Nephron Experimental Nephrology最新文献

Background/aims: Renal artery stenosis (RAS), which may lead to renal fibrosis, is a common cause of end-stage renal disease in elderly patients. However, the potential mechanisms leading to the development of renal fibrosis and atrophy have not been clarified.

Methods: A two-kidney, one-clip Goldblatt mouse model was established in the present study. Blood pressure, morphological and pathological alterations were examined on days 7, 14, and 28 after surgery. Peritubular capillary loss and pericyte changes after injury were evaluated. Inflammatory macrophage infiltration and Wnt/β-catenin signaling were also investigated.

Results: A significant increase in blood pressure and obvious renal atrophy were observed on days 7, 14, and 28 after surgery. Following surgery, the clipped kidneys developed aggravated interstitial fibrosis and tubular epithelial injury over time. Moreover, RAS induced obvious peritubular capillary loss and inflammatory macrophage infiltration. Increased pericyte number was found in the clipped kidneys, but these cells detached from the endothelial cells and migrated to the interstitium. Wnt/β-catenin signaling was also significantly upregulated in the clipped kidneys after surgery.

Conclusion: Our study provides a novel insight into the mechanisms linking peritubular capillary loss and pericyte changes in RAS-induced renal fibrosis. Our findings also suggest that inflammatory macrophages and Wnt/β-catenin signaling participate in these pathological processes. Therefore, multi-target therapeutic strategies may significantly contribute to the prevention of renal interstitial fibrosis and the preservation of renal function in patients with RAS.

Background: Acute kidney injury (AKI) is emerging as a public health problem in developing and developed countries. It affects up to 7% of hospitalized patients, with a higher prevalence in critical care units. Despite major advances in preventive strategies and support measures, the mortality rate among patients remains higher than 50%. Several pharmacological approaches to improve renal function and survival after an AKI episode have been largely unsuccessful in clinical practice.

Summary: Stem cell-based therapy has provided new hopes of innovative interventions to enhance the limited capability of kidney regeneration in AKI. An important target for cell therapy is represented by tubular epithelial cells which after acute ischemic or toxic insults undergo dysfunction and detachment. Among adult stem cells, mesenchymal stromal/stem cells (MSC) are an attractive therapeutic tool by virtue of their unique biological properties, tropism for damaged tissues, and proregenerative capacity. In the present review, we discuss the mechanisms underlying the renoprotective effects of therapies with stem cells of different origins in preclinical models of AKI by evaluating new modalities by which MSC interact with damaged cells via the release of soluble factors and exosomes/microvesicles. Several biological effects, including antiapoptotic, promitogenic, immunomodulatory, and anti-inflammatory activities, have been analyzed in renal tissue of AKI animals receiving stem cell treatments. The mechanisms of stem cell homing and engraftment to sites of tissue damage have also been discussed.

Key messages: The translation of preclinical data on stem cells into effective and safe new modalities of care is still limited, and further studies are needed before their application in patients with AKI.

Background: Various cell types, including podocytes and parietal epithelial cells, play important roles in the development and progression of glomerular kidney diseases, albuminuria, and glomerulosclerosis. Besides their role in renal pathologies, glomerular cells have emerging new functions in endogenous repair mechanisms. A better understanding of the dynamics of the glomerular environment and cellular composition in an intact living kidney is critically important for the development of new regenerative therapeutic strategies for kidney diseases. However, progress in this field has been hampered by the lack of in vivo research tools.

Summary: This review summarizes the current state-of-the-art in the application of the unique intravital imaging technology of multiphoton fluorescence microscopy for the dynamic visualization of glomerular structure and function over time in the intact, living kidney. Recently, this imaging approach in combination with transgenic mouse models allowed tracking of the fate of individual glomerular cells in vivo over several days and depicted the highly dynamic nature of the glomerular environment, particularly in disease conditions.

Key messages: The technology is ready and available for future intravital imaging studies investigating new glomerular regenerative approaches in animal models.

Background: Since no specific or radical treatments have yet been established for acute kidney injury (AKI), the development of cell transplantation therapy using renal progenitors is desirable as a new therapeutic option for AKI. The recent advances in developmental biology, stem cell biology, and nephrology have led to an increased availability of renal progenitors from multiple sources.

Summary: Four main sources of renal progenitors have been described so far: isolation from (1) embryonic or (2) adult kidneys, (3) directed differentiation of pluripotent stem cells such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), and (4) cellular reprogramming of fully differentiated adult renal cells. Renal progenitors from adult kidneys may not be equivalent to those from embryonic kidneys, and they contain several different cell populations identified by various methods. The methods used for the directed differentiation of ESCs/iPSCs and reprogramming of differentiated adult renal cells into renal progenitors have not been fully established. The therapeutic effects of progenitor cell transplantation in AKI animal models have been examined in a small number of reports using renal progenitors from adult kidneys, while no reports have described the therapeutic potential of renal progenitors from other sources.

