Podocyte Foot Process Effacement in Postreperfusion Allograft Biopsies Correlates With Early Recurrence of Proteinuria in Focal Segmental Glomerulosclerosis

AbstractDetermining the cause of focal segmental glomerulosclerosis (FSGS) has crucial implications for evaluating the risk of posttransplant recurrence. The degree of foot process effacement (FPE) on electron micrographs (EM) of native kidney biopsies can reportedly differentiate primary FSGS from secondary FSGS. However, no systematic evaluation of FPE in genetic FSGS has been performed. In this study, percentage of FPE and foot process width (FPW) in native kidney biopsies were analyzed in eight genetic FSGS patients and nine primary FSGS patients. All genetic FSGS patients showed segmental FPE up to 38% and FPW below 2000 nm, while all primary FSGS patients showed diffuse FPE above 88% and FPW above 3000 nm. We reviewed the literature which described the degree of FPE in genetic FSGS patients and identified 38 patients with a description of the degree of FPE. The degree of FPE in patients with mutations in the genes encoding proteins associated with slit diaphragm and cytoskeletal proteins was varied, while almost all patients with mutations in other FSGS genes showed segmental FPE. In conclusion, the present study suggests that the degree of FPE in native kidney biopsies may be useful for differentiating some genetic FSGS patients from primary FSGS patients.

Download Full-text

Novel diagnostic and therapeutic techniques reveal changed metabolic profiles in recurrent focal segmental glomerulosclerosis

Scientific Reports ◽

10.1038/s41598-021-83883-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Janina Müller-Deile ◽

George Sarau ◽

Ahmed M. Kotb ◽

Christian Jaremenko ◽

Ulrike E. Rolle-Kampczyk ◽

...

Keyword(s):

Kidney Transplantation ◽

Raman Spectra ◽

Focal Segmental Glomerulosclerosis ◽

Disease Recurrence ◽

Early Recurrence ◽

Metabolome Analysis ◽

Novel Technologies ◽

Filtration Barrier ◽

Segmental Glomerulosclerosis ◽

Living Related

AbstractIdiopathic forms of Focal Segmental Glomerulosclerosis (FSGS) are caused by circulating permeability factors, which can lead to early recurrence of FSGS and kidney failure after kidney transplantation. In the past three decades, many research endeavors were undertaken to identify these unknown factors. Even though some potential candidates have been recently discussed in the literature, “the” actual factor remains elusive. Therefore, there is an increased demand in FSGS research for the use of novel technologies that allow us to study FSGS from a yet unexplored angle. Here, we report the successful treatment of recurrent FSGS in a patient after living-related kidney transplantation by removal of circulating factors with CytoSorb apheresis. Interestingly, the classical published circulating factors were all in normal range in this patient but early disease recurrence in the transplant kidney and immediate response to CytoSorb apheresis were still suggestive for pathogenic circulating factors. To proof the functional effects of the patient’s serum on podocytes and the glomerular filtration barrier we used a podocyte cell culture model and a proteinuria model in zebrafish to detect pathogenic effects on the podocytes actin cytoskeleton inducing a functional phenotype and podocyte effacement. We then performed Raman spectroscopy in the < 50 kDa serum fraction, on cultured podocytes treated with the FSGS serum and in kidney biopsies of the same patient at the time of transplantation and at the time of disease recurrence. The analysis revealed changes in podocyte metabolome induced by the FSGS serum as well as in focal glomerular and parietal epithelial cell regions in the FSGS biopsy. Several altered Raman spectra were identified in the fractionated serum and metabolome analysis by mass spectrometry detected lipid profiles in the FSGS serum, which were supported by disturbances in the Raman spectra. Our novel innovative analysis reveals changed lipid metabolome profiles associated with idiopathic FSGS that might reflect a new subtype of the disease.

