively, this study will provide useful information for investigating characteristics of developmental biology of pneumonocytes of guinea pigs and their potential roles in development of host innate immunity.