What are Endothelial Cells?
Endothelial cells form a thin layer that lines the inside of all blood and lymphatic vessels and the heart. This layer is called the endothelium. It helps control blood flow, blood pressure, how easily fluids move in and out of vessels and how immune cells move from blood into tissues. When the endothelium does not function appropriately, it is linked to diseases such as atherosclerosis, stroke, heart failure, diabetic complications and even cancer. [1]
Further, because the endothelium sits between the blood and body tissues, it is directly exposed to and regulates drug transport, hormones, inflammatory signals and changes in metabolism. For this reason, endothelial cells are a common focus in basic research and in studies of new therapies. [2, 3]
How Endothelial Cells are Used in Research
Endothelial cells are used in a wide range of applications, including:
- Studying how new blood vessels form and change over time (angiogenesis). [7]
- Understanding inflammation, including how white blood cells stick to vessel walls and migrate into tissues.
- Studying how drugs interact with and pass through the endothelium.
- Modeling atherosclerosis and blood clot formation. [8]
- Investigating how tumors grow blood vessels and how drugs reach solid tumors.
- Building engineered tissues and organ-on-chip systems that include small blood vessels. [9, 10]
Due to this vast application potential, different research questions may need different types of endothelial cell models. Some projects may call for simple and robust systems, while others need models that are closer to specific tissues or to patient-specific biology.
Common Endothelial Cell Models
While there is no single “best” endothelial cell model for every study, researchers typically choose between several types, each with its pros and cons, to maximize effectiveness based on the application’s needs.
Overview of Main Models
| Model Type | Typical Use | Main Advantages | Main Limitations |
|---|---|---|---|
| HUVECs (umbilical cord-derived) | General vascular studies, angiogenesis and inflammation. | Well-known, widely available, easy to grow and cited in many published methods. | Derived from cord tissue and may not reflect specific adult tissues, donor-to-donor variability and limited number of passages. |
| Primary tissue-derived endothelial cells | Organ- or tissue-specific questions (e.g., heart, lung, brain). | Mimics cells found in that tissue in the body. | Limited availability, low expansion, batch variability. |
| Endothelial-like cancer lines and tumor co-cultures | Tumor blood vessel growth and tumor–vessel interactions. | Good for studying the tumor environment, stable and easy to expand. | Reflects a specific diseased state and transformed lines harbor altered transcriptional signatures. |
| 2D vs 3D models | 2D for simple assays; 3D for more complex structures. | 2D: simple and high-throughput. 3D: closer to real vessel shapes and gradients. | 2D: less physiologically relevant. 3D: more complex and harder to analyze. |
HUVECs are one of the most commonly used endothelial models and are often used for tube-formation assays and basic studies of vessel growth and inflammation. However, since they come from the umbilical cords of newborns, they may not behave like adult endothelial cells from specific tissues. That said, primary endothelial cells from organs such as the heart or brain can be more tissue-specific; however, they become significantly harder to source and expand in large numbers. [11]
Further, tumor co-culture systems are typically utilized to help researchers understand how cancer cells affect nearby vessels and how drugs reach tumors. These models can be especially useful for studying cancer environments; however, they are not ideal when the focus is on healthy vascular biology. [12]
These factors and constraints have led many researchers to seek models that are human, scalable and better suited to patient-specific studies, and iPSC-derived endothelial cells are one approach to addressing these challenges.
