When the human body suffers an injury, the response is swift and universal. Many different types of cells immediately are released into the blood stream and directed at the wound in order to seal the wound. One of these types of cells is called a macrophage. Greek for “big eaters,” these are white blood cells within tissues that initiate specific defense mechanisms as well as act as general defenders by enveloping and destroying debris and foreign invaders.
The presence of these necessary miniature surgeons is one of the reasons our body is so good at repairing itself. However, there are instances when the little guys do more harm than good.
One of these instances is in a spinal cord injury. Spinal cords are specialized tissue confined in an extremely delicate space and when these cells show up en masse, the inflammatory response causes tissue and blood vessels to essentially be ripped apart, forming a traumatic wound.
These macrophages come from different sources, including the spinal cord itself. Scientists believe these “resident” macrophages do more good than harm. However, new research from the Ohio State University’s Phil Popovich identifies the spleen as the culprit of at least some of the most damaging “rescuers.”
Researchers removed the spleen from one group of mice while leaving it in another. They then inflicted a spinal cord injury in the T-9 region, essentially the middle of their backs. The mice without spleens saw a 20 percent drop in the number of macrophages released into the blood stream compared to those with spleens intact. The fact that these missing cells were due to the spleen’s removal was confirmed by the analysis of the characteristics of the cells in the bone marrow, blood spleen and spinal cord. Because the excess cells in the mice with spleens were very similar to those of the spleen, the researchers concluded it must be where the missing cells would have been made.
Assuming these results translate to humans, the discovery could be an important step in mitigating the damage in the wake of a spinal cord injury. Especially seeing as the spleen is an excellent drug target because it filters blood, making intravenous drug delivery easy and effective. If future research can show a way to turn off the spleen’s production of these cells, or to alter their structures and functions, patients may be able to make a fuller recovery from these paralyzing injuries.