Severe ischemia-reperfusion injury (IRI) causes acute and chronic kidney allograft damage. As therapeutic interventions to reduce damage are limited yet, research on how to promote kidney repair has gained significant interest. To address this question, we performed genome-wide transcriptome and epigenome profiling in progenitor cells isolated from the urine of deceased (severe IRI) and living (mild IRI) donor human kidney transplants and identified LIM homeobox-1 (LHX1) as an epigenetically regulated gene whose expression depends on the IRI severity. Using a mouse model of IRI, we observed a relationship between IRI severity, LHX1 promoter hypermethylation, and LHX1 gene expression. Using functional studies, we confirmed that LHX1 expression is involved in the proliferation of epithelial tubular cells and podocyte differentiation from kidney progenitor cells. Our results provide evidence that severe IRI may reduce intrinsic mechanisms of kidney repair through epigenetic signaling.

Parietal epithelial cells (PECs) are kidney progenitor cells with similarities to a bone marrow stem cell niche. In focal segmental glomerulosclerosis (FSGS) PECs become activated and contribute to extracellular matrix deposition. Colony stimulating factor-1 (CSF-1), a hematopoietic growth factor, acts via its specific receptor, CSF-1R, and has been implicated in several glomerular diseases, although its role on PEC activation is unknown. Here, we found that CSF-1R was upregulated in PECs and podocytes in biopsies from patients with FSGS. Through in vitro studies, PECs were found to constitutively express CSF-1R. Incubation with CSF-1 induced CSF-1R upregulation and significant transcriptional regulation of genes involved in pathways associated with PEC activation. Specifically, CSF-1/CSF-1R activated the ERK1/2 signaling pathway and upregulated CD44 in PECs, while both ERK and CSF-1R inhibitors reduced CD44 expression. Functional studies showed that CSF-1 induced PEC proliferation and migration, while reducing the differentiation of PECs into podocytes. These results were validated in the Adriamycin-induced FSGS experimental mouse model. Importantly, treatment with either the CSF-1R-specific inhibitor GW2580 or Ki20227 provided a robust therapeutic effect. Thus, we provide evidence of the role of the CSF-1/CSF-1R pathway in PEC activation in FSGS, paving the way for future clinical studies investigating the therapeutic effect of CSF-1R inhibitors on patients with FSGS.

Background and Aims: Inflammatory pouch disorders exhibit a heterogeneous clinical spectrum and therapeutic requirements have not been properly studied. Methods: This retrospective, multicentre study included ulcerative colitis patients with ileal pouch construction and were later diagnosed with an inflammatory pouch disorder between 1995 and 2020. Classifications, behaviour and therapies applied were recorded and compared in the long-term. Results: Overall, 338 patients were recruited. The most common disorders were pouchitis (n = 258, 76%), Crohn's disease of the pouch (n = 55, 16%) and cuffitis (n = 25, 7%). Pouchitis presented mainly as chronic (65.2%) and recurrent (87%) forms. Crohn's disease manifested as stricturing/penetrating in 53% of cases and perianal disease in 42%. Patients received multiple therapies: 86% antibiotics, 42% steroids, 27% immunosuppressants, 43% biologics and 27% surgery. Compared with pouchitis, Crohn's disease of the pouch was characterised by a later diagnosis (99 vs. 55 months, p < 0.001) and greater needs for immunosuppressants (OR 3.53, 1.79-6.94, p < 0.0001), biologics (OR 5.45, 2.78-10.6, p < 0.0001) and surgeries (OR 2.65, 1.43-4.89, p < 0.001). Conclusions: Chronic pouchitis is the most common pouch disorder presentation. These entities have diverse therapeutics requirements, particularly for Crohn's disease of the pouch.

