Molecular therapy for renal diseases

Proximal tubulopathies associated with monoclonal light chains: the spectrum of clinicopathologic manifestations and molecular pathogenesis

CONTEXT

Lesions associated with monoclonal light and heavy chains display a variety of glomerular, tubular interstitial, and vascular manifestations. While some of the entities are well recognized, including light and heavy chain deposition diseases, AL (light chain) and AH (heavy chain) amyloidosis, and light chain ("myeloma") cast nephropathy, other lesions centered on proximal tubules are much less accurately identified, properly diagnosed, and adequately understood in terms of pathogenesis and molecular mechanisms involved. These proximal tubule-centered lesions are typically associated with monoclonal light chains and have not been reported in patients with circulating monoclonal heavy chains.

OBJECTIVE

To determine the incidence of proximal tubulopathies in a series of patients with monoclonal light chain-related renal lesions and characterize them with an emphasis on clinical correlations and elucidation of molecular mechanisms involved in their pathogenesis.

DESIGN

A study of 5410 renal biopsies with careful evaluation of light microscopic, immunofluorescence, and electron microscopic findings was conducted to identify these monoclonal light/heavy chain-related lesions. In selected cases, ultrastructural immunolabeling was performed to better illustrate and understand molecular mechanisms involved or to resolve specific diagnostic difficulties.

RESULTS

In all, 2.5% of the biopsies were diagnosed as demonstrating renal pathology associated with monoclonal light or heavy chains. Of these, approximately 46% were classified as proximal tubule-centered lesions, also referred to as monoclonal light chain-associated proximal tubulopathies. These proximal tubulopathies were divided into 4 groups defined by characteristic immunomorphologic manifestations associated with specific clinical settings.

CONCLUSIONS

These are important lesions whose recognition in the different clinical settings is extremely important for patients' clinical management, therapeutic purposes, and prognosis. These entities have been segregated into 4 distinct variants, conceptualized morphologically and clinically. Specific mechanisms involved in their pathogenesis are proposed.

Adeno-associated viral vector transduction of green fluorescent protein in kidney: effect of unilateral ureteric obstruction

OBJECTIVE

To evaluate adeno-associated virus (AAV) mediated renal gene transfer, by examining the localization and time course of gene expression in the kidneys of mice with unilateral ureteric obstruction (UUO) and controls. AAV is a replication-defective virus that has the potential to deliver genes into the kidney to improve renal damage after UUO.

MATERIALS AND METHODS

An AAV vector carrying a green fluorescent protein (GFP) reporter gene (rAAV-GFP) was used. In control mice, GFP expression was evaluated at 4, 7, 14 and 28 days after intrapelvic injection of rAAV or phosphate-buffered saline (PBS). In mice with UUO, the left ureter was obstructed, and 24 h later either rAAV or PBS was injected; GFP expression was evaluated 4, 7 and 14 days later by direct fluorescence.

RESULTS

In the control mice, at least 7 days was required to detect GFP expression, whereas after UUO, GFP expression was already evident at 4 days after injection. GFP was localized mainly to the medullary tubules.

CONCLUSIONS

This study shows successful transduction of GFP into mouse kidney using an AAV vector; GFP was expressed sooner in UUO kidneys than in the controls. These results show the feasibility of using AAV to transduce GFP into the obstructed kidney, and suggest that it might be useful in transducing therapeutically active agents.

Plasticity of mesangial cells: a basis for understanding pathological alterations

In the last two decades, the ability of mesangial cells to respond to various stimuli or injurious agents by altering their phenotype and function has become recognized. The plasticity of these mesangial cells has been linked to the morphological and functional alterations responsible for the pathologic findings. Many of the glomerular disorders target the mesangium as the primary and/or initial site of injury. Understanding how mesangial cells are altered in the various conditions provides a platform for conceptualizing pathologic mechanisms and defining key steps amenable to therapeutic intervention. The present paper reviews the normal and altered mesangium with an emphasis on mechanisms involved in alterations of mesangial homeostasis. Mesangial cells and matrix are very important in maintaining normal glomerular structure, and function and the plasticity of these cells is responsible for pathological manifestations, repair, and scarring. Our more sophisticated understanding of mesangial cell behavior and matrix biology provides very useful information to help design new therapeutic approaches to the treatment of renal diseases. The potential for bone marrow-derived cells to differentiate into mesangial cells and repopulate damaged mesangium, thus "healing" what is today considered to be irreversible damage represents an exciting new area of research.

