Seeing Inside a Cell express
In winter, puddles freeze, and ice cracks the asphalt. Inside a living cell, freezing does something similar: ice crystals tear its membrane. To prevent this, the cell is soaked in a special solution, like antifreeze for a car. But precision is key: too little solution and ice still forms; too much and the solution itself poisons the cell. How do you know how much protective substance got inside and how it spread? Until recently, this was nearly impossible.
Researchers at the University of Minnesota have proposed a new method. They use an X-ray tomograph that takes many images from different angles, and then a computer assembles them into a 3D picture. But a regular tomograph can't tell the difference between the protective solution and water: they are almost equally transparent to X-rays. The scientists taught the device to distinguish them by subtle differences in how the rays pass through the material. It's like learning to spot people in a crowd wearing identical gray clothes by noticing a slightly different shade of collar.
It turned out that the protective solution penetrates tissue unevenly: in some places there is more, in others less. Previously, it was thought that it distributes evenly, like sugar in a cup of tea after stirring. The new data show that this is not the case, and this is important for preserving cells during freezing. Now it's possible to adjust the solution composition and soaking time so that cells survive more reliably. This is a step toward storing organs for transplantation not for hours, but for weeks and months.
The word "vitrification" comes from the Latin vitrum, meaning glass. During rapid freezing, the solution doesn't crystallize but becomes glass-like: solid but without sharp edges.
In the movie "Forever Young," the hero is frozen in a capsule to be awakened decades later. The new method could make such freezing safer, though for now it's only about cells and tissues.