Rituximab targets podocytes in recurrent focal segmental glomerulosclerosis

Long-term prognosis of adult patients with steroid-dependent minimal change nephrotic syndrome following rituximab treatment

This study was to evaluate the long-term efficacy and safety of a single-dose rituximab regimen rituximab treatment in adult patients with steroid-dependent minimal change nephrotic syndrome (MCNS). We conducted a prospective cohort study with historical controls to evaluate the effect of single-dose infusions of rituximab at 375 mg/m2 BSA per dose administered at intervals of 6 months for a period of 24 months. At the end of the 24-month period, the patients were divided into the treatment continuation (n = 20) and treatment discontinuation (n = 5) groups according to their intention to continue/discontinue the treatment. A significant reduction in the total number of relapses was observed during the 24-month period after the first rituximab infusion as compared with that during the 24-month period before the first rituximab infusion (108 vs. 8, P < 0.001). Complete remission was induced/maintained in all patients from 12 to 24 months after the first rituximab infusion. In regard to the clinical course after 24 months, 4 of the 20 patients in the treatment continuation group discontinued the rituximab treatment after the fifth infusion and 2 patients discontinued the treatment after the sixth infusion. However, complete remission was maintained in all the 20 patients of this group during the 12-month observation period after the first four single-dose rituximab infusions. On the other hand, 1 of the 5 patients in the treatment discontinuation group developed relapse during the observation period after the first four rituximab infusions, and the rituximab treatment was resumed. In our trial, rituximab therapy was associated with maintenance of complete remission. Complete remission was maintained even in most of the patients who showed B-cell repletion after discontinuation of rituximab therapy. Thus, rituximab may be considered as a radical therapeutic agent for patients with steroid-dependent MCNS.

Rituximab in adult minimal change disease and focal segmental glomerulosclerosis

Treatment of nephrotic syndrome due to minimal change disease and focal segmental glomerulosclerosis remains a challenge since steroid dependence, steroid resistance and a relapsing disease course exhibits a high cumulative steroid dosage. The necessity of using alternative steroid-sparing immunosuppressive agents with potential toxic side effects also restricts their long-term use. Rituximab, a monoclonal antibody targeting CD20, has been increasingly used in the therapy of difficult-to-treat nephrotic syndrome. A clinical response has been shown for patients with steroid-dependent or frequently relapsing nephrotic syndrome, whereas the benefit seems to be limited in steroid-resistant patients, especially those with underlying focal segmental glomerulosclerosis. No potentially life-threatening adverse events have been observed in the treatment of adult minimal change disease and focal segmental glomerulosclerosis following rituximab administration. Since most reports are retrospective and evidence of efficacy is derived from small case series, more prospective trials in a controlled, randomized manner are highly desirable to delineate the use of rituximab or other B cell-depleting agents in steroid-dependent, frequently relapsing or steroid-resistant patients.

Sphingomyelin phosphodiesterase acid-like 3A (SMPDL3A) is a novel nucleotide phosphodiesterase regulated by cholesterol in human macrophages

Cholesterol-loaded foam cell macrophages are prominent in atherosclerotic lesions and play complex roles in both inflammatory signaling and lipid metabolism, which are underpinned by large scale reprogramming of gene expression. We performed a microarray study of primary human macrophages that showed that transcription of the sphingomyelin phosphodiesterase acid-like 3A (SMPDL3A) gene is up-regulated after cholesterol loading. SMPDL3A protein expression in and secretion from primary macrophages are stimulated by cholesterol loading, liver X receptor ligands, and cyclic AMP, and N-glycosylated SMPDL3A protein is detectable in circulating blood. We demonstrate for the first time that SMPDL3A is a functional phosphodiesterase with an acidic pH optimum. We provide evidence that SMPDL3A is not an acid sphingomyelinase but unexpectedly is active against nucleotide diphosphate and triphosphate substrates at acidic and neutral pH. SMPDL3A is a major source of nucleotide phosphodiesterase activity secreted by liver X receptor-stimulated human macrophages. Extracellular nucleotides such as ATP may activate pro-inflammatory responses in immune cells. Increased expression and secretion of SMPDL3A by cholesterol-loaded macrophage foam cells in lesions may decrease local concentrations of pro-inflammatory nucleotides and potentially represent a novel anti-inflammatory axis linking lipid metabolism with purinergic signaling in atherosclerosis.

Rituximab for childhood-onset, complicated, frequently relapsing nephrotic syndrome or steroid-dependent nephrotic syndrome: a multicentre, double-blind, randomised, placebo-controlled trial

BACKGROUND

Rituximab could be an effective treatment for childhood-onset, complicated, frequently relapsing nephrotic syndrome (FRNS) and steroid-dependent nephrotic syndrome (SDNS). We investigated the efficacy and safety of rituximab in patients with high disease activity.

METHODS

We did a multicentre, double-blind, randomised, placebo-controlled trial at nine centres in Japan. We screened patients aged 2 years or older experiencing a relapse of FRNS or SDNS, which had originally been diagnosed as nephrotic syndrome when aged 1-18 years. Patients with complicated FRNS or SDNS who met all other criteria were eligible for inclusion after remission of the relapse at screening. We used a computer-generated sequence to randomly assign patients (1:1) to receive rituximab (375 mg/m(2)) or placebo once weekly for 4 weeks, with age, institution, treatment history, and the intervals between the previous three relapses as adjustment factors. Patients, guardians, caregivers, physicians, and individuals assessing outcomes were masked to assignments. All patients received standard steroid treatment for the relapse at screening and stopped taking immunosuppressive agents by 169 days after randomisation. Patients were followed up for 1 year. The primary endpoint was the relapse-free period. Safety endpoints were frequency and severity of adverse events. Patients who received their assigned intervention were included in analyses. This trial is registered with the University Hospital Medical Information Network clinical trials registry, number UMIN000001405.

FINDINGS

Patients were centrally registered between Nov 13, 2008, and May 19, 2010. Of 52 patients who underwent randomisation, 48 received the assigned intervention (24 were given rituximab and 24 placebo). The median relapse-free period was significantly longer in the rituximab group (267 days, 95% CI 223-374) than in the placebo group (101 days, 70-155; hazard ratio: 0·27, 0·14-0·53; p<0·0001). Ten patients (42%) in the rituximab group and six (25%) in the placebo group had at least one serious adverse event (p=0·36).

INTERPRETATION

Rituximab is an effective and safe treatment for childhood-onset, complicated FRNS and SDNS.

FUNDING

Japanese Ministry of Health, Labour and Welfare.