Download Full-text

Mechanical challenges and cytoskeletal impairments in focal segmental glomerulosclerosis

AJP Renal Physiology ◽

10.1152/ajprenal.00641.2017 ◽

2018 ◽

Vol 314 (5) ◽

pp. F921-F925 ◽

Cited By ~ 5

Author(s):

Di Feng ◽

Clark DuMontier ◽

Martin R. Pollak

Keyword(s):

Blood Flow ◽

Focal Segmental Glomerulosclerosis ◽

Kidney Injury ◽

Future Research ◽

Disease States ◽

Filtration Barrier ◽

Segmental Glomerulosclerosis ◽

The Face ◽

Foot Process ◽

Future Research Directions

Focal segmental glomerulosclerosis (FSGS) is a histologically defined form of kidney injury typically mediated by podocyte dysfunction. Podocytes rely on their intricate actin-based cytoskeleton to maintain the glomerular filtration barrier in the face of mechanical challenges resulting from pulsatile blood flow and filtration of this blood flow. This review summarizes the mechanical challenges faced by podocytes in the form of stretch and shear stress, both of which may play a role in the progression of podocyte dysfunction and detachment. It also reviews how podocytes respond to these mechanical challenges in dynamic fashion through rearranging their cytoskeleton, triggering various biochemical pathways, and, in some disease states, altering their morphology in the form of foot process effacement. Furthermore, this review highlights the growing body of evidence identifying several mutations of important cytoskeleton proteins as causes of FSGS. Lastly, it synthesizes the above evidence to show that a better understanding of how these mutations leave podocytes vulnerable to the mechanical challenges they face is essential to better understanding the mechanisms by which they lead to disease. The review concludes with future research directions to fill this gap and some novel techniques with which to pursue these directions.

Download Full-text

Proteolytic program-dependent functions are impaired in INF2-mediated focal segmental glomerulosclerosis

10.1101/530642 ◽

2019 ◽

Cited By ~ 1

Author(s):

Balajikarthick Subramanian ◽

Justin Chun ◽

Chandra Perez ◽

Paul Yan ◽

Isaac Stillman ◽

...

Keyword(s):

Focal Segmental Glomerulosclerosis ◽

Segmental Glomerulosclerosis ◽

Terminal Fragment ◽

Cathepsin Proteases ◽

Foot Process ◽

Inhibitory Domain ◽

Altered Regulation ◽

Actin Regulatory Proteins ◽

And Function ◽

Mutant Polypeptides

AbstractRegulation of the actin cytoskeleton is critical for normal glomerular podocyte structure and function. Altered regulation of the podocyte cytoskeleton can lead to proteinuria, reduced kidney filtration function and focal segmental glomerulosclerosis (FSGS). Mutations in inverted formin 2 (INF2), a member of the formin family of actin regulatory proteins, are the most common cause of autosomal dominant FSGS. INF2 is a multi-domain protein regulated by interaction between its N-terminal Diaphanous Inhibitory Domain (DID) and its C-terminal Diaphanous Auto-regulatory Domain (DAD). Although many aspects of the INF2 DID-DAD interaction are understood, it remains unclear why disease-causing mutations are restricted to the DID and how these mutations cause human disease. Here we report a proteolytic cleavage in INF2 that liberates the INF2 N-terminal DID to function independently of the INF2 C-terminal fragment containing the DAD domain. N-terminal DID region epitopes are differentially localized to podocyte foot process structures in normal glomeruli. This N-terminal fragment localization is lost in INF2-mediated FSGS, whereas INF2 C-terminal fragment epitopes localize to the podocyte cell body in both normal and disease conditions. INF2 cleavage is mediated by cathepsin proteases. In cultured podocytes, the wild-type INF2 N-terminal fragment localizes to membrane regions and promotes cell spreading, while these functions are impaired in a disease-associated INF2 mutant R218Q in the DID. These features are dependent on INF2-cleavage, with accompanying interaction of INF2 N-fragment with mDIA1. Our data suggest a unique cellular function of the DID dependent on INF2 cleavage and help explain the altered localization of FSGS-associated INF2 mutant polypeptides.

