Patched1 patterns fibroblast growth factor 10 and forkhead box F1 expression during pulmonary branch formation

Hedgehog (Hh) signalling, Fibroblast grovvth factor 10 (Fgr10) and Forkhead box Fl (Foxf1) are each individually important for directing pulmonary branch formation but theft interactions are not well understood. Here we demonstrate that Hh signalling is vital in regulating Foxf1 and Fgf10 expression during branching. The Hedgehog receptor Patched1 (Ptchl) was conditionally inactivated in the lung mesenchyme by Denno1-Cre in vivo or using a recombinant Cie recombinase protein (HNCre) in lung cultures resulting in cell autonomous activation of Hh signalling. Homozygous mesenchymal Ptchl deleted embryos (DertnolCre+/-; Ptch1(lox/lox)) showed secondary branching and lobe formation defects. Fgf 10 expression is spatially reduced in the distal tip of Derrno/Cre+/-; Ptch1(lox/lox) lungs and addition of Fgf10 recombinant protein to these lungs in culture has shown partial restoration of branching, indicating Ptchl function patterns Fgf10 to direct lung branching. Foxil expression is upregulatecl in Dermol Cre+/-; Ptch1(lox/lox) lungs, suggesting Foxf1 may mediate Hh signalling effects in the lung mesenchyme. In vitro HNCre-mecliated Ptchl deleted lung explants support the in vivo observations, with evidence of mesenchyme hyperproliferation and this is consistent with the previously reported role of Hh signalling in maintaining mesenchymal cell survival. Consequently it is concluded that during early pseudoglandular stage of lung development Ptchl patterns Fgf10 and regulates Foxf 1 expression in the lung mesenchyme to direct branch formation and this is essential for proper lobe formation and lung function. (C) 2017 Elsevier B.V. All rights reserved