Mitochondrial DNA and neurofilament release as Parkinson’s phenotypes in midbrain organoids

Introduction: Parkinson’s disease (PD) prevalence keeps growing worldwide, with growing numbers and considerable societal and economic concerns. This study aimed to evaluate the use of microglia-containing midbrain organoids as PD patient-specific systems for the detection of extracellular disease biomarkers. Materials and methods: We used the cell culture supernatant from healthy control and patient-specific organoids to measure Neurofilament light chain (NfL) levels via ELISA and to study mitochondrial DNA phenotypes through digital polymerase chain reaction (PCR). Organoid tissue was used for immunofluorescence staining and quantification of alpha-synuclein and glial fibrillary acidic protein (GFAP) levels. Results: Organoids generated from the PD patient line released higher levels of NfL and mitochondrial DNA into the medium. Furthermore, immunofluorescence staining of PD patient-specific organoids showed higher levels of phosphorylated alpha-synuclein as well as GFAP. Conclusions: Alterations in NfL levels and mitochondrial DNA homeostasis can be measured in the organoid supernatant and are particularly suitable as disease biomarkers and for high-throughput screening approaches.