World Parkinson’s Day: Deciphering Disease Mechanisms Through Cellular Models
Apr 13,2026
April 11, 2026 marks the 29th World Parkinson’s Day. Parkinson’s disease (PD) is the second most common neurodegenerative disorder worldwide, after Alzheimer’s disease. In recent years, research has shifted from symptom management toward elucidating underlying molecular mechanisms. Cell-based in vitro models of PD have emerged as a critical bridge between pathophysiological studies and clinical translation.
In this issue of Cell Culture Academy, we outline the neuropathological basis of PD and review key technologies and recent advances in in vitro model development.
I. Neuropathological Basis of Parkinson’s Disease
A central pathological hallmark of PD is the progressive loss of dopaminergic (mDA) neurons in the substantia nigra pars compacta (SNpc)[1]. These neurons project to the striatum (caudate nucleus and putamen) via the nigrostriatal pathway and regulate motor function through dopamine release. Core motor symptoms, including resting tremor, bradykinesia, and rigidity, typically appear only after 60-80% neuronal loss, when striatal dopamine is markedly depleted. This extended compensatory phase indicates that substantial neurodegeneration precedes clinical diagnosis.
Another key feature is the abnormal aggregation of α-synuclein (α-syn). Physiologically, α-syn functions in synaptic vesicle dynamics; pathologically, it misfolds into neurotoxic oligomers and fibrils that accumulate as Lewy bodies and Lewy neurites. These aggregates extend beyond the SNpc to the brainstem, olfactory bulb, and enteric nervous system, consistent with the broad spectrum of non-motor symptoms, including sleep disturbances, hyposmia, and constipation[2].
II. Cellular Sources for In Vitro Dopaminergic Neuron Models
A critical step in modeling PD in vitro is obtaining human dopaminergic neurons. Early studies relied on fetal tissue-derived neurons, but ethical constraints and limited availability have driven a shift toward cell lines and stem cell-derived models. Current approaches primarily use tumor-derived cell lines and dopaminergic neurons differentiated from human induced pluripotent stem cells (hiPSCs).
1. Tumor-derived Cell Lines
SH-SY5Y cells (human neuroblastoma) are widely used in PD research. They exhibit neuron-like properties and express dopaminergic markers, including tyrosine hydroxylase (TH) and the dopamine transporter (DAT), along with a catecholaminergic phenotype. To achieve a more mature neuronal state, SH-SY5Y cells require differentiation. Retinoic acid (RA) is commonly used to induce neuronal differentiation, followed by phorbol ester treatment to promote maturation and enhance neuronal features[3].
2. Induced Pluripotent Stem Cells
hiPSCs can be directed to differentiate into midbrain dopaminergic neurons, enabling patient-specific in vitro PD models. Key strategies include[4]:
Neural induction: Dual SMAD inhibition using Noggin and SB431542 suppresses BMP and TGF-β/Activin signaling, efficiently driving hiPSCs into neural progenitor cells.
Midbrain specification: Activation of Sonic Hedgehog and WNT/β-catenin signaling directs progenitors toward a dopaminergic lineage, with upregulation of LMX1A and FOXA2.
Maturation and survival: Late-stage supplementation with brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF), combined with ascorbic acid and cAMP analogs (e.g., forskolin, dbcAMP), enhances electrophysiological function and dopamine synthesis.
III. In Vitro PD Modeling Strategies and Validation
After generating high-quality dopaminergic neurons, PD-relevant phenotypes can be induced.
1. α-syn-Based Models
Gene overexpression: Viral vectors, including adeno-associated virus (AAV) and lentivirus, drive overexpression of wild-type or mutant (e.g., A53T) α-synuclein in neurons, promoting intracellular accumulation and toxicity. This approach is widely used to study early aggregation mechanisms[5].
Preformed fibril (PFF) induction: Exogenous α-syn preformed fibrils (PFFs) seed misfolding and aggregation of endogenous α-syn, generating phosphorylated and ubiquitinated inclusions. These aggregates can spread between cells, recapitulating Lewy body formation and pathological propagation[6].
2. Toxin-induced Models
MPP⁺, the active metabolite of MPTP, enters dopaminergic neurons via the DAT and inhibits mitochondrial complex I. This leads to ATP depletion and increased reactive oxygen species, causing acute or subacute neuronal injury and death. The model is straightforward, with rapid onset, and is well suited for studying mitochondrial dysfunction and oxidative stress[7].
