Artificial rapidity heart valves

U.S. and Swiss scientists have developed an inexpensive way to create heart valves in minutes that work immediately after implantation in sheep. The study was recently published in the journal Matter.

According to statistics, there are 12 million heart valve patients in the world, and nearly 1 million people die every year. Especially children with heart valve disease often require heart surgery to replace the valve. However, existing heart valve replacements cannot grow as the child grows, requiring the patient to repeat this high-risk procedure throughout their lives.

The pulmonary heart valve consists of 3 partially overlapping lobules that open and close with each heartbeat. They are responsible for controlling the one-way blood flow through the heart, and with each heartbeat, they open fully to allow blood to flow forward, and then turn off completely, preventing blood from flowing back.

To make the valve, the researchers used airflow jets to direct liquid polymers onto a valve-shaped frame, creating a seamless network of tiny fibers. These valves are designed to be temporary and renewable: they provide a porous scaffold for cells to infiltrate, expand, and eventually replace biodegradable polymers.

“The two biggest advantages of this approach are speed and spatial fidelity.” Sarah Motta, a co-first author and biophysicist at Harvard University and the University of Zurich in Switzerland, said: “We can make very small fibers at the nanoscale, mimic the extracellular matrix that heart valve cells use to grow, and turn out the complete valve in minutes, whereas currently available technologies may take weeks or months.” ”

Motta calls the method “focused rotary jet spinning,” similar to “a marshmallow machine with a hair dryer in the back.” While long-term in vivo studies were needed to test the durability of the valves, they effectively controlled blood flow in sheep for an hour.

Kit Parker, a bioengineer at Harvard University and corresponding author of the paper, said: “Cells grow at the nanoscale, which 3D printing cannot achieve, but the new technology can set up nanoscale spatial scaffolds so that when cells infiltrate the scaffold, they feel like they are in the heart valve, not in the synthetic scaffold.” There are certain tricks to this. ”

Using a pulse replicator, a machine that simulates a heartbeat, the team tested the valve’s strength, elasticity and ability to switch on and off repeatedly.

“A normal heart valve has billions of switching cycles over a person’s lifetime, so they are constantly stretched and stimulated.” Harvard researcher Michael Peters, a co-author of the paper, said: “They need to be very elastic to maintain their shape under these mechanical stimuli, and they must also be strong enough to withstand the back pressure of the blood trying to flow back.” ”

They also cultured heart cells on valves to test their biocompatibility and see if the cells penetrated well into the scaffold. “The valve is in direct contact with the blood, so we need to check if this material can cause blood clots or blockage of blood vessels.” Motta said.

The researchers tested the valve’s immediate function in sheep. Sheep are a good animal model because the physical forces inside sheep and human hearts are similar, and in addition, sheep hearts also represent an “extreme” environment for heart valves because sheep metabolize calcium faster, which increases the risk of calcium deposition, a common complication in heart valve recipients.

The surgeon implants the valves into two sheep and monitors the position and function of the valves with ultrasound within an hour. Both valves implanted successfully and functioned immediately, but one sheep’s valve fell off after a few minutes — a reason the researchers believe is because the valves are not the right size for the animal. In the second sheep, the valve showed good function within an hour, and autopsy analysis showed that there were no complications of tearing or thrombosis, and the cells had begun to penetrate and adhere to the valve.

Next, the team plans to test the performance of the new valve over a longer period of time and in more sheep. Peters said: “We wanted to see how well our valves function over a period of weeks to months, and how effectively and quickly the cells and tissues of the sheep reshape the scaffold. ”

“Developing a drug that works on patients is a long process, and it should be long, and you have to experiment on a lot of animals before you put something in humans.” Parker said. (Source: Feng Weiwei, China Science News)

Concept art of artificially created heart valves. Image from the author

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