Abstract
The pathogenesis of renal impairment in chronic liver diseases (CLDs) has been primarily studied in the advanced stages of hepatic injury. Meanwhile, the pathology of renal impairment in the early phase of CLDs is poorly understood, and animal models to elucidate its mechanisms are needed. Thus, we investigated whether an existing mouse model of CLD induced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) shows renal impairment in the early phase. Renal injury markers, renal histology (including immunohistochemistry for tubular injury markers and transmission electron microscopy), autophagy, and oxidative stress were studied longitudinally in DDC- and standard diet–fed BALB/c mice. Slight but significant renal dysfunction was evident in DDC-fed mice from the early phase. Meanwhile, histological examinations of the kidneys with routine light microscopy did not show definitive morphological findings, and electron microscopic analyses were required to detect limited injuries such as loss of brush border microvilli and mitochondrial deformities. Limited injuries have been recently designated as sublethal tubular cell injury. As humans with renal impairment, either with or without CLD, often show almost normal tubules, sublethal injury has been of particular interest. In this study, the injuries were associated with mitochondrial aberrations and oxidative stress, a possible mechanism for sublethal injury. Intriguingly, two defense mechanisms were associated with this injury that prevent it from progressing to apparent cell death: autophagy and single-cell extrusion with regeneration. Furthermore, the renal impairment of this model progressed to chronic kidney disease with interstitial fibrosis after long-term DDC feeding. These findings indicated that DDC induces renal impairment with sublethal tubular cell injury from the early phase, leading to chronic kidney disease. Importantly, this CLD mouse model could be useful for studying the pathophysiological mechanisms of sublethal tubular cell injury.
Highlights
Acute kidney injury (AKI) is a common complication of chronic liver diseases (CLDs), and the prevalence is approximately 20% in patients with cirrhosis [1, 2]
The results showed that plasma creatinine levels were slightly but significantly increased from day 1 of DDC feeding compared to those of the control mice; the increase lasted throughout the early phase (Fig 1)
Urinary examinations showed a high level of a tubular damage marker, urinary neutrophil gelatinase-associated lipocalin (NGAL), and the urinary albumin/creatinine ratio were increased at day 7
Summary
Acute kidney injury (AKI) is a common complication of chronic liver diseases (CLDs), and the prevalence is approximately 20% in patients with cirrhosis [1, 2]. The pathogenesis of renal impairment in CLD has been primarily studied in the advanced stages of hepatic injury both in animal models and clinical studies [2, 3]. These studies revealed that hepatorenal syndrome and bile nephrosis are two major pathophysiological mechanisms of AKI in advanced hepatic failure [2,3,4,5]. The definitive pathological features of renal impairment in the early phase of CLDs is poorly understood in part because of the lack of animal models. This study focuses on renal impairment in the early phase of CLD induced in mice by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)
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