Porcine models of acute kidney injury

Citronellol protects renal function by exerting anti-inflammatory and antiapoptotic effects against acute kidney injury induced by folic acid in mice

Acute kidney injury (AKI) is characterized by an abrupt cessation of kidney function. Folic acid-induced renal tubular damage is marked by immense inflammation and apoptosis in the kidney. Citronellol is a type of natural monoterpene alcohol commonly used in traditional medicine. Citronellol possesses pharmacological properties such as antioxidants, anti-inflammatory, and analgesic effects. This study aimed to investigate the reno-protective effect of citronellol against folic acid-induced AKI in mice models. Mice were divided into four groups. In addition to control and AKI-induction groups, two treatment groups were mice that received 50 or 100 mg/kg/day of citronellol orally for four consecutive days. On day 4, mice also received a single injection of folic acid (250 mg/kg) and were euthanized after 48 h. Citronellol 50 and 100 mg/kg rescued renal function as indicated by the significant reduction of serum urea, serum creatinine, and gene expression of KIM-1 compared to the non-treated group. In addition, citronellol 50 and 100 mg/kg relieved renal inflammation by significantly downregulating NF-κB, IL-6, and IL-1β gene expressions compared to the non-treated mice. Furthermore, citronellol retarded renal apoptotic events by the significant decline in renal tissue BAX and cleaved caspase-3 levels compared to non-treated mice. Histopathological report of renal tissue provides further evidence that augments the above results. The study highlighted the importance of some natural compounds that could have a place in therapeutic procedures for kidney injury, as observed by the strong renal protective effects of citronellol against AKI and remarkable anti-inflammatory and antiapoptotic actions.

Impact of different anesthetic protocols during anesthesia for the establishment of a porcine model of acute kidney injury

BACKGROUND

During the establishment of a model of acute kidney injury (AKI) in pigs, we observed a high prevalence of malignant hyperthermia (MH). These complications led us to refine the anesthetic protocol. This publication describes the impact of the choice of anesthetics on the results obtained.

METHODS

Pigs were euthanized at the end of the procedure, without recovery from anesthesia. Three anesthetic protocols were used: sevoflurane inhalation (ProtocolA, n = 5), a combination of ketamine, medetomidine and diazepam by intravenous infusion (ProtocolB, n = 5), and a combination of ketamine, diazepam, medetomidine, glucose, and noradrenaline (ProtocolC, n = 5). All pigs received morphine for analgesia. AKI was induced by interrupting renal perfusion for 90 min. MH was diagnosed based on clinical and biological parameters.

RESULTS

All MH pigs belonged to ProtocolA. MH pigs showed significantly higher maximum rectal temperature (p = 0.04), maximum expired carbon dioxide (CO2; p = 0.04), maximum heart rate (HR; p = 0.03), plasma concentration of creatinine and potassium (p < 0.0001). Protocol A pigs had a significantly higher maximum HR (p = 0.01) and hyperkalemia compared to the two other groups (ProtocolB, p = 0.005 and ProtocolC, p < 0.0001). Pigs from ProtocolA had a significantly lower minimum mean arterial pressure (MAP) than ProtocolC group (p = 0.03) and MAP remained below 60 mmHg for longer (p = 0.004). In ProtocolB, minimum glycemia was lower than other groups (p = 0.01).

CONCLUSION

Sevoflurane use was associated with the occurrence of MH, hemodynamic alterations and changes in plasma concentration of creatinine and potassium. These modifications can have a major impact on the validation of an experimental AKI model.

Ultrasound-guided renal subcapsular transplantation of mesenchymal stem cells for treatment of acute kidney injury in a minipig model: safety and efficacy evaluation

BACKGROUND

Acute kidney injury (AKI) is a major global public health concern with limited treatment options. While preclinical studies have suggested the potential of mesenchymal stem cells (MSCs) to repair and protect injured kidneys in AKI, clinical trials using transarterial MSCs transplantation have yielded disappointing results. This study aimed to investigate the feasibility and safety of minimally invasive renal subcapsular transplantation of MSCs for treating AKI in a minipig model, ultimately aiming to facilitate the clinical translation of this approach.

