A new mouse model of radiation-induced liver disease reveals mitochondrial dysfunction as an underlying fibrotic stimulus

Nicolas Melin; Tural Yarahmadov; Daniel Sanchez-Taltavull; Fabienne E Birrer; Tess M Brodie; Benoît Petit; Andrea Felser; Jean-Marc Nuoffer; Matteo Montani; Marie-Catherine Vozenin; Evelyn Herrmann; Daniel Candinas; Daniel M Aebersold; Deborah Stroka

doi:10.1016/j.jhepr.2022.100508

A new mouse model of radiation-induced liver disease reveals mitochondrial dysfunction as an underlying fibrotic stimulus

JHEP Rep. 2022 May 21;4(7):100508. doi: 10.1016/j.jhepr.2022.100508. eCollection 2022 Jul.

Authors

Nicolas Melin^{1

2}, Tural Yarahmadov^{1

2}, Daniel Sanchez-Taltavull^{1

2}, Fabienne E Birrer^{1

2}, Tess M Brodie^{1

2}, Benoît Petit³, Andrea Felser⁴, Jean-Marc Nuoffer⁴, Matteo Montani⁵, Marie-Catherine Vozenin³, Evelyn Herrmann⁶, Daniel Candinas¹, Daniel M Aebersold⁶, Deborah Stroka^{1

2}

Affiliations

¹ Department of Visceral Surgery and Medicine, Inselspital, Bern University Hospital, University of Bern, Switzerland.
² Department for BioMedical Research, Visceral Surgery and Medicine, University of Bern, Switzerland.
³ Laboratory of Radiation Oncology, Radiation Oncology Service, Department of Oncology, CHUV, Lausanne University Hospital, University of Lausanne, Switzerland.
⁴ Institute of Clinical Chemistry, University of Bern, Switzerland.
⁵ Department of Pathology, University of Bern, Switzerland.
⁶ Department of Radiation Oncology, Department for BioMedical Research, University of Bern, Bern University Hospital, Switzerland.

Abstract

Background & aims: High-dose irradiation is an essential tool to help control the growth of hepatic tumors, but it can cause radiation-induced liver disease (RILD). This life-threatening complication manifests itself months following radiation therapy and is characterized by fibrosis of the pericentral sinusoids. In this study, we aimed to establish a mouse model of RILD to investigate the underlying mechanism of radiation-induced liver fibrosis.

Methods: Using a small animal image-guided radiation therapy platform, an irradiation scheme delivering 50 Gy as a single dose to a focal point in mouse livers was designed. Tissues were analyzed 1 and 6 days, and 6 and 20 weeks post-irradiation. Irradiated livers were assessed by histology, immunohistochemistry, imaging mass cytometry and RNA sequencing. Mitochondrial function was assessed using high-resolution respirometry.

Results: At 6 and 20 weeks post-irradiation, pericentral fibrosis was visible in highly irradiated areas together with immune cell infiltration and extravasation of red blood cells. RNA sequencing analysis showed gene signatures associated with acute DNA damage, p53 activation, senescence and its associated secretory phenotype and fibrosis. Moreover, gene profiles of mitochondrial damage and an increase in mitochondrial DNA heteroplasmy were detected. Respirometry measurements of hepatocytes in vitro confirmed irradiation-induced mitochondrial dysfunction. Finally, the highly irradiated fibrotic areas showed markers of reactive oxygen species such as decreased glutathione and increased lipid peroxides and a senescence-like phenotype.

Conclusions: Based on our mouse model of RILD, we propose that irradiation-induced mitochondrial DNA instability contributes to the development of fibrosis via the generation of excessive reactive oxygen species, p53 pathway activation and a senescence-like phenotype.

Lay summary: Irradiation is an efficient cancer therapy, however, its applicability to the liver is limited by life-threatening radiation-induced hepatic fibrosis. We have developed a new mouse model of radiation-induced liver fibrosis, that recapitulates the human disease. Our model highlights the role of mitochondrial DNA instability in the development of irradiation-induced liver fibrosis. This new model and subsequent findings will help increase our understanding of the hepatic reaction to irradiation and to find strategies that protect the liver, enabling the expanded use of radiotherapy to treat hepatic tumors.

Keywords: 4HNE, 4-hydroxynonenal; CV, central vein; ECM, extracellular matrix; ETC, electron transfer chain; GSH, reduced glutathione (glutathione); GSSG, oxidized glutathione (glutathione disulfide); HSCs, hepatic stellate cells; IGRT, image-guided radiation therapy; IHC, immunohistochemistry; IMC, imaging mass cytometry; MDA, malondialdehyde; RILD, radiation-induced liver disease; RNAseq, RNA sequencing; ROS; ROS, reactive oxygen species; RT, radiation therapy; SASP, senescence-associated secretory phenotype; SNP, single nucleotide polymorphism; SOS, sinusoidal obstruction syndrome; fibrosis; image guided radiation therapy (IGRT); mitochondrial dysfunction; mitochondrial-DNA; mouse model; mtDNA, mitochondrial DNA; mtROS, mitochondrial reactive oxygen species; p53; radiation-induced liver disease (RILD); rcf, relative centrifuge force; senescence; sinusoidal obstruction syndrome.