Rituximab-cyclophosphamide-dexamethasone is highly effective in patients with monoclonal Ig deposit-related glomerulopathy and indolent non-Hodgkin lymphomas

Indolent non-hodgkin lymphomas (iNHL) are a rare cause of monoclonal immunoglobulin deposits-related glomerulopathy (mIgGN). In patients with iNHL-related mIgGN, whether treatment should include either single or a combination of drug(s) to target the malignant clone and renal inflammation remains elusive. In this retrospective study, we report a cohort of 14 patients with iNHL-related mIgGN (cryoglobulinemic glomerulonephritis [n = 5], membranous nephropathy [n = 3], membranoproliferative glomerulonephritis [n = 3], AL or AL/AH amyloidosis [n = 2], and Light Chain Deposits Disease [n = 1]) and who received a treatment combining rituximab, cyclophosphamide, and dexamethasone (RCD). After a mean follow-up of 18 ± 4 months, nine patients (63%) had complete haematological response. Renal response was observed in 12 of the 14 patients (86%; complete response: n = 9; partial: n = 3). Estimated glomerular filtration rate increased from 47 ± 7 to 63 ± 8 mL/min/1.73 m(2) , and proteinuria decreased from 6.5 ± 0.7 to 1.4 ± 0.8 g/24 hr at one year. Following hematological relapse, renal relapse occurred in two patients suggesting sustained clonal eradication offers the best renal protection. Tolerance of RCD was good and the most frequent adverse event was pneumonia (3/14, 21%). RCD is a promising regimen for patients with iNHL and mIgGN, irrespective of glomerular pathologic pattern. Whether steroids can be avoided or minimized remains to be addressed.

B cells: depletion or functional modulation in rheumatic diseases

PURPOSE OF REVIEW

The availability of drugs directly and indirectly targeting the B cells has refocussed attention on the role of B lymphocytes in rheumatic autoimmune/inflammatory diseases (RAIDs), but their distinct therapeutic potential for certain diseases remains to be further assessed.

RECENT FINDINGS

Although additional drugs are currently in clinical development targeting surface molecules (CD19, CD20, CD22, etc.) and cytokines (IL-6, IL-21, BAFF and APRIL) with key effects on B cell/plasma cell survival and differentiation, respectively, recent studies have also provided further insights into the effects of currently available drugs on protective immunity and mechanisms of the initiation and progression of RAIDs (i.e. rituximab, belimumab, mycophenolate and azathioprine). A key aspect of B-cell-directed drugs is their impact on continuous immune activation and chronic maintenance which may differ between individual RAIDs.

SUMMARY

The translational advances in the area of B-cell-depleting therapies and more sophisticated approaches to modulate key B-cell functions, such as blocking B-cell receptor downstream effects, interfering with the differentiation and survival of antigen-experienced memory B and plasma cells are of central interest. Differences in the efficacy and safety profiles of B-cell depletion compared with B-cell-modulating therapies (including antigen-specific tolerance induction) need to be further delineated.

Focal segmental glomerulosclerosis recurrence in the renal allograft

Focal segmental glomerulosclerosis (FSGS) represents a common histologic pattern of glomerular injury associated with a multitude of disease mechanisms. The etiology of FSGS is often classified into primary (idiopathic) and secondary forms in response to genetic abnormalities, infections, toxins, and systemic disorders that lead to adaptive changes, glomerular hyperfiltration, and proteinuria. Our understanding of the pathogenic mechanisms responsible for FSGS was substantially enhanced in recent years because of major advances in the cell biology of the podocyte and parietal epithelial cell. Recurrence of FSGS occurs mainly in its primary form and is only rarely described in secondary forms. The re-enactment of pathologic mechanisms of FSGS as recurrent disease after kidney transplantation represents a biologic experiment that can provide unique insight. Nonetheless, recurrent FSGS remains a notable clinical problem that correlates with poorer renal allograft outcomes. This is the focus of this particular review, concentrating on the most recent developments.

Refractory focal segmental glomerulosclerosis in the adult: complete and sustained remissions of two episodes of nephrotic syndrome after a single dose of rituximab

Rituximab therapy may achieve remission of proteinuria in children or adolescents with refractory focal segmental glomerulosclerosis (FSGS), but its effectiveness in adults is uncertain. We describe the case of a 22-year-old Caucasian woman with refractory FSGS that achieved complete and sustained remission of nephrotic syndrome (NS) with one single 375 mg/m(2) rituximab infusion. At 4 months after complete circulating B-cell depletion, proteinuria declined from 4.5 to 0.27 g/24 h and serum albumin normalised. Rituximab was well tolerated and allowed complete withdrawal of previous immunosuppression with steroids and azathioprine. The patient was in sustained remission up to month 32, when she experienced a relapse. A second infusion of rituximab (375 mg/m(2)) achieved prompt proteinuria reduction with no additional immunosuppressants. At 48 months after the initial treatment, this patient is in complete remission without any immunosuppression. This case suggests that rituximab, even a single dose, may safely promote NS remission in adults with refractory FSGS.

Identification and biochemical characterization of an acid sphingomyelinase-like protein from the bacterial plant pathogen Ralstonia solanacearum that hydrolyzes ATP to AMP but not sphingomyelin to ceramide

Acid sphingomyelinase (aSMase) is a human enzyme that catalyzes the hydrolysis of sphingomyelin to generate the bioactive lipid ceramide and phosphocholine. ASMase deficiency is the underlying cause of the genetic diseases Niemann-Pick Type A and B and has been implicated in the onset and progression of a number of other human diseases including cancer, depression, liver, and cardiovascular disease. ASMase is the founding member of the aSMase protein superfamily, which is a subset of the metallophosphatase (MPP) superfamily. To date, MPPs that share sequence homology with aSMase, termed aSMase-like proteins, have been annotated and presumed to function as aSMases. However, none of these aSMase-like proteins have been biochemically characterized to verify this. Here we identify RsASML, previously annotated as RSp1609: acid sphingomyelinase-like phosphodiesterase, as the first bacterial aSMase-like protein from the deadly plant pathogen Ralstonia solanacearum based on sequence homology with the catalytic and C-terminal domains of human aSMase. A biochemical characterization of RsASML does not support a role in sphingomyelin hydrolysis but rather finds RsASML capable of acting as an ATP diphosphohydrolase, catalyzing the hydrolysis of ATP and ADP to AMP. In addition, RsASML displays a neutral, not acidic, pH optimum and prefers Ni²⁺ or Mn²⁺, not Zn²⁺, for catalysis. This alters the expectation that all aSMase-like proteins function as acid SMases and expands the substrate possibilities of this protein superfamily to include nucleotides. Overall, we conclude that sequence homology with human aSMase is not sufficient to predict substrate specificity, pH optimum for catalysis, or metal dependence. This may have implications to the biochemically uncharacterized human aSMase paralogs, aSMase-like 3a (aSML3a) and aSML3b, which have been implicated in cancer and kidney disease, respectively, and assumed to function as aSMases.

Is rituximab effective in childhood nephrotic syndrome? Yes and no

The idiopathic nephrotic syndrome (i.e. MCNS and FSGS) in children has been regarded as a disorder of T-cell function. Recent studies, however, also describe abnormalities of B-cell function. This supports the use of B-cell modulating treatment for idiopathic nephrotic syndrome (INS), especially rituximab, which has been used in other glomerular disorders as well. Many studies indicate that rituximab is effective in steroid-sensitive and -dependent nephrotic syndrome, by either inducing long-term remission or reducing relapses. In most series, children with primary (and recurrent) focal segmental glomerulosclerosis (FSGS) do not respond as well. The exact mechanisms of action of rituximab (as well as those of the other treatment options) in INS are as yet unclear. In addition to hosting mechanisms a direct stabilizing effect on the podocyte may also be of relevance, especially in FSGS. Although results are encouraging especially in steroid-sensitive patients, further studies on the clinical use of rituximab and the short- and long-term immunological effects and side-effects are necessary.

