Transcriptional profiling of mouse proximal tubular epithelial cells during injury and repair
Ontology highlight
ABSTRACT: Proximal tubule has a remarkable capacity for repair after acute kidney injury. Whether dedifferentiation or a fixed progenitor population is responsible for this repair remains the subject of ongoing controversy. We have generated a novel genetic mouse model to address this question. We generated a Kim-1-GFPCreERt2 knockin mouse line (Kim1GCE) by homologous recombination. Kim-1 is expressed exclusively in dedifferentiated proximal tubule cells. We crossed this mouse line to the EGFP-L10a mouse line to perform Translating Ribosome Affinity Purification coupled with next generation sequencing (TRAP-seq) to identify the transcriptional signature of tubular epithelial cells during the course of injury and repair. TRAP-seq was performed in kidney samples at day 2, 7, and 14 after bilateral ischemia reperfusion injury and sham.
Project description:Injury to the proximal tubule plays a central role in the initiation and progression of kidney fibrosis, and rates of chronic kidney disease progresses approximately 50% faster in males compared to females. We applied Translating Ribosome Affinity Purification (TRAP) followed by RNA-sequencing to characterize the cell-specific proximal tubule transcriptional landscape during fibrosis in male vs. female mice.
Project description:After acute kidney injury (AKI), patients either recover or alternatively develop fibrosis and chronic kidney disease. Interactions between injured epithelia, stroma and inflammatory cells determine whether kidneys repair or undergo fibrosis, but the molecular events that drive these processes are poorly understood. Here, we use single nucleus RNA sequencing of a mouse model of AKI to characterize cell states during repair from acute injury. We identify a distinct proinflammatory and profibrotic proximal tubule cell state that fails to repair. Deconvolution of bulk RNA-seq datasets indicates that this “failed-repair proximal tubule cell” or FR-PTC, state can be detected in other models of kidney injury, increasing in the aging rat kidney and over time in human kidney allografts. We also describe dynamic intercellular communication networks and discern transcriptional pathways driving successful vs. failed repair. Our study provides a detailed description of cellular responses after injury and suggests that the FR-PTC state may represent a therapeutic target to improve repair.
Project description:FAN1 is a DNA endonuclease that we have previously identified as the underlying genetic cause of karyomegalic interstitial nephritis (OMIM: 614817) in humans. In order to deduce the molecular function of FAN1 in the setting of acute kidney injury and progression to chronic kidney disease, we generated a proximal tubule specific Fan1 knockout mouse model and subjected these mice to cisplatin injury. RNA-seq of the transgenic mice kidneys revealed dysregulation of the DNA damage repair pathway as well as cell cycle associated genes. Together, the data supports for a role of Fan1 in DNA damage repair, and that in its absence results in dysfunctional proximal tubule repair and regeneration upon cisplatin injury.
Project description:Acute kidney injury (AKI) is associated with an abrupt loss of kidney function that results in significant morbidity and mortality. Considerable effort has focused around the identification of diagnostic biomarkers and the analysis of molecular events. Most studies have adopted organ-wide approaches that do not fully capture the interplay among different cell types in the pathophysiology of AKI. To extend our understanding of molecular and cellular events in AKI, we developed a mouse line that enables the identification of translational profiles in specific cell types by CRE recombinase-dependent activation of an eGFP-tagged L10a ribosomal protein subunit, and consequently, translating ribosome affinity purification (TRAP) of mRNA populations. By utilizing cell-type specific CRE-driver lines, in this study we identify distinct cellular responses in an ischemia reperfusion injury (IRI) model of AKI. Cell-specific translational expression profiles were uncovered 24 hours after IRI from four populations enriched for distinct anatomical and cellular subgroups: nephron, interstitial cell populations, vascular endothelium, and macrophages/monocytes by Affymetrix microarray. A construct containing the CAGGS promoter driving eGFP-L10a, with a loxP-site flanked triple SV40 polyA cassette between promoter and eGFP-L10a cassette was targeted into the ubiquitously active Rosa26 locus. The upstream polyA cassette is designed to block activity of the downstream eGFP-L10a cassette. CRE-dependent removal of this transcriptional block activates eGFP::L10a production within the CRE-producing cell, and all of its descendants. Mice carrying the conditional eGFP-L10a allele, referred to as L10a, were maintained in a homozygous state. L10a mice were crossed to four CRE strains to activate eGFP::L10a expression in four predominantly non-overlapping cellular compartments in the kidney. A Six2-Tet-GFP::CRE allele is active exclusively within nephron progenitors; consequently, historical labeling results in eGFP::L10a expression throughout the main body of the nephron. A Foxd1-GFP::CRE allele is active in the progenitors of many of the interstitial cell lineages including those generating mesangial and non-glomerular pericytes. In addition, Foxd1 is normally expressed in podocytes. Cdh5-CRE is reported to be active throughout the vascular endothelium, and finally, Lyz2-CRE specifically labels cells of the myeloid lineage, notably macrophages, monocytes and dendritic cells. Mice carrying any CRE allele and the L10a allele are designated generically CRE-L10a. six2-L10a, foxd1-L10a, cdh5-L10a and lyz2-L10a denote specifically mice that are compound heterozygotes for the indicated CRE driver and L10a. CRE-L10a, L10a heterozygous littermates without CRE allele, C57BL/6 wild type mice were subjected to renal bilateral warm ischemia 28 minutes followed by 24-hour reperfusion when the kidney TRAP RNA and total RNA were isolated and subjected to Affymetrix microarray. Biological triplicates for each CRE-L10a line underwent no Surgery; sham Surgery and IRI treatment.
Project description:We combined lineage tracing of cycling (Ki67+) cells with single nuclear multiomics (single nucleus RNA-seq + single nucleus ATAC-seq) to characterize the long-term (4 weeks and 6 months) outcome of cells that initiate proliferation early after acute kidney injury (AKI). The data document a broad proliferative response to injury in epithelial and non-epithelial kidney cell types, identify novel transcription factors governing the adaptive and maladaptive proximal tubule cell state and highlight the importance of enhancer dynamics in determining cell states. Comparison of lineage traced with control proximal tubule cells reveals long-term effects of AKI on proximal tubule cells, even following adaptive repair.
Project description:Mammalian kidney has very limited ability to repair or regenerate after acute kidney injury (AKI). The maladaptive repair of AKI promotes the progression to chronic kidney disease (CKD). Therefore, it is extremely urgent to explore new strategies to promote the repair/regeneration of injured renal tubules after AKI. It has been shown that hypoxia induces heart regeneration in adult mice. However, it is unknown whether hypoxia can induce kidney regeneration after AKI. In this study, we used a prolyl hydroxylase domain inhibitor (PHDI), MK-8617, to mimic hypoxia condition and found that MK-8617 significantly ameliorates ischemia reperfusion injury (IRI) induced acute kidney injury. We then showed that MK-8617 dramatically facilitates renal regeneration via promoting the proliferation of injured renal proximal tubular cells (RPTCs) after IRI-induced AKI. We then performed bulk mRNA sequencing and discovered that multiple nephrogenesis- related genes were significantly upregulated with MK-8617 pretreatment. Furthermore, we showed that MK-8617 may alleviate proximal tubule injury via stabilizing HIF-1α protein specifically in renal proximal tubular cells. We also demonstrated that MK-8617 promotes the reprogramming of renal proximal tubular cells to Sox9+ renal progenitor cells, and the regeneration of renal proximal tubules. In summary, we discovered that inhibition of prolyl hydroxylase improves renal proximal tubule regeneration after IRI-induced AKI via promoting the reprogramming of renal proximal tubular cells to Sox9+ renal progenitor cells.
