Prophylaxis of antibody-induced acute glomerulonephritis with genetically modified bone marrow-derived vehicle cells

Role of Macrophages and Related Cytokines in Kidney Disease

Inflammation is a key characteristic of kidney disease, but this immune response is two-faced. In the acute phase of kidney injury, there is an activation of the immune cells to fight against the insult, contributing to kidney repair and regeneration. However, in chronic kidney diseases (CKD), immune cells that infiltrate the kidney play a deleterious role, actively participating in disease progression, and contributing to nephron loss and fibrosis. Importantly, CKD is a chronic inflammatory disease. In early CKD stages, patients present sub-clinical inflammation, activation of immune circulating cells and therefore, anti-inflammatory strategies have been proposed as a common therapeutic target for renal diseases. Recent studies have highlighted the plasticity of immune cells and the complexity of their functions. Among immune cells, monocytes/macrophages play an important role in all steps of kidney injury. However, the phenotype characterization between human and mice immune cells showed different markers; therefore the extrapolation of experimental studies in mice could not reflect human renal diseases. Here we will review the current information about the characteristics of different macrophage phenotypes, mainly focused on macrophage-related cytokines, with special attention to the chemokine CCL18, and its murine functional homolog CCL8, and the macrophage marker CD163, and their role in kidney pathology.

Macrophage polarization in chronic kidney disease: a balancing act between renal recovery and decline?

Macrophages are heterogenous cells of the innate immune system that can fluidly modulate their phenotype to respond to their local microenvironment. They are found throughout the renal compartments, where they contribute to homeostasis and function. However, renal injury activates molecular pathways that initially stimulate differentiation of macrophages into a proinflammatory M1 phenotype. Later in the course of healing, abundant apoptotic debris and anti-inflammatory cytokines induce the production of anti-inflammatory M2 macrophages, which contribute to tissue regeneration and repair. Thus, the dynamic balance of M1 and M2 populations may outline the burden of inflammation and process of tissue repair that define renal outcomes, which has been the impetus for therapeutic efforts targeting macrophages. This review will discuss the role of these phenotypes in the progression of chronic renal injury, potential pathogenic mechanisms, and the promise of macrophage-based therapeutic applications for chronic kidney disease.

M2 macrophages in kidney disease: biology, therapies, and perspectives

Tissue macrophages are crucial players in homeostasis, inflammation, and immunity. They are characterized by heterogeneity and plasticity, due to which they display a continuum of phenotypes with M1/M2 presenting 2 extremes of this continuum. M2 macrophages are usually termed in the literature as anti-inflammatory and wound healing. Substantial progress has been made in elucidating the biology of M2 macrophages and their potential for clinical translation. In this review we discuss the current state of knowledge in M2 macrophage research with an emphasis on kidney disease. We explore their therapeutic potential and the challenges in using them as cellular therapies. Some new regulators that shape macrophage polarization and potential areas for future research are also examined.

Pathogenic and protective role of macrophages in kidney disease

Macrophages (MΦ) are located throughout kidney tissue, where they play important roles in homeostasis, surveillance, tolerance, and cytoprotection. MΦ are highly heterogeneous cells and exhibit distinct phenotypic and functional characteristics depending on their microenvironment and the disease type and stage. Recent studies have identified a dual role for MΦ in several murine models of kidney disease. In this review, we discuss the pathogenic and protective roles of the various MΦ subsets in experimental and human kidney diseases and summarize current progress toward the therapeutic use of MΦ in kidney diseases.

Mechanistic connection between inflammation and fibrosis

Fibrosis of the kidney is caused by the prolonged injury and deregulation of normal wound healing and repair processes, and by an excess deposition of extracellular matrices. Despite intensive research, our current understanding of the precise mechanism of fibrosis is limited. There is a connection between fibrotic events involving inflammatory and non-inflammatory glomerulonephritis, inflammatory cell infiltration, and podocyte loss. The current review will discuss the inflammatory response after renal injury that leads to fibrosis in relation to non-inflammatory mechanisms.

Macrophages in renal development, injury, and repair

Macrophages have long been regarded as classic mediators of innate immunity because of their production of proinflammatory cytokines and their ability to induce apoptotic cell death. As a result of such activities and the detrimental long-term effect of kidney inflammation, macrophages principally have been regarded as mediators of glomerular damage, tubular cell death, and the downstream fibrotic events leading to chronic kidney disease. Although this has been the accepted consequence of macrophage infiltration in kidney disease, macrophages also play a critical role in normal organ development, cell turnover, and recovery from injury in many organs, including the kidney. There is also a growing awareness that there is considerable heterogeneity of phenotype and function within the macrophage population and that a greater understanding of these different states of activation may result in the development of therapies specifically designed to capitalize on this variation in phenotype and cellular responses. In this review, we discuss the current understanding of induction and consequences of classic versus alternative macrophage activation and highlight what additional therapeutic options this may provide for the management of both acute and chronic kidney disease as well as renal cancer.

