17 research outputs found
Leukemia Inhibitory Factor in Rat Fetal Lung Development: Expression and Functional Studies
Background: Leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) are members of the family of the glycoprotein 130 (gp130)-type cytokines. These cytokines share gp130 as a common signal transducer, which explains why they show some functional redundancy. Recently, it was demonstrated that IL-6 promotes fetal lung branching. Additionally, LIF has been implicated in developmental processes of some branching organs. Thus, in this study LIF expression pattern and its effects on fetal rat lung morphogenesis were assessed. Methodology/Principal Findings: LIF and its subunit receptor LIFRa expression levels were evaluated by immunohistochemistry and western blot in fetal rat lungs of different gestational ages, ranging from 13.5 to 21.5 days post-conception. Throughout all gestational ages studied, LIF was constitutively expressed in pulmonary epithelium, whereas LIFRa was first mainly expressed in the mesenchyme, but after pseudoglandular stage it was also observed in epithelial cells. These results point to a LIF epithelium-mesenchyme cross-talk, which is known to be important for lung branching process. Regarding functional studies, fetal lung explants were cultured with increasing doses of LIF or LIF neutralizing antibodies during 4 days. MAPK, AKT, and STAT3 phosphorylation in the treated lung explants was analyzed. LIF supplementation significantly inhibited lung growth in spite of an increase in p44/42 phosphorylation. On the other hand, LIF inhibition significantly stimulated lung growth via p38 and Akt pathways
Deletion of Frs2α from the ureteric epithelium causes renal hypoplasia
Fibroblast growth factor receptor 2 (Fgfr2) signaling is critical in maintaining ureteric branching architecture and mesenchymal stromal morphogenesis in the kidney. Fibroblast growth factor receptor substrate 2α (Frs2α) is a major docking protein for Fgfr2 with downstream targets including Ets variant (Etv) 4 and Etv5 in other systems. Furthermore, global deletion of Frs2α causes early embryonic lethality. The purpose of the study was to determine the role of Frs2α in mediating Fgfr2 signaling in the ureteric epithelium. To that end, we generated mice with conditional deletion of Frs2α in the ureteric epithelium (Frs2αUB−/−) and mice with point mutations in the Frs2α binding site of Fgfr2 (Fgfr2LR/LR). Frs2αUB−/− mice developed mild renal hypoplasia characterized by decreased ureteric branching morphogenesis but maintained normal overall branching architecture and had normal mesenchymal stromal development. Reduced nephron endowment in postnatal mutant mice was observed, corresponding with the reduction in branching morphogenesis. Furthermore, there were no apparent renal abnormalities in Fgfr2LR/LR mice. Interestingly, Etv4 and Etv5 expression was unaltered in Frs2αUB−/− mice, as was Sprouty1, an antagonist of Frs2α signaling. However, Ret and Wnt11 (molecules critical for ureteric branching morphogenesis) mRNA levels were lower in mutants vs. controls. Taken together, these findings suggest that Fgfr2 signals through adapter molecules other than Frs2α in the ureteric epithelium. Furthermore, Frs2α may transmit signals through other receptor kinases present in ureteric epithelium. Finally, the renal hypoplasia observed in Frs2αUB−/− mice is likely secondary to decreased Ret and Wnt11 expression