Abstract Background and Aims Fibrosis is responsible for the loss of kidney function as a result of several insults, such as ischemia-reperfusion injury or hyperfiltration. This process can continue even after cessation of the primary insult, as documented in acute kidney injury to chronic kidney disease. Recently, we discovered that iron accumulation is a hallmark of fibrotic diseases [1]. We found that in mouse models, iron deposition in the kidney accompanies the progression of the disease. Based on these results, we propose that chronic-low grade hemolysis produced in situation like ischemia-reperfusion injury may be one of the drivers of fibrosis through the damage that the filtrated hemolytic iron cause to the kidneys. Early detection of this iron could help the detection of ongoing fibrogenesis and improve the outcomes by prompt intervention. The challenge of this approach is the lack of non-invasive markers of fibrosis. We evaluated if magnetic resonance image (MRI)-based detection of iron levels in the kidney are correlated to fibrosis in biopsies from kidney transplant recipients. Method After approval from the Institutional Revision Board, we carried out a transversal study in our center between 2020 and 2021. We evaluated iron deposits through MRI in patients who underwent a kidney biopsy (per protocol or by clinical indication) and its association with histological parameters. MRI was performed at the same period the biopsy was done. Iron deposits were estimated by using the R2* sequence considering the Grassedonio protocol [2]. Results We collected data from 15 kidney transplant recipients. Mean age was 58.3 years old. Mean time from kidney transplant to the biopsy was 4.3 years and mean eGFR was 44.4 ml/min/1.73 m2.We analyzed by MRI the R2* signal in the kidney cortex, and their level of fibrosis measured on the biopsies (IFTA score, interstitial fibrosis and tubular atrophy). We found that patients with high IFTA score (2 and 3) presented with significantly higher R2* signal (p = 0.005), than patients with low IFTA score (0 and 1). We also found positive and significant correlation between IFTA (0-3) and iron deposits (Spearman correlation index: r = 0.7537, p = 0.0012). Conclusion Iron deposits in the kidney are higher in patients with more fibrosis, and its detection through MRI could be considered a non-invasive marker.

Abstract Background and Aims Focal segmental glomerulosclerosis (FSGS) is the most common glomerular cause leading to end-stage kidney disease. Actual treatment of primary FSGS by immunosuppressive agents presents inconsistent results. Thus, new innovative strategies different from those used to date by taking into consideration podocyte renewal and maintenance or even strategies complementary to immunosuppression are needed. In FSGS, parietal epithelial cells (PECs) switch to an activated phenotype (aPECs) in response to podocyte damage promoting glomerulosclerosis. Colony-stimulating factor (CSF-1) is a hematopoietic growth factor that acts via its specific receptor, the tyrosine kinase receptor CSF-1R. CSF-1 has been detected in sera and renal biopsies from patients with different renal complications, including FSGS, attributing their role and presence to macrophage but not to glomerular cells. The potential cellular and molecular mechanisms involved are also unknown. In this work, we evaluated the implication of CSF-1/CSF-1R axis in the pathogenesis of FSGS and its potential as new pharmacological target point by using specific CSF-1R inhibitors. Specifically, we focused on the modulation of PECS activation by de novo production of CD44 and the preservation of podocyte loss. Method We evaluated the role of the CSF-1/CSF-1R axis as a driver of glomerular damage in FSGS in adriamycin-induced nephropathy (ADR) in mice, the main experimental model to study human FSGS. To this end, we treated or not ADR-animals with CSF-1R specific inhibitors, GW2580 or Ki20227 (n = 5-7 group). We determined the expression and localization of CSF-1R in the glomerulus in tissue by triple immunofluorescence (WT-1, SSeCks and CSF-1R) and their relevance in glomerulosclerosis (PAS and pro-fibrotic genes), the determination of de novo CD44 formation and its correlation with ERK1/2 pathway by immunohistochemistry (IH). We detected podocyte in the glomerulus by WT-1 IH and the localization of aPECS in the glomerular tuff by Claudin-1 and SSeCkS markers. Finally, we used isolated human kidney progenitor cells with and without CSF-1 treatment (n = 6/group) to identify potential key interactors of CSF-1 by RNAseq. We validated genes of interest in the FSGS experimental model. Results We observed a constitutively expression of CSF-1R in the glomerulus of control mice that significantly increased in ADR-treated mice, specifically in podocytes (WT1) and PECs (SSeCks), confirmed with mRNA expression. ADR-treated mice showed important events of sclerotic glomerulus and pro-fibrotic genes as collagen that was significantly reversed by the treatment with CSF-1R inhibitors (p<0.001). Results reflected a CSF-1R inhibitor-dependent renal function recovery with the use of the inhibitors with a reduction of proteinuria and an increase of glomerular filtration rate (p<0.001). We found a positive CD44 staining both in Bowman's capsule and inner the tuff of ADR-treated mice, accompanied by an increase of ERK1/2 activation. CSF-1R inhibitors significantly reduced the percentage of glomeruli with de novo CD44 production. Remarkably, podocyte depletion was also preserved with very similar levels to non-treated animals (p<0.001). For RNAseq results, 227 differentially expressed genes (considering a criterion of a probability of differential expression >0.9 and a |M| > 1) were subjected to enrichment analysis. The top significant gene ontology terms were mainly involved with interferon-induced genes. Genes involved in this pathway were validated in the FSGS model, showing an increase in mice treated with ADR compared to controls and alleviated with CSF-1R inhibitors (p<0.001). Conclusion In this study we propose a novel therapeutic strategy to FSGS-associated pathology based on the inhibition of CSF1-R activity having an impact on reducing aPECs, glomerulosclerosis, proteinuria, improving renal function and preserving the podocyte-progenitor phenotype, thus, in podocyte preservation against damage.

