Reduction of chronic rejection of renal allografts by anti-transforming growth factor-β antibody therapy in a rat model

Klotho and Mesenchymal Stem Cells: A Review on Cell and Gene Therapy for Chronic Kidney Disease and Acute Kidney Disease

Chronic kidney disease (CKD) and acute kidney injury (AKI) are public health problems, and their prevalence rates have increased with the aging of the population. They are associated with the presence of comorbidities, in particular diabetes mellitus and hypertension, resulting in a high financial burden for the health system. Studies have indicated Klotho as a promising therapeutic approach for these conditions. Klotho reduces inflammation, oxidative stress and fibrosis and counter-regulates the renin-angiotensin-aldosterone system. In CKD and AKI, Klotho expression is downregulated from early stages and correlates with disease progression. Therefore, the restoration of its levels, through exogenous or endogenous pathways, has renoprotective effects. An important strategy for administering Klotho is through mesenchymal stem cells (MSCs). In summary, this review comprises in vitro and in vivo studies on the therapeutic potential of Klotho for the treatment of CKD and AKI through the administration of MSCs.

Approaches for Controlling Antibody-Mediated Allograft Rejection Through Targeting B Cells

Both acute and chronic antibody-mediated allograft rejection (AMR), which are directly mediated by B cells, remain difficult to treat. Long-lived plasma cells (LLPCs) in bone marrow (BM) play a crucial role in the production of the antibodies that induce AMR. However, LLPCs survive through a T cell-independent mechanism and resist conventional immunosuppressive therapy. Desensitization therapy is therefore performed, although it is accompanied by severe side effects and the pathological condition may be at an irreversible stage when these antibodies, which induce AMR development, are detected in the serum. In other words, AMR control requires the development of a diagnostic method that predicts its onset before LLPC differentiation and enables therapeutic intervention and the establishment of humoral immune monitoring methods providing more detailed information, including individual differences in the susceptibility to immunosuppressive agents and the pathological conditions. In this study, we reviewed recent studies related to the direct or indirect involvement of immunocompetent cells in the differentiation of naïve-B cells into LLPCs, the limitations of conventional methods, and the possible development of novel control methods in the context of AMR. This information will significantly contribute to the development of clinical applications for AMR and improve the prognosis of patients who undergo organ transplantation.

Methamphetamine facilitates pulmonary and splenic tissue injury and reduces T cell infiltration in C57BL/6 mice after antigenic challenge

Methamphetamine (METH) is a strong addictive central nervous system stimulant. METH abuse can alter biological processes and immune functions necessary for host defense. The acquisition and transmission of HIV, hepatitis, and other communicable diseases are possible serious infectious consequences of METH use. METH also accumulates extensively in major organs. Despite METH being a major public health and safety problem globally, there are limited studies addressing the impact of this popular recreational psychostimulant on tissue adaptive immune responses after exposure to T cell dependent [ovalbumin (OVA)] and independent [lipopolysaccharide (LPS)] antigens. We hypothesized that METH administration causes pulmonary and splenic tissue alterations and reduces T cell responses to OVA and LPS in vivo, suggesting the increased susceptibility of users to infection. Using a murine model of METH administration, we showed that METH causes tissue injury, apoptosis, and alters helper and cytotoxic T cell recruitment in antigen challenged mice. METH also reduces the expression and distribution of CD3 and CD28 molecules on the surface of human Jurkat T cells. In addition, METH decreases the production of IL-2 in these T-like cells, suggesting a negative impact on T lymphocyte activation and proliferation. Our findings demonstrate the pleotropic effects of METH on cell-mediated immunity. These alterations have notable implications on tissue homeostasis and the capacity of the host to respond to infection.

Assessment of treatment efficacy using surface-enhanced Raman spectroscopy analysis of urine in rats with kidney transplantation or kidney disease

BACKGROUND

Individuals who have kidney disease or kidney transplants need routine assessment of their kidney damage and function, which are largely measured based on histological examination of kidney biopsies, blood test, and urinalysis. These methods are practically difficult or inconvenient, and expensive. The objective of this study was to develop a model to estimate the kidney damage and function by surface-enhanced Raman spectroscopy (SERS).