Project description:Studies in animal models have suggested a linkage between the inflammatory response to injury and subsequent nephron loss during the acute kidney injury (AKI) to chronic kidney disease (CKD) transition. Failure of normal repair during the CKD transition correlates with de novo expression of vascular cell adhesion protein-1 (VCAM-1) by a subset of injured proximal tubule cells. This study identified the role of VCAM-1 expression in promoting the failed repair state. Single-cell transcriptome analysis of patients with AKI and CKD and whole kidney RNA and protein analyses of mouse models of CKD confirmed a marked increase of VCAM-1 expression in the proximal tubules of injured kidneys. In immortalized mouse proximal tubular cells and primary cultured renal cells (PCRCs), VCAM-1 expression was induced by proinflammatory cytokines including tumor necrosis factor (TNF)-α and interleukin (IL)-1β. Analyses of bulk RNA sequencing of TNF-α-treated primary cultured renal cells or pseudo-bulk RNA sequencing of biopsies from Kidney Precision Medicine Project datasets indicated activation of NF-κB and an enrichment of inflammatory response and cell adhesion pathways in VCAM-1-positive cells. Pharmacological inhibition of NF-κB signaling or genetic deletion of myeloid differentiation factor 88 and TIR domain-containing adapter-inducing interferon-β suppressed TNF-α- and IL-1β-induced VCAM-1 expression in vitro. TNF-α stimulation or overexpression of VCAM-1 significantly increased splenocyte adhesion to the mouse proximal tubular monolayer in culture. These results demonstrate that persistence of proinflammatory cytokines after AKI can induce NF-κB-dependent VCAM-1 expression by proximal tubule cells, mediating increased immune cell adhesion to the tubule and thus promoting further tubule injury and greater risk of progression from AKI to CKD.
Project description:The cellular mechanisms of kidney tubule repair are poorly characterized in human. Here, we applied single-cell RNA sequencing to analyze the kidney in the first days after acute injury in 5 patients with severe COVID19. We found that tubule repair follows two converging patterns involving the plasticity of mature tubule cells and the expansion and differentiation of progenitor-like cells. Tubule repair by cell plasticity displayed substantial similarities between mouse and man and determined the transient expansion of undifferentiated tubule cells with altered functional and metabolic properties. Progenitor-like cells marked by PROM1 proliferated in response to injury and followed a differentiation process characterized by the sequential activation of the WNT, NOTCH and HIPPO signaling pathways. Taken together, our analyses reveal cell state transitions and fundamental cellular hierarchies underlying kidney injury and repair in patients.
Project description:We generated a new macrophage-specific mouse line for the application of Translating Ribosome Affinity Purification (MacTRAP). MacTRAP mice express an eGFP-tagged ribosomal protein (L10a) under the control of the macrophage-specific c-fms promoter (driver of Csf1r). The TRAP line was characterized and expression of the transgene confirmed in kidney and other tissues. Validation included testing the responsiveness of the transgene under pro-inflammatory challenge in the kidney. Using TRAP, we successfully extracted macrophage-specific polysomal RNA from MacTRAP kidneys and conducted RNA-Seq following bioinformatic analyses to establish a comprehensive in vivo gene expression and pathway signature of resident renal macrophages, which may be of use to investigators studying the gene expression profile of these cells. Overall, this new in vivo tool may be of great value for the study of macrophage biology in different organs and various models of injury and disease.
Project description:This study reports the cellular self-organization of primary human renal proximal tubule epithelial cells (RPTECs) around a minimal Matrigel scaffold to produce basal-in and apical-out proximal tubule organoids (tubuloids). These tubuloids are produced and maintained in hanging drop cultures for 90+ days, the longest such culture of any kind reported to date. The tubuloids upregulate maturity markers, such as aquaporin-1 (AQP1) and megalin (LRP2), and exhibit less mesenchymal and proliferation markers, such as vimentin and Ki67, compared to 2D cultures. They also experience changes over time as revealed by a comparison of gene expression patterns of cells in 2D culture and in day 31 and day 67 tubuloids. Gene expression analysis and immunohistochemistry reveal an increase in the expression of megalin, an endocytic receptor that can directly bind and uptake protein or potentially assist protein uptake. The tubuloids, including day 90 tubuloids, uptake fluorescent albumin and reveal punctate fluorescent patterns, suggesting functional endocytic uptake through these receptors. Furthermore, the tubuloids release kidney injury molecule-1 (KIM-1), a common biomarker for kidney injury, when exposed to albumin in both dose- and time-dependent manners. While this study focuses on potential applications for modeling proteinuric kidney disease, the tubuloids may have broad utility for studies where apical proximal tubule cell access is required.