Development of a multi-sensor integrated midbrain organoid-on-a-chip platform for studying Parkinson’s disease

Abstract

Due to its ability to recapitulate key pathological processes in vitro, midbrain organoid technology has significantly advanced the modeling of Parkinson's disease over the last few years. However, some limitations such as insufficient tissue differentiation and maturation, deficient nutrient supply, and low analytical accessibility persist, altogether restricting the technology from reaching its full potential. To overcome these drawbacks, we have developed a multi-sensor integrated organ-on-a-chip platform capable of monitoring the electrophysiological, respiratory, and dopaminergic activity of human midbrain organoids. Our study showed that microfluidic cultivation resulted in a marked reduction in necrotic core formation, improved tissue differentiation as well as the recapitulation of key pathological hallmarks. Non-invasive monitoring employing an orthogonal sensing strategy revealed a clear time dependency in the onset of Parkinson's disease-related phenotypes, reflecting the complex progression of the neurodegenerative disorder. Furthermore, drug-mediated rescue effects were observed after treatment with the repurposed compound 2-hydroxypropyl β-cyclodextrin, highlighting the platform's potential in the context of drug screening applications as well as personalized medicine.

Sensor‐integrated brain‐on‐a‐chip platforms: Improving the predictive validity in neurodegenerative research

“…In comparison to conventional in vitro models, OoC technology thus offers three key advantages: (i) spatial and temporal control over cells and biochemical cues, (ii) biophysical stimulation as well as (iii) analytical accessibility 25–28 . For these reasons, OoC technology has already led to the successful development of various tissue analogs in vitro, including, among others, models of the human blood–brain barrier (BBB) as well as the central nervous system applicable to the study of key pathological mechanisms and the identification of new drug targets 27,29–31 …”

“…Key pathological phenotypes such as reduced populations of dopaminergic neurons, impaired glial differentiation, aggregated α‐synuclein (α‐syn), and compromised mitochondrial phenotypes were observed upon comparing patient‐specific organoids carrying a triplication mutation of the α‐syn gene with control organoids at 60 days of differentiation (Figure 1c). Furthermore, rescue effects in mitochondrial and neurodegenerative phenotypes were observed after the treatment of patient‐specific organoids with the repurposed compound 2‐hydroxypropyl‐β‐cyclodextrin 31 . Pediaditakis et al, on the other hand, employed a membrane‐based platform to investigate the role of the BBB in PD by co‐culturing human dopaminergic neurons, astrocytes, pericytes, microglia, and microvascular endothelial cells under dynamic conditions.…”

“…Zirath et al have previously shown that lifetime‐based optical oxygen sensors can easily be integrated into microfluidic platforms and can provide valuable information on the formation of oxygen gradients, cellular viabilities as well as cell‐specific respiration profiles 58,64 . Furthermore, the sensor was successfully integrated into a midbrain‐on‐a‐chip platform for long‐term studies, revealing significant differences in the oxygen demand between control and PD‐specific midbrain organoids, as well as upon treatment with a repurposed compound 31 . Furthermore, several commercially available oxygen sensors have been reported (Table S4).…”

“…Due to their application in complex biological matrices, the sensors may be applicable to monitor dopamine in OoC platforms 156,157 . To illustrate, Spitz et al recently successfully employed a sensor functionalization protocol published by Njagi et al 157 to modify screen‐printed carbon electrodes and utilize them as insert‐based sensors for dopamine measurements in a midbrain organoid‐on‐a‐chip platform 31 . Commercial dopamine sensors may be a viable alternative to overcome the challenges associated with complex electrode fabrication in dopamine sensing.…”

“…[25][26][27][28] For these reasons, OoC technology has already led to the successful development of various tissue analogs in vitro, including, among others, models of the human blood-brain barrier (BBB) as well as the central nervous system applicable to the study of key pathological mechanisms and the identification of new drug targets. 27,[29][30][31] 1.2 | Recent advances in organ-on-a-chip models for neurodegenerative disease research Most microfluidic studies on NDDs to date have been dedicated to unraveling the mechanisms behind the uptake, transport, and transmission of aberrant proteins by utilizing the beneficial combination of cellular compartmentalization and optical accessibility obtained within microfluidic setups. While these predominately 2D studies have provided valuable insights into key mechanisms underlying NDD onset and progression, most of the studies (around 80%) have employed over-simplified models with non-human cell sources (70%).…”