METHODS

A novel AKI minipig model was established by combining cisplatin with hydration to evaluate the effectiveness of potential therapies. Renal subcapsular catheterization was successfully achieved under ultrasound guidance. Subsequently, the efficacy of renal subcapsular MSCs transplantation was assessed, and the biological role of the tryptophan metabolite kynurenine (Kyn) in AKI was elucidated through both in vivo and in vitro experiments.

RESULTS

The method of pre-hydration at 4% of body weight, followed by post-cisplatin (3.8 mg/kg) hydration at 2% of body weight, successfully established a cisplatin-induced AKI minipig model with a survival time exceeding 28 days, closely mimicking the clinical characteristics of typical AKI patients. Additionally, we discovered that multiple MSCs transplantations promoted renal function recovery more effectively than single transplantation via the renal subcapsular catheter. Furthermore, elevated levels of Kyn were observed in kidney during AKI, which activated the aryl hydrocarbon receptor (AhR)-mediated NF-κB/NLRP3/IL-1β signaling pathway in tubular epithelial cells, thereby exacerbating inflammatory injury.

CONCLUSIONS

Ultrasound-guided renal subcapsular transplantation of mesenchymal stem cells is a safe and effective therapeutic approach for AKI, with the potential to bring about significant clinical advancements in the future.

Scaling factors to inform in vitro-in vivo extrapolation from preclinical and livestock animals: state of the field and recommendations for development of missing data

The use of in-vitro-in-vivo physiologically based pharmacokinetic (IVIVE-PBPK) modeling approaches assists for prediction of first-in animal or human trials. These approaches are underpinned by the scaling factors: microsomal protein per gram (MPPG) and cytosolic protein per gram (CPPG). In addition, IVIVE-PBPK has significant application in the reduction and refinement of live animal models in research. While human scaling factors are well-defined, many preclinical and livestock species remain poorly elucidated or uncharacterized. The MPPG parameter for liver (MPPGL) is the best characterized across all species and is well-defined for mouse, rat, and dog models. The MPPG parameters for Kidney (MPPGK) and intestine (MPPGI), are however; relatively indefinite for most species. Similarly, CPPG scaling factors for liver, kidney, and intestine (CPPGL/CPPGK/CPPGI) are generally sparse in all species. In addition to generation of mathematical values for scaling factors, methodological and animal-specific considerations, such as age, sex, and strain differences, have not yet been comprehensively described. Here, we review the current state-of-the-field for microsomal and cytosolic scaling factors, including highlighting areas that may need further description and development, with the intention of drawing attention to key knowledge gaps. The intention is to promote improved accuracy and precision in IVIVE-PBPK, concordance between laboratories, and stimulate work in underserved, but increasingly vital areas.

Temporary bilateral clamping of renal arteries induces ischemia-reperfusion: A new pig model of acute kidney injury using total intravenous anesthesia

Ischemia-reperfusion (IR) is a leading cause of acute kidney injury (AKI), and pigs are commonly used in preclinical AKI models. However, existing models often vary in the methods used to induce ischemia, and the resulting AKI tends to be mild-to-moderate. Moreover, follow-up is often performed under volatile anesthesia, which, in contrast to total intravenous anesthesia (TIVA), can induce malignant hyperthermia and cause hemodynamic instability. Here we present a novel surgical model of IR-induced AKI using bilateral renal artery clamping under TIVA. Anesthesia was induced via TIVA with diazepam, ketamine, and morphine. After retroperitoneal exposure, the renal arteries were isolated and clamped with a plastic tube for 90 min, followed by 8 h of reperfusion. The IR group (n = 6) was compared with a Sham group (n = 5) that underwent the same procedure without IR. The IR group developed moderate-to-severe AKI as evidenced by reduced glomerular filtration, a 158% increase in plasma creatinine versus 21% in the Sham group, and elevated neutrophil gelatinase-associated lipocalin levels (+280% in IR vs. 0% in Sham), indicating tubular injury. Histopathology confirmed these findings. Thus, this preclinical model successfully induced moderate-to-severe AKI in pigs. The TIVA anesthetic protocol offered several advantages compared to halogenated gas anesthesia.

