Pregnancy associated plasma protein-A (PAPP-A) is not a marker of the vulnerable atherosclerotic plaque

Objective: To investigate if pregnancy associated plasma protein-A (PAPP-A) was present in the vulnerable plaque, and if not, to find alternative hypothesis for the release of PAPP-A. Design and methods: Vulnerable plaques and control tissues were examined by immunohistochemistry. Volunteers and patients with non-atherosclerotic disease were examined for release of PAPP-A during ischemia and medical treatment. Non-atherosclerotic tissue samples were examined after incubation with heparins. Results: We were not able to detect PAPP-A in vulnerable plaques. Patients and volunteers experiencing ischemic events without atherosclerotic lesions only had elevated PAPP-A when treated with heparin. When tissue from normal artery wall was incubated with heparin, PAPP-A was eluted. This was not the case for non-arterial tissue samples. Conclusion: Elevation of PAPP-A in patients with acute coronary syndromes seems to be caused by heparin induced release of PAPP-A from the arterial wall and not due to excretion from vulnerable plaques.