Fibrogenesis is part of a normal protective response to tissue injury that can become irreversible and progressive, leading to fatal diseases. Senescent cells are a main driver of fibrotic diseases through their secretome, known as senescence-associated secretory phenotype (SASP). Here, we report that cellular senescence, and multiple types of fibrotic diseases in mice and humans are characterized by the accumulation of iron. We show that vascular and hemolytic injuries are efficient in triggering iron accumulation, which in turn can cause senescence and promote fibrosis. Notably, we find that senescent cells persistently accumulate iron, even when the surge of extracellular iron has subdued. Indeed, under normal conditions of extracellular iron, cells exposed to different types of senescence-inducing insults accumulate abundant ferritin-bound iron, mostly within lysosomes, and present high levels of labile iron, which fuels the generation of reactive oxygen species and the SASP. Finally, we demonstrate that detection of iron by magnetic resonance imaging might allow non-invasive assessment of fibrotic burden in the kidneys of mice and in patients with renal fibrosis. Our findings suggest that iron accumulation plays a central role in senescence and fibrosis, even when the initiating events may be independent of iron, and identify iron metabolism as a potential therapeutic target for senescence-associated diseases.

Chronic kidney disease (CKD) will become the fifth global cause of death by 2040, thus emphasizing the need to better understand the molecular mechanisms of damage and regeneration in the kidney. CKD predisposes to acute kidney injury (AKI) which, in turn, promotes CKD progression. This implies that CKD or the AKI-to-CKD transition are associated with dysfunctional kidney repair mechanisms. Current therapeutic options slow CKD progression but fail to treat or accelerate recovery from AKI and are unable to promote kidney regeneration. Unraveling the cellular and molecular mechanisms involved in kidney injury and repair, including the failure of this process, may provide novel biomarkers and therapeutic tools. We now review the contribution of different molecular and cellular events to the AKI-to-CKD transition, focusing on the role of macrophages in kidney injury, the different forms of regulated cell death and necroinflammation, cellular senescence and the senescence-associated secretory phenotype (SAPS), polyploidization, and podocyte injury and activation of parietal epithelial cells. Next, we discuss key contributors to repair of kidney injury and opportunities for their therapeutic manipulation, with a focus on resident renal progenitor cells, stem cells and their reparative secretome, certain macrophage subphenotypes within the M2 phenotype and senescent cell clearance.

Crescentic glomerulonephritis is a devastating autoimmune disease that without early and properly treatment may rapidly progress to end-stage renal disease and death. Current immunosuppressive treatment provides limited efficacy and an important burden of adverse events. Epigenetic drugs are a source of novel therapeutic tools. Among them, bromodomain and extraterminal domain (BET) inhibitors (iBETs) block the interaction between bromodomains and acetylated proteins, including histones and transcription factors. iBETs have demonstrated protective effects on malignancy, inflammatory disorders and experimental kidney disease. Recently, Gremlin-1 was proposed as a urinary biomarker of disease progression in human anti-neutrophil cytoplasmic antibody (ANCA)-associated crescentic glomerulonephritis. We have now evaluated whether iBETs could regulate Gremlin-1 in experimental anti-glomerular basement membrane nephritis induced by nephrotoxic serum (NTS) in mice, a model resembling human crescentic glomerulonephritis. In NTS-injected mice, the iBET JQ1 inhibited renal Gremlin-1 overexpression and diminished glomerular damage, restoring podocyte numbers. Chromatin immunoprecipitation assay demonstrated BRD4 enrichment of the Grem-1 gene promoter in injured kidneys, consistent with Gremlin-1 epigenetic regulation. Moreover, JQ1 blocked BRD4 binding and inhibited Grem-1 gene transcription. The beneficial effect of iBETs was also mediated by modulation of NOTCH pathway. JQ1 inhibited the gene expression of the NOTCH effectors Hes-1 and Hey-1 in NTS-injured kidneys. Our results further support the role for epigenetic drugs, such as iBETs, in the treatment of rapidly progressive crescentic glomerulonephritis.

