Real‐time in vivo imaging confirms the presence of apoptotic signaling at the onset of ischemia‐reperfusion injury

Abstract

Renal ischemia-reperfusion injury (IRI) is a complex disorder characterized by varying degrees of structural and functional losses. The degree of the insult depends on the severity of the condition and the kidney's ability to recover. IRI simultaneously contributes to the development of acute tubular injury and microvascular/endothelial injury. To further complicate matters, it is also believed that microvascular/endothelial injury leads to apoptotic signaling to, in turn, further reduce capillary density and blood flow, and exacerbate tubular damage that supports the transition from acute to chronic disorders. In recent times, studies have employed intravital imaging systems to enhance our understanding of these mechanisms. Such studies have identified ways that intravital renal imaging can be used to track apoptosis in vivo. As a result, we aimed to build on this convention by searching for evidence of apoptotic signaling at the onset of IRI. Using intravital two-photon microscopy, fluorescent micrographs of tubular nuclei were collected and examined at the onset of ischemia. Signs of apoptosis were identified by cell shrinkage that led to the formation of apoptotic bodies. Furthermore, the concurrent presence of necrotic signaling, which led to increased cell permeability and swelling, was also visualized. Altogether these results confirm the presence of apoptotic signaling, as well as, necrotic signaling, and provide important evidence about the previously unconfirmed cell death mechanisms that can support the debilitating progression of IRI.