Hydrogen gas inhalation ameliorates glomerular enlargement after hypoxic-ischemic insult in asphyxiated piglet model

Acute kidney injury (AKI) has been reported to occur in 30-70% of asphyxiated neonates. Hydrogen (H2) gas became a major research focus in neonatal medicine after the identification of its robust antioxidative properties. However, the ability of H2 gas to ameliorate AKI is unknown. We examined histopathological injuries in the piglet renal cortex on day 5 after a hypoxic-ischemic (HI) insult and if H2 gas can alleviate kidney injuries. Twenty piglets were divided into three groups: no insult (Control, n = 6), HI insult alone (HI, n = 8), and HI insult with H2 gas ventilation (HI-H2, 2.1-2.7% for 24 h, n = 6). The total glomerular cell count was significantly higher in the HI group than in the other groups, with no difference between the HI-H2 and control groups. Proximal tubular lumen narrowing was significantly increased in the HI group versus control, but not in the HI-H2 group. In this piglet model, glomerular enlargement with an increase in glomerular cell number due to tubular lumen narrowing was observed on day 5 after HI insult. H2 gas effectively suppressed this glomerular cell increase and tubular lumen narrowing.

Transplantation of decellularized porcine kidney grafts repopulated with primary human cells demonstrates filtration function in pigs

BACKGROUND

End-stage renal disease is a growing global health issue, disproportionately impacting low- and middle-income countries. While kidney transplantation remains the best treatment for end-stage renal disease, access to this treatment modality is limited by chronic donor organ shortages. To address this critical need, we are developing transplantable bioengineered kidney grafts.

METHODS

Podocyte differentiation was achieved in adherent monoculture through Wnt and TGF-β inhibition with IWR-1 and SB431542, respectively. Podocytes along with endothelial cells were then used to recapitulate glomeruli within decellularized porcine kidney scaffolds to generate bioengineered kidneys grafts. These bioengineered kidney grafts were functionally assessed via normothermic perfusion which compared kidney grafts recellularized with only endothelial cells as a control to bi-culture kidney grafts comprised of endothelial cells and podocytes. Heterotopic implantation further tested bi-culture kidney graft function over 3 successive implant sessions with 1-2 grafts per session.

RESULTS

We demonstrate the ability to source primary human podocytes at scale. Decellularized porcine kidney grafts repopulated with podocytes and endothelial cells exhibit native glomerular structure and display blood filtration capabilities during normothermic perfusion testing. Extending these findings to a clinically relevant model, bioengineered kidneys produce urine with indices of filtration when heterotopically implanted in pigs.

CONCLUSIONS

Our results showcase a human-scale, transplantable bioengineered kidney capable of performing requisite filtration function. This study reinforces the possibility for the bioengineering of transplantable human kidneys, which could someday provide increased and more equitable access to kidney grafts for the treatment of end-stage renal disease.

Renal-Targeted Drug Delivery by Chitosan Oligosaccharide Micelles with HSA-Enriched Protein Corona for the Treatment of Ischemia/Reperfusion-Induced Acute Kidney Injury

Renal-specific nanoparticulate drug delivery systems have shown great potential in reducing systemic side effects and improving the safety and efficacy of treatments for renal diseases. Here, stearic acid-grafted chitosan oligosaccharide (COS-SA) was synthesized as a renal-targeted carrier due to the high affinity of the 2-glucosamine moiety on COS to the megalin receptor expressed on renal proximal tubular epithelial cells. Specifically, COS-SA/CLT micelles were prepared by encapsulating celastrol (CLT) with COS-SA, and different proportions of human serum albumin (HSA) were then adsorbed onto its surface to explore the interaction between the protein corona and cationic polymeric micelles. Our results showed that a multilayered protein corona, consisting of an inner "hard" corona and an outer "soft" corona, was formed on the surface of COS-SA/CLT@HSA8, which was beneficial in preventing its recognition and phagocytosis by macrophages. The formation of HSA protein corona on COS-SA/CLT micelles also increased its accumulation in the renal tubules. Furthermore, the electropositivity of COS-SA/CLT micelles affected the conformation of adsorbed proteins to various degrees. During the adsorption process, the protein corona on the surface of COS-SA/CLT@HSA1 was partially denatured. Overall, COS-SA/CLT and COS-SA/CLT@HSA micelles demonstrated sufficient safety with renal targeting potential, providing a viable strategy for the management of ischemia/reperfusion-induced acute kidney injury.

