Fig 2: KITLG promoted EndoMT and furthered the increase in permeability of GECs through the AKT/ERK1/2 signaling pathway. EndoMT markers, including E-cadherin, N-cadherin, and vimentin levels, were assessed in HGECs treated with BSA (300 µg/ml) or AGE–BSA (300 µg/ml) for 48 h (n = 3). (A–C) After treatment with KITLG (10 ng/ml) for 48 h, EndoMT was examined in HGECs using Western blotting (n = 3). (D) The permeability of HGECs was examined after treatment with normal control (NC) and KITLG (10 ng/ml) for 48 h using FITC–dextran dye (n = 3). (E,F) PCDH7 and PCDH17 mRNA were assessed in HGECs treated with NC and KITLG for 24 h (n = 3). (G–J) The level of phospho-AKT/AKT and phospho-ERK1/2/ERK1/2 protein expression in HGECs treated with BSA, AGE–BSA, NC or KITLG for 6 h were examined using Western blotting. * p < 0.05, ** p < 0.01, *** p < 0.001 by Student’s t-test.

Fig 3: Positive relationship between KITLG expression and kidney dysfunction in mice with DN. (A,B) The expression of KITLG and N-cadherin in GECs of kidneys in mice is shown. The kidney sections of non-diabetic db/m mice and diabetic db/db mice were co-stained with KITLG (green) and CD34 (brown), as the marker of GECs. (C) Urinary KITLG levels were measured in db/m mice (n = 6) and db/db mice (n = 6) using ELISA. (D) The correlation between urinary KITLG levels and urinary albumin/creatinine ratio (ACR). Urine albumin was measured using an immunoturbidimetric assay, and urine creatinine was determined by an enzymatic method. The bar graph represents the mean ± S.E.M. of at least three independent experiments. *** p < 0.001 by Student’s t-test; the p-value of the correlation was assessed by Spearman analysis.

Fig 4: Illustration of the mechanism by which AGEs induce EndoMT and the increase in the permeability of GECs through the KITLG/AKT/ERK1/2 pathway and urinary KITLG as a biomarker of kidney injury in type 2 DM. Furthermore, imatinib reversed AGE-induced EndoMT and impaired the permeability of GECs.

Fig 5: AGEs increased KITLG expression in GECs. (A) KITLG mRNA expression in HGECs treated with NG (5.5 mM) or HG (25 mM) for 24 h (n = 3). (B) KITLG mRNA expression in HGECs treated with BSA (300 μg/ml) or AGE–BSA (300 μg/ml) for 24 h (n = 3). KITLG mRNA levels were assessed by quantitative real-time polymerase chain reaction (qRT-PCR). (C,D) KITLG protein level in the supernatant of HGECs treated with NG, HG, BSA, and AGE–BSA for 48 h. The level of KITLG was determined by an ELISA kit. The bar graph represents the mean ± S.E.M. ns = not significant, * p < 0.05, ** p < 0.01 by Student’s t test.