Project description:Background: Strategies to improve long term renal allograft survival have been directed to recipient dependent mechanisms of renal allograft injury. In contrast, no such efforts have been made to optimize organ quality in the donor. In order to get insight into the deleterious gene pathways expressed at different time points during deceased kidney transplantation, transcriptomics was performed on kidney biopsies from a large cohort of deceased kidney transplants. Methods: A total of 554 kidney biopsies were taken from living and deceased donor kidneys at donation, after cold ischemia and after reperfusion. Transcriptomics by means of whole genome micro-array analyses followed by functional pathway analyses was performed. Results: Oxidative stress and complement- and coagulation pathways were uncovered as potential pathways for intervention in deceased donors. No genes were found to be differentially expressed between donation and cold ischemia. After reperfusion, pathways related to oxidative stress, NOD-like signalling, MAPK, cytokine-cytokine receptor, complement- and-coagulation and chemokines were enriched in kidneys from deceased organ donors. Pathways related to prolonged and worsening deprivation of oxygen were associated with delayed graft function of DCD grafts. Conclusions: The present study reveals oxidative stress and enrichment of complement and coagulation pathways in deceased donor kidneys. Future intervention therapies to optimize donor organ quality and prolong allograft survival should target oxidative stress and innate immune activation in the donor.
Project description:Fibroblasts are present in every organ. While the role fibroblasts in chronic diseases such as fibrosis or tumor expression has been extensively explored, little is known about their physiological role. The kidney possesses a unique capacity to recover from even severe acute injury. We study molecular mechanisms of this intrinsic repair capacity in the mouse model of ischemia-reperfusion (IR). In this model, the renal artery and vein are clamped for 45 min, leading to acute kidney injury. The kidney spontaneously recovers from such IR injury within 14 days. IR kidney injury is associated with a transient accumulation of fibroblasts in the diseased tissue. We hypothesized that fibroblasts aid the repair of acute IR injury in the kidney. To elucidate how FSP1+ fibroblasts may contribute to the repair of kidney injury, we undertook a global unbiased approach to compare gene expression profiles of fibroblasts isolated from kidneys post-IRI and from control kidneys by FACS sorting. To investigate the role fibroblasts may play in the repair of kidney inhury, we performed ischemia reperfusion injury surgery on transgenic mice in which the FSP-1 promoter drives EGFP expression. Kidney injury peaks at day 3 post-IRI, followed by spontaneous regeration that restores nearly perfect kidney architecture and health by day 10. Fibroblasts are thought to possibly play a role in this process, as they are normally rare in the healthy kidney, acute kidney injury is associated with a transient accumulation of interstitial fibroblasts, but whether they may help repair the acute kidney injury or in fact could contribute to the damage is not known. To compare the gene expression profiles of normal fibroblasts and those from post-ischemic kidneys, we sacrificed control FSP1-GFP mice and the FSP1-GFP mice three days post-IRI. We generated single-cell suspensions from both the post-IRI and control kidneys, and then isolated FSP1-GFP+ cells by FACS sorting that, when cultured on plastic, displayed typical fibroblast morphology. Total RNA was immediately extracted from the sorted cells and amplified to produce enough for a array. We biotinylated five of the samples from post-ischemic kidneys and three of the control (non-ischemic) kidneys and used Affymetrix 3' Arrays to examine differences in gene expression profiles between the two groups that may she some light on what role, if any, fibroblasts play in the spontaneous healing of the kidney after acute kidney injury. We performed ischemia reperfusion surgery in FSP1-GFP mice, and at day 3, we sacrificed the mice, isolated FSP1-GFP positive cells from both IR and normal control kidneys by FACS sorting, extracted total RNA from the isolated FSP1-GFP cells and used Affymetrix Mouse Expression Array 430 2.0 microarrays to perform gene expression profiling of the samples. All told, we performed the FACS Sorting, RNA extration, and hybridization with 5 ischemic kidneys and 3 normal kidneys. Fibroblasts, acute kidney injury, repair, comparative gene expression profiling, microarrays, FACS sorting, role in healing
Project description:In deceased donor kidney transplantation, acute kidney injury (AKI) prioir to surgery is a major determinant of delayed graft function (DGF), but AKI is histologically silent and difficult to assess. We hypothesized that a molecular measurement of AKI would add power to conventional risk assessments to predict the early poor allograft function at first week post transplantation. We performed microarrays on implantation biopsies taken during reperfusion in 70 deceased donor kidneys from 53 donors. Early poor function was classified by two definitions on day 7 post-transplantation: serum creatinine greater than 265 umol/L (3 mg/dL) or the requirement for dialysis. Donor age and related risk scores (Irish, Schold, KDRI) associated with worse early function, as expected, but histologic features (glomerulosclerosis; pathology risk scores (Remuzzi, MAPI)) correlated with donor age but not with poor function. However, molecular AKI signal, previously defined in kidneys with early injury, was the best single predictor of poor allograft function. The combination of donor age and the AKI signal improved the prediction of poor function. In addition, asssessments of tissue quality particularly donor age, Banff ct, Irish and KDRI scores, showed negative correlative trend with late graft function, whereas the AKI signal did not. Thus donor age and the molecular AKI signal are the main predictors of early impaired function, but have little impact on survival.
