Prior to this discovery, it was believed that new blood vessels developed from existing blood vessels or progenitor cells.

A peer-reviewed study from the Weizmann Institute of Science published in Nature on Wednesday demonstrates that blood vessels can emerge from lymphatic vessels.

Until now, new blood vessels were assumed to develop from either other blood vessels or progenitor cells, which are stem cell descendants. This third source, lymphatic vessels, was discovered in genetically modified zebrafish whose cells were labeled with fluorescent markers to allow tracing.

Dr. Rudra N. Das, a postdoctoral fellow in Weizmann’s Immunology and Regenerative Biology Department, explained, “It was known that blood vessels can give rise to lymphatic vessels, but we’ve shown for the first time that the reverse process can also take place in the course of normal development and growth.”

Das discovered lymphatic veins emerged before the bones did in young zebrafish fins while studying their growth. Some of these lymphatic veins later evolved into blood vessels, losing their distinguishing traits.

Why didn’t the blood vessels in the fins just grow from a big blood vessel nearby?

Analyzing mutant zebrafish lacking lymphatic vessels, the team discovered that blood vessels in the fins did indeed branch off from existing blood vessels. However, the fins would grow improperly, resulting in skeletal malformations and internal hemorrhage. Furthermore, an abnormally large number of red blood cells, which carry oxygen, surged into the newly constructed blood vessels. In the normal fish, the red blood cells could not get in.

“We found that blood vessels must derive from the right source in order to function properly – it’s as if they remember where they came from,” study leader Prof. Karina Yaniv remarked.

The restricted presence of red blood cells manifested as low-oxygen circumstances favorable to bone growth.

Is this important for human growth?

The findings of the study are likely to apply to other animals, including humans.

“In past studies, whatever we discovered in fish was usually shown to be true for mammals as well,” added researcher Karina Yaniv.

These findings may pave the way for future studies in the field of human development. They could, for example, shed light on the function of the human placenta’s particular arrangement of blood arteries, which generates a low-oxygen environment for embryo development. The findings of the study could lead to new discoveries in the fields of heart disease and cardiovascular health; doctors may be able to better treat heart attacks if they have a better understanding of the heart’s coronary veins.

“On a more general level, we’ve demonstrated a link between the ‘biography’ of a blood vessel cell and its function in the adult organism,” Yaniv concluded. “We’ve shown that a cell’s identity is shaped not only by its place of ‘residence,’ or the kinds of signals it receives from surrounding tissue, but also by the identity of its ‘parents’.”

Image Credit: Getty

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