Tardigrades are about 0.5 mm long, and have eight limbs tipped with claw-like structures that propel their plump, segmented bodies through a variety of watery, algae-rich environments all over the world. Since the successful revival and breading of the frozen tardigrade a few years ago, scientists have put them through their paces to find out how hardy these creatures actually are. Tardigrades have even been sent into low-Earth orbit, where they weathered exposure to space's vacuum, cosmic rays and solar ultraviolet radiation.
Their secret lies in an ability to expel all the water in their cells and generate a protective coating, suspending them in a deathlike but still-living state that they can maintain until conditions improve. This also allows them to survive without water for up to a decade.
Scientists at Harvard Medical School, the University of Washington and MIT are now studying tardigrades to see if they can provide a blueprint for biostasis in humans. Their research is being funded by the Defense Advanced Research Projects Agency (DARPA), and they are looking for ways to extend the “golden hour” between a traumatic injury and medical intervention. This could apply to a soldier suffering a traumatic injury on the battlefield, someone suffering a stroke or heart attack, or cases of sepsis.
The researchers say that any biostasis solutions they come up with would not be a long-term fix, as biological processes would return to normal after a short period. However, biostasis would buy doctors and medical personnel more time to get the patient the help they need.
So far, researchers have found that tardigrades change the regulation and production of certain proteins. This effectively protects the organism’s cellular components until such time when conditions are more habitable. It is the discovery of these proteins and their roles in tardigrade survivability that the team is using as a proof of concept for the application of “novel unstructured proteins as inducers and supporters of crypto-biotic states”.
According to Harvard’s Pamela Silver, principal co-investigator on the project, these proteins are called IDPs: intrinsically disordered proteins. “The functions of this class of proteins are under intense recent research, so our results play into the overall picture as well. Our idea is to design proteins that have similar action in human cells and tissues. The notion is that by forming a special state in cells, that the proteins then can become protective. It is of note that our new proteins could prove a basis for further drug design,” she said in an interview.
The researchers have found that not all IDPs slow down cellular aging, so the team needs to work out the structure of the proteins that help tardigrades survive extreme conditions. After that, they will need to design a protein that can be used by humans.
This will be an extremely complicated task, scientists say. The sequence of the amino acids that make up a protein determine its shape. The shape then determines its function. What the team has to do is find the right shape from an infinite number of possible amino acid combinations. To do this, the researchers are going to use a computer model to run through the possibilities, then test them to rule them out or investigate them further.
“We have a design-build-test cycle where we test many proteins at once. The first step is to use machine learning to design new proteins. Then we will test their ability to preserve activities of proteins. This is followed by cell-based tests for prolonging life under harsher conditions, followed by tests in organoids that mimic tissues and, lastly, in animal models,” Silver explained.
She points out that the team is developing totally new “designer” proteins based on what nature has provided, and the resultant “drug” will be a protein. The scientists will also have to work out how to deliver the protein to cells.
While the research is in its very early stages, it shows promise. A few years from now, people who would have lost limbs as a result of massive trauma might well be thanking tardigrades for their intelligent design.