METHODS

Urine samples were collected from two previous studies: renal allograft recipient Lewis rats receiving anti-TGF-β antibody or control antibody treatment and obese diabetic ZSF1 rats with kidney disease fed with whole grape powder-containing chow or control chow. Silver nanoparticle-based SERS spectra of urine were measured. SERS spectra were analyzed using principal component analysis (PCA) combined with linear discriminant analysis (LDA) and partial least squires (PLS) analysis.

RESULTS

PCA/LDA separated anti-TGF-β antibody-treated group from control group with 90% sensitivity and 70% specificity in kidney transplants, and grape-fed group from controls with 72.7% sensitivity and 60% specificity in diabetic kidneys. The receiver operating characteristic curves showed that the integration area under the curve was 0.850 ± 0.095 (p = 0.008) in kidney transplant groups and 0.800 ± 0.097 (p = 0.02) in diabetic kidney groups. PLS predicted the biochemical parameters of kidney function using the SERS spectra, resulting in R² = 0.8246 (p < 0.001,urine protein), R² = 0.8438 (p < 0.001, urine creatinine), R² = 0.9265 (p < 0.001, urea), R² = 0.8719 (p < 0.001, serum creatinine), and R² = 0.6014 (p < 0.001, urine protein to creatinine ratio).

CONCLUSION

Urine SERS spectral analysis suggesting that it may become a convenient method for rapid assessment of renal impairment.

Serological cytokine profiles of cardiac rejection and lung infection after heart transplantation in rats

BACKGROUND

Allograft rejection and infection are the major sources of morbidity and mortality after heart transplant. Early differential diagnosis is clinically crucial but difficult. The aim of the study was to examine serum cytokine profiles associated with each entity and whether such profiles could help to differentiate between them.

METHODS

Heart allografts from Wistar rats were transplanted to Lewis rats as described by Yokoyama. Cardiac rejection and pulmonary bacterial infection were induced by Cyclosporine cessation and bacteria bronchus injection, and pathologically confirmed. Ninety serological cytokines profiles of the study objects were then simultaneously measured using a biotin label-based cytokine array. The fold change (FC) was used for relative cytokine concentration comparison analysis.

RESULTS

Four cytokines in cardiac rejection group were significantly dysregulated as compared to health controls (β -Catenin, 0.51 FC; E-Selectin, 0.62 FC; IFN-gamma, 1.87 FC; and IL-13, 0.60 FC, respectively). In pulmonary infection animals, 11 cytokines were remarkably dysregulated in comparison with the control group (CINC-3, 0.57 FC; CNTF R alpha, 0.59 FC; E-Selectin, 0.58 FC; FSL1,0.62 FC; Hepassocin, 0.64 FC; IL-2, 0.26 FC; IL-13, 0.49 FC; NGFR, 0.57 FC; RAGE, 0.50 FC; TIMP-1, 0.49 FC; and IFN-gamma, 1.77 FC, respectively). Eleven cytokines were significantly up-regulated in cardiac rejection group comparing to the pulmonary infection animals (FSL1, 2.32FC; Fractalkine, 1.65FC; GFR alpha-1, 1.64FC; IL-2, 2.72FC; IL-5, 1.60FC; MMP-2, 1.71FC; NGFR, 2.25FC; TGF-beta1, 1.58FC; TGF-beta3, 1.58FC; Thrombospondin, 1.64FC, and TIMP-1, 1.52FC, respectively).

CONCLUSIONS

The current study illustrated the disease-specific serological cytokine profiles of allograft rejection and pulmonary bacterial infection after cardiac transplant. Such disease associated cytokine portraits might have the potential for early discrimination diagnosis.

Galectin-1-induced tolerogenic dendritic cells combined with apoptotic lymphocytes prolong liver allograft survival

Donor-derived tolerogenic dendritic cells (DCs) and apoptotic lymphocytes (ALs) are practical tools for controlling rejection after transplantation by targeting direct and indirect allorecognition pathways, respectively. To date, few studies have investigated the combination of donor-derived tolerogenic DCs and ALs infusion in organ transplantation protection. In the present study, we generated galectin-1-induced tolerogenic DCs (DC_gal-1s) and ultraviolet irradiation-induced ALs with stable immune characteristics in vitro and potential immune regulatory activity in vivo. A rat model of acute liver transplant rejection was established, and the intrinsic tolerogenic profiles associated with the short-term alleviation of rejection and the long-term maintenance of tolerance in the absence of immunosuppressive drugs were evaluated. The DC_gal-1-AL treatment prolonged allograft survival more significantly than a transfusion of DC_gal-1s or ALs alone. This benefit was associated with CD4⁺ Treg cell expansion and decreased interferon (IFN)-γ⁺ T cell levels. Moreover, DC_gal-1-AL treatment led to different cytokine/chemokine changes in the allograft and peripheral blood, that indicated an alleviation of local and systemic inflammation on day 7 post-transplantation. TGF-β1 and TGF-β2 were significantly increased in the long-term surviving allografts after DC_gal-1-AL treatment. Our results indicate that the combination of DC_gal-1s with ALs effectively prolongs liver allograft survival and represents a novel therapeutic strategy for liver transplant rejection.