Rituximab in idiopathic nephrotic syndrome: does it make sense?

Idiopathic nephrotic syndrome (INS) includes three different entities: minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), and mesangial proliferative glomerulonephritis. Historically, this condition has been attributed to a T-cell disorder resulting in the secretion of a circulating factor that increases glomerular permeability to plasma proteins. The therapeutic approach to control the proteinuria of INS remains the use of drugs that have been considered to suppress the production of the "circulating factor" secreted by T cells. Recently, rituximab (RTX), a chimeric monoclonal antibody directed against the CD20 cell surface receptor expressed on B cells, has emerged as potential therapeutic agent. The number of publications reporting clinical experience with RTX in the treatment of nephrotic syndrome has greatly increased in the last few years. However, there is currently no good evidence from clinical or experimental studies that support a role of RTX in the treatment of MCD and FSGS proteinuria. In summary, there is the need for a better understanding of the pathogenesis of the proteinuria in INS and the potential role of RTX in this condition.

Rituximab treatment combined with methylprednisolone pulse therapy and immunosuppressants for childhood steroid-resistant nephrotic syndrome

BACKGROUND

Calcineurin inhibitors (CIs) with/without intravenous methylprednisolone pulse therapy (MPT) constitute the standard treatment for childhood-onset, steroid-resistant nephrotic syndrome (SRNS). However, some patients fail to achieve remission. We treated SRNS patients resistant to CIs and MPT with additional rituximab combined with MPT and immunosuppressive agents.

METHODS

Ten patients (aged 2-14 years) with CI- and MPT-resistant SRNS were enrolled. Patients were administered rituximab (1-4 doses; 375 mg/m(2)) followed by MPT (30 mg/kg/day of methylprednisolone for 3 consecutive days) once every 2-4 weeks until complete remission (CR). We analyzed clinical outcome and safety.

RESULTS

Six patients received a single dose of rituximab, 2 received two doses, and 2 received four doses. Seven patients achieved CR, 1 achieved partial remission, and 2 showed no response. Although 2 patients with no response progressed to end-stage renal failure, 7 patients with CR preserved normal renal function without proteinuria at the last observation. There were two serious adverse events.

CONCLUSIONS

Additional rituximab combined with conventional MPT and immunosuppressive agents is a promising option for overcoming refractory SRNS. Aggressive B cell suppression by rituximab may ameliorate resistance to conventional treatments and a cocktail of other immunosuppressive agents, such as CIs, MMF, mizoribine, may be beneficial. However, as intense immunosuppression may cause serious adverse events, further evaluation is necessary.

Effects of pretransplant plasmapheresis and rituximab on recurrence of focal segmental glomerulosclerosis in adult renal transplant recipients

BACKGROUND/AIMS

Recurrent focal segmental glomerulosclerosis (FSGS) following renal transplantation is relatively common. However, the risk factors and optimal pretransplant treatment preventing recurrence of FSGS remain controversial.

METHODS

We retrospectively reviewed 27 adult renal transplant recipients with FSGS over a period of 10 years. We first compared possible risk factors for FSGS recurrence between the recurrence and nonrecurrence groups. Then we evaluated the effect of pretransplant plasmapheresis (PP; n = 4) and PP with rituximab (PP + RTX; n = 5) on recurrence of FSGS after transplantation compared to control patients that were not treated with these modalities.

RESULTS

There were seven recurrences in 27 patients (25.9%), but there were no significant differences in possible risk factors for FSGS recurrence between the two groups. Recurrence rates between patients with pretransplant PP or PP + RTX and control patients were not significantly different (22.2% vs. 27.7%, p > 0.05). There was also no significant difference in recurrence between the pretransplant PP and PP + RTX groups (25% vs. 20%, p > 0.05).

CONCLUSIONS

Pretransplant PP or PP + RTX do not significantly decrease the recurrence of FSGS in adult renal transplant candidates.

Sphingomyelinase-like phosphodiesterase 3b expression levels determine podocyte injury phenotypes in glomerular disease

Diabetic kidney disease (DKD) is the most common cause of ESRD in the United States. Podocyte injury is an important feature of DKD that is likely to be caused by circulating factors other than glucose. Soluble urokinase plasminogen activator receptor (suPAR) is a circulating factor found to be elevated in the serum of patients with FSGS and causes podocyte αVβ3 integrin-dependent migration in vitro. Furthermore, αVβ3 integrin activation occurs in association with decreased podocyte-specific expression of acid sphingomyelinase-like phosphodiesterase 3b (SMPDL3b) in kidney biopsy specimens from patients with FSGS. However, whether suPAR-dependent αVβ3 integrin activation occurs in diseases other than FSGS and whether there is a direct link between circulating suPAR levels and SMPDL3b expression in podocytes remain to be established. Our data indicate that serum suPAR levels are also elevated in patients with DKD. However, unlike in FSGS, SMPDL3b expression was increased in glomeruli from patients with DKD and DKD sera-treated human podocytes, where it prevented αVβ3 integrin activation by its interaction with suPAR and led to increased RhoA activity, rendering podocytes more susceptible to apoptosis. In vivo, inhibition of acid sphingomyelinase reduced proteinuria in experimental DKD but not FSGS, indicating that SMPDL3b expression levels determined the podocyte injury phenotype. These observations suggest that SMPDL3b may be an important modulator of podocyte function by shifting suPAR-mediated podocyte injury from a migratory phenotype to an apoptotic phenotype and that it represents a novel therapeutic glomerular disease target.

Lipid biology of the podocyte--new perspectives offer new opportunities

In the past 15 years, major advances have been made in understanding the role of lipids in podocyte biology. First, susceptibility to focal segmental glomerulosclerosis (FSGS) and glomerular disease is associated with an APOL1 sequence variant, is expressed in podocytes and encodes apolipoprotein L1, an important component of HDL. Second, acid sphingomyelinase-like phosphodiesterase 3b encoded by SMPDL3b has a role in the conversion of sphingomyelin to ceramide and its levels are reduced in renal biopsy samples from patients with recurrent FSGS. Furthermore, decreased SMPDL3b expression is associated with increased susceptibility of podocytes to injury after exposure to sera from these patients. Third, in many individuals with membranous nephropathy, autoantibodies against the phospholipase A2 (PLA2) receptor, which is expressed in podocytes, have been identified. Whether these autoantibodies affect the activity of PLA2, which liberates arachidonic acid from glycerophospholipids and modulates podocyte function, is unknown. Fourth, clinical and experimental evidence support a role for ATP-binding cassette sub-family A member 1-dependent cholesterol efflux, free fatty acids and glycerophospolipids in the pathogenesis of diabetic kidney disease. An improved understanding of lipid biology in podocytes might provide insights to develop therapeutic targets for primary and secondary glomerulopathies.