Macrophage diversity in renal injury and repair

Monocyte-derived macrophages can determine the outcome of the immune response and whether this response contributes to tissue repair or mediates tissue destruction. In addition to their important role in immune-mediated renal disease and host defense, macrophages play a fundamental role in tissue remodeling during embryonic development, acquired kidney disease, and renal allograft responses. This review summarizes macrophage phenotype and function in the orchestration of kidney repair and replacement of specialized renal cells following injury. Recent advances in our understanding of macrophage heterogeneity in response to their microenvironment raise new and exciting therapeutic possibilities to attenuate or conceivably reverse progressive renal disease in the context of fibrosis. Furthermore, parallels with pathological processes in many other organs also exist.

Ex vivo programmed macrophages ameliorate experimental chronic inflammatory renal disease

Macrophage infiltration of the kidney is a prominent feature associated with the severity of renal injury and progressive renal failure. To determine the influence of macrophages in renal disease models in the absence of endogenous T and B cells, we performed adoptive transfer of macrophages into severe combined immunodeficient (SCID) mice. In this study, macrophages were isolated from the spleens of BALB/c mice and stimulated with lipopolysaccharide to induce classically activated M1 macrophages or with interleukin-4 (IL-4) and IL-13 to induce alternatively activated M2 macrophages. These macrophages were then infused into SCID mice with adriamycin nephropathy; an in vivo model of chronic inflammatory renal disease analogous to human focal segmental glomerulosclerosis. Mice infused with M1 macrophages had a more severe histological and functional injury, whereas M2 macrophage-induced transfused mice had reduced histological and functional injury. Both M1 and M2 macrophages localized preferentially to the area of injury and maintained their phenotypes even after 4 weeks. The protective effect of M2 macrophages was associated with reduced accumulation and possibly downregulated chemokine and inflammatory cytokine expression of the host infiltrating macrophages. Our findings demonstrate that macrophages not only act as effectors of immune injury but can be induced to provide protection against immune injury.

Targeting genetically modified macrophages to the glomerulus

Macrophages are key players in the development of the majority of renal diseases and are therefore ideal cellular vectors for site specifically targeting gene therapy to inflamed glomeruli. Macrophages can be genetically modified using viral vectors ex vivo then re-introduced into the body where they can home to the diseased site. This review summarises current experience in efficiently targeting modified macrophages to the inflamed glomerulus focussing on the factors controlling macrophage localisation, macrophage gene transfer methods, in vivo gene delivery and results of recent investigations using modified macrophage gene therapy for glomerular disease.

Macrophages and the kidney

PURPOSE OF REVIEW

Macrophage infiltration is a hallmark of all forms of inflammatory and non-inflammatory renal injury. However, the classical view of macrophages as cells that cause injury has been superseded with evidence of their heterogeneous role, i.e. with involvement in all stages of the inflammatory process including tissue repair and healing. This review summarizes the major advances in macrophage biology achieved in the last year, highlighting the different activation states, how these are regulated, and their relevance in renal disease.

RECENT FINDINGS

New concepts have emerged concerning the factors controlling monocyte recruitment into inflamed tissue and their subsequent differentiation into activated macrophages. There is now compelling evidence for the heterogeneity of macrophages in clinical disease, i.e. they appear to be able to both promote and downregulate inflammation. An increased understanding of the factors regulating the expression of pro-inflammatory or reparative characteristics by macrophages is establishing how their function can be manipulated to attenuate renal inflammation in experimental models.

SUMMARY

An understanding of the role of macrophages at different time-points in renal inflammation, and the development of techniques for modulating macrophage activation in vivo, will provide a powerful method for exploiting the reparative attributes of these cells in clinical settings, restoring regulation to the inflammatory process and promoting healing.

Multiple facets of macrophages in renal injury

Macrophage infiltration is a common feature of renal disease and their presence has been synonymous with tissue damage and progressive renal failure. More recently work has focused on the heterogeneity of macrophage activation and in particular their ability to curtail inflammation and restore normal function. This has led to the view that it is macrophage function rather than their number that is important in determining the outcome of inflammatory disease. This review will focus on the pathways that regulate macrophage infiltration and activation and how these could be manipulated to control renal inflammatory disease. In particular, the ability of specific cell surface receptors and intracellular signaling pathways to control macrophage activation and how macrophages can be genetically manipulated to develop properties that favor resolution over ongoing injury.

