Pregnancy in renal transplant patients: Renal function markers and maternal-fetal outcomes

OBJECTIVES

We aimed to evaluate laboratory markers in women who got pregnant after renal transplantation.

STUDY DESIGN

Cross-sectional prospective study.

MAIN OUTCOME MEASURES

Renal function parameters and maternal and fetal data were assessed in renal transplant recipients.

RESULTS

Forty-three women who got pregnant after renal transplantation (mean age, 28.5 years; mean gestational age, 35.6 weeks) were included. Most patients (53.5%) received a renal transplant from a deceased donor. Podocyturia was not significantly correlated with other renal function markers. Mean period from transplantation to pregnancy was approximately 5 years; this period was not associated with obstetric complications or changes in renal markers. A gradual increase was observed in the following parameters during pregnancy and puerperium: serum creatinine levels (P < 0.001), proteinuria (P < 0.001), urinary protein/creatinine ratio (P < 0.001), and albumin/creatinine ratio (P < 0.001). The sensitivity and specificity of protein/creatinine ratio in predicting preeclampsia were high (96.0% and 94.0%, respectively). Elevated serum creatinine levels, urinary albumin/creatinine ratio, and retinol-binding protein levels in the third trimester were associated with prematurity (P < 0.001). Preeclampsia was the main cause of renal function decline at the end of pregnancy (65.0% of cases). Approximately four (9.5%) pregnant women presented with premature rupture of membranes and 18 (42.0%) with a urinary tract infection.

CONCLUSIONS

Proteinuria, urinary protein/creatinine ratio, and retinol-binding protein levels were elevated in patients with preeclampsia. Using these markers to assess renal function during pregnancy may be clinically useful for detecting and monitoring renal injury in renal transplant recipients.

Podocytes: Way to Go

This commentary highlights the article by Hara et al that discusses the clinical implications of mitotic catastrophe in podocyte health during diabetic kidney disease.

Mutations in six nephrosis genes delineate a pathogenic pathway amenable to treatment

No efficient treatment exists for nephrotic syndrome (NS), a frequent cause of chronic kidney disease. Here we show mutations in six different genes (MAGI2, TNS2, DLC1, CDK20, ITSN1, ITSN2) as causing NS in 17 families with partially treatment-sensitive NS (pTSNS). These proteins interact and we delineate their roles in Rho-like small GTPase (RLSG) activity, and demonstrate deficiency for mutants of pTSNS patients. We find that CDK20 regulates DLC1. Knockdown of MAGI2, DLC1, or CDK20 in cultured podocytes reduces migration rate. Treatment with dexamethasone abolishes RhoA activation by knockdown of DLC1 or CDK20 indicating that steroid treatment in patients with pTSNS and mutations in these genes is mediated by this RLSG module. Furthermore, we discover ITSN1 and ITSN2 as podocytic guanine nucleotide exchange factors for Cdc42. We generate Itsn2-L knockout mice that recapitulate the mild NS phenotype. We, thus, define a functional network of RhoA regulation, thereby revealing potential therapeutic targets.

Advances and unmet needs in genetic, basic and clinical science in Alport syndrome: report from the 2015 International Workshop on Alport Syndrome

Alport syndrome (AS) is a genetic disease characterized by haematuric glomerulopathy variably associated with hearing loss and anterior lenticonus. It is caused by mutations in the COL4A3, COL4A4 or COL4A5 genes encoding the α3α4α5(IV) collagen heterotrimer. AS is rare, but it accounts for >1% of patients receiving renal replacement therapy. Angiotensin-converting enzyme inhibition slows, but does not stop, the progression to renal failure; therefore, there is an urgent requirement to expand and intensify research towards discovering new therapeutic targets and new therapies. The 2015 International Workshop on Alport Syndrome targeted unmet needs in basic science, genetics and diagnosis, clinical research and current clinical care. In three intensive days, more than 100 international experts including physicians, geneticists, researchers from academia and industry, and patient representatives from all over the world participated in panel discussions and breakout groups. This report summarizes the most important priority areas including (i) understanding the crucial role of podocyte protection and regeneration, (ii) targeting mutations by new molecular techniques for new animal models and potential gene therapy, (iii) creating optimal interaction between nephrologists and geneticists for early diagnosis, (iv) establishing standards for mutation screening and databases, (v) improving widespread accessibility to current standards of clinical care, (vi) improving collaboration with the pharmaceutical/biotech industry to investigate new therapies, (vii) research in hearing loss as a huge unmet need in Alport patients and (viii) the need to evaluate the risk and benefit of novel (including 'repurposing') therapies on an international basis.

