Few would expect any human-related insights to come from a nematode like the Caenorhabditis elegans, let alone from the way they spit up food. Yet in a paper recently published in Current Biology, researchers from the Massachusetts Institute of Technology have noted properties of the worm’s spitting behavior that could lead to a better understanding of valvular heart disease.
The findings revolve around something called myogenic muscles. These are muscles that expand and contract without being signaled by the nervous system. In humans, the myogenic muscles in the heart work to pump blood through the tubes leading to various arteries. The heart uses signals from the brain to regulate other functions like heart rate, but the act of pumping itself is done without neural input.
The Caenorhabditis elegans‘ pharynx is made up of myogenic muscles. The worm’s pharynx rhythmically pumps bacteria into the worm’s intestine. It is essentially the same behavior (pumping substances in one direction) that the heart’s myogenic muscles perform.
The worms have filters to detect toxic substances in what they eat. If a substance is detected, the myogenic pharynx vomits the whole meal out instead of sealing the filter. The behavior is similar to a condition in humans called aortic regurgitation. Like the name suggests, it is a situation where the heart valve does not fully close and oxygenated blood flows backwards into the heart instead of out into the body. Although doctors and scientists have been aware of the condition for some time, the exact cause and triggers of it have remained elusive.
Humans have billions of neurons across their bodies. The elegans worm only has 302, allowing for their neural connections to be fully mapped. MIT scientists isolated the neuron, called M1, which controlled the spitting behavior in worms.
With the M1 neuron isolated, the scientists hope to translate the development into human findings. If, for instance, scientists discover that the human heart also has M1 neurons, then it could suggest that some sort of harmful substance is being sensed in the blood that triggers aortic regurgitation (or, possibly, a false-positive that triggers regurgitation).
Current treatment for valvular disorders involves surgery. It is hoped that the neural finding may lead to more therapeutic and less invasive treatments…all thanks to a vomiting worm.
Sources for Today’s Article:
Bhatla, N., et al., “Distinct Neural Circuits Control Rhythm Inhibition and Spitting by the Myogenic Pharynx of C. elegans,” Current Biology. Accessed July 27, 2015. doi: http://dx.doi.org/10.1016/j.cub.2015.06.052.
Paddock, C., “‘Worm Spitting’ Offers Insights for Heart Research,” Medical News Today web site, July 27, 2015; http://www.medicalnewstoday.com/articles/297324.php.