Our organs consist of a variety of specific proteins that are vital for providing energy to the organs, helping the immune system fight infections, and facilitating communication between cells. They are essential for the body to function normally. Proteins leak into the blood as part of normal turnover, which can accelerate during disease. However, it has been unclear from which organs or cells these proteins originate. Now, researchers at Lund University, in collaboration with Skåne University Hospital, have mapped cellular and organ-specific proteins in 18 of the body's most vascularized organs, as well as in eight of our most common blood cells.
"All of these 18 organs have specific protein 'fingerprints' in the blood even under normal circumstances, but in the event of organ damage or disease, the composition of proteins changes, thus reflecting the organ's health status", says Erik Malmström, researcher at the Department of Infectious Medicine, Lund University, and a resident physician in emergency medicine at Skåne University Hospital.
By developing a special algorithm, the researchers can determine which proteins are specifically expressed in one or more organs, which they have then compiled into an atlas of where proteins are produced in the body. Using this atlas, they can measure how these organ-specific proteins change in the blood during injury or disease. This provides new insights into how each cell and tissue organizes its set of proteins, which is important for developing new biomarkers.
From just a single drop of blood, we can analyze thousands of proteins simultaneously through mass spectrometry — both identifying the different types and quantifying their concentration. Previous studies have mapped proteins from various organs, but we have gone a step further by examining whether these proteins decrease or increase in concentration in plasma during pathological events. We are the first to do this, says Johan Malmström, professor at the Department of Infectious Medicine, Lund University.
For some conditions, methods already exist to measure proteins in the blood and thus understand whether a specific organ has been affected by injury or disease. For example, during a heart attack, the heart releases the protein troponin, allowing a simple blood test to make the correct diagnosis. For suspected diabetes, a blood sugar marker is used.
"But we need more specific biomarkers to measure the health status of all our organs", says Erik Malmström.
At the emergency department at Skåne University Hospital, where he works, there is a high patient flow with varying diseases of different severity and complex conditions, requiring more reliable diagnostic methods. Erik Malmström believes that the new method could be a step toward understanding disease changes and providing healthcare with better diagnostic tools. For certain systemic or inflammatory diseases that affect multiple cell types and organs, such as sepsis, there is currently no single biomarker that can sensitively diagnose the disease. The next step is, therefore, to investigate how proteins in the blood change during sepsis, as it is a condition that is often difficult to diagnose.
"A prerequisite for our research is the close collaboration between the university and the hospital, where Emma Nimeus played an instrumental role. Without it, this type of research would not have been possible", concludes Erik Malmström.