Telomere dysfunction promotes cholangiocyte senescence and biliary fibrosis in primary sclerosing cholangitis
Nidhi Jalan-Sakrikar, … , Diana Jurk, Robert C. Huebert
Nidhi Jalan-Sakrikar, … , Diana Jurk, Robert C. Huebert
Published September 14, 2023
Citation Information: JCI Insight. 2023;8(20):e170320. https://doi.org/10.1172/jci.insight.170320.
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Research Article Gastroenterology Hepatology

Telomere dysfunction promotes cholangiocyte senescence and biliary fibrosis in primary sclerosing cholangitis

Abstract

Cellular senescence and biliary fibrosis are prototypical features of obliterative cholangiopathies, such as primary sclerosing cholangitis (PSC). Telomere dysfunction can lead to senescence either through telomere erosion or damaged telomeres. Our goal was to investigate a mechanistic relationship between telomere damage and biliary fibrosis in PSC. Telomere attrition was observed in the bile ducts of patients with PSC along with a reduction in telomerase reverse transcriptase (TERT) expression, compared with that in normal livers. Similarly, liver tissue from mouse models of biliary fibrosis showed telomere attrition with increased damage at telomeres measured as telomere-associated foci (TAF). Cellular models of senescence induction increased the TAF in cholangiocytes. This coincided with decreased TERT expression and increased senescence, which was rescued by modulating TERT levels. Epigenetic analysis revealed increased acquisition of repressive histone methylation at the TERT promoter, which correlated with decreased TERT transcription. Cholangiocyte-selective deletion of TERT in mice exacerbated fibrosis, whereas androgen therapy toward telomerase rescued liver fibrosis and liver function in a genetic mouse model of PSC. Our results demonstrate a mechanistic role for telomere dysfunction in cellular senescence and fibrosis that characterize PSC. This suggests that PSC may be, in part, a telomere biology disorder, and identifies TERT as a potential therapeutic target.

Authors

Nidhi Jalan-Sakrikar, Abid Anwar, Usman Yaqoob, Can Gan, Anthony B. Lagnado, Alexander Q. Wixom, Diana Jurk, Robert C. Huebert

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Figure 4

Cellular models of senescence reduce TERT in cholangiocytes.

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Cellular models of senescence reduce TERT in cholangiocytes. (A) RT-PCR ...
(A) RT-PCR analysis of HiBECs shows an approximately 3-fold increase in p21 gene transcription and a 0.5-fold decrease in the TERT transcript in irradiated (IRR) cells compared with control cells. *P < 0.01, **P < 0.001, paired, 2-tailed t test. All error bars are SEM; n = 5. (B) IB of p21 and TERT with GAPDH as the loading control in HiBECs 6 days after irradiation. Densitometry data reported in the bar graphs show increased p21 with a decrease in TERT upon irradiation. **P < 0.001, paired, 2-tailed t test. All error bars are SEM; n = 4. (C) Luciferase assay revealing decrease in TERT transcription in irradiated cells compared with controls cells transfected with luciferase-fused TERT promoter. *P < 0.01. All error bars are SEM; n = 3. (D) IB of HiBECs overexpressing TERT reveals a decrease in irradiation-induced p21 and γH2A.x. Densitometry demonstrates TERT overexpression preventing irradiation-induced DNA damage and increase in p21 expression. *P < 0.01. All error bars are SEM; n = 3. (E) Immuno-FISH for telomeres (red) and the DNA damage marker 53BP1 (green) in primary cholangiocytes reveals reduced DNA damage in cells transfected with TERT upon irradiation. (F) Western blotting of HiBECs exposed to irradiation showing rescue of TERT levels by danazol and reduced levels of DNA damage markers 53BP1 and γH2A.x, as well as of p21 compared with DMSO-treated cells with GAPDH as a loading control. Densitometry graphs confirm the increase in TERT levels with a concomitant decrease in the senescence marker p21. *P < 0.01, **P < 0.001, 1-way ANOVA followed by Tukey’s post-test. All error bars are SEM; n = 4.