Kidney/Aorta Ratio for Renal Morphometric Determination in Swine Subjected to Acute Kidney Injury Using an Optimized Surgical Model

This research aims to establish an experimental surgical model for access to the renal pedicle and kidney and to determine renal length measurement via the kidney/aorta ratio (K/AO) using ultrasound. Fifteen swine underwent ventral median celiotomy with a supraumbilical transverse incision to access the right and left renal pedicles and induce renal ischemia-reperfusion injury (IRR). The kidneys were evaluated using ultrasonography to standardize renal length, aortic diameter, and the K/AO. Assessment was performed at 2 time points: 1 h before and 24 h after the surgery to induce IRR. Blood and urine samples were collected to assess renal function. Histologic evaluation of kidney fragments was also conducted. The proposed abdominal cavity access method proved to be highly efficient for exposing the right and left renal pedicles and inducing IRR. Serum levels of urea, creatinine, calcium, and phosphorus, as well as levels of the urinary protein/urinary creatinine ratio and urinary GGT, did not show significant differences. Acute kidney injury was confirmed through histopathology. The mean lengths of the right and left kidneys were 82.63 and 87.64 mm, respectively. The values of the right and left K/AO were 9.81 and 10.38, respectively. There was no statistically significant difference in the K/AO ratio before and after IRR. The proposed surgical model allowed surgical intervention on the renal pedicles without intra- or postoperative complications. Furthermore, the K/AO could be measured through ultrasonography, establishing a reference for healthy animals.

Comparing Gut Microbial Composition and Functional Adaptations between SPF and Non-SPF Pigs

The gut microbiota is a key factor significantly impacting host health by influencing metabolism and immune function. Its composition can be altered by genetic factors, as well as environmental factors such as the host's surroundings, diet, and antibiotic usage. This study aims to examine how the characteristics of the gut microbiota in pigs, used as source animals for xenotransplantation, vary depending on their rearing environment. We compared the diversity and composition of gut microbiota in fecal samples from pigs raised in specific pathogen-free (SPF) and conventional (non-SPF) facilities. The 16S RNA metagenome sequencing results revealed that pigs raised in non-SPF facilities exhibited greater gut microbiota diversity compared to those in SPF facilities. Genera such as Streptococcus and Ruminococcus were more abundant in SPF pigs compared to non-SPF pigs, while Blautia, Bacteroides, and Roseburia were only observed in SPF pigs. Conversely, Prevotella was exclusively present in non-SPF pigs. It was predicted that SPF pigs would show higher levels of processes related to carbohydrate and nucleotide metabolism, and environmental information processing. On the other hand, energy and lipid metabolism, as well as processes associated with genetic information, cell communication, and diseases, were predicted to be more active in the gut microbiota of non-SPF pigs. This study provides insights into how the presence or absence of microorganisms, including pathogens, in pig-rearing facilities affects the composition and function of the pigs' gut microbiota. Furthermore, this serves as a reference for tracing whether xenotransplantation source pigs were maintained in a pathogen-controlled environment.

Robust Rat and Mouse Models of Bilateral Renal Ischemia Reperfusion Injury

BACKGROUND/AIM

Acute and chronic kidney diseases are a major contributor to morbidity and mortality worldwide, with no specific treatments currently available for these. To enable understanding the pathophysiology of and testing novel treatments for acute and chronic kidney disease, a suitable in vivo model of kidney disease is essential. In this article, we describe two reliable rodent models (rats and mice) of efficacious kidney injury displaying acute to chronic kidney injury progression, which is also reversible through novel therapeutic strategies such as ischemic preconditioning (IPC).

