Ischemia-reperfusion injury (IRI) is a major risk factor for chronic renal failure. Here, we characterize the different modes of programmed cell death in the tubular and microvascular compartments during the various stages of IRI-induced AKI, and their relative importance to renal fibrogenesis. We performed unilateral renal artery clamping for 30 minutes and contralateral nephrectomy in wild-type mice (C57BL/6) or caspase-3 mice. Compared with their wild-type counterparts, caspase-3 mice in the early stage of AKI had high urine cystatin C levels, tubular injury scores, and serum creatinine levels. Electron microscopy revealed evidence of tubular epithelial cell necrosis in caspase-3 mice, and immunohistochemistry showed upregulation of the necroptosis marker receptor-interacting serine/threonine-protein kinase 3 (RIPK3) in renal cortical sections. Western blot analysis further demonstrated enhanced levels of phosphorylated RIPK3 in the kidneys of caspase-3 mice. In contrast, caspase-3 mice had less microvascular congestion and activation in the early and extension phases of AKI. In the long term (3 weeks after IRI), caspase-3 mice had reduced microvascular rarefaction and renal fibrosis, as well as decreased expression of -smooth muscle actin and reduced collagen deposition within peritubular capillaries. Moreover, caspase-3 mice exhibited signs of reduced tubular ischemia, including lower tubular expression of hypoxia-inducible factor-1 and improved tubular injury scores. These results establish the pivotal importance of caspase-3 in regulating microvascular endothelial cell apoptosis and renal fibrosis after IRI. These findings also demonstrate the predominant role of microvascular over tubular injury as a driver of progressive renal damage and fibrosis after IRI.

Pretransplant autoantibodies to LG3 and angiotensin II type 1 receptors (AT1R) are associated with acute rejection in kidney transplant recipients, whereas antivimentin autoantibodies participate in heart transplant rejection. Ischemia-reperfusion injury (IRI) can modify self-antigenic targets. We hypothesized that ischemia-reperfusion creates permissive conditions for autoantibodies to interact with their antigenic targets and leads to enhanced renal damage and dysfunction. In 172 kidney transplant recipients, we found that pretransplant anti-LG3 antibodies were associated with an increased risk of delayed graft function (DGF). Pretransplant anti-LG3 antibodies are inversely associated with graft function at 1 year after transplantation in patients who experienced DGF, independent of rejection. Pretransplant anti-AT1R and antivimentin were not associated with DGF or its functional outcome. In a model of renal IRI in mice, passive transfer of anti-LG3 IgG led to enhanced dysfunction and microvascular injury compared with passive transfer with control IgG. Passive transfer of anti-LG3 antibodies also favored intrarenal microvascular complement activation, microvascular rarefaction and fibrosis after IRI. Our results suggest that anti-LG3 antibodies are novel aggravating factors for renal IRI. These results provide novel insights into the pathways that modulate the severity of renal injury at the time of transplantation and their impact on long-term outcomes.

Ischemia-reperfusion injury (IRI) is a major risk factor for chronic renal failure. Caspase-3, an effector responsible for apoptosis execution, is activated within peritubular capillary (PTC) in the early stage of IRI-induced acute kidney injury (AKI). Recently, we showed that caspase-3-dependent microvascular rarefaction plays a key role in fibrosis development after mild renal IRI. Here, we further characterize the role of caspase-3 in microvascular dysfunction and progressive renal failure in both mild and severe AKI, by performing unilateral renal artery clamping for 30/60 minutes with contralateral nephrectomy in wild-type (C57BL/6) or caspase-3-/- mice. In both forms of AKI, caspase-3-/- mice showed better long-term outcomes in spite of worse initial tubular injury. After 3 weeks, they showed reduced PTC injury, decreased PTC collagen deposition and α-SMA expression, and lower tubular injury scores when compared to wild-type animals. Caspase-3-/- mice with severe IRI also showed better preservation of long-term renal function. Intra-vital imaging and micro Computed Tomography (microCT) revealed preserved PTCs permeability and better terminal capillary density in caspase-3-/- mice. Collectively, these results demonstrate the pivotal importance of caspase-3 in regulating long-term renal function after IRI and establish the predominant role of PTCs dysfunction as a major contributor to progressive renal dysfunction.