A rare heart bone “os cordis” is discovered in chimpanzees

A rare heart bone "os cordis" is discovered in chimpanzees

It’s a very surprising discovery. A study of the heart of chimpanzees shows that in some of these monkeys a bone in the heart can be found. The bone is only a few millimeters in size, but may have a major impact on their health, researchers write in the journal Scientific Reports.

There are few animal species that possess such a bone in the heart – also called os cordis. The os cordis is present by default in some animal species – such as cattle. In other animal species – such as the otter, but also the dog and camel – it is sometimes found in animals. And chimpanzees also sometimes turn out to have it. It is still unclear why one chimpanzee does have it and the other does not.

“Our study shows that there is no correlation between whether a chimpanzee has the ox cordis and its age or gender,” states the lead author Dr. Catrin Rutland from the University of Nottingham. For example, females were found to have it about as often as males. And while previous studies have suggested that an os cordis is more common in older animals, the oldest chimpanzee that Rutland and colleagues studied did not appear to possess it.

Image: Dr. Catrin Rutland -University of Nottingham

The researchers found the bone more often in the heart of chimpanzees suffering from myocardial fibrosis, a heart condition that is common among chimpanzees and can lead to cardiac arrhythmias, among other things. “We also discovered os cartilage – similar to os cordis, but made from cartilage instead of bone – to chimpanzees suffering from myocardial fibrosis in some of them,” Rutland says. “So our chimpanzees with the most severe form of myocardial fibrosis all had os cordis or os cartilage (which can develop into bone over time), while the chimpanzees who did not or hardly suffered from the heart condition possessed neither of these structures.”

The function of the ox cordis is still shrouded in mists in both chimpanzees and other animal species. But the fact that the chimpanzees have been found in os cartilago does give a little more insight into the mechanisms that lead to the formation of the bone, the researchers claim. Follow-up research should show exactly how it affects the health of chimpanzees. And Rutland hopes it will lead to better care for and ultimately the conservation of the endangered chimpanzee, which has a lot to do with heart problems both in the wild and in captivity. “Understanding why the os cordis occurs, how the bone functions, and what role it plays gives us more insight into how the body of chimpanzees with heart disease reacts and why the body reacts this way. Understanding how diseases arise and what they cause is an important part of treating and preventing them. Up to 77 percent of chimpanzees in zoos are heart-related and we know that heart disease also occurs in the wild and leads to premature death, so it’s important to study this condition.”

Finally, the research may also have consequences for humans, who are quite closely related to chimpanzees. Because the researchers do not rule out the fact that some people also have such a small bone in the heart. It may be hard to imagine that such a bone has escaped our attention all this time, but Rutland explains that that is not so far-fetched.

In chimpanzees, we hadn’t noticed until recently. “Chimpanzees who die often undergo an autopsy, but this part of the heart (where the bone may be located, ed.), is often not examined. And the same goes for people. In addition, it requires advanced technology to see the very small bone and it is unlikely that you will see it on a normal CT or MRI scan or X-ray. It is therefore certainly possible that people develop this heart disease – possibly in response to disease – but that we have not yet seen it, because – as with chimpanzees – it is very small.” She points out that the chimpanzee’s bone is only between 5 and 7.8 millimeters in size. “Moreover, despite our extensive knowledge, new anatomical structures are still found in many species, including humans.”

For now, the exciting discovery clearly raises a lot of new questions, and Rutland hopes to be able to answer some of them in due course. “Our research continues and we will try to find out what the os cordis does in the heart and how and why the bone originates both in chimpanzees and within other species.