MATERIALS AND METHODS

We utilized adult male Lewis rats and adult male wildtype (C57BL/6) mice, performed a midline laparotomy, and induced warm ischemia to both kidneys by bilateral clamping of both renal vascular pedicles for a set time, to mimic the hypoxic etiology of disease commonly found in kidney injury.

RESULTS

Bilateral ischemia reperfusion injury caused marked structural and functional kidney injury as exemplified by histology damage scores, serum creatinine levels, and kidney injury biomarker levels in both rodents. Furthermore, this effect displayed a dose-dependent response in the mouse model.

CONCLUSION

These rodent models of bilateral kidney IRI are reliable, reproducible, and enable detailed mechanistic study of the underlying pathophysiology of both acute and chronic kidney disease. They have been carefully optimised for single operator use with a strong track record of training both surgically trained and surgically naïve operators.

The degree of aortic occlusion in the setting of trauma alters the extent of acute kidney injury associated with mitochondrial preservation

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is used to control noncompressible hemorrhage not addressed with traditional tourniquets. However, REBOA is associated with acute kidney injury (AKI) and subsequent mortality in severely injured trauma patients. Here, we investigated how the degree of aortic occlusion altered the extent of AKI in a porcine model. Female Yorkshire-cross swine (n = 16, 68.1 ± 0.7 kg) were anesthetized and had carotid and bilateral femoral arteries accessed for REBOA insertion and distal and proximal blood pressure monitoring. Through a laparotomy, a 6-cm liver laceration was performed and balloon inflation was performed in zone 1 of the aorta for 90 min, during which animals were randomized to target distal mean arterial pressures of 25 or 45 mmHg via balloon volume adjustment. Blood draws were taken at baseline, end of occlusion, and time of death, at which point renal tissues were harvested 6 h after balloon deflation for histological and molecular analyses. Renal blood flow was lower in the 25-mmHg group (48.5 ± 18.3 mL/min) than in the 45-mmHg group (177.9 ± 27.2 mL/min) during the occlusion phase, which recovered and was not different after balloon deflation. AKI was more severe in the 25-mmHg group, as evidenced by circulating creatinine, blood urea nitrogen, and urinary neutrophil gelatinase-associated lipocalin. The 25-mmHg group had increased tubular necrosis, lower renal citrate synthase activity, increased tissue and circulating syndecan-1, and elevated systemic inflammatory cytokines. The extent of renal ischemia-induced AKI is associated with the magnitude of mitochondrial biomass and systemic inflammation, highlighting potential mechanistic targets to combine with partial REBOA strategies to prevent AKI.NEW & NOTEWORTHY Large animal models of ischemia-reperfusion acute kidney injury (IR-AKI) are lacking. This report establishes a titratable IR-AKI model in swine in which a balloon catheter can be used to alter distal pressures experienced by the kidney, thus controlling renal blood flow. Lower blood flow results in greater renal dysfunction and structural damage, as well as lower mitochondrial biomass, elevated systemic inflammation, and vascular dysfunction.

Enhanced STAT3/PIK3R1/mTOR signaling triggers tubular cell inflammation and apoptosis in septic-induced acute kidney injury: implications for therapeutic intervention

Septic acute kidney injury (AKI) is a severe form of renal dysfunction associated with high morbidity and mortality rates. However, the pathophysiological mechanisms underlying septic AKI remain incompletely understood. Herein, we investigated the signaling pathways involved in septic AKI using the mouse models of lipopolysaccharide (LPS) treatment and cecal ligation and puncture (CLP). In these models, renal inflammation and tubular cell apoptosis were accompanied by the aberrant activation of the mechanistic target of rapamycin (mTOR) and the signal transducer and activator of transcription 3 (STAT3) signaling pathways. Pharmacological inhibition of either mTOR or STAT3 significantly improved renal function and reduced apoptosis and inflammation. Interestingly, inhibition of STAT3 with pharmacological inhibitors or small interfering RNA blocked LPS-induced mTOR activation in renal tubular cells, indicating a role of STAT3 in mTOR activation. Moreover, knockdown of STAT3 reduced the expression of the phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1/p85α), a key subunit of the phosphatidylinositol 3-kinase for AKT and mTOR activation. Chromatin immunoprecipitation assay also proved the binding of STAT3 to PIK3R1 gene promoter in LPS-treated kidney tubular cells. In addition, knockdown of PIK3R1 suppressed mTOR activation during LPS treatment. These findings highlight the dysregulation of mTOR and STAT3 pathways as critical mechanisms underlying the inflammatory and apoptotic phenotypes observed in renal tubular cells during septic AKI, suggesting the STAT3/ PIK3R1/mTOR pathway as a therapeutic target of septic AKI.