Macrophages have mechanisms for eliminating cholesterol from cells. If excess cholesterol is not eliminated from the macrophages, then transformation into a foam cell may occur. Foam cells are a hallmark of the atherosclerotic lesions that contribute to the development and rupture of atherosclerotic plaques. Several in vitro and in vivo studies have shown changes in the macrophage phenotype and improved phagocytosis after the acquisition of functional mitochondria. However, the effect of mitochondrial transplantation on promoting phagocytosis and phenotypic changes in lipid-loaded macrophages leading to foam cells has not been studied. We aimed to prove that the transplantation of healthy mitochondria to highly cholesterol-loaded macrophages induces macrophage phagocytosis and reduces the macrophage shift towards foam cells. For this purpose, using a murine macrophage cell line, RAW264.7, we determined if mitochondria transplantation to 7-ketocholesterol (7-KC)-loaded macrophages reduced lipid accumulation and modified their phagocytic function. We evidenced that mitochondrial transplantation to 7-KC-loaded macrophages reestablished phagocytosis and reduced lipid content. In addition, CPT1a expression and anti-inflammatory cytokines were restored after mitochondrial transplantation. We have developed a potential therapeutic approach to restore foam cell functionality.

Phagocytosis is an inherent function of tissue macrophages for the removal of apoptotic cells and cellular debris during acute and chronic injury; however, the dynamics of this event during fibrosis development is unknown. We aim to prove that during the development of kidney fibrosis in the unilateral ureteral obstruction (UUO) model, there are some populations of macrophage with a reduced ability to phagocytose, and whether the infusion of a population of phagocytic macrophages could reduce fibrosis in the murine model UUO. For this purpose, we have identified the macrophage populations during the development of fibrosis and have characterized their phagocytic ability and their expression of CPT1a. Furthermore, we have evaluated the therapeutic effect of macrophages overexpressing CPT1a with high phagocytic skills. We evidenced that the macrophage population which exhibits high phagocytic ability (F4/80low-CD11b) in fibrotic animals decreases during the progression of fibrosis while the macrophage population with lower phagocytic ability (F4/80high-CD11b) in fibrotic conditions, conversely, increases and CPT1a macrophage cell therapy with a strengthening phagocytic ability is associated with a therapeutic effect on kidney fibrosis. We have developed a therapeutic approach to reduce fibrosis in the UUO model by enrichment of the kidney resident macrophage population with a higher proportion of exogenous phagocytic macrophages overexpressing CPT1a.

Chronic kidney disease (CKD) is increasing in most countries and kidney transplantation is the best option for those patients requiring renal replacement therapy. Therefore, there is a significant number of patients living with a functioning kidney allograft. However, progressive kidney allograft functional deterioration remains unchanged despite of major advances in the field. After the first post-transplant year, it has been estimated that this chronic allograft damage may cause a 5% graft loss per year. Most studies focused on mechanisms of kidney graft damage, especially on ischemia-reperfusion injury, alloimmunity, nephrotoxicity, infection and disease recurrence. Thus, therapeutic interventions focus on those modifiable factors associated with chronic kidney allograft disease (CKaD). There are strategies to reduce ischemia-reperfusion injury, to improve the immunologic risk stratification and monitoring, to reduce calcineurin-inhibitor exposure and to identify recurrence of primary renal disease early. On the other hand, control of risk factors for chronic disease progression are particularly relevant as kidney transplantation is inherently associated with renal mass reduction. However, despite progress in pathophysiology and interventions, clinical advances in terms of long-term kidney allograft survival have been subtle. New approaches are needed and probably a holistic view can help. Chronic kidney allograft deterioration is probably the consequence of damage from various etiologies but can be attenuated by kidney repair mechanisms. Thus, besides immunological and other mechanisms of damage, the intrinsic repair kidney graft capacity should be considered to generate new hypothesis and potential therapeutic targets. In this review, the critical risk factors that define CKaD will be discussed but also how the renal mechanisms of regeneration could contribute to a change chronic kidney allograft disease paradigm.

