A human striatal-midbrain assembloid model of alpha-synuclein propagation.

Midbrain dopaminergic (mDA) neurons are essential for motor control, reward processing, emotional regulation and motivation. The degeneration of these neurons, seen in Parkinson’s disease (PD), disrupts fine motor control, leading to symptoms such as bradykinesia, rigidity, and tremor. To date, there is no cure for Parkinson’s Disease (PD), and the mechanisms underlying dopaminergic neuron degeneration remain elusive. Current cell therapies focus on replenishing the degenerated dopaminergic neurons, by transplantation of dopaminergic neurons derived from human pluripotent stem cells (PSCs). Nevertheless, these therapies face post-transplantation challenges such as low cell survival, consistent dopamine release, and co-development of an undesired cell population such as serotonergic neurons leading to hyperkinesia. Midbrain organoids generated from PD hiPSCs offer a promising platform to investigate PD pathomechanisms and discover novel therapeutic approaches. This study aimed to establish a PD model in a novel midbrain organoid and employ optogenetics to control mDA neuron activity and thus dopamine release. We developed a robust mBENO protocol featuring bona fide midbrain dopaminergic neurons within a functional neuronal-glial network resembling the human midbrain/basal ganglia. The composition of mBENO was characterized by temporal transcriptomic analysis and morphological analyses after immunofluorescence labelling, while its function was assessed through local field potential recordings and dopamine content measurements. Neurotransmitter administration confirmed the presence of a functional neuronal network harboring dopaminergic, GABAergic, cholinergic and glutamatergic neurons. Next, we genome engineered and established a PD mBENO model by introducing a SNP found in PD patients, the α-synuclein (SNCA) A30P mutation. SNCA A30P did not impair the differentiation potential but led to dopaminergic neuron loss by D90 and electrophysiological hyperexcitability resembling basal ganglia dysfunction in PD patients. This SNCA A30P mBENO model provides a valuable system to investigate PD pathomechanisms, disease progression, as well as potential therapeutic targets. mBENO could potentially serve as a cell source for cell replacement therapies, offering better cell survival and retention in patients compared to singularized cell injections. Furthermore, to control dopamine secretion we engineered an optogenetic cell line, SynfChrimson, which expresses a stably integrated, fast, red light activatable channel (f-Chrimson), under the control of a synapsin promotor in the AAVS1 locus. Multielectrode array analysis confirmed that the SynfChrimson cell line exhibits neuron specific light-evoked activation. Implanting optogenetically controlled mDA neurons along with a medical device could potentially overcome the challenges of fine-tuning dopamine release in PD therapy. In conclusion, we present a novel midbrain organoid model, which recapitulates the human midbrain in cellular composition and function. We demonstrate that the A30P mBENO exhibits mDA neuron loss and hyperexcitability, functionally modeling PD. The A30P mBENO holds promise as a tool to investigate pathomechanisms and pharmaceutical targets in the future.

P18-46 Label-free Functional Analysis for the Screening of iPSC-derived Neural Organoid Response to Neuroactive Compounds

DNAJB6 suppresses alpha-synuclein induced pathology in an animal model of Parkinson's disease

Advanced human iPSC-based preclinical model for Parkinson's disease with optogenetic alpha-synuclein aggregation.

Parkinson’s disease (PD) is the second-most common neurodegenerative disease in the world, affecting up to 10 million people. This disease mainly happens due to the loss of dopaminergic neurons accountable for memory and motor function. Partial glucocerebrosidase enzyme deficiency and the resultant excess accumulation of glycosphingolipids and alpha-synuclein (α-syn) aggregation have been linked to predominant risk factors that lead to neurodegeneration and memory and motor defects in PD, with known and unknown causes. An increasing body of evidence uncovers the role of several other lipids and their association with α-syn aggregation, which activates the innate and adaptive immune system and sparks brain inflammation in PD. Here, we review the emerging role of a number of lipids, i.e., triglyceride (TG), diglycerides (DG), glycerophosphoethanolamines (GPE), polyunsaturated fatty acids (PUFA), sphingolipids, gangliosides, glycerophospholipids (GPL), and cholesterols, and their connection with α-syn aggregation as well as the induction of innate and adaptive immune reactions that trigger neuroinflammation in PD.