Renal Embolization-Induced Uremic Swine Model for Assessment of Next-Generation Implantable Hemodialyzers

Reliable models of renal failure in large animals are critical to the successful translation of the next generation of renal replacement therapies (RRT) into humans. While models exist for the induction of renal failure, none are optimized for the implantation of devices to the retroperitoneal vasculature. We successfully piloted an embolization-to-implantation protocol enabling the first implant of a silicon nanopore membrane hemodialyzer (SNMHD) in a swine renal failure model. Renal arterial embolization is a non-invasive approach to near-total nephrectomy that preserves retroperitoneal anatomy for device implants. Silicon nanopore membranes (SNM) are efficient blood-compatible membranes that enable novel approaches to RRT. Yucatan minipigs underwent staged bilateral renal arterial embolization to induce renal failure, managed by intermittent hemodialysis. A small-scale arteriovenous SNMHD prototype was implanted into the retroperitoneum. Dialysate catheters were tunneled externally for connection to a dialysate recirculation pump. SNMHD clearance was determined by intermittent sampling of recirculating dialysate. Creatinine and urea clearance through the SNMHD were 76-105 mL/min/m2 and 140-165 mL/min/m2, respectively, without albumin leakage. Normalized creatinine and urea clearance measured in the SNMHD may translate to a fully implantable clinical-scale device. This pilot study establishes a path toward therapeutic testing of the clinical-scale SNMHD and other implantable RRT devices.

Dynamic cellular changes in acute kidney injury caused by different ischemia time

Ischemia reperfusion injury (IRI), often related to surgical procedures, is one of the important causes of acute kidney injury (AKI). To decipher the dynamic process of AKI caused by IRI (with prolonged ischemia phase), we performed single-cell RNA sequencing (scRNA-seq) of clinically relevant IRI murine model with different ischemic intervals. We discovered that Slc5a2^hi proximal tubular cells were susceptible to AKI and highly expressed neutral amino acid transporter gene Slc6a19, which was dramatically decreased over the time course. With the usage of mass spectrometry-based metabolomic analysis, we detected that the level of neutral amino acid isoleucine dropped off in AKI mouse plasma metabolites. And the reduction of plasma isoleucine was also verified in patients with cardiac surgery-associated acute kidney injury (CSA-AKI). The findings advanced the understanding of dynamic process of AKI and introduced reduction of isoleucine as a potential biomarker for CSA-AKI.

Protective effect of sacubitril/valsartan (Entresto) on kidney function and filtration barrier injury in a porcine model of partial nephrectomy

Kidney surgery often includes organ ischaemia with a risk of acute kidney injury. The present study tested if treatment with the combined angiotensin II-angiotensin II receptor type 1 and neprilysin blocker Entresto (LCZ696, sacubitril/valsartan) protects filtration barrier and kidney function after ischaemia and partial nephrectomy (PN) in pigs. Single kidney glomerular filtration rate (GFR) by technetium-99m diethylene-triamine-pentaacetate clearance was validated (n = 6). Next, four groups of pigs were followed for 15 days (n = 24) after PN (one-third right kidney, 60 min ischaemia) + Entresto (49/51 mg/day; n = 8), PN + vehicle (n = 8), sham + Entresto (49/51 mg/day; n = 4) and sham + vehicle (n = 4). GFR, diuresis and urinary albumin were measured at baseline and from each kidney after 15 days. The sum of single-kidney GFR (right 25 ± 6 mL/min, left 31 ± 7 mL/min) accounted for the total GFR (56 ± 14 mL/min). Entresto had no effect on baseline blood pressure, p-creatinine, mid-regional pro-atrial natriuretic peptide (MR-proANP), heart rate and diuresis. After 15 days, Entresto increased GFR in the uninjured kidney (+23 ± 6 mL/min, P < .05) and reduced albuminuria from both kidneys. In the sham group, plasma MR-proANP was not altered by Entresto; it increased to similar levels 2 h after surgery with and without Entresto. Fractional sodium excretion increased with Entresto. Kidney histology and kidney injury molecule-1 in cortex tissue were not different. In conclusion, Entresto protects the filtration barrier and increases the functional adaptive response of the uninjured kidney.