Klotho May Ameliorate Proteinuria by Targeting TRPC6 Channels in Podocytes

Klotho is a type-1 membrane protein predominantly produced in the kidney, the extracellular domain of which is secreted into the systemic circulation. Membranous and secreted Klotho protect organs, including the kidney, but whether and how Klotho directly protects the glomerular filter is unknown. Here, we report that secreted Klotho suppressed transient receptor potential channel 6 (TRPC6)-mediated Ca2+ influx in cultured mouse podocytes by inhibiting phosphoinositide 3-kinase-dependent exocytosis of the channel. Furthermore, soluble Klotho reduced ATP-stimulated actin cytoskeletal remodeling and transepithelial albumin leakage in these cells. Overexpression of TRPC6 by gene delivery in mice induced albuminuria, and exogenous administration of Klotho ameliorated the albuminuria. Notably, immunofluorescence and in situ hybridization revealed Klotho expression in podocytes of mouse and human kidney. Heterozygous Klotho-deficient CKD mice had aggravated albuminuria compared with that in wild-type CKD mice with a similar degree of hypertension and reduced clearance function. Finally, disrupting the integrity of glomerular filter by saline infusion-mediated extracellular fluid volume expansion increased urinary Klotho excretion. These results reveal a potential novel function of Klotho in protecting the glomerular filter, and may offer a new therapeutic strategy for treatment of proteinuria.

Podocyte Autophagy: A Potential Therapeutic Target to Prevent the Progression of Diabetic Nephropathy

Diabetic nephropathy (DN), a leading cause of end-stage renal disease (ESRD), becomes a worldwide problem. Ultrastructural changes of the glomerular filtration barrier, especially the pathological changes of podocytes, lead to proteinuria in patients with diabetes. Podocytes are major components of glomerular filtration barrier, lining outside of the glomerular basement membrane (GBM) to maintain the permeability of the GBM. Autophagy is a high conserved cellular process in lysosomes including impaired protein, cell organelles, and other contents in the cytoplasm. Recent studies suggest that activation of autophagy in podocytes may be a potential therapy to prevent the progression of DN. Here, we review the mechanisms of autophagy in podocytes and discuss the current studies about alleviating proteinuria via activating podocyte autophagy.

The Effects of Extensive Glomerular Filtration of Thin Graphene Oxide Sheets on Kidney Physiology

Understanding how two-dimensional (2D) nanomaterials interact with the biological milieu is fundamental for their development toward biomedical applications. When thin, individualized graphene oxide (GO) sheets were administered intravenously in mice, extensive urinary excretion was observed, indicating rapid transit across the glomerular filtration barrier (GFB). A detailed analysis of kidney function, histopathology, and ultrastructure was performed, along with the in vitro responses of two highly specialized GFB cells (glomerular endothelial cells and podocytes) following exposure to GO. We investigated whether these cells preserved their unique barrier function at doses 100 times greater than the dose expected to reach the GFB in vivo. Both serum and urine analyses revealed that there was no impairment of kidney function up to 1 month after injection of GO at escalating doses. Histological examination suggested no damage to the glomerular and tubular regions of the kidneys. Ultrastructural analysis by transmission electron microscopy showed absence of damage, with no change in the size of podocyte slits, endothelial cell fenestra, or the glomerular basement membrane width. The endothelial and podocyte cell cultures regained their full barrier function after >48 h of GO exposure, and cellular uptake was significant in both cell types after 24 h. This study provided a previously unreported understanding of the interaction between thin GO sheets with different components of the GFB in vitro and in vivo to highlight that the glomerular excretion of significant amounts of GO did not induce any signs of acute nephrotoxicity or glomerular barrier dysfunction.

