Fig. 2

Illustrations of experimental timeline and visualisation of grafted mDA neurons in the host brain. 6-hydroxydopamine (6-OHDA) was injected unilaterally into the left SNpc at week 0 (Wk 0). Three weeks later (Wk 3), dopaminergic precursors derived from hiPSCs were transplanted into the same area. In vivo extracellular electrophysiological recordings were performed between 9 months (Wk 36) and 12 months (Wk 44) post-transplantation. (A) Coronal brain section showing dopamine cell loss induced by the 6-OHDA injection into the left SNpc. (B) Representative images of TH⁺ and HuNu⁺ neurons within the graft, 9 months after transplantation. The labelling shows the localisation of TH⁺ neurons (in red, a), the transplant identified by HuNu nuclear labelling (in green, b), and the merged image of the TH⁺/HuNu⁺ (c). High-magnification images within the white frame highlight TH⁺ neurons [1], HuNu + cells [2], and TH⁺ neurons derived from hiPSCs (indicated by white arrows) in [3]. (C, D) Representative images of double immunostainings for TH (green) and hNCAM (red) along the nigrostriatal pathway through the medial forebrain bundle (MFB) (C; AP: -1.8 from bregma) and in the dorsal striatum (dStr) (D; AP: +0.4 from bregma) at 12 months after transplantation. Double-labeled TH⁺/hNCAM⁺ fibers indicate axonal projections originating from human grafted mDA-neurons. The schematic drawings were adapted from The Paxinos and Franklin’s mouse brain atlas [55]. Abbreviations: SNpc, substantia nigra pars compacta; VTA, ventral tegmental area; AP, antero-posterior; CPu, caudate putamen; MFB, medial forebrain bundle; dStr, dorsal striatum