CD59 protects glomerular endothelial cells from immune-mediated thrombotic microangiopathy in rats

Antiphospholipid syndrome nephropathy: Current knowledge and unanswered questions

The definition of acute and chronic antiphospholipid syndrome (APS) nephropathy was recently updated using a multiphase methodology in the context of the development of the new APS classification criteria. Currently, there is no consensus for the treatment of APS nephropathy, which mainly relies on the general recommendations for the management of APS. Based on evidence from experimental studies and a few clinical studies and case series, targeted treatments such as B-cell depletion, anti-B-cell activating factor antibody, complement inhibition, mammalian target of rapamycin inhibition, and neutrophil extracellular traps or interferon targeting may show promise for the treatment of microvascular manifestations in APS, including APS nephropathy. Validation of the new APS nephropathy definition and/or efforts for improvement in proposed terminology, along with the assessment of the safety and efficacy of potential targeted treatments in randomized controlled trials, are major future research directions. In this review, we summarize the current knowledge of APS nephropathy and discuss unanswered questions.

Atypical hemolytic uremic syndrome: when pregnancy leads to lifelong dialysis: a case report and literature review

Atypical hemolytic uremic syndrome (aHUS), a challenging disorder, commonly caused by inherited defects or regulatory processes of the complement alternative pathway. There are multiple causes, including pregnancy. Pregnancy provokes life-threatening episodes, preeclampsia, hemolysis elevated liver enzymes low platelets, microangiopathic hemolytic anemia (MAHA) and end-stage renal disease. Additionally, complement dysregulation and, with aHUS, affects fetal and maternal outcomes. Pregnancy-associated aHUS results in a poor prognosis with irreversible renal damage. Likewise, it is imperative to know that MAHA can provoke endothelial disruption, destruction of red cells and thrombocytopenia. We present a case of a young 18-year-old woman with MAHA and aHUS, requiring emergent cesarean section at 34 weeks of gestation and hemodialysis, secondary to complications from a recent pregnancy. Elevated blood pressure readings, rising creatinine levels, as well as her mother being on dialysis after pregnancy raised suspicion for thrombotic microangiopathy and aHUS. She was subsequently managed with plasma exchange, steroids, eculizumab and hemodialysis. Thus, plasma exchange should be initiated, with pending additional workup. Upon a definitive diagnosis of aHUS, eculizumab would be warranted to mitigate immune dysregulation. Understanding thrombotic microangiopathies diagnosis, and recognizing concomitant consequences, is vital. Having better insights into endothelial injuries can prevent unfortunate outcomes.

Successful Treatment of Catastrophic Antiphospholipid Syndrome Using Rituximab: Case Report and Review of the Literature

BACKGROUND

Kidney involvement is a frequent complication of systemic lupus erythematosus (SLE) and kidney biopsy is essential in differentiating lupus nephritis (LN) from thrombotic microangiopathy (TMA) secondary to antiphospholipid autoantibodies (aPL). Association between antiphospholipid syndrome (APS) and acquired hemophilia due to inhibitors was very rarely described in SLE patients.

CASE PRESENTATION

We present the case of a 61-year-old male diagnosed with SLE who acquired deficiency of clotting factor VIII due to circulating inhibitors, admitted for acute kidney injury (AKI), microangiopathic hemolytic anemia, thrombocytopenia, and diplopia. Kidney biopsy showed TMA due to APS, but no signs of LN. Head computed tomography identified low dense areas in the white matter, suggesting small blood vessels' involvement. A diagnosis of probable catastrophic antiphospholipid syndrome (CAPS) was established and treatment with low molecular weight heparin, intravenous methylprednisolone, plasmapheresis, and rituximab was initiated, followed by resolution of AKI, diplopia, and TMA with complete depletion of CD19+B-lymphocytes (CD19+B-Ly) after one month. We further review the current knowledge regarding pathogenesis and management of CAPS in SLE patients.

CONCLUSIONS

Targeted therapy was possible after kidney biopsy, improving renal and general prognosis. CD19+B-Ly repopulation preceded biological relapse, so monitoring of CD19+B-Ly may serve as a tool to predict relapses and guide rituximab therapy.

Informatics Analysis of Health Indicators and Pathological Manifestations of Foot-Process in Patients with Primary IgA Nephropathy

Objective: This paper focuses on the foot-process in renal biopsies of patients with lgA, and examines their correlation with baseline clinical indicators and pathological manifestations in patients with lgA. Method: A retrospective data of patients who performed renal biopsy proven IgA nephropathy was selected. The patients who reached the agreed standard were grouped based on the degree of foot-process. There were three groups (ABC Groups) (Du, Y. and Huang, C, 2009. The value of proteinuria and foot process fusion in the onset of prognosis of acute kidney disease. Chinese Journal of Integrated Traditional and Western Medicine, 10(1), pp.44-45): group A for patients with no obvious foot-process lesion; group B for patients with segmental foot-process; group C for patients with massive foot-process. The three groups were reviewed in the aspects of baseline clinical indicators and Oxford classification, so as to discover foot-process’ effect on patients with IgA nephropathy. Results: A total of 129 patients with IgA nephropathy were included in the study. Concerning about the clinical baseline indicators related to the degree of foot-process, the 24-hour proteinuria level at admission was statistically significant and positively correlated (r = 0.324, P = 0.000). The comparison between groups showed there was statistically significant difference between group C and group A and group B (P = 0.001, P = 0.035). According to the Oxford Classification, only the differences of mesangial hypercellularity (M) and segmental sclerosis/adhesion (S) were statistically significant (r = 0.239, P = 0.006; r = 0.257, P = 0.003) and were positively correlated. In terms of mesangial hypercellularity (M), the differences between group A and B, group A and C were statistically significant (P = 0.01, P = 0.003). The comparison between group B and group C showed statistical difference (P = −0.031) in segmental sclerosis/adhesion (S). Among the 76 patients with S0 revealed by the Oxford classification, there were 55 patients of glomerulosclerosis, which was positively correlated with the degree of foot process (r = 0.211, P = 0.016). The comparison between group A and group C showed statistical difference (P = 0.014). Conclusion: The severity foot-process was positively correlated with the level of proteinuria. Foot-process is positively related with mesangial hypercellularity, segmental sclerosis and glomerulosclerosis. With more severe the foot-process, there will be more serious mesangial hypercellularity and irreversible glomerular injury. Foot-process is positively correlated with Lee’s Pathological Grading.

Percutaneous transluminal renal angioplasty attenuates poststenotic kidney mitochondrial damage in pigs with renal artery stenosis and metabolic syndrome

Percutaneous transluminal renal angioplasty (PTRA) has been used to treat renovascular disease (RVD), a chronic condition characterized by renal ischemia and metabolic abnormalities. Mitochondrial injury has been implicated as a central pathogenic mechanism in RVD, but whether it can be reversed by PTRA remains uncertain. We hypothesized that PTRA attenuates mitochondrial damage, renal injury, and dysfunction in pigs with coexisting renal artery stenosis (RAS) and metabolic syndrome (MetS). Four groups of pigs (n = 6 each) were studied after 16 weeks of diet-induced MetS and RAS (MetS + RAS), MetS + RAS treated 4 weeks earlier with PTRA, and Lean and MetS Sham controls. Single-kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multidetector computed tomography, and renal tubular mitochondrial structure and function and renal injury ex vivo. PTRA successfully restored renal artery patency, but mean arterial pressure remained unchanged. Stenotic kidney RBF and GFR, which fell in MetS + RAS compared to MetS, rose after PTRA. PTRA attenuated MetS + RAS-induced mitochondrial structural abnormalities in tubular cells and peritubular capillary endothelial cells, decreased mitochondrial H2 02 production, and increased renal cytochrome-c oxidase-IV activity and ATP production. PTRA also improved cortical microvascular and peritubular capillary density and ameliorated tubular injury and tubulointerstitial fibrosis in the poststenotic kidney. Importantly, renal mitochondrial damage correlated with poststenotic injury and dysfunction. Renal revascularization attenuated mitochondrial injury and improved renal hemodynamics and function in swine poststenotic kidneys. This study suggests a novel mechanism by which PTRA might be relatively effective in ameliorating mitochondrial damage and improving renal function in coexisting MetS and RAS.

