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Abstract
Background/Aims We studied the role of lysyl oxidase-like 2 (LOXL2) in collagen crosslinking and hepatic progenitor cell (HPC) differentiation, and the therapeutic efficacy of a LOXL2-blocking monoclonal antibody on liver fibrosis progression/reversal in mice.
Methods Anti-LOXL2 antibody, control antilysyl oxidase antibody or placebo was administered during thioacetamide (TAA)-induced fibrosis progression or during recovery. Therapeutic efficacy in biliary fibrosis was tested in BALB/c.Mdr2−/− and 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed mice. Collagen crosslinking, fibrosis progression and reversal were assessed histologically and biochemically. HPC differentiation was studied in primary EpCAM(+) liver cells in vitro.
Results LOXL2 was virtually absent from healthy but strongly induced in fibrotic liver, with predominant localisation within fibrotic septa. Delayed anti-LOXL2 treatment of active TAA fibrosis significantly reduced collagen crosslinking and histological signs of bridging fibrosis, with a 53% reduction in morphometric collagen deposition. In established TAA fibrosis, LOXL2 inhibition promoted fibrosis reversal, with enhanced splitting and thinning of fibrotic septa, and a 45% decrease in collagen area at 4 weeks of recovery. In the Mdr2−/− and DDC-induced models of biliary fibrosis, anti-LOXL2 antibody similarly achieved significant antifibrotic efficacy and suppressed the ductular reaction, while hepatocyte replication increased. Blocking LOXL2 had a profound direct effect on primary EpCAM(+) HPC behaviour in vitro, promoting their differentiation towards hepatocytes, while inhibiting ductal cell lineage commitment.
Conclusions LOXL2 mediates collagen crosslinking and fibrotic matrix stabilisation during liver fibrosis, and independently promotes fibrogenic HPC differentiation. By blocking these two convergent profibrotic pathways, therapeutic LOXL2 inhibition attenuates both parenchymal and biliary fibrosis and promotes fibrosis reversal.
- CIRRHOSIS
- HEPATITIS
- HEPATIC FIBROSIS
- PRIMARY BILIARY CIRRHOSIS
- PRIMARY SCLEROSING CHOLANGITIS
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Footnotes
Contributors NI performed most experiments, analysed data and wrote the manuscript. Z-WP and SY performed oval cell characterisation and some animal experiments. SBL and DYS performed mouse breeding and genotyping, assisted with animal experiments and assays. AMV performed immunohistochemistry and connective tissue square morphometry. DS and VS provided experimental tools and critically revised the manuscript. YVP designed the experiments, analysed data, supervised the study and wrote the manuscript.
Funding This study was supported in part by a research grant from Gilead Sciences, and an institutional grant from Department of Medicine (BIDMC) to YVP. NI was supported by a fellowship award from the Uehara Memorial Foundation and Z-WP was a recipient of career development awards from The First Affiliated Hospital of Sun Yat-sen University (Guangzhou, China), National Natural Science Foundation of China (81301842) and Pearl River S&T Nova Program (2014J2200087).
Competing interests AM-V and VS are employees of Gilead Sciences which develops anti-LOXL2 antibody and holds related patents. YVP received research funding from Gilead Sciences.
Provenance and peer review Not commissioned; externally peer reviewed.