Progressive Renal Disease Established by Renin-Coding Adeno-Associated Virus-Driven Hypertension in Diverse Diabetic Models

Endothelial Dysfunction in the Tubule Area Accelerates the Progression of Early Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease. Therefore, understanding the molecular regulatory mechanisms underlying the pathogenesis of DKD is imperative. In this study, we aimed to explore the molecular mechanisms of tubule region endothelial dysfunction in early DKD. Early-stage DKD model was established in 16-week-old female db/db mice for 16 weeks. Body weight, glucose level, and urine albumin-to-creatinine ratio (UACR) were measured. Hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) staining were performed to evaluate pathological lesions. RNA sequencing data of the kidneys and integrated publicly available single-cell and spatial transcriptome datasets were used to investigate the mechanism of endothelial dysfunction. There was a significant increase in body weight (p = 0.001), glucose levels (p=0.0008), and UACR (p=0.006) in db/db mice compared with db/m mice. H&E and PAS staining showed that vacuolar lesions and protein casts of tubules were the major histopathological changes observed in early-stage DKD mice. The apoptotic pathway in endothelial cells was notably activated in DKD, and Thbs1 was identified as the central gene involved in this apoptotic process. Deconvolution of the cell composition in the RNA sequencing data showed a decrease in the proportion of endothelial cells in the DKD mice. Further analysis of the activity and regulatory network of transcription factors showed that Creb1 was activated in both mouse and human early-stage DKD, suggesting that Creb1 activation may be involved in early kidney injury. The endothelial cell apoptotic pathway is activated in DKD, and the proportion of endothelial cells was reduced in the DKD mice, which is significantly associated with Thbs1. Keywords: Diabetic kidney disease, Endothelial dysfunction, RNA sequencing,Thbs1, Creb1.

Exploring potential targets for natural product therapy of DN: the role of SUMOylation

Diabetic nephropathy (DN) is a common and serious micro-vascular complication of diabetes and a leading cause of end-stage renal disease globally. This disease primarily affects middle-aged and elderly individuals, especially those with a diabetes history of over 10 years and poor long-term blood glucose control. Small ubiquitin-related modifiers (SUMOs) are a group of reversible post-translational modifications of proteins that are widely expressed in eukaryotes. SUMO proteins intervene in the progression of DN by modulating various signaling cascades, such as Nrf2-mediated oxidative stress, NF-κB, TGF-β, and MAPK pathways. Recent advancements indicate that natural products regulating SUMOylation hold promise as targets for intervening in DN. In a previous article published in 2022, we reviewed the mechanisms by which SUMOylation intervenes in renal fibrosis and presented a summary of some natural products with therapeutic potential. Therefore, this paper will focus on DN. The aim of this review is to elucidate the mechanism of action of SUMOylation in DN and related natural products with therapeutic potential, thereby summarising the targets and candidate natural products for the treatment of DN through the modulation of SUMOylation, such as ginkgolic acid, ginkgolide B, resveratrol, astragaloside IV, etc., and highlighting that natural product-mediated modulation of SUMOylation is a potential therapeutic strategy for the treatment of DN as a potential therapeutic strategy.

VEPTP inhibition with an extracellular domain targeting antibody did not restore albuminuria in a mouse model of diabetic kidney disease

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease. DKD is a heterogeneous disease with complex pathophysiology where early endothelial dysfunction is associated with disease progression. The Tie2 receptor and Angiopoietin 1 and 2 ligands are critical for maintaining endothelial cell permeability and integrity. Tie2 signaling is negatively regulated by the endothelial specific transmembrane receptor Vascular Endothelial Protein Tyrosine Phosphatase (VEPTP). Genetic deletion of VEPTP protects from hypertension and diabetes induced renal injury in a mouse model of DKD. Here, we show that VEPTP inhibition with an extracellular domain targeting VEPTP antibody induced Tie2 phosphorylation and improved VEGF-A induced vascular permeability both in vitro and in vivo. Treatment with the VEPTP blocking antibody decreased the renal expression of endothelial activation markers (Angpt2, Edn1, and Icam1) but failed to improve kidney function in db/db uninephrectomized ReninAAV DKD mice.

Urinary stem cell-derived exocrine circRNA ATG7 regulates the SOCS1/STAT3 signaling pathway through miR-4500, inhibits M1 macrophage polarization, and alleviates the progression of diabetes nephropathy

OBJECTIVE

The etiopathogenesis of diabetes nephropathy (DN) has not yet been fully clarified. Finding effective treatments to prevent renal failure in DN patients has become the main focus of research in recent years. Circular RNA (circRNA) has been shown to play a momentous role in DN progression. Based on this, we aimed to investigate the potential mechanism by which urine-derived stem cell (USC)-derived exosome circRNA ATG7 (Exo-ATG7) mediates DN progression.

METHODS

Exosomes from USCs were isolated and identified. The DN rat model was established by intraperitoneally injecting 60 mg/kg streptozotocin. The protein expression levels were measured by Western blot and immunofluorescence. HE and Masson staining were used to evaluate renal injury, and the expression of related genes was detected by RT-qPCR.

RESULTS

CircRNA ATG7 was significantly downregulated in the DN rat model, and the extracellular vesicles of USCs improved renal function and reduced inflammation in DN rats. However, after knocking down the USCs-derived exosome circRNA ATG7, improvement and therapeutic effect on renal function in DN rats were lost. In addition, overexpression of ATG7 facilitated the switching of macrophages from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype both in vivo and in vitro. Mechanistically, upregulation of circRNA ATG7 expression can alleviate renal damage in DN rats. Importantly, the USCs-derived exosome circRNA ATG7 promotes macrophage M2 polarization by regulating the SOCS1/STAT3 signaling pathway through miR-4500. In addition, animal experiments also confirmed that after knocking down ATG7 in USC cells, the extracted exosome-treated DN rats could weaken the therapeutic effect of USC exosomes.

CONCLUSION

Our research results indicate that USC-derived exosomal circRNA ATG7 facilitates macrophage phenotype switching from M1 to M2 through the SOCS1/STAT3 signaling pathway mediated by miR-4500, thereby inhibiting DN progression.

Recessive variants in the intergenic NOS1AP-C1orf226 locus cause monogenic kidney disease responsive to anti-proteinuric treatment

In genetic disease, an accurate expression landscape of disease genes and faithful animal models will enable precise genetic diagnoses and therapeutic discoveries, respectively. We previously discovered that variants in NOS1AP , encoding nitric oxide synthase 1 (NOS1) adaptor protein, cause monogenic nephrotic syndrome (NS). Here, we determined that an intergenic splice product of N OS1AP / Nos1ap and neighboring C1orf226/Gm7694 , which precludes NOS1 binding, is the predominant isoform in mammalian kidney transcriptional and proteomic data. Gm7694 -/- mice, whose allele exclusively disrupts the intergenic product, developed NS phenotypes. In two human NS subjects, we identified causative NOS1AP splice variants, including one predicted to abrogate intergenic splicing but initially misclassified as benign based on the canonical transcript. Finally, by modifying genetic background, we generated a faithful mouse model of NOS1AP -associated NS, which responded to anti-proteinuric treatment. This study highlights the importance of intergenic splicing and a potential treatment avenue in a mendelian disorder.

Understanding interleukin 11 as a disease gene and therapeutic target

Interleukin 11 (IL11) is an elusive member of the IL6 family of cytokines. While initially thought to be a haematopoietic and cytoprotective factor, more recent data show instead that IL11 is redundant for haematopoiesis and toxic. In this review, the reasons that led to the original misunderstandings of IL11 biology, which are now understandable, are explained with particular attention on the use of recombinant human IL11 in mice and humans. Following tissue injury, as part of an evolutionary ancient homeostatic response, IL11 is secreted from damaged mammalian cells to signal via JAK/STAT3, ERK/P90RSK, LKB1/mTOR and GSK3β/SNAI1 in autocrine and paracrine. This activates a program of mesenchymal transition of epithelial, stromal, and endothelial cells to cause inflammation, fibrosis, and stalled endogenous tissue repair, leading to organ failure. The role of IL11 signalling in cell- and organ-specific pathobiology is described, the large unknowns about IL11 biology are discussed and the promise of targeting IL11 signalling as a therapeutic approach is reviewed.

The crosstalk between glomerular endothelial cells and podocytes controls their responses to metabolic stimuli in diabetic nephropathy

In diabetic nephropathy (DN), glomerular endothelial cells (GECs) and podocytes undergo pathological alterations, which are influenced by metabolic changes characteristic of diabetes, including hyperglycaemia (HG) and elevated methylglyoxal (MGO) levels. However, it remains insufficiently understood what effects these metabolic factors have on GEC and podocytes and to what extent the interactions between the two cell types can modulate these effects. To address these questions, we established a co-culture system in which GECs and podocytes were grown together in close proximity, and assessed transcriptional changes in each cell type after exposure to HG and MGO. We found that HG and MGO had distinct effects on gene expression and that the effect of each treatment was markedly different between GECs and podocytes. HG treatment led to upregulation of "immediate early response" genes, particularly those of the EGR family, as well as genes involved in inflammatory responses (in GECs) or DNA replication/cell cycle (in podocytes). Interestingly, both HG and MGO led to downregulation of genes related to extracellular matrix organisation in podocytes. Crucially, the transcriptional responses of GECs and podocytes were dependent on their interaction with each other, as many of the prominently regulated genes in co-culture of the two cell types were not significantly changed when monocultures of the cells were exposed to the same stimuli. Finally, the changes in the expression of selected genes were validated in BTBR ob/ob mice, an established model of DN. This work highlights the molecular alterations in GECs and podocytes in response to the key diabetic metabolic triggers HG and MGO, as well as the central role of GEC-podocyte crosstalk in governing these responses.

Contribution of animal models to diabetes research: Its history, significance, and translation to humans

Diabetes mellitus is still expanding globally and is epidemic in developing countries. The combat of this plague has caused enormous economic and social burdens related to a lowered quality of life in people with diabetes. Despite recent significant improvements of life expectancy in patients with diabetes, there is still a need for efforts to elucidate the complexities and mechanisms of the disease processes to overcome this difficult disorder. To this end, the use of appropriate animal models in diabetes studies is invaluable for translation to humans and for the development of effective treatment. In this review, a variety of animal models of diabetes with spontaneous onset in particular will be introduced and discussed for their implication in diabetes research.

Integrating basic science with translational research: the 13th International Podocyte Conference 2021

The 13th International Podocyte Conference was held in Manchester, UK, and online from July 28 to 30, 2021. Originally planned for 2020, this biannual meeting was postponed by a year because of the coronavirus disease 2019 (COVID-19) pandemic and proceeded as an innovative hybrid meeting. In addition to in-person attendance, online registration was offered, and this attracted 490 conference registrations in total. As a Podocyte Conference first, a day for early-career researchers was introduced. This premeeting included talks from graduate students and postdoctoral researchers. It gave early career researchers the opportunity to ask a panel, comprising academic leaders and journal editors, about career pathways and the future for podocyte research. The main meeting over 3 days included a keynote talk and 4 focused sessions each day incorporating invited talks, followed by selected abstract presentations, and an open panel discussion. The conference concluded with a Patient Day, which brought together patients, clinicians, researchers, and industry representatives. The Patient Day was an interactive and diverse day. As well as updates on improving diagnosis and potential new therapies, the Patient Day included a PodoArt competition, exercise and cooking classes with practical nutrition advice, and inspirational stories from patients and family members. This review summarizes the exciting science presented during the 13th International Podocyte Conference and demonstrates the resilience of researchers during a global pandemic.

Nephroprotective Effects of Semaglutide as Mono- and Combination Treatment with Lisinopril in a Mouse Model of Hypertension-Accelerated Diabetic Kidney Disease

Background: Obesity, hyperglycemia and hypertension are critical risk factors for development of diabetic kidney disease (DKD). Emerging evidence suggests that glucagon-like peptide-1 receptor (GLP-1R) agonists improve cardiovascular and renal outcomes in type 2 diabetes patients. Here, we characterized the effect of the long-acting GLP-1R agonist semaglutide alone and in combination with an ACE inhibitor (lisinopril) in a model of hypertension-accelerated, advanced DKD facilitated by adeno-associated virus-mediated renin overexpression (ReninAAV) in uninephrectomized (UNx) female diabetic db/db mice. Methods: Female db/db mice received a single intravenous injection of ReninAAV 1 week prior to UNx. Six weeks post-nephrectomy, db/db UNx-ReninAAV mice were administered (q.d.) vehicle, semaglutide (30 nmol/kg, s.c.) or semaglutide (30 nmol/kg, s.c.) + lisinopril (30 mg/kg, p.o.) for 11 weeks. Endpoints included blood pressure, plasma/urine biochemistry, kidney histopathology and RNA sequencing. Results: Vehicle-dosed db/db UNx-ReninAAV mice developed hallmarks of DKD characterized by severe albuminuria and advanced glomerulosclerosis. Semaglutide robustly reduced hyperglycemia, hypertension and albuminuria concurrent with notable improvements in glomerulosclerosis severity, podocyte filtration slit density, urine/renal kidney injury molecule-1 (KIM-1) levels and gene expression markers of inflammation and fibrogenesis in db/db UNx-ReninAAV mice. Co-administration of lisinopril further ameliorated hypertension and glomerulosclerosis. Conclusions: Semaglutide improves disease hallmarks in the db/db UNx-ReninAAV mouse model of advanced DKD. Further benefits on renal outcomes were obtained by adjunctive antihypertensive standard of care. Collectively, our study supports the development of semaglutide for management of DKD.

Mapping the single-cell transcriptomic response of murine diabetic kidney disease to therapies

Diabetic kidney disease (DKD) occurs in ∼40% of patients with diabetes and causes kidney failure, cardiovascular disease, and premature death. We analyzed the response of a murine DKD model to five treatment regimens using single-cell RNA sequencing (scRNA-seq). Our atlas of ∼1 million cells revealed a heterogeneous response of all kidney cell types both to DKD and its treatment. Both monotherapy and combination therapies targeted differing cell types and induced distinct and non-overlapping transcriptional changes. The early effects of sodium-glucose cotransporter-2 inhibitors (SGLT2i) on the S1 segment of the proximal tubule suggest that this drug class induces fasting mimicry and hypoxia responses. Diabetes downregulated the spliceosome regulator serine/arginine-rich splicing factor 7 (Srsf7) in proximal tubule that was specifically rescued by SGLT2i. In vitro proximal tubule knockdown of Srsf7 induced a pro-inflammatory phenotype, implicating alternative splicing as a driver of DKD and suggesting SGLT2i regulation of proximal tubule alternative splicing as a potential mechanism of action for this drug class.

Epigenetics in the pathogenesis of diabetic nephropathy

Diabetic nephropathy (DN), which is a common microvascular complication with a high incidence in diabetic patients, greatly increases the mortality of patients. With further study on DN, it is found that epigenetics plays a crucial role in the pathophysiological process of DN. Epigenetics has an important impact on the development of DN through a variety of mechanisms, and promotes the generation and maintenance of metabolic memory, thus ultimately leading to a poor prognosis. In this review we discuss the methylation of DNA, modification of histone, and regulation of non-coding RNA involved in the progress of cell dysfunction, inflammation and fibrosis in the kidney, which ultimately lead to the deterioration of DN.

Integrative transcriptomic profiling of a mouse model of hypertension-accelerated diabetic kidney disease

The current understanding of molecular mechanisms driving diabetic kidney disease (DKD) is limited, partly due to the complex structure of the kidney. To identify genes and signalling pathways involved in the progression of DKD, we compared kidney cortical versus glomerular transcriptome profiles in uninephrectomized (UNx) db/db mouse models of early-stage (UNx only) and advanced [UNxplus adeno-associated virus-mediated renin-1 overexpression (UNx-Renin)] DKD using RNAseq. Compared to normoglycemic db/m mice, db/db UNx and db/db UNx-Renin mice showed marked changes in their kidney cortical and glomerular gene expression profiles. UNx-Renin mice displayed more marked perturbations in gene components associated with the activation of the immune system and enhanced extracellular matrix remodelling, supporting histological hallmarks of progressive DKD in this model. Single-nucleus RNAseq enabled the linking of transcriptome profiles to specific kidney cell types. In conclusion, integration of RNAseq at the cortical, glomerular and single-nucleus level provides an enhanced resolution of molecular signalling pathways associated with disease progression in preclinical models of DKD, and may thus be advantageous for identifying novel therapeutic targets in DKD.

Therapeutic effects of lisinopril and empagliflozin in a mouse model of hypertension-accelerated diabetic kidney disease

Hypertension is a critical comorbidity for progression of diabetic kidney disease (DKD). To facilitate the development of novel therapeutic interventions with the potential to control disease progression, there is a need to establish translational animal models that predict treatment effects in human DKD. The present study aimed to characterize renal disease and outcomes of standard of medical care in a model of advanced DKD facilitated by adeno-associated virus (AAV)-mediated renin overexpression in uninephrectomized (UNx) db/db mice. Five weeks after single AAV administration and 4 wk after UNx, female db/db UNx-ReninAAV mice received (PO, QD) vehicle, lisinopril (40 mg/kg), empagliflozin (20 mg/kg), or combination treatment for 12 wk (n = 17 mice/group). Untreated db/+ mice (n = 8) and vehicle-dosed db/db UNx-LacZAAV mice (n = 17) served as controls. End points included plasma, urine, and histomorphometric markers of kidney disease. Total glomerular numbers and individual glomerular volume were evaluated by whole kidney three-dimensional imaging analysis. db/db UNx-ReninAAV mice developed hallmarks of progressive DKD characterized by severe albuminuria, advanced glomerulosclerosis, and glomerular hypertrophy. Lisinopril significantly improved albuminuria, glomerulosclerosis, tubulointerstitial injury, and inflammation. Although empagliflozin alone had no therapeutic effect on renal endpoints, lisinopril and empagliflozin exerted synergistic effects on renal histological outcomes. In conclusion, the db/db UNx-ReninAAV mouse demonstrates good clinical translatability with respect to physiological and histological hallmarks of progressive DKD. The efficacy of standard of care to control hypertension and hyperglycemia provides a proof of concept for testing novel drug therapies in the model.NEW & NOTEWORTHY Translational animal models of diabetic kidney disease (DKD) are important tools in preclinical research and drug discovery. Here, we show that the standard of care to control hypertension (lisinopril) and hyperglycemia (empagliflozin) improves physiological and histopathological hallmarks of kidney disease in a mouse model of hypertension-accelerated progressive DKD. The findings substantiate hypertension and type 2 diabetes as essential factors in driving DKD progression and provide a proof of concept for probing novel drugs for potential nephroprotective efficacy in this model.

A systematic review and meta-analysis of cell-based interventions in experimental diabetic kidney disease

Regenerative, cell‐based therapy is a promising treatment option for diabetic kidney disease (DKD), which has no cure. To prepare for clinical translation, this systematic review and meta‐analysis summarized the effect of cell‐based interventions in DKD animal models and treatment‐related factors modifying outcomes. Electronic databases were searched for original investigations applying cell‐based therapy in diabetic animals with kidney endpoints (January 1998‐May 2019). Weighted or standardized mean differences were estimated for kidney outcomes and pooled using random‐effects models. Subgroup analyses tested treatment‐related factor effects for outcomes (creatinine, urea, urine protein, fibrosis, and inflammation). In 40 studies (992 diabetic rodents), therapy included mesenchymal stem/stromal cells (MSC; 61%), umbilical cord/amniotic fluid cells (UC/AF; 15%), non‐MSC (15%), and cell‐derived products (13%). Tissue sources included bone marrow (BM; 65%), UC/AF (15%), adipose (9%), and others (11%). Cell‐based therapy significantly improved kidney function while reducing injury markers (proteinuria, histology, fibrosis, inflammation, apoptosis, epithelial‐mesenchymal‐transition, oxidative stress). Preconditioning, xenotransplantation, and disease‐source approaches were effective. MSC and UC/AF cells had greater effect on kidney function while cell products improved fibrosis. BM and UC/AF tissue sources more effectively improved kidney function and proteinuria vs adipose or other tissues. Cell dose, frequency, and administration route also imparted different benefits. In conclusion, cell‐based interventions in diabetic animals improved kidney function and reduced injury with treatment‐related factors modifying these effects. These findings may aid in development of optimal repair strategies through selective use of cells/products, tissue sources, and dose administrations to allow for successful adaptation of this novel therapeutic in human DKD.

Effects of metabolic memory on inflammation and fibrosis associated with diabetic kidney disease: an epigenetic perspective

Diabetic kidney disease (DKD) is one of the most common microvascular complication of both type 1 (T1DM) and type 2 diabetes mellitus (T2DM), and the leading cause of end-stage renal disease (ESRD) worldwide. Persistent inflammation and subsequent chronic fibrosis are major causes of loss of renal function, which is associated with the progression of DKD to ESRD. In fact, DKD progression is affected by a combination of genetic and environmental factors. Approximately, one-third of diabetic patients progress to develop DKD despite intensive glycemic control, which propose an essential concept "metabolic memory." Epigenetic modifications, an extensively studied mechanism of metabolic memory, have been shown to contribute to the susceptibility to develop DKD. Epigenetic modifications also play a regulatory role in the interactions between the genes and the environmental factors. The epigenetic contributions to the processes of inflammation and fibrogenesis involved in DKD occur at different regulatory levels, including DNA methylation, histone modification and non-coding RNA modulation. Compared with genetic factors, epigenetics represents a new therapeutic frontier in understanding the development DKD and may lead to therapeutic breakthroughs due to the possibility to reverse these modifications therapeutically. Early recognition of epigenetic events and biomarkers is crucial for timely diagnosis and intervention of DKD, and for the prevention of the progression of DKD to ESRD. Herein, we will review the latest epigenetic mechanisms involved in the renal pathology of both type 1 (T1DN) and type 2 diabetic nephropathy (T2DN) and highlight the emerging role and possible therapeutic strategies based on the understanding of the role of epigenetics in DKD-associated inflammation and fibrogenesis.

IL-11 in cardiac and renal fibrosis: Late to the party but a central player

Fibrosis is a pathophysiological hallmark of cardiorenal disease. In the heart, fibrosis leads to contractile dysfunction and arrhythmias; in the kidney, it is the final common pathway for many diseases and predicts end-stage renal failure. Despite this, there are currently no specific anti-fibrotic treatments available for cardiac or renal disease. Recently and unexpectedly, IL-11 was found to be of major importance for cardiorenal fibroblast activation and fibrosis. In mouse models, IL-11 overexpression caused fibrosis of the heart and kidney while genetic deletion of Il11ra1 protected against fibrosis and preserved organ function. Neutralizing antibodies against IL-11 or IL-11RA have been developed that have anti-fibrotic activity in human fibroblasts and protect against fibrosis in murine models of disease. While IL-11 biology has been little studied and, we suggest, largely misunderstood, its autocrine activity in myofibroblasts appears non-redundant for fibrosis, which offers new opportunities to better understand and potentially target cardiorenal fibrosis.

Impact of sex on diabetic nephropathy and the renal transcriptome in UNx db/db C57BLKS mice

Diabetic nephropathy (DN) is associated with albuminuria and loss of kidney function and is the leading cause of end-stage renal disease. Despite evidence of sex-associated differences in the progression of DN in human patients, male mice are predominantly being used in preclinical DN research and drug development. Here, we compared renal changes in male and female uninephrectomized (UNx) db/db C57BLKS mice using immunohistochemistry and RNA sequencing. Male and female UNx db/db mice showed similar progression of type 2 diabetes, as assessed by obesity, hyperglycemia, and HbA1c. Progression of DN was also similar between sexes as assessed by kidney and glomerular hypertrophy as well as urine albumin-to-creatinine ratio being increased in UNx db/db compared with control mice. In contrast, kidney collagen III and glomerular collagen IV were increased only in female UNx db/db as compared with respective control mice but showed a similar tendency in male UNx db/db mice. Comparison of renal cortex transcriptomes by RNA sequencing revealed 66 genes differentially expressed (p < .01) in male versus female UNx db/db mice, of which 9 genes were located on the sex chromosomes. In conclusion, male and female UNx db/db mice developed similar hallmarks of DN pathology, suggesting no or weak sex differences in the functional and structural changes during DN progression.

A new, easily generated mouse model of diabetic kidney fibrosis

Our understanding of diabetic kidney disease pathogenesis has been hampered by the lack of easily generated pre-clinical animal models that faithfully recapitulate critical features of human disease. While most standard animal models develop manifestations of early stage diabetic injury such as hyperfiltration and mesangial matrix expansion, only a select few develop key late stage features such as interstitial fibrosis and reduced glomerular filtration rate. An underlying theme in these late stage disease models has been the addition of renin-angiotensin system hyperactivation, an important contributor to human disease pathogenesis. Widespread use of these models has been limited, however, as they are either labour intensive to generate, or have been developed in the rat, preventing the use of the many powerful genetic tools developed for mice. Here we describe the Akita^+/− Ren^+/− mouse, a new, easily generated murine model of diabetic kidney disease that develops many features of late stage human injury, including not only hyperglycemia, hypertension, and albuminuria, but also reduced glomerular filtration rate, glomerulosclerosis, and interstitial fibrosis.

Targeting VE-PTP phosphatase protects the kidney from diabetic injury

Diabetic nephropathy is a leading cause of kidney failure. VE-PTP phosphatase expression is increased in the endothelium of rodents with diabetes and hypertension. Genetic deletion of VE-PTP reduces kidney injury in diabetic mice, suggesting it may be a therapeutic target.

Diabetic nephropathy is a leading cause of end-stage kidney failure. Reduced angiopoietin-TIE2 receptor tyrosine kinase signaling in the vasculature leads to increased vascular permeability, inflammation, and endothelial cell loss and is associated with the development of diabetic complications. Here, we identified a mechanism to explain how TIE2 signaling is attenuated in diabetic animals. Expression of vascular endothelial protein tyrosine phosphatase VE-PTP (also known as PTPRB), which dephosphorylates TIE2, is robustly up-regulated in the renal microvasculature of diabetic rodents, thereby reducing TIE2 activity. Increased VE-PTP expression was dependent on hypoxia-inducible factor transcriptional activity in vivo. Genetic deletion of VE-PTP restored TIE2 activity independent of ligand availability and protected kidney structure and function in a mouse model of severe diabetic nephropathy. Mechanistically, inhibition of VE-PTP activated endothelial nitric oxide synthase and led to nuclear exclusion of the FOXO1 transcription factor, reducing expression of pro-inflammatory and pro-fibrotic gene targets. In sum, we identify inhibition of VE-PTP as a promising therapeutic target to protect the kidney from diabetic injury.

Pathological and Transcriptome Changes in the ReninAAV db/db uNx Model of Advanced Diabetic Kidney Disease Exhibit Features of Human Disease

The ReninAAV db/db uNx model of diabetic kidney disease (DKD) exhibits hallmarks of advanced human disease, including progressive elevations in albuminuria and serum creatinine, loss of glomerular filtration rate, and pathological changes. Microarray analysis of renal transcriptome changes were more similar to human DKD when compared to db/db eNOS−/− model. The model responds to treatment with arterial pressure lowering (lisinopril) or glycemic control (rosiglitazone) at early stages of disease. We hypothesized the ReninAAV db/db uNx model with advanced disease would have residual disease after treatment with lisinopril, rosiglitazone, or combination of both. To test this, ReninAAV db/db uNx mice with advanced disease were treated with lisinopril, rosiglitazone, or combination of both for 10 weeks. All treatment groups showed significant lowering of urinary albumin to creatinine ratio compared to baseline; however, only combination group exhibited lowering of serum creatinine. Treatment improved renal pathological scores compared to baseline values with residual disease evident in all treatment groups when compared to db/m controls. Gene expression analysis by TaqMan supported pathological changes with increased fibrotic and inflammatory markers. The results further validate this model of DKD in which residual disease is present when treated with agents to lower arterial pressure and glycemic control.

Synopsis of Sweet! Mouse Models of Diabetic Kidney Disease

Diabetes mellitus (types 1 and 2) is the leading cause of glomerular disease and end-stage renal disease in most developed countries, with estimates that one-third of people living with diabetes will develop diabetic kidney disease (DKD). The current standard of care medications slow but do not arrest progression of kidney disease, and therefore, therapy for DKD is a highly unmet medical need for patients. To discover and test novel and durable new therapies, it is necessary to develop animal models of human DKD, which authentically recapitulate the human disease state and provide translatable efficacy to human patients. Here, we review selected mouse models of human DKD, which demonstrate many of the features of type 2 human DKD.