Abstract Background Pouchitis and Crohn′s-like disease of the pouch (CDP) can be refractory to conventional therapy. Evidence of biological therapy has been rarely reported in large patient cohorts. We explored the use and effectiveness of these therapies and compared the success of a second biologic after antiTNF failure. Methods This is a retrospective RESERVO study of the Spanish cohort of GETECCU, that included patients operated for ulcerative colitis, with pouch construction, and subsequent diagnosis of pouchitis, CDP or cuffitis second ECCO diagnostic criteria1. Patients treated with antiTNF, Vedolizumab and/or Ustekinumab were selected. Clinical effectiveness was evaluated at long-term. We defined clinical remission as returning to the previous stool frequency, no pain or defecatory urgency, clinical response as the improvement in these parameters without the achievement of remission and non-response as no change or worsening of these symptoms. We also compared the effectiveness of second biologic (antiTNF vs vedolizumab-ustekinumab) after antiTNF failure, using descriptive and comparative statistics. Results The cohort comprised 145 patients. Demographic and clinical characteristics are represented in Table 1. A total of 232 biologic therapies were indicated. Of the total cohort, 60 (41.3%), 21 (14.4%) and 6 (4.1%) used two, three and four lines, respectively. Biologics used were Infliximab (n=95), Adalimumab (n=69), Vedolizumab (n=35), Ustekinumab (n=26) and Golimumab (n=7). Therapy characteristics, clinical effectiveness, need for intensification, discontinuation, and therapy duration for each biological therapy are represented in Table 2. Global rates of clinical remission, response, non-response and loss of response to a first biologic were 21.8%, 27.5%, 21.1% and 29.6%. Female gender was the only factor associated with effectiveness to a first biologic in univariate analysis (OR 2.16, CI 1.08–4.32, p 0.027). There were no significant differences regarding efectiveness between type of pouch disorder (pouchitis vs CDP, 51.6 vs 47.6%, p 0.48) or biologic agents. Thirty-nine patients received a second biologic after prior antiTNF failure (28 a second antiTNF and 11 non-antiTNF: 6 Vedolizumab, 5 Ustekinumab). Basal characteristics in this subgroup showed no significant differences. Clinical response (21.4 vs 63.6%, p 0.02) and discontinuation therapy rates (82.2 vs 54.5 %, p 0.04) after 11 months showed a more favorable profile for non-antiTNF therapy. Conclusion Biologics represent an effective option in the management of pouchitis and Crohn′s like disease of the pouch. Despite our small sample size, non-antiTNF therapy could be the best option after antiTNF failure. 1Fernando Magro. J Crohns Colitis 2017; 11(6): 649–670.

Abstract Background Pouchitis and other inflammatory pouch diseases (IPD) are frequent in pouch-carrying patients operated for a previous diagnosis of ulcerative colitis. We evaluated characteristics and differences in therapeutic requirements between pouchitis, Crohn′s-like disease of the pouch (CDP) and cuffitis. Methods This is a retrospective and multicentric Spanish cohort of GETECCU (RESERVO Study), including pouch-carrying patients (operated 1995 to 2016) with previous ulcerative colitis, ileostomy closure and subsequent diagnosis of IPD (pouchitis, CDP or cuffitis), following ECCO diagnostic criteria1. Follow up extended to June 2020. Pouchitis was categorized attending current classifications. Use of medical and surgical therapies was collected and differences between pouchitis and CDP were analyzed using descriptive and comparative statistics. Results A total of 338 patients were included. Demographic and clinical characteristics are presented in Table 1. The most frequent IPD was pouchitis (n=258, 76%), followed by CDP (n=55, 16%) and cuffitis (n=25, 7.4%). Pouchitis was diagnosed at a median time of 27 (range 1–342) months. Prevalence according to pouchitis classification is presented in Figure 1. CDP was diagnosed at a median time of 77 (range 5–324) months, around 75% with a previous pouchitis diagnosis. Location of CDP (not mutually excludent) was pouch CDP (91%), 87% pre-pouch ileitis, and 41% perianal disease. Regarding behavior: 26 (47%) were inflammatory, 12 (22%) stricturing and 17 (31%) penetrating (8 rectovaginal fistulas). Cuffitis was diagnosed at a median time of 18 (range 1–219) months. Medical and surgical therapies used are shown in Figure 2. Immunosuppressants (58.2 vs 22.4%, p 0.001), biologics (74.5 vs 34.8%, p 0.0001), and surgery (41.8 vs 21.3%, p 0.003) were more used in CDP than in pouchitis. Conclusion Pouchitis and CDP are heterogeneous inflammatory pouch complications with a wide and high therapeutic requirement. CDP presents a later diagnosis and has higher therapeutic needs than pouchitis. 1. Fernando Magro, Paolo Gionchetti, Rami Eliakim et al, for the European Crohn’s and Colitis Organisation [ECCO], Third European Evidence-based Consensus on Diagnosis and Management of Ulcerative Colitis. Part 1: Definitions, Diagnosis, Extra-intestinal Manifestations, Pregnancy, Cancer Surveillance, Surgery, and Ileo-anal Pouch Disorders, J Crohns Colitis 2017; 11(6): 649–670.

