Generation and characterization of iPSC‐derived DAn.Figure 1A-GAfter iPSC‐based reprogramming of fibroblasts, we generated DAn from PD patients (n = 10) and gender‐ and age‐matched healthy controls (n = 4) using a 30‐day differentiation protocol. Blind to researcher, resulting iPSC‐derived DAn showed similar properties and maturation state in PD and controls. Specifically, studied iPSC‐derived DAn encompassed 30‐day ventromedial (vm)‐DAn‐enriched cultures of morphologically mature DAn showing typical bipolar morphology, lacking PD neural phenotypes, mostly of the A9 subtype, and showing properties of tyrosine hydroxylase (TH)+ mature neurons. Representative immunocytochemistry analyses of vmDAn from PD patients and controls showed that (A) TUJ1‐positive cells expressing neural tubulin III (TUJ1) co‐expressed TH (Scale bar, 25 μm); (B) co‐expressed the A9 subtype marker of inward rectifier K+ channel GIRK2 (Scale bar, 25 μm); (C) co‐expressed the A9 subtype marker of transcription factor Forkhead Box A2 (FOXA2) (Scale bar, 12.5 μm). A-GAfter iPSC‐based reprogramming of fibroblasts, we generated DAn from PD patients (n = 10) and gender‐ and age‐matched healthy controls (n = 4) using a 30‐day differentiation protocol. Blind to researcher, resulting iPSC‐derived DAn showed similar properties and maturation state in PD and controls. Specifically, studied iPSC‐derived DAn encompassed 30‐day ventromedial (vm)‐DAn‐enriched cultures of morphologically mature DAn showing typical bipolar morphology, lacking PD neural phenotypes, mostly of the A9 subtype, and showing properties of tyrosine hydroxylase (TH)+ mature neurons. Representative immunocytochemistry analyses of vmDAn from PD patients and controls showed that (D) The 1‐week neural progenitor cells (NPCs) from which iPSC‐derived DAn were generated strongly expressed DAn progenitor markers such as the nuclear‐related receptor 1 NURR1 (Scale bar, 12.5 μm). A-GAfter iPSC‐based reprogramming of fibroblasts, we generated DAn from PD patients (n = 10) and gender‐ and age‐matched healthy controls (n = 4) using a 30‐day differentiation protocol. Blind to researcher, resulting iPSC‐derived DAn showed similar properties and maturation state in PD and controls. Specifically, studied iPSC‐derived DAn encompassed 30‐day ventromedial (vm)‐DAn‐enriched cultures of morphologically mature DAn showing typical bipolar morphology, lacking PD neural phenotypes, mostly of the A9 subtype, and showing properties of tyrosine hydroxylase (TH)+ mature neurons. (E) We observed similar and comparable cell counts of total neurons in PD and controls as quantified by TUJ‐1/DAPI and of DAn as quantified by TH/TUJ1. Selected DAn cells were generated upon 2‐6 iPSC lines per subject (See methods). Error bars indicate SEM. C, control; TUJ1, neuron‐specific class III b‐tubulin. A-GAfter iPSC‐based reprogramming of fibroblasts, we generated DAn from PD patients (n = 10) and gender‐ and age‐matched healthy controls (n = 4) using a 30‐day differentiation protocol. Blind to researcher, resulting iPSC‐derived DAn showed similar properties and maturation state in PD and controls. Specifically, studied iPSC‐derived DAn encompassed 30‐day ventromedial (vm)‐DAn‐enriched cultures of morphologically mature DAn showing typical bipolar morphology, lacking PD neural phenotypes, mostly of the A9 subtype, and showing properties of tyrosine hydroxylase (TH)+ mature neurons. Representative immunocytochemistry analyses of vmDAn from PD patients and controls showed that (F) co‐expressed the synaptic vesicle protein synaptophysin (SYP) which was located along neurites (Scale bar, 5 μm). A-GAfter iPSC‐based reprogramming of fibroblasts, we generated DAn from PD patients (n = 10) and gender‐ and age‐matched healthy controls (n = 4) using a 30‐day differentiation protocol. Blind to researcher, resulting iPSC‐derived DAn showed similar properties and maturation state in PD and controls. Specifically, studied iPSC‐derived DAn encompassed 30‐day ventromedial (vm)‐DAn‐enriched cultures of morphologically mature DAn showing typical bipolar morphology, lacking PD neural phenotypes, mostly of the A9 subtype, and showing properties of tyrosine hydroxylase (TH)+ mature neurons. (G) Calcium imaging assay revealed strong spontaneous neuronal activity. %ΔF/F indicates the relative change in fluorescence of the monitored neurons. Collectively, these results indicate that the iPSC‐derived DAn used our study were sufficiently mature for the studied parameters to be functional and to spontaneously form active neural networks in a similar and comparable manner for PD and controls.