The role of klotho in chronic kidney disease

Chronic kidney disease (CKD) is an inherently systemic disease that refers to a long-term loss of kidney function. The progression of CKD has repercussions for other organs, leading to many kinds of extrarenal complications. Intensive studies are now being undertaken to reveal the risk factors and pathophysiological mechanism of this disease. During the past 20 years, increasing evidence from clinical and basic studies has indicated that klotho, which was initially known as an anti-aging gene and is mainly expressed in the kidney, is significantly correlated with the development and progression of CKD and its complications. Here, we discuss in detail the role and pathophysiological implications of klotho in ion disorders, the inflammation response, vascular calcification, mineral bone disorders, and renal fibrosis in CKD. Based on the pathogenic mechanism of klotho deficiency and klotho decline in urine early in CKD stage 2 and even earlier in CKD stage 1, it is not difficult to understand that soluble klotho can serve as an early and sensitive marker of CKD. Moreover, the prevention of klotho decline by several mechanisms can attenuate renal injuries, retard CKD progression, ameliorate extrarenal complications, and improve renal function. In this review, we focus on the functions and pathophysiological implications of klotho in CKD and its extrarenal complications as well as its potential applications as a diagnostic and/or prognostic biomarker for CKD and as a novel treatment strategy to improve and decrease the burden of comorbidity in CKD.

Arterial wall hypertrophy is ameliorated by α2-adrenergic receptor antagonist or aliskiren in kidneys of angiotensinogen-knockout mice

BACKGROUND

Arterial hypertrophy and interstitial fibrosis are important characteristics in kidneys of angiotensinogen-knockout (Atg ^-/-) mice. In these mice, which exhibit polyuria and hypotension, sympathetic nerve signaling is estimated to be compensatorily hyperactive. Furthermore, transforming growth factor (TGF)-β1 is overexpressed in mice kidneys. To determine whether sympathetic nerve signaling and TGF-β1 exacerbate arterial hypertrophy and interstitial fibrosis, intervention studies of such signaling are required.

METHODS

We performed renal denervation and administered the α2-adrenergic receptor (AR) antagonist, atipamezole, to Atg ^-/- mice. A renin inhibitor, aliskiren, which was preliminarily confirmed to reduce TGF-β1 gene expression in kidneys of the mice, was additionally administered to assess the effect on the arterial hypertrophy and interstitial fibrosis.

RESULTS

Norepinephrine content in kidneys of Atg ^-/- mice was three times higher than in kidneys of wild-type mice. Interventions by renal denervation and atipamezole resulted in amelioration of the histological findings. Overexpression of TGF-β1 gene in kidneys of Atg ^-/- mice was altered in a manner linked to the histological findings. Surprisingly, aliskiren reduced α2-AR gene expression, interstitial fibrosis, and arterial hypertrophy in kidneys of Atg ^-/- mice, which lack renin substrate.

CONCLUSIONS

Alpha2-AR signaling is one of the causes of persistent renal arterial hypertrophy in Atg ^-/- mice. Aliskiren also angiotensinogen-independently reduces the extent of renal arterial hypertrophy, partly thorough downregulation of α2-ARs. Although renal arterial hypertrophy in Atg ^-/- mice appears to be of multifactorial origin, TGF-β1 may play a key role in the persistence of such hypertrophy.