Is there B cell involvement in a rat model of spontaneous idiopathic nephrotic syndrome treated with LF15-0195?

BACKGROUND

The Buffalo/Mna (Buff/Mna) rat spontaneously develops idiopathic nephrotic syndrome (INS), and its nephropathy recurs after the renal transplantation of a healthy graft. Only LF15-0195 is able to cause regression of the Buff/Mna nephropathy and to induce regulatory T cells, which decrease proteinuria when transferred into proteinuric Buff/Mna rats. Based on previous research on B cells in human INS, we evaluated the involvement of B cells in our model and the impact of LF15-0195.

METHODS

We studied the effect of LF15-0195 on peripheral B cells by flow cytometry and quantitative reverse transcription-polymerase chain reaction. B cells were purified from LF15-0195-treated Buff/Mna rats in remission, and transferred into proteinuric Buff/Mna rats. We treated the Buff/Mna rats with mitoxantrone and measured the depletion of B/T cells in parallel with proteinuria.

RESULTS

LF15-0195 changed the phenotype of B cells: the number of naïve mature B cells increased significantly, while the number of switched, transitional 1, and transitional 2 B cells decreased. There were no changes in the amount of memory, activated or regulatory B cells. We observed a significant increase of immunoglobulin (Ig)M mRNA transcripts in the LF15-0195-treated Buff/Mna B cells compared to controls, but no difference in the level of IgG. This profile is consistent with a block in B cell maturation at the IgM to IgG switch. The transfer of B cells from LF15-0195-treated rats into proteinuric Buff/Mna rats did not have an effect on proteinuria. Mitoxantrone, despite causing a significant depletion of B cells, did not reduce proteinuria.

CONCLUSION

Despite LF15-0195 acting on B cells, the beneficial effects of this drug on nephrotic syndrome did not involve the induction of regulatory B cells. Moreover, the B cell depletion was not effective in reducing proteinuria, indicating that B cells are not a therapeutic target.

Successful treatment of recurrent focal segmental glomerulosclerosis with a low dose rituximab in a kidney transplant recipient

Recurrence of focal segmental glomerulosclerosis (FSGS) is a major therapeutic challenge in kidney transplantation (KT). Although intensive plasmapheresis and high-dose rituximab have been introduced to treat recurrent FSGS, the most effective dosage and regimen of rituximab have not been determined. Herein we reported the first case of successful treatment of recurrent FSGS with a low-dose rituximab. The patient showed marked proteinuria (3.5 g/d) and oliguria 2 d after KT. Two courses of plasmapheresis and immunoglobulin were applied to the patient, however, nephrotic range proteinuria persisted and creatinine level increased to 3.56 mg/dL. Five months post-transplant, the patient received injection with only one dose of rituximab 100 mg, without further plasmapheresis, which resulted in immediate reduction of serum creatinine and full remission of proteinuria during the following 18 months. This case suggested that recurrent FSGS, which frequently relapses after plasmapheresis, could be treated successfully with a low-dose rituximab even without plasmapheresis.

Rituximab in steroid-dependent or frequently relapsing idiopathic nephrotic syndrome

The outcome of steroid-dependent or frequently relapsing nephrotic syndrome of minimal change disease (MCD), mesangial proliferative GN (MesGN), or FSGS may be poor and with major treatment toxicity. This academic, multicenter, off-on trial (ClinicalTrials.gov #NCT00981838) primarily evaluated the effects of rituximab therapy followed by immunosuppression withdrawal on disease recurrence in 10 children and 20 adults with MCD/MesGN (n=22) or FSGS who had suffered ≥2 recurrences over the previous year and were in steroid-induced remission for ≥1 month. Participants received one dose (n=28) or two doses of rituximab (375 mg/m(2) intravenously). At 1 year, all patients were in remission: 18 were treatment-free and 15 never relapsed. Compared with the year before rituximab treatment, total relapses decreased from 88 to 22 and the per-patient median number of relapses decreased from 2.5 (interquartile range [IQR], 2-4) to 0.5 (IQR, 0-1; P<0.001) during 1 year of follow-up. Reduction was significant across subgroups (children, adults, MCD/MesGN, and FSGS; P<0.01). After rituximab, the per-patient steroid maintenance median dose decreased from 0.27 mg/kg (IQR, 0.19-0.60) to 0 mg/kg (IQR, 0-0.23) (P<0.001), and the median cumulative dose to achieve relapse remission decreased from 19.5 mg/kg (IQR, 13.0-29.2) to 0.5 mg/kg (IQR, 0-9.4) (P<0.001). Furthermore, the mean estimated GFR increased from 111.3±25.7 to 121.8±29.2 ml/min per 1.73 m(2) (P=0.01), with the largest increases in children and in FSGS subgroups. The mean height z score slope stabilized in children (P<0.01). Treatment was well tolerated. Rituximab effectively and safely prevented recurrences and reduced the need for immunosuppression in steroid-dependent or frequently relapsing nephrotic syndrome, and halted disease-associated growth deficit in children.

Rituximab treatment prevents the early development of proteinuria following pig-to-baboon xeno-kidney transplantation

We previously reported life-supporting α1,3-galactosyltransferase knockout (GalTKO) thymokidney xenograft survival of >2 months in baboons. However, despite otherwise normal renal function, recipients developed proteinuria with morphologic changes (podocyte effacement), a condition that presents a major obstacle to long-term studies in this model. A recent clinical study showed that rituximab therapy after allogeneic transplant prevented proteinuria possibly associated with loss of sphingomyelin phosphodiesterase acid-like 3b (SMPDL-3b). Here, we demonstrate that rituximab prevents the disruption of pig podocytes in an SMPDL-3b-dependent manner in vitro and the early development of proteinuria after xenogeneic kidney transplantation in baboons. Immunofluorescence showed SMPDL-3b expression in pig glomerular epithelium; immunoprecipitation demonstrated rituximab binding to SMPDL-3b in glomeruli. Culture of isolated pig podocytes with naive baboon sera, which has preformed antipig natural antibodies, reduced SMPDL-3b expression, disrupted podocyte morphology, and decreased podocyte proliferation, whereas pretreatment with rituximab prevented these effects. Six baboons received rituximab before transplantation to deplete B cells and again in the peri-transplant period; 18 baboons treated only before transplantation served as historical controls. The onset of post-transplant proteinuria was significantly delayed in a B cell-independent manner in the animals that received peri-transplant rituximab treatment. Although further optimization of this protocol is required, these data provide intriguing clues to the mechanisms of post-transplant proteinuria in xenogeneic kidney transplantation and a potential strategy for its prevention.

Immunopathogenesis of idiopathic nephrotic syndrome with relapse

Idiopathic change nephrotic syndrome (INS), the most frequent glomerular disease in children and young adults, is characterized by heavy proteinuria and a relapsing remitting course. Although the mechanisms underlying the pathophysiology of proteinuria remain unclear, clinical and experimental observations suggest that lymphocyte and podocyte disturbances are two sides of the disease. The current hypothesis suggests that immune cells release a putative factor, which alters podocyte function resulting in nephrotic proteinuria. Besides T-cell abnormalities, recent evidence of B-cell depletion efficacy in sustained remissions added a new challenge in understanding the immunological mechanisms of INS. In this review, we discuss recent insights related to podocyte disorders occurring in INS and their relevance in human diseases.

