Proteome of human calcium kidney stones.
OBJECTIVE
Idiopathic calcium oxalate (CaOx) stones are believed to develop attached to papillary subepithelial deposits called Randall's plaques. Calcium phosphate (CaP) stones, conversely, are thought to arise within the inner medullary collecting ducts, enlarging and damaging surround tubular structures as they expand. If this is true, we theorize that differences will be seen within the organic portion (matrix) of CaOx stones compared with CaP stones using a mass spectroscopy (MS) approach.


METHODS
From a cohort of 47 powdered stones, 25 calculi (13 CaOx, 12 CaP) were confirmed to contain a dominant mineral content of >80% by powder x-ray diffraction. Matrix proteins were then extracted, purified, and digested. Peptide tandem MS data were acquired, and spectra were searched against a large human protein database to identify protein matches.


RESULTS
No significant differences were seen between pattern profiles of CaOx and CaP stones. However, variations in protein expression patterns were seen within individual CaOx (monohydrate and dihydrate) and CaP (apatite and brushite) mineral subtypes, suggesting a relationship between crystal-surface binding properties and matrix composition. Both groups contain a large number of inflammatory proteins and a catalog of common proteins is included.


CONCLUSIONS
Calcium kidney stone matrix contains hundreds of proteins and is predominated by proteins associated with inflammatory response. Many of the same proteins were identified in both CaOx and CaP stones, suggesting inflammation as a unifying origin or a common secondary role in calcium stone pathogenesis.
Canales
Benjamin K
BK
Department of Urology, University of Minnesota, Minneapolis, Minnesota, USA. Benjamin.canales@urology.ufl.edu
Anderson
Lorraine
L
Higgins
Leeann
L
Ensrud-Bowlin
Kathy
K
Roberts
Ken P
KP
Wu
Baolin
B
Kim
Il Won
IW
Monga
Manoj
M
D001031:Apatites / Q000032:analysis; D002129:Calcium Oxalate / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D003460:Crystallization; D004847:Epithelial Cells / Q000473:pathology; D006801:Humans; D007249:Inflammation; D007668:Kidney / Q000473:pathology; D007669:Kidney Calculi / Q000737:chemistry* / Q000209:etiology; D013058:Mass Spectrometry; D011506:Proteins / Q000032:analysis* / Q000302:isolation & purification; D040901:Proteomics; D014961:X-Ray Diffraction
D001031:Apatites; D002130:Calcium Phosphates; D011506:Proteins; D002129:Calcium Oxalate; C494366:calcium phosphate, dibasic, dihydrate