Lentiviral gene transduction of kidney

Nfil3 contributes to renal fibrosis by activating fibroblasts through directly promoting the expression of Spp1

The activation of fibroblasts into myofibroblasts and the expansion of myofibroblasts are key processes contributing to renal fibrosis; however, the precise underlying mechanisms remain largely unclear. In this study, we found that nuclear factor, interleukin 3 regulated (Nfil3), a basic leucine zipper transcription factor, was significantly upregulated in fibroblasts in kidney tissues from mouse models of unilateral ureteral obstruction (UUO)-induced renal fibrosis and kidney biopsies from patients with renal fibrosis. Conditional knockout of Nfil3 in fibroblasts (Nfil3flox/floxS100a4Cre) and global knockout of Nfil3 reduced UUO-induced accumulation of myofibroblasts and the severity of renal fibrosis in mice, whereas ectopic expression of Nfil3 in fibroblasts activated renal interstitial fibroblasts and initiated renal fibrosis. Overexpression of Nfil3 significantly induced the expression of secreted phosphoprotein 1 (Spp1). Mechanistically, Nfil3 mediated the upregulation of Spp1 in renal fibroblasts by interacting with a conserved sequence in the promoter of Spp1 to regulate its transcription. Furthermore, transforming growth factor beta 1 (Tgfb1) was found to induce the upregulation of Nfil3 in renal fibroblasts. Knockdown of Nfil3 attenuated Tgfb1-induced expression of extracellular matrix proteins and the proliferation of fibroblasts by downregulating Spp1. Altogether, these results suggest that Nfil3 plays an important role in the activation and expansion of fibroblasts, thereby contributing to renal fibrosis.

Gene therapy and kidney diseases

Chronic kidney disease (CKD) poses a significant global health challenge, projected to become one of the leading causes of death by 2040. Current treatments primarily manage complications and slow progression, highlighting the urgent need for personalized therapies targeting the disease-causing genes. Our increased understanding of the underlying genomic changes that lead to kidney diseases coupled with recent successful gene therapies targeting specific kidney cells have turned gene therapy and genome editing into a promising therapeutic approach for treating kidney disease. This review paper reflects on different delivery routes and systems that can be exploited to target specific kidney cells and the ways that gene therapy can be used to improve kidney health.

Gene therapy of Dent disease type 1 in newborn ClC-5 null mice for sustained transgene expression and gene therapy effects

Dent disease type 1 is caused by changes in the chloride voltage-gated channel 5 (CLCN5) gene on chromosome X, resulting in the lack or dysfunction of chloride channel ClC-5. Individuals affected by Dent disease type 1 show proteinuria and hypercalciuria. Previously we found that lentiviral vector-mediated hCLCN5 cDNA supplementary therapy in ClC-5 null mice was effective only for three months following gene delivery, and the therapeutic effects disappeared four months after treatment, most likely due to immune responses to the ClC-5 proteins expressed in the treated cells. Here we tried two strategies to reduce possible immune responses: 1) confining the expression of ClC-5 expression to the tubular cells with tubule-specific Npt2a and Sglt2 promoters, and 2) performing gene therapy in newborn mutant mice whose immune system has not fully developed. We found that although Npt2a and Sglt2 promoters successfully drove ClC-5 expression in the kidneys of the mutant mice, the treatment did not ameliorate the phenotypes. However, gene delivery to the kidneys of newborn Clcn5 mutant mice enabled long-term transgene expression and phenotype improvement. Our data suggest that performing gene therapy on Dent disease affected subjects soon after birth could be a promising strategy to attenuate immune responses in Dent disease type 1 gene therapy.

Current Status and Prospects of Viral Vector-Based Gene Therapy to Treat Kidney Diseases

Inherited kidney diseases are among the leading causes of chronic kidney disease, reducing the quality of life and resulting in substantial socioeconomic impact. The advent of early genetic testing and the growing understanding of the molecular basis and pathophysiology of these disorders have opened avenues for novel treatment strategies. Viral vector-based gene therapies have evolved from experimental treatments for rare diseases to potent platforms that carry the intrinsic potential to provide a cure with a single application. Several gene therapy products have reached the market, and the numbers are only expected to increase. Still, none target inherited kidney diseases. Gene transfer to the kidney has lagged when compared to other tissue-directed therapies such as hepatic, neuromuscular, and ocular tissues. Systemic delivery of genetic information to tackle kidney disease is challenging. The pharma industry is taking steps to take on kidney disease and to translate the current research into the therapeutic arena. In this review, we provide an overview of the current viral vector-based approaches and their potential. We discuss advances in platforms and injection routes that have been explored to enhance gene delivery toward kidney cells in animal models, and how these can fuel the development of viable gene therapy products for humans.

Sweroside attenuates podocyte injury and proteinuria in part by activating Akt/BAD signaling in mice

In this study, we investigated the effects of sweroside on podocyte injury in diabetic nephropathy (DN) mice and elucidated its molecular mechanisms. We conducted in vivo experiments using a C57BL/6 mice model of DN to explore the effects of sweroside on proteinuria and podocyte injury in DN mice. In in vitro experiments, conditionally immortalized mouse podocytes were treated with high glucose and sweroside, and the protective effects of sweroside on podocyte injury were analyzed. In vitro, Akt/BAD pathways were detected using gene siRNA silencing assays and found to be involved in the protective roles of sweroside in high glucose-mediated podocyte injury. In vivo, sweroside significantly decreased albuminuria in DN mice (p < 0.01). periodic acid-Schiff staining showed that sweroside alleviated the glomerular volume and mesangium expansion in DN mice. Consistently, western blot and reverse transcription-polymerase chain reaction analyses showed that the profibrotic molecule expression in the glomeruli declined in sweroside-treated DN mice. Immunofluorescent results showed that sweroside preserved nephrin and podocin expression, and transmission electron microscopy showed that sweroside attenuated podocyte injury. In DN mice, sweroside decreased podocyte apoptosis, and increased nephrin, podocin expression and decreased desmin and HIF1α expression. These results confirmed that sweroside ameliorated albuminuria, glomerulomegaly, and glomerulosclerosis in these mice. Experiments in vitro revealed that sweroside improved HG-induced podocyte injury and apoptosis. Sweroside stimulated activation of the Akt/BAD pathway and upregulated Bcl-2-associated death promoter (BAD) and p-Akt. Overall, sweroside protected podocytes from injury and prevented the progression of DN, providing a novel strategy for the treatment of DN.

