Morphometric study of proximal tubular cell mitochondria using TEM images in renal diseases

The kidney is rich in mitochondria, and any alterations or damage to tubular cell mitochondria play an important role in renal metabolic activities and the pathogenesis of various kidney diseases. Quantitative analysis of mitochondrial concentration, size, and shape is essential for understanding mitochondrial biology in renal disorders. This study assessed mitochondrial morphometric parameters of the proximal convoluted tubular cell adjacent to the glomerulus in different renal disorders and investigated how they correlated with serum creatinine. A total of 65 kidney biopsy cases received by the transmission electron microscope (TEM) laboratory for diagnosis were included in the study. TEM images of glutaraldehyde-osmium tetroxide fixed epoxy-resin embedded 70 nm thick sections were used for the evaluation of (i) minor axis(MinX) (ii) major axis(MajX) (iii) Area, (iv)Perimeter, (v) Aspect ratio and (vi) Roundness of mitochondria in renal tubular cells using QuPath software. Mitochondrial density (MDensity), % of mitochondrial space (MSpace), and mitochondrial surface density (MSDensity) in the cytoplasm of tubular space were estimated for each sample. Serum creatinine showed good negative correlations with MSpace and MSDensity, and elongation of mitochondria was more in renal disorder in comparison to normal histology, which indicated the variation of mitochondrial concentration and shape in proximal tubular cells could be important features in the renal function disorder.