Protein Semaphorin 3A Helps to Detect Acute Kidney Injury

Acute kidney injury, a common and serious complication of hospitalization, is on the increase worldwide, and reports indicate that guidance cues that form the organ may also be associated with red flags that point out danger.

According to recent data, this problem affects an estimated 6 percent of all hospitalized patients at 30 to 40 percent of adults. This also includes children who have cardiopulmonary bypass surgery.

About 10 to 15 percent of acute injuries translate to chronic kidney damage or failure that may require dialysis or a kidney transplant, according to Dr. Ganesan Ramesh, kidney pathologist in the Vascular Biology Center at the Medical College of Georgia at Georgia Regents University.

Both animal and human studies have shown that within a few hours of injury, a significant amount of protein called semaphoring 3A is detectable in urine.

"Semaphorin 3A appears to be a sensitive biomarker that we believe will give physicians an early and accurate heads-up that their patient's kidneys have been injured so that damage can be minimized and potentially reversed with rapid intervention," said Ramesh, the study's corresponding author.

The protein, which is not usually measurable in urine, was quickly detected in a group of 60 pediatric patients following cardiopulmonary bypass surgery at Cincinnati's Children's Hospital. High levels of the protein were about 90 percent accurate at identifying the 26 children with acute kidney injury. In those patients, urine levels were high within two hours, peaked at six hours and essentially normalized 12 hours after surgery.

Researchers believe this may be caused due to the kidney's significant reserve capacity, as in a 48 hour period, a byproduct of muscle metabolism is typically excreted by the kidneys and is elevated in the blood.

The study of 60 children watched creatinine levels over a 24 hour period, which stayed relatively the same. However, by 48 hurs, levels were significantly elevated in the acute kidney injury group for a period of five days. The researchers initially identified semaphorin 3A in an animal model of temporarily compromised oxygen levels, or ischemia, to the kidneys, and when they eliminated the protein's expression in a mouse, it reduced ischemia-related kidney damage.

However, reports show that many unknowns persist about semaphorin 3A, including the role of the guidance cue in the healthy developed kidney and why it's levels shoot up then drop down so dramatically with injury.