The relationship of peritubular capillary density with glomerular volume and kidney function in living kidney donors

Abstract

Background: Peritubular capillary rarefaction plays an important role in the progression of chronic kidney disease. Little is known about the relation between peritubular capillary density, glomerular volume and filtration rate in the healthy kidney.

Methods: In this single-center study, we included 69 living kidney donors who donated between 2005 and 2008 and had representative renal biopsies available. In all donors, glomerular filtration rate was measured using ¹²⁵I-Iothalamate before donation and at five years after donation. Before donation, the increase in glomerular filtration rate after dopamine stimulation was measured. Glomerular volume and peritubular capillary density were determined in biopsies taken at the time of transplantation. Pearson's correlation coefficient and linear regression were used to assess relations between parameters.

Results: Mean donor age was 52 ± 11 years and mean measured glomerular filtration rate was 119 ± 22 mL/min before donation and 82 ± 15 mL/min at five years after donation. While peritubular capillary density (measured by either number of peritubular capillaries/50,000 μm² or number of peritubular capillaries/tubule) was not associated with measured glomerular filtration rate before or after donation, number of peritubular capillaries/tubule was associated with the increase in measured glomerular filtration rate after dopamine stimulation (St.β = 0.33, p = 0.004), and correlated positively with glomerular volume (R = 0.24, p = 0.047). Glomerular volume was associated with unstimulated measured glomerular filtration rate before donation (St.β = 0.31, p = 0.01) and at five years (St.β = 0.30, p = 0.01) after donation, independent of age.

Conclusions: In summary, peritubular capillary density was not related to unstimulated kidney function before or after kidney donation, in contrast to glomerular volume. However, number of peritubular capillaries/tubule correlated with the increase in glomerular filtration rate after dopamine stimulation in healthy kidneys, and with glomerular volume. These findings suggest that peritubular capillary density and glomerular volume differentially affect kidney function in healthy living kidney donors.

Keywords: Glomerular hypertrophy; Kidney biopsy; Kidney function; Living kidney donation; Peritubular capillary rarefaction.

Fig. 1

Representative examples of the microstructural measurements on biopsies. In Periodic acid-Schiff (PAS) stained sections (a and b) the area of cortex was delineated (a), and the area of the tuft of all individual non-sclerosed glomeruli (a and b). On CD34 stained sections (c–e) peritubular capillaries (PTCs) are accentuated. Tubuli (d) peritubular capillaries (e), were annotated manually. Scale bars: a 200 um; b–e 50 um

Fig. 2

Scatter plots of the morphometrical parameters with each other. A glomerular volume (x-axis) with PTC/tubule (y-axis), Pearson = 0.24, p = 0.047; B glomerular volume (x-axis) with tubular area (y-axis), Pearson = 0.26, p = 0.03; C glomerular volume (x-axis) with PTC/50,000 µm² (y-axis), Pearson = − 0.21, p = 0.08; D tubular area (y-axis) with PTC/tubule (x-axis), Pearson = 0.31, p = 0.01; E tubular area (y-axis) with PTC/50,000 µm² (x-axis), Pearson = 0.63, P < 0.001; F PTC/50,000 µm² (y-axis) with PTC/tubule (x-axis), Pearson = 0.05, p = 0.70. PTC/tubule: peritubular capillary per tubule; PTC/50,000 µm²: peritubular capillary per 50,000 µm²