Role Of Regulatory T Cells In Acute And Chronic Liver Injury

Part Ⅰ:Regulatory T Cells Induced after Liver Injury Play a Critical Role in Liver Wound HealingAim:To observe dynamic state of regulatory T cells (Tregs) in the course of acute liver injury and to investigate the role of Tregs in wound healing of liver injuryMethods:Acute liver injury was induced by thioacetamide (40mg/Kg, ip).This model was established with B6.Foxp3gfp-knockin mice. The population of Tregs in liver, blood and spleen was measured at definite time point after administration. The subset of Tregs before and after administration was analyzed. Depletion of Tregs was used to investigate the role of Tregs in wound healing of liver injury.Results:With the process of liver injury, the population of hepatic Tregs was reduced. However, during the period of wound healing, hepatic Tregs came back and at72hours after administration, the number of hepatic Tregs reached the base line level. By analyzing the subset of hepatic Tregs, induced Tregs contributed to the increase of hepatic Tregs at72hours after administration. Depletion of Tregs, which increased after administration, impaired the wound healing of liver injury.Conclusions:Tregs, which were induced in the period of liver wound healing, facilitated recovery of liver from acute injury. Part Ⅱ:Hepatic Stellate Cells Induce Regulatory T Cells Dependent on Matrix MetalloproteasesAim:To investigate the role of hepatic stellate cells (HSCs) in induction of regulatory T cells (Tregs) and the underlying mechanism. Methods:Acute liver injury was induced by Thioacetamide (40mg/Kg, ip). This model was established in MMP9-/-and MMP13-/-mice to exam the role of Matrix Metalloproteases (MMPs) in wounding healing of acute liver injury and hepatic Tregs induction. HSCs were cultured in3D gel to investigate the method and mechanism of induction of Tregs by HSCs.Results:Without MMP9or MMP13, the number of hepatic Tregs was failed to increase in liver wounding healing. Tregs were not induced by co-culture of HSCs and naive T cells in plastic dices. However, conditioned medium of HSCs cultured in3D gel had the ability to induce Tregs from naive T cells. In addition, this conditioned medium stabilized natural Tregs (nTregs) function and made them resistant to convent to Th17cells in the presence of IL-6.Conclusions:MMPs produced by active HSCs was critical for activation of TGFβ, which play an important role in induction of hepatic Tregs after liver injury. Additionally, retinoic acid released by active HSCs could sustain the stability and function of nTregs in an inflammatory milieu. Part Ⅲ:Immune Suppression in Fibrotic Liver are Mediated by Induced Regulatory T Cells which Safeguard Fibroplasias from ClearanceAim:To investigate the role of regulatory T cells (Tregs), which accumulated in fibrotic liver, in liver fibrosisMethods:Liver fibrosis was induced by Thioacetamide. The population of hepatic Tregs was measured after fibrosis was established. Inflammatory response in fibrotic liver was compared with normal liver under the challenge of hepatic toxin. Co-culture of Tregs and kupffer cells was used to exam the effect of Tregs on kupffer cells. Depletion of Tregs was adopted to investigate the role of Tregs in fibrotic liver inflammatory response and the effect of Tregs on liver fibrolysis.Results:Tregs were accumulated in liver after fibrosis, and the inflammatory response was suppressed in fibrotic liver. Depletion of Tregs promoted inflammatory responses, increased hepatic MMPs levels and facilitated liver fibrolysis. Furthermore, in vitro test indicated that Tregs had the ability of suppressing MMPs production by kupffer cells. Depletion of kupffer cells reduced MMPs levels in the presence of TAA and liver fibroplasias was safeguard.Conclusions:Tregs, which accumulated in fibrotic liver, suppressed inflammatory responses, especially reduced MMPs production by kupffer cells and safeguard liver fibroplasias from clearance.