Cerebral Organoid Culture

Cerebral Organoids are brain-like structures derived from human pluripotent stem cells (hPSCs—including ESCs or iPSCs) that are formed under three-dimensional culture conditions through processes of "self-organization" and "differentiation." This represents a sophisticated technique designed to mimic the developmental processes of the human brain.
The core steps involved in the culture of Cerebral Organoids are as follows^[1][2][3]:

1. Embryoid Body (EB) Formation

First, human pluripotent stem cells (hPSCs—including embryonic stem cells or induced pluripotent stem cells) are dissociated into single cells and aggregated within low-attachment culture plates to form three-dimensional cellular clusters known as embryoid bodies (EBs).

2. Neuroectoderm Induction

Once the embryoid bodies (EBs) have grown to a specific size, they are transferred into a neural induction medium devoid of specific differentiation factors. This step aims to suppress cellular differentiation toward other germ layers while specifically directing their development toward the neuroectoderm lineage.

3. Matrigel Embedding

The tissue aggregates, which have by this stage begun to exhibit neuroepithelial structures, are embedded within droplets of Matrigel. Matrigel serves to mimic the in vivo extracellular matrix environment, providing structural support to the neuroepithelium and facilitating the formation of polarized, ventricle-like structures.

4. Transfer and Culture

Following several days of rotational culture and maturation within the embedded matrix, the organoids are transferred to a spinner flask or an orbital shaker for long-term suspension culture. Continuous rotation enhances the exchange of oxygen and nutrients within the culture medium, preventing necrosis in the core of the organoids caused by hypoxia. This supports their long-term growth and maturation, ultimately leading to the formation of complex structures exhibiting characteristics of various brain regions (including cortical-like regions) and expressing marker proteins (such as PAX6, TBR1, and MAP2).

MCE has not independently verified the accuracy of these methods. They are provided for reference purposes only.

Key Reagents^[2][4]
• Matrigel
• Neural induction medium
• DMEM/F12, Neurobasal medium
• N-2 Supplement, B27 supplement (Vitamin A-free)
GlutaMAX, MEM-NEAA
• β-mercaptoethanol
• Growth Factors/Inhibitors: SB431542 (TGF-β inhibitor), Noggin (BMP inhibitor), EGF or FGF2 (Optional)

Additional Information^[2][4][5]

(1) Reagents for Regulating Neural Differentiation Signaling^[2][4][5]

Dual SMAD Inhibitors: A-83, SB-431542 (HY-10431), LDN193189 (HY-12071) (Core reagents for neural ectoderm induction)^[4]
WNT Pathway Activators: GSK3β inhibitor CHIR99021 (HY-10182)^[4]
Fibroblast Growth Factors: Recombinant bFGF (FGF2) Protein^[2]
Anti-apoptotic Reagent: ROCK Inhibitor Y-27632 (HY-10071) (Inhibits apoptosis of hiPSCs during single-cell seeding)^[5]

(2) 3D Culture and Histology Reagents^[4]

3D Scaffold Material: Matrigel (Used for organoid embedding; provides structural support and an environment conducive to polarity formation)
Cell Dissociation Reagents: Accutase, Dispase, 0.05% Trypsin/EDTA Solution, Trypsin Inhibitor
Fixation and Embedding Reagents: 4% Paraformaldehyde (PFA) (HY-DY3003), 30% Sucrose Solution, 7.5% Gelatin/10% Sucrose Embedding Medium, 4% Low-Melting-Point Agarose
Basic Buffers: Sterile PBS (with/without Ca²⁺/Mg²⁺), 0.5 mM EDTA Solution
Immunohistochemistry Reagents: 0.25% Triton-X Permeabilization Solution, 4% Normal Donkey Serum Blocking Solution, Fluorescent Secondary Antibodies (Donkey-derived AlexaFluor 488/568/647 Series)

(3) Summary of Functional Markers^[4]

Neural Stem/Progenitor Cell Markers: NESTIN, SOX2, PAX6, OTX2, FOXG1, HOPX, FAM107A, PTPRZ1, Ki67, PH3 (Phosphorylated Histone H3)
, P-Vimentin, TBR2
Neuronal Markers: TUJ1, MAP2, CTIP2, TBR1, SATB2, CUX1, BRN2, REELIN, DCX, TH, FOXA2, NURR1, PITX3, DAT, GABA, VGLUT1, PV, nNOS, SST, POMC, VIP, OXT, NPY, OTP
Glial Markers: GFAP, S100β
Nuclear Marker: DAPI