Mesenchymal Stem/Stromal Cell-Derived Extracellular Vesicles Elicit Better Preservation of the Intra-Renal Microvasculature Than Renal Revascularization in Pigs with Renovascular Disease

Background: Percutaneous transluminal renal angioplasty (PTRA) confers clinical and mortality benefits in select ‘high-risk’ patients with renovascular disease (RVD). Intra-renal-delivered extracellular vesicles (EVs) released from mesenchymal stem/stromal cells (MSCs) protect the kidney in experimental RVD, but have not been compared side-by-side to clinically applied interventions, such as PTRA. We hypothesized that MSC-derived EVs can comparably protect the post-stenotic kidney via direct tissue effects. Methods: Five groups of pigs (n = 6 each) were studied after 16 weeks of RVD, RVD treated 4 weeks earlier with either PTRA or MSC-derived EVs, and normal controls. Single-kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multi-detector CT, and renal microvascular architecture (3D micro CT) and injury pathways ex vivo. Results: Despite sustained hypertension, EVs conferred greater improvement of intra-renal microvascular and peritubular capillary density compared to PTRA, associated with attenuation of renal inflammation, oxidative stress, and tubulo-interstitial fibrosis. Nevertheless, stenotic kidney RBF and GFR similarly rose in both PTRA- and EV-treated pigs compared RVD + Sham. mRNA sequencing reveled that EVs were enriched with pro-angiogenic, anti-inflammatory, and antioxidants genes. Conclusion: MSC-derived EVs elicit a better preservation of the stenotic kidney microvasculature and greater attenuation of renal injury and fibrosis compared to PTRA, possibly partly attributed to their cargo of vasculo-protective genes. Yet, both strategies similarly improve renal hemodynamics and function. These observations shed light on diverse mechanisms implicated in improvement of post-stenotic kidney function and position EVs as a promising therapeutic intervention in RVD.

Systemic lupus erythematosus multiorgan flare with quiescent serologic markers

Systemic lupus erythematosus (SLE) can affect almost every organ with differing degrees of severity. Typically, SLE activity is associated with hypocomplimentaemia and elevated double-stranded DNA (dsDNA) levels. We describe a case of a severe multiorgan lupus flare including lupus cerebritis, autoimmune haemolytic anaemia, lupus nephritis and lupus myopericarditis with normal complement and dsDNA levels. This highlights the importance of understanding the heterogeneous nature of SLE flares.

Complement as a Therapeutic Target in Systemic Autoimmune Diseases

The complement system (CS) includes more than 50 proteins and its main function is to recognize and protect against foreign or damaged molecular components. Other homeostatic functions of CS are the elimination of apoptotic debris, neurological development, and the control of adaptive immune responses. Pathological activation plays prominent roles in the pathogenesis of most autoimmune diseases such as systemic lupus erythematosus, antiphospholipid syndrome, rheumatoid arthritis, dermatomyositis, and ANCA-associated vasculitis. In this review, we will review the main rheumatologic autoimmune processes in which complement plays a pathogenic role and its potential relevance as a therapeutic target.

MiR-185-5p ameliorates endoplasmic reticulum stress and renal fibrosis by downregulation of ATF6

Endoplasmic reticulum (ER) stress is considered an important factor in the formation of fibrosis. Therefore, modulation of ER stress may represent a promising therapeutic strategy in renal fibrosis. MiR-185-5p has been identified to be implicated in TGF-β1-induced renal fibrosis; however, it is largely unknown whether and how miR-185-5p regulates ER stress in renal fibrosis. In this study, we demonstrated that miR-185-5p directly bound to ATF6, an ER stress-related protein, and downregulated the expression thereof. We subsequently constructed an in vitro model of renal fibrosis using HK2 cells treated with TGF-β1, and found that miR-185-5p attenuated ER stress and dedifferentiation of tubular epithelia by suppression of ATF6. In addition, we constructed an in vivo mouse model using unilateral urethral obstruction (UUO). Our in vivo findings showed that miR-185-5p reduced the expression of ER stress-related proteins and inhibited epithelial dedifferentiation via downregulation of ATF6, thereby improving UUO-induced renal fibrosis. Overall, our findings revealed that miR-185-5p exerts beneficial effects in renal fibrosis. Thus, the miR-185-5p/ATF6 regulatory pathway may be a potential target for therapeutic intervention in renal fibrosis.

Coexisting renal artery stenosis and metabolic syndrome magnifies mitochondrial damage, aggravating poststenotic kidney injury in pigs

OBJECTIVE

Renovascular disease (RVD) produces chronic underperfusion of the renal parenchyma and progressive ischemic injury. Metabolic abnormalities often accompany renal ischemia, and are linked to poorer renal outcomes. However, the mechanisms of injury in kidneys exposed to the ischemic and metabolic components of RVD are incompletely understood. We hypothesized that coexisting renal artery stenosis (RAS) and metabolic syndrome (MetS) would exacerbate mitochondrial damage, aggravating poststenotic kidney injury in swine.

METHODS

Domestic pigs were studied after 16 weeks of either standard diet (Lean) or high-fat/high-fructose (MetS) with or without superimposed RAS (n = 6 each). Single-kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multidetector-CT, and renal tubular mitochondrial structure, homeostasis and function and renal injury ex vivo.

RESULTS

Both RAS groups achieved significant stenosis. Single-kidney RBF and GFR were higher in MetS compared with Lean, but decreased in Lean+RAS and MetS+RAS vs. their respective controls. MetS and RAS further induced changes in mitochondrial structure, dynamics, and function, and their interaction (diet × ischemia) decreased matrix density, mitophagy, and ATP production, and lead to greater renal fibrosis.

CONCLUSION

Coexisting RAS and MetS synergistically aggravate mitochondrial structural damage and dysfunction, which may contribute to structural injury and dysfunction in the poststenotic kidney. These observations suggest that mitochondrial damage precedes loss of renal function in experimental RVD, and position mitochondria as novel therapeutic targets in these patients.

TTP-like syndrome: novel concept and molecular pathogenesis of endotheliopathy-associated vascular microthrombotic disease

TTP is characterized by microangiopathic hemolytic anemia and thrombocytopenia associated with brain and kidney dysfunction. It occurs due to ADAMTS13 deficiency. TTP-like syndrome occurs in critically ill patients with the similar hematologic changes and additional organ dysfunction syndromes. Vascular microthrombotic disease (VMTD) includes both TTP and TTP-like syndrome because their underlying pathology is the same disseminated intravascular microthrombosis (DIT). Microthrombi are composed of platelet-unusually large von Willebrand factor multimers (ULVWF) complexes. TTP occurs as a result of accumulation of circulating ULVWF secondary to ADAMTS13 deficiency. This protease deficiency triggers microthrombogenesis, leading to "microthrombi" formation in microcirculation. Unlike TTP, TTP-like syndrome occurs in critical illnesses due to complement activation. Terminal C5b-9 complex causes channel formation to endothelial membrane, leading to endotheliopathy, which activates two different molecular pathways (i.e., inflammatory and microthrombotic). Activation of inflammatory pathway triggers inflammation. Activation of microthrombotic pathway promotes platelet activation and excessive endothelial exocytosis of ULVWF from endothelial cells (ECs). Overexpressed and uncleaved ULVWF become anchored to ECs as long elongated strings to recruit activated platelets, and assemble "microthrombi". In TTP, circulating microthrombi typically be lodged in microvasculature of the brain and kidney, but in TTP-like syndrome, microthrombi anchored to ECs of organs such as the lungs and liver as well as the brain and kidneys, leading to multiorgan dysfunction syndrome. TTP occurs as hereditary or autoimmune disease and is the phenotype of ADAMTS13 deficiency-associated VMTD. But TTP-like syndrome is hemostatic disorder occurring in critical illnesses and is the phenotype of endotheliopathy-associated VMTD. Thus, this author's contention is TTP and TTP-like syndrome are two distinctly different disorders with dissimilar underlying pathology and pathogenesis.

Antiphospholipid Syndrome Nephropathy: From Pathogenesis to Treatment

Kidney damage is a well-recognized complication of the antiphospholipid syndrome (APS), either primary or systemic lupus erythematosus (SLE)-associated APS. Kidney involvement in APS involves a variety of manifestations, such as renal artery thrombosis or stenosis, renal vein thrombosis, allograft loss due to thrombosis after kidney transplantation, and injury to the renal microvasculature, also known as APS nephropathy. Biopsy in patients with APS nephropathy includes acute thrombotic microangiopathy lesions and chronic intrarenal vascular lesions such as interlobular fibrous intimal hyperplasia, arterial and arteriolar recanalizing thrombosis, fibrous arterial occlusion, and focal cortical atrophy. The most frequent clinical features are hypertension, microscopic hematuria, proteinuria (ranging from mild to nephritic levels), and renal insufficiency. It is uncertain whether antiphospholipid antibodies or other factors are implicated in the development of APS nephropathy, and whether it is driven mainly by thrombotic or by inflammatory processes. Experimental models and clinical studies of thrombotic microangiopathy lesions implicate activation of the complement cascade, tissue factor, and the mTORC pathway. Currently, the management of APS nephropathy relies on expert opinion, and consensus is lacking. There is limited evidence about the effect of anticoagulants, and their use remains controversial. Treatment approaches in patients with APS nephropathy lesions may include the use of heparin based on its role on complement activation pathway inhibition or the use of intravenous immunoglobulin and/or plasma exchange. Targeted therapies may also be considered based on potential APS nephropathy pathogenetic mechanisms such as B-cell directed therapies, complement inhibition, tissue factor inhibition, mTOR pathway inhibition, or anti-interferon antibodies, but prospective multicenter studies are needed to address their role.