Expression and localization of PDGF-B, PDGF-D, and PDGF receptor in the kidney of angiotensin II-infused rat

Lipid accumulation in the kidney is a marker of tissue damage and may play a role in the development of renal injury. We have previously shown that long-term administration of angiotensin II in rats causes increased expression of transforming growth factor-beta1, coupled with an accumulation of lipids in the tubular and vascular wall cells in the kidney. In this study, we examine the regulation of expression of platelet-derived growth factor (PDGF) and its receptor system and their co-localization with lipid deposits in the kidneys of angiotensin II-infused rats. Real-time RT-PCR showed that expression of PDGF-B, PDGF-D, and PDGF receptor-beta (PDGFR-beta) mRNA was increased by angiotensin II infusion, and in situ hybridization showed the co-localization of these mRNAs. Tubular cells that had increased PDGF-B mRNA expression were positive for lipid deposition and also for cellular proliferation, which was indicated by the presence of proliferating cell nuclear antigen. By contrast, in the kidneys of angiotensin II-infused rats, apoptosis occurred in tubular cells that contained deposits of iron but not lipids. The deposition of lipids and upregulation of PDGF-B, PDGF-D, and PDGFR-beta induced by administration of angiotensin II were all suppressed by the selective angiotensin II type 1 (AT(1)) receptor antagonist losartan, but not by the nonspecific vasodilator hydralazine. The findings that lipid accumulation, upregulation of PDGF-B, PDGF-D, and PDGFR-beta, and cellular proliferation were topologically associated and regulated in an AT(1) receptor-dependent manner in the kidney of angiotensin II-infused rats suggests that these phenomena are related.

An efficient gene transfer method mediated by ultrasound and microbubbles into the kidney

BACKGROUND

Safety issues are of paramount importance in clinical human gene therapy. From this point of view, it would be better to develop a novel non-viral efficient gene transfer method. Recently, it was reported that ultrasound exposure could induce cell membrane permeabilization and enhance gene expression.

METHODS

In this study, we examined the potential of ultrasound for gene transfer into the kidney. First, we transfected rat left kidney with luciferase plasmid mixed with microbubbles, Optison, to optimize the conditions (duration of ultrasound and concentration of Optison). Then, 4, 7, 14 and 21 days after gene transfer, luciferase activity was measured. Next, localization of gene expression was assessed by measuring luciferase activity and green fluorescent protein (GFP) expression. Expression of GFP plasmid was examined under a fluorescence microscope at 4 and 14 days after gene transfer. Finally, to examine the side effects of this gene transfer method, biochemical assays for aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN) and creatinine (Cre) were performed.

RESULTS

Optison and/or ultrasound significantly enhanced the efficiency of gene transfer and expression in the kidney. Especially, 70-80% of total glomeruli could be transfected. Also, a significant dose-dependent effect of Optison was observed as assessed by luciferase assay (Optison 25%: 12.5 x 10(5) relative light units (RLU)/g tissue; 50%: 31.3 x 10(5) RLU/g tissue; 100%: 57.9 x 10(5) RLU/g tissue). GFP expression could be observed in glomeruli, tubules and interstitial area. Results of blood tests did not change significantly after gene transfer.

CONCLUSIONS

Overall, an ultrasound-mediated gene transfer method with Optison enhanced the efficiency of gene transfer and expression in the rat kidney. This novel non-viral method may be useful for gene therapy for renal disease.

A realistic chance for gene therapy in the near future

The expanding knowledge of the genetic and cellular mechanisms of human diseases in the post-genomic era coupled with the development of different vector systems to efficiently transfer genes to a variety of cell types and organs in vivo gave rise to the concept of gene therapy as a promising therapeutic option for genetic and acquired diseases. Gene therapy has been the focus of both enthusiasm and critique in the past years. Major progress has been achieved in evaluating gene therapy in clinical trials. However, a number of hurdles must still be overcome to make gene therapy safe and applicable for human diseases. Increased knowledge of the interaction of the gene therapy vehicles with the host has resulted in modifications of existing and the development of new vector systems, as well as adjustments of future clinical applications. Adeno-associated virus vectors, retrovirus- and lentivirus-based vectors show great promise for the correction of monogenic diseases. Correction of the genetic defect can be attempted by either in vivo administration to directly target a diseased organ or by administration of ex vivo genetically modified cells, e.g., bone marrow stem cells. The lack of persistent expression and the immune responses of the host have limited the use of adenovirus vectors for the permanent correction of monogenic diseases. However, the ease of production and the number of cell types and organs that can be efficiently infected make adenovirus-based vectors a promising tool for applications where permanent gene expression is not the therapeutic goal or where the induction of immune responses is the desired response, as for genetic vaccines. Overall, gene therapy remains promising for the correction of genetic as well as acquired disorders, where permanent or transient expression of a gene product will be therapeutic.

