In a discovery that surprised even the researchers responsible, a new type of cell – resembling a glial cell usually only found in the brain and spinal cord – has been found in the heart.

Dubbed “nexus glia” because of their net-like appearance around the heart, the team behind the discovery believe these new cells may hold the key to how we understand heart disease and defects in the future.

The findings were published recently in the journal PLOS BIOLOGY.

“For me the definition of great science is something that you discover that opens up even more questions,” said study co-author Cody Smith. “This, I think, is the definition of that.”

The newly-discovered cells resemble astrocytes – star-shaped multitasking cells, of which our brains are chock-full. These cells play a crucial role in building and maintaining neural networks in the brain and spine, but aren’t thought to live anywhere else in the body – which is weird, right? If they’re so important, why wouldn’t they be found in other places too?

Astrocytes belong to a class of cells known as glial cells – the name comes from the Greek for “glue,” the only function the 19th-century neurologists who discovered the cells were able to ascertain for them. These days, we know a bit more about glial cells, but not everything – we know they can be found throughout the body, including organs like the pancreas, spleen, lungs, and intestines, for instance, but we don’t know precisely what they do there.

Neither is it clear why astrocytes in particular, so crucial to neuron function in the brain, seem basically non-existent in the peripheral nervous system (PNS) – that is, the parts of the body connected by nerves outside of the brain and spinal cord.

“We were puzzled,” Smith explained, “so we searched for glial like cells in the PNS.”

“Really, [first author] Nina Kikel-Coury searched!” he added. “Nina came to my office every week with more data that supported a glial identity, many of which I was admittedly unconvinced by … Eventually the data became too much to dismiss.”

To begin with, the team looked at zebrafish – an animal that’s rapidly become the guinea pig of choice for scientists modeling diseases in recent years. They discovered a type of cell in the zebrafish heart that resembled astrocytes – and cross-species analysis revealed the same cells in human and mouse hearts. Formed before birth from the same group of cells that eventually go on to build our faces and smooth muscles, the cells spread out through the heart from the outflow tracts – and that provided an important clue as to the nexus glia’s function.

“'This is fascinating because the outflow tract is defective in 30 percent of congenital heart diseases,' Nina explained … Scoring heart beats she noticed increased heart rates when nexus glia were disrupted,” wrote Smith.

What’s more, when the nexus glia were deprived of a key glial development gene, the heartbeat became irregular. “I thought that if we could find a new cellular piece to the cardiovascular puzzle, it could be foundational for future work,” explained Kikel-Coury.

As with so many discoveries of this nature, the full implications are yet to be seen. While Smith thinks the nexus glia “could play a pretty important role in regulating the heart,” he cautioned that they “don’t completely know” their precise function yet.

“[We now] have 100 questions we didn’t even know existed, so we’re following up on them to explore this path that has never been studied before,” said Smith. “This is another example of how studying basic neurobiology can lead to the understanding of many different disorders … I’m excited about the future.”