Gene therapy in renal diseases

Kidney-targeted gene therapy could be an ideal treatment for renal diseases since the therapeutic molecule is limited in the kidney and the systemic effect may be minimized. The technical development of the gene delivery to kidney and the identification of the responsive gene for a particular disease encourage the challenge to hereditary diseases. Collagen type IV reassembling was reported to be succeeded in Alport syndrome model by introduction of exogenous COL4A5 gene. Many gene therapies are evaluated in various glomerulonephritis models and unilateral ureteral obstruction (UUO) model, and favorable results are accumulated. Transplant kidney is an ideal target for gene therapy, by which ischemia reperfusion, acute rejection and chronic allograft nephropathy can be treated. The importation of the novel technology, for example hybrid stem cell-gene therapy could promote the gene therapy of renal diseases toward clinical application.

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.

Gene delivery using human cord blood-derived CD34+cells into inflamed glomeruli in NOD/SCID mice

BACKGROUND

Bone marrow reconstitution using genetically-modified hematopoietic stem cells has been reported to confer resistance to inflammation and prevent renal injury in glomerulonephritis. Although this strategy has potentials for clinical use, taking hematopoietic stem cells from bone marrow is highly stressful for patients. In this regard, umbilical cord blood may be a useful alternative and, therefore, we focused on their suitability as a source of hematopoietic stem cells for transplantation-based therapy for glomerulonephritis.

METHODS

CD34+ cells were obtained from human umbilical cord blood, retrovirally transduced with human beta-glucuronidase (HBG) gene, and transplanted into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. After confirming the successful chimerism, these mice were treated with lipopolysaccharide (LPS), and local HBG expression in glomeruli was examined using immunohistochemical analysis, HBG bioassay, and Western blot analysis.

RESULTS

Clonogenic assay showed that 88.4 +/- 5.9% burst-forming unit-erythroid (BFU-E), 79.7 +/- 11.4% in colony-forming unit-macrophage (CFU-M), and 81.1 +/- 14.1% in colony-forming unit-granulocyte (CFU-G), respectively, possessed the transgene after transfection, suggesting that precommited cells were susceptible to retroviral infection. Flow cytometric analysis revealed that 24.1 +/- 14.5% of bone marrow cells in these chimera mice expressed human lymphocyte antigen (HLA) 8 weeks after transplantation. Also, clonogenic assay showed that a sustained engraftment of human hematopoietic cells expressed HBG. CD14-positive cells were recruited into the glomeruli upon LPS treatment and they secreted bioactive HBG, suggesting that cord blood-derived CD34+cells may differentiate into monocyte lineage while maintaining the expression of the transgene.

CONCLUSION

These data indicate that umbilical cord blood cells can be utilized as a source of hematopoietic stem cells for the transplantation-based therapy of glomerulonephritis.

Stem cells in renal biology: bone marrow transplantation for the treatment of IgA nephropathy

The pathogenesis of IgA nephropathy (IgAN) is still obscure. In this study, we investigated whether the fundamental pathogenesis of IgAN lies in bone marrow stem cells (BMCs) and whether bone marrow transplantation from normal C57BL/6j (B6) mice can attenuate glomerular lesions in a murine IgAN model (high serum level IgA ddY mouse; HIGA mouse). Mesangial deposits of IgA and C3 and glomerular sclerosis in HIGA recipients of BMCs from B6 mice (B6-->HIGA) were decreased as compared with those in HIGA recipients of BMCs from HIGA mice (HIGA-->HIGA). Furthermore, the serum levels of IgA and macromolecular IgA were notably lower in B6-->HIGA mice than in HIGA-->HIGA mice. Of note, bone marrow derived H-2(b)-positive cells from B6 donors were observed in the glomeruli of H-2(b)-negative HIGA recipients. Our data suggest that qualitative and quantitative changes of serum IgA are determined at the level of stem cells and that bone marrow transplantation from normal mice may not only replace recipients' immune cells with donors' BMCs, but also regenerate glomerular cells in HIGA mice. This approach offers a promising strategy for the treatment of IgAN.

Targeting growth factors to the kidney: myth or reality?

