MIT scientists have developed a groundbreaking method to grow artificial blood vessels, marking a significant advancement in tissue engineering. This innovative approach involves using mechanical stretching to enhance the growth of new capillary-like sprouts and guide their direction. The research, published in the Proceedings of the National Academy of Sciences, introduces a vessel-on-a-chip platform that utilizes magnets to apply controlled strain within a three-dimensional tissue model.
The device, smaller than a postage stamp, features a central hollow channel lined with human endothelial cells, which naturally form blood vessels. An external magnet moves an embedded actuator, pulling the surrounding gel and stretching the vessel wall. This system allows researchers to adjust the strength, frequency, and direction of stretching, offering precise control over blood vessel growth.
In their experiments, the team applied different levels of strain (5% and 15%) and stimulation methods (dynamic and static) to the vessels. They found that all forms of mechanical stimulation increased sprouting, but the strain level influenced the pattern of growth. Five percent dynamic strain produced the highest number of sprouts, while 15 percent dynamic strain resulted in fewer sprouts but longer vessels.
The direction of stretching also played a crucial role. When the gel was stretched along one axis, sprouts grew preferentially along that line. This finding highlights the importance of mechanical cues in guiding vessel growth. The researchers further demonstrated that changing the direction of stimulation after three days did not erase earlier growth but instead allowed sprouts to continue extending in the newly imposed direction.
One of the key insights from this study is the role of PIEZO1, a gene that controls a pressure-sensitive ion channel in cell membranes. By suppressing PIEZO1, the researchers found that it contributed to strain-induced vessel growth. However, barrier strengthening remained intact, suggesting that other force-sensing pathways control that response.
The practical implications of this research are significant. Precisely guiding small blood vessels could overcome a major barrier in tissue engineering. Existing methods often struggle to create fine networks with controlled geometry. This magnetic platform offers a novel approach to add physical instructions after tissue growth has begun, allowing researchers to guide vessels through three dimensions without relying solely on chemical gradients.
Future versions of this platform will need to incorporate additional cell types and flowing blood to better replicate native circulation. The researchers are also exploring the potential of mechanically patterned vessels to improve engineered muscle function. If this approach proves effective in more complex tissues, it could lead to the development of thicker, better-supplied implants and more realistic laboratory models for studying diseases involving abnormal blood vessel growth.
