Dendritic Cells Regulate Treg-Th17 Axis in Obstructive Phase of Bile Duct Injury in Murine Biliary Atresia

The role of extracellular vesicles in cholangiocarcinoma tumor microenvironment

Cholangiocarcinoma (CCA) is a highly aggressive malignant tumor that originates from the biliary system. With restricted treatment options at hand, the challenging aspect of early CCA diagnosis leads to a bleak prognosis. Besides the intrinsic characteristics of tumor cells, the generation and progression of CCA are profoundly influenced by the tumor microenvironment, which engages in intricate interactions with cholangiocarcinoma cells. Of notable significance is the role of extracellular vesicles as key carriers in enabling communication between cancer cells and the tumor microenvironment. This review aims to provide a comprehensive overview of current research examining the interplay between extracellular vesicles and the tumor microenvironment in the context of CCA. Specifically, we will emphasize the significant contributions of extracellular vesicles in molding the CCA microenvironment and explore their potential applications in the diagnosis, prognosis assessment, and therapeutic strategies for this aggressive malignancy.

Single-cell and spatial transcriptomics reveal the fibrosis-related immune landscape of biliary atresia

BACKGROUND

Biliary atresia (BA) is a devastating inflammatory and fibrosing cholangiopathy of neonates with unknown aetiology. We aim to investigate the relationship between these two main characteristics.

METHODS

Single-cell RNA sequencing and spatial transcriptomics were performed on liver samples from a cohort of 14 objects (BA: n = 6; control: n = 8). We conducted data integration and cell-type annotation based on gene expression profiling. Furthermore, we identified fibrosis-related immune cells according to their spatial locations, GO and KEGG analysis. Finally, SPOTlight and CIBERSORTx were used to deconvolute ST data and microarray data of the GSE46960 cohorts, respectively.

RESULTS

Immune subpopulations inhabiting the 'fibrotic niche' (areas of scarring), comprising 'intermediate' CD14⁺⁺ CD16⁺ monocytes, scar-associated macrophages, natural killer T cells, transitional B cells and FCN3⁺ neutrophils were identified. GO and KEGG analyses showed that pathways including 'positive regulation of smooth muscle cell/fibroblast proliferation' and 'positive regulation of/response to VEGFR/VEGF/EGFR/FGF' were enriched in these cell types. Interactions analysis showed that communication among 'FGF_FGFR', 'RPS19-C5AR1', 'CD74_COPA/MIF/APP' and 'TNFRSF1A/B_GRN' was extensive. Finally, the results of deconvolution for ST data and microarray data validated that the proportions of certain identified fibrosis-related cell types we identified were increased in BA.

DISCUSSION

Fibrosis is an important feature of BA, in which the immune system plays an important role. Our work reveals the subpopulations of immune cells enriched in the fibrotic niche of BA liver, as well as key related pathways and molecules; some are highlighted for the first time in liver fibrosis. These newly identified interactions might partly explain why the rate of liver fibrosis occurs much faster in BA than in other liver diseases.

CONCLUSION

Our study revealed the molecular, cellular and spatial immune microenvironment of the fibrotic niche of BA.

Hepatic Ly6CLo Non-Classical Monocytes Have Increased Nr4a1 (Nur77) in Murine Biliary Atresia

Biliary atresia (BA) is a rapidly progressive perinatal inflammatory disease, resulting in liver failure. Hepatic Ly6CLo non-classical monocytes promote the resolution of perinatal liver inflammation during rhesus rotavirus-mediated (RRV) BA in mice. In this study, we aim to investigate the effects of inflammation on the transcription factor Nr4a1, a known regulator of non-classical monocytes. Nr4a1-GFP reporter mice were injected with PBS for control or RRV within 24 h of delivery to induce perinatal liver inflammation. GFP expression on myeloid immune populations in the liver and bone marrow (BM) was quantified 3 and 14 days after injection using flow cytometry. Statistical significance was determined using a student’s t-test and ANOVA, with a p-value < 0.05 for significance. Our results demonstrate that non-classical monocytes in the neonatal liver exhibit the highest mean fluorescence intensity (MFI) of Nr4a1 (Ly6CLo MFI 6344 vs. neutrophils 3611 p < 0.001; macrophages 2782; p < 0.001; and Ly6CHi classical monocytes 4485; p < 0.0002). During inflammation, hepatic Ly6CLo non-classical monocytes showed a significant increase in Nr4a1 expression intensity from 6344 to 7600 (p = 0.012), while Nr4a1 expression remained unchanged on the other myeloid populations. These findings highlight the potential of using Nr4a1 as a regulator of neonatal hepatic Ly6CLo non-classical monocytes to mitigate perinatal liver inflammation.

