Credit: Daniel Gay
The longer blood is stored, the less it is able to carry oxygen into the tiny microcapillaries of the body, according to a study published in Scientific Reports.
Using advanced optical techniques, researchers measured the stiffness of the membrane surrounding red blood cells.
They found that, even though the cells retain their shape and hemoglobin content, the membranes get stiffer over time, which steadily decreases the cells’ functionality.
“Our results show some surprising facts: Even though the blood looks good on the surface, its functionality is degrading steadily with time,” said study author Gabriel Popescu, PhD, of the University of Illinois at Urbana-Champaign.
Dr Popescu and his colleagues wanted to measure changes in red blood cells over time to help determine what effect older blood could have on a patient.
They used an optical technique called spatial light interference microscopy (SLIM), which was developed in Dr Popescu’s lab in 2011. It uses light to noninvasively measure cell mass and topology with nanoscale accuracy. Through software and hardware advances, the SLIM system today acquires images almost 100 times faster than it did 3 years ago.
The researchers took time-lapse images of red blood cells, measuring and charting their properties. In particular, the team was able to measure nanometer-scale motions of the cell membrane, which are indicative of the cell’s stiffness and function. The fainter the membrane motion, the less functional the cell.
The measurements revealed that a lot of characteristics stay the same over time. The cells retain their shape, mass, and hemoglobin content, for example.
However, the membranes become stiffer and less elastic as time passes. This is important because the cells need to be flexible enough to travel through tiny capillaries and permeable enough for oxygen to pass through.
“In microcirculation, such as that in the brain, cells need to squeeze though very narrow capillaries to carry oxygen,” said study author Basanta Bhaduri, PhD, of the University of Illinois at Urbana-Champaign.
“If they are not deformable enough, the oxygen transport is impeded to that particular organ, and major clinical problems may arise. This is the reason why new red blood cells are produced continuously by the bone marrow, such that no cells older than 100 days or so exist in our circulation.”
The researchers hope the SLIM imaging method will be used clinically to monitor stored blood before it is given to patients, since conventional white-light microscopes can be easily adapted for SLIM with a few extra components.
“These results can have a wide variety of clinical applications,” said author Krishna Tangella, MD, of the University of Illinois at Urbana-Champaign.
“Functional data from red blood cells would help physicians determine when to give red cell transfusions for patients with anemia. This study may help better utilization of red cell transfusions, which will not only decrease healthcare costs but also increase the quality of care.”
