Structure and diversity of human dendritic spines evidenced by a new three-dimensional reconstruction procedure for Golgi staining and light microscopy.

Background: Different approaches aim to unravel detailed morphological features of neural cells. Dendritic spines are multifunctional units that reflect cellular connectivity, synaptic strength and plasticity.

New Method: A novel three-dimensional (3D) reconstruction procedure is introduced for visualization of dendritic spines from human postmortem brain tissue using brightfield microscopy. The segmentation model was based on thresholding the intensity values of the dendritic spine image along 'z' stacks. We used median filtering and removed false positives. Fine adjustments during image processing confirmed that the reconstructed image of the spines corresponded to the actual original data.

Results: Examples are shown for the cortical amygdaloid nucleus and the CA3 hippocampal area. Structure of spine heads and necks was evaluated at different angles. Our 3D reconstruction images display dendritic spines either isolated or in clusters, in a continuum of shapes and sizes, from simple to more elaborated forms, including the presence of spinule and complex 'thorny excrescences'.

Comparison With Existing Methods: The procedure has the advantages already described for the adapted "single-section" Golgi method, since it provides suitable results using human brains fixed in formalin for long time, is relatively easy, requires minimal equipment, and uses an algorithm for 3D reconstruction that provides high quality images and more precise morphological data.

Conclusion: The procedure described here allows the reliable visualization and study of human dendritic spines with broad applications for normal controls and pathological studies.