MIT guided vascular branch growth by magnetic stretching in a human vessel model

MIT guided vascular branch growth by magnetic stretching in a human vessel model

In a collagen gel, researchers varied the strength and direction of stretching near the vessel wall. Weak stretching produced more branches, while strong stretching caused individual branches to grow longer.

Engineered tissue needs a network of small blood vessels to supply its cells with oxygen and nutrients. Large channels can be printed, but capillaries must grow from cells and connect to form a functional network. Their shape cannot yet be controlled with the same precision.

On 14 July, MIT published an overview of a study published in PNAS on 6 July. The team created a hollow channel in a collagen gel and lined it with human endothelial cells, which form the inner wall of blood vessels. The researchers placed a small magnet beside the channel. An external actuator moved the magnet and stretched the gel near the vessel wall for one hour per day over three days.

The strength of the stretching changed the number and length of the branches, while its direction determined their path. Stretching the gel by 5% of its width produced more branches. At 15%, fewer branches formed, but individual branches grew longer. When the researchers changed the magnet's direction of motion along three axes, the branches turned with the direction of stretching, producing shapes that included L-shaped branches. Some branches retained an internal channel connected to the original vessel. The authors confirmed this connection using a fluorescent dye.

For now, this method controls only the early growth of branches in a single-vessel model. The authors have not yet created a complete vascular network. The next test is to use these branches to form a dense network that can sustain complex tissue over time and connect to the bloodstream after transplantation.

The researchers also examined how the cells responded to stretching. When they suppressed PIEZO1, the gene that encodes a mechanically sensitive ion channel, fewer branches formed. However, stretching still maintained the barrier function of the vessel wall. This result indicates that other mechanisms also contribute to the cellular response to force.