GPR68 and chronic kidney disease: To investigate whether high-GPR68-expressing monocytes are involved in the exacerbation of cardiac dysfunction in mice with chronic renal failure, monocytes were collected from the spleen of healthy mice and cells were infected with lentivirus-expressing microRNA (miRNA) against Gpr68. Control or GPR68-downregulated monocytes were injected intravenously into Splx-5/6Nx mice every 3 days for 2 weeks (Fig. 4a).