Expansion microscopy method targets human brain pathology

A new variant of expansion microscopy that is tailored for brain pathology samples reveals cells and structures that can’t be seen with other methods.

Expansion microscopy is a way of achieving the equivalent of superresolution with an ordinary diffraction-limited optical microscope. Fluorescently labeled tissue samples are embedded in a gel, treated with an enzyme that digests the proteins, and expanded. The expansion, which occurs equally in all directions, pulls the proteins apart while keeping them in the same positions relative to one another.

Edward S. Boyden of the Massachusetts Institute of Technology, E. Antonio Chiocca of Harvard Medical School, and coworkers call their new expansion microscopy variant decrowding expansion pathology, or dExPath (Sci. Transl. Med. 2024, DOI: 10.1126/scitranslmed.abo0049). In dExPath, instead of digesting the proteins, the researchers’ process uses a softening buffer that keeps the proteins intact. An initial partial expansion begins the process of separating the proteins. Because the proteins are still intact, they can be labeled with fluorescently labeled antibodies after the decrowding step, which results in improved labeling density and image quality.

The researchers used dExPath to do multiplexed imaging of various human brain pathology samples, including ones from patients with glioma, Alzheimer’s disease, and Parkinson’s disease. “After decrowding, we could observe cell populations or structures that were previously undetected using conventional immunostaining,” Boyden writes in an email. “This process of staining can be done many times on the same tissue to visualize many markers on the same tissue.”