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In Vivo vs. In Vitro Blood-Brain Barrier Models
The blood-brain barrier (BBB) serves as a dynamic interface of the neurovascular unit and constructs the molecular defense of the brain through a sophisticated network of endothelial cells, pericytes and astrocytes acting in concert. This complex system not only selectively regulates the bidirectional transport of nutrients and metabolic wastes, but also maintains the homeostasis of the intracerebral microenvironment through the spatial and temporal expression of active efflux transporters and tight junction proteins. Its functional integrity is directly related to neurodevelopment, disease progression and drug delivery efficiency, making it a key breakthrough in the treatment of Alzheimer's disease, stroke and brain tumors.
At Creative Biolabs, we focus on the innovation of multi-scale modeling of the BBB, integrating microfluidic organoids, iPSC-derived models and artificial intelligence prediction algorithms to systematically analyze the mechanism of cross-barrier transport. We provide novel solutions for targeted repair of neurodegenerative lesions, and promote the leapfrog development of brain science from basic research to clinical translation.
Basic Structure and Function of the BBB
BBB is an important protective structure of the central nervous system (CNS).
Basic Structure of BBB
Table 1. BBB Structure.
| Component | Description |
| Constituent Cells | BBB is composed of capillary endothelial cells, astrocytes, pericytes, and basement membrane. These cells form a barrier through tight junctions (TJs), restricting substance diffusion across the membrane. |
| Endothelial Cells | Core component of the BBB; non-porous cells that prevent diffusion of most substances via tight junctions and adhesion molecules. |
| Pericytes | Embedded between endothelial cells; regulate blood flow through vessels and enhance barrier integrity. |
| Astrocytes | Astrocyte end-feet cover the basement membrane and interact with endothelial cells to maintain barrier function. |
| Other Components | Include perivascular fluid space and neurons that collaborate to maintain BBB function. |
Figure 1. Diagram of BBB structure in relation to OA progression.1,2
Main Functions
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Protective Effect
BBB prevents harmful substances (e.g. bacteria, toxins) from entering the brain tissue, while protecting neurons from the external environment. -
Substance Transport Regulation
BBB allows specific molecules (e.g. oxygen, glucose, amino acids) to enter the brain tissue by passive diffusion or active transport, while blocking the passage of macromolecules and hydrophilic substances. -
Maintenance of Intracerebral Homeostasis
BBB ensures the stability of the intracerebral environment by regulating ion homeostasis, metabolic waste removal and nutrient supply. -
Immune Isolation
BBB restricts the entry of immune cells into the brain tissue, preventing the damage of inflammatory reaction to the nervous system.
Transport Mechanisms
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Passive Diffusion
Small molecules of lipid-soluble substances (e.g., oxygen, carbon dioxide) can diffuse directly through the lipid bilayer. -
Active Transport
Specific substances (e.g., glucose, amino acids) enter brain tissue via transporter proteins (e.g., glut1, glut3). -
Receptor-Mediated Transport
Certain substances enter brain tissue by receptor-mediated means.
Changes in Pathological States
BBB may become dysfunctional in a variety of diseases, such as tumors, ischemic stroke, and traumatic brain injury, leading to an increase in barrier permeability and the entry of harmful substances into brain tissue.
In summary, the BBB is a complex semipermeable membrane structure that achieves protection of brain tissue and precise control of substance transport through fine cellular composition and functional regulation.
In Vivo BBB model
Model Types
Rodent Model
Disease simulation by surgery (e.g., middle artery occlusion) or gene editing, combined with dynamic monitoring of blood-brain barrier leakage by MRI.
In Vivo Microscopy
Two-photon microscopy to observe the distribution of fluorescently labeled drugs in the brain parenchyma in real time.
Advantages and limitations
Strengths
Preservation of intact neuro-vascular-immune interactions, suitable for systemic pathology studies.
Limitations
Ethical controversy, species differences, low throughput.
In Vitro BBB Models
Table 2. Typical in vitro BBB models
| Model | Description | Advantages | Disadvantages |
| Single Cell Culture Model | Monolayer of cultured endothelial cells, usually co-cultured with astrocytes or pericytes. | Simple to operate, low cost, suitable for initial screening of drug permeability. | Lacks shear stress and dynamic environment; cannot fully mimic complex BBB structure and function. |
| Co-Culture Model | Multicellular culture to better mimic BBB interactions. | Better mimics multicellular interactions of BBB in vivo; improves physiological relevance. | Batch differences in cell sources may affect experimental consistency. |
| Transwell Model | Uses Transwell system to create bilayer of endothelial cells and astrocytes. | Direct measurement of TEER and permeability; widely used BBB model. | Cannot simulate shear stress or dynamic environment. |
| Microfluidic Chip Model (μBBB) | Simulates dynamic environment with microfluidics; thin cell interface; applies shear stress. | Closer to physiological BBB state; suitable for studying drug transport and neural activity. | Requires complex equipment and higher cost. |
| Triple Co-Culture Model | Combines endothelial cells, astrocytes, and neurons to form complex 3D structure. | Mimics complete BBB function including permeability and transporter protein expression. | Complex construction, high cost, and long experimental period. |
| Dynamic Microfluidic Model (DIV-BBB) | Uses microfluidic chip with hollow fiber to simulate vascular lumen and apply shear stress. | Combines static and dynamic model advantages; suitable for long-term research. | Larger wall thickness may affect cell-cell interactions. |
| Organ-on-a-Chip Model | Simulates organ microenvironment and BBB structure/function using microchip technology. | Highly simulates in vivo environment; suitable for complex disease model research. | High technical requirements and expensive. |
| Stem Cell-Based Models | Uses endothelial cells and neurons derived from induced pluripotent stem cells (iPSCs). | Reproduces molecular and functional properties of human BBB; suitable for personalized medicine. | Technically complex; requires strict quality control. |
BBB Model Selection
Table 3. Comparison of different models.
| Model type | Advantages | Limitations |
| In vivo model | Intact physiological environment, suitable for mechanism exploration | Ethical constraints, significant species differences |
| Transwell | High throughput | Low TEER, static conditional distortion |
| Microfluidic chip | Dynamic shear, TEER >300 Ω·cm² | Equipment cost >$10,000, high operational complexity |
| iPSC-derived models | Human genetic background, personalized drug testing | Cultivation cycle >30 days, risk of de-differentiation |
Why Creative Biolabs?
As a partner in neuroscience research, Creative Biolabs focuses on providing accurate and translatable BBB modeling solutions to accelerate CNS drug development relying on the following core services:
- Customized Blood-Brain Barrier Model Service
- Basic Neuroscience Research Tool Preparation Services
- Advanced Drug Discovery Service
Contact us today to break through BBB research bottlenecks with technological innovations that will empower the development of next-generation brain disease therapeutic strategies.
References
- Wu, Di, et al. "The Blood–Brain Barrier: Structure, Regulation and Drug Delivery." Signal Transduction and Targeted Therapy, vol. 8, no. 1, May 2023. https://doi.org/10.1038/s41392-023-01481-w.
- Distributed under Open Access license CC BY 4.0, without modification.
For Research Use Only. Not For Clinical Use.