Macrophages show remarkable phenotypic plasticity in response to environmental signals. Although it is generally less considered, cytoskeletal changes in macrophages influence their phenotype, including phagocytosis and secretion of soluble cytokines. Influenza virus NS1A-binding protein (Ivns1abp) belongs to the Kelch family of proteins that play a central role in actin cytoskeleton dynamics by directly associating with F-actin and by protecting against actin derangement. Due to its role in cytoskeleton preservation, the Ivns1abp gene might be a critical regulator of the macrophage phenotype and function under inflammatory conditions. In this study, we determine that the modulation of the Ivns1abp gene in macrophages could modify resistance to macrophages against inflammation and maintain functional phagocytosis. Our results indicate that inflammatory insults inhibit the Ivns1abp gene, whereby phagocytosis is inhibited and the ability of macrophages to induce proliferation and repair of damaged cells is compromised. Furthermore, our results show that inflammatory insults alter the activity of the transcription factor c-myc, a factor which directly modulates the expression of the Ivns1abp gene. In conclusion, this study demonstrates a central role of lvns1abp in promoting and preserving a reparative macrophage phenotype and resistance to this inflammatory environment.

Background: The effects of macrophage therapies on muscle regeneration and stem cell activation after injury remains unclear. This study aims to know the effect of macrophage therapies on muscle l regeneration and endogenous stem cell activation towards new muscle Methods: Adult male Swiss mice were subjected to an injury in the gastrocnemius, close to the myotendinous junction, using a 2-mm biopsy tube. Animals were assigned to the following groups: 1.- Injury; 2.- Injury+ clodronate. Macrophages were depleted 24 hours after injury by clodronate injection. 3. - Injury+ clodronate+ macrophage therapy. Macrophage depleted mice were treated with an intramuscularl injection of 1 million peritoneal macrophages modified with intermittent anoxia reoxygenation. Animals were sacrificed at 4, and 15 days after the injury, (n = 8 per study time). Gene expression of proliferating cell nuclear antigen(PCNA) and Ki67 as cell proliferating markers, mannose receptor Ecotype 1(MRC1) and Interleukin10(IL-10) as anti-inflammatory markers, PAX7, MYOD as stem cell abundance and activation markers were evaluated by RT-PCR. Immunofluorescence analysis of PAX7, MYOD and histological scores of regeneration were performed. Results: Macrophage depletion provoked an increase in anti-inflammation (IL-10, , MRC1), cell proliferation (Ki67, PCNA) and stem cell abundance(PAX7), indicating that during injury, endogenous macrophages are inducers of inflammation, anti-proliferation and inhibitors of stem cell abundanceAdoptive transfer of intermittent anoxia treated macrophages (M2 macrophages) to previously depleted animals increased cell proliferation (Ki67 and PCNA), stem cell activation (MyoD) and abundance (Pax7). Immunofluorescence revealed increases in positive PAX7 fluorescence, indicating that M2 are inducers of proliferation, anti-inflammation and stem cell proliferation and activation.. Conclusion: This study indicates that infusion of intermittent anoxia treated macrophages to injured muscle reduces inflammation, promotes cell proliferation and stem cell activation and proliferation, leading to muscle regeneration. Intermittent hypoxia/reoxygenation induced macrophages, promote muscle regeneration without the addition of any external inducer agent, which simplifies the process and should allow to obtain a safer regenerative product from a clinical point of view.

