New Discovery about Haemoglobin
Context:
- For many years, textbooks have claimed that haemoglobin, which is present in red blood cells (RBCs), is what gives blood its red colour, delivers oxygen, and is vital to human survival.
“Hormone bodies”:
- There is more than only red blood cells that use haemoglobin, according to a recent and coincidental finding. Chinese researchers found that chondrocytes, the cells that form the cartilage that connects bones, also produce haemoglobin and appear to be dependent on it for survival in a study that was published in Nature. Since 2010, Chinese pathologist Feng Zhang has focused on the formation of bones.
- He discovered a few spherical blob-like formations in 2017 while researching growth plates, which are cartilaginous tissues at the ends of some long bones that allow the bones to grow longer. They contained haemoglobin and had an amazing similarity to red blood cells.
- Imagine what happens when water and oil are combined: a process known as phase separation causes the oil to split into tiny globules. That also appeared to be the case with the cartilage’s chondrocytes. Dr. Zhang discovered that the chondrocytes in the growth plates of baby mice were not only creating a lot of haemoglobin, but it was also clumping together to create big, membrane-free blobs. These lumps were dubbed haemoglobin bodies, or Hedy, by the scientists.
What does the haemoglobin do:
- With the knowledge that chondrocytes were producing haemoglobin bodies, the question arose as to whether or not the Hedy was functional. The haemoglobin-producing gene was removed from mice that were genetically altered by the scientists in order to test this. These mice died as embryos and produced essentially no haemoglobin molecules. However, upon closer inspection of the growth plate cartilage tissue from these mice, it was discovered that the majority of the chondrocytes were dying.
- The same thing happened when the gene that produced haemoglobin in cartilage tissue was removed: the chondrocytes died. It was evident that Hedy was necessary for the survival of the chondrocytes.
A reserve of oxygen:
- They now knew that the chondrocytes experienced a form of low-oxygen stress due to the absence of haemoglobin. The next thing they wanted to investigate was how chondrocytes, both normal and hemoglobin-free, responded to low oxygen levels in their surroundings. The cells were then put to the test in a hypoxic, or low-oxygen, setting by the researchers. When haemoglobin was present, the cells appeared to release more oxygen. However, when haemoglobin was lacking, the chondrocytes began to degrade. This strengthened their suspicion that the chondrocytes’ haemoglobin was probably storing oxygen and delivering it to the cells when needed.
Way Forward:
- This work is significant because it dismantles preconceived notions about the relationship between skeletal biology and haematology and demonstrates how closely related these two disciplines are. The finding that cartilage contains functional haemoglobin raises the prospect that it may be involved in a few joint disorders. Defects in chondrocytes can lead to a variety of bone abnormalities. Researchers are hopeful that this finding may allow them to rethink the processes behind various joint disorders.