Nephrotoxicity Induced by Cisplatin Intake in Experimental Rats and Therapeutic Approach of Using Mesenchymal Stem Cells and Spironolactone

Chronic kidney disease may lead to subsequent tissue fibrosis. However, many factors can combat injurious stimuli in these tissues aiming to repair, heal, and alleviate any disturbance. Chemokines release, migration of inflammatory cells to the affected site, and activation of fibroblasts for the production of extracellular matrix are commonly observed in this disease. In the last years, many studies have focused on spironolactone (SPL), a mineralocorticoid receptor antagonist, and its pharmacological effects. In the present study, SPL was selected as an anti-inflammatory agent to combat nephrotoxicity and renal fibrosis induced by cisplatin. Mesenchymal stem cells (MSCs) were also selected in addition as a referring agent. Renal fibrosis induced by cisplatin intake significantly increased creatinine, urea, nuclear factor kappa B, insulin-like growth factor-1, fibroblast growth factor-23, and kidney malondialdehyde (MDA) content. Hepatocyte growth factor and renal content of reduced glutathione demonstrated a significant decrease. Histopathological examination of kidney tissues demonstrated marked cellular changes which are correlated with the biochemical results. Oral SPL intake (20 mg/kg/body weight) daily for 4 weeks and MSCs administration (3 × 10⁶ cell/rat) intravenous to the experimental rats resulted in a significant improvement of both the biomarkers studied and the histopathological profile of the renal tissue. Individual administration of spironolactone and MSCs exhibited a marked anti-inflammatory potential and alleviated to a great extent the nephrotoxicity and renal fibrotic pattern induced by cisplatin.

Novel Therapeutics Identification for Fibrosis in Renal Allograft Using Integrative Informatics Approach

Chronic allograft damage, defined by interstitial fibrosis and tubular atrophy (IF/TA), is a leading cause of allograft failure. Few effective therapeutic options are available to prevent the progression of IF/TA. We applied a meta-analysis approach on IF/TA molecular datasets in Gene Expression Omnibus to identify a robust 85-gene signature, which was used for computational drug repurposing analysis. Among the top ranked compounds predicted to be therapeutic for IF/TA were azathioprine, a drug to prevent acute rejection in renal transplantation, and kaempferol and esculetin, two drugs not previously described to have efficacy for IF/TA. We experimentally validated the anti-fibrosis effects of kaempferol and esculetin using renal tubular cells in vitro and in vivo in a mouse Unilateral Ureteric Obstruction (UUO) model. Kaempferol significantly attenuated TGF-β1-mediated profibrotic pathways in vitro and in vivo, while esculetin significantly inhibited Wnt/β-catenin pathway in vitro and in vivo. Histology confirmed significantly abrogated fibrosis by kaempferol and esculetin in vivo. We developed an integrative computational framework to identify kaempferol and esculetin as putatively novel therapies for IF/TA and provided experimental evidence for their therapeutic activities in vitro and in vivo using preclinical models. The findings suggest that both drugs might serve as therapeutic options for IF/TA.

Renal Fibrosis mRNA Classifier: Validation in Experimental Lithium-Induced Interstitial Fibrosis in the Rat Kidney

Accurate diagnosis of fibrosis is of paramount clinical importance. A human fibrosis classifier based on metzincins and related genes (MARGS) was described previously. In this investigation, expression changes of MARGS genes were explored and evaluated to examine whether the MARGS-based algorithm has any diagnostic value in a rat model of lithium nephropathy. Male Wistar rats (n = 12) were divided into 2 groups (n = 6). One group was given a diet containing lithium (40 mmol/kg food for 7 days, followed by 60mmol/kg food for the rest of the experimental period), while a control group (n = 6) was fed a normal diet. After six months, animals were sacrificed and the renal cortex and medulla of both kidneys removed for analysis. Gene expression changes were analysed using 24 GeneChip^® Affymetrix Rat Exon 1.0 ST arrays. Statistically relevant genes (p-value<0.05, fold change>1.5, t-test) were further examined. Matrix metalloproteinase-2 (MMP2), CD44, and nephroblastoma overexpressed gene (NOV) were overexpressed in the medulla and cortex of lithium-fed rats compared to the control group. TGFβ2 was overrepresented in the cortex of lithium-fed animals 1.5-fold, and 1.3-fold in the medulla of the same animals. In Gene Set Enrichment Analysis (GSEA), both the medulla and cortex of lithium-fed animals showed an enrichment of the MARGS, TGFβ network, and extracellular matrix (ECM) gene sets, while the cortex expression signature was enriched in additional fibrosis-related-genes and the medulla was also enriched in immune response pathways. Importantly, the MARGS-based fibrosis classifier was able to classify all samples correctly. Immunohistochemistry and qPCR confirmed the up-regulation of NOV, CD44, and TGFβ2. The MARGS classifier represents a cross-organ and cross-species classifier of fibrotic conditions and may help to design a test to diagnose and to monitor fibrosis. The results also provide evidence for a common pathway in the pathogenesis of fibrosis.

