Comparison of Methods for Counting Cells in the Mouse Glomerulus

Abstract

Background: Researchers have long been interested in counting the number of cells within the glomerulus. Investigators using different techniques have yielded conflicting results. The most direct method is to count the cells in serial sections from the entire glomerulus. This Exhaustive Count method is not usually practical. The disector/fractionator method counts the number of cells in a fraction of sections. The total is estimated from the product of the cell count and the reciprocal of the fraction. The Weibel-Gomez method determines the density of cells per glomerulus, then multiplies this density by glomerular volume to obtain cell number. In this study, we compared the disector/fractionator and Weibel-Gomez methods to identify a practical alternative for the time-consuming Exhaustive Count method. Methods: Glomeruli from a normal mouse kidney were completely sectioned and images obtained. Appropriate images were used to count glomerular cell number using each method. Results: The Exhaustive Count method yielded 213 ± 22 (mean ± SD) cells/glomerulus vs. the disector/fractionator average of 211 ± 29 cells/glomerulus (p = 0.82). The Weibel-Gomez method average of 235 ± 26 cells/glomerulus was statistically different from the Exhaustive Count method (p = 0.003). Conclusion: The Weibel-Gomez produced a 10% overestimation, whereas the disector/fractionator method was unbiased and thus a good substitute for the Exhaustive Count method.