Login to Access Video or Poster Abstract: MP12-17
Sources of Funding: NIH P01 DK056788

Introduction

Brushite stone disease is rare, but apparently increasing in Western countries. Why some patients form their stones of brushite is unknown. We sought to identify proteins that might be involved uniquely in brushite stone formation.

Methods

Micro-CT characterized stone specimens from 15 patients (5 M-BR, 5 F-BR, 5 M-CaOx) were used, 2 from each patient except for 1 M-CaOx, for which enough material was available for only 1 specimen. These 29 stone specimens were ground to fine powder and protein was extracted using sonication in 8M urea and 10 mM dithiothreitol. Protein extracts were digested with trypsin and analyzed using label-free quantitative mass spectrometry via LC-MS/MS. The acquired data were searched against the UniProt protein sequence database of HUMAN using X!Tandem algorithms in the Trans-Proteomic Pipeline.

Results

1,941 unique protein database entries representing 1,812 unique gene products were identified, quantified, and statistically compared. Of these, 1,004 proteins were detected and quantified in all three groups, mean abundances compared by ANOVA, and fold-differences calculated. M-CaOx stone matrix had the largest number (305) of unique protein types while M-BR and F-BR proteins were least different. Significant differences in the abundance of both commonly detected and previously unreported stone matrix proteins were observed between groups that suggest differential stone-formation mechanisms. Overall, proteins in brushite stones were more likely to be of cellular origin, while proteins in CaOx stones were more likely to be those typically found in urine.

Conclusions

We found a number of proteins that differed significantly between CaOx and BR stones. Most of these were membrane or cytoplasmic proteins that were higher in brushite stones than in CaOx. These proteins could simply reflect the increased cell damage that has been shown to be a part of brushite stone disease, but they are also candidates to explain the formation of this unusual mineral in this aggressive form of stone disease.

Funding

NIH P01 DK056788