Chinese team removed cryoprotectants from vascular grafts in 15 minutes and preserved the grafts after transplantation into rats

Chinese team removed cryoprotectants from vascular grafts in 15 minutes and preserved the grafts after transplantation into rats

On July 18, Materials Today Bio published a paper describing CTX-RYST, a method for vitrifying small arterial grafts. After the grafts were transplanted into the carotid arteries of rats, stenosis was 4%, compared with 24% in the group treated with the standard VS55 solution.

A small vascular graft is a segment of artery less than six millimeters in diameter that a surgeon can use to replace a damaged section of a blood vessel. Successful storage requires preservation of the endothelium, the layer of cells lining the vessel. These cells come into contact with blood, limit clot formation, and help keep the vessel open after transplantation.

During vitrification, water and the cryoprotectant solution are cooled into a glass-like state without forming ice crystals. This requires the vessel to be infused with a concentrated solution. Ice ruptures cells, while the introduction and removal of the cryoprotectant solution alter cell volume and the surrounding chemical environment. The vessel can therefore be damaged during cryoprotectant removal itself.

In the paper by Zhiyang Zhao, Bing Zhang, and Gang Zhao, CTX-RYST combines these two steps. Low doses of ice inhibitors suppress crystal formation, after which the cryoprotectants are removed in a single 15-minute step instead of the approximately one-hour multistep procedure. The authors propose that this method better preserves lamin B1, a protein in the nuclear envelope, allowing the nucleus to tolerate the rapid change in its environment more effectively.

The team first tested endothelial cells. After the procedure, 89% of the cells attached to the surface, compared with 8% under the comparator protocol. The grafts were then transplanted into the carotid arteries of rats. After six weeks, the mean degree of stenosis, meaning narrowing of the vessel lumen, was 4% after CTX-RYST and 24% after VS55.

For a small arterial graft, cooling accounts for only half of the procedure. The endothelium must also survive removal of the solution and keep the vessel open to blood flow after transplantation.