Key messages: Renal progenitor transplantation might provide a novel therapeutic strategy for AKI. Further research efforts toward the clinical application of this strategy are needed, including a detailed characterization of embryonic or adult renal progenitors and the development of in vitro expansion methods and therapeutically effective transplantation methods for these cell types. More experience and knowledge should be accumulated regarding the directed differentiation of pluripotent stem cells and cellular reprogramming to generate renal progenitor cells.

Background: Leflunomide (LEF) and benazepril have renoprotective effects on diabetic nephropathy (DN) through their anti-inflammatory and anti-fibrotic activities. This study investigated whether combined treatment using LEF and benazepril affords superior protection compared with the respective monotherapies.

Methods: Diabetes was induced with streptozotocin (STZ, 65 mg/kg) by intraperitoneal injection in male Wistar rats. Two weeks after STZ injection, diabetic rats were treated daily for 12 weeks with LEF (10 mg/kg), benazepril (10 mg/kg), or a combination of both. Basic parameters (body weight, fasting blood glucose level, and 24 h urinary protein excretion), histopathology, inflammatory [inflammatory cell infiltration (ED-1), monocyte chemoattractant protein-1 (MCP-1), and Toll-like receptor-2 (TLR-2)] and glomerulosclerotic factors [transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF)], and oxidative stress (8-hydroxy-2'-deoxyguanosine, 8-OHdG) were studied.

Results: Benazepril or LEF treatment significantly prevented body weight loss and 24 h urinary protein excretion induced by diabetes; combined treatment with LEF and benazepril further improved these parameters compared with giving each drug alone (all p < 0.01). Increased expression of inflammatory (MCP-1 and TLR-2) and glomerulosclerotic (TGF-β1 and CTGF) factors in diabetic rat kidney was reduced by treatment with either LEF or benazepril and was further reduced by the combined administration of the two drugs (p < 0.01). These effects were accompanied by suppression of urinary 8-OHdG excretion. There was no significant between-group difference in blood glucose level.

Conclusions: LEF treatment lessens DN, and combined treatment with LEF and benazepril provides synergistic effects in preventing DN.

Background/aims: Continuous exposure of the peritoneal membrane to high-glucose (HG) peritoneal dialysis fluids (PDFs) can produce peritoneal mesothelial cells (PMCs) injury. It has been demonstrated that hydrogen sulfide (H2S), the third endogenous gaseous mediator identified after nitric oxide and carbon monoxide, exhibits a potent protective effect on cell activity. We studied the toxic effects of HG PDFs and their reversal by H2S on cultures of rat PMCs.

Methods: Synchronized confluent rat PMCs were incubated with 2.5% glucose PDFs with or without NaHS, an H2S donor. Cell viability was assessed by methyl thiazolyl tetrazolium assay and flow cytometry. The level of phospho-p38 mitogen-activated protein kinase (MAPK) was analyzed by immunoblotting. p53, Bax and Bcl-2 mRNA expressions by rat PMCs were detected by real-time PCR. The levels of reactive oxygen species (ROS), superoxide dismutase (SOD) activity and caspase-3 activity were measured.

Results: Exposure of rat PMCs to 2.5% glucose PDFs for 24 h resulted in a significant induction of apoptosis, which was attenuated by NaHS. NaHS also restored the 2.5% glucose PDF-induced increase in phospho-p38 MAPK (indices of cellular toxicity). Further investigation of the apoptotic mechanisms in rat PMCs demonstrated that HG activated caspase-3 and upregulated Bax, while it downregulated Bcl-2. All the above responses were prevented by pretreatment with NaHS. Moreover, NaHS reversed the 2.5% glucose PDF-induced increase in ROS generation and decrease in SOD activity.

Conclusions: These findings suggest that HG PDFs significantly inhibit rat PMC viability, leading to peritoneal injury. H2S exhibits a potent anti-apoptotic ability by attenuating oxidative stress and inhibiting caspase-3 activation, which in turn restores peritoneal injury.

Aims: We aimed to determine the impact of aging on ischemic acute kidney injury, especially in terms of the pathological mechanisms of kidney and heart crosstalk.

Method: The effects of 45 min of unilateral ischemic reperfusion (IR) of the renal artery on the contralateral kidney and heart were histologically assessed in 7- and 40-week-old SD rats after 7 days.

Results: Glomerular sclerosis, interstitial fibrosis and numbers of ED1 cells were significantly increased in the contralateral kidneys of the 40-, but not the 7-week-old rats. The numbers of ED1 cells in the heart significantly and similarly increased in both groups, but reactive fibrosis after IR was significant only in the 40-week-old rats. The exaggerated profibrotic response induced by aging seemed to be closely associated with the increased number of ED1 cells in the affected area.

