Background: CD146 is a cell adhesion molecule belonging to the immunoglobulin superfamily. It plays a critical role in cell proliferation and activation, and contributes to inflammatory reactions. We studied the association between CD146 and renal tubular epithelial cells (RTECs) under normal (NG) and high glucose (HG) to understand its role in the pathogenesis of diabetic nephropathy.
Methods: Human proximal tubular epithelial (HK-2) cells were cultured in different glucose media (NG5mM, HG15mM and HG40mM). CD146 mRNA expression was determined by RT-PCR. CD146 protein expression was assessed by fluorescence immunoassay, enzymatic immunohistochemistry and flow cytometry. A soluble form of CD146 was evaluated by ELISA.
Results: We found weak expression of CD146 mRNA and protein in the NG group. Faint labeling of CD146 protein was detected mainly at the cell-cell junction, with sparse staining in cytoplasm and nucleus. In the HG group, both membrane and intracellular expression of CD146 were significantly increased by high glucose, while osmotic pressure had no effect on CD146 expression in cultured HK-2 cells. A soluble form of CD146, sCD146, was detected in the supernatant of HK-2 cells in the NG group which was elevated in the HG40mM group (29.33 -/+ 1.22 ng/mL vs. 61.87 -/+ 9.10 ng/mL, p<0.05).
Conclusion: CD146 might be a novel marker for RTECs, correlating with cell proliferation and cell-cell conjunctions. High glucose up-regulates both CD146 and sCD146 expression. CD146 may be a biomarker of activated RTECs, and sCD146 may have clinical value for determining severity and prognosis of diabetic nephropathy.