Platelet activation and platelet leukocyte aggregates are associated with acute kidney injury after cardiac surgery

We hypothesised that circulating extracellular vesicles (EV) and micro-RNA levels can serve as predictive and diagnostic markers for acute kidney injury (AKI) in patients undergoing cardiac surgery. Plasma samples were collected from patients recruited to the MaRACAS study before, immediately after and 6-12, 24 and 48 hours after the procedure from 95 patients. Particle size distribution and concentrations were measured using NanoSight. EV derivation and platelet and leukocyte activation were measured using flow cytometry. Platelet function was measured with Multiplate, and circulating soluble biomarkers were measured with a MAGPIX device. Micro-RNA assessment was performed with TaqMan arrays in batched samples. Selected micro-RNAs were validated in each sample by qRT-PCR. Our data shows that platelet-derived EVs were higher 24 hours after surgery. TaqMan arrays identified miR-668 downregulated before and miR-92a-1, -920, -518a- 3p, -133b and -1262 upregulated immediately after surgery in AKI patients. Validation confirmed that miR-1262 was significantly upregulated after surgery and identified miR-133b as downregulated before surgery. In addition, we showed that platelets were desensitised to ADP 6-12 hours after surgery. There were more platelet-granulocyte aggregates before and 24 hours after surgery, and levels of soluble ICAM1 were higher before surgery in patients with AKI. In conclusion, AKI is associated with platelet activation, suggesting that platelet inhibition treatments may be renoprotective. Furthermore, studies in larger cohorts should verify miR-1262 as a diagnostic marker of AKI. ### Competing Interest Statement Prof. Murphy received grants from Terumo and Baxter. The remaining authors have disclosed that they do not have any potential conflicts of interest. ### Funding Statement British Heart Foundation (RG/13/6/29947), (CH/12/1/29419) to GJM, MW, TK, and HA; Leicester and Bristol National Institute for Health Research Cardiovascular Biomedical Research Units. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by East Midlands - Leicester South Research Ethics Committee (REC reference 13/EM/0383) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript.