Gene therapy targeting kidney diseases: routes and vehicles

Overexpression of Corin Ameliorates Kidney Fibrosis through Inhibition of Wnt/β-Catenin Signaling in Mice

The Wnt/β-catenin pathway represents a promising therapeutic target for mitigating kidney fibrosis. Corin possesses the homologous ligand binding site [Frizzled-cysteine-rich domain (Fz-CRD)] similar to Frizzled proteins, which act as receptors for Wnt. The Fz-CRD has been found in eight different proteins, all of which, except for corin, are known to bind Wnt and regulate its signal transmission. We hypothesized that corin may inhibit the Wnt/β-catenin signaling pathway and thereby reduce fibrogenesis. Reduced expression of corin along with the increased activity of Wnt/β-catenin signaling was found in unilateral ureteral obstruction (UUO) and ureteral ischemia/reperfusion injury (UIRI) models. In vitro, corin bound to the Wnt1 through its Fz-CRDs and inhibit the Wnt1 function responsible for activating β-catenin. Transforming growth factor-β1 inhibited corin expression, accompanied by activation of β-catenin; conversely, overexpression of corin attenuated the fibrotic effects of transforming growth factor-β1. In vivo, adenovirus-mediated overexpression of corin attenuated the progression of fibrosis, which was potentially associated with the inhibition of Wnt/β-catenin signaling and the down-regulation of its target genes after UUO and UIRI. These results suggest that corin acts as an antagonist that protects the kidney from pathogenic Wnt/β-catenin signaling and from fibrosis following UUO and UIRI.

The Smad3-dependent microRNA let-7i-5p promoted renal fibrosis in mice with unilateral ureteral obstruction

Renal fibrosis is a common feature of all types of chronic kidney disease (CKD) and is tightly regulated by the TGF-β/Smad3 pathway. Let-7i-5p belongs to the let-7 microRNA family with diverse biological functions. It has been reported that let-7i-5p suppresses fibrotic disease in the heart, lungs, and blood vessels, while the role of let-7i-5p in renal fibrosis remains limited. In this study, we aimed to investigate the role of let-7i-5p in renal fibrosis in a mouse model of unilateral ureteral obstruction (UUO) and TGF-β1–stimulated renal tubular cell line TCMK1. The RNA-targeting CRISPR/Cas13d system was used to knock down let-7i-5p. Renal injury and fibrosis were determined by histological analysis, RT-PCR, Western blot, and immunostaining. Our results have shown that in the kidneys after UUO, the expression of let-7i-5p was significantly increased along with notable tubular injury and interstitial fibrosis. Electroporation of let-7i–targeting Cas13d plasmid efficiently knocked down let-7i-5p in kidneys after UUO with reduced tubular injury, fibrotic area, and expression of fibrotic marker genes α-SMA, fibronectin, and Col1a1. In TGF-β1–stimulated TCMK1 cells, knockdown of let-7i-5p by Cas13d plasmid transfection also blunted the expression of fibrotic marker genes. Most importantly, the genomic locus of let-7i showed enriched binding of Smad3 as revealed by chromatin immunoprecipitation. In TCMK1 cells, the overexpression of Smad3 can directly induce the expression of let-7i-5p. However, the deletion of Smad3 abolished TGF-β1–stimulated let-7i-5p expression. Collectively, these findings suggest that let-7i-5p is a Smad3-dependent microRNA that plays a pathogenic role in renal fibrosis. Let-7i-5p could be a promising target for the treatment of CKD-associated renal fibrosis.

Effects of Tissue Pressure on Transgene Expression Characteristics via Renal Local Administration Routes from Ureter or Renal Artery in the Rat Kidney

We previously developed a renal pressure-mediated transfection method (renal pressure method) as a kidney-specific in vivo gene delivery system. However, additional information on selecting other injection routes and applicable animals remains unclear. In this study, we selected renal arterial and ureteral injections as local administration routes and evaluated the characteristics of gene delivery such as efficacy, safety, and distribution in pressured kidney of rat. Immediately after the naked pDNA injection, via renal artery or ureter, the left kidney of the rat was pressured using a pressure controlling device. Transfection efficiency of the pressured kidney was about 100-fold higher than that of the injection only group in both administration routes. The optimal pressure intensity in the rat kidney was 1.2 N/cm² for renal arterial injection and 0.9 N/cm² for ureteral injection. We found that transgene expression site differs according to administration route: cortical fibroblasts and renal tubule in renal arterial injection and cortical and medullary tubule and medullary collecting duct in ureteral injection. This is the first report to demonstrate that the renal pressure method can also be effective, after renal arterial and ureteral injections, in rat kidney.

Inhibition of Glomerular Mesangial Cell Proliferation by siPDGF-B- and siPDGFR-β-Containing Chitosan Nanoplexes

Mesangioproliferative glomerulonephritis is a disease that has a high incidence in humans. In this disease, the proliferation of glomerular mesangial cells and the production of extracellular matrix are important. In recent years, the RNAi technology has been widely used in the treatment of various diseases due to its capability to inhibit the gene expression with high specificity and targeting. The objective of this study was to decrease mesangial cell proliferation by knocking down PDGF-B and its receptor, PDGFR-β. To be able to use small interfering RNAs (siRNAs) in the treatment of this disease successfully, it is necessary to develop appropriate delivery systems. Chitosan, which is a biopolymer, is used as a siRNA delivery system in kidney drug targeting. In order to deliver siRNA molecules targeted at PDGF-B and PDGFR-β, chitosan/siRNA nanoplexes were prepared. The in vitro characterization, transfection studies, and knockdown efficiencies were studied in immortalized and primary rat mesangial cells. In addition, the effects of chitosan nanoplexes on mesangial cell proliferation and migration were investigated. After in vitro transfection, the PDGF-B and PDGFR-β gene silencing efficiencies of PDGF-B and PDGFR-β targeting siRNA-containing chitosan nanoplexes were 74 and 71% in immortalized rat mesangial cells and 66 and 62% in primary rat mesangial cells, respectively. siPDGF-B- and siPDGFR-β-containing nanoplexes indicated a significant decrease in mesangial cell migration and proliferation. These results suggested that mesangial cell proliferation may be inhibited by silencing of the PDGF-B signaling pathway. Gene silencing approaches with chitosan-based gene delivery systems have promise for the efficient treatment of renal disease.

Targeting gene expression to specific cells of kidney tubules in vivo, using adenoviral promoter fragments

Although techniques for cell-specific gene expression via viral transfer have advanced, many challenges (e.g., viral vector design, transduction of genes into specific target cells) still remain. We investigated a novel, simple methodology for using adenovirus transfer to target specific cells of the kidney tubules for the expression of exogenous proteins. We selected genes encoding sodium-dependent phosphate transporter type 2a (NPT2a) in the proximal tubule, sodium-potassium-2-chloride cotransporter (NKCC2) in the thick ascending limb of Henle (TALH), and aquaporin 2 (AQP2) in the collecting duct. The promoters of the three genes were linked to a GFP-coding fragment, the final constructs were then incorporated into an adenovirus vector, and this was then used to generate gene-manipulated viruses. After flushing circulating blood, viruses were directly injected into the renal arteries of rats and were allowed to site-specifically expression in tubule cells, and rats were then euthanized to obtain kidney tissues for immunohistochemistry. Double staining with adenovirus-derived EGFP and endogenous proteins were examined to verify orthotopic expression, i.e. "adenovirus driven NPT2a-EGFP and endogenous NHE3 protein", "adenovirus driven NKCC2-EGFP and endogenous NKCC2 protein" and "adenovirus driven AQP2-EGFP and endogenous AQP2 protein". Owing to a lack of finding good working anti-NPT2a antibody, an antibody against a different protein (sodium-hydrogen exchanger 3 or NHE3) that is also specifically expressed in the proximal tubule was used. Kidney structures were well-preserved, and other organ tissues did not show EGFP staining. Our gene transfer method is easier than using genetically engineered animals, and it confers the advantage of allowing the manipulation of gene transfer after birth. This is the first method to successfully target gene expression to specific cells in the kidney tubules. This study may serve as the first step for safe and effective gene therapy in the kidney tubule diseases.

Glomeruli or interstitium targeted by inter-renal injections supplemented by electroporation: Still a useful tool in renal research

BACKGROUND

Studies concerning proteins are always a crucial part of renal research. As a result of current technologies, scientists have mastered several techniques for generating genetically modified animals. However, in most cases, accessing these animals is still time-consuming and often expensive. This makes the alteration of protein expression by in vivo plasmid transfection an easily-accessible alternative. However, there is still no comprehensive study describing where plasmids would be expressed when they are injected into the kidneys.

METHODS

We injected pEGFP-N1 into rats via intra-/inter-renal channels and detected green fluorescent protein (GFP) by immunohistochemistry and immunofluorescence to localize plasmid expression.

RESULTS

Seven days post-injection, we found that GFP was expressed in the glomeruli when pEGFP-N1 was injected via the renal artery or vein enhanced by electroporation and in the interstitium following injection via the ureter. Other channels, including intraperitoneal, subcapsule and parenchymal injection, only led to scattered expression within the kidneys.

CONCLUSIONS

The present study provides evidence that plasmid transfection via the renal vessels is suitable for glomeruli research and that transfection via the ureter is appropriate for studies regarding interstitium lesions. Additionally, we provide evidence that plasmid transfection on live animals is still an applicable and useful tool, as well as being cost-effective and facile.

siRNA technology in kidney transplantation: current status and future potential

Kidney transplantation is one of the most common transplantation operations in the world, accounting for up to 50 % of all transplantation surgeries. To curtail the damage to transplanted organs that is caused by ischemia-reperfusion injury and the recipient's immune system, small interfering RNA (siRNA) technology is being explored. Importantly, the kidney as a whole is a preferential site for non-specific systemic delivery of siRNA. To date, most attempts at siRNA-based therapy for transplantation-related conditions have remained at the in vitro stage, with only a few of them being advanced into animal models. Hydrodynamic intravenous injection of naked or carrier-bound siRNAs is currently the most common route for delivery of therapeutic constructs. To our knowledge, no systematic screens for siRNA targets most relevant for kidney transplantation have been attempted so far. A majority of researchers have arrived at one or another target of interest by analyzing current literature that dissects pathological processes taking place in transplanted organs. A majority of the genes that make up the list of 53 siRNA targets that have been tested in transplantation-related models so far belong to either apoptosis- or immune rejection-centered networks. There is an opportunity for therapeutic siRNA combinations that may be delivered within the same delivery vector or injected at the same time and, by targeting more than one pathway, or by hitting the same pathways within two different key points, will augment the effects of each other.

Kidney-specific expression of GFP by in-utero delivery of pseudotyped adeno-associated virus 9

Gene therapy targeting of kidneys has been largely unsuccessful. Recently, a recombinant adeno-associated virus (rAAV) vector was used to target adult mouse kidneys. Our hypothesis is that a pseudotyped rAAV 2/9 vector can produce fetal kidney-specific expression of the green fluorescent protein (GFP) gene following maternal tail vein injection of pregnant mice. Pregnant mice were treated with rAAV2/9 vectors with either the ubiquitous cytomegalovirus promoter or the minimal NPHS1 promoter to drive kidney-specific expression of GFP. Kidneys from dams and pups were analyzed for vector DNA, gene expression, and protein. Vector DNA was identified in kidney tissue out to 12 weeks at low but stable levels, with levels higher in dams than that in pups. Robust GFP expression was identified in the kidneys of both dams and pups treated with the cytomegalovirus (CMV)-enhanced green fluorescent protein (eGFP) vector. When treated with the NPHS1-eGFP vector, dams and pups showed expression of GFP only in kidneys, localized to the glomeruli. An 80-fold increase in GFP mRNA expression in dams and a nearly 12-fold increase in pups was found out to 12 weeks of life. Selective targeting of the fetal kidney with a gene therapy vector was achieved by utilizing the pseudotyped rAAV 2/9 vector containing the NPHS1 promoter.

Contrast ultrasound and targeted microbubbles: diagnostic and therapeutic applications in progressive diabetic nephropathy

Diabetic nephropathy remains one of the most common causes for end-stage renal disease worldwide. Although therapies aimed at optimizing glycemic control and systemic blood pressure have benefit, the reduction in progressive nephropathy remains modest at best. Thus, research continues to focus on newer therapies to address the unmet needs for additional renal protective strategies. The ability to noninvasively image the molecular and cellular processes that underlie diabetic nephropathy would be useful in risk stratifying patients with diabetes, and more importantly would aid in the evaluation of novel therapies to prevent and treat nephropathy. In addition, the development of ultrasound technologies that allow targeted gene delivery using high-power ultrasound and DNA-bearing microbubbles may have applicability for gene therapy to prevent diabetic nephropathy. This review highlights contrast-enhanced ultrasound imaging techniques for the evaluation of renal pathologies, including perfusion and molecular imaging techniques, and ultrasound-mediated gene delivery for therapeutic applications in diabetic nephropathy, that have potential for translation to clinical practice.

Studies on neutral, cationic and biotinylated cationic microbubbles in enhancing ultrasound-mediated gene delivery in vitro and in vivo

Ultrasound-mediated gene transfer is emerging as a practical means of facilitating targeted gene expression and is significantly enhanced in the presence of exogenously added microbubbles. This study explores the influence of microbubble surface modifications on their interaction with plasmid DNA and target cells, and the functional consequences of those interactions in terms of ultrasound-mediated gene transfer. Polyethylene glycol-stabilized, lipid-shelled microbubbles with neutral (SDM201), cationic (SDM202) and biotinylated cationic (SDM302) surfaces were compared in terms of their abilities to interact with a luciferase-encoding reporter plasmid DNA and with target cells in vitro. The results demonstrate that the biotinylated cationic microbubble>cationic microbubble>neutral microbubble, in terms of their abilities to interact with target cells and to enhance ultrasound-mediated gene transfer, particularly at low microbubble concentration. The presence of a net positive charge on both cationic microbubbles promoted the formation of microbubble-nucleic acid complexes, although preformation of the complexes prior to addition to target cells inhibited the interaction between the microbubbles and target cells in vitro. The impact of these findings on potential in vitro or ex vivo therapeutic applications of microbubble-enhanced ultrasound-mediated gene transfer is discussed. All three microbubble preparations could be used to facilitate gene transfer in vivo and the potential advantages associated with the use of the cationic microbubbles for targeted gene delivery are discussed.

Mesangial pathology in glomerular disease: targets for therapeutic intervention

The glomerulus is the filtration unit of the kidney. Disruption of glomerular function may be caused by primary glomerular pathology or secondary to systemic diseases. The mesangial, endothelial and epithelial cells of the glomerulus are involved in most pathologic processes. Animal models provide an understanding of the molecular basis of glomerular disease. These studies show that mesangial cells are critical players in the initiation and progression of disease. Therefore, modulation of mesangial cell responses offers a novel therapeutic approach. The complex architecture of the kidney, specifically the renal glomerulus, makes targeted drug delivery especially challenging. Targeted delivery of therapeutic agents reduces dose of administration and minimises unwanted side effects caused by toxicity to other tissues. The currently available modalities demonstrating the feasibility of mesangial cell targeting are discussed.

Novel siRNA delivery system to target podocytes in vivo

Podocytes are injured in several glomerular diseases. To alter gene expression specifically in podocytes in vivo, we took advantage of their active endocytotic machinery and developed a method for the targeted delivery of small interfering ribonucleic acids (siRNA). We generated an anti-mouse podocyte antibody that binds to rat and mouse podocytes in vivo. The polyclonal IgG antibody was cleaved into monovalent fragments, while preserving the antigen recognition sites. One Neutravidin molecule was linked to each monovalent IgG via the available sulfohydryl group. Protamine, a polycationic nuclear protein and universal adaptor for anionic siRNA, was linked to the neutravidin via biotin. The delivery system was named shamporter (sheep anti mouse podocyte transporter). Injection of shamporter coupled with either nephrin siRNA or TRPC6 siRNA via tail vein into normal rats substantially reduced the protein levels of nephrin or TRPC6 respectively, measured by western blot analysis and immunostaining. The effect was target specific because other podocyte-specific genes remained unchanged. Shamporter + nephrin siRNA induced transient proteinuria in rats. Control rats injected with shamporter coupled to control-siRNA showed no changes. These results show for the first time that siRNA can be delivered efficiently and specifically to podocytes in vivo using an antibody-delivery system.

Serotype chimeric and fiber-mutated adenovirus Ad5/19p-HIT for targeting renal cancer and untargeting the liver