Hyperbranched polyglycerol is superior to glucose for long-term preservation of peritoneal membrane in a rat model of chronic peritoneal dialysis

Background

Replacing glucose with a better biocompatible osmotic agent in peritoneal dialysis (PD) solutions is needed in PD clinic. We previously demonstrated the potential of hyperbranched polyglycerol (HPG) as a replacement for glucose. This study further investigated the long-term effects of chronic exposure to HPG as compared to a glucose-based conventional PD solution on peritoneal membrane (PM) structure and function in rats.

Methods

Adult male Wistar rats received once-daily intraperitoneal injection of 10 mL of HPG solution (1 kDa, HPG 6%) compared to Physioneal™ 40 (PYS, glucose 2.27%) or electrolyte solution (Control) for 3 months. The overall health conditions were determined by blood chemistry analysis. The PM function was determined by ultrafiltration, and its injury by histological and transcriptome-based pathway analyses.

Results

Here, we showed that there was no difference in the blood chemistry between rats receiving the HPG and the Control, while PYS increased serum alkaline phosphatase, globulin and creatinine and decreased serum albumin. Unlike PYS, HPG did not significantly attenuate PM function, which was associated with smaller change in both the structure and the angiogenesis of the PM and less cells expressing vascular endothelial growth factor, α-smooth muscle actin and MAC387 (macrophage marker). The pathway analysis revealed that there were more inflammatory signaling pathways functioning in the PM of PYS group than those of HPG or Control, which included the signaling for cytokine production in both macrophages and T cells, interleukin (IL)-6, IL-10, Toll-like receptors, triggering receptor expressed on myeloid cells 1 and high mobility group box 1.

Conclusions

The results from this experimental study indicate the superiority of HPG to glucose in the preservation of the peritoneum function and structure during the long-term PD treatment, suggesting the potential of HPG as a novel osmotic agent for PD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1098-z) contains supplementary material, which is available to authorized users.

Relationship of clusterin with renal inflammation and fibrosis after the recovery phase of ischemia-reperfusion injury

Background

Long-term outcomes after acute kidney injury (AKI) include incremental loss of function and progression towards chronic kidney disease (CKD); however, the pathogenesis of AKI to CKD remains largely unknown. Clusterin (CLU) is a chaperone-like protein that reduces ischemia-reperfusion injury (IRI) and enhances tissue repair after IRI in the kidney. This study investigated the role of CLU in the transition of IRI to renal fibrosis.

Methods

IRI was induced in the left kidneys of wild type (WT) C57BL/6J (B6) versus CLU knockout (KO) B6 mice by clamping the renal pedicles for 28 min at the body temperature of 32 °C. Tissue damage was examined by histology, infiltrate phenotypes by flow cytometry analysis, and fibrosis-related gene expression by PCR array.

Results

Reduction of kidney weight was induced by IRI, but was not affected by CLU KO. Both WT and KO kidneys had similar function with minimal cellular infiltration and fibrosis at day 14 of reperfusion. After 30 days, KO kidneys had greater loss in function than WT, indicated by the higher levels of both serum creatinine and BUN in KO mice, and exhibited more cellular infiltration (CD8 cells and macrophages), more tubular damage and more severe tissue fibrosis (glomerulopathy, interstitial fibrosis and vascular fibrosis). PCR array showed the association of CLU deficiency with up-regulation of CCL12, Col3a1, MMP9 and TIMP1 and down-regulation of EGF in these kidneys.

Conclusion

Our data suggest that CLU deficiency worsens renal inflammation and tissue fibrosis after IRI in the kidney, which may be mediated through multiple pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-016-0348-x) contains supplementary material, which is available to authorized users.