Multi-Omics Techniques Make it Possible to Analyze Sepsis-Associated Acute Kidney Injury Comprehensively

Sepsis-associated acute kidney injury (SA-AKI) is a common complication in critically ill patients with high morbidity and mortality. SA-AKI varies considerably in disease presentation, progression, and response to treatment, highlighting the heterogeneity of the underlying biological mechanisms. In this review, we briefly describe the pathophysiology of SA-AKI, biomarkers, reference databases, and available omics techniques. Advances in omics technology allow for comprehensive analysis of SA-AKI, and the integration of multiple omics provides an opportunity to understand the information flow behind the disease. These approaches will drive a shift in current paradigms for the prevention, diagnosis, and staging and provide the renal community with significant advances in precision medicine in SA-AKI analysis.

Modeling Cisplatin-Induced Kidney Injury to Increase Translational Potential

BACKGROUND

Cisplatin-induced kidney injury is a major challenge hindering treatment of cancer patients. Thirty percent of patients treated with cisplatin develop acute kidney injury (AKI). Even patients that do not develop AKI are at risk for long-term decline in renal function and development of chronic kidney disease. Despite researchers' best efforts, no therapeutic agents to treat or prevent cisplatin-induced kidney injury have made it past phase 2 clinical trials.

SUMMARY

Modeling cisplatin-induced kidney injury in rodents has primarily been done using a single, high-dose model of injury. Newer models of injury have utilized repeated, low, or intermediate doses of cisplatin to incorporate the study of maladaptive repair processes following a renal insult. We believe that utilization of all these models is important to understand and treat the diverse types of cisplatin-induced kidney injury patients develop in the clinic. Incorporating comorbidities such as cancer and development of large animal models is also vital to increasing the human relevance of our studies.

KEY MESSAGES

Utilizing multiple dosing models of cisplatin-induced kidney injury, including relevant comorbidities and biological variables, and development of large animal models will increase the translational potential of preclinical studies.

Inhibition of polycomb repressive complex 2 by targeting EED protects against cisplatin-induced acute kidney injury

Polycomb repressive complex 2 (PRC2) is a multicomponent complex with methyltransferase activity that catalyzes trimethylation of histone H3 at lysine 27 (H3K27me3). Interaction of the epigenetic reader protein EED with EZH2, a catalytic unit of PRC, allosterically stimulates PRC2 activity. In this study, we investigated the role and underlying mechanism of the PRC2 in acute kidney injury (AKI) by using EED226, a highly selective PRC2 inhibitor, to target EED. Administration of EED226 improved renal function, attenuated renal pathological changes, and reduced renal tubular cell apoptosis in a murine model of cisplatin‐induced AKI. In cultured renal epithelial cells, treatment with either EED226 or EED siRNA also ameliorated cisplatin‐induced apoptosis. Mechanistically, EED226 treatment inhibited cisplatin‐induced phosphorylation of p53 and FOXO3a, two transcriptional factors contributing to apoptosis, and preserved expression of Sirtuin 3 and PGC1α, two proteins associated with mitochondrial protection in vivo and in vitro. EED226 was also effective in enhancing renal tubular cell proliferation, suppressing expression of multiple inflammatory cytokines, and reducing infiltration of macrophages to the injured kidney. These data suggest that inhibition of the PRC2 activity by targeting EED can protect against cisplatin‐induced AKI by promoting the survival and proliferation of renal tubular cells and inhibiting inflammatory response.

