A team at the University of Bonn has established a highly efficient and cost-effective technique to produce functional endothelial cells from human induced pluripotent stem cells, potentially advancing cardiovascular disease research and organoid development. Scientists at the University Hospital Bonn (UKB) and the University of Bonn have made significant strides in the field of cardiovascular research by developing a novel method to generate endothelial cells from human induced pluripotent stem cells (hiPSCs). This new approach, which utilises a specific transcription factor, offers a more efficient, cost-effective, and reproducible way to create these crucial cells for in vitro studies of cardiovascular diseases.

Their research is published in Cardiovascular Research [1].

Endothelial cells, which line the interior of blood vessels, play a vital role in various bodily functions, including blood pressure regulation and clotting. They are also implicated in the development of cardiovascular diseases, making them a critical focus for researchers seeking to understand and potentially treat these conditions.

The ETV2 protocol: A game-changer for stem cell differentiation

The research team, led by Professor Bernd K. Fleischmann, Director of the Institute of Physiology I at the UKB, has refined a differentiation strategy that centres on the activation of a specific transcription factor called ETS variant transcription factor 2 (ETV2). This approach, dubbed the ETV2 protocol, builds upon recent work by an international team including researchers from Harvard Medical School and the UKB. Dr Sarah Rieck, the study’s co-corresponding and first author, explains the advantages of their improved protocol: “We were able to show that the ETV2 protocol we improved is more efficient and cost-effective than the protocol with growth factors. This is because it delivers endothelial cells more quickly, requires fewer additives for the culture medium and does not require an additional purification step.”

The researchers compared their ETV2 protocol with the previously established method that relies on growth factors to induce differentiation. They found that their new approach not only produced endothelial cells more rapidly but also with greater purity and stability over extended cultivation periods. Moreover, the ETV2 protocol demonstrated high reproducibility and ease of transfer to other hiPSC lines, making it a potentially valuable tool for researchers across the field. The resulting cells exhibited characteristic proteins and functional properties typical of endothelial cells, further validating the efficacy of this new method.

One of the notable features of the improved ETV2 protocol is its flexibility. By modifying certain aspects of the differentiation process, researchers can preferentially obtain endothelial cells with either arterial or venous characteristics. This versatility could prove invaluable for studying specific vascular conditions or developing targeted therapies

Endothelial cells differentiated in the culture dish from ETV2 iso2 hiPSCs in red. The cell nuclei are blue.
Photo credit: University Hospital Bonn (UKB) / S. Rieck, Institute of Physiology

Maturity considerations and future directions

While the endothelial cells produced through the ETV2 protocol showed a slightly higher degree of maturity compared to those differentiated using growth factors, both types fell short of the maturity level seen in human umbilical vein endothelial cells. Professor Volker Busskamp, a co-author of the study, attributes this to the absence of external influences such as blood flow in
the in vitro environment.

Looking ahead, the research team anticipates that their PGP1 ETV2 iso2 cell line and the resulting endothelial cells will prove invaluable for modelling and studying human vascular diseases in vitro. Dr Rieck and Professor Fleischmann are already exploring this potential in their work with the DFG Collaborative Research Center Transregio (TRR) 259 “Aortic Diseases”.

Applications in organoid research

Beyond disease modelling, the researchers see potential applications for their endothelial cells in the burgeoning field of organoid research. The ability to incorporate a vascular system into organoids could significantly enhance their complexity and physiological relevance, opening new avenues for drug testing and tissue engineering.

As they continue to refine their technique, the Bonn researchers are keen to explore cultivation methods that could increase the ‘degree of maturity’ of the endothelial cells following differentiation. Dr Rieck emphasises the importance of this goal: “We are also interested in which cultivation methods increase the ‘degree of maturity’ of the endothelial cells following differentiation, so that their profile corresponds more closely to that of adult endothelial cells.” This research represents a significant step forward in the field of cardiovascular research and stem cell biology. By providing a more efficient and reproducible method for generating endothelial cells, the team at the University of Bonn has opened up new possibilities for studying vascular diseases and developing potential treatments. As they continue to refine and expand upon this technique, the impact on both basic and translational research could be substantial.

Reference:
1. Rieck, S., et al. (2024). Forward programming of hiPSCs via the transcription factor ETV2: rapid, reproducible, and cost-effective generation of highly enriched, functional endothelial cells. Cardiovascular Research. https://doi.org/10.1093/cvr/cvae129