Sickle blood cells can block the filter of the spleen, leading to potentially life-threatening conditions. Researchers from Massachusetts Institute of Technology, Nanyang Polytechnic University of Singapore, Pasteur Institute of France and other institutions have designed a microfluidic device, namely "spleen chip", which can simulate how the phenomenon of acute spleen isolation occurs. The paper was published in the latest issue of the Proceedings of the National Academy of Sciences. Researchers found that low oxygen levels are more likely to block the spleen filter, and increasing oxygen levels can unblock the filter, which may help explain how blood transfusion can help patients with sickle cell disease. The life span of most red blood cells is about 120 days, so nearly 1% of the supply must be removed every day. In the spleen, blood flows through the red pulp tissue, which contains a narrow channel called the gap between the endothelium. These gaps are formed by gaps arranged between splenic vascular endothelial cells, and their maximum opening size is significantly smaller than that of red blood cells. Any red blood cells that cannot pass through these tiny openings due to damage, rigidity or deformity will be trapped and destroyed by macrophages. In order to simulate the filtration function of the spleen, researchers created a microfluidic device with two modules, namely, the S chip simulating the gap between the endothelium and the M chip simulating the macrophage. The device also includes a gas channel, which can be used to control the oxygen concentration of each chip to simulate the conditions in the human body. The researchers used healthy red blood cells and sickle red blood cells from sickle cell disease patients to study, allowing these cells to flow through their equipment under the control of oxygen levels. The study found that under normal oxygen conditions (20% oxygen), sickle cells caused some blockage at the gap, but there was still room for other blood cells to pass through. However, when the oxygen level drops to 2%, the gap will soon be completely blocked. When the researchers raised the oxygen level again, the blockage disappeared. (Outlook New Era)