Despite some advances, patients with advanced renal cell carcinoma (RCC) cannot usually be cured. Alteration of the natural tropism of adenoviruses may permit more specific gene transfer to target tissues. The aim of this study was to use novel targeting moieties for adenoviral gene therapy of RCC. Previous work in rats suggested that use of Ad5/19p (Ad5 capsid with Ad19p fiber) with kidney vascular targeting moieties HTTHREP (HTT), HITSLLS (HIT), and APASLYN (APA) placed into the fiber knob might be useful for targeting kidney vasculature. Therefore, we sought to investigate the utility of Ad5/19p variants for gene delivery to human RCC cell lines, clinical samples, and orthotopic murine models of metastatic RCC. Six different human RCC cell lines were infected but only Ad5/19p-HIT showed increased transduction, and only in one cell line. Thus, we analyzed human normal and cancerous kidney specimens fresh from patients, which might better mimic the three-dimensional architecture of clinical tumors and found that Ad5/19p-HIT showed transduction levels similar to Ad5. In mice, we found that intraperitoneal and intravenous Ad5/19p-HIT transduced tumors at levels comparable to Ad5, and that intratumoral Ad5/19p-HIT was superior to Ad5. Liver tropism was significantly reduced in comparison with Ad5. Improvements in tumor-to-liver transduction ratios suggested that Ad5/19p-HIT may be promising for systemic gene delivery to kidney tumors.

Anti-alpha8 integrin immunoliposomes in glomeruli of lupus-susceptible mice: a novel system for delivery of therapeutic agents to the renal glomerulus in systemic lupus erythematosus

OBJECTIVE

Glomerular mesangial cells are active participants in the pathogenesis of lupus glomerulonephritis (GN). Thus, targeted delivery of therapeutic agents to mesangial cells would be an attractive approach to treatment. However, lack of known unique mesangial cell surface markers has hampered this process. This study was undertaken in a mouse model of lupus GN to identify mesangial markers and to develop a system for targeted drug delivery to the glomerulus.

METHODS

Based on previous observations, alpha8 integrin expressed on the surface of glomerular mesangial cells was selected as a target molecule for delivery. Two mouse strains susceptible to lupus GN, NZM2328 and (NZM2328 x NOD)F1, were studied. Glomerular expression of alpha8 integrin in normal and nephritic mice was confirmed by immunofluorescence and quantitative polymerase chain reaction analysis. Liposomes were formulated and conjugated with an anti-alpha8 integrin antibody. These immunoliposomes were loaded with DiI, a red fluorescent dye, to allow tracking in vivo, and injected into the tail vein of female mice at different ages. Specificity of targeting was studied by fluorescence microscopy and flow cytometry.

RESULTS

Expression of alpha8 integrin was observed in the glomeruli of normal and nephritic mice. Anti-alpha8 integrin immunoliposomes were detected in the glomerulus and glomerular mesangial cells after tail vein injection in normal and nephritic mice. Delivery of DiI by anti-alpha8 integrin immunoliposomes was tissue specific, being observed predominantly in the glomeruli, with some nonspecific uptake by CD11b cells.

CONCLUSION

These findings are the first demonstration of specific delivery of anti-alpha8 integrin immunoliposomes to the mesangium following tail vein injection in mice. Anti-alpha8 integrin immunoliposomes thus offer a novel approach for targeted drug therapy in lupus and other glomerular diseases.

Kidney-specific reconstitution of the A1 adenosine receptor in A1 adenosine receptor knockout mice reduces renal ischemia-reperfusion injury

Genetic deletion of the adenosine A1 receptor (A1AR) increased renal injury following ischemia-reperfusion injury suggesting that receptor activation is protective in vivo. Here we tested this hypothesis by expressing the human-A(1)AR in A(1)AR knockout mice. Renal ischemia-reperfusion was induced in knockout mice 2 days after intrarenal injection of saline or a lentivirus encoding enhanced green fluorescent protein (EGFP) or EGFP-human-A(1)AR. We found that the latter procedure induced a robust expression of the reporter protein in the kidneys of knockout mice. Mice with kidney-specific human-A(1)AR reconstitution had significantly lower plasma creatinine, tubular necrosis, apoptosis, and tubular inflammation as evidenced by decreased leukocyte infiltration, pro-inflammatory cytokine, and intercellular adhesion molecule-1 expression in the kidney following injury compared to mice injected with saline or the control lentivirus. Additionally, there were marked disruptions of the proximal tubule epithelial filamentous (F)-actin cytoskeleton in both sets of control mice upon renal injury, whereas the reconstituted mice had better preservation of the renal tubule actin cytoskeleton, which co-localized with the human-A(1)ARs. Consistent with reduced renal injury, there was a significant increase in heat shock protein-27 expression, also co-localizing with the preserved F-actin cytoskeleton. Our findings suggest that selective expression of cytoprotective A(1)ARs in the kidney can attenuate renal injury.