Concentration of soluble urokinase plasminogen activator receptor (suPAR) in the pre-ovulatory follicular fluid is associated with development of ovarian hyperstimulation syndrome during ovarian stimulation.

PURPOSE: Investigating whether pre-ovulatory follicular fluid (FF) levels of selected proteins differ between women who do or do not develop severe ovarian hyperstimulation syndrome (OHSS) and evaluate whether they potentially could guide a "freeze-all" strategy. METHODS: FF was collected during a randomized controlled trial comparing OHSS in antagonist versus agonist protocol including 1050 women in their first assisted reproductive technology (ART) cycle during year 2009-2013. The present sub-study is a matched case-control study comparing FF levels of soluble urokinase plasminogen activator receptor (suPAR), C-reactive protein, placental growth factor, vascular endothelial growth factor, and angiopoietins 1 and 2 in OHSS cases (n = 25, severe OHSS, and ≥ 15 oocytes), high-risk controls (n = 25, no OHSS, and ≥ 15 oocytes), and low-risk controls (n = 25, no OHSS, and 5-8 oocytes). RESULTS: FF level of suPAR differed significantly between the three groups (p = 0.018) with mean (SD) levels of 2.3 (0.4) µg/L, 2.6 (0.8) µg/L, and 2.8 (0.6) µg/L in OHSS cases, high-risk controls, and low-risk controls, respectively. Receiver operating characteristic curve analysis demonstrated that suPAR levels could predict severe OHSS (AUC 0.678; 95% CI 0.553-0.803) with a sensitivity of 64% and a specificity of 66%. None of the other investigated proteins differed between the three groups or between OHSS cases and combined controls. CONCLUSION: The pre-ovulatory FF level of suPAR was significantly lower in women developing severe OHSS, indicating that the plasminogen activator system could be involved in the pathophysiology of OHSS. However, suPAR did not provide a satisfying predictive value for the prediction of OHSS.

Removal of focal segmental glomerulosclerosis (FSGS) factor suPAR using CytoSorb.

Treatment of primary focal segmental glomerulosclerosis (FSGS) and its recurrence after kidney transplantation associated with rapid deterioration of kidney function remains to be challenging despite advances in immunosuppressive therapy. The presence of circulating factors has been postulated to be a pivotal player in the pathogenesis of FSGS, although suPAR and CLCF-1 have been identified as the most promising causative factors. The potential therapeutic effect of suPAR elimination in an FSGS patient using CytoSorb, a hemoadsorption device that gained attention in the cytokine elimination in septic patients, was studied. Efficiency of total plasma exchange to remove suPAR was determined. CytoSorb hemoadsorption caused a 27.33% reduction of the suPAR level in a single treatment, whereas total plasma exchange showed a suPAR level reduction of 25.12% (n = 3; 95% confidence interval, 0.2777-0.8090; P < 0.01), which may indicate therapeutic potential in the treatment of primary FSGS and its recurrence in a kidney transplant.

An improved method for the detection and enrichment of low-abundant membrane and lipid raft-residing proteins.

A high degree of optimisation is required in native co-immunoprecipitation (co-IP) experiments with added challenges for low-abundant membrane proteins and masking by IgG molecules. Although in vivo tagged-protein purification avoids the IgG masking problem, modifying the terminus of the protein may result in conformational and post-translational modification changes. In this paper, we propose a method which combines four key aspects to improve the solubility and enrichment of low-abundant plasma membrane proteins using the urokinase plasminogen activator receptor (uPAR) as an example. As this GPI-linked receptor predominantly resides in lipid rafts (LR), we used a modified RIPA lysis buffer containing the non-ionic detergent, octyl-glucoside which solubilizes LRs to extract uPAR. This is followed by a modified crosslinking co-IP which covalently crosslinks the antibodies to the beads. Crosslinking allowed for a significant increase in the detection of uPAR with minimal IgG contamination using on-bead digestion or acid elution followed by digestion and analysis on high-throughput one-dimensional (nanoLC) MS/MS instrument (AbSciex 5600). To the best of our knowledge, this method of isolation is the first to be done to increase the yield of a low-abundant membrane protein and may be useful for the purification of other non-raft and raft-residing membrane proteins.