Adenovirus-mediated gene transfer to renal glomeruli in rodents

BACKGROUND

The expression of foreign genes into renal glomerular cells holds enormous potential to modulate the outcome of renal diseases. Recombinant adenoviruses (rAds) are promising gene transfer vectors because they have the ability to infect a wide range of nondividing cells. However, despite the fact that renal glomeruli are easily accessible via the renal circulation, adenovirus-mediated gene transfer into rodent glomeruli has been problematic. Here, we described our experience using rAd vectors to express foreign genes in rodent renal glomeruli in vivo and in cultured human renal glomerular cells.

METHODS

We developed two techniques--the "portal clamping" and "prolonged renal infusion"--to infect mouse and rat renal glomeruli in vivo, respectively. We used E-1-deleted rAd vectors carrying the lacZ gene encoding beta-galactosidase (Ad. CBlacZ) under the control of the cytomegalovirus enhancer and chicken beta-actin promoter. Cultured human renal glomerular podocytes, endothelial and mesangial cells were grown following standard techniques. Transgene expression was evaluated by doing beta-galactosidase staining and reverse transcription-polymerase chain reaction studies.

RESULTS

We found that both a prolonged exposure and a high concentration of circulating adenoviral vectors were required to achieve efficient gene transfer to renal glomerular cells in rodents. The virus-mediated transgene expression in renal glomeruli lasted for at least 42 days in mice and 21 days in rats without causing significant renal injury.

CONCLUSIONS

These data demonstrate the feasibility of using rAd vectors as a tool to express foreign genes in rodent renal glomerular cells and suggest that all types of human renal glomerular cells are equally susceptible to rAd infection.

Monoclonal light chain--mesangial cell interactions: early signaling events and subsequent pathologic effects

Glomerulopathic monoclonal light chains (G-LC) interact with mesangial cells (MC), resulting in alterations of mesangial homeostasis. Early signaling events control mitogenic activities and cytokine production, which in turn participate in the subsequent pathologic events. Mesangial homeostasis is affected in two very different ways, depending on whether the G-LC is from a patient with light chain deposition disease (LCDD) or light chain-related amyloidosis (AL-Am). In contrast, tubulopathic (T)-LC chains from patients with myeloma cast nephropathy do not significantly interact with MC and result in no alterations in mesangial homeostasis. Therefore, understanding early events in the monoclonal LC-MC interactions is fundamental. MC in culture were exposed to LC obtained and purified from the urine of patients with plasma cell dyscrasias and biopsy-proven renal disease, including LCDD, AL-Am, and myeloma cast nephropathy. Incubation of MC with G-LC, but not T-LC, resulted in cytoskeletal and cell shape changes, activation of platelet-derived growth factor-beta (PDGF-beta) and its corresponding receptor, cytoplasmic to nuclear migration of c-fos and NF-kappa beta signals, and production of monocyte chemoattractant protein-1 (MCP-1), as well as increased expression of Ki-67, a proliferation marker. Although NF-kappa beta activation was directly related to MCP-1 production, c-fos activation regulated proliferative signals and cytoskeletal changes in MC. Amyloidogenic LC were avidly internalized by the MC, whereas LCDD-LC effector targets were located at the MC surface. These cellular events are likely initiated as a result of interactions of the G-LC with yet-uncharacterized MC surface receptors. Dissecting the events taking place when G-LC interact with MC may define potential important targets for selective therapeutic manipulation to ameliorate or prevent the glomerular injury that ensues.

Efficient gene transfer to rat renal glomeruli with recombinant adenoviral vectors

Recombinant adenoviruses are attractive vectors for renal gene transfer since they can efficiently transduce nondividing cells. However, despite the fact that renal glomeruli are easily accessible via the renal circulation, attempts to deliver foreign genes specifically into renal glomeruli, using adenoviral vectors, have had limited success in rodents. A simple intraarterial injection of adenoviral vectors into the renal circulation or incubation of the virus with the kidney for an extended period of time was found to be insufficient for this purpose. In this study, we have established an efficient gene transfer protocol to express foreign genes in rat renal glomerular cells, using adenoviral vectors. We demonstrated, for the first time, that rat glomerular endothelial cells could be efficiently transduced by slowly infusing a recombinant adenovirus (Ad.CBlacZ) into the right renal artery for a period of 15 min. High levels of lacZ expression were achieved in renal glomeruli without causing significant damage to renal glomeruli or other kidney structures. The virus-mediated expression lasted for at least 21 days. These data demonstrate the feasibility of using recombinant adenoviral vectors as a tool with which to study the effect of foreign gene expression on the structure and function of rat renal glomeruli in vivo.