(4) Instruments and Equipment

Ultra-low attachment culture plates (low-attachment plates)
CO₂ Incubator
Centrifuge
Microscope (Inverted fluorescence microscope)
Suspension culture system (Spinner flask or orbital shaker)

Step 1: Embryoid Body (EB) Formation (Day 0-5)

Dissociate hPSCs (ESCs or iPSCs) at 70–80% confluence into single cells. Resuspend the cells in hES medium containing a low concentration of bFGF (1/5 of the standard concentration) and 50 μM of the ROCK inhibitor Y-27632; seed 4,500 cells per well into a 96-well ultra-low attachment U-bottom plate, and culture at 37°C with 5% CO₂. Perform a half-medium change every two days; after 6 days, mature EBs of uniform size will have formed.

Step 2: Neural Induction (Day 6-10)

Transfer 6-day-old EBs—approximately 500–600 μm in size with translucent edges—into a 24-well ultra-low attachment plate using a wide-bore 200 μL pipette tip (with the tip cut to widen the opening), placing one EB per well. Add neural induction medium (DMEM/F12 base supplemented with 1:100 N2 supplement, 1 μg/mL heparin, 1:100 GlutaMAX, and 1:100 MEM-NEAA).
After 48 hours of culture, add an additional 500 μL of fresh induction medium; subsequently, perform a complete medium exchange every two days. Continue the induction for 5 days to allow the EB ectoderm to differentiate into neuroectoderm, at which point translucent neuroepithelial regions will become visible on the surface of the EBs.

Step 3: Matrigel Embedding (Day 11-14)

Thaw the Matrigel overnight on ice at 4°C in advance. Prepare a sterile Parafilm plate containing small wells using a 200 μL pipette tip box.
Transfer the neural-induced EBs one by one, aspirate the excess culture medium, and embed each EB in a 30 μL droplet of Matrigel placed within a well of the Parafilm; incubate at 37°C for 20–30 minutes to allow the Matrigel to polymerize.

Step 4: Expansion Culture (Day 15+)

Transfer the aggregated droplets to a 60 mm culture dish and add 5 mL of Vitamin A-free differentiation medium (a 1:1 mixture of DMEM/F12 and Neurobasal, supplemented with 1:200 N2, 1:100 Vitamin A-free B27, 3.5 μL/L 2-mercaptoethanol, 1:4000 insulin, 1:100 GlutaMAX, and 1:200 MEM-NEAA).
Culture statically for 4 days, changing the medium every 2 days; during this period, the EBs will develop continuous neuroepithelial buds and ventricle-like cavities.

Step 5: Dynamic Culture (Day 20+)

Transfer the organoids—following the completion of static culture—using a wide-bore pipette tip:
① Option 1: Large Rotating Bioreactor—Add 75–100 mL of Vitamin A-containing differentiation medium (substituting the B27 supplement with the Vitamin A-containing version, and supplementing with the neurotrophic factors BDNF and GDNF), then culture under low-speed agitation.
② Option 2: Orbital Shaker—Place the organoids in a 60 mm culture dish and culture on an orbital shaker at 85 rpm.
Subsequently, perform a complete medium exchange with fresh Vitamin A-containing differentiation medium every 3–4 days; the organoids can be cultured long-term—for several months or even up to one year—to promote cortical stratification and cellular maturation.

Step 6: Detection and Analysis

Immunofluorescence staining (PAX6, SOX2, TBR1, MAP2)
qPCR analysis of gene expression
Single-cell sequencing (scRNA-seq)
Electrophysiological recording (at the maturation stage)

For detailed experimental procedures, please refer to the references below^[1][2][4][5].

1. Organoid Size Heterogeneity

Causes:
Inconsistent initial cell numbers
Lack of strict control during the EB formation stage
Solutions:
Strict quantification using single-cell counting
Standardize EB size using the AggreWell system

2. Low Neural Differentiation Efficiency

Causes:
Insufficient SMAD inhibition
Poor cell health/quality
Solutions:
Optimize SB431542/Noggin concentrations
Use high-quality hPSCs (with low background differentiation)

3. Organoid Core Necrosis

Causes:
Insufficient oxygen and nutrient diffusion
Solutions:
Use a spinner flask or orbital shaker
Reduce organoid size