Computational identification & 3D morphological characterization of renal glomeruli in optically cleared murine kidneys

Résumé :
Characterization of glomerulus structure is of critical importance to understand the pathophysiological involvements of the kidney in renal and systemic diseases such as cardiovascular dysfunction. The aim of our study was to establish an accessible methodology for the objective identification and three-dimensional morphological characterization of renal glomeruli in mice.

Experiments were done on 7 8-week-old female C57BL/6J mice. 3D imaging was performed in the renal cortex by light-sheet microscopy on iDISCO+ optical cleared kidneys after labeling of the capillary endothelium by lectin injection. 3D images were processed with the open-source software ImageJ. Non-visual image segmentation was made in three steps based, respectively, on (1) the frequency distribution of the voxel greyscale values, (2) the volume, and (3) the shape of the objects. Renal glomeruli were characterized by their numeric and volume densities, and the average and frequency distribution of their surface area, volume, and compactness (a normalized volume/surface ratio whose maximal value is 1 for a sphere).

The number of glomeruli was equal to 274 ± 41/mm3 of renal tissue, representing 1.73 ± 0.47 % of the tissue volume. The mean ± SD surface area, volume, and compactness were respectively equal to 21360 ± 5800 µm², 62810 ± 12650 µm3, and 0.064 ± 0.026.

The proposed standardized methodology is easily accessible for biologists. It provides the identification of the renal glomeruli and their 3D morphological characterization and allows statistical comparison between samples. It is hence useful for the study of renal functions and dysfunctions

Mots clés : renal glomeruli; optical clearing; light-sheet microscopy; 3D image processing; 3D morphological characterization

Auteurs : Nabil Nicolas, Nour Nicolas, Etienne Roux
Univ. Bordeaux, INSERM, Biologie des maladies cardiovasculaires, U1034, F-33600 Pessac, France, Pessac, France

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