Conclusion: Aging could play a major role in exaggerating the pathological processes of inflammation to fibrosis in remote organs including the heart and the nonischemic kidney after IR stimulation of the unilateral kidney.

Background and aims: Murine bone marrow (BM) dendritic cells (DCs) can be modulated to be tolerogenic by cytokines, such as interleukin (IL)-10 and transforming growth factor (TGF)-β, and may play a regulatory role and sustain immune hemostasis in cognate kidney disease. However, it is unknown whether BM-DCs can be used to protect against renal injury in murine Adriamycin nephropathy (AN).

Methods: In this study, by adoptive in vivo transfer of BM-DCs, including immature DCs, mature DCs (lipopolysaccharide-stimulated DCs) and BM regulatory DCs (IL-10/TGF-β-modified DCs, DCregs), we addressed the potential benefits of BM-DCs in chronic kidney disease.

Results: We found that after adoptive transfer of DCregs, renal injury, including glomerulosclerosis, interstitial fibrosis and tubular atrophy, was not changed compared to AN controls. Correspondingly, renal functions measured by serum creatinine, 12-hour urine protein and creatinine clearance were also not improved by transfusion with DCregs compared to AN controls.

Conclusion: This study showed that the adoptive transfer of BM-DCs was unable to improve renal injury in an AN model, and this failure related to their inability to access the kidney.

Background: Renal tubular cell apoptosis is a key mechanism of contrast-induced acute kidney injury. It has been reported that endoplasmic reticulum (ER) stress is the underlying mechanism of high osmolar contrast-induced renal tubular cell apoptosis. Whether ER stress is involved in low osmolar contrast-induced renal tubular cell injury remains unclear. In the present study, the roles of ER stress in iopromide-induced (a low osmolar contrast) renal tubular cell apoptosis and the effects of N-acetylcysteine (NAC) on ER stress were investigated.

Methods: NRK-52E cells were exposed to different concentrations of iopromide [50, 100 and 150 mg iodine (I)/ml] for 4 h. In a separate experiment, NRK-52E cells were exposed to iopromide (100 mg I/ml, 4 h) with or without NAC (10 mmol/l). NAC was added 1 h before incubation with iopromide. Apoptosis was determined by Hoechst staining and flow cytometry. The intracellular formation of reactive oxygen species (ROS) was detected by confocal microscopy with fluorescent probe CM-H2DCFDA. The expression of glucose-regulated protein 78 (GRP78) and CAAT/enhancer-binding protein homologous protein (CHOP) was determined by Western blot.

Results: Iopromide induced NRK-52E cell apoptosis in a concentration-dependent manner. The intracellular ROS production increased significantly following iopromide exposure in the NRK-52E cells. Significantly increased expressions of GRP78 and CHOP were observed in the NRK-52E cells exposed to iopromide for 4 h; NAC attenuated iopromide-induced NRK-52E cell apoptosis by inhibiting the overproduction of intracellular ROS and subsequently suppressing the overexpression of GRP78 and CHOP.

Conclusion: ROS-mediated ER stress is involved in contrast-induced renal tubular cell apoptosis.

Background: Lipoprotein abnormalities are associated with a rapid decline in renal function in patients of chronic kidney disease. In addition, hyperlipidemia is associated with an increased risk of developing renal insufficiency. The underlying molecular mechanisms for these clinical findings are unclear. We have previously reported a role for inhibitor of differentiation 3 (ID3), a transcription factor, in regulating kidney disease in hyperlipidemia. Introducing a genetic deficiency of Id3 in spontaneously hyperlipidemic apolipoprotein E knockout (Apoe(-/-)) mice led to accelerated mesangioproliferative glomerulonephritis. The present study was carried out to further investigate the contribution of ID3 in hyperlipidemia-associated kidney disease.

Methods: Female C57BL/6 mice that were ID3-sufficient wild-type (WT) or ID3-deficient (Id3(-/-)) were fed a Western diet and evaluated for proteinuria, glomerular pathology, and immune infiltrating cells. Primary mesangial cell lines were generated from both mouse strains and stimulated with oxidized phospholipids. Cytokines and chemokines produced were measured by multiplex assays, ELISA, and QPCR. Glomerular isolates were studied for CXCL1 expression by QPCR.

Results: Id3(-/-) mice on a Western diet developed accelerated proteinuria and mesangioproliferative glomerulonephritis compared to WT controls. In vitro, Id3(-/-) glomerular mesangial cell lines produced higher levels of the monocyte chemoattractant CXCL1 in response to oxidized phospholipids. This was consistent with the rapid increase in glomerular CXCL1 expression followed by macrophage infiltration in Id3(-/-) mice fed a Western diet.

Conclusions: A functional ID3 influences susceptibility to kidney disease and prevents glomerular injury by regulating local chemokine production and inflammatory cell recruitment.