Background: Nephrotic syndrome (NS) occurs when the glomerular filtration barrier becomes abnormally permeable, leading to the clinical triad of proteinuria, massive oedema, and hypoalbuminaemia. Historically, NS has been thought to result from dysregulation of the immune system, although recent evidence suggests the glomerular podocyte plays a central role in disease pathogenesis. Children with NS are generally treated with an empiric course of glucocorticoid (Gc) therapy; a class of steroids which are activating ligands for the glucocorticoid receptor (GR) transcription factor. A major factor limiting the clinical utility of these agents is the marked variation observed in response to treatment. Although Gc-therapy has been the cornerstone of NS management for several decades, the mechanism of action, and target cell, remain poorly understood. Hypothesis and aims: The central hypothesis for this thesis states that glucocorticoids act directly on the podocyte to produce clinically useful effects without involvement of the immune system. Findings: Using a wild-type human podocyte cell line, I demonstrated that the basic GR-signalling mechanism is intact in the podocyte, and that glucocorticoids produce a direct, protective effect on the podocyte without immune cell involvement, by using electrical resistance across a podocyte monolayer as a surrogate marker for barrier integrity. To understand potential mechanisms underpinning this direct effect I defined the podocyte GR cistrome (using a combination of chromatin immunoprecipitation followed by massively parallel DNA sequencing and transcriptomic analysis) as well as total cell proteomics. Subsequent gene ontology analysis revealed that Gc treatment had prominent effects on podocyte motility, and these findings were validated with live-cell imaging. To gain mechanistic insight, I investigated the role of the pro-migratory small GTPase regulator Rac1, and demonstrated that treatment with Gc reduced Rac1 activity. Furthermore, the Rac1 inhibitor EHT 1864 had a direct, protective effect on the podocyte. To create a model to study the role of podocyte GR in vivo I generated a mouse line with a podocyte-specific GR deletion. Impact: Gc exposure produces potentially clinically-relevant effects directly on the podocyte, and Gc-induced podocyte hypomobility may underlie the clinical efficacy of these agents. Future animal studies investigating the consequences of GR deletion in the podocyte and the anti-proteinuric effects of Rac1 inhibition are warranted.

No description available.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 3 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Thesis--Copenhagen. / Summary in Danish. Bibliography: p. [93]-106.

Thesis--Copenhagen. / Summary in Danish. Bibliography: p. [93]-106.

Background Glomerulonephritis is a major cause of end-stage kidney disease (ESRD) in Africa. There is scanty data on the clinico-pathological characteristics and outcome of the mesangioproliferative glomerulonephritides in Africa, despite the non-IgA subtype being reported as a common cause of nephrotic syndrome. This study will assess the outcome of patients with biopsy proven mesangioproliferative glomerulonephritis (MesPGN) from a single centre in Cape Town, South Africa. Methods The study is designed as 10-year retrospective analysis of patients with biopsy proven MesPGN. The MesPGN patterns were divided into non-IgA MesPGN and IgA nephropathy (IgAN), depending on the predominant type of immune deposit. Univariate cox regression analysis was used to determine factors associated with ESRD. Results Data of 109 patients with renal biopsy-proven MesPGN were included for the period between 2005-2014. The mean age at biopsy was 33.8 ±14.9 years, 53.2% were males, and 39.4% were black Africans. Clinically, 58.7% presented with nephrotic syndrome. On histology 79.8% had non-IgA MesPGN, and 20.2% had IgAN. Compared to the non-IgA group, most patients with IgAN were not treated with immunosuppression (72.7% vs. 40.2%; p=0.006). At the last visit, 10.1% reached ESRD (40.9% vs. 2.3%; p<0.0001) and 30.2% achieved complete remission (9.1% vs. 35.7%; p=0.015) for IgAN and non-IgA MesPGN respectively. The 5-year renal survival for IgAN and non-IgA MesPGN respectively, were: 63.3% vs. 97.6%, log rank p=0.001. Overall, hypertension (p=0.019), not receiving immunosuppression (p=0.046) and having IgAN (p=0.007) were independent predictors of progression to ESRD. Conclusion There is a significantly higher ESRD-free survival of patients with biopsy proven non-IgA MesPGN than IgAN. Whether this is related to the limited use of immunosuppressive therapy in IgAN patients or represents a true nature of the disease still requires further research.

Abstract available in the Journal of Investigative Medicine.

Nephrotic syndrome (NS) is the second leading cause of chronic kidney disease (CKD) presenting under the age of 30. NS presents in children with edema and severe proteinuria, caused by the effacement of podocyte foot processes within the glomerular filtration barrier. Patients with steroid-resistant NS (SRNS) frequently develop end-stage renal disease (ESRD). Additionally, renal biopsies from these patients often reveal focal segmental glomerulosclerosis (FSGS). Pathogenic mutations in known monogenic disease genes have been found in 11-45% children with FSGS/SRNS. Notably, most Mendelian etiologies exhibit recessive inheritance, while dominant vertical inheritance with incomplete penetrance is observed in the remainder. The role of de novo variants (DNVs) in NS necessitates further investigation. Tripartite motif containing 8, TRIM8, is an E3 ubiquitin ligase. De novo TRIM8 variants were previously implicated in a syndromic disease consisting of neurodevelopmental delay, epilepsy, cerebral atrophy, and nephrotic syndrome. In this study, we recapitulate the patient-specific mutations in inducible overexpression cell lines and in CRISPR/Cas9-generated mouse models. N-terminal MYC or GFP-tagged TRIM8 inducible cell lines were generated and characterized using the pInducer21 system. Western blot and immunofluorescence data show that MYC- and GFP-TRIM8 were induced by doxycycline in immortalized podocyte cell lines. Candidate interactors for TRIM8 from the literature and stratified using kidney single cell mRNA sequencing expression were cloned into mammalian expression vectors. Finally, a Trim8 knockout allele (c. 56_162del; p.H20Qfs*124 and c.367_463+304delins46) was generated and bred to yield an allelic series of wildtype, heterozygous and homozygous animals. These mice exhibited normal survival and did not demonstrate proteinuria through three to four months of life. Overall, further studies are ongoing with regards to the continued monitoring of proteinuria and kidney dysfunction, as well as the potential interactor cloning and cell line characterization. / 2025-02-06T00:00:00Z

No description available.