TIE2 activation by antibody-clustered endogenous angiopoietin-2 prevents capillary loss and fibrosis in experimental kidney disease
Riikka Pietilä, Amanda Marks-Hultström, Liqun He, Sami Nanavazadeh, Susan E. Quaggin, Christer Betsholtz, Marie Jeansson
Riikka Pietilä, Amanda Marks-Hultström, Liqun He, Sami Nanavazadeh, Susan E. Quaggin, Christer Betsholtz, Marie Jeansson
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Research Article Nephrology Vascular biology

TIE2 activation by antibody-clustered endogenous angiopoietin-2 prevents capillary loss and fibrosis in experimental kidney disease

Abstract

The role of endothelial dysfunction in tubulointerstitial fibrosis associated with chronic kidney disease (CKD) is not well understood. In this study, we demonstrate that the activation of the endothelial tyrosine kinase TIE2 alleviates renal pathology in experimental CKD in mice. TIE2 activation was achieved using a human angiopoietin-2–binding and TIE2-activating antibody (ABTAA) or through adult-induced endothelium-specific knockout of the vascular endothelial protein tyrosine phosphatase gene (Veptp). Both methods markedly protected CKD mice from endothelial dysfunction, peritubular capillary loss, tubular epithelial injury, and tubulointerstitial fibrosis. Conversely, silencing TIE2 through adult-induced endothelium-specific knockout of the Tie2 gene exacerbated CKD pathology. Additionally, we found that endothelial dysfunction promoted renal fibrosis not through endothelial-to-mesenchymal transition, as previously expected, but by inducing the expression of profibrotic PDGFB in tubular epithelial cells, a process that is inhibited by TIE2 activation. Our findings suggest that TIE2 activation via ABTAA warrants investigation as a therapy in human CKD, where there is a substantial unmet medical need.

Authors

Riikka Pietilä, Amanda Marks-Hultström, Liqun He, Sami Nanavazadeh, Susan E. Quaggin, Christer Betsholtz, Marie Jeansson

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Figure 1

Pharmacological or genetic activation of TIE2 improves renal perfusion and prevents capillary rarefaction following experimental CKD.

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Pharmacological or genetic activation of TIE2 improves renal perfusion a...
(A) Schematic diagram of the experimental setup with UUO, contralateral control kidney (CL), and ABTAA (or IgG) administration. (B and C) Schematic diagram of ABTAA function (B) and inducible conditional mouse lines used in the study (C). TAM, tamoxifen induction. (D and E) pTIE2/TIE2 in 3-day UUO kidneys in ABTAA (ABT) and VeptpiECKO (VeKO) mice, respectively. Data are based on n = 3–10 mice/group and 3 (D) and 1 (E) blots (see Supplemental Figure 2). (F) VEPTP in kidney lysates from CL and 3-day UUO kidneys in WT and VeptpiECKO mice. Data are based on n = 3 mice/group and 1 blot (see Supplemental Figure 2). (G) TIE2 protein measured by ELISA in kidney homogenates from CL and 3-day UUO kidneys in Tie2iECKO (T2KO) mice. Data are based on n = 3–5 mice/group. (H) Renal perfusion measured with ultrasound contrast imaging in 2-day UUO/CL kidneys from ABTAA-treated, VeptpiECKO, Tie2iECKO, and PdgfbiKO (PbKO) mice and their respective controls. The same group of sham-operated mice was used to establish baseline perfusion levels for comparison with UUO-injured kidneys. Data are based on n = 5–8 mice/group. (I–K) Immunohistochemistry and quantification from renal cortex for endothelial markers (endomucin [EMCN] and podocalyxin [PODXL]) in 3-day UUO kidneys from ABTAA-treated, VeptpiECKO, Tie2iECKO, and PdgfbiKO mice and their controls. Data are based on n = 5–11 mice/group and >600 images/marker. Scale bars: 50 μm. Data represent mean ± SD, and each symbol represents 1 mouse (females, magenta; males, cyan). *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, determined by 1-way ANOVA and Tukey’s post hoc test (F–H, J, and K) or unpaired 2-tailed Student’s t test (D and E).