PPARγ-dependent hepatic macrophage switching acts as a central hub for hUCMSCs-mediated alleviation of decompensated liver cirrhosis in rats

Abstract:Background: Decompensated liver cirrhosis (DLC), a terminal-stage complication of liver disease, is a major cause of morbidity and mortality in patients with hepatopathie. Human umbilical cord mesenchymal stem cell (hUCMSCs) therapy has emerged as a treatment novel alternative for the treatment of DLC. However, optimized therapy protocols and the associated mechanisms are not completely understood. Methods: We constructed a DLC rat model consistent with the typical clinical characteristics combined use of PB and CCL₄. By performing dynamic detection of liver morphology and function in rats for 11 weeks, the various disease characteristics of DLC and the therapeutic effect of hUCMSCs on DLC in experimental rats were fully investigated, according to ascites examination, histopathological and related blood biochemical analyses. Flow-cytometry analysis of rat liver, immunofluorescence and RT-qPCR were performed to examine the changes of liver immune microenvironment after hucMSCs treatment. RNA-seq analysis of liver and primary macrophages and hUCMSCs co-culture system in vitro were performed to explore possible signaling pathways. PPARγ antagonist, GW9662, and clodronate liposomes were used to inhibit PPAR activation and pre-exhaustion of macrophages in DLC rats’ liver respectively. Results: We found that changing of the two key issues, the frequency and initial phase of hUCMSCs infusion can affect the efficacy of hUCMSCs and the optimal hUCMSCs treatment schedule is once every week for three weeks at the early-stage of DLC progression, providing the best therapeutic effect in reducing mortality and ascites, and improving liver function in DLC rats. hUCMSCs treatment skewed the macrophage phenotype from M1-type to M2-type through activating PPARγ signaling pathway in liver, which was approved by primary macrophages and hUCMSCs co-culture system in vitro. Both inhibition of PPARγ activation with GW9662 and pre-exhaustion of macrophages in DLC rats’ liver abolished the regulation of hUCMSCs on macrophage polarization, thus attenuating the beneficial effect of hUCMSCs treatment in DLC rats. Conclusions: HUCMSCs treatment on DLC were attributed to the activation of the PPARγ signaling pathway in liver macrophages of DLC rats, which polarizes M1-type macrophages to M2-type, thus inhibiting inflammation and promoting the repair of damaged liver tissue. Our results about different infusion regimens comparison and mechanisms exploration provide a robust theoretical foundation for the future study design of Mesenchymal Stem Cells therapy on DLC.