Mechanisms underpinning remission of albuminuria following bariatric surgery

PURPOSE OF REVIEW

Albuminuria is a biomarker of renal injury commonly used to monitor progression of diabetic kidney disease. The appearance of excess albumin in the urine reflects alterations in the structure and permeability of the glomerular filtration barrier. The present article summarizes the clinical evidence base for remission of albuminuria after bariatric surgery. It furthermore focuses on how beneficial impacts on glomerular podocyte structure and function may explain this phenomenon.

RECENT FINDINGS

A coherent clinical evidence base is emerging demonstrating remission of albuminuria following bariatric surgery in patients with obesity and diabetes. The impaired metabolic milieu in diabetic kidney disease drives podocyte dedifferentiation and death through glucotoxic, lipotoxic proinflammatory, and pressure-related stress. Improvements in these parameters after surgery correlate with improvements in albuminuria and preclinical studies provide mechanistic data that support the existence of cause-effect relationship.

SUMMARY

The benefits of bariatric surgery extend beyond weight loss in diabetes to encompass beneficial effects on diabetic renal injury. Attenuation of the toxic metabolic milieu that the podocyte is exposed to postbariatric surgery suggests that the restitution of podocyte health is a key cellular event underpinning remission of albuminuria.

[Regulatory Effect of Chinese Drugs for Stasis Removing and Collaterals Dredging on the Expres- sions of podocin and CD2AP in Podocyte Slit Diaphragm of Diabetic Nephropathy Rats]

OBJECTIVE

To observe the regulatory effect of Chinese drugs for stasis removing and collaterals dredging (CDSRCD) on the expressions of podocin and CD2AP in podocyte slit diaphragm (SD) of diabetic nephropathy (DN) rats.

METHODS

DN rat model was duplicated in 40 male Sprague- Dawley rats by feeding high fat high glucose diet combined with intraperitoneally injecting 1 % streptozoto- cin (STZ, 35 mg/kg). Totally 36 successfully modeled rats were divided into the model group, the CD- SRCD group,- and the irbesartan group according to random digit table, 12 in each group. Besides, anoth- er 10 normal rats were recruited as a normal group. Rats in the CDSRCD group and the irbesartan group were intragastrically fed with CDSRCD and irbesartan respectively. Rats in the normal group and the mod- el group were fed with equal volume of distilled water at the same time. 24 h urine protein quantitation was detected using ELISA at various time points. Body weight (BW) , kidney weight ( KW), kidney index (KI) , fasting blood glucose (FBG) , serum creatinine (SCr), blood urea nitrogen (BUN), and uric acid (UA) in each group were detected after 16 weeks of intervention. The pathomorphological changes of re- nal tissue were observed under light microscope and electron microscope respectively. The protein and mRNA expressions of podocin and CD2AP were detected by Western blot and Real-time PCR respectively.

RESULTS

(1) Compared with the normal group, 24 h urine protein quantitation significantly increased at week 4, 8, 12, and 16, respectively (P <0. 01). BW was decreased; KI and levels of FBG, SCr, BUN, and UA all increased after modeling (P <0. 01). Compared with the model group, 24 h urine protein quan- titation significantly decreased in the CDSRCD group and the irbesartan group at week 4, 8, 12, and 16, respectively (P <0. 01). Besides, it was more obviously reduced in the CDSRCD group than in the irbe- sartan group (P <0. 05, P <0.01). BUN level obviously decreased both in the CDSRCD group and the irbesartan group after modeling (P <0. 05, P <0. 01). (2) Results of renal pathology showed that disar- ranged renal structure, obviously thickened basement membrane, severely proliferated mesenteria, widely fused foot processes in the model group. All these pathological changes were attenuated in the CD- SRCD group and the irbesartan group to some degree. (3) Results of Western blot and Real-time PCR showed, compared with the normal group, protein and mRNA expressions of podocin and CD2AP decreased in the model group (P <0. 01). Compared with the model group, protein and mRNA expressions of podocin and CD2AP increased in the CDSRCD group and the irbesartan group (P <0. 01). Protein and mRNA expressions of podocin and CD2AP increased more in the CDSRCD group than in the irbesartan group (P <0. 05).

CONCLUSIONS

CDSRCD could protect renal function by lowering urinary protein in DN rats, improve renal pathological changes. Its mechanism might be related to up-regulating mRNA and protein expressions of podocin and CD2AP.

