TH and Parkinson disease: In the histological analysis, both PD groups exhibited significant decreases in striatal TH fibre density (STR: A1 = 50.07 ± 4.82%, n = 9; A5 = 31.41 ± 1.68%, n = 5) and in nigral DA cell counts (SNC: A1 = 38.03 ± 2.08%, n = 9; A5 = 22.00 ± 2.57%, n = 5; Fig. 1g, h; Supplementary Fig. 2b).