Actin-associated Proteins in the Pathogenesis of Podocyte Injury

Podocytes have a complex cellular architecture with interdigitating processes maintained by a precise organization of actin filaments. The actin-based foot processes of podocytes and the interposed slit diaphragm form the final barrier to proteinuria. The function of podocytes is largely based on the maintenance of the normal foot process structure with actin cytoskeleton. Cytoskeletal dynamics play important roles during normal podocyte development, in maintenance of the healthy glomerular filtration barrier, and in the pathogenesis of glomerular diseases. In this review, we focused on recent findings on the mechanisms of organization and reorganization of these actin-related molecules in the pathogenesis of podocyte injury and potential therapeutics targeting the regulation of actin cytoskeleton in podocytopathies.

Issues in solid-organ transplantation in children: translational research from bench to bedside

In this review, we identify important challenges facing physicians responsible for renal and cardiac transplantation in children based on a review of the contemporary medical literature. Regarding pediatric renal transplantation, we discuss the challenge of antibody-mediated rejection, focusing on both acute and chronic antibody-mediated rejection. We review new diagnostic approaches to antibody-mediated rejection, such as panel-reactive antibodies, donor-specific cross-matching, antibody assays, risk assessment and diagnosis of antibody-mediated rejection, the pathology of antibody-mediated rejection, the issue of ABO incompatibility in renal transplantation, new therapies for antibody-mediated rejection, inhibiting of residual antibodies, the suppression or depletion of B-cells, genetic approaches to treating acute antibody-mediated rejection, and identifying future translational research directions in kidney transplantation in children. Regarding pediatric cardiac transplantation, we discuss the mechanisms of cardiac transplant rejection, including the role of endomyocardial biopsy in detecting graft rejection and the role of biomarkers in detecting cardiac graft rejection, including biomarkers of inflammation, cardiomyocyte injury, or stress. We review cardiac allograft vasculopathy. We also address the role of genetic analyses, including genome-wide association studies, gene expression profiling using entities such as AlloMap®, and adenosine triphosphate release as a measure of immune function using the Cylex® ImmuKnow™ cell function assay. Finally, we identify future translational research directions in heart transplantation in children.

Podocyte pathology and nephropathy - sphingolipids in glomerular diseases

Sphingolipids are components of the lipid rafts in plasma membranes, which are important for proper function of podocytes, a key element of the glomerular filtration barrier. Research revealed an essential role of sphingolipids and sphingolipid metabolites in glomerular disorders of genetic and non-genetic origin. The discovery that glucocerebrosides accumulate in Gaucher disease in glomerular cells and are associated with clinical proteinuria initiated intensive research into the function of other sphingolipids in glomerular disorders. The accumulation of sphingolipids in other genetic diseases including Tay-Sachs, Sandhoff, Fabry, hereditary inclusion body myopathy 2, Niemann-Pick, and nephrotic syndrome of the Finnish type and its implications with respect to glomerular pathology will be discussed. Similarly, sphingolipid accumulation occurs in glomerular diseases of non-genetic origin including diabetic kidney disease (DKD), HIV-associated nephropathy, focal segmental glomerulosclerosis (FSGS), and lupus nephritis. Sphingomyelin metabolites, such as ceramide, sphingosine, and sphingosine-1-phosphate have also gained tremendous interest. We recently described that sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) is expressed in podocytes where it modulates acid sphingomyelinase activity and acts as a master modulator of danger signaling. Decreased SMPDL3b expression in post-reperfusion kidney biopsies from transplant recipients with idiopathic FSGS correlates with the recurrence of proteinuria in patients and in experimental models of xenotransplantation. Increased SMPDL3b expression is associated with DKD. The consequences of differential SMPDL3b expression in podocytes in these diseases with respect to their pathogenesis will be discussed. Finally, the role of sphingolipids in the formation of lipid rafts in podocytes and their contribution to the maintenance of a functional slit diaphragm in the glomerulus will be discussed.

Rituximab treatment for relapsing minimal change disease and focal segmental glomerulosclerosis: a systematic review

BACKGROUND

Minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) remain a therapeutic challenge, since steroids and other immunosuppressive agents exhibit an unfavorable adverse event spectrum. The aim of this review was to systematically summarize and analyze data from preexisting studies reporting the outcome of rituximab (RTX) treatment in these patients.

METHODS

Study data on adult patients with either steroid-dependent or frequently relapsing MCD/FSGS were identified by a PubMed and Embase search. The number of relapses was calculated and the use of immunosuppressive co-medication prior to and after RTX treatment was quantified.

RESULTS

We identified 14 studies including 86 patients with frequently relapsing and steroid-dependent MCD or FSGS. Treatment with RTX reduced the number of relapses per year from 1.3 (0-9) relapses prior to treatment compared to 0 (0-2) after therapy (p < 0.001). Proteinuria decreased from 2.43 (0-15) g/day to 0 (0-4.89) g/day (p < 0.001), while serum albumin increased from 2.9 (1.2-4.6) at baseline to 4.0 (1.8-5.09) g/l after RTX (p = 0.001). The use of immunosuppression used at the time of RTX administration was also reduced after RTX therapy (p < 0.001). Baseline serum albumin was lower (p = 0.018), whereas the number of immunosuppressants prior to RTX was higher (p = 0.018) in patients with relapse after RTX.

CONCLUSIONS

The published data suggest that RTX is effective in reducing the number of relapses and sparing immunosuppression in frequently relapsing and steroid-dependent nephrotic syndrome due to MCD and FSGS. These promising findings have to be confirmed in controlled and prospective studies.

Podocyte effacement closely links to suPAR levels at time of posttransplantation focal segmental glomerulosclerosis occurrence and improves with therapy

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) recurs after kidney transplantation in more than 30% of cases and can lead to allograft loss. Serum soluble urokinase-type plasminogen activator receptor (suPAR) is implicated in the pathogenesis of native and recurrent FSGS.

METHODS

We conducted a retrospective study of 25 adults with posttransplantation FSGS. We investigated the relationship between suPAR levels and podocyte changes and the impact of therapy on podocyte structure. We assessed response to therapy by improvement in proteinuria, allograft function, and resolution of histologic changes.

RESULTS

A median (interquartile range) of 15 (10-23) plasmapheresis sessions was administered; 13 of the subjects also received rituximab. Median pretreatment suPAR levels were higher among those with severe (≥75%) versus those with mild (≤25%) podocyte foot process effacement (13,030 vs. 4806 pg/mL; P=0.02). Overall, mean±SD of proteinuria improved from 5.1±3.8 to 2.1±2.8 mg/dL (P=0.003), mean podocyte effacement decreased from 57%±33% to 22%±22% (P=0.0001), estimated glomerular filtration rates increased from median (interquartile range) of 32.9 (20.6-44.2) to 39.3 (28.8-63.4; P<0.0001), and suPAR levels decreased from a median of 6.781 to 4.129 pg/mL (P=0.02) with therapy.

