Researchers study trauma response using near-infrared rays
SAN ANTONIO (May 5, 2009) — Texas researchers are using near-infrared light waves and a contrast agent to detect tiny leaks in rodents’ blood vessels, then track the blood as it pools in tissues. By viewing this damage as it occurs, the scientists seek to understand how to regenerate muscle tissue and save limbs after traumatic injuries, such as those occurring in soldiers injured by improvised explosive devices (IEDs) in Afghanistan and Iraq.
The project is being conducted at The University of Texas Health Science Center at San Antonio. Other Health Science Center researchers are assessing whether the same contrast agent, IR-820, can provide real-time information about how to limit the tissue area killed by strokes. Visualizing stroke injury in living animal models rather than by frozen sections after autopsy potentially may lead to better stroke diagnostics and therapies.
Technique could be used in humans
“Right now we are using IR-820 with near-infrared spectroscopy in mice, but it is a technique that could be taken to humans,” said Paula K. Shireman, M.D., associate professor of surgery at the Health Science Center and co-author of an article on IR-820’s utility in the journal Molecular Imaging. “This type of spectroscopy could be used like CT (computed tomography) or MRI (magnetic resonance imaging).”
On the electromagnetic spectrum, infrared rays fall between microwaves and visible light. Near-infrared waves, the shortest of the infrareds, are used in TV remote controls. These rays, which are closest in wavelength to visible light, penetrate tissue safely and with low scattering.
Vessel leaks, muscle damage can be measured
A key feature of IR-820 is its ability to bind to a blood protein called albumin. In trauma, blood vessels leak albumin into skeletal muscle, which can be a marker of damage or death of the muscle.
“In the IR-820 experiments, we are attempting to measure how much albumin leaves the vascular system and how robust the injured tissue’s capacity is to remove it,” Dr. Shireman said. “We are looking to see if the vascular system is not leaky anymore and whether there is regeneration of muscle.”
Studies with impaired mice are on the horizon
The journal article describes IR-820 imaging experiments in normal, healthy mice. The next step is to repeat the experiments in mice with impaired muscle regeneration capacity.
Possible method to assess post-stroke therapies
Another article co-author, James Lechleiter, Ph.D., professor of cellular and structural biology at the Health Science Center, said the goal of the mouse stroke model project is to find ways to lessen the effects of strokes and promote recovery. After a stroke, brain cells are killed progressively over several days due to a lack of oxygen, radiating from the site of the blockage outward, much like the ripple effect of a stone dropped into a pond.
“We are in the early stages of study, but it looks like we can use near-infrared spectroscopy with IR-820 to evaluate different neuro-protective agents to see how they might limit stroke damage,” Dr. Lechleiter said. “We will be able to follow the events in our mice as they happen, which is a much more efficient way to study stroke.”
The authors, who are from the Greehey Children’s Cancer Research Institute at the Health Science Center, the South Texas Veterans Health Care System, and the university’s departments of surgery, cellular and structural biology, pathology, periodontics, medicine, pediatrics, and epidemiology and biostatistics, are Suresh Prajapati; Carlo Martinez, M.D., M.S.; Ali Bahadur; Isabel Wu; Wei Zheng; James Lechleiter, Ph.D.; Linda McManus, Ph.D.; Gary Chisholm, M.S.; Joel Michalek, Ph.D.; Paula Shireman,M.D., and Charles Keller, M.D.
The University of Texas Health Science Center at San Antonio is the leading research institution in South Texas and one of the major health sciences universities in the world. With an operating budget of $668 million, the Health Science Center is the chief catalyst for the $16.3 billion biosciences and health care sector in San Antonio’s economy. The Health Science Center has had an estimated $36 billion impact on the region since inception and has expanded to six campuses in San Antonio, Laredo, Harlingen and Edinburg. More than 26,000 graduates (physicians, dentists, nurses, scientists and other health professionals) serve in their fields, including many in Texas. Health Science Center faculty are international leaders in cancer, cardiovascular disease, diabetes, aging, stroke prevention, kidney disease, orthopaedics, research imaging, transplant surgery, psychiatry and clinical neurosciences, pain management, genetics, nursing, dentistry and many other fields. For more information, visit www.uthscsa.edu.
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