Molecular characterization of the transition from acute to chronic kidney injury following ischemia/reperfusion

Though an acute kidney injury (AKI) episode is associated with an increased risk of chronic kidney disease (CKD), the mechanisms determining the transition from acute to irreversible chronic injury are not well understood. To extend our understanding of renal repair, and its limits, we performed a detailed molecular characterization of a murine ischemia/reperfusion injury (IRI) model for 12 months after injury. Together, the data comprising RNA-sequencing (RNA-seq) analysis at multiple time points, histological studies, and molecular and cellular characterization of targeted gene activity provide a comprehensive profile of injury, repair, and long-term maladaptive responses following IRI. Tubular atrophy, interstitial fibrosis, inflammation, and development of multiple renal cysts were major long-term outcomes of IRI. Progressive proximal tubular injury tracks with de novo activation of multiple Krt genes, including Krt20, a biomarker of renal tubule injury. RNA-seq analysis highlights a cascade of temporal-specific gene expression patterns related to tubular injury/repair, fibrosis, and innate and adaptive immunity. Intersection of these data with human kidney transplant expression profiles identified overlapping gene expression signatures correlating with different stages of the murine IRI response. The comprehensive characterization of incomplete recovery after ischemic AKI provides a valuable resource for determining the underlying pathophysiology of human CKD.

Therapeutic efficacy of bone marrow derived mesenchymal stromal cells versus losartan on adriamycin-induced renal cortical injury in adult albino rats

BACKGROUND

Renal disease is a major health problem. Recent studies have reported the efficacy of stem cell therapy in nephropathy animal models.

AIM OF THE WORK

This study was designed to investigate the therapeutic effectiveness of bone marrow-derived mesenchymal stromal cells (MSCs) versus losartan in the treatment of renal alterations induced by adriamycin (ADR).

MATERIALS AND METHODS

Thirty-five adult male albino rats were divided into four groups. Group I was the control group. Group II (adriamycin-treated group),which included ten rats that were injected with a single dose of adriamycin (15 mg/kg) intraperitoneally, was subdivided into subgroup IIa and IIb and they were sacrificed 1 week and 5 weeks after adriamycin injection, respectively. Group III was the adriamycin + losartan-treated group and 1 week after adriamycin injection five rats received 10 mg/kg of losartan orally and daily for 4 weeks. Group IV was the adriamycin + MSC-treated group); five rats were injected with adriamycin as group II then supplied with MSCs at a dose of 1 × 10(6) cells suspended in 0.5 mL of phosphate-buffered saline (PBS) per rat in the tail vein 1 week after adriamycin injection. Rats of this group were sacrificed 4 weeks after the stem cell injection. Blood urea nitrogen and serum creatinine were measured. Samples from renal cortex were processed for light and electron microscope examination. As regards light microscope, sections were stained with hematoxylin and eosin (H-E), periodic acid-Schiff (PAS), masson trichrome, proliferating cell nuclear antigen (PCNA) and Caspase-3 immunohistochemical stains. Morphometrical and statistical analyses were also conducted.

RESULTS

Examination of adriamycin-treated group revealed deterioration of renal functions and various degrees of renal structural alterations as vacuolated cytoplasm, dark nuclei and detached epithelial lining. Administration of losartan partially improved ADR-induced kidney dysfunction, whereas MSCs denoted a more ameliorative role evidenced by structural and functional recovery.

CONCLUSION

MSCs have a relevant therapeutic potential against ADR-induced renal damage. MSCs may accomplish this role by decreasing caspase-3 expression and increasing proliferating cell nuclear antigen staining which influence the regeneration of the kidney.

The metabolic syndrome induces early changes in the swine renal medullary mitochondria

The metabolic syndrome (MetS) is associated with nutrient surplus and kidney hyperfiltration, accelerating chronic renal failure. Mitochondria can be overwhelmed by substrate excess, leading to inefficient energy production and thereby tissue hypoxia. Mitochondrial dysfunction is emerging as an important determinant of renal damage, but whether it contributes to MetS-induced renal injury remains unknown. We hypothesized that early MetS induces kidney mitochondrial abnormalities and dysfunction, which would be notable in the vulnerable renal medulla. Pigs were studied after 16 weeks of diet-induced MetS, MetS treated for the last 4 weeks with the mitochondria-targeted peptide elamipretide (0.1 mg/kg SC q.d), and Lean controls (n = 7 each). Single-kidney renal blood flow, glomerular filtration rate, and oxygenation were measured in-vivo, whereas cortical and medullary mitochondrial structure and function and renal injurious pathways were studied ex-vivo. Blood pressure was slightly elevated in MetS pigs, and their renal blood flow and glomerular filtration rate were elevated. Blood oxygen level-dependent magnetic resonance imaging demonstrated that this was associated with medullary hypoxia, whereas cortical oxygenation remained intact. MetS decreased renal content of the inner mitochondrial membrane cardiolipin, particularly the tetra-linoleoyl (C18:2) cardiolipin species, and altered mitochondrial morphology and function, particularly in the medullary thick ascending limb. MetS also increased renal cytochrome-c-induced apoptosis, oxidative stress, and tubular injury. Chronic mitoprotection restored mitochondrial structure, ATP synthesis, and antioxidant defenses and decreased mitochondrial oxidative stress, medullary hypoxia, and renal injury. These findings implicate medullary mitochondrial damage in renal injury in experimental MetS, and position the mitochondria as a therapeutic target.

Modeling complement-driven diseases in transgenic mice: Values and limitations

Remarkable advances have been made over past decades in understanding the pathogenesis of complement-mediated diseases. This has led to development of new therapies for, and in some cases re-classification of, complement-driven diseases. This success is due to not only insight from human patients but also studies using transgenic animal models. Animal models that mimic human diseases are useful tools to understand the mechanism of disease and develop new therapies but there are also limitations due to species differences in their complement systems. This review provides a summary of transgenic animal models for three human diseases that are at the forefront of anti-complement therapy, paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy (C3G). They are discussed here as examples to highlight the values and limitations of animal modeling in complement-driven diseases.

Early atherosclerosis aggravates renal microvascular loss and fibrosis in swine renal artery stenosis

Renal function in patients with atherosclerosis and renal artery stenosis (ARAS) deteriorates more frequently than in nonatherosclerotic RAS. We hypothesized that ARAS aggravates stenotic-kidney micro vascular loss compared to RAS. Domestic pigs were randomized to normal, RAS, and ARAS (RAS fed a high-cholesterol diet) groups (n = 7 each). Ten weeks later stenotic-kidney oxygenation, renal blood flow, and glomerular filtration rate (GFR) were evaluated in vivo, and micro vascular density by micro-computed tomography. Blood pressure in both RAS and ARAS was elevated; and stenotic-kidney renal blood flow and GFR similarly decreased. RAS decreased the density of small-size cortical microvessels (<200 μm), whereas ARAS extended the decrease to medium-sized microvessels (200-300 μm). Cortical hypoxia and interstitial fibrosis increased in both RAS and ARAS but correlated inversely with micro vascular density only in RAS. Atherosclerosis aggravates loss of stenotic-kidney microvessels, yet additional determinants likely contribute to cortical hypoxia and fibrosis in swine ARAS.

The relevance of "non-criteria" clinical manifestations of antiphospholipid syndrome: 14th International Congress on Antiphospholipid Antibodies Technical Task Force Report on Antiphospholipid Syndrome Clinical Features

The purpose of this task force was to critically analyze nine non-criteria manifestations of APS to support their inclusion as APS classification criteria. The Task Force Members selected the non-criteria clinical manifestations according to their clinical relevance, that is, the patient-important outcome from clinician perspective. They included superficial vein thrombosis, thrombocytopenia, renal microangiopathy, heart valve disease, livedo reticularis, migraine, chorea, seizures and myelitis, which were reviewed by this International Task Force collaboration, in addition to the seronegative APS (SN-APS). GRADE system was used to evaluate the quality of evidence of medical literature of each selected item. This critical appraisal exercise aimed to support the debate regarding the clinical picture of APS. We found that the overall GRADE analysis was very low for migraine and seizures, low for superficial venous thrombosis, thrombocytopenia, chorea, longitudinal myelitis and the so-called seronegative APS and moderate for APS nephropathy, heart valve lesions and livedo reticularis. The next step can be a critical redefinition of an APS gold standard, for instance derived from the APS ACTION registry that will include not only current APS patients but also those with antiphospholipid antibodies not meeting current classification criteria.

