ABSTRACT
Cell senescence plays a major role in the progression of tumors and chronic conditions such as diabetes and chronic kidney disease. Senescent cells are an important model for the study of aging-related diseases, and there is currently no efficient method for sorting out senescent cells. Decoy receptor 2 (DcR2) is a transmembrane receptor of the tumor necrosis factor superfamily, which is specifically expressed in senescent cells. In this study, we used magnetic activated cell sorting (MACS) isolation of a highly-pure populations DcR2-positive renal tubular epithelial cells (RTECs) based on three senescent cell models including the fifth passage cells, advanced glycation end-products (AGEs)- and H2O2-induced cells. The percentages of DcR2 positive RTECs in G1 and S phases increased by 20% and 4%, respectively, as compared to that in the pre-sorted cells. The positivity rates of SA-ß-gal, p16, and senescence-associated heterochromatin foci (SAHF) in DcR2-positive RTECs were about 40%, 30%, and 44% higher than that prior to cell sorting. The levels of IL-6 and TGF-ß1 in the supernatant were increased by 1.7 and 1.5 folds, respectively, as compared to that observed prior to sorting. No significant cell death was observed after 5days of continuous culture. Ki-67 positive expression rate in DcR2 negative RTECs was significantly higher than that in DcR2 positive RTECs after MACS. We demonstrated the use of DcR2 to classify live, senescent RTECs with a high specificity and stability. Our findings lay the foundation for further study of senescent RTECs in the progression of chronic kidney disease.
Subject(s)
Cell Proliferation , Cellular Senescence , Epithelial Cells/immunology , Immunomagnetic Separation , Kidney Tubules/immunology , Tumor Necrosis Factor Decoy Receptors/immunology , Animals , Cell Proliferation/drug effects , Cells, Cultured , Cellular Senescence/drug effects , Epithelial Cells/drug effects , Epithelial Cells/metabolism , G1 Phase Cell Cycle Checkpoints , Glycation End Products, Advanced/pharmacology , Hydrogen Peroxide/pharmacology , Interleukin-6/metabolism , Ki-67 Antigen/metabolism , Kidney Tubules/cytology , Kidney Tubules/drug effects , Kidney Tubules/metabolism , Male , Mice, Inbred C57BL , Phenotype , S Phase Cell Cycle Checkpoints , Time Factors , Transforming Growth Factor beta1/metabolism , Tumor Necrosis Factor Decoy Receptors/metabolismABSTRACT
Tubulointerstitial injury (TII) plays a crucial role in the progression of diabetic nephropathy (DN), but lack of specific and sensitive biomarkers for monitoring TII in DN management. This study is to investigate whether urinary decoy receptor 2 (uDcR2) could serve as a novel noninvasive biomarker for assessing TII in DN. We recruited 311 type 2 diabetics and 139 DN patients who were diagnosed by renal biopsy. uDcR2 levels were measured by ELISA, and renal DcR2 expression was detected immunohistochemically. Associations between uDcR2 and renal DcR2 and renal functional parameters were evaluated. Receiver operating characteristics (ROC) curve analyzed area under the curve (AUC) of uDcR2 for assessing TII. Double staining was undertaken for renal DcR2 with proximal and distal tubular markers; senescent markers p16, p21, and senescence-associated ß-galactosidase (SA-ß-gal); and fibrotic markers collagen I and IV. We found DcR2 was primarily expressed in renal proximal tubules; uDcR2 levels were elevated per albuminuria stratum and correlated with renal functional parameters in diabetics and were associated with percentage of tubular DcR2 and TII score in DN. The uDcR2 had an AUC of 0.909 for assessing TII in DN by ROC analysis. Almost all tubular DcR2 was coexpressed with p16 and p21, and nearly more than one-half of tubular DcR2 was positive for SA-ß-gal, primarily in collagen I- and IV-positive regions of DN. Our results indicate uDcR2 could potentially serve as a novel biomarker for TII and may reflect senescence of renal proximal tubular cells in DN pathogenesis.
