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A new way to warm up frozen tissue could help with the organ shortage

This could help with the organ shortage

Unlike convective warming, the new nanowarming method prevents tissue damage by evenly reheating cryogenically preserved tissues.
Credit: Manuchehrabadi et al., Science Translational Medicine (2017)]

A new way to warm up frozen tissue using tiny vibrating particles could one day help with the problem of organ shortages.

We know how to cool organs to cryogenic temperatures, which is usually below 320 degrees Fahrenheit. But the organs can’t be stored for long — sometimes only four hours for heart and lungs — because they get damaged when you try to warm them up. As a result, more than 60 percent of donor hearts and lungs aren’t transplanted. In a study published today in Science Translational Medicine, scientists used nanoparticles to warm up frozen tissue quickly and without damaging the organs. Within a decade, this could lead to being able to store entire organs in organ banks for a long period of time, the authors say.

For today’s study, the team rewarmed 50 milliliters of tissue and solution with magnetic nanoparticles. Magnetic particles create heat in electromagnetic fields, says study co-author Zhe Gao, an post-doc studying nanotechnology at the University of Minnesota. Basically, the scientists infused a tissue with a special kind of nanoparticle made of silica-coated iron oxide. Then, they expose it to a magnetic field. Think of the nanoparticles as antennae. Once they get pick up the “signal” from the magnetic fields, they start to vibrate, and this creates the heat that warms up the organ quickly.

Cryopreservation has traditionally focused on the best way to cool tissue, but warming is one of the biggest obstacles. There are two big challenges. First, because the freezing is uneven, some parts become colder than others. The cold organ is already brittle and prone to shattering when it gets warmed up, but this becomes an even bigger risk if one part warms faster than the other. Freezing also forms little tiny ice crystals, which don’t hurt the organs when they’re being cooled. But those ice crystals are “like little atomic bombs ready to explode,” says Mehmet Toner, a professor of bioengineering at Harvard-MIT Health Sciences and Technology who was not involved with the study. When you slowly warm the organ, they grow and can damage the cells and tissues.

This new process overcomes both obstacles. It warms all parts of the organ at the same rate, which means it’s less likely to shatter. And because it happens quickly, you can rewarm before the ice crystals grow too big. The idea comes from a certain type of cancer therapy, which uses nanoparticles and infrared fields to kill off tumors.

Though the scientists haven’t rewarmed organs yet, this 50 milliliters is still a big improvement because, previously, researchers could only rewarm 1 milliliter of tissue. Next, the team will begin testing this technology in organs: the heart of rats and rabbits, then pig organs, and, eventually, human organs. There are also regulatory issues that will need to be solved before this technology comes to market, says study co-author John Bischof, a biomedical engineer at the University of Minnesota. And it seems unlikely that we’ll be able to rewarm human bodies within the next century, says co-author Kelvin Brockbank, a biologist at Clemson University.

This study is “a very serious step forward using an out of the box concept,” says Toner, from Harvard. “As the population ages, the need for organ transplantation is becoming a serious issue,” he added. “There’s more work to be done, and this is going to open up a whole new field as investigators work in warming.”