Experimental coronary artery stenosis accelerates kidney damage in renovascular hypertensive swine

The impact of coronary artery stenosis (CAS) to renal injury is unknown. Here we tested whether the existence of CAS, regardless of concurrent atherosclerosis, would induce kidney injury and magnify its susceptibility to damage from co-existing hypertension (HT). Pigs (7 each) were assigned to Sham, left-circumflex CAS, renovascular HT, and CAS plus HT groups. Cardiac and non-stenotic kidney functions, circulating and renal inflammatory and oxidative markers, and renal and microvascular remodeling, were assessed 10 weeks later. Myocardial perfusion declined distal to CAS. Systemic levels of PGF2-α isoprostane, a marker of oxidative stress, increased in CAS and CAS plus HT, while single-kidney blood flow responses to acetylcholine were significantly blunted only in CAS plus HT compared to sham, HT, and CAS, indicating renovascular endothelial dysfunction. Tissue expression of inflammatory and oxidative markers were elevated in the CAS pig kidney, and further magnified in CAS plus HT, whereas angiogenic factor expression was decreased. Bendavia, a mitochondria-targeted peptide, decreased oxidative stress and improved renal function and structure in CAS. Furthermore, CAS and HT synergistically amplified glomerulosclerosis and renal fibrosis. Thus, mild myocardial ischemia, independent of systemic atherosclerosis, induced renal injury, possibly mediated by increased oxidative stress. Superimposed HT aggravates renal inflammation and endothelial dysfunction caused by CAS, and synergistically promotes kidney fibrosis, providing impetus to preserve cardiac integrity in order to protect the kidney.

Complement regulation in renal disease models

Activation of the complement system is tightly regulated by plasma and cell-associated complement regulatory proteins (CRPs), such as factor H (fH), decay-accelerating factor, and membrane cofactor protein. Animal models of disease have provided considerable insights into the important roles for CRPs in the kidney. Mice deficient in fH have excessive fluid phase C3 activation and inactivation, leading to deposition of inactivated C3b in glomerular capillary walls (GCW), comparable with dense deposit disease. In contrast, when fH lacks C-terminal surface targeting regions, local activation on the GCW leads to a disease reminiscent of thrombotic microangiopathy. The uniquely rodent protein, CR1-related y (Crry), has features analogous to human membrane cofactor protein. Defective Crry leads to unrestricted alternative pathway activation in the tubulointerstitium, resulting in pathologic features ranging from thrombotic microangiopathy (TMA), acute kidney injury, and tubulointerstitium nephritis. In the presence of initiators of the classic or lectin pathways, commonly in the form of immune complexes in human glomerular diseases, complement regulation is stressed, with the potential for recruitment of the spontaneously active alternative pathway. The threshold for this activation is set by CRPs; pathology is more likely when complement regulation is defective. Within the endocapillary region of the GCW, fH is key, while decay-accelerating factor and Crry are protective on mesangial cells and podocytes. Arguably, acquired alterations in these CRPs is a more common event, extending from pathologic states of cellular injury or production of inhibitory antibodies, to physiological fine tuning of the adaptive immune response.

Magnetic resonance elastography noninvasively detects in vivo renal medullary fibrosis secondary to swine renal artery stenosis

OBJECTIVES

Magnetic resonance elastography (MRE) can noninvasively sample tissue stiffness in vivo. Renal fibrosis secondary to renal artery stenosis (RAS), which is aggravated in atherosclerotic RAS (ARAS), may increase its stiffness. An increase in cortical stiffness in vivo can be masked by intrinsic hemodynamic determinants, whereas renal medullary stiffness is less dependent on renal hemodynamics. Therefore, this study tested the hypothesis that MRE-determined medullary stiffness would correspond to the histological degree of medullary fibrosis in stenotic kidneys in RAS and detect its exacerbation in ARAS.

MATERIALS AND METHODS

Seventeen pigs were studied 10 weeks after induction of unilateral RAS (n = 6), ARAS (n = 5), or sham (n = 6). Stiffness of the cortex and the medulla was determined through 3-dimensional MRE, and renal perfusion and function were determined using multidetector computed tomography. Kidney fibrosis was subsequently assessed ex vivo using the Masson trichrome staining.

RESULTS

Renal stenotic cortex and medulla were significantly more fibrotic in RAS and ARAS compared with healthy kidney. However, MRE detected increased stiffness in RAS compared with the healthy kidney (12.7 ± 0.41 kPa vs 10.7 ± 0.18 kPa; P = 0.004) only in the medulla, which was further increased in ARAS (16.6 ± 1.3 kPa; P = 0.017 vs RAS). Magnetic resonance elastography-derived medullary, but not cortical, stiffness significantly correlated with histological degree of fibrosis, although cortical and medullary fibroses were correlated. Renal blood flow and function were similarly decreased in RAS and ARAS compared with the healthy kidney.

CONCLUSIONS

Noninvasive 3-dimensional MRE detects increased renal medullary stiffness in RAS and ARAS in vivo, which correlates with its fibrosis ex vivo and may also reflect cortical fibrosis. Hence, MRE-derived medullary stiffness can be potentially useful in detecting renal fibrosis and track disease progression.

The spectrum of renal thrombotic microangiopathy in lupus nephritis

INTRODUCTION

Among various lupus renal vascular changes, thrombotic microangiopathy (TMA) presented with the most severe clinical manifestations and high mortality. The pathogenesis of TMA in systemic lupus erythematosus (SLE) was complicated. The aim of this study was to assess clinical manifestations, laboratory characteristics, pathological features and risk factors for clinical outcomes of lupus nephritis patients co-existing with renal TMA in a large cohort in China.

METHODS

Clinical and renal histopathological data of 148 patients with biopsy-proven lupus nephritis were retrospectively analyzed. Serum complement factor H, A Disintegrin and Metalloprotease with Thrombospondin type I repeats 13 (ADAMTS-13) activity, antiphospholipid antibodies and C4d deposition on renal vessels were further detected and analyzed.

RESULTS

In the 148 patients with lupus nephritis, 36 patients were diagnosed as co-existing with renal TMA based on pathological diagnosis. Among the 36 TMA patients, their clinical diagnoses of renal TMA were as followings: 2 patients combining with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome, 2 patients combining with anti-phospholipid syndrome, 2 patients with malignant hypertension, 1 patient with scleroderma and the other 29 patients presenting with isolated renal TMA. Compared with the non-renal TMA group, patients with renal TMA had significantly higher urine protein (7.09±4.64 vs. 4.75±3.13 g/24h, P=0.007) and serum creatinine (159, 86 to 215 vs. 81, 68 to 112 μmol/l, P<0.001), higher scores of total activity indices (AI) (P<0.001), endocapillary hypercellularity (P<0.001), subendothelial hyaline deposits (P=0.003), interstitial inflammation (P=0.005), glomerular leukocyte infiltration (P=0.006), total chronicity indices (CI) (P=0.033), tubular atrophy (P=0.004) and interstitial fibrosis (P=0.018). Patients with renal TMA presented with poorer renal outcome (P=0.005) compared with the non-TMA group. Renal TMA (hazard ratio (HR): 2.772, 95% confidence interval: 1.009 to 7.617, P=0.048) was an independent risk factor for renal outcome in patients with lupus nephritis. The renal outcome was poorer for those with both C4d deposition and decreased serum complement factor H in the TMA group (P=0.007).

CONCLUSIONS

There were various causes of renal TMA in lupus nephritis. Complement over-activation via both classical and alternative pathways might play an important role in the pathogenesis of renal TMA in lupus nephritis.

Membrane-bound complement regulatory proteins as biomarkers and potential therapeutic targets for SLE

For the last two decades, there had been remarkable advancement in understanding the role of complement regulatory proteins in autoimmune disorders and importance of complement inhibitors as therapeutics. Systemic lupus erythematosus is a prototype of systemic autoimmune disorders. The disease, though rare, is potentially fatal and afflicts women at their reproductive age. It is a complex disease with multiorgan involvement, and each patient presents with a different set of symptoms. The diagnosis is often difficult and is based on the diagnostic criteria set by the American Rheumatology Association. Presence of antinuclear antibodies and more specifically antidouble-stranded DNA indicates SLE. Since the disease is multifactorial and its phenotypes are highly heterogeneous, there is a need to identify multiple noninvasive biomarkers for SLE. Lack of validated biomarkers for SLE disease activity or response to treatment is a barrier to the efficient management of the disease, drug discovery, as well as development of new therapeutics. Recent studies with gene knockout mice have suggested that membrane-bound complement regulatory proteins (CRPs) may critically determine the sensitivity of host tissues to complement injury in autoimmune and inflammatory disorders. Case-controlled and followup studies carried out in our laboratory suggest an intimate relation between the level of DAF, MCP, CR1, and CD59 transcripts and the disease activity in SLE. Based on comparative evaluation of our data on these four membrane-bound complement regulatory proteins, we envisaged CR1 and MCP transcripts as putative noninvasive disease activity markers and the respective proteins as therapeutic targets for SLE. Following is a brief appraisal on membrane-bound complement regulatory proteins DAF, MCP, CR1, and CD59 as biomarkers and therapeutic targets for SLE.