Mesenchymal Stem Cells-Derived Exosomes Ameliorate Ischemia/Reperfusion Induced Acute Kidney Injury in a Porcine Model

Exosomes are membrane-enclosed vesicles secreted by cells, containing a variety of biologically active ingredients including proteins, nucleic acids and lipids. In this study, we investigated the therapeutic effects of the exosomes and underlying mechanisms in a miniature pig model of ischemia/reperfusion-induced acute kidney injury (I/R-AKI). The exosomes were extracted from cultured human umbilical cord derived mesenchymal stem cells (hUC-MSCs) and infused into a miniature pig model of I/R AKI. Our results showed that 120 min of unilateral ischemia followed by reperfusion and contralateral nephrectomy resulted in renal dysfunction, severe kidney damage, apoptosis and necroptosis. Intravenous infusion of one dose of exosomes collected from about 4 × 108 hUC-MSCs significantly improved renal function and reduced apoptosis and necroptosis. Administration of hUC-MSC exosomes also reduced the expression of some pro-inflammatory cytokines/chemokines, decreased infiltration of macrophages to the injured kidneys and suppressed the phosphorylation of nuclear factor-κB and signal transducer and activator of transcription 3, two transcriptional factors related to inflammatory regulation. Moreover, hUC-MSC exosomes could promote proliferation of renal tubular cells, angiogenesis and upregulation of Klotho and Bone Morphogenetic Protein 7, two renoprotective molecules and vascular endothelial growth factor A and its receptor. Collectively, our results suggest that injection of hUC-MSC exosomes could ameliorate I/R-AKI and accelerate renal tubular cell repair and regeneration, and that hUC-MSC exosomes may be used as a potential biological therapy for Acute kidney injury patients.

Temporal and sex-dependent gene expression patterns in a renal ischemia-reperfusion injury and recovery pig model

Men are more prone to acute kidney injury (AKI) and chronic kidney disease (CKD), progressing to end-stage renal disease (ESRD) than women. Severity and capacity to regenerate after AKI are important determinants of CKD progression, and of patient morbidity and mortality in the hospital setting. To determine sex differences during injury and recovery we have generated a female and male renal ischemia/reperfusion injury (IRI) pig model, which represents a major cause of AKI. Although no differences were found in blood urea nitrogen (BUN) and serum creatinine (SCr) levels between both sexes, females exhibited higher mononuclear infiltrates at basal and recovery, while males showed more tubular damage at injury. Global transcriptomic analyses of kidney biopsies from our IRI pig model revealed a sexual dimorphism in the temporal regulation of genes and pathways relevant for kidney injury and repair, which was also detected in human samples. Enrichment analysis of gene sets revealed five temporal and four sexual patterns governing renal IRI and recovery. Overall, this study constitutes an extensive characterization of the time and sex differences occurring during renal IRI and recovery at gene expression level and offers a template of translational value for further study of sexual dimorphism in kidney diseases.

Folic acid-induced animal model of kidney disease

The kidneys are a vital organ that is vulnerable to both acute kidney injury (AKI) and chronic kidney disease (CKD) which can be caused by numerous risk factors such as ischemia, sepsis, drug toxicity and drug overdose, exposure to heavy metals, and diabetes. In spite of the advances in our understanding of the pathogenesis of AKI and CKD as well AKI transition to CKD, there is still no available therapeutics that can be used to combat kidney disease effectively, highlighting an urgent need to further study the pathological mechanisms underlying AKI, CKD, and AKI progression to CKD. In this regard, animal models of kidney disease are indispensable. This article reviews a widely used animal model of kidney disease, which is induced by folic acid (FA). While a low dose of FA is nutritionally beneficial, a high dose of FA is very toxic to the kidneys. Following a brief description of the procedure for disease induction by FA, major mechanisms of FA-induced kidney injury are then reviewed, including oxidative stress, mitochondrial abnormalities such as impaired bioenergetics and mitophagy, ferroptosis, pyroptosis, and increased expression of fibroblast growth factor 23 (FGF23). Finally, application of this FA-induced kidney disease model as a platform for testing the efficacy of a variety of therapeutic approaches is also discussed. Given that this animal model is simple to create and is reproducible, it should remain useful for both studying the pathological mechanisms of kidney disease and identifying therapeutic targets to fight kidney disease.