Sex differences in podocyte density are largely due to sex differences in kidney size
Location
D.P. Culp Center Ballroom
Start Date
4-5-2024 9:00 AM
End Date
4-5-2024 11:30 AM
Poster Number
50
Name of Project's Faculty Sponsor
Aaron Polichnowski
Faculty Sponsor's Department
Biomedical Sciences
Competition Type
Competitive
Type
Poster Presentation
Presentation Category
Health
Abstract or Artist's Statement
Chronic kidney disease (CKD) affects over 15% of the adult population and is a leading cause of morbidity and mortality. Clinical studies have demonstrated that the rate of CKD progression is accelerated in males; however, the underlying mechanisms are poorly understood. Sex differences in podocyte density may contribute to the sex disparity in CKD progression. Podocytes are terminally differentiated visceral epithelial cells whose major role is to support the glomerular capillaries against relatively high filtration pressures. While kidney size is, on average, greater in males, which could impact the susceptibility to CKD progression by decreasing podocyte density, there is limited data regarding sex differences in podocyte density. Therefore, we tested the hypothesis that male rats would exhibit reduced podocyte density as compared to female rats. Sprague-Dawley rats (8-10-weeks-old, n=16 female; n=16 male) were subjected to either right uninephrectomy (UNX, n=8/sex) or sham UNX (i.e., intact kidneys, n=8/sex). Six weeks later, kidneys were perfusion-fixed, harvested, and paraffin-embedded. To assess podocyte density, kidney sections (5 um) were stained with a podocyte-specific primary antibody (Wilms Tumor 1 (WT-1), 1:60), a fluorescent secondary antibody (1:200), and DAPI (300nM) to identify nuclei. Merged WT-1/DAPI images of 20 randomly selected glomeruli per section were analyzed (CellSens) to determine glomerular tuft area, podocyte number, and podocyte diameter. Podocyte density was calculated as the number of podocytes/glomerular tuft volume. A 2-way-ANOVA with Holm-Sidak post hoc analysis was used to assess differences among groups. Linear regression analysis was used to assess the relationship between glomerular tuft volume and podocyte density and diameter. All data are reported as mean ± standard error and P<0.05 was considered statistically significant. Body weight was 59% greater (P<0.05) in male vs. female rats within both intact and UNX groups, but there were no significant differences between intact and UNX groups within each sex. Absolute kidney weight was 57% greater (P<0.05) in male vs. female rats and 59% greater (P<0.05) in UNX vs. intact groups within sexes. Glomerular tuft volume was 25% greater (P<0.05) in male vs. female rats and 22% greater (P<0.05) in UNX vs. intact groups within sexes. Podocyte number per glomerular tuft was not significantly different between male vs. female rats or between intact vs. UNX groups within each sex. Podocyte density was 12% less (P<0.05) in male vs. female rats and 20% less (P<0.05) in UNX vs. intact groups within each sex. Linear regression analysis revealed that 56% of the variability in podocyte density as well as podocyte diameter was explained by variability in glomerular tuft volume (P<0.0001). In conclusion, sex differences in podocyte density are largely dependent on sex differences in kidney weight and glomerular tuft volume. The well-known sex differences in kidney weight in clinical populations may therefore contribute to the sex disparity in susceptibility to hypertensive renal injury and rate of CKD progression. Future studies are planned to examine the effects of manipulating kidney weight and podocyte density within sexes on the susceptibility to hypertensive renal injury.
Sex differences in podocyte density are largely due to sex differences in kidney size
D.P. Culp Center Ballroom
Chronic kidney disease (CKD) affects over 15% of the adult population and is a leading cause of morbidity and mortality. Clinical studies have demonstrated that the rate of CKD progression is accelerated in males; however, the underlying mechanisms are poorly understood. Sex differences in podocyte density may contribute to the sex disparity in CKD progression. Podocytes are terminally differentiated visceral epithelial cells whose major role is to support the glomerular capillaries against relatively high filtration pressures. While kidney size is, on average, greater in males, which could impact the susceptibility to CKD progression by decreasing podocyte density, there is limited data regarding sex differences in podocyte density. Therefore, we tested the hypothesis that male rats would exhibit reduced podocyte density as compared to female rats. Sprague-Dawley rats (8-10-weeks-old, n=16 female; n=16 male) were subjected to either right uninephrectomy (UNX, n=8/sex) or sham UNX (i.e., intact kidneys, n=8/sex). Six weeks later, kidneys were perfusion-fixed, harvested, and paraffin-embedded. To assess podocyte density, kidney sections (5 um) were stained with a podocyte-specific primary antibody (Wilms Tumor 1 (WT-1), 1:60), a fluorescent secondary antibody (1:200), and DAPI (300nM) to identify nuclei. Merged WT-1/DAPI images of 20 randomly selected glomeruli per section were analyzed (CellSens) to determine glomerular tuft area, podocyte number, and podocyte diameter. Podocyte density was calculated as the number of podocytes/glomerular tuft volume. A 2-way-ANOVA with Holm-Sidak post hoc analysis was used to assess differences among groups. Linear regression analysis was used to assess the relationship between glomerular tuft volume and podocyte density and diameter. All data are reported as mean ± standard error and P<0.05 was considered statistically significant. Body weight was 59% greater (P<0.05) in male vs. female rats within both intact and UNX groups, but there were no significant differences between intact and UNX groups within each sex. Absolute kidney weight was 57% greater (P<0.05) in male vs. female rats and 59% greater (P<0.05) in UNX vs. intact groups within sexes. Glomerular tuft volume was 25% greater (P<0.05) in male vs. female rats and 22% greater (P<0.05) in UNX vs. intact groups within sexes. Podocyte number per glomerular tuft was not significantly different between male vs. female rats or between intact vs. UNX groups within each sex. Podocyte density was 12% less (P<0.05) in male vs. female rats and 20% less (P<0.05) in UNX vs. intact groups within each sex. Linear regression analysis revealed that 56% of the variability in podocyte density as well as podocyte diameter was explained by variability in glomerular tuft volume (P<0.0001). In conclusion, sex differences in podocyte density are largely dependent on sex differences in kidney weight and glomerular tuft volume. The well-known sex differences in kidney weight in clinical populations may therefore contribute to the sex disparity in susceptibility to hypertensive renal injury and rate of CKD progression. Future studies are planned to examine the effects of manipulating kidney weight and podocyte density within sexes on the susceptibility to hypertensive renal injury.