Download Full-text

Pediatric Focal Segmental Glomerulosclerosis: Favorable Transplantation Outcome With Plasma Exchange

10.21203/rs.3.rs-806062/v1 ◽

2021 ◽

Author(s):

Fatina I Fadel ◽

Hafez M Bazaraa ◽

Mohamed A Abdel Mawla ◽

Doaa M Salah

Keyword(s):

Plasma Exchange ◽

Focal Segmental Glomerulosclerosis ◽

Survival Data ◽

Early Recurrence ◽

Transplant Recipients ◽

Kidney Transplant Recipients ◽

Segmental Glomerulosclerosis ◽

Kaplan Meier ◽

One Year

Abstract Background: Although kidney transplantation (KT) is the treatment of choice for pediatric kidney failure (KF); concerns for recurrence in cases of focal segmental glomerulosclerosis (FSGS) are still present. This study aimed to investigate the outcome of KT in children with KF secondary to FSGS, with implementation of preemptive perioperative plasma exchange (PE) for non-genetically proven patients.Methods: Forty FSGS pediatric kidney transplant recipients were studied. Of them: 12 patients (30%) had genetically proven NPHS2 mutations/familial and 28 (70%) were sporadic FSGS patients. Sporadic patients electively received 6 preoperative PE sessions. Recurrence of proteinuria was managed with PE and Rituximab (RTX). Kaplan-Meier curves were used to analyze graft and recurrence free survival data.Results: The mean follow-up duration after KT was 3.8 ± 2.86 years. Recurrence of proteinuria was encountered early postoperative in 11 patients (27.5%) and late (1.6 and 2.9 years after KT) in 2 patients (5%). Proteinuria was less in patients underwent native nephrectomy than others immediately postoperative and at assessment (p= 0.002 & 0.0031 respectively). One-year graft and patient survival was 93.8% with a mean 1-year serum creatinine of 0.67 ± 0.25 mg/dl. Three graft losses (7.5%) were due to chronic rejection 3.3, 3.75 and 4.17 years after KT and 2 patients' mortality (5%) occurred early postoperative (first 2 weeks) due to infection.Conclusion: FSGS transplanted children have favorable outcomes with perioperative PE for non-genetically proven cases. Early recurrence after KT can be successfully managed with PE and RTX.

Download Full-text

Epithelial Cell Foot Process Effacement in Podocytes in Focal and Segmental Glomerulosclerosis: A Quantitative Analysis

Ultrastructural Pathology ◽

10.3109/01913123.2014.927405 ◽

2014 ◽

Vol 38 (5) ◽

pp. 303-308 ◽

Cited By ~ 1

Author(s):

Hala Kfoury

Keyword(s):

Quantitative Analysis ◽

Epithelial Cell ◽

Focal And Segmental Glomerulosclerosis ◽

Segmental Glomerulosclerosis ◽

Foot Process Effacement ◽

Foot Process

Download Full-text

Melanocortin therapy ameliorates podocytopathy and proteinuria in experimental focal segmental glomerulosclerosis involving a podocyte specific non-MC1R-mediated melanocortinergic signaling

Clinical Science ◽

10.1042/cs20200016 ◽

2020 ◽

Vol 134 (7) ◽

pp. 695-710

Author(s):

Yingjin Qiao ◽

Pei Wang ◽

Mingyang Chang ◽

Bohan Chen ◽

Yan Ge ◽

...

Keyword(s):