Renoprotective effect of human umbilical cord-derived mesenchymal stem cells in immunodeficient mice suffering from acute kidney injury

It is unknown whether human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) can improve the renal function of patients suffering from acute kidney injury. Moreover, before beginning clinical trials, it is necessary to investigate this renoprotective effect of hUC-MSCs in a xenogeneic model of acute kidney injury. However, no previous studies have examined the application of hUC-MSCs to immunodeficient mice suffering from acute kidney injury. The objectives of this study were to examine whether hUC-MSCs could improve renal function in nonobese diabetic-severe combined immune deficiency (NOD-SCID) mice suffering from acute kidney injury, and to investigate the mechanism(s) for hUC-MSCs to improve renal function in this xenogeneic model. Early (3 hr) and late (12 hr) administrations of hUC-MSCs (10⁶ cells) were performed via the external jugular vein into NOD-SCID mice suffering from either folic acid (FA) (250 mg/kg body weight) or vehicle. The results showed that early administration of hUC-MSCs improved the renal function of NOD-SCID mice suffering from FA-induced acute kidney injury, as evidenced by decreased serum urea nitrogen and serum creatinine levels, as well as a reduced tubular injury score. The beneficial effects of hUC-MSCs were through reducing apoptosis and promoting proliferation of renal tubular cells. These benefits were independent of inflammatory cytokine effects and transdifferentiation. Furthermore, this study is the first one to show that the reduced apoptosis of renal tubular cells by hUC-MSCs in this xenogeneic model is mediated through the mitochondrial pathway, and through the increase of Akt phosphorylation.

C6 knock-out mice are protected from thrombophilia mediated by antiphospholipid antibodies

BACKGROUND

Complement activation plays a role in pathogenesis of the antiphospholipid syndrome (APS), but the involvement of the C5b-9 membrane attack complex (MAC) is unknown. Here we studied the effects of human polyclonal antiphospholipid (aPL) antibodies on thrombosis and tissue factor (TF) up-regulation in C6 deficient (C6(-/-)) mice.

METHODS

C6(-/-) mice or the wild-type C3H/HeJ (C6(+/+)) mice were injected twice with IgG-APS (n = 2) or IgM-APS (n = 1) isolated from APS patients or with the corresponding control immunoglobulins (Igs) of normal human serum, (NHS) (IgG-NHS or IgM-NHS). Then, the sizes of induced thrombi in the femoral vein were determined 72 hours after the first injection. Tissue factor was determined in homogenates of carotid arteries and in peritoneal macrophages.

RESULTS

Thrombus sizes were significantly larger in C6(+/+) treated with IgG-APS1 or with IgG-APS2 or with IgM-APS when compared with C6(+/+) mice treated with IgG-NHS or with IgM-NHS, respectively. The sizes of thrombi were significantly smaller in the C6(-/-) mice injected with IgG-APS1, IgG-APS2 or IgM-APS (p < 0.001), compared to their C6(+/+) counterparts showing an important abrogation of thrombus formation in mice lacking C6. The TF expression and activity in the C6(-/-) mice treated with IgG-APS or IgM-APS were diminished when compared to C3H/HeJ (C6(+/+)) mice treated with the same Igs. All mice injected with IgG-APS and IgM-APS had medium-high titers of anticardiolipin (aCL) and anti-β(2)glycoprotein I (aβ(2)GPI) antibodies.

CONCLUSIONS

These data indicate that the C6 component of the complement system mediates aPL-thrombogenic effects, underscoring an important pathogenic mechanism and indicating the possibility of inhibiting complement to ameliorate APS-related manifestations.

Complement-mediated injury and protection of endothelium: lessons from atypical haemolytic uraemic syndrome

The complement system provides a vital defence against invading pathogens. As an intrinsic system it is always 'on', in a state of constant, low level activation. This activation is principally mediated through the deposition of C3b on to pathogenic surfaces and host tissues. C3b is generated by spontaneous 'tick over' and formal activation of the alternative pathway, and by activation of the classical and lectin pathways. If the deposited C3b is not appropriately regulated, there is progression to terminal pathway complement activation via the C5 convertases, generating the potent anaphylotoxin C5a and the membrane attack complex C5b-9. Unsurprisingly, these highly active components have the potential to cause injury to bystander host tissue, including the vascular endothelium. As such, complement activation on endothelium is normally tightly controlled by a large number of fluid-phase and membrane bound inhibitors, in an attempt to ensure that propagation of complement activation is appropriately restricted to invading pathogens and altered 'self', e.g. apoptotic and necrotic cells. The kidney is increasingly recognised as a site at particular risk from complement-mediated endothelial injury. Both genetic and acquired defects which impact on complement regulation predispose to this susceptibility. The thrombotic microangiopathy, haemolytic uraemic syndrome (HUS), will be used to illustrate the mechanisms by which the endothelial cell injury occurs. Finally, the underlying rationale for current and future potential therapeutic interventions in HUS and also the opportunities for enhancing endothelial defence to prevent relapsing disease through increased complement cytoprotective strategies will be summarised.

Podocyte number predicts progression of proteinuria in IgA nephropathy

Podocyte injury is a feature of glomerulopathies associated with proteinuria, which in turn has been used as a clinical prognostic factor for glomerular diseases. The goal of this study is to investigate the relationship between podocyte injury found in biopsied renal tissue and change of proteinuria in IgA nephropathy (IgAN). In all, 35 patients with biopsy-proven IgAN and proteinuria (>1.0 g per 24 h) were enrolled in the IgAN group, while 8 patients with excision of renal harmatoma or carcinoma served as kidney controls (Control). Immunohistochemistry was applied to detect the expression of nestin, cell-cycle regulatory protein p27, as well as complement C5b-9 and complement receptor 1 (CR1). Podocyte foot process width (FPW) and podocyte population in renal biopsied samples were measured by morphometric analysis. On the basis of the podocyte density (Nv), the IgAN patients were divided into podocytopenic group (n=17, Nv<57.10 /microm(3) x 10(6)) and normopodocytic group (n=18, Nv> or =57.10 /microm(3) x 10(6)). Changes of proteinuria were followed for 18 months after biopsy. Compared with the Control, IgAN glomeruli had reduced podocyte expression of p27 and nestin along with decreased podocyte number. IgAN glomeruli also showed activation of C5b-9 in mesangial and subepithelial areas with decreased CR1 expression in podocytes. The C5b-9 positivity was inversely correlated with the number of WT-1-positive podocytes. Although the magnitude of proteinuria at biopsy correlated with podocyte FPW (P<0.05), the change in the amount of proteinuria expressed as proteinuria progression rate significantly correlated with the podocyte density. Thus, the normopodocytic group showed significantly lower proteinuria progression rate than the podocytopenic group regardless the comparable clinical features at biopsy and treatment regimen between the two groups. The results of this study indicate that, in IgAN, podocyte injury is involved in development of proteinuria and loss of podocytes predicts progression of the proteinuria. Complement activation may contribute to podocyte damage in IgAN.

Antiphospholipid antibody profiles in lupus nephritis with glomerular microthrombosis: a prospective study of 124 cases

Introduction

Glomerular microthrombosis (GMT) is a common vascular change in patients with lupus nephritis (LN). The mechanism underlying GMT is largely unknown. Although several studies have reported the association of antiphospholipid antibodies (aPL) with GMT, the relation between GMT and aPL remains controversial. Previous studies have demonstrated that some aPL could bind to several hemostatic and fibrinolytic proteases that share homologous enzymatic domains. Of the protease-reactive aPL, some can inhibit the anticoagulant activity of activated protein C and the fibrinolytic function of plasmin, and hinder the antithrombin inactivation of thrombin. The purpose of this study was to investigate the prevalence of GMT in LN patients and examine the relation between the aPL profiles (including some protease-reactive aPL) and GMT.

Methods

Renal biopsy specimens were examined for the presence of glomerular microthrombi. Plasma samples from 25 LN patients with GMT (LN-GMT group) and 99 LN patients without GMT (LN-non-GMT group) were tested for lupus anticoagulant and antibodies against cardiolipin, β2 glycoprotein I, plasmin, thrombin, tissue plasminogen activator, and annexin II.

