When some snakes bite, they can deliver a powerful punch of toxin-filled venom that damages organ systems and can even result in death. Annually, around 400,000 snakebite victims die worldwide. One of the most devastating effects of snake venom is its ability to cause internal bleeding, or hemorrhage.
Now, a team of researchers developed an artificial system of blood vessels that they can use to study exactly how snake venom breaks them down and causes bleeding.1 They created an organ-on-a-chip model of blood vessels that better mimics the human circulatory system to study this hemorrhagic process and found that venoms from different snake species work to break down blood vessels in different ways. They published their results in Scientific Reports. This 3D blood vessel model now allows researchers to effectively study the peculiarities of venoms from different species and test different antibodies to mitigate the detrimental effects.
“This is a very good contribution to our field because it allows us to study the mechanism of toxicity in this very well-defined model,” said José María Gutiérrez Gutiérrez, a toxicologist at the University of Costa Rica, who was not involved with the study. “[The study] furthers our understanding of the mechanism of action of hemorrhagic toxins because it reproduces the real dynamics of blood flow in blood vessels”.
Previously, researchers studied the effects of snake venom on blood vessels by using cultured endothelial cells, the cells that make up the wall of vessels. However, these so-called static models fail to reproduce what occurs in vivo since they lack a key component of the circulatory system: the physical forces exerted by blood flowing through the blood vessels. These biophysical forces, Gutiérrez Gutiérrez said, potentially contribute to the damage caused by snake venom.
To create a model of the human circulatory system, biologist Mátyás Bittenbinder teamed up with chemist Jeroen Kool, both researchers at Vrije University Amsterdam.
They cultured endothelial cells alongside essential blood vessel molecules, such as collagen, and introduced the mixture into microfluidic channels. There, the cells formed into 3D tubular structures that resembled blood vessels.
Once they had the model in place, the team tested venoms from four different common snake species: the West African carpet viper, the many-banded krait, the Mozambique spitting cobra, and the Indian cobra. As the venom flowed through the artificial blood vessels, the researchers measured how much fluorescent tracers leaked out of the vessels, an indicator of how well the endothelial cells held up in the presence of the toxic cocktails. All four snake venoms elicited blood vessel leakage, although some more than others and at different time points throughout a 90-minute observation period.
“It’s a better mimic of the in vivo conditions and you can look at the effects [in] real time, which is obviously not possible in other animal models,” said Bittenbinder. “You can really see the blood vessel losing its integrity”.
But, when the researchers explored how exactly this disruption was occurring, they found that the venoms exhibited different mechanisms of action. In particular, the highly hemorrhagic venom from the West African carpet viper, which is native to Nigeria, seemed to “delaminate” the endothelial cell layer from the extracellular matrix. Other snake venoms, such as those of the Mozambique spitting cobra and the Indian cobra, induced cytotoxicity by directly disrupting the cellular membrane and killing off the endothelial cells.
Moving forward, researchers can use the system to probe specific toxins in the venom and identify the components responsible for the damage, Gutiérrez Gutiérrez said. “Venoms comprise a large mixture of substances with different actions, so it’s like a black box.”
Additionally, the new technology enables scientists to run high-throughput screens of molecules that could stop the damaging effects of venoms. “We want to use this information to see how can we block the cytotoxicity,” said Kool. “It’s not a miracle bullet that will bring the medicines to the world but it’s another tool that is valuable in being better able to develop new treatments.”