Beneficial Effect ◽

Focal Segmental Glomerulosclerosis ◽

De Novo ◽

Protective Action ◽

Clinical Effectiveness ◽

Podocyte Injury ◽

Segmental Glomerulosclerosis ◽

Foot Process

Abstract The clinical effectiveness of adrenocorticotropin in inducing remission of steroid-resistant nephrotic syndrome points to a steroidogenic-independent anti-proteinuric activity of melanocortins. However, which melanocortin receptors (MCR) convey this beneficial effect and if systemic or podocyte-specific mechanisms are involved remain uncertain. In vivo, wild-type (WT) mice developed heavy proteinuria and kidney dysfunction following Adriamycin insult, concomitant with focal segmental glomerulosclerosis (FSGS) and podocytopathy, marked by loss of podocin and synaptopodin, podocytopenia and extensive foot process effacement on electron microscopy. All these pathologic findings were prominently attenuated by NDP-MSH, a potent non-steroidogenic pan-MCR agonist. Surprisingly, MC1R deficiency in MC1R-null mice barely affected the severity of Adriamycin-elicited injury. Moreover, the beneficial effect of NDP-MSH was completely preserved in MC1R-null mice, suggesting that MC1R is likely non-essential for the protective action. A direct podocyte effect seems to contribute to the beneficial effect of NDP-MSH, because Adriamycin-inflicted cytopathic signs in primary podocytes prepared from WT mice were all mitigated by NDP-MSH, including apoptosis, loss of podocyte markers, de novo expression of the podocyte injury marker desmin, actin cytoskeleton derangement and podocyte hypermotility. Consistent with in vivo findings, the podoprotective activity of NDP-MSH was fully preserved in MC1R-null podocytes. Mechanistically, MC1R expression was predominantly distributed to glomerular endothelial cells in glomeruli but negligibly noted in podocytes in vivo and in vitro, suggesting that MC1R signaling is unlikely involved in direct podocyte protection. Ergo, melanocortin therapy protects against podocyte injury and ameliorates proteinuria and glomerulopathy in experimental FSGS, at least in part, via a podocyte-specific non-MC1R-mediated melanocortinergic signaling.

Download Full-text

Novel Diagnostic and Therapeutic Techniques Reveal Changed Metabolic Profiles in Recurrent Focal Segmental Glomerulosclerosis

10.21203/rs.3.rs-109697/v1 ◽

2020 ◽

Author(s):

Janina Müller-Deile ◽

George Sarau ◽

Christoph Daniel ◽

Christian Jaremenko ◽

Ahmed M Kotb ◽

...

Keyword(s):

Kidney Transplantation ◽

Raman Spectra ◽

Focal Segmental Glomerulosclerosis ◽

Disease Recurrence ◽

Early Recurrence ◽

Metabolome Analysis ◽

Novel Technologies ◽

Filtration Barrier ◽

Segmental Glomerulosclerosis ◽

Living Related

Abstract Idiopathic forms of Focal Segmental Glomerulosclerosis (FSGS) are caused by circulating permeability factors, which can lead early recurrence of FSGS and kidney failure after kidney transplantation. In the past three decades, many research endeavors were undertaken to identify these unknown factors. Even though some potential candidates have been recently discussed in the literature, “the” actual factor remains elusive. Therefore, there is an increased demand in FSGS research for the use of novel technologies that allow us to study FSGS from a yet unexplored angle. Here, we report the successful treatment of recurrent FSGS in a patient after living related kidney transplantation by removal of circulating factors with CytoSorb apheresis. Interestingly, the classical published circulating factors were all in normal range in this patient but early disease recurrence in the transplant kidney and immediate response to CytoSorb apheresis were still suggestive for pathogenic circulating factors. To proof the functional effects of the patient’s serum on podocytes and the glomerular filtration barrier we used a podocyte cell culture model and a proteinuria model in zebrafish to detect pathogenic effects on the podocytes actin cytoskeleton inducing a functional phenotype. We then performed Raman spectroscopy in the <50 kD serum fraction, on cultured podocytes treated with the FSGS serum and in kidney biopsies of the same patient at the time of transplantation and at the time of disease recurrence. The analysis revealed changes in podocyte metabolom induced by the FSGS serum as well as in focal glomerular and parietal epithelial cell regions in the FSGS biopsy. Several altered Raman spectra were identified in the fractionated serum and metabolome analysis by mass spectrometry detected lipid profiles in the FSGS serum, which were supported by disturbances in the Raman spectra. Our novel innovative analysis reveals changed lipid metabolome profiles associated with idiopathic FSGS that might reflect a new subtype of the disease.

Download Full-text