While some scientists are exploring further and further into space in search of life, other scientists are looking deeper and deeper into our own bodies to learn more about humanity. This week, for example, a team of German immunologists published a new study in the journal Nature Metabolism describing a newly discovered network of blood vessels buried within our bones. It turns out that the connection between our circulatory and skeletal system is more intertwined than we thought.
Led by Matthias Gunzer of University Duisburg-Essen, the team used chemicals on mouse bones to turn them transparent. And once they did so, they could see tiny red blood vessels crossing the shaft of the bone. Now, it is common knowledge that blood exists within the bone, but that is called bone marrow—where the body makes immune cells—and it does connect to the circulatory system, as it is. This new discovery, however, offers a more intricate look at bone health and might actually shed new light on bone diseases like osteoporosis.
Looking at the lab mouse’s lower leg bone—which is about the size of a match stick—the researchers found upwards of one-thousand capillaries. They called these trans-cortical vessels. Prior to this discover, scientists had only known of a few blood vessels entering the bone at either end (again, connecting to the bone marrow). These newly-discovered capillaries, however, covered the entire bone to provide most of its blood supply.
From there, the team observed that human bones have similar trans-cortical vessels. In mice, these vessels are the avenue by which immune cells exit the bone marrow (for distribution throughout the body). Obviously, Gunzer and his team theorize that the same might be true of the similar trans-cortical vessels in humans.
At the same time preliminary observations dictate that human bone does not appear to have as many of these capillaries as they found in mice. While we do not quite understand if the number is important, the researchers theorize that this system could serve to explain how immune cells can appear so quickly in the bloodstream. More importantly, though, they know this is only the beginning of perhaps the most important anatomical discovery in the past several decades.