Results

The prevalence of GMT in LN patients was 20.2%. Compared with the LN-non-GMT group, the LN-GMT group had an elevated systemic lupus erythematosus disease activity index; elevated renal tissue injury activity and chronicity indices; elevated serum creatinine, blood urea nitrogen, and proteinuria levels; a lower serum C3 level and much intense glomerular C3, C1q staining; and a higher frequency of hypertension (P < 0.05 for all). Additionally, the detection rate of lupus anticoagulant, immunoglobulin G (IgG) anti-β2 glycoprotein I and anti-thrombin antibodies were higher in the LN-GMT group than in the LN-non-GMT group (P < 0.05 for all). No statistical differences were found in the detection rates of IgG anti-cardiolipin, plasmin, tissue plasminogen activator, or annexin II antibodies (P > 0.05 for all). No detectable difference in IgM autoantibodies to the above antigens was observed between the two groups.

Conclusions

GMT occurs in approximately 20.2% of LN patients. Patients with GMT have severer renal tissue injuries and poorer renal functions than patients without GMT. The lupus anticoagulant and antibodies against β2 glycoprotein I and thrombin may play a role in GMT.

Exogenous bone marrow cells do not rescue non-irradiated mice from acute renal tubular damage caused by HgCl2, despite establishment of chimaerism and cell proliferation in bone marrow and spleen

OBJECTIVE

Various studies have shown that bone marrow stem cells can rescue mice from acute renal tubular damage under a conditioning advantage (irradiation or cisplatin treatment) favouring donor cell engraftment and regeneration; however, it is not known whether bone marrow cells (BMCs) can contribute to repair of acute tubular damage in the absence of a selection pressure for the donor cells. The aim of this study was to examine this possibility.

MATERIALS AND METHODS

Ten-week-old female mice were assigned into control non-irradiated animals having only vehicle treatment, HgCl(2)-treated non-irradiated mice, HgCl(2)-treated non-irradiated mice infused with male BMCs 1 day after HgCl(2), and vehicle-treated mice with male BMCs. Tritiated thymidine was given 1 h before animal killing.

RESULTS

Donor BMCs could not alleviate non-irradiated mice from acute tubular damage caused by HgCl(2), deduced by no reduction in serum urea nitrogen combined with negligible cell engraftment. However, donor BMCs could home to the bone marrow and spleen and display proliferative activity. This is the first report to show that despite no preparative myeloablation of recipients, engrafted donor BMCs can synthesize DNA in the bone marrow and spleen.

CONCLUSIONS

Exogenous BMCs do not rescue non-irradiated mice from acute renal tubular damage caused by HgCl(2), despite establishment of chimerism and cell proliferation in bone marrow and spleen.

Haematopoietic lineage-committed bone marrow cells, but not cloned cultured mesenchymal stem cells, contribute to regeneration of renal tubular epithelium after HgCl 2 -induced acute tubular injury

OBJECTIVE

Our previous studies have demonstrated that endogenous bone arrow cells (BMCs) contribute to renal tubular regeneration after acute tubular injury. The aim of this study was to examine which fraction of BMCs, haematopoietic lineage marrow cells (HLMCs) or mesenchymal stem cells (MSCs), are effective.

MATERIALS AND METHODS

Six-week-old female mice were lethally irradiated and were transplanted with female enhanced green fluorescent protein-positive (GFP(+)), plastic on-adherent marrow cells (as a source of HLMCs) plus cloned cultured male GFP(-) MSCs. Four weeks later, they were assigned into two groups: control mice with vehicle treatment and mice treated with HgCl2. Tritiated thymidine was given 1 h before animal killing which occurred at intervals over 2 weeks. Kidney sections were stained for a tubular epithelial marker, cell origin indicated by GFP immunohistochemistry or Y chromosome in situ hybridization; periodic acid-Schiff staining was performed, and samples were subjected to autoradiography. One thousand consecutive renal tubular epithelial cells per mouse, in S phase, were scored as either female (indigenous) GFP+(HLMC-derived) or male (MSC-derived).

RESULTS

Haematopoietic lineage marrow cells and MSCs stably engrafted into bone marrow and spleen, but only HLMC-derived cells, not MSCs, were found in the renal tubules and were able to undergo DNA synthesis after acute renal injury. A few MSCs were detected in the renal interstitium, but their importance needs to be further explored.

CONCLUSION

Haematopoietic lineage marrow cells, but not cloned cultured MSCs, can play a role not only in normal wear-and-tear turnover of renal tubular cells, but also in repair after tubular injury.

Pathogenic role of antiphospholipid antibodies

The antiphospholipid antibody syndrome (APS) is characterized by recurrent arterial and venous thrombosis and/or pregnancy in association with antiphospholipid (aPL) antibodies. The pathogenic mechanisms in APS that lead to in vivo injury are incompletely understood. Recent evidence suggests that APL antibodies alter regulation of haemostasis and induce activation of complement. We will discuss the current knowledge on how aPL antibodies trigger increased inflammation and enhanced thrombotic tendency, and thereby lead to tissue damage.

HSP72 attenuates renal tubular cell apoptosis and interstitial fibrosis in obstructive nephropathy

Although heat shock protein 72 kDa (HSP72) protects tubular epithelium from a variety of acute insults, its role in chronic renal injury and fibrosis is poorly characterized. In this study, we tested the hypothesis that HSP72 reduces apoptosis and epithelial-to-mesenchymal transition (EMT), important contributors to tubular cell injury in vitro and in vivo. In rats, orally administered geranylgeranylacetone (GGA), an agent that selectively induces HSP72, markedly reduced both apoptosis and cell proliferation in tubular epithelium and decreased both interstitial fibroblast accumulation and collagen I deposition after unilateral ureteric obstruction, a model of chronic renal tubulointerstitial fibrosis and dysfunction. In cultured renal NRK52E cells, exposure to TGF-beta1 induced EMT and apoptosis, major causes of renal fibrosis and tubular atrophy, respectively. Exposure to a pan-caspase inhibitor (ZVAD-FMK) prevented TGF-beta1-induced apoptosis but did not reduce EMT. In contrast, selective HSP72 expression in vitro inhibited EMT caused by TGF-beta1 as indicated by preserving the E-cadherin expression level and alpha-smooth muscle actin induction. Small interfering RNA directed against HSP72 blocked the cytoprotective effects of HSP72 overexpression on EMT in TGF-beta1-exposed cells. Taken together, our data indicate that HSP72 ameliorates renal tubulointerstitial fibrosis in obstructive nephropathy by inhibiting both renal tubular epithelial cell apoptosis and EMT.

Activation of intrarenal complement system in mouse model for chronic cyclosporine nephrotoxicity

PURPOSE

Local activation of the complement system plays a role in target organ damage. The aim of our study was to investigate the influence of cyclosporine (CsA)- induced renal injury on the complement system in the kidney.

MATERIALS AND METHODS

Mice fed a low salt (0.01%) diet were treated with vehicle (VH, olive oil, 1 mL/kg/day) or CsA (30 mg/kg/day) for one or four weeks. Induction of chronic CsA nephrotoxicity was evaluated with renal function and histomorphology. Activation of the complement system was assessed through analysis of the expression of C3, C4d, and membrane attack complex (MAC), and the regulatory proteins, CD46 and CD55. CsA treatment induced renal dysfunction and typical morphology (tubulointerstitial inflammation and fibrosis) at four weeks.

RESULTS

CsA-induced renal injury was associated with increased the expression of C3, C4d, and MAC (C9 and upregulation of complement regulatory proteins (CD 46 and CD55). Immunohistochemistry revealed that the activated complement components were mainly confined to the injured tubulointerstitium.

CONCLUSION

CsA-induced renal injury is associated with activation of the intrarenal complement system.

Pathogenesis and prognosis of thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is a clinicopathological syndrome characterized by thrombosis formation in the microvasculature of various organs. Included in the broad category of TMA are the hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Typical HUS is caused by Escherichia coli O157:H7, which produces the Shiga-like toxins; Stx-1 and Stx-2. In addition to damaging endothelial cells via the inhibition of protein synthesis, Shiga-like toxins also activate endothelial cells to produce inflammatory mediators, amplifying the prothrombogenic state. Although most patients with typical HUS recover renal functions, recent analysis has shown that typical HUS is not a benign disease in the long term. Genetic abnormalities of complement regulatory proteins predispose patients to atypical HUS. Mutations in factor H, membrane cofactor protein, and factor I are known to be associated with atypical HUS. Atypical HUS forms have a poor outcome and show recurrent and progressive courses. Autoimmune IgG inhibitors of a disintegrin and metalloprotease, with thrombospodin-1-like domains (ADAMTS) 13 and mutations of the ADAMTS13 gene lead to the development of TTP. Without treatment, TTP is associated with a very high mortality rate. As it is for atypical HUS, plasma exchange is currently the most feasible treatment for TTP. Etiological diagnosis at the bedside and the development of disease-specific therapeutic modalities will enable us to optimize the management of patients with TMA and improve their prognosis in the future.

