In Parkinson’s disease dopaminergic neurons are irrecoverably lost from the midbrain resulting in slowed movement, tremors and other symptoms. Dopamine augmentation is the main treatment for Parkinson’s, however, there is no cure available that can reverse the symptoms, partly due to the lack of adequate experimental systems to test new drugs and therapies. Midbrain organoids hold great potential for studying the dopaminergic system.
Jens Christian Schwamborn of University of Luxembourg, and colleagues, attempted to address the limitations of midbrain organoid generation; namely, absence of vascularization leading to dead core, heterogeneity in size and cellular composition, and non-optimised analysis techniques. The results were published in the journal Stem Cell Research.
The starting materials for organoid generation were three independent induced pluripotent stem cell lines (iPSCs); K7 fibroblasts from a woman of 81 years, T12 from a 53 year old lady and COR from a man of 55 years. The cell lines were differentiated into floor plate neuronal progenitor cells (mfNPC) and three different methods for generating organoids were then applied.
Dopaminergic neuron generation in the organoids was confirmed using an antibody against the tyrosine hydroxylase (TH) neuronal marker. Dopamine transporter (DAT) and dopamine (DOPA) itself were also detected. Treatment of mature organoids with the neurotoxin 6-OHDa reduced the number of dopaminergic neurons as expected.
The scientists were able to generate organoids without dead cores using two out of the three organoid generation protocols. One method was less variable than the others. The condition with the least dead cores also produced the most neurons relative to the total number of nuclei.
Increased reproducibility and reduced generation times are major pluses of the neuronal organoid generation process developed by the team. The new system holds promise as a tool for neurotoxicity screening, however, the researchers did not develop the complete set of protocols using the organoids that would be needed to replace current animal testing.
“By modulating the organoid maturation process, we have generated a novel optimized and standardized human midbrain-like organoid model that exhibits many features reminiscent of the human midbrain dopaminergic system. The optimized generation strategy led to a spatially organized organoid model, including different cell types of neuroectodermal origin,” concluded the authors.