case western reserve university

Page Expired


The page you are attempting to view may be out-of-date.

The page in question has not been verified by its author in quite some time.

If the information provided on the page is time sensitive, it is possible that it is no longer accurate. To ensure that you receive the most current information, we recommend you contact the page's author. He or she can verify whether the information is correct and/or direct you to a more up-to-date page.

Continue to the requested page.

estion, Dr. Simon and his team looked at the entire genome using a process called transcriptional profiling. While treating a patient for heart attack in the hospital, researchers drew their blood and compared it with samples from patients with stable angina. They examined mRNA , which contains the blueprint for making proteins, for all of a person's 30,000 or so genes.

Researchers were challenged to analyze the blood in a way that could discern which differences they found preceded the heart attack and did not result from it. "It's a chicken-and egg problem. Which came first?" Dr. Simon explains. The team chose to examine platelets-fragments of bone marrow cells called megakaryocytes that break off and enter the bloodstream and, significantly, have no DNA -housing nucleus. The signs of gene expression are frozen in time during the 7- to 10-day lifespan of the platelets, earning them Dr. Simon's designation as "nature's time capsules."

Theirs is the first published report of platelet profiling in human health or disease; since then, the method has been applied in sickle cell disease research. The scientists dubbed their platelet-based approach the "Lois Lane-Superman phenomenon" because the pre-heart attack biological state is reflected in post-heart attack blood. In Dr. Simon's words, "By sampling the platelets, we can turn back time-just like Superman before Lois Lane dies in the crash-and look at gene expression in the days and hours before the heart attack."

By collaborating on the transcriptional profiling with Millennium Pharmaceuticals, Dr. Simon and his academic colleagues from Harvard were able to leverage the company's personalized medicine program; in particular, the research benefited from a high-fidelity amplification method used to make crucial health observations, such as distinguishing high-risk from low-risk tumors. The approach-a method "as mindbogglingly complex and expensive as it is powerful," as Dr. Simon describes it-magnified the number of molecules so that a small amount of blood taken from each patient sufficed for analysis that would normally require 1,000 times that amount.

Mukesh Jain, MD, came from Harvard to become the Ellery Sedgwick Jr. Chair and Distinguished Scientist and director of the Case Cardiovascular Research Institute at the School of Medicine. He describes himself as "consultant and sounding board" on the MRP-8/14 research, and says, "The partnership is an extraordinary example of how bright people from industry and academia can collaborate to play up their respective research strengths."

Heart Attack Ahead?

As detailed in the May 16, 2006, issue of the journal Circulation, the transcriptional profiling project bore encouraging fruit in the form of 59 differences spotted between the platelets of those with heart attack and those with stable coronary disease. It identifies the disparity with the greatest promise for further scientific study as the protein MRP-14-which is bonded with its sister molecule MRP-8 and so is studied in its MRP-8/14 combination state.

MRP-8/14 was the most abundant protein found inside infection-fighting cells called neutrophils. Neutrophils play a starring role in acute inflammation-a process that scientists today understand as a considerable contributor to atherosclerosis and heart attack-and are the cells associated with plaque ruptures seen in autopsies after death from heart attack.

Dr. Simon and his team knew from examining platelets that MRP-8/14 was present in patients' blood in relatively high levels before their heart attack. This suggested the protein might serve as a prompt indicator of which people sensing an elephant on their chest were having an actual heart attack. What they still did not know, however, was how far in advance of the coronary calamity that elevated levels of MRP-8/14 appeared. Does the protein lurk inside apparently healthy people, even years before a heart attack occurs? In that case, tracking MRP-8/14 levels-which can be measured in the plasma with a simple blood test-could prove to be an enormously powerful tool in heart attack prediction for the general population.

For a prospective validation study that would elucidate the timeline, the researchers were granted access to scientifically precious blood from the Women's Health Study-a renowned cardiovascular disease prevention study during which blood from more than 28,000 apparently healthy women was collected and frozen. Over the years following the blood collection, some of the women had a heart attack or stroke, while others did not.

In those women who went on to have heart attacks, Dr. Simon's group found the expected elevated cholesterol levels, high blood pressure and other accepted risk indicators. Notably, women who went on to have MIs also had much higher levels of the study's protein of interest, MRP-8/14, in their blood when they were seemingly healthy. This served as the hoped-for validation of the compound's predictive potential. Abnormally elevated levels of MRP-8/14 were associated with a more than doubled heart attack risk, a more significant association than even LDL cholesterol.