Update on Etiology and Pathogenesis of Biliary Atresia

Biliary atresia is a rare inflammatory sclerosing obstructive cholangiopathy that initiates in infancy as complete choledochal blockage and progresses to the involvement of intrahepatic biliary epithelium. Growing evidence shows that biliary atresia is not a single entity with a single etiology but a phenotype resulting from multifactorial events whose common path is obliterative cholangiopathy. The etiology of biliary atresia has been explained as resulting from genetic variants, toxins, viral infection, chronic inflammation or bile duct lesions mediated by autoimmunity, abnormalities in the development of the bile ducts, and defects in embryogenesis, abnormal fetal or prenatal circulation and susceptibility factors. It is increasingly evident that the genetic and epigenetic predisposition combined with the environmental factors to which the mother is exposed are potential triggers for biliary atresia. There is also an indication that a progressive thickening of the arterial middle layer occurs in this disease, suggestive of vascular remodeling and disappearance of the interlobular bile ducts. It is suggested that the hypoxia/ischemia process can affect portal structures in biliary atresia and is associated with both the extent of biliary proliferation and the thickening of the medial layer.

ANKRD1 and SPP1 as diagnostic markers and correlated with immune infiltration in biliary atresia

The diagnosis of biliary atresia (BA) remains a clinical challenge, reliable biomarkers that can easily distinguish BA and other forms of intrahepatic cholestasis (IC) are urgently needed.Differentially expressed genes were identified by R software. The least absolute shrinkage and selection operator regression and support vector machine algorithms were used to filter the diagnostic biomarkers of BA. The candidate biomarkers were further validated in another independent cohort of patients with BA and IC. Then CIBERSORT was used for estimating the fractions of immune cell types in BA. Gene set enrichment analyses were conducted and the correlation between diagnostic genes and immune cells was analyzed.A total of 419 differentially expressed genes in BA were detected and 2 genes (secreted phosphoprotein 1 [SPP1] and ankyrin repeat domain [ANKRD1]) among them were selected as diagnostic biomarkers. The SPP1 yielded an area under the curve (AUC) value of 0.798 (95% confidence interval [CI]: 0.742-0.854) to distinguish patients with BA from those with IC, and ANKRD1 exhibited AUC values of 0.686 (95% CI: 0.616-0.754) in discriminating BA patients and those with IC. Further integrating them into one variable resulted in a higher AUC of 0.830 (95% CI: 0.777-0.879). The regulatory T cells, M2 macrophages cells, CD4 memory T cells, and dendritic cells may be involved in the BA process. The ANKRD1 and SPP1 was negatively correlated with regulatory T cells.In conclusion, the ANKRD1 and SPP1 could potentially provide extra guidance in discriminating BA and IC. The immune cell infiltration of BA gives us new insight to explore its pathogenesis.

An insight into the mechanism and molecular basis of dysfunctional immune response involved in cholestasis

Cholestasis is one of the most common clinical symptom of liver diseases. If patients do not receive effective treatment, cholestasis can evolve into liver fibrosis, cirrhosis and ultimately liver failure requiring liver transplantation. Currently, only ursodeoxycholic acid, obeticholic acid and bezafibrate are FDA-approved drugs, thereby requiring a breakthrough in new mechanisms and therapeutic development. Inflammation is one of the common complications of cholestasis. Hepatic accumulation of toxic hydrophobic bile acids is a highly immunogenic process involving both resident and immigrating immune cells. And the resulting inflammation may further aggravate hepatocyte injury. Though, great investigations have been made in the immune responses during cholestasis, the relationship between immune responses and cholestasis remains unclear. Moreover, scarce reviews summarize the immune responses during cholestasis and the efficacy of therapies on immune response. The main purpose of this paper is to review the existing literature on dysfunctional immune response during cholestasis and the effect of treatment on immune response which may provide an insight for researchers and drug development.