An increasing body of evidence suggests that mitochondrial dysfunction mediated by α-synuclein (α-syn) aggregates plays a key role in the pathogenesis of Parkinson's disease (PD), leading to intensive research for the discovery and development of compounds with mitoprotective effects. Silymarin (SIL) is a complex mixture of flavonolignans with a wide range of protective effects on mitochondria under stress conditions. Herein, the potency of SIL, in bulk and nano forms, in protecting mitochondria against oxidative damage induced by α-syn aggregates has been investigated. Mitochondria were isolated from rat brain and liver tissues as well as human neuroblastoma SH-SY5Y cells, and damage was evaluated by using a range of biochemical assays. The obtained results show a substantial difference in the response of various mitochondria to oxidative damage induced by α-syn aggregates, with brain mitochondria exhibiting the highest vulnerability. We found that incubation of mitochondria with either bulk or nano forms of SIL before exposure to α-syn aggregates significantly attenuated oxidative damage in a dose-dependent manner. In parallel, α-syn aggregates aged in the presence of bulk or nano forms of SIL considerably lost their capacity to cause mitochondrial damage. While both bulk and nano forms of SIL showed significant mitoprotective effects, SIL nanosheets were much more effective. Possible mechanisms relating to the mitoprotective effects of SIL and the higher efficacy of SIL nanosheets are discussed. The obtained results suggest natural polyphenol-based nanoparticles as an efficient therapeutic approach in relation to amyloid-related diseases, such as PD.

Human midbrain organoids (hMOs) show promise as a patient-derived model for the study of Parkinson's disease (PD). Yet, much remains unknown about how accurately hMOs recapitulate key features of PD in the human brain. In both PD patients and animal models, disease progression leads to characteristic changes in neural activity throughout the basal ganglia. Here we demonstrate that patient-derived induced pluripotent stem cell (iPSC) hMOs harboring a triplication in the SNCA gene, encoding α-synuclein, a key protein in PD pathogenesis, can recapitulate PD-associated changes in neural activity. Namely, we observe hyperactive network activity in SNCA triplication hMOs, but not in isogenic, CRISPR-corrected iPSC hMOs. These changes are characterized by an increase in the number of bursts and network-wide bursts. Moreover, SNCA triplication hMOs exhibit an increase in network synchrony and burst/network burst strength similar to observations in animal and human PD brains. Subsequently, we show that the observed changes in neuronal activity are attributed to dopamine D2 receptor hypoactivity due to dopamine depletion, which could be reversed by the D2 receptor agonist quinpirole. Thus, hMOs faithfully model network wide electrophysiological changes associated with PD progression and serve as a promising tool for PD research and personalized medicine.

Striatal Plasticity and Basal Ganglia Circuit Function

Diffusion kurtosis imaging (DKI) by measuring non-Gaussian diffusion allows an accurate estimation of the distribution of water molecule displacement and may correctly characterize microstructural brain changes caused by neurodegeneration. The aim of this study was to evaluate the ability of DKI to detect changes induced by α-synuclein (α-syn) accumulation in α-syn over-expressing transgenic mice (TNWT-61) in both gray matter (GM) and white matter (WM) using region of interest (ROI) and tract-based spatial statistics analyses, respectively, and to explore the relationship between α-syn accumulation and DKI metrics in our regions of interest. Fourteen-month-old TNWT-61 mice and wild-type (WT) littermates underwent invivo DKI scanning using the Bruker Avance 9.4 Tesla magnetic resonance imaging system. ROI analysis in the GM regions substantia nigra, striatum, hippocampus, sensorimotor cortex, and thalamus and tract-based spatial statistics analysis in WM were performed. Immunohistochemistry for α-syn was performed in TNWT-61 mice and correlated with DKI findings. We found increased kurtosis and decreased diffusivity values in GM regions such as the thalamus and sensorimotor cortex, and in WM regions such as the external and internal capsule, mamillothalamic tract, anterior commissure, cingulum, and corpus callosum in TNWT-61 mice as compared to WT mice. Furthermore, we report for the first time that α-syn accumulation is positively correlated with kurtosis and negatively correlated with diffusivity in the thalamus. The study provides evidence of an association between the amount of α-syn and the magnitude of DKI metric changes in the ROIs, with the potential of improving the clinical diagnosis of Parkinson's disease. We propose diffusion kurtosis imaging as a sensitive method for detecting human α-synuclein accumulation-induced changes in brain tissue, which may be reflective of Parkinson disease stage. Boxplots show the averaged mean kurtosis (orange) and mean diffusivity (blue) under the results of the analysis (*p<0.05) in brains of wild-type (WT) and α-synuclein over-expressing (TNWT-61) mice. This approach might represent a novel biomarker for the early diagnosis of Parkinson's disease. Read the Editorial Highlight for this article on page 1117.

