Therapeutic potential of regulatory macrophages generated from peritoneal dialysate in adriamycin nephropathy

Cell therapy using macrophages requires large amounts of cells, which are difficult to collect from patients. Patients undergoing peritoneal dialysis (PD) discard huge numbers of peritoneal macrophages in dialysate daily. Macrophages can be modulated to become regulatory macrophages, which have shown great promise as a therapeutic strategy in experimental kidney disease and human kidney transplantation. This study aimed to examine the potential of using peritoneal macrophages (PMs) from peritoneal dialysate to treat kidney disease. Monocytes/macrophages accounted for >40% of total peritoneal leukocytes in both patients and mice undergoing PD. PMs from patients and mice undergoing PD were more mature than peripheral monocytes/macrophages, as shown by low expression of C-C motif chemokine receptor 2 (CCR2) and morphological changes during in vitro culture. PMs from patients and mice undergoing PD displayed normal macrophage function and could be modulated into a regulatory (M2) phenotype. In vivo, adoptive transfer of peritoneal M2 macrophages derived from PD mice effectively protected against kidney injury in mice with adriamycin nephropathy (AN). Importantly, the transfused peritoneal M2 macrophages maintained their M2 phenotype in kidney of AN mice. In conclusion, PMs derived from patients and mice undergoing PD exhibited conventional macrophage features. Peritoneal M2 macrophages derived from PD mice are able to reduce kidney injury in AN, suggesting that peritoneal macrophages from patients undergoing PD may have the potential for clinical therapeutic application.