Regulation of bile duct epithelial injury by hepatic CD71+ erythroid cells

Extramedullary hematopoietic cells are present in the liver of normal neonates in the first few days of life and persist in infants with biliary atresia. Based on a previous report that liver genes are enriched by erythroid pathways, we examined the liver gene expression pattern at diagnosis and found the top 5 enriched pathways are related to erythrocyte pathobiology in children who survived with the native liver beyond 2 years of age. Using immunostaining, anti-CD71 antibodies identified CD71+ erythroid cells among extramedullary hematopoietic cells in the livers at the time of diagnosis. In mechanistic experiments, the preemptive antibody depletion of hepatic CD71+ erythroid cells in neonatal mice rendered them resistant to rhesus rotavirus-induced (RRV-induced) biliary atresia. The depletion of CD71+ erythroid cells increased the number of effector lymphocytes and delayed the RRV infection of livers and extrahepatic bile ducts. In coculture experiments, CD71+ erythroid cells suppressed the activation of hepatic mononuclear cells. These data uncover an immunoregulatory role for CD71+ erythroid cells in the neonatal liver.

CD40 up-regulation on dendritic cells correlates with Th17/Treg imbalance in chronic periodontitis in young population

We aimed to discover the influence of age on the development of chronic periodontitis and illustrate the molecular mechanism in this process. Blood samples were collected from 63 chronic periodontitis patients and 30 healthy controls. Th17 cell/Foxp3⁺ regulatory T cell (Treg) ratio and expression of costimulatory molecules in dendritic cells (DCs) were analyzed by flow cytometry. The serum levels of soluble CD40 ligand (CD40L) and IL-17 were examined by ELISA. In young chronic periodontitis patients, the Th17/Treg ratio was significantly higher than that in old patients. CD40 on DCs and serum levels of CD40L and IL-17 were all higher in young chronic periodontitis patients. Mature DCs with high CD40 expression level elevated the Th17/Treg ratio in vitro. During the pathogenesis of chronic periodontitis, young patients had higher Th17/Treg ratio than old patients and this phenomenon was in line with the differential expression levels of CD40 in DCs.

CD4+T Cell Subset Profiling in Biliary Atresia Reveals ICOS- Regulatory T Cells as a Favorable Prognostic Factor

Biliary atresia (BA) is a destructive pediatric liver disease and CD4+T cell activation is demonstrated to play an important role in BA. However, a comprehensive scenario regarding the involvement of CD4+T cell subsets to the development of BA remains unclear. Here, we aim to explore the infiltration of CD4+T cell subsets and their clinical significance in BA. In the present study, thirty BA liver samples were collected during surgery and were divided into good (BA1, n = 16) and poor prognosis (BA2, n = 14), with samples from choledochal cyst patients (n = 8) as control. By using multiplex immunohistochemistry, we evaluated the infiltration level of CD4+T cell subsets in the portal areas. RT-qPCR and flow cytometry were further applied to explore detailed features of Treg subsets. We revealed that hepatic infiltrating Th1, Th2, Th17, and ICOS+Treg cells were significantly increased in BA patients compared to controls and were negatively associated with prognosis, while high infiltrating ICOS-Tregs showed a favorable outcome. Phenotypic analysis indicated that, in contrast to ICOS+Tregs, ICOS-Tregs were mainly CD45RAhiCD45ROlow, and preferentially expressed more CD73. Besides, RT-qPCR revealed elevated expression of CD25, CD73, TGF-β, and BCL-2 genes in ICOS-Tregs. Finally, functional assay confirmed that ICOS-Tregs had a higher suppressive capacity to cytokine secretion and were more resistant to apoptosis in vitro. Collectively, we demonstrate that a mixed immune response is involved in BA pathogenesis, and the globally enhanced effector CD4+T cell response is associated with unfavorable prognosis, highly suppressive ICOS-Tregs is a protective factor and may serve an important reference to predict prognosis.

