Real-Time Imaging of Stroke Models Employing Two-Photon Excited Florescence Microscopy

One of the major hurdles to understanding how brain cells die during a stroke and identifying new ways to protect them has been the long-standing inability to image strokes, (ischemic events) in living tissue. Now researchers have developed methods to trigger strokes in animal models and image the events as they unfold.

"We can see the dynamics of interaction,” Cornel University (Ithaca, NY, USA) research associate Dr. Nozomi Nishimura said, adding that some neurons most likely die due to interactions with many different types of cells, including immune system cells, vascular cells, astrocytes, and glial cells. Dr. Nishimura and her colleagues visualize intercellular dynamics via two-photon excited fluorescence (2PEF) microscopy, which is able to image individual cells and capillaries. Employing relatively long wavelengths of light, she and her colleagues have succeeded in imaging at greater depths into tissue than has been possible to date.

Dr. Nishimura and her colleagues have also developed a method to induce localized lesions within rodent models. They adapted a technology, femtosecond laser ablation, typically used in micromachining of solid materials, for a novel biologic use. This ability to induce specific small lesions is particularly important to creating viable models in which to study the progression typical of dementia. According to Dr. Nishimura, it is becoming apparent that many older individuals suffering from dementia have experienced a series of microstrokes, triggering cumulative damage. "How is it that these small bleeds or blood clots affect neurons?” she asked, adding that the ability to introduce and then image microstrokes in a model system should shed light on how damage might best be mitigated.

The laser ablation system is also being examined for use in surgical manipulation and in examining tumor migration, specifically, how cells shed from tumors might also block blood vessels.

The study's findings were presented on October 26, 2010, at the Frontiers in Optics (FiO) 2010/Laser Science XXVI--the 94th annual meeting of the Optical Society (OSA), which was held together with the annual meeting of the American Physical Society (APS) Division of Laser Science in Rochester, NY, USA, from October 24-28, 2010.

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