The intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury
Background & Aims: In vertebrates, canonical Hedgehog (Hh) pathway activation requires Smoothened (SMO) translocation to the primary cilium (Pc), followed by a GLI-mediated transcriptional response. In addition, a similar gene regulation occurs in response to growth factors/cytokines, although i...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Journal Article |
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Elsevier BV
2014
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| Online Access: | http://hdl.handle.net/20.500.11937/42482 |
| _version_ | 1848756431829860352 |
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| author | Grzelak, C. Martelotto, L. Sigglekow, N. Patkunanathan, B. Ajami, K. Calabro, S. Dwyer, Benjamin Tirnitz-Parker, Janina Watkins, D. Warner, F. Shackel, N. McCaughan, G. |
| author_facet | Grzelak, C. Martelotto, L. Sigglekow, N. Patkunanathan, B. Ajami, K. Calabro, S. Dwyer, Benjamin Tirnitz-Parker, Janina Watkins, D. Warner, F. Shackel, N. McCaughan, G. |
| author_sort | Grzelak, C. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Background & Aims: In vertebrates, canonical Hedgehog (Hh) pathway activation requires Smoothened (SMO) translocation to the primary cilium (Pc), followed by a GLI-mediated transcriptional response. In addition, a similar gene regulation occurs in response to growth factors/cytokines, although independently of SMO signalling. The Hh pathway plays a critical role in liver fibrosis/regeneration; however, the mechanism of activation in chronic liver injury is poorly understood. This study aimed to characterise Hh pathway activation upon thioacetamide (TAA)- induced chronic liver injury in vivo by defining Hh-responsive cells, namely cells harbouring Pc and Pc-localised SMO. Methods: C57BL/6 mice (wild-type or Ptc1+/_) were TAA-treated. Liver injury and Hh ligand/pathway mRNA and protein expression were assessed in vivo. SMO/GLI manipulation and SMO dependent/ independent activation of GLI-mediated transcriptional response in Pc-positive (Pc+) cells were studied in vitro. Results: In vivo, Hh activation was progressively induced following TAA. At the epithelial-mesenchymal interface, injured hepatocytes produced Hh ligands. Progenitors, myofibroblasts, leukocytes and hepatocytes were GLI2+. Pc+ cells increased following TAA, but only EpCAM+/GLI2+ progenitors were Pc+/SMO+. In vitro, SMO knockdown/hGli3-R overexpression reduced proliferation/viability in Pc+ progenitors, whilst increased proliferation occurred with hGli1 overexpression. HGF induced GLI transcriptional activity independently of Pc/SMO. Ptc1+/_ mice exhibited increased progenitor, myofibroblast and fibrosis responses. Conclusions: In chronic liver injury, Pc+ progenitors receive Hh ligand signals and process it through Pc/SMO-dependent activation of GLI-mediated transcriptional response. Pc/SMO-independent GLI activation likely occurs in Pc_/GLI2+ cells. Increased fibrosis in Hh gain-of-function mice likely occurs by primary progenitor expansion/proliferation and secondary fibrotic myofibroblast expansion, in close contact with progenitors. |
| first_indexed | 2025-11-14T09:12:06Z |
| format | Journal Article |
| id | curtin-20.500.11937-42482 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:12:06Z |
| publishDate | 2014 |
| publisher | Elsevier BV |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-424822019-02-19T05:35:17Z The intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury Grzelak, C. Martelotto, L. Sigglekow, N. Patkunanathan, B. Ajami, K. Calabro, S. Dwyer, Benjamin Tirnitz-Parker, Janina Watkins, D. Warner, F. Shackel, N. McCaughan, G. Background & Aims: In vertebrates, canonical Hedgehog (Hh) pathway activation requires Smoothened (SMO) translocation to the primary cilium (Pc), followed by a GLI-mediated transcriptional response. In addition, a similar gene regulation occurs in response to growth factors/cytokines, although independently of SMO signalling. The Hh pathway plays a critical role in liver fibrosis/regeneration; however, the mechanism of activation in chronic liver injury is poorly understood. This study aimed to characterise Hh pathway activation upon thioacetamide (TAA)- induced chronic liver injury in vivo by defining Hh-responsive cells, namely cells harbouring Pc and Pc-localised SMO. Methods: C57BL/6 mice (wild-type or Ptc1+/_) were TAA-treated. Liver injury and Hh ligand/pathway mRNA and protein expression were assessed in vivo. SMO/GLI manipulation and SMO dependent/ independent activation of GLI-mediated transcriptional response in Pc-positive (Pc+) cells were studied in vitro. Results: In vivo, Hh activation was progressively induced following TAA. At the epithelial-mesenchymal interface, injured hepatocytes produced Hh ligands. Progenitors, myofibroblasts, leukocytes and hepatocytes were GLI2+. Pc+ cells increased following TAA, but only EpCAM+/GLI2+ progenitors were Pc+/SMO+. In vitro, SMO knockdown/hGli3-R overexpression reduced proliferation/viability in Pc+ progenitors, whilst increased proliferation occurred with hGli1 overexpression. HGF induced GLI transcriptional activity independently of Pc/SMO. Ptc1+/_ mice exhibited increased progenitor, myofibroblast and fibrosis responses. Conclusions: In chronic liver injury, Pc+ progenitors receive Hh ligand signals and process it through Pc/SMO-dependent activation of GLI-mediated transcriptional response. Pc/SMO-independent GLI activation likely occurs in Pc_/GLI2+ cells. Increased fibrosis in Hh gain-of-function mice likely occurs by primary progenitor expansion/proliferation and secondary fibrotic myofibroblast expansion, in close contact with progenitors. 2014 Journal Article http://hdl.handle.net/20.500.11937/42482 10.1016/j.jhep.2013.08.012 Elsevier BV fulltext |
| spellingShingle | Grzelak, C. Martelotto, L. Sigglekow, N. Patkunanathan, B. Ajami, K. Calabro, S. Dwyer, Benjamin Tirnitz-Parker, Janina Watkins, D. Warner, F. Shackel, N. McCaughan, G. The intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury |
| title | The intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury |
| title_full | The intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury |
| title_fullStr | The intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury |
| title_full_unstemmed | The intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury |
| title_short | The intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury |
| title_sort | intrahepatic signalling niche of hedgehog is defined by primary cilia positive cells during chronic liver injury |
| url | http://hdl.handle.net/20.500.11937/42482 |