Altered expression of Toll-like receptor 9 in the lung tissue of adult mice generated by in vitro embryo culture and embryo transfer

Children conceived through assisted reproductive technologies (ART) are more sensitive to asthma and allergic respiratory diseases compared with children born through natural pregnancy. Growing evidence suggests that Toll-like receptors (TLRs) play a role in asthma. We previously demonstrated that TLR9 expression is significantly downregulated in the lung tissue of mouse fetuses generated through ART. The present study therefore investigated whether altered expression of TLR9 is maintained in the lung tissue in the perinatal period and in adult mice conceived through in vitro embryo culture and embryo transfer. We also examined the expression pattern of TLR9 in lung tissue. The study comprised one control (CG) and one experimental group (EG). Mice comprising EG were generated through the transfer of in vitro-derived F2 blastocysts. Mice obtained from naturally ovulated females served as the CG. Quantitative real-time PCR (qRT-PCR) and immunohistochemistry/immunofluorescence analyses were employed to determine the expression of TLR9. qRT-PCR analyses demonstrated that expression of TLR9 decreased 1.38-fold in EG when compared with the CG. Immunohistochemistry/immunofluorescence analyses revealed that the expression pattern of TLR9 is similar between the groups. Simultaneous staining of sequential sections further elucidated that TLR9 is expressed in type II alveolar epithelial cells. It therefore appears that altered expression of TLR9 observed in the lung tissue of mouse fetuses generated through embryo culture and embryo transfer persists into adulthood. To what extent the findings of the present study apply to human ART warrants further investigations.