Clinical and pathologic findings in two new allelic murine models of polycystic kidney disease

Patients with inherited cystic kidney diseases have progressive cystic dilation of nephrons with concomitant loss of functional renal parenchyma and renal failure. Animal models of inherited cystic kidney disease are useful for study of the pathogenesis and molecular basis of cystic renal diseases. This article describes the clinical and pathologic features in two spontaneously occurring murine models of inherited polycystic kidney disease due to independent allelic mutations on mouse chromosome 8. The mutations, designated kat and kat2J, affect a chromosomal segment homologous to a region of human chromosome 4q35; the altered gene has not yet been identified. An allelism test showed that the mutations are at the same locus. The phenotype, inherited as an autosomal recessive, is more severe in kat2J/kat2J mice. Their kidneys are morphologically normal at birth, but by 3 mo of age, cysts affect all levels of the nephron. Adult males have testicular hypoplasia and they are sterile. A few of the oldest kat2J/kat2J mice have focal portal bile duct proliferation and dilation. kat2J/kat2J mice develop anemia and uremia and die before 1 yr of age. In kat/kat mice, the renal cystic disease progresses more slowly but is morphologically similar to that of kat2J/kat2J mice. The progressive cystic transformation of the kidneys in these allelic murine models resembles that seen in humans with autosomal dominant polycystic kidney disease.

Transduction of renal cells in vitro and in vivo by adeno-associated virus gene therapy vectors

There has been an increasing interest recently in the possibility of treating renal diseases using gene therapy. The ability to pursue gene therapy for renal diseases has been limited by the availability of an adequate system for gene delivery to the kidney. Adeno-associated virus (AAV) is a defective virus of the parvovirus family that has a number of properties attractive for renal gene delivery: recombinant AAV contains no viral genes; expression of genes delivered by these vectors does not activate cell-mediated immunity; the virus is able to transduce nondividing as well as dividing cells; and both wild-type and recombinant AAV integrate into the host chromosome resulting in long-term gene expression. Studies were performed to determine whether AAV can deliver reporter genes to kidney cells in vitro and in vivo. These studies show that AAV can deliver reporter genes with approximately equal efficiency to human mesangial, proximal tubule, thick ascending limb, collecting tubule, and renal cell carcinoma cells in primary culture. Immortalized mouse mesangial cells are transduced at a much greater efficiency. Transduction can be enhanced by pharmaceutical agents up to sevenfold in primary cells (transducing up to 20% of primary cells per well) and as much as 400-fold in immortalized mesangial cells. AAV delivered in vivo by intraparenchymal injection results in at least 3 mo of reporter gene expression in tubular epithelial, but not glomerular or vascular, cells at the injection site. These data indicate that AAV can deliver genes to renal cells both in vitro and in vivo resulting in prolonged gene expression, and thus AAV can be a useful tool for renal gene delivery.

Antisense oligonucleotides targeting malarial aldolase inhibit the asexual erythrocytic stages of Plasmodium falciparum

A major obstacle in the global effort to control malaria is the paucity of anti-malarial drugs. This is compounded by the continuing emergence and spread of resistance to old and new anti-malarial drugs in the malarial parasites. Here we describe the anti-malarial effect of phosphorothioate antisense (AS) oligodeoxynucleotides (ODNs) targeting the aldolase enzyme of Plasmodium falciparum, using the asexual blood stages of the parasite grown in vitro. The blood stages of P. falciparum depend almost entirely on the energy produced by their own glycolysis. Aldolase, the fourth enzyme of the glycolytic pathway, is highly upregulated during the malarial 48-h life cycle. We found that the mRNA of this enzyme can be inhibited, in a sequence specific manner, using AS-ODN to the splice sites on the pre-mRNA of malarial aldolase. At the enzyme level, both specific AS-ODNs for the splice sites, as well as for the translation initiation site on mature mRNA, can inhibit aldolase enzyme activity within the trophozoites of P. falciparum. Furthermore, this downregulation of the malarial aldolase results in a reduction in the production of ATP within the parasite. Finally, the treatment reduces parasitemia. In summary, AS-ODNs targeting the aldolase gene of P. falciparum can interfere with the blood-stage life cycle of this parasite in vitro by inhibiting the expression of the enzyme aldolase which results in decreased malarial glycolysis and energy production. Thus, we conclude that blockade of the expression of malarial glycolytic enzymes using specific AS-ODNs has the potential of a new anti-malarial strategy.

