Urinary cMet as a prognostic marker in immunoglobulin A nephropathy

Abstract

The prediction of prognosis in patients with immunoglobulin A nephropathy (IgAN) is challenging. We investigated the correlation between urinary cMet (ucMet) levels and clinical parameters and examined the effects of cMet agonistic antibody (cMet Ab) in an in vitro IgAN model. Patients diagnosed with IgAN (n = 194) were divided into three groups representing undetectable (Group 1), below-median (Group 2) and above-median (Group 3) levels of ucMet/creatinine (ucMet/Cr). Stained kidney biopsy samples were graded according to cMet intensity. Primary-cultured human mesangial cells were stimulated with recombinant tumour necrosis factor (TNF)-α and treated with cMet Ab. Our results showed that ucMet/Cr levels positively correlated with proteinuria (P < .001). During the follow-up, patients in Group 3 showed a significantly lower probability of complete remission (CR; uPCr < 300 mg/g) than those in groups 1 and 2, after adjusting for blood pressure, estimated glomerular filtration rate, and proteinuria, which influence clinical prognosis (HR 0.60, P = .038); moreover, ucMet/Cr levels were also associated with glomerular cMet expression. After TNF-α treatment, the proliferation of mesangial cells and increased interleukin-8 and intercellular adhesion molecule-1 expression were markedly reduced by cMet Ab in vitro. In conclusion, ucMet/Cr levels significantly correlated with proteinuria, glomerular cMet expression, and the probability of CR. Further, cMet Ab treatment alleviated the inflammation and proliferation of mesangial cells. Hence, ucMet could serve as a clinically significant marker for treating IgAN.

Keywords: cMet agonistic antibody; complete remission; immunoglobulin A nephropathy; inflammation; mesangial cells; prognostic marker; proliferation; proteinuria; urinary cMet.

Figure 1

The association between ucMet/Cr levels and clinical parameters. A, The ucMet/Cr level converted to natural logarithm is positively correlated with proteinuria (Pearson correlation coefficients; R = .402, P < .001) and the percentage of crescent (Pearson correlation coefficients; R = .268, P = .001), and negatively correlated with serum albumin level (Pearson correlation coefficients; R = −.407, P < .001). B, No correlation was seen between ucMet/Cr levels and eGFR, IgA, and systolic blood pressure

Figure 2

Comparison of the CR probability according to ucMet/Cr level. A, Patients in Group 3 had a significantly lower probability of reaching CR compared to patients in Groups 1 + 2 (Log rank P = .010). B, Four combinations of proteinuria and ucMet/Cr levels were made, and the probabilities of reaching CR were compared. In patients with proteinuria >1 g/d, higher ucMet/Cr levels resulted in lower CR (Log rank P < .001)

Figure 3

cMet intensity in the kidney tissue and ucMet/Cr level. A, Glomerular cMet expression was correlated with ucMet/Cr level, B, but tubular cMet expression was not. Magnification: 600× (bar = 50 μm; glomerulus), 200× (bar = 100 μm; tubule). All data are presented as the mean ± SEM. *P < .05 (unpaired t test)

Figure 4

Proliferation and inflammation of mesangial cells alleviated by cMet Ab treatment. A, Observation of cMet and desmin (a mesangial cells marker) expressions which are confirmed to merge well at the same site. Magnification: 800× (bar = 50 μm). B, Ki‐67‐positive cell expression and proliferation were increased after TNF‐α stimulation and decreased dose‐dependently after cMet Ab treatment. The data shown are representative of three independent experiments (N = 3/group; N = 5/group). Magnification: 400× (bar = 100 μm). C, Flow cytometry showed that the IL‐8⁺ cells increased by approximately 1.7 times by TNF‐α stimulation compared to the control. A dose‐dependent decrease was observed on treatment with cMet Ab (N = 3/group). D, ICAM‐1 expression was also increased on TNF‐α stimulation; it was seen to reduce after cMet Ab treatment. Magnification: 800× (bar = 50 μm). The data shown are representative of three independent experiments. All data are presented as the mean ± SEM. *P < .05 (unpaired t test); **P < .01 (unpaired t test); ***P < .001 (unpaired t test)