Following model establishment, phenotypes are validated using complementary approaches:
Molecular and biochemical assays: Immunofluorescence to assess α-syn aggregation and neuronal markers (TH, MAP2); Western blotting for protein expression; and high-performance liquid chromatography (HPLC) to quantify dopamine and its metabolites.
Functional imaging: Calcium imaging enables real-time monitoring of neuronal network activity.
Electrophysiology: Patch-clamp recording measures action potentials and ion channel properties in single neurons, while multi-electrode arrays (MEA) provide long-term, noninvasive assessment of network connectivity and synchrony, enabling detection of early functional deficits.
IV. In Vitro Culture of PD Models
Conventional two-dimensional (2D) monolayer cultures are straightforward but lack the complexity of the native tissue environment, limiting their ability to recapitulate in vivo features. As a result, PD models are increasingly shifting toward multicellular 2D co-culture systems and three-dimensional (3D) platforms[8].
2D Co-culture Systems: Co-culture of neurons, astrocytes, and microglia is a promising approach for studying PD pathogenesis, as it captures interactions among neurons, glial cells, and the microenvironment.
3D Culture Technologies: Self-assembling peptide nanofiber scaffolds and brain organoids provide a more physiologically relevant three-dimensional structure, improving neural stem cell survival, differentiation efficiency, and functional maturation.
Robust and reproducible neural culture systems depend on key reagents:
Basal media: Neurobasal medium and Neurobasal-A medium provide essential nutrients for neuronal growth.
Supplements: B-27 and N-2 supply hormones, proteins, and antioxidants critical for neuronal survival.
Surface coatings: Poly-L-Lysine Solution mimics the extracellular matrix, promoting cell adhesion and neurite outgrowth.
Growth factors: BDNF, GDNF, and TGF-β3 support neuronal differentiation, maturation, and maintenance of functional phenotypes.
Parkinson’s disease research now spans a continuum from elucidating nigrostriatal degeneration to precisely inducing pathological changes in human dopaminergic neurons in vitro, forming an integrated framework from fundamental pathology to advanced models.
References
1. Lillian A, Zuo W, Laham L, Hilfiker S, Ye JH. Pathophysiology and Neuroimmune Interactions Underlying Parkinson's Disease and Traumatic Brain Injury. International Journal of Molecular Sciences. 2023 Apr 13; 24(8):7186.
2. Samizadeh MA, Fallah H, Toomarisahzabi M, Rezaei F, Rahimi-Danesh M, Akhondzadeh S, Vaseghi S. Parkinson's Disease: A Narrative Review on Potential Molecular Mechanisms of Sleep Disturbances, REM Behavior Disorder, and Melatonin. Brain Sciences. 2023 Jun 6;13 (6):914.
3. Ioghen OC, Ceafalan LC, Popescu BO. SH-SY5Y Cell Line In Vitro Models for Parkinson Disease Research-old Practice for New Trends. Journal of Integrative Neuroscience. 2023 Jan 16; 22 (1): 20.
4. Chen Y, Kuang J, Niu Y, et al. Multiple Factors to Assist Human-derived Induced Pluripotent Stem Cells to Efficiently Differentiate into Midbrain Dopaminergic Neurons. Neural Regeneration Research. 2024; 19 (4): 908-914.
5. Cenci MA, Björklund A. Animal Models for Preclinical Parkinson's research: An Update and Critical Appraisal. Progress in Brain Research. 2020; 252: 27-59.
6. Chmielarz P, Domanskyi A. Alpha-synuclein Preformed Fibrils: A Tool to Understand Parkinson's Disease and Develop Disease Modifying Therapy. Neural Regeneration Research. 2021; 16 (11): 2219-2221.
7. Pariyar R, Lamichhane R, Jung HJ, Kim SY, Seo J. Sulfuretin Attenuates MPP+-Induced Neurotoxicity through Akt/GSK3β and ERK Signaling Pathways. International Journal of Molecular Sciences. 2017 Dec 19; 18 (12): 2753.
8. Solana-Manrique C, Sánchez-Pérez AM, Paricio N, Muñoz-Descalzo S. Two- and Three-Dimensional In Vitro Models of Parkinson's and Alzheimer's Diseases: State-of-the-Art and Applications. International Journal of Molecular Sciences. 2025; 26 (2): 620.
