| 1. |
- Charrin, Emmanuelle, et al.
(author)
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Soluble Klotho protects against glomerular injury through regulation of ER stress response
- 2023
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In: Communications Biology. - : Springer Nature. - 2399-3642. ; 6:1
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Journal article (peer-reviewed)abstract
- alpha Klotho (Klotho) has well established renoprotective effects; however, the molecular pathways mediating its glomerular protection remain incompletely understood. Recent studies have reported that Klotho is expressed in podocytes and protects glomeruli through auto- and paracrine effects. Here, we examined renal expression of Klotho in detail and explored its protective effects in podocyte-specific Klotho knockout mice, and by overexpressing human Klotho in podocytes and hepatocytes. We demonstrate that Klotho is not significantly expressed in podocytes, and transgenic mice with either a targeted deletion or overexpression of Klotho in podocytes lack a glomerular phenotype and have no altered susceptibility to glomerular injury. In contrast, mice with hepatocyte-specific overexpression of Klotho have high circulating levels of soluble Klotho, and when challenged with nephrotoxic serum have less albuminuria and less severe kidney injury compared to wildtype mice. RNA-seq analysis suggests an adaptive response to increased endoplasmic reticulum stress as a putative mechanism of action. To evaluate the clinical relevance of our findings, the results were validated in patients with diabetic nephropathy, and in precision cut kidney slices from human nephrectomies. Together, our data reveal that the glomeruloprotective effects of Klotho is mediated via endocrine actions, which increases its therapeutic potential for patients with glomerular diseases. Transgenic overexpression of alpha Klotho in hepatocytes results in protection against renal insults, possibly through modulation of the ER stress response by circulating alpha Klotho. In contrast, alpha Klotho overexpressed in podocytes is not renoprotective.
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| 2. |
- Dabaghie, Dina
(author)
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Identification of genes and pathways involved in the development and progression of glomerular diseases
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Chronic kidney disease (CKD) affects millions of people worldwide and is characterized by a reduction in glomerular filtration rate and albuminuria resulting in a gradual loss of kidney function. The high prevalence of the disease, along with the limited treatment options available, makes it a major burden to the health care systems around the world. Current treatment strategies are directed towards slowing the progression and delaying the complications. The glomerulus is the filtration unit of the kidney and a major target of injury, making glomerular diseases one of the leading causes of CKD. The kidney is a challenging organ to study due to tissue heterogeneity, complex disease phenotypes and morphologies. The lack of knowledge on the molecular mechanisms of disease pathogenesis limits the development of new diagnostic and treatment tools. The main aim of this thesis was to gain a better understanding into genes and pathways involved in the development and progression of glomerular diseases. In a long run, our aim is to utilize the gained knowledge to develop new means to diagnose and treat CKD. In the first part of the thesis (paper I and II), we used single cell RNA-sequencing (scRNAseq) to get insights into the glomerular environment in health and disease, as well as under drug therapy. Paper I: By profiling the glomerulus, we defined the true transcriptomic signatures of specific cell types, gained better insight into their functionality, and identified molecular profiles of rare cell types. By comparing the expression profiles between mouse and human glomerulus, we revealed significant cross-species differences in the main glomerular cells. Paper II: By profiling the molecular signatures of Angiotensin Converting Enzyme-inhibitor (ACEi) in diseased glomerular tissue, we revealed mesangial cells (MCs) to be the main early responder to the treatment. MCs showed downregulation of genes and pathways related to extracellular matrix (ECM) production. Only few transcriptomic changes were detected in the other glomerular cell types. In the second part of the thesis (paper III and IV), we investigated two candidate genes identified through transcriptomic studies. Retinoic acid receptor responder 1 (Rarres1) and Natriuretic peptide receptor 3 (NPR3) were analysed through various in vitro and in vivo experiments. Paper III: We investigated the role of Rarres1 in the glomerulus using various transgenic mouse lines, molecular profiling of patient material and in vitro models. We identified Rarres1 as a possible therapeutic target and biomarker of injury for glomerular diseases. In diseases, an up-regulation of Rarres1 expression was observed in endothelial cells, in which it aggravated the glomerular injury. This effect was potentially mediated by the activation of NFκB pathway via tyrosine kinase Axl Paper IV: We analysed the role of NPR3 in the glomerulus, and especially explored the possibility of manipulating glomerular natriuretic peptide (NP) system through NPR3. Pharmacological inhibition of NPR3 showed variable reno-protective effects when profiled in two rodent models of glomerular injury, suggesting that the modulation of the glomerular NP system could be a potential therapeutic target for CKD. However, more studies are needed to optimise the treatment strategy and to further understand the role of NPR3 in kidney tissue. To summarise in this thesis, we have demonstrated the power of transcriptomic approach in gaining new knowledge on the molecular biology of the glomerulus. Moreover, our studies with Rarres1 and NPR3 contribute to identification of possible novel therapeutic approaches and biomarkers.
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| 3. |
- He, Bing, et al.
(author)
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Single-cell RNA sequencing reveals the mesangial identity and species diversity of glomerular cell transcriptomes
- 2021
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In: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Journal article (peer-reviewed)abstract
- Molecular characterization of the individual cell types in human kidney as well as model organisms are critical in defining organ function and understanding translational aspects of biomedical research. Previous studies have uncovered gene expression profiles of several kidney glomerular cell types, however, important cells, including mesangial (MCs) and glomerular parietal epithelial cells (PECs), are missing or incompletely described, and a systematic comparison between mouse and human kidney is lacking. To this end, we use Smart-seq2 to profile 4332 individual glomerulus-associated cells isolated from human living donor renal biopsies and mouse kidney. The analysis reveals genetic programs for all four glomerular cell types (podocytes, glomerular endothelial cells, MCs and PECs) as well as rare glomerulus-associated macula densa cells. Importantly, we detect heterogeneity in glomerulus-associated Pdgfrb-expressing cells, including bona fide intraglomerular MCs with the functionally active phagocytic molecular machinery, as well as a unique mural cell type located in the central stalk region of the glomerulus tuft. Furthermore, we observe remarkable species differences in the individual gene expression profiles of defined glomerular cell types that highlight translational challenges in the field and provide a guide to design translational studies. The molecular identity of renal glomerular cells is poorly characterized and rodent glomerulopathy models translate poorly to humans. Here, the authors show molecular signatures of glomerulus-associated cells using single cell RNA sequencing and highlight differences between mouse and human cells.
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