WASHINGTON, Sept. 3 (Xinhua) -- A new study from the Massachusetts Institute of Technology (MIT) revealed how one of the most common complications of sickle-cell disease arises with deformed red blood cells clumping together and blocking blood vessels.
The study published on Monday in the Proceedings of the National Academy of Sciences represented a step toward being able to predict when these events known as vaso-occlusive pain crises might occur.
"These painful crises are very much unpredictable. In a sense, we understand why they happen, but we don't have a good way to predict them yet," said Dao Ming, a principal research scientist in MIT's Department of Materials Science and Engineering and one of the senior authors of the study.
Patients with sickle cell disease have a single mutation in the gene that encodes hemoglobin, the protein that allows red blood cells to carry oxygen. The mutation tend to misshape red blood cells.
Instead of the characteristic disc shape, cells become sickle-shaped, especially in low-oxygen conditions.
Patients often suffer from anemia because the abnormal hemoglobin can not carry as much oxygen, as well as from vaso-occlusive pain crises.
The researchers built a specialized microfluidic system that mimics the post-capillary vessels, which carry deoxygenated blood away from the capillaries. These vessels, about 10 to 20 microns in diameter, are where vaso-occlusions are most likely to occur. The microfluidic system was designed to allow the researchers to control the oxygen level.
They found that when oxygen is very low, or under hypoxia, similar to what is seen in post-capillary vessels, sickle red cells are two to four times more likely to get stuck to the blood vessel walls than they are at normal oxygen levels.
When oxygen is low, hemoglobin inside the sickle cells forms stiff fibers that grow and push the cell membrane outward. These fibers also help the cells stick more firmly to the lining of the blood vessel, according to the study.
The researchers also found that in patients with sickle cell disease, immature red blood cells called reticulocytes are most likely to adhere to blood vessels.
These young sickle red cells, just released from bone marrow, carry more cell membrane surface area than mature red blood cells, allowing them to create more adhesion sites.
Since not all patients with sickle cell disease experience vaso-occlusion and the frequency of attacks can vary widely between patients, the MIT researchers hope that their findings may help them to devise a way to predict these crises for individual patients.
