Clinical Course and Genetic Susceptibility of Primary Biliary Cirrhosis: Analysis of a Prospective Cohort

New insights on the role of human leukocyte antigen complex in primary biliary cholangitis

Primary Biliary Cholangitis (PBC) is a rare autoimmune cholangiopathy. Genetic studies have shown that the strongest statistical association with PBC has been mapped in the human leukocyte antigen (HLA) locus, a highly polymorphic area that mostly contribute to the genetic variance of the disease. Furthermore, PBC presents high variability throughout different population groups, which may explain the different geoepidemiology of the disease. A major role in defining HLA genetic contribution has been given by genome-wide association studies (GWAS) studies; more recently, new technologies have been developed to allow a deeper understanding. The study of the altered peptides transcribed by genetic alterations also allowed the development of novel therapeutic strategies in the context of immunotolerance. This review summarizes what is known about the immunogenetics of PBC with a focus on the HLA locus, the different distribution of HLA alleles worldwide, and how HLA modifications are associated with the pathogenesis of PBC. Novel therapeutic strategies are also outlined.

Genetic association of E26 transformation specific sequence 1 polymorphisms with the susceptibility of primary biliary cholangitis in China

Primary biliary cholangitis (PBC) is a chronic and cholestatic liver disease characterized by an autoimmune-mediated destruction of intrahepatic bile ducts. E26 transformation specific sequence 1 (ETS-1) is a transcription factor regulating the expression of various immune-related genes. The aim of our study was to identify the associations between the gene polymorphisms of ETS-1 with the susceptibility and clinical characteristics of PBC in Chinese Han population. Three single nucleotide polymorphisms (rs4937333, rs11221332 and rs73013527) of ETS-1 were selected based on relevant studies. Genotyping was executed with polymerase chain reaction-high resolution melting (PCR-HRM) assay. SNP rs4937333 of ETS-1 was prominent correlation with the susceptibility of PBC (P = 0.007, OR = 1.44, 95%CI = 1.10–1.88). For rs4937333, PBC patients carrying the allele T assumed high-level TP (P = 0.020), and homozygous genotype TT assumed low-level RDW (P = 0.033). For rs11221332, PBC patients carrying the allele T assumed high-level TP and HDLC (P = 0.004, P = 0.015, respectively). For rs73013527, PBC patients carrying the allele T assumed low-level PLT (P = 0.002), and homozygous genotype TT assumed high-level RDW (P = 0.021). In conclusion, Gene polymorphisms of ETS-1 present relevant with the susceptibility of PBC, and affect the expression of TP, HDLC, PLT and RDW concentrations in patients with PBC.

Integrative omics analysis identifies macrophage migration inhibitory factor signaling pathways underlying human hepatic fibrogenesis and fibrosis

The genetic basis underlying liver fibrosis remains largely unknown. We conducted a study to identify genetic alleles and underlying pathways associated with hepatic fibrogenesis and fibrosis at the genome-wide level in 121 human livers. By accepting a liberal significance level of P<1e-4, we identified 73 and 71 candidate loci respectively affecting the variability in alpha-smooth muscle actin (α-SMA) levels (fibrogenesis) and total collagen content (fibrosis). The top genetic loci associated with the two markers were BAZA1 and NOL10 for α-SMA expression and FAM46A for total collagen content (P<1e-6). We further investigated the relationship between the candidate loci and the nearby gene transcription levels (cis-expression quantitative trait loci) in the same liver samples. We found that 44 candidate loci for α-SMA expression and 44 for total collagen content were also associated with the transcription of the nearby genes (P<0.05). Pathway analyses of these genes indicated that macrophage migration inhibitory factor (MIF) related pathway is significantly associated with fibrogenesis and fibrosis, though different genes were enriched for each marker. The association between the single nucleotide polymorphisms, MIF and α-SMA showed that decreased MIF expression is correlated with increased α-SMA expression, suggesting that variations in MIF locus might affect the susceptibility of fibrogenesis through controlling MIF gene expression. In summary, our study identified candidate alleles and pathways underlying both fibrogenesis and fibrosis in human livers. Our bioinformatics analyses suggested MIF pathway as a strong candidate involved in liver fibrosis, thus further investigation for the role of the MIF pathway in liver fibrosis is warranted. The study was reviewed and approved by the Institutional Review Board (IRB) of Wayne State University (approval No. 201842) on May 17, 2018.

Increased Waitlist Mortality and Lower Rate for Liver Transplantation in Hispanic Patients With Primary Biliary Cholangitis

BACKGROUND & AIMS

Data on the differences in ethnicity and race among patients with primary biliary cholangitis (PBC) awaiting liver transplantation (LT) are limited. We evaluated liver transplant waitlist trends and outcomes based on ethnicity and race in patients with PBC in the United States.

METHODS

Using the United Network for Organ Sharing (UNOS) registry, we collected data on patients with PBC on the liver transplant waitlist, and performed analysis with a focus on ethnicity and race-based variations clinical manifestations, waitlist mortality and LT rates from 2000 to 2014. Outcomes were adjusted for demographics, complications of portal hypertension, and Model for End-stage Liver Disease score at time of waitlist registration.

RESULTS

Although the number of white PBC waitlist registrants and additions decreased from 2000 to 2014, there were no significant changes in the number of Hispanic PBC waitlist registrants and additions each year. The proportion of Hispanic patients with PBC on the liver transplant waitlist increased from 10.7% in 2000 to 19.3% in 2014. Hispanics had the highest percentage of waitlist deaths (20.8%) of any ethnicity or race evaluated. After adjusting for demographic and clinical characteristics, Hispanic patients with PBC had the lowest overall rate for undergoing LT (adjusted hazard ratio, 0.71; 95% CI, 0. 60-0.83; P < .001) and a significantly higher risk of death while on the waitlist, compared to whites (adjusted hazard ratio, 1.41; 95% CI, 1.15-1.74; P < .001). Furthermore, Hispanic patients with PBC had the highest proportion of waitlist removals due to clinical deterioration.

CONCLUSIONS

In an analysis of data from UNOS registry focusing on outcomes, we observed differences in rates of LT and liver transplant waitlist mortality of Hispanic patients compared with white patients with PBC. Further studies are needed to improve our understanding of ethnicity and race-based differences in progression of PBC.