Vascular Endothelial Growth Factor and Podocyte Protection in Chronic Hypoxia: Effects of Endothelin-A Receptor Antagonism

BACKGROUND

Podocytes are major components of the filtration barrier and a renal source of vascular endothelial growth factor (VEGF). Chronic renovascular disease (RVD) progressively degrades the renal function, accompanied by podocyte damage and a progressive reduction in VEGF. We showed that the endothelin (ET) pathway contributes to this pathological process and ET-A (but not ET-B) receptor antagonism protects the kidney in RVD. We hypothesize that ET-A-induced renoprotection is largely driven by the protection of podocyte integrity and function.

METHODS

To mimic the renal environment of chronic RVD, human podocytes were incubated under chronic hypoxia for 96 h and divided in untreated or treated with an ET-A or ET-B receptor antagonist. Cells were quantified after 96 h. Cell homogenates and media were obtained after 1, 24 and 96 h to quantify production of VEGF, anti-VEGF soluble receptor s-Flt1, and the expression of apoptotic mediators. A separate set of similar experiments was performed after addition of a VEGF-neutralizing antibody (VEGF-NA).

RESULTS

Hypoxia decreased podocyte number, which was exacerbated by ET-B but improved after ET-A antagonism. Production of VEGF was preserved by ET-A antagonism, whereas s-Flt1 increased in hypoxic cells after ET-B antagonism only, accompanied by a greater expression of pro-apoptotic mediators. On the other hand, treatment with VEGF-NA diminished ET-A-induced protection of podocytes.

CONCLUSION

ET-A antagonism preserves podocyte viability and integrity under chronic hypoxia, whereas ET-B antagonism exacerbates podocyte dysfunction and death. Enhanced bioavailability of VEGF after ET-A antagonism could be a pivotal mechanism of podocyte protection that significantly contributes to ET-A receptor blockade-induced renal recovery in chronic RVD.

[Protective effects of metformin on glomerular podocytes of type 2 diabetes model rats]

OBJECTIVE

To observe the effects of metformin (MET) on podocalyxin (PCX) expression in renal tissue from type 2 diabetes mellitus (T2DM) model rats and investigate its protective effects against glomerular podocyte injury.

METHOD

The rat model of T2DM was established by feeding with high-fat diet and intraperitoneal injection of low dose of streptozotocin (STZ). All the rats were divided into four groups: diabetic group (n=9), metformin group (300 mg·kg(-1)·d(-1), n=8), glibenclamide group (5 mg·kg(-1)·d(-1), n=8 ) and normal group (n=8). After 8 weeks, urinary PCX and creatinine, blood glucose (BG) and glycated hemoglobin (HbA1c) were detected in all the rats. Immunohistochemistry was used to observe the protein expression of PCX in renal tissue. Real-time polymerase chain reaction (PCR) was performed to detect mRNA expression of PCX. Pathological changes of renal tissue were observed by electron microscope.

RESULTS

Metformin and glyburide treatment decreased the levels of BG and HbA1c [(9.6±1.1) and (9.9±1.1) vs (15.6±1.6) mmol/L, (7.0±0.3)% and (8.0±1.0)% vs (12.4±0.6)%, all P<0.05], compared with diabetes group, while there was no statistically significant difference between the two intervention groups (P>0.05). The level of urinary PCX/urinary creatinine (UPCR) in diabetic rats were higher than that of normal group [(697±136) vs (94±25 ) ng/g, P<0.05), meanwhile the levels of protein and mRNA expression of PCX in kidney tissue reduced remarkably [(0.75±0.11) vs (3.18±0.14), (0.08±0.09) vs (1.00±0.02), both P<0.05]. Above-mentioned indicators could be ameliorated by metformin and glyburide treatment compared to normal group (P<0.05), and there were statistically significant difference between the two intervention groups [(404±83) vs (516±38) ng/g, (1.54±0.06) vs(1.06±0.10), (0.23±0.01) vs (0.16±0.04), all P<0.05)]. Further observation found that basement membrane thickness of kidney [(267±22) vs (106±10)nm )] and fusion rate of foot process (0.80±0.07 vs 0) increased in the rats of diabetic group, and metformin or glyburide treatment can significantly reduced the above changes (P<0.05), additionally, the changes were remarkable different between metformin and glyburide group [(151±17) vs (204±22 ) nm, (0.49±0.04) vs (0.57±0.03), both P<0.05)].

