X-ray Technique Visualizes Microscopic Structures in Brain

A novel X-ray imaging technique can be used to identify individual Purkinje cells in the cerebellum, according to a new study.

Researchers at the University of Basel (UB; Switzerland) and University Hospital of Basel (Switzerland) have developed a specific mathematical filter for use with X-ray phase tomography that can visualize a volume of up to 43 mm3 of human post mortem or biopsy brain samples in three dimensions (3D), with automatic cell feature quantification at isotropic resolution in a label-free manner. The researchers used synchrotron radiation to determine local phase shifts, which provided better contrast than conventional X-ray techniques that rely on the attenuation of X-rays.

Using the technique, they succeeded in setting a pixel size of 0.45 micrometers, a hundred times smaller than the diameter of a human hair. The researchers then demonstrated the method on the cerebellum, automatically identifying 5,000 Purkinje cells with an error of less than 5%, and determined that the local surface density was 165 cells per mm2, on average. They also used the 3D data to segment sub-cellular structures, including the dendritic tree and Purkinje cell nucleoli, without the need for dedicated staining. The study was published in the September 2016 issue of Scientific Reports.

“Detailed insight into the cellular structures of the cerebellum enables, for example, a better description of motor function, coordination, and balance regulation. Moreover, morphological changes due to disease such as neurodegeneration should become better recognized on the basis of the 3D imaging data,” concluded lead author Simone Hieber, PhD, of the UB department of biomedical engineering, and colleagues. “In combination with the specific software, this approach could contribute to a better understanding and treatment of neurodegenerative diseases.”

Purkinje cells are large neurons with many branching extensions that are found in the cortex of the cerebellum, and which play a fundamental role in controlling motor movement. They are characterized by cell bodies that are flask-like in shape, by numerous branching dendrites, and by a single long axon. Purkinje cells release gamma-aminobutyric acid (GABA), a neurotransmitter that inhibits transmission of nerve impulses, which allows the cells to regulate and coordinate motor movements. The cells were first discovered in 1837 by Czech physiologist Jan Evangelista Purkinje.

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