Ischemic preconditioning in the liver is independent of regulatory T cell activity

Ischemic preconditioning (IPC) protects organs from ischemia reperfusion injury (IRI) through unknown mechanisms. Effector T cell populations have been implicated in the pathogenesis of IRI, and T regulatory cells (Treg) have become a putative therapeutic target, with suggested involvement in IPC. We explored the role of Treg in hepatic IRI and IPC in detail. IPC significantly reduced injury following ischemia reperfusion insults. Treg were mobilized rapidly to the circulation and liver after IRI, but IPC did not further increase Treg numbers, nor was it associated with modulation of circulating pro-inflammatory chemokine or cytokine profiles. We used two techniques to deplete Treg from mice prior to IRI. Neither Treg depleted FoxP3.LuciDTR mice, nor wildtyoe mice depleted of Tregs with PC61, were more susceptible to IRI compared with controls. Despite successful enrichment of Treg in the liver, by adoptive transfer of both iTreg and nTreg or by in vivo expansion of Treg with IL-2/anti-IL-2 complexes, no protection against IRI was observed.We have explored the role of Treg in IRI and IPC using a variety of techniques to deplete and enrich them within both the liver and systemically. This work represents an important negative finding that Treg are not implicated in IPC and are unlikely to have translational potential in hepatic IRI

Use of Renal Replacement Therapy May Influence Graft Outcomes following Liver Transplantation for Acute Liver Failure:A Propensity-Score Matched Population-Based Retrospective Cohort Study

INTRODUCTION:Acute kidney injury is associated with a poor prognosis in acute liver failure but little is known of outcomes in patients undergoing transplantation for acute liver failure who require renal replacement therapy. METHODS:A retrospective analysis of the United Kingdom Transplant Registry was performed (1 January 2001-31 December 2011) with patient and graft survival determined using Kaplan-Meier methods. Cox proportional hazards models were used together with propensity-score based full matching on renal replacement therapy use. RESULTS:Three-year patient and graft survival for patients receiving renal replacement therapy were 77.7% and 72.6% compared with 85.1% and 79.4% for those not requiring renal replacement therapy (P<0.001 and P = 0.009 respectively, n = 725). In a Cox proportional hazards model, renal replacement therapy was a predictor of both patient death (hazard ratio (HR) 1.59, 95% CI 1.01-2.50, P = 0.044) but not graft loss (HR 1.39, 95% CI 0.92-2.10, P = 0.114). In groups fully matched on baseline covariates, those not receiving renal replacement therapy with a serum creatinine greater than 175 μmol/L had a significantly worse risk of graft failure than those receiving renal replacement therapy. CONCLUSION:In patients being transplanted for acute liver failure, use of renal replacement therapy is a strong predictor of patient death and graft loss. Those not receiving renal replacement therapy with an elevated serum creatinine may be at greater risk of early graft failure than those receiving renal replacement therapy. A low threshold for instituting renal replacement therapy may therefore be beneficial

CSF1 Restores Innate Immunity Following Liver Injury in Mice and Serum Levels Indicate Outcomes of Patients With Acute Liver Failure

Background &#38; Aims: Liver regeneration requires functional liver macrophages, which provide an immune barrier that is compromised after liver injury. The numbers of liver macrophages are controlled by macrophage colony-stimulating factor (CSF1). We examined the prognostic significance of the serum level of CSF1 in patients with acute liver injury and studied its effects in mice. Methods: We measured levels of CSF1 in serum samples collected from 55 patients who underwent partial hepatectomy at the Royal Infirmary Edinburgh between December 2012 and October 2013, as well as from 78 patients with acetaminophen-induced acute liver failure admitted to the Royal Infirmary Edinburgh or the University of Kansas Medical Centre. We studied the effects of increased levels of CSF1 in uninjured mice that express wild-type CSF1 receptor or a constitutive or inducible CSF1-receptor reporter, as well as in chemokine receptor 2 (Ccr2)-/- mice; we performed fate-tracing experiments using bone marrow chimeras. We administered CSF1-Fc (fragment, crystallizable) to mice after partial hepatectomy and acetaminophen intoxication, and measured regenerative parameters and innate immunity by clearance of fluorescent microbeads and bacterial particles. Results: Serum levels of CSF1 increased in patients undergoing liver surgery in proportion to the extent of liver resected. In patients with acetaminophen-induced acute liver failure, a low serum level of CSF1 was associated with increased mortality. In mice, administration of CSF1-Fc promoted hepatic macrophage accumulation via proliferation of resident macrophages and recruitment of monocytes. CSF1-Fc also promoted transdifferentiation of infiltrating monocytes into cells with a hepatic macrophage phenotype. CSF1-Fc increased innate immunity in mice after partial hepatectomy or acetaminophen-induced injury, with resident hepatic macrophage as the main effector cells. Conclusions: Serum CSF1 appears to be a prognostic marker for patients with acute liver injury. CSF1 might be developed as a therapeutic agent to restore innate immune function after liver injury

Heme oxygenase system in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) limits access to transplantation. Heme oxygenase-1 (HO-1) is a powerful antioxidant enzyme which degrades free heme into biliverdin, free iron and carbon monoxide. HO-1 and its metabolites have the ability to modulate a wide variety of inflammatory disorders including hepatic IRI. Mechanisms of this protective effect include reduction of oxygen free radicals, alteration of macrophage and T cell phenotype. Further work is required to understand the physiological importance of the many actions of HO-1 identified experimentally, and to harness the protective effect of HO-1 for therapeutic potential

Univariable analysis of risk factors for patient death and graft loss after liver transplantation for acute liver failure.

<p>Hazard ratios were determined using Cox Proportional Hazards model. Values in parentheses are 95% confidence intervals.</p

Renal replacement therapy and survival in a matched dataset.

<p>Probability of patient (A) and graft survival (B) at one year following liver transplant by pre-operative serum creatinine level and RRT requirement in a matched dataset. In patients not receiving RRT, a pre-operative serum creatinine of greater than 175 μmol/L had a significantly greater risk of graft failure compared to those receiving RRT (C; black line indicates hazard ratio = 1, shaded areas represent 95% CI). Cox proportional hazards model with groups fully matched for baseline covariates used for each analysis.</p

Multivariable analysis of pre-operative risk factors for patient death and graft loss in those undergoing liver transplantation for acute liver failure.

<p>Cox Proportional Hazards model using variables found to be significant in univariable analysis (P<0.05) and those thought to be clinically significant. Serum creatinine was centred at a value of 90 μmol/L for the purposes of the analysis. Patient survival data was only considered for patients receiving their first liver transplantation. Values in parentheses are 95% confidence intervals.</p

The interaction between renal replacement therapy and elevated creatinine on patient and graft survival.

<p>Kaplan-Meier plots demonstrating the interaction between pre-operative creatinine concentration and requirement for RRT on patient (A) and graft survival (B); P value calculated using log-rank test. Probability of death at one year following liver transplant by pre-operative serum creatinine level, RRT and recipient age is shown for patient (C) and graft survival (D). Models use Cox proportional hazards, with co-variable patient characteristics adjusted to haemoglobin concentration of 10 g/dL, requirement of mechanical ventilation and absence of sepsis.</p