Nanouric acid or nanocalcium phosphate as central nidus to induce calcium oxalate stone formation: a high-resolution transmission electron microscopy study on urinary nanocrystallites

Figures & data

Table 1 Comparison of properties of urine from healthy controls and CaOx stone-forming patients (n=9)

Particulars	Healthy controls (n=9), mean ± SD	CaOx stone-forming patients (n=9), mean ± SD	Pa
Urine volume, mL/day	1,713±378	1,213±202	<0.05
Urine pH	6.09±0.27	6.31±0.23	NS
Calcium, mg/L	112±14	147±32	<0.05
Oxalate, mg/L	20.1±3.0	35.2±5.11	<0.05
Phosphorous, mg/L	441±59	481±89	NS
Uric acid excretion, mg/L	496±128	741±203	<0.01
Citrate excretion, mg/L	341±81	236±56	<0.05
GAGs excretion, mg/L	9.33±2.90	4.32±2.04	<0.01
Magnesium, mg/L	61.0±14.8	71.1±14.2	<0.05
Creatinine, mg/L	909±188	1,069±169	NS
Zeta potential, mV	−(10.2±2.0)	−(6.09±1.91)	<0.01

Note:

a Data were analyzed using a Student’s t-test.

Abbreviations: SD, standard deviation; CaOx, calcium oxalate; GAG, glycosaminoglycan; NS, not significant.

Figure 1 X-ray diffraction spectra of stones in two representative calcium oxalate stone patients.

Notes: (A) patient A, (B) patient B. ^apeak at d=2.26 (202), ^bpeak at d=2.24 (213). The black arrows indicate the corresponding peaks and crystal faces. ★calcium oxalate monohydrate, ✰calcium oxalate dihydrate.

Figure 2 High-resolution transmission electron microscopy images of urinary nanocrystallites of two representative calcium oxalate stone patients.

Notes: (A) Patient A, the bar: 500 nm; (B) patient B, the bar: 200 nm.

Figure 3 Fast Fourier transformation (FFT) images of high-resolution transmission electron microscopy in different areas of urinary nanocrystallites in one representative calcium oxalate stone patient.

Notes: (A–D) show patients A–D, respectively. a and b show the FFT diffraction patterns transformed from the respective yellow boxes in A.

Abbreviation: d, interplanar spacing.

Table 2 High-resolution transmission electron microscopy diffraction data and attributes in different areas of urinary crystallites in patients with calcium oxalate stones

	Measured d	d in PDF card	Attribution
(A)
a	d=2.88 Å	d=2.88 Å	(0210) plane of β-CaP
b	d=1.55 Å	d=1.55 Å	(517) plane of β-CaP
c	d=1.39 Å	d=1.39 Å	(1,514) plane of β-CaP
(B)
a	d=5.88 Å	d=5.93 Å	($\overline{1}$01) plane of COM
b	d=2.60 Å	d=2.61 Å	(220) plane of β-CaP
c	d=2.19 Å	d=2.19 Å	(404) plane of β-CaP
d	d=1.72 Å	d=1.73 Å	($\overline{3}$23) plane of COM
e	d=1.62 Å	d=1.62 Å	(2,218) plane of β-CaP
f	d=1.55 Å	d=1.55 Å	(517) plane of β-CaP

Note: (A) data from patient D, (B) data from patient A. (a–f) The different interplanar spacings of urinary crystallites.

Abbreviations: CaP, calcium phosphate; COM, calcium oxalate monohydrate; d, crystal plane distance; PDF, powder diffraction file.

Figure 4 Selected area electron diffraction images in different areas of urinary crystallites in one patient with calcium oxalate stones.

Note: (A) patient D, (B) patient A.

Abbreviation: d, interplanar spacing.

Figure 5 High-resolution transmission electron microscopy and selected area electron diffraction images of urinary nanocrystallites of one representative calcium oxalate stone patient. The bar: (A) 100 nm, (B) 10 nm, (C) 5 nm, (D) 2 1/nm.

Notes: The areas B, C, and D in (A) are enlarged in (B), (C), and (D), respectively. a and b show the FFT diffraction patterns transformed from the respective yellow boxes in B.

Abbreviations: CaP, calcium phosphate; COM, calcium oxalate monohydrate; d, interplanar spacing.

Figure 6 Atomic ratios from energy dispersive X-ray spectroscopy analysis of the central and surrounding regions of different urinary crystallites from calcium oxalate monohydrate stone patients.

Figure 7 Energy dispersive X-ray spectroscopy analysis of the elemental distribution of urinary crystallite of a representative calcium oxalate stone patient.

Notes: (A, C) High-resolution transmission electron microscopy images; (B, D) element distribution, in which (A, B) show the central part, and (C, D) show the outside part of urinary crystallites.

Figure 8 Schema of the process of papillary COM renal stone formation.

Abbreviations: CaP, calcium phosphate; COM, calcium oxalate monohydrate; GAGs, glycosaminoglycans; UA, uric acid.