Matching Human Unilateral AKI, a Reverse Translational Approach to Investigate Kidney Recovery after Ischemia.

BACKGROUND: The duration of renal ischemia that is associated with (or leads to) renal injury in patients is uncertain, and a reverse translational research approach has been proposed to improve animal models of AKI to facilitate clinical translatability. We developed a two murine models of unilateral renal ischemia to match a recently published human study that investigated renal injury after unilateral renal ischemia during partial nephrectomy. METHODS: Eight 10-week-old C57BL/6 male mice underwent left UiAKI or sham procedure, with or without intra-operative ice packs. Functional, histological, and biomarker outcomes were followed at 2, 6 and 24 hours, or 14 or 28 days later. The 14 and 28 day cohorts were duplicated such that contralateral nephrectomy could be performed 3 days prior to sacrifice with functional measurements obtained to isolate the glomerular filtration rate of the injured kidney. RESULTS: The short-term outcomes correlated with the human study findings with urine and serum biomarkers of injury peaking around 24 hours and then normalizing, and reassuring immediate histological outcomes. Functional and histological outcomes at the later time-points (14 and 28 days) demonstrate an increase in fibrosis markers, and a reduction in glomerular filtration rate in the injured kidney, corresponding to the duration of ischemia, while serum and urine biomarkers remained reassuring. CONCLUSIONS: Our findings suggest that clinically available biomarkers of renal function are falsely reassuring against long-term injury following UiAKI, and that the duration of ischemia correlates with impaired function and increased fibrosis.

Periostin induces kidney fibrosis after acute kidney injury via the p38 MAPK pathway.

Periostin plays a crucial role in fibrosis, and acute kidney injury results in a high risk of progression to chronic kidney disease. Therefore, we hypothesized that periostin was involved in the progression of acute kidney injury to kidney fibrosis. Unilateral ischemia-reperfusion injury (UIRI) was induced in 7- to 8-wk-old male wild-type and periostin-null mice, and the animals were observed for 6 wk. In vitro, human kidney-2 cells and primary-cultured human tubular epithelial cells were incubated under hypoxic conditions (5% O2, 5% CO2, and 90% N2) for 5 days. The cells were also cultured with recombinant periostin (rPeriostin) and a p38 mitogen-activated protein kinase (MAPK) inhibitor in a hypoxic incubator. At 6 wk after UIRI, interstitial fibrosis/tubular atrophy was significantly alleviated in periostin-null mice compared with wild-type controls. In addition, periostin-null mice had attenuated expression of fibrosis/apoptosis markers and phosphorylated-p38 MAPK compared with wild-type controls. In vitro, hypoxic injury increased the expression of fibrosis markers, periostin, and phosphorylated-p38 MAPK, which was comparable to or substantially greater than their expression levels following treatment with recombinant transforming growth factor-ß1 under normoxic conditions. Furthermore, rPeriostin treatment under hypoxic conditions enhanced fibrosis/apoptosis markers and phosphorylated-p38 MAPK. In contrast, p38 MAPK inhibition ameliorated hypoxia-induced fibrosis, and the addition of the p38 MAPK inhibitor to rPeriostin significantly ameliorated the changes induced by rPeriostin. In conclusion, periostin promotes kidney fibrosis via the p38 MAPK pathway following acute kidney injury triggered by a hypoxic or ischemic insult. Periostin ablation may protect against chronic kidney disease progression.

Shared and Distinct Renal Transcriptome Signatures in 3 Standard Mouse Models of Chronic Kidney Disease.

INTRODUCTION: Several mouse models with diverse disease etiologies are used in preclinical research for chronic kidney disease (CKD). Here, we performed a head-to-head comparison of renal transcriptome signatures in standard mouse models of CKD to assess shared and distinct molecular changes in three mouse models commonly employed in preclinical CKD research and drug discovery. METHODS: All experiments were conducted on male C57BL/6J mice. Mice underwent sham, unilateral ureter obstruction (UUO), or unilateral ischemic-reperfusion injury (uIRI) surgery and were terminated two- and 6-weeks post-surgery, respectively. The adenine-supplemented diet-induced (ADI) model of CKD was established by feeding with adenine diet for 6 weeks and compared to control diet feeding. For all models, endpoints included plasma biochemistry, kidney histology, and RNA sequencing. RESULTS: All models displayed increased macrophage infiltration (F4/80 IHC) and fibrosis (collagen 1a1 IHC). Compared to corresponding controls, all models were characterized by an extensive number of renal differentially expressed genes (≥11,000), with a notable overlap in transcriptomic signatures across models. Gene expression markers of fibrosis, inflammation, and kidney injury supported histological findings. Interestingly, model-specific transcriptome signatures included several genes representing current drug targets for CKD, emphasizing advantages and limitations of the three CKD models in preclinical target and drug discovery. CONCLUSION: The UUO, uIRI, and ADI mouse models of CKD have significant commonalities in their renal global transcriptome profile. Model-specific renal transcriptional signatures should be considered when selecting the specific model in preclinical target and drug discovery.

Analysis of the Function of CCN2 in Tubular Epithelium Cells with a Focus on Renal Fibrogenesis.

Renal interstitial fibrosis is the final common pathway in the process of all kidney diseases, and it results in chronic kidney disease. CCN2 is an important factor in the pathogenesis of renal interstitial fibrosis, and analysis of its function can lead to treatments for chronic kidney disease. Since CCN2 knockout mice are developmentally lethal, generation of conditional knockout mice is essential for in vivo analysis. Since CCN2 is expressed in a variety of cells in the kidney, including podocytes, mesangial cells, pericytes, and tubular epithelial cells, it is necessary to perform cell-specific verification of the cells that play a central role in fibrosis. However, cell-specific validation using the Cre/loxP system in vivo has only been performed in mesangial cells. In our research program, we are focusing on the role of CCN2 in tubular epithelial cells in renal fibrogenesis. In this report, we introduce the creation of a tubular epithelial cell-specific knockout model and method of its analysis.

Integrated Analysis of the CircRNA-Based ceRNA Network in Renal Fibrosis Induced by Ischemia Reperfusion Injury.

Background: Circular RNAs (circRNAs), which have broad posttranscriptional regulatory potencies, are involved in the pathogenesis of fibrotic diseases and are promising diagnostic biomarkers and therapeutic targets. However, their specific roles in renal fibrosis remain elusive. Methods: A robust unilateral renal ischemia reperfusion injury (UIRI) mouse model was established to recapitulate the pathophysiology of renal fibrosis. The expression of circRNAs, miRNAs, and mRNAs was profiled by high-throughput RNA sequencing technology. Results: In total, 4983 circRNAs, 216 miRNAs, and 6371 mRNAs were differentially expressed in UIRI-induced fibrotic kidneys. Candidate circRNAs and miRNAs were validated by RT-qPCR in both UIRI and unilateral ureteral obstruction mouse models. Bioinformatic analysis indicated that the parental genes of the differentially expressed circRNAs were predominantly implicated in focal adhesion, adhesion junctions, and regulation of actin cytoskeleton pathways. Through circRNA-miRNA-mRNA construction, we identified two hub genes, circSlc8a1 and circApoe, that targeted a large number of differentially expressed miRNAs and mRNAs related to metabolism and cytokine-cytokine receptor pathways, respectively. Conclusion: CircRNAs were dysregulated in the UIRI model and might be potentially involved in the pathogenesis of renal fibrosis. Research efforts should focus on unravelling the functions of aberrantly expressed circRNAs in renal fibrosis to uncover biomarkers that would enable early diagnosis and the design of prompt therapeutic interventions to prevent disease progression.