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signaling activity compared to healthy midbrain organoids. and commonly used cell lines, such as SH-SY5Y cells,
Dysregulated insulin signaling in GBA-PD exacerbates have also been developed. In these 3D-cultured cells,
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DA neuron loss through FOXO1 overexpression, while phosphorylated α-synuclein and a detergent-insoluble
elevated insulin levels disrupt lipid metabolism and trigger α-synuclein fraction were observed following 1-methyl-
cellular death. These findings emphasize the potential 4-phenylpyridinium and rotenone treatment. This study
of targeting insulin signaling to combat PD-related presents a cost-efficient and accessible 3D PD model that
neurodegeneration. Frattini et al. generated another effectively recapitulates key α-synuclein pathologies,
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hMOs model from GBA1-L444P-associated PD patients’ providing a valuable platform for PD-related research and
iPSCs. These hMOs display a reduced GCase activity, therapeutic applications. Alternatively, it has also been
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recapitulating DA neuron loss and fundamental features of reported that organoids derived from peripheral blood
Lewy body pathology observed in human brains, including mononuclear cells (PBMCs) of patients with the idiopathic
the generation of α-synuclein fibrillary aggregates. Notably, form of PD have been developed (Table 1). This approach
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ambroxol and GZ667161, two GCase modulators in clinical offers a less invasive method for obtaining patient-specific
development, effectively reduced α-synuclein pathology, cells, facilitating the study of PD pathology and the
highlighting midbrain organoids as a valuable platform for development of personalized therapeutic strategies.
preclinical drug screening. 54,55 Recent studies using hMOs
derived from genetically modified human embryonic 3. Organoid models in drug screening
stem cells have provided significant insights into the for PD
synergistic effects of GBA1 loss and SNCA overexpression
on α-synuclein aggregation. Specifically, the concurrent The challenges in drug screening for PD are multifaceted,
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loss of GBA1 function and overexpression of wild-type stemming from the disease’s complexity, limitations of
α-synuclein leads to the substantial accumulation of current models, and difficulties in translating preclinical
detergent-resistant, β-sheet-rich α-synuclein aggregates findings into clinical outcomes. Traditional 2D cell cultures
and the formation of Lewy body-like inclusions within and animal models often fail to replicate the intricate
these organoids. Notably, these pathological features pathophysiology of PD due to limitations in capturing key
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do not emerge when either genetic alteration occurs aspects such as α-synuclein aggregation, neuroinflammation,
independently. In addition, impaired GCase function has mitochondrial dysfunction, and progressive neuronal
been shown to promote α-synuclein aggregation in hMOs loss. While 2D cultures of DA neurons provide valuable
derived from PD patients carrying SNCA triplication insights, they lack cellular diversity, extracellular matrix
mutations. 56 interactions, and long-term maturation, limiting their
ability to model chronic neurodegeneration. 62,63 Similarly,
Along this line, beyond α-synuclein accumulation, animal models, including MPTP-treated mice, rotenone-
GBA1 loss in human iPSC-derived neurons indeed disrupts exposed rats, and α-synuclein transgenic models, only
lysosomal protein degradation, leading to neurotoxicity partially mimic human PD pathology, as differences in
through aggregation-dependent mechanisms. α-synuclein species affect dopamine metabolism, immune response,
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itself inhibits the lysosomal trafficking of GCase, creating and protein aggregation dynamics. Moreover, these models
a bidirectional feedback loop that perpetuates disease often fail to recapitulate the prion-like spread of misfolded
progression. This self-reinforcing cycle suggests that α-synuclein and the full spectrum of motor and non-motor
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targeting both α-synuclein accumulation and lysosomal symptoms seen in PD patients. 64-67
dysfunction may be necessary for effective PD therapies.
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Additionally, the interaction between GBA and LRRK2 has To overcome these challenges, emerging alternatives
been well established. DA neurons carrying LRRK2 R1441C, such as 3D midbrain organoids, microfluidic organ-
R1441G, or G2019S mutations exhibit reduced GCase on-a-chip systems, and humanized animal models are
activity, which can be restored by LRRK2 kinase inhibition, being developed. iPSC-derived midbrain organoids, for
accompanied by decreased α-synuclein phosphorylation. 58,59 instance, recreate nigrostriatal connectivity, glial-neuronal
These findings strongly suggest that the interplay between GBA interactions, and progressive α-synuclein pathology,
and other PD-related proteins may have synergistic effects offering a more physiologically relevant platform for disease
on neuronal toxicity, further driving disease progression. modeling and drug discovery. A group of researchers
Understanding these interactions provides critical insights developed a novel organoid model based on optogenetic
into PD pathogenesis and highlights the potential of targeting proteins, termed the optogenetics-assisted α-synuclein
multiple pathways for therapeutic intervention. aggregation induction system (OASIS). This system
enables rapid induction of α-synuclein aggregates and
2.7. Other organoid models associated toxicity in PD-associated hMOs. By utilizing
In addition to hMOs incorporating PD-related genetic optogenetic proteins, OASIS allows precise light-induced
factors, other 3D culture models utilizing Matrigel spatiotemporal control of protein interactions, effectively

Volume 1 Issue 2 (2025) 6 doi: 10.36922/OR025040006