Senescence in chronic allograft nephropathy

Despite increasing numbers of patients on dialysis, the numbers of renal transplants performed yearly have remained relatively static. During the last 50 years, there have been many advances in the pharmacology of prevention of organ rejection. However, most patients will suffer from a slow but steady decline in renal function leading to graft loss. The most common cause of long-term graft loss is chronic allograft nephropathy (CAN). Therefore, elucidating and understanding the mechanisms involved in CAN is crucial for achieving better posttransplant outcomes. It is thought that the development of epithelial to mesenchymal transition (EMT) in proximal tubules is one of the first steps towards CAN, and has been shown to be a result of cellular senescence. Cells undergoing senescence acquire a senescence associated secretory phenotype (SASP) leading to the production of interleukin-1 alpha (IL-1α), which has been implicated in several degenerative and inflammatory processes including renal disease. A central mediator in SASP activation is the production of reactive oxygen species (ROS), which are produced in response to numerous physiological and pathological stimuli. This review explores the connection between SASP and the development of EMT/CAN in an effort to suggest future directions for research leading to improved long-term graft outcomes.

Stop chronic kidney disease progression: Time is approaching

Progression of chronic kidney disease (CKD) is inevitable. However, the last decade has witnessed tremendous achievements in this field. Today we are optimistic; the dream of withholding this progression is about to be realistic. The recent discoveries in the field of CKD management involved most of the individual diseases leading the patients to end-stage renal disease. Most of these advances involved patients suffering diabetic kidney disease, chronic glomerulonephritis, polycystic kidney disease, renal amyloidosis and chronic tubulointerstitial disease. The chronic systemic inflammatory status and increased oxidative stress were also investigated. This inflammatory status influences the anti-senescence Klotho gene expression. The role of Klotho in CKD progression together with its therapeutic value are explored. The role of gut as a major source of inflammation, the pathogenesis of intestinal mucosal barrier damage, the role of intestinal alkaline phosphatase and the dietary and therapeutic implications add a novel therapeutic tool to delay CKD progression.

Increased gene expression of TGF-β in peripheral blood mononuclear cells from renal transplant patients with polyomavirus BK viremia

We aimed to investigate the roles of cytokines during polyomavirus BK (BKV) reactivation in renal transplant patients. Forty-eight renal allograft recipients were enrolled, and their sera BKV viral load and mRNA expression levels of cytokines in peripheral blood mononuclear cells were measured by real-time polymerase chain reaction. Patient's age and gene expression levels of interleukin (IL)-2 (10.04 ± 2.63 vs. 8.70 ± 2.40, p = 0.049) and transforming growth factor (TGF)-β (12.58 ± 2.59 vs. 10.89 ± 1.91, p = 0.015) were significantly higher in BKV viremia (+) renal transplant patients. Multivariate logistic regression analysis revealed that age and mRNA expression levels of TGF-β, but not IL-2, significantly correlated with the presence of BKV viremia. Sera BKV viral loads showed a positive correlation with patient age and the levels of TGF-β and IL-6 mRNA. After adjusting for age and sex in the regression model, both age and TGF-β mRNA levels maintained a significant positive association with sera BKV viral loads. Serum TGF-β concentration tended to be higher in BKV viremia (+) patients (p = 0.079). In conclusion, expression levels of TGF-β were found to correlate with both BKV viremia positivity and sera BKV viral loads in renal transplant patients.

Lefty-1 alleviates TGF-β1-induced fibroblast-myofibroblast transdifferentiation in NRK-49F cells

Fibroblast activation and proliferation are important for fibroblast–myofibroblast transdifferentiation, a crucial process in the pathological changes that define renal interstitial fibrosis. The left–right determination factor (Lefty) is an important cytokine of the transforming growth factor (TGF)-β family, with two variants, Lefty-1 and Lefty-2, in mice. Lefty has diverse functions, such as the regulation of embryonic development, the inhibition of TGF-β1 signaling, and the suppression of tumor activity. However, whether Lefty-1 influences fibroblast activation and proliferation, and consequently prevents fibroblast–myofibroblast transdifferentiation, remains unclear. This study aimed to investigate whether Lefty-1 can attenuate TGF-β1-induced fibroblast–myofibroblast transdifferentiation in normal rat kidney interstitial fibroblast cells (NRK-49F), as well as the mechanisms underlying any effects. Results showed that the typical fibroblast cell morphology of NRK-49F cells was altered after TGF-β1 treatment and that Lefty-1 significantly prevented this change in a dose-dependent manner. Further analyses demonstrated decreased proliferating cell nuclear antigen, cyclin D1, collagen I(A1), alpha-smooth muscle actin, and fibronectin expression. Lefty-1 further induced remarkable reductions in TGF-β1-induced Smad3 and mitogen-activated protein kinase-10/c-Jun N-terminal kinase (JNK-3) signaling, and enhanced expression of the antifibrotic factor bone morphogenetic protein (BMP)-5. However, without TGF-β1, Lefty-1 had no effect on Smad3, JNK-3, and BMP-5 activation and fibroblast–myofibroblast transdifferentiation. Taken together, these findings indicate that Lefty-1 can alleviate TGF-β1-mediated activation and the proliferation of fibroblasts. Furthermore, Lefty-1 may prevent fibroblast–myofibroblast transdifferentiation in part via modulations of Smad3, JNK-3, and BMP-5 activities in the TGF-β/BMP signaling pathway.