Alpha-Synuclein (α-Syn) aggregation is a pathological feature of synucleinopathies, neurodegenerative disorders that include Parkinson's disease (PD). Here, we explored the efficacy of N,N,N′,N′-tetraethyl-10H-phenothiazine-3,7-diamine dihydrochloride (LETC), a protein aggregation inhibitor, on α-Syn aggregation. In both cellular models and transgenic mice, α-Syn aggregation was achieved by the overexpression of full-length human α-Syn fused with a signal sequence peptide. α-Syn accumulated in transfected DH60.21 neuroblastoma cells and α-Syn aggregation was inhibited by LETC with an EC50 of 0.066 ± 0.047 μM. Full-length human α-Syn overexpressing Line 62 (L62) mice accumulated neuronal α-Syn that was associated with a decreased motor performance in the open field and automated home cage. LETC, administered orally for 6 weeks at 10 mg/kg significantly decreased α-Syn-positive neurons in multiple brain regions and this resulted in a rescue of movement deficits in the open field in these mice. LETC however, did not improve activity deficits of L62 mice in the home cage environment. The results suggest that LETC may provide a potential disease modification therapy in synucleinopathies through the inhibition of α-Syn aggregation.

Misfolded alpha-synuclein (αSyn) aggregates are a hallmark event in Parkinson's disease (PD) and other synucleinopathies. Recently, αSyn seed amplification assays (αSyn-SAAs) have shown promise as a test for biochemical diagnosis of synucleinopathies. αSyn-SAAs use the intrinsic self-replicative nature of misfolded αSyn aggregates (seeds) to multiply them in vitro. In these assays, αSyn seeds circulating in biological fluids are amplified by a cyclical process that includes aggregate fragmentation into smaller self-propagating seeds, followed by elongation at the expense of recombinant αSyn (rec-αSyn). Amplification of the seeds allows detection by fluorescent dyes specific for amyloids, such as thioflavin T. Several αSyn-SAA reports have been published in the past under the names 'protein misfolding cyclic amplification' (αSyn-PMCA) and 'real-time quaking-induced conversion'. Here, we describe a protocol for αSyn-SAA, originally reported as αSyn-PMCA, which allows detection of αSyn aggregates in cerebrospinal fluid samples from patients affected by PD, dementia with Lewy bodies or multiple-system atrophy (MSA). Moreover, this αSyn-SAA can differentiate αSyn aggregates from patients with PD versus those from patients with MSA, even in retrospective samples from patients with pure autonomic failure who later developed PD or MSA. We also describe modifications to the original protocol introduced to develop an optimized version of the assay. The optimized version shortens the assay length, decreases the amount of rec-αSyn required and reduces the number of inconclusive results. The protocol has a hands-on time of ~2 h per 96-well plate and can be performed by personnel trained to perform basic experiments with specimens of human origin.

Parkinson disease (PD) is a highly prevalent and incurable neurodegenerative disease associated with the accumulation of misfolded α-synuclein (αSyn) aggregates. An important problem in this disease is the lack of a sensitive, specific, and noninvasive biochemical diagnosis to help in clinical evaluation, monitoring of disease progression, and early differential diagnosis from related neurodegenerative diseases. To develop a novel assay with high sensitivity and specificity to detect small quantities of αSyn aggregates circulating in cerebrospinal fluid (CSF) of patients affected by PD and related synucleinopathies. The strategy evaluated in this proof-of-concept study uses the protein misfolding cyclic amplification (PMCA) technology that detects minute amounts of misfolded oligomers by taking advantage of their ability to nucleate further aggregation, enabling a very high amplification of the signal. The technology was first adapted with synthetic αSyn oligomers prepared in vitro and used to screen in 2 blinded cohorts of CSF samples from German and Japanese patients with PD (n = 76) and individuals serving as controls affected by other neurologic disorders (n = 65), neurodegenerative diseases (n = 18), and Alzheimer disease (n = 14). The kinetics of αSyn aggregation were measured by αSyn-PMCA in the presence of CSF samples from the participants to detect αSyn oligomeric seeds present in this biological fluid. The assays were conducted from November 15, 2013, to August 28, 2015. Kinetic parameters correlated with disease severity at the time of sample collection, measured by the Hoehn and Yahr scale, with the lowest grade indicating unilateral involvement with minimal or no functional impairment, and the highest grade defining patients with complete confinement to wheelchair or bed. Studies with synthetic αSyn aggregates showed that αSyn-PMCA enabled to detect as little as 0.1 pg/mL of αSyn oligomers. The αSyn-PMCA signal was directly proportional to the amount of αSyn oligomers added to the reaction. A blinded study of CSF samples correctly identified patients affected by PD with an overall sensitivity of 88.5% (95% CI, 79.2%-94.6%) and specificity of 96.9% (95% CI, 89.3%-99.6%). The αSyn-PMCA results for different patients correlated with the severity of the clinical symptoms of PD (Japanese cohort: rs = -0.54, P = .006; German cohort: rs = -0.36, P = .02). The findings suggest that detection of αSyn oligomers by αSyn-PMCA in the CSF of patients affected by PD may offer a good opportunity for a sensitive and specific biochemical diagnosis of the disease. Further studies are needed to investigate the usefulness of αSyn-PMCA to monitor disease progression and for preclinical identification of patients who may develop PD.

