Imaging immune response in breathing lung

As with toddlers, tissues that are constantly in motion can be difficult to capture in still images without at least a little blurring. But researchers have developed a method of stabilization for living lung tissue that allows more precise imaging without disrupting the organ’s normal function.

Neutrophils (green) are visualized moving through alveolar capillaries marked with Texas Red dextran (red) under baseline conditions. Images courtesy of E. Thornton and M. Looney, UCSF.

Thanks to the new method, the team was able for the first time to observe both the real-time interaction of live cells in their natural habitat, so to speak, and the sequence of events that makes up the immune response to lung injury.

“We figured out a method for holding cells still enough to image them without interrupting their normal processes,” said Max Krummel, associate professor of pathology at the University of California. “This enabled us to observe cellular events as they happen naturally rather than the usual way, which is to stop the motion of cellular processes in order to photograph them.”

Lung cells marked in the Actin-CFP transgenic mouse (green) are stabilized with an imaging window, and breathing artifacts are removed by averaging 15 video-rate frames.

In the technique, a custom rig device applies a gentle amount of suction to the surface of the tissue, the suction holds the viewing region in place within the range of the microscope, and then a two-photon microscope photographs the tissue. The researchers took footage 30 times per second to reveal, for example, which cells worked together in response to an injury. They used this information to identify the functions of different cell types.

The team plans to work on miniaturizing the stabilizing rig to provide imaging for live tissue biopsies. The research was published online Dec. 12, 2010, in Nature Methods (Vol. 8, pp. 91-96, 2011).