Obesity and kidney disease: differential effects of obesity on adipose tissue and kidney inflammation and fibrosis

PURPOSE OF REVIEW

To provide a perspective by investigating the potential cross-talk between the adipose tissue and the kidney during obesity.

RECENT FINDINGS

It is well established that excessive caloric intake contributes to organ injury. The associated increased adiposity initiates a cascade of cellular events that leads to progressive obesity-associated diseases such as kidney disease. Recent evidence has indicated that adipose tissue produces bioactive substances that contribute to obesity-related kidney disease, altering the renal function and structure. In parallel, proinflammatory processes within the adipose tissue can also lead to pathophysiological changes in the kidney during the obese state.

SUMMARY

Despite considerable efforts to better characterize the pathophysiology of obesity-related metabolic disease, there are still a lack of efficient therapeutic strategies. New strategies focused on regulating adipose function with respect to AMP-activated protein kinase activation, NADPH oxidase function, and TGF-β may contribute to reducing adipose inflammation that may also provide renoprotection.

siRNA technology in kidney transplantation: current status and future potential

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

Renal allograft fibrosis: biology and therapeutic targets

Renal tubulointerstitial fibrosis is the final common pathway of progressive renal diseases. In allografts, it is assessed with tubular atrophy as interstitial fibrosis/tubular atrophy (IF/TA). IF/TA occurs in about 40% of kidney allografts at 3-6 months after transplantation, increasing to 65% at 2 years. The origin of renal fibrosis in the allograft is complex and includes donor-related factors, in particular in case of expanded criteria donors, ischemia-reperfusion injury, immune-mediated damage, recurrence of underlying diseases, hypertensive damage, nephrotoxicity of immunosuppressants, recurrent graft infections, postrenal obstruction, etc. Based largely on studies in the non-transplant setting, there is a large body of literature on the role of different cell types, be it intrinsic to the kidney or bone marrow derived, in mediating renal fibrosis, and the number of mediator systems contributing to fibrotic changes is growing steadily. Here we review the most important cellular processes and mediators involved in the progress of renal fibrosis, with a focus on the allograft situation, and discuss some of the challenges in translating experimental insights into clinical trials, in particular fibrosis biomarkers or imaging modalities.

New strategies and concepts in organ preservation

Organ transplantation is still affected by a notable degree of preservation-associated ischemia and reperfusion injury, which can seriously hamper early graft function. The increasing extension of the criteria for donor organ acceptance, especially for organs that have suffered from periods of warm ischemic injury prior to graft retrieval, results in even higher demands on preserving these ischemia-sensitive grafts. Growing attention is thus directed towards more dynamic preservation methods instead of simple static storage. Particularly in grafts that are retrieved after cardiac standstill of the donor, provision of oxygen to enable some kind of regenerative metabolism appears to be desirable, although the optimal temperature for oxygenated preservation/revitalization is still under debate. Hybrid solutions, comprising conventional cold storage for ease of graft procurement and transportation together with more sophisticated 'in-house' reconditioning protocols after arrival at the implantation clinic, might help to minimize graft injury during the critical transition from preservation to reperfusion.

Recent advances in renal interstitial fibrosis and tubular atrophy after kidney transplantation

Although kidney transplantation has been an important means for the treatment of patients with end stage of renal disease, the long-term survival rate of the renal allograft remains a challenge. The cause of late renal allograft loss, once known as chronic allograft nephropathy, has been renamed “interstitial fibrosis and tubular atrophy” (IF/TA) to reflect the histologic pattern seen on biopsy. The mechanisms leading to IF/TA in the transplanted kidney include inflammation, activation of renal fibroblasts, and deposition of extracellular matrix proteins. Identifying the mediators and factors that trigger IF/TA may be useful in early diagnosis and development of novel therapeutic strategies for improving long-term renal allograft survival and patient outcomes. In this review, we highlight the recent advances in our understanding of IF/TA from three aspects: pathogenesis, diagnosis, and treatment.

