Paraffin embedded tissues were sectioned (10 µm section thickness) and mounted on superfrost slides. After deparaffinization and antigen retrieval in citrate buffer pH 6.0, immunofluorescence staining on sections was performed using rabbit polyclonal GFP antibody (#2555, 1:1000 dilution; Cell Signalling Technologies) with Alexa Fluor 488 conjugated goat anti-rabbit secondary antibody (#A-11034, 1:200 dilution; Thermo Fisher), to unambiguously detect eGFP transgene expression and differentiate from tissue background fluorescence.8 (link),14 (link) The slides were mounted using a mounting medium containing 4′,6-diamidino-2-phenylindole (DAPI) nuclear stain (Fluoro-Gel II, #17985; Electron Microscopy Sciences), and the slides were dried and sealed. Image acquisition was performed using a Zeiss fluorescence microscope under identical conditions (20× objective; laser intensity 30%; DAPI exposure time, 50 ms; GFP exposure time, 300 ms). Lumbar spinal cord sections were additionally co-stained for neuronal nuclei protein NeuN using mouse monoclonal NeuN antibody (#MAB377, 1:1000 dilution; Millipore) with Alexa Fluor 568–conjugated goat anti-mouse secondary antibody (#A-11031, 1:200 dilution; Thermo Fisher). The slides were then scanned using NanoZoomer S60 digital slide scanner (Hamamatsu).