Metformin triggers a kidney GDF15-dependent area postrema axis to regulate food intake and body weight

Metformin, the most widely prescribed medication for obesity-associated type 2 diabetes (T2D), lowers plasma glucose levels, food intake, and body weight in rodents and humans, but the mechanistic site(s) of action remain elusive. Metformin increases plasma growth/differentiation factor 15 (GDF15) levels to regulate energy balance, while GDF15 administration activates GDNF family receptor α-like (GFRAL) that is highly expressed in the area postrema (AP) and the nucleus of the solitary tract (NTS) of the hindbrain to lower food intake and body weight. However, the tissue-specific contribution of plasma GDF15 levels after metformin treatment is still under debate. Here, we found that metformin increased plasma GDF15 levels in high-fat (HF) fed male rats through the upregulation of GDF15 synthesis in the kidney. Importantly, the kidney-specific knockdown of GDF15 expression as well as the AP-specific knockdown of GFRAL expression negated the ability of metformin to lower food intake and body weight gain. Taken together, we unveil the kidney as a target of metformin to regulate energy homeostasis through a kidney GDF15-dependent AP axis.

Macrophage‑derived exosomal miRNA‑155 promotes tubular injury in ischemia‑induced acute kidney injury

Tubule injury is a characteristic pathological feature of acute kidney injury (AKI) and determines the prognosis of kidney disease. However, the exact mechanism of tubule injury remains largely unclear. In the present study, the exact mechanism of tubule injury was investigated. Bilateral renal ischemia/reperfusion (I/R) injury (I/RI) was induced in mice and exosome secretion inhibitor GW4869 and miRNA-155 inhibitor were used. In addition, the exosomal microRNA (miR)-155-mediated cross-talk between macrophage and tubular cells was also investigated. It was determined that tubular injury was observed in an I/R-induced AKI model, which was closely associated with macrophage infiltration. Interestingly, blocking exosome production using GW4869 ameliorated tubular injury in I/R-induced AKI. Mechanistically, once released, activated macrophage-derived exosomal miR-155 was internalized by tubular cells, resulting in increased tubule injury through targeting of suppressor of cytokine signaling-1 (SOCS-1), a negative regulator of NF-κB signaling. In addition, a dual-luciferase reporter assay confirmed that SOCS-1 was the direct target of miR-155 in tubular cells. Notably, injection of these miR-155-enriched exosomes into renal parenchyma resulted in increased tubule injury in vivo. Thus, the present study demonstrated that exosomal miR-155 mediated the communication between activated macrophages and injured tubules, leading to progression of AKI, which not only provide novel insights into the pathophysiology of AKI but also offer a new therapeutic strategy for kidney diseases.

MBTPS2 exacerbates albuminuria in streptozotocin-induced type I diabetic nephropathy by promoting endoplasmic reticulum stress-mediated renal damage

BACKGROUND

The membrane-bound transcription factor protease site 2 (MBTPS2) is an intramembranous metalloprotease involved in the regulation of ER stress response, however, whether it is associated with DN is unknown.

RESULTS

We report that MBTPS2 expression is upregulated in the renal cortex of diabetic mice induced by streptozotocin (STZ), a murine model of insulinopenic type 1 DN. Functionally, in vivo, MBTPS2 overexpression exacerbates and its knockdown attenuates albuminuria, which indicate a detrimental role of MBTPS2 played in albuminuria development in DN mice. We further show that MBTPS2 promotes ER stress and renal damage in DN mice, and that reducing ER stress via a chemical chaperone 4-phenylbutyric acid (4-PBA) markedly rescues MBTPS2-exacerbated renal damage and albuminuria severity.

CONCLUSIONS

Collectively, our study associates the function of MBTPS2 in DN albuminuria with ER stress regulation, thus underscoring the notorious role of maladaptive ER response in influencing DN albuminuria.

MYDGF attenuates podocyte injury and proteinuria by activating Akt/BAD signal pathway in mice with diabetic kidney disease

AIMS/HYPOTHESIS

Myeloid-derived growth factor (MYDGF), mainly secreted by bone marrow-derived cells, has been known to promote glucagon-like peptide-1 production and improve glucose/lipid metabolism in mouse models of diabetes, but little is known about the functions of MYDGF in diabetic kidney disease (DKD). Here, we investigated whether MYDGF can prevent the progression of DKD.

METHODS

In vivo experiments, both loss- and gain-of-function strategies were used to evaluate the effect of MYDGF on albuminuria and pathological glomerular lesions. We used streptozotocin-treated Mydgf knockout and wild-type mice on high fat diets to induce a model of DKD. Then, albuminuria, glomerular lesions and podocyte injury were evaluated in Mydgf knockout and wild-type DKD mice treated with adeno-associated virus-mediated Mydgf gene transfer. In vitro and ex vivo experiments, the expression of slit diaphragm protein nephrin and podocyte apoptosis were evaluated in conditionally immortalised mouse podocytes and isolated glomeruli from non-diabetic wild-type mice treated with recombinant MYDGF.

RESULTS

MYDGF deficiency caused more severe podocyte injury in DKD mice, including the disruption of slit diaphragm proteins (nephrin and podocin) and an increase in desmin expression and podocyte apoptosis, and subsequently caused more severe glomerular injury and increased albuminuria by 39.6% compared with those of wild-type DKD mice (p < 0.01). Inversely, MYDGF replenishment attenuated podocyte and glomerular injury in both wild-type and Mydgf knockout DKD mice and then decreased albuminuria by 36.7% in wild-type DKD mice (p < 0.01) and 34.9% in Mydgf knockout DKD mice (p < 0.01). Moreover, recombinant MYDGF preserved nephrin expression and inhibited podocyte apoptosis in vitro and ex vivo. Mechanistically, the renoprotection of MYDGF was attributed to the activation of the Akt/Bcl-2-associated death promoter (BAD) pathway.

CONCLUSIONS/INTERPRETATION

The study demonstrates that MYDGF protects podocytes from injury and prevents the progression of DKD, providing a novel strategy for the treatment of DKD. Graphical abstract.

Improving Molecular Therapy in the Kidney

Mutations in approximately 80 genes have been implicated as the cause of various genetic kidney diseases. However, gene delivery to kidney cells from the blood is inefficient because of the natural filtering functions of the glomerulus, and research into and development of gene therapy directed toward kidney disease has lagged behind as compared with hepatic, neuromuscular, and ocular gene therapy. This lack of progress is in spite of numerous genetic mouse models of human disease available to the research community and many vectors in existence that can theoretically deliver genes to kidney cells with high efficiency. In the past decade, several groups have begun to develop novel injection techniques in mice, such as retrograde ureter, renal vein, and direct subcapsular injections to help resolve the issue of gene delivery to the kidney through the blood. In addition, the ability to retarget vectors specifically toward kidney cells has been underutilized but shows promise. This review discusses how recent advances in gene delivery to the kidney and the field of gene therapy can leverage the wealth of knowledge of kidney genetics to work toward developing gene therapy products for patients with kidney disease.

Gene therapy research for kidney diseases

A resurgence in the development of newer gene therapy systems has led to recent successes in the treatment of B cell cancers, retinal degeneration and neuromuscular atrophy. Gene therapy offers the ability to treat the patient at the root cause of their malady by restoring normal gene function and arresting the pathological progression of their genetic disease. The current standard of care for most genetic diseases is based upon the symptomatic treatment with polypharmacy while minimizing any potential adverse effects attributed to the off-target and drug-drug interactions on the target or other organs. In the kidney, however, the development of gene therapy modifications to specific renal cells has lagged far behind those in other organ systems. Some positive strides in the past few years provide continued enthusiasm to invest the time and effort in the development of new gene therapy vectors for medical intervention to treat kidney diseases. This mini-review will systematically describe the pros and cons of the most commonly tested gene therapy vector systems derived from adenovirus, retrovirus, and adeno-associated virus and provide insight about their potential utility as a therapy for various types of genetic diseases in the kidney.

Transparenchymal Renal Pelvis Injection of Recombinant Adeno-Associated Virus Serotype 9 Vectors Is a Practical Approach for Gene Delivery in the Kidney

Gene therapy has great potential in treating human diseases, but little progress has been made in preclinical and clinical studies of renal diseases. To find an effective gene delivery approach in the kidney, transparenchymal renal pelvis injection was developed. Using adeno-associated virus serotype 9 (AAV9) vectors, the gene delivery efficiency and safety of this administration method were evaluated. The results showed that the exogenous gene was expressed in the tubular epithelial cells of the injected kidney, with a much lower expression level in the contralateral kidney. Extra-renal transduction in the liver was also observed in this study, with the liver function of AAV9-injected mice comparable to that of control mice. Altogether, the administration of AAV9 vectors by newly established transparenchymal renal pelvis injection achieved the desired exogenous gene expression in renal tubular cells, and hence might be one possible way for gene therapy in renal diseases.

High-fidelity CRISPR/Cas9- based gene-specific hydroxymethylation rescues gene expression and attenuates renal fibrosis

While suppression of specific genes through aberrant promoter methylation contributes to different diseases including organ fibrosis, gene-specific reactivation technology is not yet available for therapy. TET enzymes catalyze hydroxymethylation of methylated DNA, reactivating gene expression. We here report generation of a high-fidelity CRISPR/Cas9-based gene-specific dioxygenase by fusing an endonuclease deactivated high-fidelity Cas9 (dHFCas9) to TET3 catalytic domain (TET3CD), targeted to specific genes by guiding RNAs (sgRNA). We demonstrate use of this technology in four different anti-fibrotic genes in different cell types in vitro, among them RASAL1 and Klotho, both hypermethylated in kidney fibrosis. Furthermore, in vivo lentiviral delivery of the Rasal1-targeted fusion protein to interstitial cells and of the Klotho-targeted fusion protein to tubular epithelial cells each results in specific gene reactivation and attenuation of fibrosis, providing gene-specific demethylating technology in a disease model.

Suppression of gene expression due to aberrant promoter methylation contributes to organ fibrosis. Here, the authors couple a deactivated Cas9 to the TET3 catalytic domain to induce expression of four antifibrotic genes, and show that lentiviral-mediated delivery is effective in reducing kidney fibrosis in mouse models.

Intrarenal ghrelin receptor inhibition ameliorates angiotensin II-dependent hypertension in rats

The intrarenal ghrelin receptor (GR) is localized to collecting duct (CD) cells, where it increases epithelial Na⁺ channel (αE_NaC)-dependent sodium reabsorption in rodents. We hypothesized that chronic GR inhibition with intrarenal GR siRNA lowers blood pressure (BP) in angiotensin II-dependent hypertension via reductions in αE_NaC-dependent sodium reabsorption. Uninephrectomized Sprague-Dawley rats ( n = 121) received subcutaneous osmotic pumps for chronic systemic delivery of angiotensin II or vehicle (5% dextrose in water). Rats also received intrarenal infusion of vehicle, GR siRNA, or scrambled (SCR) siRNA. In rats receiving intrarenal vehicle or intrarenal SCR siRNA, systemic angiotensin II infusion increased sodium retention and BP on day 1, and BP remained elevated throughout the 5-day study. These rats also demonstrated increased CD GR expression after 5 days of infusion. However, intrarenal GR siRNA infusion prevented angiotensin II-mediated sodium retention on day 1, induced a continuously negative cumulative sodium balance compared with angiotensin II alone, and reduced BP chronically. Glomerular filtration rate and renal blood flow remained unchanged in GR siRNA-infused rats. Systemic angiotensin II infusion also increased serum aldosterone levels, CD αE_NaC, and phosphorylated serum and glucocorticoid-inducible kinase 1 expression in rats with intrarenal SCR siRNA; however, these effects were not observed in the presence of intrarenal GR siRNA, despite exposure to the same systemic angiotensin II. These data demonstrate that chronic inhibition of intrarenal GR activity significantly reduces αE_NaC-dependent sodium retention, resulting in a negative cumulative sodium balance, thereby ameliorating angiotensin II-induced hypertension in rats. Renal GRs represent a novel therapeutic target for the treatment of hypertension and other sodium-retaining states.

BCL6 attenuates renal inflammation via negative regulation of NLRP3 transcription

Renal inflammation contributes to the pathogeneses of hypertension. This study was designed to determine whether B-cell lymphoma 6 (BCL6) attenuates renal NLRP3 inflammasome activation and inflammation and its underlying mechanism. Male spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were used in the present study. Angiotensin (Ang) II or lipopolysaccharides (LPS) was used to induce inflammation in HK-2 cells, a human renal tubular epithelial (RTE) cell line. NLRP3 inflammasome was activated and BCL6 was downregulated in the kidneys of SHR. Either Ang II or LPS suppressed BCL6 expression in HK-2 cells. BCL6 overexpression in HK-2 cells attenuated Ang II-induced NLRP3 upregulation, inflammation and cell injury. The inhibitory effects of BCL6 overexpression on NLRP3 expression and inflammation were also observed in LPS-treated HK-2 cells. BCL6 inhibited the NLRP3 transcription via binding to the NLRP3 promoter. BCL6 knockdown with shRNA increased NLRP3 and mature IL-1β expression levels in both PBS- or Ang II-treated HK-2 cells but had no significant effects on ASC, pro-caspase-1 and pro-IL-1β expression levels. BCL6 overexpression caused by recombinant lentivirus expressing BCL6 reduced blood pressure in SHR. BCL6 overexpression prevented the upregulation of NLRP3 and mature IL-1β expression levels in the renal cortex of SHR. The results indicate that BCL6 attenuates Ang II- or LPS-induced inflammation in HK-2 cells via negative regulation of NLRP3 transcription. BCL6 overexpression in SHR reduced blood pressure, NLRP3 expression and inflammation in the renal cortex of SHR.

Histone deacetylase 4 selectively contributes to podocyte injury in diabetic nephropathy

Studies have highlighted the importance of histone deacetylase (HDAC)-mediated epigenetic processes in the development of diabetic complications. Inhibitors of HDAC are a novel class of therapeutic agents in diabetic nephropathy, but currently available inhibitors are mostly nonselective inhibit multiple HDACs, and different HDACs serve very distinct functions. Therefore, it is essential to determine the role of individual HDACs in diabetic nephropathy and develop HDAC inhibitors with improved specificity. First, we identified the expression patterns of HDACs and found that, among zinc-dependent HDACs, HDAC2/4/5 were upregulated in the kidney from streptozotocin-induced diabetic rats, diabetic db/db mice, and in kidney biopsies from diabetic patients. Podocytes treated with high glucose, advanced glycation end products, or transforming growth factor-β (common detrimental factors in diabetic nephropathy) selectively increased HDAC4 expression. The role of HDAC4 was evaluated by in vivo gene silencing by intrarenal lentiviral gene delivery and found to reduce renal injury in diabetic rats. Podocyte injury was associated with suppressing autophagy and exacerbating inflammation by HDAC4-STAT1 signaling in vitro. Thus, HDAC4 contributes to podocyte injury and is one of critical components of a signal transduction pathway that links renal injury to autophagy in diabetic nephropathy.

Correction of methylmalonic aciduria in vivo using a codon-optimized lentiviral vector

Methylmalonic aciduria is a rare disorder of organic acid metabolism with limited therapeutic options, resulting in high morbidity and mortality. Positive results from combined liver/kidney transplantation suggest, however, that metabolic sink therapy may be efficacious. Gene therapy offers a more accessible approach for the treatment of methylmalonic aciduria than organ transplantation. Accordingly, we have evaluated a lentiviral vector-mediated gene transfer approach in an in vivo mouse model of methylmalonic aciduria. A mouse model of methylmalonic aciduria (Mut(-/-)MUT(h2)) was injected intravenously at 8 weeks of age with a lentiviral vector that expressed a codon-optimized human methylmalonyl coenzyme A mutase transgene, HIV-1SDmEF1αmurSigHutMCM. Untreated Mut(-/-)MUT(h2) and normal mice were used as controls. HIV-1SDmEF1αmurSigHutMCM-treated mice achieved near-normal weight for age, and Western blot analysis demonstrated significant methylmalonyl coenzyme A enzyme expression in their livers. Normalization of liver methylmalonyl coenzyme A enzyme activity in the treated group was associated with a reduction in plasma and urine methylmalonic acid levels, and a reduction in the hepatic methylmalonic acid concentration. Administration of the HIV-1SDmEF1αmurSigHutMCM vector provided significant, although incomplete, biochemical correction of methylmalonic aciduria in a mouse model, suggesting that gene therapy is a potential treatment for this disorder.

Extracellular-regulated-kinase 5-mediated renal protection against ischemia-reperfusion injury

ERK5, a member of the mitogen activated protein kinase, expressed in the kidneys was smaller (∼80kDa) in apparent molecular mass compared to other organs (∼120kDa). A blocking peptide experiment confirmed that the ∼80kDa detected on Western blots was a specific band detected by the anti-ERK5 antibody. Expression of the known ERK5 variants ERK5a, b, c, and T confirmed that none of the known splice variants encoded for the renal-specific ∼80kDa protein. However, RT-PCR with primers targeting the potential splice sites did not reveal a novel transcript in the kidney. The smaller molecular mass of the kidney-specific ERK5-immunoreactive protein suggested that this cyto-protective molecule may not be fully functional in the kidneys. Lentivirus-mediated in vivo overexpression of full length ERK5 in the mouse kidneys provided protection against renal IR injury. The identity of the renal-specific ∼80kDa ERK5 remains unknown but a better understanding of the ERK5 expression and post-translational processing in the kidneys may reveal a novel strategy for renal protection.

Adeno-Associated Virus-Mediated Gene Transfer to Renal Tubule Cells via a Retrograde Ureteral Approach

Background/Aims

Gene therapy involves delivery of exogenous DNA to provide a therapeutic protein. Ideally, a gene therapy vector should be non-toxic, non-immunogenic, easy to produce, and efficient in protecting and delivering DNA into target cells.

Methods

Adeno-associated virus (AAV) offers these advantages and few, if any, disadvantages, and over 100 isolates exist. We previously showed that AAV-mediated gene therapy can be used to restore vision to patients with Leber's congenital amaurosis, a disease of childhood blindness.

Results

Here we show that novel recombinant AAV2/8 and AAV2/9 transduce kidney tubule cells with high efficiency both in vitroin cell culture and in vivoin mice. In addition, we adapted and modified a retrograde approach to allow for optimal transgene delivery to renal tubular cells that further minimizes the risk of an immunogenic reaction.

Conclusions

We believe that recombinant AAV2, especially AAV2/8, gene delivery to renal tubule cells via a retrograde approach represents a viable method for gene therapy for a multitude of renal disorders ranging from autosomal dominant polycystic kidney disease to acute kidney injury.

PRKX critically regulates endothelial cell proliferation, migration, and vascular-like structure formation

Angiogenesis is a fundamental step in several important physiological events and pathological conditions including embryonic development, wound repair, tumor growth and metastasis. PRKX was identified as a novel type-I cAMP-dependent protein kinase gene expressed in multiple developing tissues. PRKX has also been shown to be phylogenetically and functionally distinct from PKA. This study presents the first evidence that PRKX stimulates endothelial cell proliferation, migration, and vascular-like structure formation, which are the three essential processes for angiogenesis. In contrast, classic PKA demonstrated an inhibitory effect on endothelia vascular-like structure formation. Our findings suggest that PRKX is an important protein kinase engaged in the regulation of angiogenesis and could play critical roles in various physiological and pathological conditions involving angiogenesis. PRKX binds to Pin-1, Magi-1 and Bag-3, which regulate cell proliferation, apoptosis, differentiation and tumorigenesis. The interaction of PRKX with Pin-1, Magi-1 and Bag-3 could contribute to the stimulating role of PRKX in angiogenesis.

Lentiviral-human heme oxygenase targeting endothelium improved vascular function in angiotensin II animal model of hypertension

We examined the hypothesis that vascular and renal dysfunction caused by angiotensin II (Ang II) through increased levels of blood pressure, inflammatory cytokines, and oxidative stress in Sprague-Dawley rats can be prevented by lentiviral-mediated delivery of endothelial heme oxygenase (HO)-1. We targeted the vascular endothelium using a lentiviral construct expressing human HO-1 under the control of the endothelium-specific promoter VE-cadherin (VECAD-HO-1) and examined the effect of long-term human HO-1 expression on blood pressure in Ang II-mediated increases in blood pressure and oxidant stress. A bolus injection of VECAD-HO-1 into the renal artery resulted in expression of human HO-1 for up to 6-9 weeks. Sprague-Dawley rats were implanted with Ang II minipumps and treated with lentivirus carrying either the HO-1 or green fluorescent protein. Renal tissue from VECAD-HO-1-transduced rats expresses human HO-1 mRNA and proteins without an effect on endogenous HO-1. Infusion of Ang II increased blood pressure (p < 0.001) but decreased vascular relaxation in response to acetylcholine, endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS (peNOS) levels, and renal and plasma levels of adiponectin (p < 0.05); in contrast, plasma tumor necrosis factor-α and monocyte chemoattractant protein-1 levels increased. Ang II-treated animals had higher levels of superoxide anion and inducible nitric oxide synthase and increased urinary protein and plasma creatinine levels. Lentiviral transduction with the VECAD-HO-1 construct attenuated the increase in blood pressure (p < 0.05), improved vascular relaxation, increased plasma adiponectin, and prevented the elevation in urinary protein and plasma creatinine in Ang II-treated rats. Endothelial-specific expression of HO-1 also reduced oxidative stress and levels of inflammatory cytokines resulting in increased expression of the anti-apoptotic proteins phosphorylated AKT, phosphorylated AMP-activated protein kinase, peNOS, and eNOS. Collectively, these findings demonstrate that endothelial-specific increases in HO-1 expression attenuate Ang II hypertension and the associated vascular dysfunction that is associated with increases in adiponectin and peNOS and reductions in oxidative stress and levels of inflammatory cytokines.

Lentiviral-mediated RNA interference against TGF-beta receptor type II in renal epithelial and fibroblast cell populations in vitro demonstrates regulated renal fibrogenesis that is more efficient than a nonlentiviral vector

Background. Lentiviral constructs reportedly can integrate into the genome of non-dividing, terminally differentiated cells and dividing cells, for long-term gene expression. This investigation tested whether a third generation lentiviral-mediated small interfering RNA (siRNA) delivered into renal epithelial and fibroblast cells against type II transforming growth factor-beta receptor (siRNA-TBRII) could better attenuate renal fibrogenesis in comparison with a non-lentiviral construct. Methods. HIV-derived lentiviral and non-lentiviral constructs were used to transfect cells with siRNA-TBRII or siRNA-EGFP control. Human embryonic kidney (HEK-293T), renal epithelial cells (NRK-52E) and renal fibroblasts (NRK-49F) were transfected and gene silencing quantified (fluorescence microscopy, Western blotting, fluorescence-activated cell sorting). Renal fibrogenesis was assessed using extracellular matrix protein synthesis (fibronectin and collagen-III; Western immunoblot), and α-smooth muscle actin (α-SMA) was analysed as a marker of fibroblast activation and epithelial-to-mesenchymal transdifferentiation (EMT). Results. Lentiviral-mediated siRNA-TBRII significantly suppressed TBRII expression in all cell lines, and also significantly suppressed renal fibrogenesis. In comparison with the non-lentiviral construct, lentiviral-mediated siRNA-TBRII produced stronger and more persistent inhibition of collagen-III in NRK-49F cells, fibronectin in all renal cell lines, and α-SMA in renal epithelial cells. Conclusions. Lentiviral vector systems against TBRII can be delivered into renal cells to efficiently limit renal fibrogenesis by sequence-specific gene silencing.

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.

[Development of nucleic acid transfection technology to the kidney]

The kidney is one of the most important organs that play a crucial role in homeostasis and, therefore, congenital or acquired renal dysfunction causes refractory diseases, i.e., Alport's syndrome, Fabry's disease, diabetic nephropathy, IgA nephropathy, kidney cancer, transplant glomerulopathy. Nucleic acid transfection technology to the kidney is indispensable for the progress of biomedical research and the realization of gene therapy and nucleic acid drug for renal diseases. Control of renal nucleic acid transfection was difficult because of the structural complexity; however, the study of recombinant virus, synthetic carrier and physical force-mediated nucleic acid transfection to the kidney has advanced. Recombinant virus and synthetic carrier-mediated methods require long-term block of the blood or urinary flow for efficient transfection of nucleic acid because of the rich blood flow of the kidney. In contrast, physical force-mediated methods that transfect with nucleic acid via transient membrane permeability do not apprehend ischemia-reperfusion injury and, therefore, may be beneficial for nucleic acid transfection to the kidney. In this article, we collect the information of therapeutic gene, target molecule of the nucleic acid drug and target cells for renal diseases and structural property of the kidney from the point of view of nucleic acid transfection. Additively, current status of nucleic acid transfection technology to the kidney is reviewed.

Novel treatment for lithium-induced nephrogenic diabetes insipidus rat model using the Sendai-virus vector carrying aquaporin 2 gene

Congenital nephrogenic diabetes insipidus (NDI) is a chronic disorder involving polyuria and polydipsia that results from unresponsiveness of the renal collecting ducts to the antidiuretic hormone vasopressin. Either of the genetic defects in vasopressin V2 receptor or the water channel aquaporin 2 (AQP2) cause the disease, which interfere the water reabsorption at the epithelium of the collecting duct. An unconscious state including a perioperative situation can be life threatening because of the difficulty to regulate their water balance. The Sendai virus (SeV) vector system deleting fusion protein (F) gene (SeV/DeltaF) is considered most suitable because of the short replication cycle and nontransmissible character. An animal model for NDI with reduced AQP2 by lithium chloride was used to develop the therapy. When the SeV/DeltaF vector carrying a human AQP2 gene (AQP2-SeV/DeltaF) was administered retrogradely via ureter to renal pelvis, AQP2 was expressed in the renal collecting duct to reduce urine output and water intake by up to 40%. In combination with the retorograde administration to pelvis, this system could be the cornerstone for the applicable therapies on not only NDI patients but also other diseases associate with the medullary collecting duct.

Gene therapy targeting kidney diseases: routes and vehicles

Renal gene therapy may offer new strategies to treat diseases of native and transplanted kidneys. Several experimental techniques have been developed and employed using nonviral, viral, and cellular vectors. The most efficient viral vector for in vivo transfection appears to be adenovirus. In addition, enhanced naked plasmid techniques, such as the hemagglutinating virus of Japan (HVJ)-liposome method, electroporation, the hydrodynamic method, and ultrasound with microbubbles, are promising. Trapping genetically modified macrophages in the inflamed kidneys is an elegant method for site-specific gene delivery. The choice of delivery vehicle as well as the administration route determines the site of transduction. In conclusion, for both in vivo and ex vivo renal transfection, enhanced naked plasmids, adenoviruses, and modified cell vectors offer the best prospects for effective clinical application. Moreover, the development of safer and nonimmunogenic vectors may realize clinical renal gene therapy in the near future.

In vivo gene transfer into adult stem cells in unconditioned mice by in situ delivery of a lentiviral vector

The potential of in vivo lentivirus-mediated bone marrow stem cell gene transfer by bone cavity injection, which could take full advantage of any source of stem cells present there, has not been previously explored. Such an approach may avoid several difficulties encountered by ex vivo hematopoietic stem cell (HSC) gene transfer. We sought to determine if efficient gene transfer could be achieved in HSC and mesenchymal stem/progenitor cells (MSC) by intrafemoral injection of a lentivirus vector in mice. Four months after injection, up to 12% GFP-expressing cells were observed in myeloid and lymphoid subpopulations. Significant transduction efficiencies were seen in Lin(-)c-kit(+)Sca1(+) HSC/progenitors and CFU with multilineage potential, which were also confirmed by duplex PCR analysis of progenitor-derived colonies. Four months after secondary BMT, we observed 8.1 to 15% vector(+) CFU in all recipients. Integration analysis by LAM-PCR demonstrated that multiple transduced clones contributed to hematopoiesis in these animals. We also showed that GFP-expressing MSC retained multilineage differentiation potential, with 2.9 to 8.8% GFP-containing CFU-fibroblasts detected in both injected and BMT recipients. Our data provide evidence that adult stem cells in bone marrow can be efficiently transduced "in situ" by in vivo vector administration without preconditioning. This approach could lead to a novel application for treatment of human diseases.

Targeted killing effect of lentivirus-mediated CD/TK suicide genes on colorectal carcinoma cells

AIM: To investigate the killing effect of lentivirus-mediated double suicide genes under the regulation of kinase domain-containing receptor (KDR) promoter targeted on colorectal carcinoma cells.

METHODS: 293FT packaging cells were transfected by the constructed plasmids pLenti6/V5-D-KDR-CDglyTK and pLenti6/V5-D-GFP. After blasticidin selection and cell cloning, the infectious viruses were generated. Then SW620 (with KDR expression) and LS174T cells (without KDR expression) were transfected with the obtained viruses by lipofectamin 2000. The transfection efficacy was evaluated by the fluorecence microscopy. The expression of CDglyTK was detected by reverse transcription-polymerase chain reaction (RT-PCR). After treatment with 5-FC and GCV, the killing effects and bystander effect of CD/TK suicide genes on the two kinds of cell lines were assessed.

RESULTS: The transfection efficacy was not significantly different between SW620 and LS174T cells, and elevated with the increase of virus titer. RT-PCR demonstrated that CDglyTK was expressed only in SW620 cells infected by pLenti6/V5-D-KDR-CDglyTK but not in LS147T cells. For the transfected SW620 cells, the survival rate was 32.34% ± 2.42% or 30.56% ± 2.14% when GCV (100 mg/L) or 5-FC (2.0 g/L) was used alone, respectively, and it was 5.36% ± 1.55% when GCV and 5-FC were used in combination. For the transfected LS174T cells, the survival rate was 95.48% ± 1.70% when GCV and 5-FC were used in combination. SW620 cells had a higher sensitivity to the prodrugs than LS174T cells did (P < 0.001), and the effects of double suicide genes were markedly stranger than that of either single gene (P < 0.001). Considerable bystander effect was also observed. When the infected cells covered a percentage of 40%, the survival rate of SW620 cells was 11.42% ± 2.66%, while that of LS174T cells was 99.54% ± 2.61% after treatment with GCV and 5-FC. There was significant difference between the two kinds of cells (P < 0.001).

CONCLUSION: Lentivirus-mediated CD/TK suicide genes driven by KDR promoter have specific killing effect on colorectal carcinoma cells with KDR expression.

Protein Kinase X Activates Ureteric Bud Branching Morphogenesis in Developing Mouse Metanephric Kidney

The human protein kinase X (PRKX) gene was identified previously as a cAMP-dependent serine/threonine kinase that is aberrantly expressed in autosomal dominant polycystic disease kidneys and normally expressed in fetal kidneys. The PRKX kinase belongs to a serine/threonine kinase family that is phylogenetically and functionally distinct from classical protein kinase A kinases. Expression of PRKX activates cAMP-dependent renal epithelial cell migration and tubular morphogenesis in cell culture, suggesting that it might regulate branching growth of the collecting duct system in the fetal kidney. With the use of a mouse embryonic kidney organ culture system that recapitulates early kidney development in vitro, it is demonstrated that lentiviral vector-driven expression of a constitutively active, cAMP-independent PRKX in the ureteric bud epithelium stimulates branching morphogenesis and results in a 2.5-fold increase in glomerular number. These results suggest that PRKX stimulates epithelial branching morphogenesis by activating cell migration and support a role for this kinase in the regulation of nephrogenesis and of collecting system development in the fetal kidney.

In vivo correction of murine hereditary tyrosinemia type I by phiC31 integrase-mediated gene delivery

Phage phiC31 integrase is a site-specific recombinase that mediates efficient integration of circular extrachromosomal DNA into the host genome. Here, the integrase system was used to transfer the fumarylacetoacetate hydrolase (FAH) gene into the liver of mice affected with hereditary tyrosinemia type 1. Approximately 3.6% of transfected hepatocytes experienced an integration event. The absolute frequency of integration was 1/1374. A higher proportion of integrase-transfected FAH+ hepatocytes displayed abnormal morphology (bizarre nuclei, enlarged cells) on day 25 after gene transfer, compared to cells not receiving integrase. The increased frequency of these abnormal cells correlated with the amount of integrase plasmid administered, suggesting some form of integrase toxicity in Fah-/- livers. The abnormal hepatocyte appearance was transient and livers analyzed after longer selection (90 days) showed 60% repopulation with only normal healthy FAH+ hepatocytes. A total of seven different integration sites (accounting for >90% of integration) were identified. Serial transplantation of integrase-corrected hepatocytes to Fah-/- recipients was successful, suggesting long-term viability of corrected cells and persistent gene expression through many rounds of cell division. The stability of transgene expression, relatively high integration frequency, and significant site specificity that characterize the phiC31 integration system suggest that it may have utility in many gene therapy settings.

Newborn liver gene transfer by an HIV-2-based lentiviral vector

Newborn gene therapy, because it can prevent the damage caused by the onset of a disease, deserves specific attention. To evaluate gene transfer in tissues of newborn mice, we used a human immunodeficiency virus (HIV)-2 based lentiviral vector pseudotyped with vesicular stomatitis virus G glycoprotein expressing the green fluorescent protein reporter gene under the control of the cytomegalovirus promoter. We found that very low doses of HIV-2 could infect and be expressed in newborn mice. Under these conditions, the virus was preferentially expressed in the liver and hepatocytes were the predominant target. The treatment was not toxic, the infected liver cells proliferated and the transduced gene was stably expressed. Adult mice could be infected by HIV-2, but the vector was detected in the liver only utilizing the sensitive method of polymerase chain reaction coupled with Southern blot. Direct comparison between newborn and adult recipients demonstrated a much greater efficiency of liver transduction in the newborn mouse. These results indicate that the combination of early intervention and low multiplicity of infection may be a strategy for preferentially and efficiently targeting newborn liver for gene therapy applications.

Systemic administration of naked DNA with targeting specificity to mammalian kidneys

A major challenge for gene therapy is to be able to deliver efficiently the gene of interest to specific cell types. Here we describe a safe and simple effective naked DNA gene delivery method, via inferior vena cava (IVC) injection, to the recipient's kidneys. It was further demonstrated that gene expression was concentrated in the proximal tubular epithelial cells of the cortico-medullary region of the kidney. Confocal microscopy analyses demonstrated the presence of the exogenous DNA in the renal cell membrane 10 min postgene delivery. However, it was only by 30 min that the presence of the exogenous DNA could be detected in the cell cytoplasm and in the nuclei of the renal cells. Stable expression of the beta-galactosidase gene could be detected for up to 35 days and no toxicity or any adverse pathological effect associated with the delivery method could be observed. Importantly, this IVC gene delivery method could promote the targeting of genes to carcinoma established in the kidney of SCID mice. These results provide the first evidence to support that stable gene expression could be achieved in the renal cells of kidney and the established carcinoma in the kidneys following in vivo gene delivery with naked DNA and could therefore provide the potential to design protocols for the gene therapy of the kidney diseases.

Approaches and methods in gene therapy for kidney disease

Renal gene therapy may offer new strategies to treat diseases of native and transplanted kidneys. Several experimental techniques have been developed and employed using nonviral, viral, and cellular vectors. The most efficient vector for in vivo transfection appears to be adenovirus. Glomeruli, blood vessels, interstitial cells, and pyelum can be transfected with high efficiency. In addition, electroporation and microbubbles with ultrasound, both being enhanced naked plasmid techniques, offer good opportunities. Trapping of mesangial cells into the glomeruli as well as natural targeting of monocytes or macrophages to inflamed kidneys are elegant methods for site-specific delivery of genes. For gene therapy in kidney transplantation, hemagglutinating virus of Japan liposomes are efficient vectors for tubular transfection, whereas enhanced naked plasmid techniques are suitable for glomerular transfection. However, adenovirus offers the best opportunities in a renal transplantation setup because varying parameters of graft perfusion allows targeting of different cell types. In renal grafts, lymphocytes can be used for selective targeting to sites of inflammation. In conclusion, for both in vivo and ex vivo renal transfection, enhanced naked plasmids and adenovirus offer the best perspectives for effective clinical application. Moreover, the development of safer, nonimmunogenic vectors and the large-scale production could make clinical renal gene therapy a realistic possibility for the near future.

Modulation of renal glomerular disease using remote delivery of adenoviral-encoded solubletype II TGF-beta receptor fusion molecule

BACKGROUND

Systemic adenoviral (Ad) gene therapy for renal disorders is largely hampered by the unique architecture of the kidney. Consequently, currently available Ad vectors are of only limited therapeutic utility in the context of glomerular and fibroproliferative renal diseases.

METHODS

The Ad vectors studied in the context of blocking renal fibrosis were AdTbeta-ExR and AdCATbeta-TR. AdTbeta-ExR encodes a chimeric soluble molecule comprising the entire ectodomain of the human type II TGF-beta receptor, genetically fused to the Fc fragment of the human IgG1 (sTbetaRII), while AdCATbeta-TR encodes only the dominant-negative truncated ectodomain of the human type II TGF-beta receptor. The biologic activity of the type II TGF-beta receptor was evaluated in vitro by its ability to inhibit cellular proliferation and in vivo in a unilateral ureter obstruction fibrosis model. Renal targeting with sTbetaRII was evaluated immunohistochemically after intramuscular (IM) delivery of AdTbeta-ExR. The renal antifibrotic effect of the Ad vectors was evaluated in a lupus murine model with both light and electron microscopy and urinalysis.

RESULTS

sTbetaRII was detected in the glomeruli after remote IM injection of AdTbeta-ExR, but not the control AdCATbeta-TR, indicating renal deposition of the heterologous soluble fusion protein after its expression in the muscle and secretion into the circulation. AdTbeta-ExR, but not AdCATbeta-TR, could transiently inhibit mesangial expansion, glomerular hypercellularity, proteinuria and cortical interstitial fibrosis in a murine lupus model. However, the autoimmune renal disease eventually surpassed the antifibrotic effect.

CONCLUSIONS

These results indicate the superiority of a soluble type II TGF-beta receptor over a dominant-negative, non-soluble type II TGF-beta receptor in the context of blocking renal fibrosis in murine models.

Regulating gene expression using self-inactivating lentiviral vectors containing the mifepristone-inducible system

Methods to regulate gene expression in vitro and in vivo are currently areas of intense research. The present study, therefore, was designed to determine the efficacy of transgene expression using the GeneSwitch mifepristone-regulatable system within the context of an integrating HIV-1 vector. Lentiviral transfer plasmids expressing the red (DsRed2) and green fluorescent protein (EGFP) markers were constructed for in vitro assessment on the basal and mifepristone-induced cell activation levels by FACS analyses. In our design, efficient cell activation and transgene expression were found using a binary lentivector system i.e., the trans-activator, Switch, and the inducible promoter-transgene expression cassette were cloned into separate vectors. Note that the Switch trans-activator performed optimally when cloned into the reverse-orientation, but the inducible promoter containing lentivector did not appear to be dependent upon the orientation within the lentivector backbone. This binary lentivector system resulted in tightly regulated transgene expression, with low basal cell activation in the absence of mifepristone (MFP). Upon induction, a 41- to 275-fold increase in the number of DsRed2- and EGFP-positive cells were detected (n=3). To determine the inducing ability of the GeneSwitch, we cloned the human alpha(1)-antitrypsin cDNA into the optimal lentiviral vector and transduced HeLa and Huh7 cells at increasing lentivector doses as determined by p24 Gag ELISA. We found that MFP could induce the expression of hAAT protein in HeLa cells from 310 to 15,000 ng hAAT/10(6) cells/24 h, which was a 48-fold induction. Similar results were observed in huH7 cells. In all, this study demonstrates that the GeneSwitch system can be designed within the context of a lentiviral vector for in vitro gene transfer, and this may also provide a viable method for temporally regulating gene expression for therapeutic applications in vivo or ex vivo.

PEGylation of a vesicular stomatitis virus G pseudotyped lentivirus vector prevents inactivation in serum

One disadvantage of vesicular stomatitis virus G (VSV-G) pseudotyped lentivirus vectors for clinical application is inactivation of the vector by human serum complement. To prevent this, monomethoxypoly(ethylene) glycol was conjugated to a VSV-G-human immunodeficiency virus vector expressing Escherichia coli beta-galactosidase. The modification did not affect transduction efficiency in vitro and protected the vector from inactivation in complement-active human and mouse sera. Blood from mice dosed intravenously with either the unmodified or the PEGylated virus particles was assayed for active vector by a limiting-dilution assay to evaluate transduction efficiency and for p24, an indicator of the total number of virus particles present. PEGylation extended the circulation half-life of active vector by a factor of 5 and reduced the rate of vector inactivation in the serum by a factor of 1,000. Pharmacokinetic profiles for the total number of virus particles present in the circulation were unaffected by PEGylation. Modification of the vector with poly(ethylene) glycol significantly enhanced transduction efficiency in the bone marrow and in the spleen 14 days after systemic administration of the virus. These results, in concert with the pharmacokinetic profiles, indicate that PEGylation does protect the virus from inactivation in the serum and, as a result, improves the transduction efficiency of VSV-G pseudotyped lentivirus vectors in susceptible organs in vivo.