Allograft rejection and tubulointerstitial fibrosis in human kidney allografts: interrogation by urinary cell mRNA profiling

Because the kidney allograft has the potential to function as an in-vivo flow cytometer and facilitate the access of immune cells and kidney parenchymal cells in to the urinary space, we hypothesized that mRNA profiling of urinary cells offers a noninvasive means of assessing the kidney allograft status. We overcame the inherent challenges of urinary cell mRNA profiling by developing pre-amplification protocols to compensate for low RNA yield from urinary cells and by developing robust protocols for absolute quantification mRNAs using RT-PCR assays. Armed with these tools, we undertook first single-center studies urinary cell mRNA profiling and then embarked on the multicenter Clinical Trials in Organ Transplantation-04 study of kidney transplant recipients. We report here our discovery and validation of diagnostic and prognostic biomarkers of acute cellular rejection and of interstitial fibrosis and tubular atrophy (IF/TA). Our urinary cell mRNA profiling studies, in addition to demonstrating the feasibility of accurate diagnosis of acute cellular rejection and IF/TA in the kidney allograft, advance mechanistic and potentially targetable biomarkers. Interventional trials, guided by urinary cell mRNA profiles, may lead to personalized immunosuppression in recipients of kidney allografts.

Antiproteinuric effect of pirfenidone in a rat model of anti-glomerular basement membrane glomerulonephritis

While pirfenidone has been established as an effective anti-fibrosis remedy, whether or not its antifibrotic effect contributes to a reduction of proteinuria remains unclear. We investigated the renoprotective properties of pirfenidone in an anti-glomerular basement membrane (GBM) glomerulonephritis model both prophylactically and therapeutically to determine its profile against proteinuria. In the prophylactic regimen, pirfenidone was treated immediately after anti-serum injection. We observed a significant reduction in the progression of proteinuria (P<0.05) and decline in renal function (P<0.01) and also noted histological improvement in renal injury. These effects appeared to be due to the maintained expression of nephrin and podocin on podocytes as well as the reduced expression of profibrotic factors like transforming growth factor-β (TGF-β). The expression of nephrin mRNA was strongly negatively correlated with the amount of urinary protein excretion (R=-0.84, P<0.001), implicating podocyte damage in the outcome of proteinuria (R(2)=0.70). These results suggest that preservation of podocytes with the pirfenidone treatment may have resulted in the decrease of proteinuria. In contrast, when the therapeutic regimen was initiated 2 weeks after nephritis induction, pirfenidone had little effect on the progression of proteinuria, although the decline of renal function and fibrosis were suppressed. Taken together, present findings suggested that pirfenidone prevented the progression of proteinuria only when administered prophylactically but was still able to ameliorate the decline of renal function independent of proteinuria. In conclusion, pirfenidone as a prophylactic regimen reduces proteinuria in anti-GBM nephritis via preservation of podocytes with markedly reduced efficacy when administered as a therapeutic regimen.

Novel targets of antifibrotic and anti-inflammatory treatment in CKD

Chronic kidney disease (CKD) is becoming a worldwide epidemic, driven largely by the dramatic rise in the prevalence of diabetes and obesity. Novel targets and treatments for CKD are, therefore, desperately needed-to both mitigate the burden of this disease in the general population and reduce the necessity for renal replacement therapy in individual patients. This Review highlights new insights into the mechanisms that contribute to CKD, and approaches that might facilitate the development of disease-arresting therapies for CKD. Particular focus is given to therapeutic approaches using antifibrotic agents that target the transforming growth factor β superfamily. In addition, we discuss new insights regarding the roles of vascular calcification, the NADPH oxidase family, and inflammation in the pathogenesis of CKD. We also highlight a new understanding regarding kidney energy sensing pathways (AMPK, sirtuins, and mTOR) in a variety of kidney diseases and how they are linked to inflammation and fibrosis. Finally, exciting new insights have been made into the role of mitochondrial function and mitochondrial biogenesis in relation to progressive kidney disease. Prospective therapeutics based on these findings will hopefully renew hope for clinicians and patients in the near future.