The T-helper cells 17 instead of Tregs play the key role in acute rejection after pediatric liver transplantation

Th17 and imbalance of Treg/Th17 might be one of the mechanisms of acute rejection. We aim to explore the role of Th17s in the balance of Treg/Th17 in acute rejection after LT in children diagnosed with BA. The ratios of Treg and Th17 in peripheral blood were detected by flow cytometry pre-LT, post-LT, and when rejection occurred. Treg proportion was higher before transplantation than at 2 weeks and 1 month after transplantation, with no statistical difference between 2 weeks and 1 month. However, Treg proportions were lower in pediatric recipients than healthy controls. The proportion of Tregs before anti-rejection treatment was lower than control group, with no statistical difference compared to the stable group and it showed no difference compared with that at 2 weeks and 1 month post-LT. The Th17 proportions were higher at 2 weeks and 1 month after transplantation than healthy controls. The Th17 proportion under the circumstances of rejection was higher than that in the stable group and control group; the proportion in stable group was higher than that in control group. After anti-rejection therapy, the proportions of Th17 were lower than those before therapy. In conclusion, the imbalance of Treg/Th17, especially Th17s instead of Tregs, may be one of the important mechanisms in acute rejection.

Regulation of epithelial injury and bile duct obstruction by NLRP3, IL-1R1 in experimental biliary atresia

BACKGROUND & AIMS

Biliary atresia (BA) results from a neonatal inflammatory and fibrosing obstruction of bile ducts of unknown etiology. Although the innate immune system has been linked to the virally induced mechanism of disease, the role of inflammasome-mediated epithelial injury remains largely undefined. Here, we hypothesized that disruption of the inflammasome suppresses the neonatal proinflammatory response and prevents experimental BA.

METHODS

We determined the expression of key inflammasome-related genes in livers from infants at diagnosis of BA and in extrahepatic bile ducts (EHBDs) of neonatal mice after infection with rotavirus (RRV) immediately after birth. Then, we determined the impact of the wholesale inactivation of the genes encoding IL-1R1 (Il1r1^-/-), NLRP3 (Nlrp3^-/-) or caspase-1 (Casp1^-/-) on epithelial injury and bile duct obstruction.

RESULTS

IL1R1, NLRP3 and CASP1 mRNA increased significantly in human livers at the time of diagnosis, and in EHBDs of RRV-infected mice. In Il1r1^-/- mice, the epithelial injury of EHBDs induced by RRV was suppressed, with dendritic cells unable to activate natural killer cells. A similar protection was observed in Nlrp3^-/- mice, with decreased injury and inflammation of livers and EHBDs. Long-term survival was also improved. In contrast, the inactivation of the Casp1 gene had no impact on tissue injury, and all mice died. Tissue analyses in Il1r1^-/- and Nlrp3^-/- mice showed decreased populations of dendritic cells and natural killer cells and suppressed expression of type-1 cytokines and chemokines.

CONCLUSIONS

Genes of the inflammasome are overexpressed at diagnosis of BA in humans and in the BA mouse model. In the experimental model, the targeted loss of IL-1R1 or NLRP3, but not of caspase-1, protected neonatal mice against RRV-induced bile duct obstruction.

LAY SUMMARY

Biliary atresia is a severe inflammatory and obstructive disease of bile ducts occurring in infancy. Although the cause is unknown, activation of the innate and adaptive immune systems injures the bile duct epithelium. In this study we found that patients' livers had increased expression of inflammasome genes. Using mice engineered to inactivate individual inflammasome genes, the epithelial injury and bile duct obstruction were prevented by the loss of Il1r1 or Nlrp3, with a decreased activation of natural killer cells and expression of cytokines and chemokines. In contrast, the loss of Casp1 did not change the disease phenotype. Combined, the findings point to a differential role of inflammasome gene products in the pathogenic mechanisms of biliary atresia.