Perspectives for gene therapy in renal diseases

Somatic cell gene therapy has made considerable progress last five years and has shown clear success in some clinical trials. In the field of nephrology, both the elucidation of pathophysiology of renal diseases and the development of gene transfer technique have become driving force for new therapy of incurable renal diseases, such as Alport syndrome and polycystic kidney disease. Gene therapy of renal cancer, although its application is limited to advanced cancer, is the front-runner of clinical application. Erythropoietin gene therapy has provided encouraging results for the treatment of anemia in uremic rats and recently progressed to the inducible one in response to hypoxia. Gene therapy for glomerulonephritis and renal fibrosis showed prominent impact on experimental models, although the safety must be confirmed for prolonged treatment. Transplant kidney is an ideal material for gene modification and induction of tolerance in the transplant kidney is an attractive challenge. Emerging techniques are becoming available such as stem cell technology and messenger RNA silencing strategies. We believe that the future of gene therapy research is exciting and promising and it holds an enormous potential for clinical application.

Repopulation of rat liver by fetal hepatoblasts and adult hepatocytes transduced ex vivo with lentiviral vectors

Recent studies have shown that nondividing primary cells, such as hepatocytes, can be efficiently transduced in vitro by human immunodeficiency virus-based lentivirus vectors. Other studies have reported that, under certain conditions, the liver can be repopulated with transplanted hepatocytes. In the present study, we combined these procedures to develop a model system for ex vivo gene therapy by repopulating rat livers with hepatocytes and hepatoblasts transduced with a lentivirus vector expressing a reporter gene, green fluorescent protein (GFP). Long-term GFP expression in vivo (up to 4 months) was achieved when the transgene was driven by the liver-specific albumin enhancer/promoter but was silenced when the cytomegalovirus (CMV) enhancer/promoter was used. Transplanted cells were massively amplified ( approximately 10 cell doublings) under the influence of retrorsine/partial hepatectomy, and both repopulation and continued transgene expression in individual cells were documented by dual expression of a cell transplantation marker, dipeptidyl peptidase IV (DPPIV), and GFP. In this system, maintenance or expansion of the transplanted cells did not depend on expression of the transgene, establishing that positive selection is not required to maintain transgene expression following multiple divisions of transplanted, lentivirus-transduced hepatic cells. In conclusion, fetal hepatoblasts (liver stem/progenitor cells) can serve as efficient vehicles for ex vivo gene therapy and suggest that liver-based genetic disorders that do not shorten hepatocyte longevity or cause liver damage, such as phenylketonuria, hyperbilirubinemias, familial hypercholesterolemia, primary oxalosis, and factor IX deficiency, among others, might be amenable to treatment by this approach.

Gene delivery in renal tubular epithelial cells using recombinant adeno-associated viral vectors

Gene therapy has the potential to provide a therapeutic strategy for numerous renal diseases such as diabetic nephropathy, chronic rejection, Alport syndrome, polycystic kidney disease, and inherited tubular disorders. In previous studies using cationic liposomes or adenoviral or retroviral vectors to deliver genes into the kidney, transgene expression has been transient and often associated with adverse host immune responses, particularly with the use of adenoviral vectors. The unique properties of recombinant adeno-associated viral (rAAV) vectors permit long-term stable transgene expression with a relatively low host immune response. The purpose of the present study was to evaluate gene expression in the rat kidney after intrarenal arterial infusion of a rAAV (serotype 2) vector encoding green fluorescence protein (GFP) induced by a cytomegalovirus-chicken beta-actin hybrid promoter. The left kidney of experimental animals was treated with either saline or transduced with rAAV2-GFP (0.125 ml/100 g body wt, 1 x 10(10)/ml infectious units) through the renal artery. A time-dependent expression of GFP was observed in all kidneys injected with rAAV2-GFP, with maximal expression observed at 6 wk posttransduction. The expression of GFP was restricted to cells in the S(3) segment of the proximal tubule and intercalated cells in the collecting duct, the latter identified by co-localization with H(+)-ATPase. No transduction was observed in the glomeruli or the intrarenal vasculature. These studies demonstrate successful transgene expression in tubular epithelial cells, specifically in the S(3) segment of the proximal tubule and intercalated cells, after intrarenal administration of a rAAV vector and provide the impetus for further studies to exploit its use as a tool for gene therapy in the kidney.

Doxycycline-regulated lentiviral vector system with a novel reverse transactivator rtTA2S-M2 shows a tight control of gene expression in vitro and in vivo

Regulated expression of therapeutic genes is required for long-term gene therapy applications for many disorders. Here we describe a doxycycline (dox)-regulated lentiviral vector system consisting of two HIV-1-based self-inactivating viruses. One of the vectors is constitutively expressing a novel improved version of the tetracycline reverse transactivator rtTA2(S)-M2 and the other has a rtTA responsive promoter driving the expression of beta-galactosidase gene (lacZ). The rtTA2(S)-M2 has highly improved properties with respect to specificity, stability and inducibility. Functionality of the system by dox was confirmed after in vitro cotransduction of Chinese hamster ovary and human endothelial hybridoma (EAhy926) cells. Regulation of the system showed tight control of the gene expression. Dose dependence for dox was seen with concentrations that can be obtained in vivo with doses normally used in clinical practice. LacZ expression could be switched on/off during long-term (3 months) culturing of cotransduced cells. The system was next tested in vivo after cotransduction into rat brain and studying expression of the lacZ gene in dox-treated and control rats. Nested RT-PCR confirmed that the tight control of the gene expression was achieved in vivo. Also, X-gal staining showed positive cells in the dox-treated rats, but not in the controls 10 days after cotransduction with 4 days preceding treatment with dox. It is concluded that our doxycycline-regulated vector system shows significant potential for long-term gene therapy treatments.

In vivo correction of murine tyrosinemia type I by DNA-mediated transposition

Gene therapy applications of naked DNA constructs for genetic disorders have been limited because of lack of permanent transgene expression. This limitation, however, can be overcome by the Sleeping Beauty (SB) transposable element, which can achieve permanent transgene expression through genomic integration from plasmid DNA. To date, only one example of an in vivo gene therapy application of this system has been reported. In this report, we have further defined the activity of the SB transposon in vivo by analyzing the expression and integration of a fumarylacetoacetate hydrolase (FAH) transposon in FAH-deficient mice. In this model, stably corrected FAH(+) hepatocytes are clonally selected and stable integration events can therefore be quantified and characterized at the molecular level. Herein, we demonstrate that SB-transposon-transfected hepatocytes can support significant repopulation of the liver, resulting in long-lasting correction of the FAH-deficiency phenotype. A single, combined injection of an FAH-expressing transposon plasmid and a transposase expression construct resulted in stable FAH expression in approximately 1% of transfected hepatocytes. The average transposon copy number was determined to be approximately 1/diploid genome and expression was not silenced during serial transplantation. Molecular analysis indicated that high-efficiency DNA-mediated transposition into the mouse genome was strictly dependent on the expression of wild-type transposase.