Figure 4

Volumes from micro-XCT with varying mineral densities and for different volume fractions are shown in (a,b). Schematic of the MPC is shown at the bottom of ai and aii with proximal occluded tubules (dark streaks) and interstitial mineralization in the distal region (mineralized blocks). Micro-XCT of representative MPC with proximal intratubular and distal interstitial biomineralization is shown as a inset in top right corner of ai. Segmentation of intratubular and interstitial minerals and respective mineral densities (MD, mg/cc) and volume fractions (VF) in the MPC (ai, 4X) and in distal region (aii, 10X) of the papilla are shown. Digital segmentation illustrates mineralized volumes in proximal (yellow) and distal regions (blue) of the papilla (ai). The red dotted box (*) represents the 3D subvolume used in aii with segmented mineralized volumes of occluded tubule (purple), tubule wall (orange), and interstitium (green). Average MD ± standard deviations [range] are shown in mg/cc, and VF values are the ratios of mineral volume to total volume expressed in percentages in the table below. (b) Distal interstitial mineralization at a higher magnification can be observed in the tubule walls (red arrow heads) of the loops of Henle in RP⁻ with minerals of higher densities (white arrow head) (bi), and in the interstitial matrix of RP⁺ with minerals of higher densities (white arrow heads), and in tubular walls (red arrow heads) and adjacent interstitium (bii).