Foxp3 promoter methylation impairs suppressive function of regulatory T cells in biliary atresia

Biliary atresia (BA) is characterized by progressive inflammation of the biliary system leading to liver cirrhosis, necessitating liver transplantation in pediatric patients. Various cell types have been reported to participate in the proinflammatory response in rhesus rotavirus (RRV)-induced BA mouse models, including T helper (Th) 1, Th2, Th17, CD8⁺ T cells, and natural killer cells. The immune suppressive regulatory T (Treg) cells, on the contrary, were reported not to function properly. The underlying mechanism is largely unknown. Focusing on the impaired suppressive function of Treg, we found methylation status of CpG islands within the Foxp3 promoter region of Treg cells in BA patients and murine models were both increased. Moreover, by injecting 5-aza-2'-deoxycytidine (Aza) as DNA-methylation inhibitor to RRV-infected mice, BA phenotypes were alleviated. Furthermore, Treg cells isolated from "RRV+Aza"-injected mice had better suppressive function than Treg cells from mice injected with RRV only, both in vivo and ex vivo. Thus we concluded that aberrant increased methylation status of "Foxp3 promoter" in Treg cells leads to impaired Treg suppressive function, exacerbating inflammatory injury in BA.

Absence of Maternal Microchimerism in Regional Lymph Nodes of Children With Biliary Atresia

OBJECTIVE

Maternal lymphocytes have been cited as a potential cause of infantile biliary atresia (BA). When hepatoportoenterostomy is performed, locoregional lymphadenopathy is frequently encountered.

METHODS

We screened enlarged nodes from 6 consecutive nonsyndromatic BA patients (age: 68 days ± 18.9 days) for maternal elements using DNA fingerprinting with short tandem repeat analysis and quantitative real-time polymerase chain reaction for allelic (single nucleotide) sequence polymorphisms.

RESULTS

Although being partly positive in infants' peripheral blood, no maternal microchimerism could be demonstrated in any of the lymph nodes.

CONCLUSION

This result challenges the hypothesis that maternal cells play a role in hilar lymphadenopathy of children with BA.

Effect of Adoptive Transfer or Depletion of Regulatory T Cells on Triptolide-induced Liver Injury

Objective: The aim of this study is to clarify the role of regulatory T cell (Treg) in triptolide (TP)-induced hepatotoxicity.

Methods: Female C57BL/6 mice received either adoptive transfer of Tregs or depletion of Tregs, then underwent TP administration and were sacrificed 24 h after TP administration. Liver injury was determined according to alanine transaminase (ALT) and aspartate transaminase (AST) levels in serum and histopathological change in liver tissue. Hepatic frequencies of Treg cells and the mRNA expression levels of transcription factor Forkhead box P3 and retinoid orphan nuclear receptor γt (RORγt), interleukin-10 (IL-10), suppressor of cytokine signaling (SOCS), and Notch/Notch ligand were investigated.

Results: During TP-induced liver injury, hepatic Treg and IL-10 decreased, while T helper 17 cells cell-transcription factor RORγt, SOCS and Notch signaling increased, accompanied with liver inflammation. Adoptive transfer of Tregs ameliorated the severity of TP-induced liver injury, accompanied with increased levels of hepatic Treg and IL-10. Adoptive transfer of Tregs remarkably inhibited the expression of RORγt, SOCS3, Notch1, and Notch3. On the contrary, depletion of Treg cells in TP-administered mice resulted in a notable increase of RORγt, SOCS1, SOCS3, and Notch3, while the Treg and IL-10 of liver decreased. Consistent with the exacerbation of liver injury, higher serum levels of ALT and AST were detected in Treg-depleted mice.

Conclusion: These results showed that adoptive transfer or depletion of Tregs attenuated or aggravated TP-induced liver injury, suggesting that Tregs could play important roles in the progression of liver injury. SOCS proteins and Notch signaling affected Tregs, which may contribute to the pathogenesis of TP-induced hepatotoxicity.