CONCLUSIONS

Podocyte effacement is the first pathologic manifestation of FSGS after transplantation. The degree of podocyte effacement correlates with suPAR levels at time of diagnosis. Response to therapy results in significant reduction of suPAR levels and complete or significant improvement of podocyte effacement.

Primary focal and segmental glomerulosclerosis and soluble factor urokinase-type plasminogen activator receptor

Primary focal and segmental glomerulosclerosis (FSGS) may be due to genetic or acquired etiologies and is a common cause of nephrotic syndrome with high morbidity that often leads to end-stage renal failure. The different available therapeutic approaches are unsuccessful, in part due to partially deciphered heterogeneous and complex pathophysiological mechanisms. Moreover, the term FSGS, even in its primary form, comprises a histological description shared by a number of different causes with completely different molecular pathways of disease. This review focuses on the latest developments regarding the pathophysiology of primary acquired FSGS caused by soluble factor urokinase type plasminogen activator receptor, a circulating permeability factor involved in proteinuria and edema formation, and describes recent advances with potential success in therapy.

B-cell-targeted therapy in adult glomerulonephritis

INTRODUCTION

There are many mechanisms through which B lymphocytes have been implicated in the pathogenesis of glomerulonephritis. There are a number of trials and clinical studies in glomerulonephritis involving depletion of CD20(+) B lymphocytes using rituximab. Newer anti-CD20 agents are currently under evaluation, as are drugs targeting alternative B-cell targets such as B lymphocyte stimulator. Such selective, targeted B-cell therapies, if shown to be effective, may be of value in minimising toxicity from more conventional agents.

AREAS COVERED

This article reviews the role of B cells as a target for therapy in adult renal disease resulting from primary glomerulonephritis and that occurring secondary to systemic disease. It will not address intracellular signalling or co-stimulatory pathways as therapeutic targets.

EXPERT OPINION

There are indications for B-cell targeted therapies in a number of adult glomerulonephritides, with varying degrees of evidence. Further understanding of the mechanisms of B-cell depletion and repletion, and interplay with B-cell survival factors, is necessary in order to identify patients who will respond favourably.

Targeting therapeutics to the glomerulus with nanoparticles

Nanoparticles are an enabling technology for the creation of tissue-/cell-specific therapeutics that have been investigated extensively as targeted therapeutics for cancer. The kidney, specifically the glomerulus, is another accessible site for nanoparticle delivery that has been relatively overlooked as a target organ. Given the medical need for the development of more potent, kidney-targeted therapies, the use of nanoparticle-based therapeutics may be one such solution to this problem. Here, we review the literature on nanoparticle targeting of the glomerulus. Specifically, we provide a broad overview of nanoparticle-based therapeutics and how the unique structural characteristics of the glomerulus allow for selective, nanoparticle targeting of this area of the kidney. We then summarize literature examples of nanoparticle delivery to the glomerulus and elaborate on the appropriate nanoparticle design criteria for glomerular targeting. Finally, we discuss the behavior of nanoparticles in animal models of diseased glomeruli and review examples of nanoparticle therapeutic approaches that have shown promise in animal models of glomerulonephritic disease.

Cyclodextrin protects podocytes in diabetic kidney disease

Diabetic kidney disease (DKD) remains the most common cause of end-stage kidney disease despite multifactorial intervention. We demonstrated that increased cholesterol in association with downregulation of ATP-binding cassette transporter ABCA1 occurs in normal human podocytes exposed to the sera of patients with type 1 diabetes and albuminuria (DKD(+)) when compared with diabetic patients with normoalbuminuria (DKD(-)) and similar duration of diabetes and lipid profile. Glomerular downregulation of ABCA1 was confirmed in biopsies from patients with early DKD (n = 70) when compared with normal living donors (n = 32). Induction of cholesterol efflux with cyclodextrin (CD) but not inhibition of cholesterol synthesis with simvastatin prevented podocyte injury observed in vitro after exposure to patient sera. Subcutaneous administration of CD to diabetic BTBR (black and tan, brachiuric) ob/ob mice was safe and reduced albuminuria, mesangial expansion, kidney weight, and cortical cholesterol content. This was followed by an improvement of fasting insulin, blood glucose, body weight, and glucose tolerance in vivo and improved glucose-stimulated insulin release in human islets in vitro. Our data suggest that impaired reverse cholesterol transport characterizes clinical and experimental DKD and negatively influences podocyte function. Treatment with CD is safe and effective in preserving podocyte function in vitro and in vivo and may improve the metabolic control of diabetes.

Comparative transcriptional profiling of 3 murine models of SLE nephritis reveals both unique and shared regulatory networks

Objective

To define shared and unique features of SLE nephritis in mouse models of proliferative and glomerulosclerotic renal disease.

Methods

Perfused kidneys from NZB/W F1, NZW/BXSB and NZM2410 mice were harvested before and after nephritis onset. Affymetrix based gene expression profiles of kidney RNA were analyzed using Genomatix Pathway Systems and Ingenuity Pathway Analysis software. Gene expression patterns were confirmed using real-time PCR.

Results

955, 1168 and 755 genes were regulated in the kidneys of nephritic NZB/W F1, NZM2410 and NZW/BXSB mice respectively. 263 genes were regulated concordantly in all three strains reflecting immune cell infiltration, endothelial cell activation, complement activation, cytokine signaling, tissue remodeling and hypoxia. STAT3 was the top associated transcription factor, having a binding site in the gene promoter of 60/263 regulated genes. The two strains with proliferative nephritis shared a macrophage/DC infiltration and activation signature. NZB/W and NZM2410 mice shared a mitochondrial dysfunction signature. Dominant T cell and plasma cell signatures in NZB/W mice reflected lymphoid aggregates; this was the only strain with regulatory T cell infiltrates. NZW/BXSB mice manifested tubular regeneration and NZM2410 mice had the most metabolic stress and manifested loss of nephrin, indicating podocyte loss.

Conclusions

These findings identify shared inflammatory mechanisms of SLE nephritis that can be therapeutically targeted. Nevertheless, the heterogeneity of effector mechanisms suggests that individualized therapy might need to be based on biopsy findings. Some common mechanisms are shared with non-immune–mediated renal diseases, suggesting that strategies to prevent tissue hypoxia and remodeling may be useful in SLE nephritis.

Immunosuppressive drug therapy

The first successful kidney transplantation between monozygotic identical twins did not require any immunosuppressive drugs. Clinical application of azathioprine and glucocorticosteroids allowed the transfer of organs between genetically disparate donors and recipients. Transplantation is now the standard of care, a life-saving procedure for patients with failed organs. Progress in our understanding of the immunobiology of rejection has been translated to the development of immunosuppressive agents targeting T cells, B cells, plasma cells, costimulatory signals, complement products, and antidonor antibodies. Modern immunopharmacologic interventions have contributed to the clinical success observed following transplantation but challenges remain in personalizing immunosuppressive therapy.