Parkinson's disease (PD) presents with both motor and non-motor symptoms, including depression and anxiety, which often precede motor onset, yet the mechanisms linking these affective symptoms to PD pathology remain unclear. In this study, we investigated the bidirectional relationship between depression/anxiety behaviors and α-synuclein (α-syn) propagation using A53T α-syn transgenic mice subjected to chronic restraint stress (CRS) and/or intrastriatal injection of α-syn preformed fibrils (PFFs). Behavioral testing and immunohistochemical analyses revealed that CRS enhanced PFF-induced α-syn propagation and exacerbated depression/anxiety-like behaviors, while α-syn propagation was associated with aggravated CRS-induced behavioral deficits, indicating a potential reciprocal association that could contribute to accelerating PD progression. This interaction was mediated by the neuronal activity marker c-Fos. Pharmacological inhibition of c-Fos with T5224 mitigated both behavioral and pathological changes, and mGluR5 activation was found to partially contribute to c-Fos induction and α-syn spread. Together, these findings highlight a feedback interaction between affective symptoms and α-syn pathology in PD, mediated in part by neuronal activity-dependent mechanisms involving c-Fos and mGluR5, and suggest that early interventions targeting both neuronal activity and α-syn propagation may slow PD progression and improve patient quality of life.

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. Pathologically, it is characterized by the aberrant aggregation of α-synuclein (α-syn) in neurons. Clinical evidence shows that patients with hypercholesterolemia are more likely to get PD, while lovastatin users have a lower risk of suffering from it. In this study, we investigated the effects of lovastatin on the aggregation and phosphorylation of α-syn in vitro. Our results demonstrate that α-syn preformed fibrils induce the phosphorylation and aggregation of α-syn in HEK293 cells stably transfected with α-syn-GFP and SH-SY5Y cells as well, which could be attenuated by in a concentration-dependent manner. Besides, lovastatin inhibited oxidative stress, histone acetylation, and the activation of casein kinase 2 (CK2). Collectively, lovastatin alleviates α-syn aggregation and phosphorylation in cellular models of synucleinopathy, indicating its potential value of being adopted in the management of PD.

Recent investigations underscore the pivotal role of reactive astrocytes in the pathogenesis of Parkinson’s disease (PD). As PD advances, reactive astrocytes lose their ability to degrade α-Synuclein (α-Syn) aggregates while concurrently increasing r-aminobutyric acid (GABA) secretion, which heightens inhibition of DA neurons and worsens the disease. This study explored optogenetic manipulation of reactive astrocytes as a therapeutic strategy. Halorhodopsin (NpHR), a chloride pump, was expressed in reactive astrocytes within the substantia nigra pars compacta (SNpc) of an A53T α-Syn overexpression PD rat model. Optogenetic stimulation of NpHR led to a 72.6% reduction in GABA level (p = 0.0486) and a 67.5% decrease in α-Syn aggregates (p < 0.0001) within the SNpc. Furthermore, contralateral forelimb akinesia was significantly improved by 81.4 ± 7.2% (71.6–90.9%) post-illumination in the NpHR group compared with the pre-illumination state (p = 0.0002). These results suggest that the optogenetic modulation of reactive astrocytes can alleviate astrocytic aberrant tonic inhibition of DA neurons, resulting in the revitalization of DA neurons and enhancing the degradation of α-Syn aggregates. This mechanism may ultimately ameliorate parkinsonian motor symptoms, suggesting a promising novel therapeutic avenue for PD.