Fig. 2: AAV-TH-hαSyn or αSyn pre-formed fibrils (PFF) increase corresponding immunostaining in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA).

A Experimental design: Mice received unilateral injections of either AAV1-TH-hαSyn (1 µL) or αSyn PFF (2 µg/1 µL; 1µL per hemisphere; 0.5µL in the VTA and the SNc) into the midbrain. B Representative coronal section of the ventral midbrain (SNc and VTA), showing the AAV1-TH-hαSyn injected (ipsilateral; right) and non-injected (contralateral; left) hemispheres. Four weeks post-injection (C–F), immunostaining with Syn211 (detecting hαSyn) shows colocalization in TH+ neurons on the injected side in the SNc (D) and VTA (F), but not on the non-injected side respectively (C, E). The same timepoint but following injection with αSyn PFF (G-J), 81 A (detecting phosphorylated αSyn aggregates) shows punctate signals localized within TH⁺ neurons on the injected side in the SNc (H) and VTA (J), but not on the non-injected side respectively (G, I). These data confirm the presence of hαSyn and aggregated αSyn in both the VTA and SNc. K, M Four weeks after injection of either AAV1-TH-hαSyn or αSyn PFF, there was no significant change in the number of TH⁺ neurons in the SNc or VTA. (L, N) Similarly, no differences were observed in the number of TH⁺ and FOX3⁺ neurons in the SNc or VTA. Error bars represent mean ± SEM. (n = 3 independent biological replicates, one-way ANOVA and t-test, *p < 0.05) Scale bars: 250 µm (B); 20 µm (C–J).