Gene transfer in the kidney

Gene transfer approaches offer the promise of revolutionizing medicine. In this review, we focus on the current and future prospects of somatic gene transfer into the kidney. The advantages and disadvantages of current vector systems are described, and the ex vivo and in vitro approaches applicable to the kidney are reviewed. We discuss uses of gene transfer approaches to dissect the pathogenesis of kidney disease and the future directions and applications of gene transfer to combat kidney destruction.

Etiology of Balkan endemic nephropathy: a multifactorial disease?

Balkan endemic nephropathy (BEN) is of great clinical importance in the restricted areas of Bulgaria, Rumania, Croatia, Serbia, Bosnia and Herzegovina. So far, studies on the etiological factors for BEN have not discovered any single environmental causative agent of this puzzling disease. These data reject the possibility of a purely environmental causation of BEN. The pattern of BEN transmission in the risk families is not typical for single gene disorders. Extensive epidemiological and genetic studies disclose characteristics of multifactorial (polygenic) inheritance of BEN. The evidences of 'familial tendency', variation of the risk for BEN depending on the number of sick parents and the degree of relatedness; the development of BEN in individuals from at-risk families who were born in non-endemic areas; the data that disease is not found in the gypsy population and the expressions of 3q25 cytogenetic marker suggest that the genetic factors play an important role as causative factors in BEN development. The possible impact of environmental triggers on individuals genetically predisposed to BEN could be supposed by the following data: the cytogenetic results of the increased frequency of folate sensitive Fra sites, spontaneous or radiation-induced aberrations in several bands in BEN patients, the data from the detailed analysis of breaks in BEN patients and controls that generate structural chromosome aberrations; the occurrence of BEN in immigrants. Genetical epidemiological approaches to etiology and prevention of BEN are proposed. The predisposing genes for BEN could be genes localized in a region between 3q25-3q26; transforming growth factor-beta (TGF-beta), genetic heterogeneity of xenobiotic-metabolizing enzymes; defects in the host's immune system. The predisposing genes for BEN patients with urinary tract tumors could be germline mutations in tumor suppressor genes and acquired somatic mutations in oncogenes.

The human plasminogen activator inhibitor type I gene promoter targets to kidney

The plasminogen activator inhibitor type 1 (PAI-1) gene encodes the physiological inhibitor of tissue-type and urokinase-type plasminogen activators and is induced by cytokines such as transforming growth factor-beta (TGF-beta). Studies have identified DNA sequence elements within the first 1.3 kb of the 5'-upstream DNA that mediate cytokine responsiveness in transfected cells in vitro. However, the DNA sequences that mediate PAI-1 expression in vivo have not yet been delineated. To define these regulatory sequences, we generated transgenic mice that expressed a hybrid gene comprising sequences between -1,272 and +75 of the human PAI-1 gene ligated to a LacZ reporter gene. Transgene expression detected in two independent lines was observed only in kidney from embryonic day 13 to adult and was seen primarily in proximal tubule cells of the outer medulla. Transgene expression and activity were unchanged in response to TGF-beta and remained restricted to kidney. Thus we have identified a promoter region within the PAI-1 gene that targets transgene expression to kidney but, unlike the native promoter, is unresponsive to TGF-beta in the experimental protocol used.

Strategies of gene transfer to the kidney

Kidney targeted gene transfer has been a realistic goal for many researchers since 1991, but unfortunately, to date there is no reliable gene transfer technique for gene therapy of renal diseases. However, at the experimental level, several in vivo gene transfer methods have attempted to target certain renal structures, for example, the HVJ-liposome method and renal perfusion of adenovirus for glomerular cells, intravenous injection of oligonucleotides (ODNs) for proximal tubule, intra-arterial injection of adenovirus followed by cold incubation with a vasodilator for interstitial vasculature of the outer medulla, and adenoviral injection into the renal pelvis for the inner medullary collecting duct. As an ex vivo gene transfer method targeting the glomerulus, the transfusion of genetically-modified mesangial cells has been attempted. Implantation of genetically-modified tubular epithelial cells into the subcapsular region has been employed for ex vivo transfection to the interstitium. Gene therapy has focused particularly on the transplanted kidney, where an exogenous gene can transferred in advance. In the future, an inducible system and individual cell targeting strategy should be developed. The improvement of gene transfer techniques, especially vectors for delivering genes, is crucial. The potential application of gene transfer technologies is enormous while the therapeutic approaches have just begun to be explored. Therapeutic interventions of the process of progression of glomerulonephritis in the rat have been directed towards inhibiting the actions of growth factors. Obviously, molecular biological intervention is coming of age and there is a tremendous excitement over its potential. We believe that gene transfer techniques will become common tools for the dissection of molecular aspects of diseases and possibly for gene therapy in the field of nephrology.