Glomerular diseases: FSGS

FSGS is a lesion, not a disease. The separation into primary FSGS (a result of immunologic-mediated injury) versus secondary FSGS (related to a variety of causes) is often difficult. Even when this particular issue is carefully evaluated, the therapeutic implications are not always apparent. Newer literature on both biomarker discovery and on the genetic basis of FSGS is reviewed in this context. In addition, the thorny implications of obesity as it relates to the FSGS lesion are discussed. An overall practical algorithmic approach to the management and treatment of the FSGS lesion that integrates these controversial overlap areas is suggested.

Therapy of relapsing minimal-change disease in adults: a new approach?

Multiple-relapsing minimal-change disease (MCD) often requires exposure to potentially toxic agents in an attempt to achieve a lasting remission of nephrotic syndrome. Munyentwali and co-workers describe an experience using rituximab in adults with multiple-relapsing MCD that supports both efficacy and safety of this agent. However, the optimal dosing regimen and mechanism of action remain unclear. Thus, randomized controlled trials are warranted in both adults and children to better define the role of rituximab in multiple-relapsing MCD.

Recurrence of glomerulonephritis after renal transplantation

Recurrence of glomerulonephritis following renal transplantation is considered an important cause of allograft failure. The incidence of recurrence of glomerulonephritis varies widely depending on the definition of recurrence (pathologic recurrence or clinicopathologic recurrence) and the original glomerular disease. Moreover the impact of recurrence of glomerular disease on allograft outcome varies widely between different forms of glomerulonephritis. Whereas IgA nephritis recurs in up to one third of transplanted patients, this is not associated with adverse effects on graft survival. In contrast, recurrent focal segmental glomerulosclerosis and membranoproliferative glomerulopathy have an unfavorable prognosis. Overall, long-term graft survival in patients transplanted for glomerulonephritis is comparable to survival in patients with other causes of ESRD. In recent years, several mechanisms for recurrent disease after transplantation (e.g. PLA2R antibodies in membranous nephropathy and suPAR in FSGS) have been identified, and these findings have helped to elucidate the pathogenesis of glomerular diseases. Although renal transplantation is the treatment of choice for end-stage renal disease as a consequence of glomerulonephritis, further studies are required to develop optimal strategies to prevent, diagnose and treat recurrent glomerular diseases.

Current and emerging treatments for idiopathic focal and segmental glomerulosclerosis in adults

Idiopathic focal and segmental glomerular sclerosis is a frequent cause of nephrotic syndrome and end-stage renal disease. The pathogenesis is still unknown, although the body of evidence suggests that focal and segmental glomerular sclerosis is caused by a not clearly identified circulating factor that alters the permselectivity of the glomerular barrier. Proteinuria is followed by podocyte injury. Glucocorticoids, calcineurin inhibitors, cytotoxic agents and mycophenolate mofetil, either given alone or in combination, may obtain complete or partial remission of proteinuria in 50-60% of patients and protect them from end-stage renal disease, but the remaining patients are resistant to the available drugs. A number of new drugs, including rituximab, galactose and antifibrotic agents, are under investigation.

Rituximab is a safe and effective long-term treatment for children with steroid and calcineurin inhibitor-dependent idiopathic nephrotic syndrome

In children with idiopathic nephrotic syndrome, rituximab can maintain short-term remission with withdrawal of prednisone and calcineurin inhibitors. Long-term effects including the number of repeated infusions to maintain remission are unknown. To test this, we treated 46 consecutive children with idiopathic nephrotic syndrome lasting for at least 1 year (mean 6.3 years), maintained in remission with oral prednisone and calcineurin inhibitors. They received 1-5 rituximab courses during a median follow-up of 3 years. Oral agents were tapered after each infusion, and completely withdrawn within 45 days. Rituximab was well tolerated. Six-month probabilities of remission were 48% after the first infusion and 37% after subsequent infusions. One- and 2-year-remission probabilities were, respectively, 20 and 10%. Median time intervals between complete oral-agent withdrawal and relapse were 5.6 and 8.5 months, respectively, following the first and subsequent courses. The time to reconstitution of CD20 cells correlated with the duration of remission, but was not associated with variation in FcyR, CD20, or SMPDL-3B polymorphisms. Podocyte Src phosphorylation was normal. Thus, rituximab can be safely and repeatedly used as a prednisone and calcineurin inhibitor-sparing therapy in a considerable proportion of children with dependent forms of idiopathic nephrotic syndrome. Further study is needed to identify patients who will benefit most from rituximab therapy.

Successful management of factor IX inhibitor-associated nephrotic syndrome in a hemophilia B patient

BACKGROUND

Nephrotic syndrome (NS) is a recognized complication of immune tolerance induction (ITI) therapy, a treatment strategy used to treat inhibitors in patients with hemophilia B receiving factor IX concentrate.

CASE DIAGNOSIS/TREATMENT

We present a 4-year-old boy with hemophilia B and an inhibitor who underwent ITI, and developed NS 19 months into this therapy. A percutaneous renal biopsy was safely performed with factor IX (FIX) concentrate administration both preceding and following the procedure. The patient's inhibitor level had increased to 1.4-1.6 Bethesda Units just prior to the onset of proteinuria. Histology confirmed segmental membranous nephropathy (MGN). The patient was continued on FIX concentrate as ITI and also received 4 weekly doses of rituximab and ongoing immunosuppression with mycophenolate mofetil. This resulted in the complete resolution of his inhibitor and his NS. He continues with a modified ITI regimen and remains inhibitor-free without proteinuria >12 months post-biopsy.

CONCLUSIONS

Hemophilia B patients undergoing ITI should be regularly screened for NS. At first detection of proteinuria, with proper precautions, a percutaneous kidney biopsy can be performed safely in patients with low levels of inhibitor. Our patient had segmental MGN with complete remission of NS.

New developments in steroid-resistant nephrotic syndrome

Nephrotic syndrome is a disorder of the glomerular filtration barrier, a highly specialised tri-layer structure with unique functional properties. Recent advances emanating from the field of molecular genetics have revealed the podocyte as probably the central player in the control of glomerular filtration. More specifically, the cell-cell junction between adjacent podocyte foot processes, namely, the slit diaphragm, has been revealed to be made up of a sophisticated multi-protein complex which dynamically controls foot process architecture via signalling to the actin cytoskeleton. Key genes that have been identified from the study of inherited nephrotic syndromes include those encoding nephrin, podocin, TRPC6 (transient receptor potential canonical channel-6) and α-actinin-4, and more remain to be found. It is now possible to identify genetic causes underlying a proportion of nephrotic syndromes presenting at any age. The next big challenge for clinicians and researchers is to translate the molecular information learnt into the understanding of acquired, non-inherited forms of the disease and to guide therapeutic options. In this regard several exciting advances have been made, both in understanding the molecular mechanisms of current therapies and in revealing circulating plasma factors and the molecular pathways they trigger in the podocyte, that could be targeted by novel therapies.