iPSC-Derived Endothelial Cells
Induced pluripotent stem cells (iPSCs) are made by reprogramming adult cells, such as skin or blood cells, back into a stem cell-like state. These newly generated stem cells can then be guided to differentiate into theoretically any cell type, including endothelial cells. The resulting cells are referred to as iPSC-derived endothelial cells and provide a scalable, human-derived model for vascular research. [6]
Benefits of iPSC-Derived Endothelial Cells
- Large, renewable supply – Once an iPSC line is created, it can be expanded and banked for long periods of time. This allows for the production of billions of endothelial cells from the same starting source line, reducing experimental variability and improving overall consistency. [5]
- Patient-based models – One of the key benefits of iPSCs is that they can be generated from individual patients, including those with specific vascular diseases. Endothelial cells from these lines retain the patient’s genetic background, allowing researchers to study how specific drug applications and gene changes affect endothelial cell function, and allow a personalized approach to drug development. [4]
- More consistent experiments – Because the same iPSC source line can be used repeatedly, iPSC-derived endothelial cells remove the variability associated with using primary cells from multiple donors. Studies have shown that iPSC-derived endothelial cells perform comparably to primary endothelial cells in tube formation and vessel-forming assays while offering a consistent and reproducible source. [13]
- Use in advanced systems – iPSC-derived endothelial cells can be used within microfluidic chips, 3D gels, spheroids, organoids and bioprinted tissues. For example, differentiated iPSCs have been used to form blood vessel networks in engineered tissues and have even been used to improve blood flow and survival rates after transplantation in animal models. [9, 5]
- Easy to combine with gene editing and measurements – iPSC-based systems work well with tools such as CRISPR gene editing and omics-based assays (such as RNA sequencing or proteomics), making it easier to link specific genetic changes to endothelial cell behavior. [4, 6]
Points to Keep in Mind
Researchers are still working to further improve the resemblance of iPSC-derived endothelial cells to mature primary endothelial cells from specific tissues. Some studies have found that while iPSC-differentiated endothelial cells can form vessels and respond to flow, certain features, such as long-term stability or full-barrier function, may still require further optimization. [10] Nonetheless, iPSC-derived endothelial cells already offer many useful models for various questions in the realm of vascular biology and disease.
Choosing an Endothelial Model
Choosing the right endothelial cell-based model depends on key factors, such as experimental aims, experimental complexity and the resources you have available in your lab. In many projects, iPSC-derived endothelial cells can offer clear advantages over other options; however, that may not always be the case.
Let’s break down some common situations that researchers find themselves in and which solutions may be best for that application:
- If you need a simple system for basic questions about blood vessel growth or inflammation, HUVECs or primary endothelial cells can often be a practical starting point. These are well-documented and supported by many published methods. [3]
- If you are interested in a specific organ, such as the brain or lung, primary endothelial cells from that tissue, or specialized barrier models, can be helpful. One main limitation to note, though, is that they are often in short supply and can introduce batch-to-batch variation.
- When your work focuses on patient-specific disease mechanisms or genetic variants, iPSC-derived endothelial cells are generally the strongest choice because they carry the patient’s own DNA and can be expanded over time and reused for future purposes. This makes them well-suited for modeling rare diseases, comparing gene-edited (corrected and mutant) cells and running repeated experiments on the same genetic background. [4, 6]
- For studies of tumors and angiogenesis, co-cultures with tumor cells and endothelial cells are typically useful to capture the local tumor environment. These systems can also be built using iPSC-derived endothelial cells to add human and patient-specific context. [4, 12]
- In projects requiring large screening, models that are scalable and consistent are imperative. In this context, iPSC-derived endothelial cells provide a renewable and more standardized source of human (and optionally, patient-specific) starting material.
For many projects, a mixed approach works well. For example, some labs choose to use HUVECs for early screening and then transition to iPSC-derived endothelial cells for validation in more relevant or patient-specific cellular models. [5, 13]
Summary
Endothelial cells are involved in many diseases and are critical for researchers across various fields. Having high-quality, reliable lab models of these cells is essential for research and testing new therapies.
While common models such as HUVECs, primary tissue-derived cells, and immortalized cell lines have their advantages and limits in terms of source, growth, and resemblance to real tissues, iPSC-derived endothelial cells offer an option that is human, renewable and reflective of individual patients, conditions or diseases, while also supporting larger and more consistent studies. By matching the model to the research question, scientists can better design studies that are both practical and more relevant to human biology.
References
1. https://my.clevelandclinic.org/health/body/23471-endothelium
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC6769656/
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC3311155/
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC12841387/
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC8260893/
6. https://www.nature.com/articles/s41598-019-40417-9
7. https://onlinelibrary.wiley.com/doi/10.1002/jcp.10333
8. https://www.sciencedirect.com/science/article/pii/S0753332225006092
9. https://www.nature.com/articles/s41598-018-20966-1
10. https://pubmed.ncbi.nlm.nih.gov/30414271/
11. https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2022.953062/full
12. https://www.nature.com/articles/s41598-017-10699-y
13. https://pmc.ncbi.nlm.nih.gov/articles/PMC9368986/