Three articles were recently published by Petra Zürbig (RENALTRACT Principal Investigator) and Pedro Magalhães (ESR 9) at Mosaiques Diagnostics. In the first two articles “Association of kidney fibrosis with urinary peptides: a path towards non-invasive liquid biopsies?” and “Comparison of Urine and Plasma Peptidome Indicates Selectivity in Renal Peptide Handling, they were main contributors while they participated to the collaboration in the third one “Urinary peptidomics analysis reveals proteases involved in diabetic nephropathy”. Below is the description and link to these articles:
Association of kidney fibrosis with urinary peptides: a path towards non-invasive liquid biopsies?
A hallmark of chronic kidney disease progression is renal fibrosis, characterized by excessive accumulation of extracellular matrix (ECM) proteins. In this study, the utility of urinary peptides as a non-invasive readout of kidney fibrosis was evaluated by studying both the association of the previously identified urinary peptide-based CKD273 classifier and individual urinary peptides with the degree of fibrosis.
CKD273 displayed a significant correlation with the degree of fibrosis, while biochemical markers such as glomerular filtration rate, albuminuria and proteinuria, did not. In addition, seven individual urinary peptides displayed a significant and negative correlation with the level of kidney fibrosis. All peptides were ECM related, i.e. derived from different collagen fragments. This study provides the first investigation of the severity of kidney fibrosis and its association with urinary peptidomics.
Comparison of Urine and Plasma Peptidome Indicates Selectivity in Renal Peptide Handling
In this manuscript, twenty-two human matched urine and plasma samples were analysed by CE-MS profiling and tandem-MS. 561 plasma peptides and 1461 urinary peptides were identified, along with the determination of their overlap (n=90 peptides) in order to obtain insights of the origin of endogenous urinary peptides (e.g. kidney and urinary tract-derived or circulation system). Furthermore, when investigating the relative abundance of all overlapping peptides, no significant correlation was detected, which may a result of the tubular reabsorption of the blood-derived peptides, which are present in primary urine. However, when investigating only collagen fragments (most representative overlapping peptides), a significant correlation was found, suggesting that those may generally be excluded from tubular reabsorption. This study indicates that collagen fragments may have a specific biological function and mechanism for their selective excretion, a hypothesis meriting further experimental investigation.
Urinary peptidomics analysis reveals proteases involved in diabetic nephropathy
Abstract: Mechanisms underlying the onset and progression of nephropathy in diabetic patients are not fully elucidated. Deregulation of proteolytic systems is a known path leading to disease manifestation, therefore we hypothesized that proteases aberrantly expressed in diabetic nephropathy (DN) may be involved in the generation of DN-associated peptides in urine. We compared urinary peptide profiles of DN patients (macroalbuminuric, n = 121) to diabetic patients with no evidence of DN (normoalbuminuric, n = 118). 302 sequenced, differentially expressed peptides (adjusted p-value < 0.05) were analysed with the Proteasix tool predicting proteases potentially involved in their generation. Activity change was estimated based on the change in abundance of the investigated peptides. Predictions were correlated with transcriptomics (Nephroseq) and relevant protein expression data from the literature. This analysis yielded seventeen proteases, including multiple forms of MMPs, cathepsin D and K, kallikrein 4 and proprotein convertases. The activity of MMP-2 and MMP-9, predicted to be decreased in DN, was investigated using zymography in a DN mouse model confirming the predictions. Collectively, this proof-of-concept study links urine peptidomics to molecular changes at the tissue level, building hypotheses for further investigation in DN and providing a workflow with potential applications to other diseases.
6th December 2018