CONCLUSION

Metformin has protective effect on glomerular podocytes by regulating the expression of PCX in renal tissue, independent of its hypoglycemic effect.

Detection of podocyturia in patients with lupus nephritis

INTRODUCTION

The podocyturia has been detected in glomerular diseases, such as lupus nephritis (LN), in which proteinuria is an important manifestation, and its occurrence seems to be limited to the active phase of the disease.

OBJECTIVE

To evaluate podocyturia in LN patients, and the possible association with clinical disease activity.

METHODS

We evaluated 56 patients with LN, that were classified in three groups according to the degree of clinical activity: Group B, no activity (n = 17), Group C with mild (n = 29) and Group D, moderate to severe activity (n = 10). The control group was composed by 29 healthy subjects (Group A). The podocyturia was studied by indirect immunofluorescence using primary antibodies to podocyte: anti-podocin, nephrin and synaptopodin, and a secondary antibody conjugated with FITC. We also evaluated serum creatinine levels, urinary protein/creatinine (P/C) ratio, hematuria and leucocituria.

RESULTS

The podocyturia with anti-podocin and anti-sinaptopodin correlated statistically with the P/C ratio (p = 0.001 and p = 0.013, respectively). The podocyturia with anti-podocin, as well as the P/C ratio showed significant correlation (p < 0.001) with the degree of lupus disease activity, unlike the other two antibodies, anti-nephrin and anti-synaptopodin.

CONCLUSION

Our findings show that podocyturia with anti-podocin could be useful in monitoring disease activity in LN patients.

MicroRNA regulation in renal pathophysiology

MicroRNAs are small, noncoding RNA molecules that regulate a considerable amount of human genes on the post-transcriptional level, and participate in many key biological processes. MicroRNA deregulation has been found associated with major kidney diseases. Here, we summarize current knowledge on the role of microRNAs in renal glomerular and tubular pathologies, with emphasis on the mesangial cell and podocyte dysfunction in diabetic nephropathy, the proximal tubular cell survival in acute kidney injury, the transport function of the thick ascending limb in Ca⁺⁺ imbalance diseases, and the regulation of salt, K⁺ and blood pressure in the distal tubules. Identification of microRNAs and their target genes provides novel therapeutic candidates for treating these diseases. Manipulation of microRNA function with its sense or antisense oligonucleotide enables coordinated regulation of the entire downstream gene network, which has effectively ameliorated several renal disease phenotypes. The therapeutic potentials of microRNA based treatments, though promising, are confounded by major safety issues related to its target specificity, which remain to be fully elucidated.

[Significance of podocytes isolated from urine as a marker of glomerulonephritis activity--is the game worth of a candle?]

The significance of the native urine sediment in the differential of glomerular disease needs no further comments. However the question arises whether it could be useful to develop a more specific diagnostic approach to identify the origin of renal epithelial cells that can be detected in the urine sediments as well. Especially the detection of podocytes in the urine could be a valuable non-invasive method to get information about the disease activity or disease type and could be used as a follow up. So far there are only a few studies that analyzed the clinicaI relevance of renal epithelial cells in the urine. This review summarizes the available information on marker proteins that have been successfully used in the diagnostic of podocytes in the urine. Furthermore it shows possible diagnostic usefulness of epithelial urinary cells assessment and future research directions.

Protective effects of leukemia inhibitory factor against oxidative stress during high glucose-induced apoptosis in podocytes