Growth factors and cytokines play a crucial role in the progression of renal diseases. A growing body of evidence has been obtained from experimental studies, suggesting that manipulation of the activity of growth factors and cytokines is a potential form of therapy for renal diseases. To preserve the renal function structure in progressive renal diseases, this approach is achieved by inhibition of apoptosis of renal intrinsic cells and by decrease in the fibrotic signal. Inhibition of transforming growth factor beta, platelet-derived growth factor, interleukin-1 and tumor necrosis factor alpha, and supplementation of hepatocyte growth factor, vascular endothelial growth factor and bone morphogenic protein-7 may be beneficial. Recent progress in therapeutic implements including humanized antibodies, chimeric soluble receptors, aptamers, antisense oligonucleotides, and gene therapy allow us to target the causal molecules. Administration of a combination of growth factors and cytokines is a potential therapeutic approach. Targeting signal transduction molecules and their co-factors and regulators is another possibility because the signals from various growth factors use a common pathway. Thus, targeting growth factors and cytokines in renal diseases could be a promising therapeutic approach.

Inflamed glomeruli-specific gene activation that uses recombinant adenovirus with the Cre/loxP system

The authors previously reported that bone marrow-derived CD11b(+)CD18(+) cells could be used as a vehicle to deliver foreign genes into inflamed glomeruli and that this vehicle cell (v-cell) could retard the progression of nephritis by delivering anti-inflammatory molecules. As a next step, the authors tried to establish a switching system by which v-cells are activated only at the inflamed glomeruli. A recombinant adenovirus (Ad) that expressed Cre recombinase under the control of the interleukin-1 beta (IL-1 beta) promoter (AxIL-1pr/Cre) was constructed and transfected into v-cells. After confirming that AxIL-1pr/Cre expresses Cre by lipopolysaccharide (LPS) treatment, AxIL-1pr/Cre was infected together with another Ad bearing a switching reporter unit in which the LacZ gene is activated under the control of the CAG promoter by the Cremediated excisional deletion of interposed stuffer DNA. Only a negligible number of double-infected (Cre/loxPCAG) cells expressed LacZ. This number, however, was significantly increased by LPS, which suggests that LPS-induced Cre effectively deletes the stuffer DNA, which allows for a complete CAG promoter. DBA/2j mice were then transplanted with Cre/loxPCAG cells via a tail vein and treated with anti-glomerular basement membrane (GBM) serum. To trace the transplanted cells, marker v-cells, infected with AxCANLacZ to constitutively express the LacZ gene, were also used. Although transplanted cells expressing LacZ collected in the spleen independent of anti-GBM treatment, they did not express the LacZ gene in the mice transplanted with Cre/loxPCAG cells. On the other hand, transplanted cells were recruited in the glomeruli and expressed the LacZ gene upon anti-GBM treatment. These results suggested that only the v-cells recruited in the glomeruli could be switched on and activate foreign genes.

Genetically modified bone marrow continuously supplies anti-inflammatory cells and suppresses renal injury in mouse Goodpasture syndrome

In chronic inflammation, macrophages and neutrophils, which are derived from bone marrow, play a pivotal role. Therefore, reconstitution of bone marrow with anti-inflammatory stem cells may modify inflammation. In this study, transplantation-based gene therapy was applied to glomerular inflammation for a long-lasting suppression of the glomerular damage seen in chronic nephritis. Bone marrow cells were harvested from male donor mice, which had received 5-fluorouracil 3 days previously, and transduced with an interleukin 1 (IL-1) receptor antagonist (IL-1Ra) or a mock gene using a retrovirus vector. After confirmation that transduced cells possessed the transgene at approximately 0.7 copies per cell and secreted recombinant IL-1Ra, these cells were infused into sublethally irradiated (6 Gy) female recipients once daily for 4 consecutive days. These female recipient mice had the male Y antigen in bone marrow, liver, and spleen, and 10% to 20% of their spleen cells possessed the transgene even 8 weeks after transplantation. Glomerulonephritis was then induced in these mice. Renal function and histology were retarded in the mice whose bone marrow was reconstituted with IL-1Ra-producing cells compared with mock transduced cells. In situ hybridization using a Y painting probe revealed that transplanted donor cells were recruited into the glomerulus upon induction of nephritis, suggesting therapeutic effects were channeled through the secretion of IL-1Ra from these cells. Furthermore, the survival rate after a second challenge with nephrotoxic antibody was significantly improved in the IL-1Ra chimera. These results suggest that reconstitution of bone marrow for continuous supply of anti-inflammatory cells may be a useful strategy for the treatment of chronic inflammation.

Macrophages in renal inflammation

This review describes recent advances in macrophage biology in the context of renal inflammation. It highlights the importance of the activated macrophage for the progression and resolution of renal disease, and discusses recent and potential future approaches to modify macrophage function selectively within the kidney to activate them specifically to promote the healing of kidney disease.