Triglyceride-cholesterol imbalance across lipoprotein subclasses predicts diabetic kidney disease and mortality in type 1 diabetes: the FinnDiane Study

BACKGROUND

Circulating cholesterol (C) and triglyceride (TG) levels are associated with vascular injury in type 1 diabetes (T1DM). Lipoproteins are responsible for transporting lipids, and alterations in their subclass distributions may partly explain the increased mortality in individuals with T1DM.

DESIGN AND SUBJECTS

A cohort of 3544 individuals with T1DM was recruited by the nationwide multicentre FinnDiane Study Group. At baseline, six very low-density lipoprotein VLDL, one intermediate-density lipoprotein IDL, three low-density lipoprotein LDL and four higher high-density lipoprotein HDL subclasses were quantified by proton nuclear magnetic resonance spectroscopy. At follow-up, the baseline data were analysed for incident micro- or macroalbuminuria (117 cases in 5.3 years), progression from microalbuminuria (63 cases in 6.1 years), progression from macroalbuminuria (109 cases in 5.9 years) and mortality (385 deaths in 9.4 years). Univariate associations were tested by age-matched cases and controls and multivariate lipoprotein profiles were analysed using the self-organizing map (SOM).

RESULTS

TG and C levels in large VLDL were associated with incident albuminuria, TG and C in medium VLDL were associated with progression from microalbuminuria, and TG and C in all VLDL subclasses were associated with mortality. Large HDL-C was inversely associated with mortality. Three extreme phenotypes emerged from SOM analysis: (i) low C (<3% mortality), (ii) low TG/C ratio (6% mortality), and (iii) high TG/C ratio (40% mortality) in all subclasses.

CONCLUSIONS

TG-C imbalance is a general lipoprotein characteristic in individuals with T1DM and high vascular disease risk.

Podocyte foot process effacement in postreperfusion allograft biopsies correlates with early recurrence of proteinuria in focal segmental glomerulosclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a relatively prevalent glomerular disorder that often progresses to end-stage renal disease. Thirty to 80% of kidney transplant (KT) recipients with FSGS will experience recurrence characterized by proteinuria and podocyte damage. We hypothesized that the degree of podocyte foot process (FP) effacement in postreperfusion transplant biopsies can be used to predict the development of clinical recurrence of FSGS.

METHOD

Nineteen pairs of pre- and postreperfusion biopsy specimens were studied. We evaluated the degree of FP effacement in postreperfusion KT biopsies by counting the number of widened FP per capillary loop. Early recurrence of FSGS was defined as development of nephrotic range proteinuria between days 3 and 30 posttransplant.

RESULTS

Early recurrence occurred in 7 of 19 grafts (36.8%) at a mean of 4.29±1.89 days. The mean score of FP effacement in postreperfusion allograft biopsies was 0.72±0.31 and 1.35±0.63 in the nonrecurrent and recurrent group, respectively (P=0.039). There was an association between FP effacement and proteinuria (P = 0.04). The FP effacement score predicts early recurrence with a sensitivity of 71.4% and specificity of 91.7%.

CONCLUSION

FP effacement can be observed within minutes after reperfusion in renal transplantation of recipients with FSGS that will ultimately develop recurrent FSGS. This suggests a key role for the podocyte injury in the pathogenesis of recurrent FSGS and further supports the presence of circulating factors causing FP effacement. The FP effacement score in the postreperfusion KT biopsy may become a useful predictive test if validated in larger studies.

IgM contributes to glomerular injury in FSGS

Glomerular IgM and C3 deposits frequently accompany idiopathic FSGS and secondary glomerulosclerosis, but it is unknown whether IgM activates complement, possibly contributing to the pathogenesis of these diseases. We hypothesized that IgM natural antibody binds to neoepitopes exposed in the glomerulus after nonimmune insults, triggering activation of the complement system and further injury. We examined the effects of depleting B cells, using three different strategies, on adriamycin-induced glomerulosclerosis. First, we treated wild-type mice with an anti-murine CD20 antibody, which depletes B cells, before disease induction. Second, we evaluated adriamycin-induced glomerulosclerosis in Jh mice, a strain that lacks mature B cells. Third, we locally depleted peritoneal B cells via hypotonic shock before disease induction. All three strategies reduced deposition of IgM in the glomerulus after administration of adriamycin and attenuated the development of albuminuria. Furthermore, we found that glomerular IgM and C3 were detectable in a subset of patients with FSGS; C3 was present as an activation fragment and colocalized with glomerular IgM, suggesting that glomerular IgM may have bound a cognate ligand. Taken together, these results suggest that IgM activates the complement system within the glomerulus in an animal model of glomerulosclerosis. Strategies that reduce IgM natural antibody or that prevent complement activation may slow the progression of glomerulosclerosis.

Combination of pulse methylprednisolone infusions with cyclosporine-based immunosuppression is safe and effective to treat recurrent focal segmental glomerulosclerosis after pediatric kidney transplantation

BACKGROUND

Recurrence of focal segmental glomerulosclerosis (FSGS) in pediatric kidney allografts is associated with poor graft survival. Several therapeutic regimens have been proposed, with conflicting results.

METHODS

Ten pediatric patients with recurrent FSGS after kidney transplantation were treated with a protocol of methylprednisolone (MP) infusions in combination with cyclosporine (CsA)-based immunosuppression. The patients received a drug regimen with infusions of 20 mg/kg MP on three consecutive days at week 1, week 3, and week 5, and then monthly until six months after transplantation. If a complete or partial remission (PR) was obtained, MP pulse continued every three months until 24 months after transplantation. The CsA dose was adjusted according to AUC0-4.

RESULTS

Seven of 10 patients (70%) achieved complete remission (CR) with stable renal function within 18 months of beginning of treatment. One of two patients with PR entered CR 3.5 yr after transplantation. One patient lost her graft due to recurrence four months after transplantation. After observation for 26-119 months, seven patients maintained remission with normal glomerular filtration rate. Few major side effects were observed in association with the high-dose MP infusion therapy.

CONCLUSIONS

MP infusion therapy in combination with CsA-based immunosuppression could be safe and effective in treating recurrent FSGS after kidney transplantation.

Recent progress in the pathophysiology and treatment of FSGS recurrence

Focal segmental glomerulosclerosis (FSGS) is a glomerular disease characterized by proteinuria, frequent progression to end-stage renal disease, and recurrence after kidney transplantation in ∼25% of patients, which negatively impacts long-term allograft survival. Experimental studies suggest that abnormalities in T and, possibly, B cells may represent one initial pathogenic trigger, leading to podocyte injury and progressive loss. New data also support the existence of circulating permeability factors able to damage the podocytes, but no single molecule has been consistently identified as the causal pathogenic element in FSGS recurrence. Unfortunately, major progress from mechanistic studies has not translated into substantial advancements in patient treatment, with plasmapheresis (PP) and high doses of cyclosporine (CsA) remaining the mainstays of therapy. Despite consistent experimental and clinical evidence that treatment of proteinuria slows renal function decline in proteinuric nephropathies, maximal use of antiproteinuric agents such as renin angiotensin system antagonists is not routine in the management of FSGS recurrence. More recently, encouraging results have been reported with anti-CD20 depleting antibody rituximab, but further studies are needed to establish its safety/efficacy profile.