Project description:Deceased kidney donation after brain death (DBD) is the main source of transplants, yet these grafts yield inferior transplant outcomes when compared to living donation. In brain death, cerebral injury contributes to systemic biological dysregulation, causing significant cellular stress in donor kidneys that adversely impacts the quality of grafts. Here, we hypothesized that proteolytic processes in DBD kidneys might lead to podocyte damage with subsequent development of post-transplant dysfunction. Using protein topography and migration analysis platform (PROTOMAP), we mapped degradation profiles of cytoskeletal proteins in DBD kidneys. Cytoskeletal proteolytic degradation was further studied by Immunoblotting on a separate cohort of deceased and living donor kidney biopsies. To investigate potential mechanism of kidney cytoskeletal protein degradation, in-vitro human podocytes and ex-vivo precision-cut human kidney slices were employed. We found novel proteolytic profiles of key podocyte cytoskeletal proteins in donor kidneys associated with suboptimal posttransplant function. These were unique to brain-death and were not observed in circulatory-death or living-donor kidneys. Talin-specific protein degradation in DBD kidneys indicated Calpain-1 activation may have a key role in proteolytic processes observed in the dysfunctional kidneys. Investigation of the underlying mechanism suggests that Transforming-Growth Factor-β (TGFβ) induces Calpain-1 activation, leading to brain-death specific podocyte degradation patterns and dysregulation of actin cytoskeleton; events that were prevented, in-vitro, by Calpain inhibition. Conclusion Our data demonstrate that podocyte protein degradation impacts the quality of DBD kidneys, propose a role of TGFβ mediated Calpain-1 proteolytic processing of cytoskeletal Talin-1, suggesting therapeutic opportunities to prevent kidney dysfunction.
Project description:The fate of transplanted kidneys is substantially influenced by the graft quality as transplantation of kidneys from elderly and expanded criteria deceased donors (ECD) is associated with higher occurrence of delayed graft function, rejection and inferior long term outcome. Little is known about early molecular fingerprints of these events in different donor categories. Borderline changes represent the most frequent histological finding early after kidney transplantation. Therefore, transcriptomic profiles of early case biopsies diagnosed as borderline changes were studied in ECD, standard criteria deceased donors (SCD) and living donor (LD) kidney transplantation using RNA microarray (Agilent SurePrintG3). The increased transcripts typical for ECD as compared to LD (n=437) showed enrichment of extracellular matrix (ECM) -receptor interaction (p=0.004) and complement and coagulation pathways (p=0.004) and GO terms related to platelet activation, blood coagulation, regulation of cell cycle, acute inflammatory response, wound healing or defense response (p<0.001). Gene annotation analysis of transcripts with increased expression in ECD grafts compared to SCD (n=244) showed the highest enrichment of inflammatory response (p=0.013), response to wounding (p=0.001) and defense response (p=0.005) and ECM-receptor interaction pathway (p=0.043). Comparative gene expression overlaps of ECD, SCD and LD using Venn’s diagrams found 62 up- and 16 down-regulated genes in ECD compared to both LD and SCD. Shared increased transcripts in ECD vs. both SCD and LD included, thrombospondin 2 (THBS2), angiopoietin-like 4 (ANGPTL4), collagens (COL6A3, COL1A1), chemokines CCL13 or interleukin IL11 and most significant down-regulated transcripts included proline rich 35 (PRR35) and fibroblast growth factor 9 (FGF9). Transcriptomic profile of higher inflammation and extracellular matrix remodeling in early borderline changes in the ECD kidney allografts suggest mechanisms how ischemia/reperfusion injury aggravates alloimmune response in the presence of chronic vascular changes.