A classification of hemolytic uremic syndrome and thrombotic thrombocytopenic purpura and related disorders

The diagnostic terms hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are based on historical and overlapping clinical descriptions. Advances in understanding some of the causes of the syndrome now permit many patients to be classified according to etiology. The increased precision of a diagnosis based on causation is important for considering logical approaches to treatment and prognosis. It is also essential for research. We propose a classification that accommodates both a current understanding of causation (level 1) and clinical association in cases for whom cause of disease is unclear (level 2). We tested the classification in a pediatric disease registry of HUS. The revised classification is a stimulus to comprehensive investigation of all cases of HUS and TTP and is expected to increase the proportion of cases in whom a level 1 etiological diagnosis is confirmed.

Mechanisms of immune-deposit formation and the mediation of immune renal injury

The passive trapping of preformed immune complexes is responsible for some forms of glomerulonephritis that are associated with mesangial or subendothelial deposits. The biochemical characteristics of circulating antigens play important roles in determining the biologic activity of immune complexes in these cases. Examples of circulating immune complex diseases include the classic acute and chronic serum sickness models in rabbits, and human lupus nephritis. Immune deposits also form "in situ". In situ immune deposit formation may occur at subepithelial, subendothelial, and mesangial sites. In situ immune-complex formation has been most frequently studied in the Heymann nephritis models of membranous nephropathy with subepithelial immune deposits. While the autoantigenic target in Heymann nephritis has been identified as megalin, the pathogenic antigenic target in human membranous nephropathy had been unknown until the recent identification of neutral endopeptidase as one target. It is likely that there is no universal antigen in human membranous nephropathy. Immune complexes can damage glomerular structures by attracting circulating inflammatory cells or activating resident glomerular cells to release vasoactive substances, cytokines, and activators of coagulation. However, the principal mediator of immune complex-mediated glomerular injury is the complement system, especially C5b-9 membrane attack complex formation. C5b-9 inserts in sublytic quantities into the membranes of glomerular cells, where it produces cell activation, converting normal cells into resident inflammatory effector cells that cause injury. Excessive activation of the complement system is normally prevented by a series of circulating and cell-bound complement regulatory proteins. Genetic deficiencies or mutations of these proteins can lead to the spontaneous development of glomerular disease. The identification of specific antigens in human disease may lead to the development of fundamental therapies. Particularly promising future therapeutic approaches include selective immunosuppression and interference in complement activation and C5b-9-mediated cell injury.

Requirement of activation of complement C3 and C5 for antiphospholipid antibody-mediated thrombophilia

OBJECTIVE

Antiphospholipid antibodies (aPL) have been shown to induce thrombosis, activate endothelial cells, and induce fetal loss. The pathogenesis of aPL-induced thrombosis, although not completely understood, may involve platelet and endothelial cell activation as well as procoagulant effects of aPL directly on clotting pathway components. Recent studies have shown that uncontrolled complement activation leads to fetal death in aPL-treated mice. In this study, we tested the hypothesis that aPL are responsible for activation of complement, thus generating split products that induce thrombosis.

METHODS

To study thrombus dynamics and adhesion of leukocytes we used in vivo murine models of thrombosis and microcirculation, in which injections of aPL were used.

RESULTS

Mice deficient in complement components C3 and C5 were resistant to the enhanced thrombosis and endothelial cell activation that was induced by aPL. Furthermore, inhibition of C5 activation using anti-C5 monoclonal antibodies prevented thrombophilia induced by aPL.

CONCLUSION

These data show that complement activation mediates 2 important effectors of aPL, induction of thrombosis and activation of endothelial cells.

Protection of endothelial cells by dextran sulfate in rats with thrombotic microangiopathy

The characteristic features of thrombotic microangiopathy (TMA) include glomerular and peritubular capillary endothelial cell injury in association with loss of heparan sulfate proteoglycans on the cell surface and thrombus formation, followed by subsequent ischemic tubulointerstitial damage. It therefore was hypothesized that dextran sulfate (DXS) may protect the kidney against endothelial damage in a model of TMA. TMA was induced in rats by renal artery perfusion of an antiglomerular endothelial antibody, followed by the administration of DXS or vehicle. Renal damage was assessed by histologic analysis and measurements of blood urea nitrogen and creatinine. Whereas control rats developed severe renal failure with extensive glomerular and tubular injury, administration of DXS significantly protected renal function and preserved the glomerular endothelium and peritubular capillaries. The beneficial effect of DXS could be attributed to the ability of DXS to protect endothelial cells from coagulation and complement activation, as demonstrated by the histologic analysis. In addition, binding of the administered DXS to the surface of the glomerular endothelium was confirmed in TMA rats, suggesting that DXS acts as a "repair coat" of injured glomerular endothelium. In conclusion, DXS protects the kidney from experimental TMA. This protection may be mediated by DXS's binding directly to the surface of glomerular endothelium and amelioration of coagulation, complement activation, and cellular matrix loss.

Novel C5a regulators in inflammatory disease

Complement is part of the innate immune system, acting to protect the host from microorganisms such as bacteria, and other foreign and abnormal cells. Although primarily protective, complement activation can also cause damage to the host. In a number of inflammatory diseases, including rheumatoid arthritis and dermatitis, there is excessive and inappropriate complement activation. Many of the toxic effects seen in these conditions are attributable to the excessive production of the anaphylatoxin C5a, which may contribute to both the initiation and progression of the disease. Therefore, the regulation of C5a production and modulation of its function are good pharmacological targets in these disorders. As yet, there are no effective agents for the therapeutic regulation of C5a in routine clinical practice. This review describes the role of C5a in inflammatory disease, animal models used to study C5a-related effects, and current strategies aimed at regulating C5a. There is also a discussion of the strengths and weaknesses of these approaches, and an outline of the likely progress of this class of drugs in the future.

Complement Activation: A Novel Pathogenic Mechanism in the Antiphospholipid Syndrome

Antiphospholipid antibodies (aPLs) have been shown to induce thrombosis, activate endothelial cells, and induce fetal loss. The pathogenesis of aPL-induced thrombosis is incompletely understood, but it is thought to involve platelet and endothelial cell activation as well as pro-coagulant effects of aPL antibody directly on clotting pathway components. Recent studies have shown that uncontrolled complement activation leads to fetal death in aPL-antibody treated mice. We hypothesized that aPL antibodies activate complement, generating split products that induce thrombosis. To test this hypothesis, we used an in vivo model of thrombosis in which aPL antibodies induce a significant increase in thrombus size and a mouse model of endothelial cell activation in which aPLs induce significant adhesion of leukocytes (WBCs) to endothelial cells. We found that mice deficient in complement components C3 and C5 were resistant to enhanced thrombosis and endothelial cell activation induced by aPL antibodies. Furthermore, inhibition of C5 activation using anti-C5 mAb prevented thrombophilia induced by aPL antibodies. Our data show that complement activation mediates two important effectors of aPL antibodies: induction of thrombosis and endothelial activation.

Proliferation of bone marrow-derived cells contributes to regeneration after folic acid-induced acute tubular injury

Studies of tissue from recipients of bone marrow transplantation or organ allograft suggest that bone marrow-derived cells (BMDC) may differentiate into a variety of nonhematologic tissues, including renal tubular epithelium. The aims of this study were to examine whether BMDC contribute to recovery after acute renal injury and to assess the effects of cytokine mobilization on regeneration. Female mice (6 wk old) were lethally irradiated and transplanted with male bone marrow (BM) cells and later assigned into control, folic acid-treatment, and folic acid-treatment with granulocyte-colony stimulating factor (G-CSF), and control with G-CSF. Tritiated thymidine was given 1 h before death. Kidney sections were stained for a tubular epithelial marker, Y chromosome (in situ hybridization), periodic acid-Schiff staining, and subjected to autoradiography. Renal tubular epithelial cells in S-phase were scored as female (indigenous) or male (BM-derived). This is the first report to show that BMDC can respond by engrafting the renal tubules and undergo DNA synthesis after acute renal injury. BMDC contributed to the renal tubular epithelial cell population, although most (90%) renal tubular regeneration came from female indigenous cells. Some evidence was found for cell fusion between indigenous renal tubular cells and BMDC, but this was infrequent and the significance and consequences of cell fusion in the kidney are unresolved. G-CSF treatment nearly doubled the frequency of thymidine-labeled BM-derived tubular cells and might facilitate the recovery of renal tubular epithelium.

Possible mechanism for medial smooth muscle cell injury in diabetic nephropathy: Glycoxidation-mediated local complement activation

BACKGROUND

Although recent studies have emphasized the pathogenic role of intrarenal muscular arteries in patients with diabetic nephropathy, notice has not been taken of their pathological characteristics. We focused on medial smooth muscle cell (SMC) injury and the involvement of glycoxidation and complement activation.

