Electrolyte and metabolite composition of cystic fluid from a rat model of ARPKD

Fluid-filled cysts are the key feature of polycystic kidney disease, which eventually leads to renal failure. We analyzed the composition of cyst fluid from a rat model of autosomal recessive polycystic kidney disease, the PCK rat, and identified sexual differences. Our results demonstrate that the ion composition of cyst fluid differs from that of urine or plasma. Untargeted metabolomics combined with transcriptomic data identified tryptophan metabolism, enzyme metabolism, steroid hormone biosynthesis, and fatty acid metabolism as pathways differing between male and female PCK rats. We quantified 42 amino acids in the cyst fluid (PCK only), plasma, and urine of male and female PCK rats and Sprague Dawley rats. Taurine was the most concentrated amino acid present in the cyst fluid, and PCK rat urinary taurine excretion was over 3-fold greater than Sprague Dawley rats. Understanding the composition of cyst fluid provides valuable insights into disease pathophysiology and may help identify potential dietary or pharmacological interventions to mitigate disease progression and improve patient outcomes.

Sheathless CE-MS based metabolic profiling of kidney tissue section samples from a mouse model of Polycystic Kidney Disease

Capillary electrophoresis-mass spectrometry (CE-MS) using a sheathless porous tip interface emerged as an attractive tool in metabolomics thanks to its numerous advantages. One of the main advantages compared to the classical co-axial sheath liquid interface is the increased sensitivity, while maintaining the inherent properties of CE, such as a high separation efficiency and low sample consumption. Specially, the ability to perform nanoliter-based injections from only a few microliters of material in the sample vial makes sheathless CE-MS a well-suited and unique approach for highly sensitive metabolic profiling of limited sample amounts. Therefore, in this work, we demonstrate the utility of sheathless CE-MS for metabolic profiling of biomass-restricted samples, namely for 20 µm-thick tissue sections of kidney from a mouse model of polycystic kidney disease (PKD). The extraction method was designed in such a way to keep a minimum sample-volume in the injection vial, thereby still allowing multiple nanoliter injections for repeatability studies. The developed strategy enabled to differentiate between different stages of PKD and as well changes in a variety of different metabolites could be annotated over experimental groups. These metabolites include carnitine, glutamine, creatine, betaine and creatinine. Overall, this study shows the utility of sheathless CE-MS for biomass-limited metabolomics studies.