Project description:Approximately 70% of kidney grafts are obtained from deceased donors, and these grafts must be preserved in hypothermic conditions to prolong their viability until transplantation. However, prolonged cold storage (CS) of kidneys results in poor long-term outcomes after transplantation. We reported previously that CS of rat kidneys for 18 h prior to transplant impaired proteasome function, disrupted protein homeostasis, and reduced graft function. The goal of the present study was to identify the renal proteins that are dysregulated by this CS-induced injury. Isolated donor Lewis rat kidneys were subject to 18-h CS and transplanted into recipient Lewis rats (CS+Tx). Autotransplantation (ATx: transplant with 0-h CS) or Sham (right nephrectomy) surgeries served as controls. The proteome of kidney homogenates was analyzed with tandem mass-tag mass spectrometry to identify CS-induced abnormalities in kidney grafts. CS injury disrupted the renal phosphoproteome in kidney grafts and dysregulated numerous signaling pathways. Integrated analysis of global proteomes and phosphoproteomes identified 15 proteins that were significantly regulated in a CS-specific manner. In particular, proteins and pathways such as complement and coagulation cascades were upregulated, while antioxidant pathways, such as glutathione, were suppressed in CS+Tx groups compared to ATx and Sham controls. This study, for the first time, provides deeper insight into the disruption of the renal graft proteome caused by CS injury and provides a novel set of pathways and molecules that can be investigated to delineate their specific role in renal transplant outcomes, ultimately improving outcomes for patients with end-stage kidney disease.
Project description:Fibroblasts are present in every organ. While the role fibroblasts in chronic diseases such as fibrosis or tumor expression has been extensively explored, little is known about their physiological role. The kidney possesses a unique capacity to recover from even severe acute injury. We study molecular mechanisms of this intrinsic repair capacity in the mouse model of ischemia-reperfusion (IR). In this model, the renal artery and vein are clamped for 45 min, leading to acute kidney injury. The kidney spontaneously recovers from such IR injury within 14 days. IR kidney injury is associated with a transient accumulation of fibroblasts in the diseased tissue. We hypothesized that fibroblasts aid the repair of acute IR injury in the kidney. To elucidate how FSP1+ fibroblasts may contribute to the repair of kidney injury, we undertook a global unbiased approach to compare gene expression profiles of fibroblasts isolated from kidneys post-IRI and from control kidneys by FACS sorting. To investigate the role fibroblasts may play in the repair of kidney inhury, we performed ischemia reperfusion injury surgery on transgenic mice in which the FSP-1 promoter drives EGFP expression. Kidney injury peaks at day 3 post-IRI, followed by spontaneous regeration that restores nearly perfect kidney architecture and health by day 10. Fibroblasts are thought to possibly play a role in this process, as they are normally rare in the healthy kidney, acute kidney injury is associated with a transient accumulation of interstitial fibroblasts, but whether they may help repair the acute kidney injury or in fact could contribute to the damage is not known. To compare the gene expression profiles of normal fibroblasts and those from post-ischemic kidneys, we sacrificed control FSP1-GFP mice and the FSP1-GFP mice three days post-IRI. We generated single-cell suspensions from both the post-IRI and control kidneys, and then isolated FSP1-GFP+ cells by FACS sorting that, when cultured on plastic, displayed typical fibroblast morphology. Total RNA was immediately extracted from the sorted cells and amplified to produce enough for a array. We biotinylated five of the samples from post-ischemic kidneys and three of the control (non-ischemic) kidneys and used Affymetrix 3' Arrays to examine differences in gene expression profiles between the two groups that may she some light on what role, if any, fibroblasts play in the spontaneous healing of the kidney after acute kidney injury.
Project description:Urine was obtained from healthy kidney donors, from transplanted kidneys intrasurgery, at postoperative day 1 and at later timepoints. Exosomes were isolated and measured using nLC-MS/MS. For details, see the accompanying manuscript.