METHODS

Renal samples were obtained at autopsy from patients with diabetes mellitus (DM), patients with hypertension without renal involvement (n = 9), patients with benign nephrosclerosis (n = 7), and age-matched control subjects (n = 12). Patients with DM had glomerulosclerosis classified as severe (n = 9; DM-sev), moderate (n = 11; DM-mod), and minimal (n = 7). Renal samples were immunohistochemically determined. Activation of plasma complement from healthy subjects using advanced glycation end products (AGEs) also was performed.

RESULTS

A marked SMC loss was noted in the media of patients with DM-sev and DM-mod. A membrane attack complex (MAC) observed in the area with SMC loss correlated well with the loss. Considerable carboxymethyllysine (CML), an oxidatively modified AGE, was deposited in the area with SMC loss in patients with DM-mod and DM-sev. Degrees of MAC deposition, SMC loss, and CML deposition were greater in the DM-sev group than the non-DM groups. Another oxidative product, acrolein, colocalized with CML. Plasma complements were not activated by AGE-modified bovine serum albumin in our in vitro assays, which included a complement hemolytic activity assay and determination of complement fragments, including C4d, C3bB, iC3b, and MAC.

CONCLUSION

It is strongly suggested that medial SMC injury in intrarenal arteries is caused by interaction between glycoxidation and complement activation and contributes to the progression of diabetic nephropathy.

CD59a deficiency exacerbates accelerated nephrotoxic nephritis in mice

CD59 is a complement regulatory protein that inhibits the terminal part of the complement system, the membrane attack complex (MAC), a mediator of renal injury. Mice deficient in the Cd59a gene (mCd59a-/-) were used to investigate the role of CD59 in experimentally induced accelerated nephrotoxic nephritis, a model of immune complex-mediated glomerulonephritis. After accelerated nephrotoxic nephritis was induced by administration of sheep nephrotoxic globulin, mCd59a-/- mice and strain-matched controls on two genetic backgrounds, 129/Sv x C57BL/6 and 129/Sv, were examined. For both, mCd59a-/- mice developed significantly greater glomerular cellularity than wild-type (WT) mice at day 5 after administration. At day 10 post-administration, mCd59a-/- mice exhibited more glomerular thrombosis than WT mice (thrombosis score, 1.8 [range, 1.4 to 4.0] versus 0.8 [range, 0.2 to 1.5] quadrants thrombosed per glomerulus, respectively; P = 0.0006). In the majority of experiments, mCd59a-/- mice also had significantly more proteinuria than controls; however, there was no difference in serum creatinine or albumin. Quantitative immunofluorescence of kidney sections revealed significantly more C9 (as a marker of MAC) deposition within glomeruli of mCd59a-/- mice than WT controls (P < 0.001). There was no difference in deposition of C3 and sheep IgG between the two experimental groups. The lack of CD59a, by allowing unregulated MAC deposition, exacerbates the renal injury in this model of immune complex-mediated glomerulonephritis.

Imbalance of T-cell subsets in angiotensin II-infused hypertensive rats with kidney injury

Blockade of angiotensin (Ang) II is efficient in various renal diseases. Although interest has focused on the hemodynamic changes and reduction of proteinuria, recent studies emphasize the nonhemodynamic effects of Ang II on kidney injury. The aim of this study was to clarify the mechanisms of Ang II on the immune system that alter the balance of helper T-cell (Th) subsets. We used a continuous, Ang II infusion model of rats that develop hypertension, proteinuria, and tubulointerstitial damage, including de novo expression of alpha-smooth muscle actin and loss of endothelial cells. We isolated T cells from the spleen and measured cytokine levels by ELISA systems. Ang II-infused rats showed an increase in the Th1 cytokine gamma-interferon and a decrease in the Th2 cytokine interleukin-4. The same change in cytokine mRNA expression in the spleen and kidney was confirmed by quantitative polymerase chain reaction analysis. Our ELISPOT assay showed an increase in the number of gamma-interferon-secreting T cells by Ang II. To investigate whether these changes were specific effects of Ang II, we treated the model rats with the Ang II receptor blocker (ARB) olmesartan or the nonspecific vessel dilator hydralazine. Administration of the ARB ameliorated disease manifestations and the imbalance in Th subsets, whereas hydralazine did not, despite comparable effects on blood pressure. These results demonstrate a direct role of Ang II in the modification of Th balance. The imbalance of Th subsets was associated with hypertensive kidney injury induced by Ang II. Some of the beneficial effects of ARBs might be explained by their immunomodulatory reactions.

ET(B) receptor protects the tubulointerstitium in experimental thrombotic microangiopathy

BACKGROUND

The characteristic features of thrombotic microangiopathy (TMA) include glomerular and peritubular capillary endothelial cell injury with thrombus formation and subsequent ischemic tubulointerstitial damage. The endothelin ET(B) receptor has been shown to mediate both endothelial cell proliferation and vasodilation, and we therefore hypothesized that blockade of this receptor might promote more severe injury in this model.

METHODS

TMA was induced in recently established transgenic rats that lack expression of ET(B) receptor in the kidney; these animals were compared to control rats with TMA both in the short-term (days 1 and 3) when acute glomerular injury was most manifest, and the long-term (day 17) when glomeruli have recovered but tubulointerstitial injury is still present. Renal damage was assessed by histological analysis and blood urea nitrogen (BUN) measurements.

RESULTS

No difference in the TMA model was observed between rats with and without ET(B) receptor on days 1 or 3. At day 17, however, rats without the ET(B) receptor showed more severe tubulointerstitial injury compared with those with ET(B) receptor, which was associated with higher BUN levels. The tubulointerstitial damage was associated with a more severe loss of peritubular capillaries.

CONCLUSIONS

These findings suggest that the ET(B) receptor may protect peritubular capillaries under the ischemic insult, and serve a defensive role in the tubulointerstitium induced by renal microvascular injury.

A complement-dependent model of thrombotic thrombocytopenic purpura induced by antibodies reactive with endothelial cells

Thrombotic thrombocytopenic purpura (TTP) is an immunologically mediated disease characterized by thrombocytopenia, hemolytic anemia, and pathologic changes in various organs, including the kidney, which are secondary to widespread thromboses. Central to TTP is platelet activation, which may occur from a variety of mechanisms, including endothelial cell activation or injury. In this study, injection of K6/1, a monoclonal antibody with widespread reactivity toward endothelia, led to dose-dependent thrombocytopenia in rats. This was magnified if animals were preimmunized with mouse IgG, thereby resulting in an accelerated autologous phase of injury. In this setting, significant anemia also resulted. Rats injected with K6/1 developed renal injury, consisting of tubular damage and glomerular thrombi. Thrombocytopenia and renal morphological abnormalities were eliminated if animals were complement depleted with cobra venom factor prior to K6/1 injection and worsened when the activity of the ubiquitous complement regulator Crry was inhibited with function-neutralizing antibodies. Therefore, we have developed a complement-dependent model of TTP in rats by injecting monoclonal antibodies reactive with endothelial cells. Antibody-directed complement activation leads to stimulation of platelets, through direct interactions with complement fragments and/or indirectly through endothelial cell activation or injury, with the subsequent development of TTP.

In vivo klotho gene transfer ameliorates angiotensin II-induced renal damage

The klotho gene, originally identified by insertional mutagenesis in mice, suppresses the expression of multiple aging-associated phenotypes. This gene is predominantly expressed in the kidney. Recent studies have shown that expression of renal klotho gene is regulated in animal models of metabolic diseases and in humans with chronic renal failure. However, little is known about the mechanisms and the physiological relevance of the regulation of the expression of the klotho gene in the kidney in some diseased conditions. In the present study, we first investigated the role of angiotensin II in the regulation of renal klotho gene expression. Long-term infusion of angiotensin II downregulated renal klotho gene expression at both the mRNA and protein levels. This angiotensin II-induced renal klotho downregulation was an angiotensin type 1 receptor-dependent but pressor-independent event. Adenovirus harboring mouse klotho gene (ad-klotho, 3.3x10(10) plaque forming units) was also intravenously administered immediately before starting angiotensin II infusion in some rats. This resulted in a robust induction of Klotho protein in the liver at day 4, which was still detectable 14 days after the gene transfer. Ad-klotho gene transfer, but not ad-lacZ gene transfer, caused an improvement of creatinine clearance, decrease in urinary protein excretion, and amelioration of histologically demonstrated tubulointerstitial damage induced by angiotensin II administration. Our data suggest that downregulation of the renal klotho gene may have an aggravative role in the development of renal damage induced by angiotensin II, and that induction of the klotho gene may have therapeutic possibilities in treating angiotensin II-induced end organ damage.