“Tattooing” the heart with tiny implantable oxygen sensors is just one of dozens of concepts being presented by scientists during an international conference hosted by The Ohio State University College of Medicine and Public Health during last Fall.
The conference, attracting researchers from as far away as Russia, Israel and Australia, will present a survey of recent advances in the use of electron paramagnetic resonance (EPR) imaging technology to monitor complex biological systems related to cancer, heart attack and stroke, inflammatory diseases and wound healing.
EPR technology detects and images free radicals, which also are called highly reactive species. Free radical generation is related to biological stress, and the presence of free radicals is connected to a cascade of reactions that typically lead to tissue damage and cell death, which are associated with numerous diseases and aging.
Medical researchers in Ohio State’s Davis Heart and Lung Research Institute, a co-host of the conference, are considered international leaders in EPR imaging technology, in part because OSU houses the largest number of instruments dedicated to this type of imaging.
“We have a wide array of systems capable of measurements in biological samples ranging from single cells to large animals, including humans,” said Dr. Periannan Kuppusamy, director of the Center for Biomedical EPR Spectroscopy and Imaging at OSU and chair of the conference.
Ohio State-based research using EPR technology is led by Kuppusamy and Dr. Jay Zweier, director of the Davis Heart and Lung Research Institute (DHLRI) and vice chair of the conference. The two have amassed a large body of work derived from EPR imaging studies, most recently publishing a paper in the journal Circulation that provided the first measurements of the amount of oxygen in the heart muscle in a living animal using implantable oxygen-sensing probes that can be “read” by EPR instrumentation.
Kuppusamy likens such a probe to a tattoo on the heart – a particle-based marker that does no damage, but is visible – in this case, by EPR – for detection of its location.
In the recently published study, OSU researchers used the technique on mice, combining the probe and EPR instrumentation to observe specific characteristics of heart tissue damage related to cardiac arrest. The measurements demonstrated the critical role the molecule nitric oxide plays in regulating tissue damage that occurs during and after heart attack. Monitoring events that occur during reperfusion is a major component of EPR-based research in the Davis Heart and Lung Research Institute.
Ohio State’s work in measuring oxygen concentration within tissue sets DHLRI apart from other research institutes, Kuppusamy said. “What is unique about our capabilities is that our method enables us to make noninvasive and repeated measurements of oxygen in the same tissue over a period of time, even weeks or months,” he said. The oxygen-sensing probes can be implanted in accessible tissue, which then allows for monitoring of oxygen concentration using the EPR instrumentation.
Such measurements, now used in animals but expected to be applicable in humans, someday may offer guidance on the optimum timing for radiation or chemotherapy treatments in cancer patients based on the oxygen concentration in a tumor. And scientists envision one day implanting probes in a closed human chest – placement of the heart tattoo – to monitor patients’ recovery after bypass surgery or heart transplantation.
Scientists also are looking at how free radicals are produced in the heart after blood flow has stopped and been restarted, hoping to determine how best to salvage the heart muscle and protect it from free radical-related injuries. The research relating to free radicals also factors into the development of antioxidant cardio-protective drugs.
Wound-healing research at OSU also benefits from the availability of EPR imaging and detection of oxygen concentration in wounds, contributing to the design of therapies related to oxygen needs of damaged tissue in chronic, hard-to-heal wounds. The final day of the EPR conference is being combined with an inaugural conference of OSU’s newly designated Comprehensive Wound Center. - By Ohio State University
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