Lung explants feature epithelial branching with neuronal arborisation. (A) Axons are visible projecting to each lobe in live lung explants from the microtubule-associated protein tau eGFP (MAPT) mouse line. The vagus nerve has been removed for clarity. Lungs were cultured to assess if nerves continue to arborise with the epithelium following explantation. A fresh explant is seen in brightfield (B) and epifluorescence (C) to visualise the nerves. After 46 hours in culture, the same lung has branched considerably (D, brightfield). (E) By epifluorescence, the nerves are still present with axons projecting along the epithelial branches (examples indicated by white arrowheads). Scale bars = 200 μm. eGFP, enhanced green fluorescent protein.