During the course of sepsis in critically ill patients, kidney dysfunction and damage are among the first events of a complex scenario toward multi-organ failure and patient death. Acute kidney injury triggers the release of lipocalin-2 (Lcn-2), which is involved in both renal injury and recovery. Taking into account that Lcn-2 binds and transports iron with high affinity, we aimed at clarifying if Lcn-2 fulfills different biological functions according to its iron-loading status and its cellular source during sepsis-induced kidney failure. We assessed Lcn-2 levels both in serum and in the supernatant of short-term cultured renal macrophages (MΦ) as well as renal tubular epithelial cells (TEC) isolated from either Sham-operated or cecal ligation and puncture (CLP)-treated septic mice. Total kidney iron content was analyzed by Perls' staining, while Lcn-2-bound iron in the supernatants of short-term cultured cells was determined by atomic absorption spectroscopy. Lcn-2 protein in serum was rapidly up-regulated at 6 h after sepsis induction and subsequently increased up to 48 h. Lcn-2-levels in the supernatant of TEC peaked at 24 h and were low at 48 h with no change in its iron-loading. In contrast, in renal MΦ Lcn-2 was low at 24 h, but increased at 48 h, where it mainly appeared in its iron-bound form. Whereas TEC-secreted, iron-free Lcn-2 was associated with renal injury, increased MΦ-released iron-bound Lcn-2 was linked to renal recovery. Therefore, we hypothesized that both the cellular source of Lcn-2 as well as its iron-load crucially adds to its biological function during sepsis-induced renal injury.

Background/Aims: Reversible unilateral ureteral obstruction (R-UUO) is a model of renal injury used to study the structural and functional recovery of the kidneys after relief of the obstruction. This model has a prominent potential for the study of inflammatory and immune processes, cellular and tissue regeneration. Here we sought to describe a model of renal injury and repair R-UUO in mice. Methods: Eight week-old C57BL/6J male mice were divided into 5 groups (n = 5 each): UUO day 1, 2, 3, 4 and 5. R-UUO was performed with a microvascular clamp. At day 3, the ureteral clamp was removed and nephrectomy of the contralateral kidney was performed. Mice were sacrificed 48 h afterwards (day 5). An extra group with unilateral nephrectomy without UUO was added. Wild type mice were used as controls. Blood and tissue samples were collected for creatinine, immunohistochemistry and kidney mRNA gene expression analysis. Results: In the analysis of the obstructed kidney, we observed acute kidney injury with creatinine that doubled its baseline value; histological signs of tubular damage; increased inflammatory response evaluated by F4/80 macrophage; upregulation of pro-inflammatory and pro-fibrotic cytokines such as IL-2, MCP-1, CD40 and TGF-β1 and increased α-smooth muscle actin staining and mild fibrosis. Once the clamp was removed, we observed the amelioration of the kidney function, pathological lesions and the inflammatory response. Conclusion: This R-UUO model is an easy, reproducible and reliable method to assess kidney recovery after obstructive uropathy. In this setting, the use of this model may help to a better understanding of the process of kidney repair.

At present, Lupus Nephritis (LN) is still awaiting a biomarker to better monitor disease activity, guide clinical treatment, and predict a patient’s long-term outcome. In the last decade, novel biomarkers have been identified to monitor the disease, but none have been incorporated into clinical practice. The transmembrane receptor neuropilin-1 (NRP-1) is highly expressed by mesangial cells and its genetic deletion results in proteinuric disease and glomerulosclerosis. NRP-1 is increased in kidney biopsies of LN. In this work we were interested in determining whether urinary NRP-1 levels could be a biomarker of clinical response in LN. Our results show that patients with active LN have increased levels of urinary NRP-1. When patients were divided according to clinical response, responders displayed higher urinary and tissue NRP-1 levels at the time of renal biopsy. Areas under the receiver operating characteristic curve, comparing baseline creatinine, proteinuria, urinary NRP-1, and VEGFA protein levels, showed NRP-1 to be an independent predictor for clinical response. In addition, in vitro studies suggest that NRP-1could promote renal recovery through endothelial proliferation and migration, mesangial migration and local T cell cytotoxicity. Based on these results, NRP-1 may be used as an early prognostic biomarker in LN.