Macrophages transfected with adenovirus to express IL-4 reduce inflammation in experimental glomerulonephritis

Nephrotoxic nephritis (NTN) is characterized by acute macrophage-dependent inflammation and serves as a model of human glomerulonephritis. In this study we have transfected rat macrophages with recombinant adenovirus expressing IL-4 (Ad-IL4) and demonstrated that these transfected macrophages develop fixed properties as a result of transfection, as shown by reduced NO production in response to IFN-gamma and TNF. Ad-IL4-transfected macrophages localized with enhanced efficiency to inflamed glomeruli after renal artery injection in rats with NTN compared with adenovirus expressing beta-galactosidase (Ad-beta gal)-transfected macrophages and produced elevated levels of the cytokine in glomeruli in vivo for up to 4 days. The delivery of IL-4-expressing macrophages produced a marked reduction in the severity of albuminuria (day 2 albuminuria, 61 +/- 15 mg/24 h) compared with unmodified NTN (day 2 albuminuria, 286 +/- 40 mg/24 h; p < 0.01), and this was matched by a reduction in the number of ED1-positive macrophages infiltrating the glomeruli. Interestingly, the injection of IL-4-expressing macrophages into single kidney produced a marked reduction in the numbers of ED1-positive macrophages in the contralateral noninjected kidney, an effect that could not be mimicked by systemic delivery of IL-4-expressing macrophages. This implies that the presence of IL-4-expressing macrophages in a single kidney can alter the systemic development of the inflammatory response. Macrophage transfection and delivery provide a valuable system to study and modulate inflammatory disease and highlight the feasibility of macrophage-based gene therapy.

Genetically modified bone marrow-derived vehicle cells site specifically deliver an anti-inflammatory cytokine to inflamed interstitium of obstructive nephropathy

In this study, we used genetically modified bone marrow-derived CD11b(+)CD18(+) vehicle cells to deliver IL-1 receptor antagonist (IL-1ra) for treatment of inflamed renal interstitium in an animal model of unilateral ureteral obstruction (UUO). Vehicle cells that expressed the ICAM-1 ligands, CD11b and CD18, were obtained from bone marrow cells of DBA/2j mice and adenovirally transduced with the IL-1ra gene or glucocerebrosidase (GC) gene ex vivo. In kidneys treated to develop UUO, levels of ICAM-1, IL-1 beta, and IL-1R expression increased within 3 days compared with contralateral untreated kidneys in the same mice. Similarly, the macrophage infiltration in the cortical interstitium increased after 3 days in UUO kidneys, but not untreated kidneys. After UUO developed, DBA/2j mice were injected i.v. with either IL-1ra(+) vehicle cells (IL-1ra-treated mice) or GC(+) vehicle cells (GC-treated mice) at 24 h after UUO. Six days after the injection of these vehicle cells, marked increase of CD11b(+) IL-1ra(+) vehicle cells was observed in the ICAM-1-positive interstitium of UUO kidneys from IL-1ra-treated mice. In contrast, no CD11b(+) IL-1ra(+) cells appeared in ICAM-1-negative contralateral kidneys from these mice. Furthermore, the infiltration of macrophages (p < 0.001), expression of ICAM-1 (p < 0.005), and presence of alpha-smooth muscle actin (p = 0.005) in the interstitium of UUO kidneys were significantly decreased in IL-1ra-treated mice compared with GC-treated mice. These findings suggest that IL-1 may contribute to the development of renal interstitial injury and that our method can deliver a functioning gene encoding an antiinflammatory cytokine gene specifically at that site by interacting with local adhesion molecules.

Gene therapy for kidney disease

Gene therapy has distinct potential to treat disease at the most fundamental level. However, the ability to pursue gene therapy for renal disease has been limited by the availability of an adequate system for gene delivery to the kidney and for regulation of transgene expression. Presently, there are several limitations to overcome before clinical use of viral vector systems for targeting kidney can be considered. Non-viral vectors such as haemagglutinating virus of Japan (HVJ)-liposome mediated gene transfer and cationic liposome are promising but need to be improved. Given that the systemic delivery of the functional protein can serve as therapy for the renal diseases, skeletal muscle targeting gene therapy might be an alternative strategy for the treatment of renal disease. Gene therapy to the transplant kidney may potentially improve the graft outcome by reducing acute and chronic rejection. We review emerging strategies of gene transfer with reference to the kidney and discuss the potential application of gene therapy to renal diseases.