Previously Freeze-Dried Heart Valves Successfully Implanted Into Sheep

Rather than using artificial valves, as in a lot of modern heart surgery, doctors could in theory pick which freeze-dried valve they need off a shelf. ChaNaWiT/Shutterstock

For the first time ever, scientists have successfully used tissue that has been freeze-dried and then rehydrated in live surgery. The team of researchers from the Leibniz Research Labs for Biotechnology and Artificial Organs in Hannover, Germany, carried out this pioneering work on sheep, transplanting previously preserved heart valves in the ovine patients.

The process works by dehydrating the underlying structure of the heart valve, which can then be stored for a long period of time. When the tissue is then needed, it can simply be rehydrated by soaking it in a solution for 24 hours, before being used in exactly the same way as fresh tissue. The new technique has the potential to enable doctors to store donated tissue for months or even years before it is needed, radically altering how we carry out transplants.

This latest study, published in Acta Biomaterialia, is a follow-on and step up from previous work in which the team tested the viability of the technique back in 2012. In that earlier paper, they were exploring whether or not the structures would be damaged by the freeze-drying process, and once that was confirmed not to be the case, the team has moved on to assessing its viability in living animal models.  

The process works by taking the donor tissue, in this case a piece of heart valve, and stripping it of all its cells. This leaves behind the structure of the valves, which are then soaked in a sugary solution in order to aid in their preservation. The last step is to freeze-dry the tissue in order to suck out all the moisture.  

When dried out, the little bits of tissue look not unlike strips of beef jerky, according to the researchers. The similarities don’t end there though because as with the meaty snacks, it is thought that – in theory at least – the freeze-dried tissue can be kept indefinitely.

The technique means that the valves only need to be stored in airtight containers at room temperature, which is far more convenient than current methodology. At the moment, biological samples only have a short shelf life, as once they have been processed they are stored in a liquid that only keeps them viable for around four months.

This means that doctors have to work quickly to find suitable matches, and sometimes have to settle with one that might be less than perfect. In principle, this new technique could allow doctors to pick whichever sample they need for a transplant off a shelf 24 hours before an operation is due to begin.

The researchers also think that, while they are yet to try it, the process should also work with relatively simple organs, such as the esophagus, bladder, and possibly even the liver.

[H/T: New Scientist]

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