Cholesterol testing is known to be a meritorious, but by no means foolproof, method to appraise cardiovascular risk. "We know that many people with modest cholesterol levels are at relatively high risk, while those with high levels can be at pretty low risk," says Carl Orringer, MD, the Harrington-McLaughlin Chair in Preventive Cardiovascular Medicine at the School of Medicine and director of preventive cardiovascular medicine at University Hospitals Case Medical Center. MRP-8/14 has been compared with the "gold standard" biomarker C-reactive protein (CRP) as a possible partner with cholesterol and other measures to help predict cardiovascular events, including heart attack.

Studies in Mice and Men

The research team was not content to stop at their breakthrough finding of MRP-8/14's association with heart disease. Dr. Simon went back to the laboratory-this time as a faculty member of the School of Medicine-and created a pertinent mouse model to study whether MRP-8/14 played a fundamental role in the vascular inflammation involved in atherosclerosis. "As physician-scientists, these researchers committed to bridging the clinical and scientific observations: 'Let's go back to the bench to understand how this works,'" Dr. Jain says.

The first step in the research, published in the August 4, 2009, issue of Circulation: Create a mouse with raging atherosclerosis by feeding it a high-fat diet. Step two: Delete a gene involved in cholesterol metabolism. Finally: Cross this mouse with one engineered without its MRP-8/14 gene.

This way, the scientists were poised to examine the gene's role in vascular inflammation. Finding significantly less inflammation in the custom-designed mouse-the one missing MRP-8/14-the researchers were able to conclude that the protein plays a fundamental role in vessel wall inflammation. Says Kevin Croce, MD, PhD, an instructor of medicine at Harvard Medical School, adjunct assistant professor at Case Western Reserve, and first author on the study, "It's very powerful to go back-and-forth from test tubes, to mice, to patients. Both Dan [Simon] and I have the opportunity to work with patients every day, and it's incredibly exciting to find new targets in the lab that have real clinical promise."

Dr. Simon and his colleagues have turned their attention now to a crucial question of causation in thrombosis. "We know a person is prone to a heart attack if MRP-8/14 is present at a high level," he says. "We're trying to figure out now whether this is only a sign that a person is at risk for heart attack, or if it actually is the culprit." An upcoming paper will address whether MRP-8/14 influences the clotting that sets up a heart attack.

The research uses models with induced clots; if the time to clot is longer in a specimen whose MRP-8/14 gene has been removed than in a normal model, researchers will have their answer that MRP-8/14 plays a causational role in thrombosis.

The researchers also want to confirm whether MRP-8/14 predicts a second event in those who have established coronary disease. It seems predictive of a recurrence, based on a study published in the January 2008 American Heart Journal, and now the question must be studied in a larger number of patients. David A. Morrow, MD, MPH, a Harvard Medical School clinical cardiologist and lead author of the important recurrence study says of the ongoing collaboration among researchers from Harvard, Case Western Reserve and other distinguished research institutions, "I think this reflects the best of what academic centers have to offer in moving science forward from bench-top research to potential bedside application."

Another project is being designed by the remaining team of Brigham and Women's researchers together with Dr. Simon's School of Medicine group to compare MRP-8/14 head-to-head with other heart attack markers to better gauge what it might add to the existing field.

To be determined, ultimately, is whether medications can be developed that thwart any destructive power of MRP-8/14. Dr. Simon hopes this kind of drug will be available in 7 to 10 years. "We still have a lot to learn," acknowledges the physician-scientist, "but we view our glass as half-full. We didn't even know before that this protein might be involved in vascular inflammation and thrombosis, and in three short years we have all this dramatic information to build on."

In the near term, clinical trials are ongoing to gain approval from the Food and Drug Administration for quick-working MRP-8/14-based tests. European researchers have found MRP-8/14 to be the most sensitive and rapid predictor of heart attack for patients in the emergency room-substantiating an MI in a matter of minutes, not hours like a traditional test that tracks the substance troponin slowly leaking into the bloodstream. Dr. Simon estimates that MRP-8/14 tests could be widely available within two years, not only for use in the emergency room to confirm a heart attack, but also for routine testing in the physician's office to help avoid one.

Share bookmark or share