Leukemia inhibitory factor (LIF) is a pleiotropic glycoprotein belonging to the interleukin-6 family of cytokines. In kidney, LIF regulates nephrogenesis, involves in tubular regeneration, responds to pro- and anti-inflammatory stimuli, and so on. LIF also plays an essential role in protective mechanisms triggered by preconditioning-induced oxidative stress. Although LIF shows a wide range of biologic activities, effects of LIF on high glucose-induced oxidative stress in podocytes remain unclear. The aim of the study was to assess whether LIF can attenuate high glucose-induced apoptosis in podocytes. The result of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay indicated that LIF protected podocytes against high glucose-induced cytotoxicity. The flow cytometry assay showed that LIF attenuated high glucose-induced apoptosis in podocytes. Meanwhile, the result of flow cytometric assay gave the clear indication that LIF decreased high glucose-induced elevated level of reactive oxygen species (ROS). The measurement of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, superoxide dismutase (SOD), malondialdehyde (MDA), and caspase-3 activity levels showed that LIF attenuated the high glucose-induced decreased level of SOD and elevated level of NADPH oxidase, MDA and caspase-3 activity. These results may provide potential therapy for diabetic nephropathy in the future.

Glomerular expression of kidney injury molecule-1 and podocytopenia in diabetic glomerulopathy

BACKGROUND/AIMS

Studies have shown that kidney injury molecule-1 (KIM-1) is upregulated in damaged renal proximal tubules. In this study, we examined KIM-1 expression in glomerular epithelial cells in diabetic glomerulopathy.

METHODS

Renal histology, immunostaining and Western blot for protein level, and real-time PCR for mRNA expression of KIM-1 and podocyte markers were evaluated in untreated or losartan-treated Zucker lean (Fa/+) and Zucker diabetic fatty (Fa/Fa) rats.

RESULTS

The diabetic rats showed an increased glomerular expression of KIM-1. KIM-1 staining was localized primarily in the hyperplastic parietal epithelium of Bowman's capsule in the early stages of diabetes with subsequent increase in KIM-1-positive cells in the glomerular tuft in the more advanced stages. The increase in glomerular KIM-1 was associated with a decrease in podocytes in Fa/Fa rats. Antiproteinuric treatment with losartan attenuated podocytopenia and decreased renal expression of KIM-1 in treated diabetic rats. In an in vitro study, albumin overload increased KIM-1 protein in the primary cultures of rat glomerular epithelial cells.

CONCLUSION

These results show that glomerular KIM-1 expression was increased, in proportion to the extent of proteinuria and podocytopenia in the diabetic animals, supporting that KIM-1 could be used as a potential biomarker for glomerular injury in proteinuric kidney disease.

[Clinical characteristics and WT1 genetic analysis of patients with steroid-resistant nephrotic syndrome accompanied with genitourinary malformations]

OBJECTIVE

To analyze the clinical features and WT1 gene mutations in patients with steroid-resistant nephrotic syndrome (SRNS) accompanied with genitourinary malformations. The expression of podocyte molecules was also investigated in renal specimen of these WT1 mutated patients.

METHODS

From January 2005 to May 2007, 3 cases of SRNS accompanied with genitourinary malformations were involved in this study. The expression of podocyte molecules (nephrin, podocin, alpha-actinin 4, WT1 and CD2AP) in 2 cases was analyzed by immunofluorescence and immunohistochemistry; using PCR to amplify genomic DNA and RT-PCR to amplify WT1 cDNA. GeneScan and GeneScan software were used to quantify the ratio of +KTS/-KTS isoforms.

RESULTS

The age of onset of the 3 cases were 6 months, 1 year and 10 years, respectively. The age at diagnosis was 7 months, 9 years and 15 years, respectively. The phenotype of case 1 and case 3 was male accompanied with genitourinary malformations. Case 2 was phenotypic female. Karyotype analysis of the 3 cases revealed 46, XY. Each case was diagnosed as SRNS. Focal segmental glomerulosclerosis (FSGS) was confirmed in 2 cases. Podocyte molecular expression altered in renal tissues of 2 cases. WT1 staining was negative in case 1. WT1 expression in case 2 showed a diffuse nuclear staining with less obvious speckles compared with controls. WT1 IVS 9 + 5 G > A mutation was detected in case 2 and WT1 exon 9 1186 G > A mutation was detected in case 3. No WT1 mutation was detected in case 1.

CONCLUSIONS

Karyotype analysis and WT1 genetic analyzing should be performed for all female patients with early onset SRNS and in male patients with SRNS accompanied with genitourinary malformations. The abnormal ratio of +KTS/-KTS isoforms caused by WT1 mutations along with abnormal expression of podocyte molecules were involved in the pathogenesis of proteinuria.