title: Metalloproteinase inhibitor TIMP-1 affects hepatocyte cell cycle via HGF activation in murine liver regeneration.
abstract: Liver regeneration depends on timely restoration of cellular mass while orchestrating structural matrix remodeling. Matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) are known to regulate the extracellular matrix (ECM) turnover and, more recently, the processing of growth factors and cytokines. We have previously demonstrated that TIMP-1 inhibits preneoplastic hepatocyte proliferation by attenuating growth factor bioavailability. In the present study, we examined the role of TIMP-1 in de novo hepatocyte cell division during liver regeneration. Comprehensive real-time reverse-transcriptase polymerase chain reaction analyses of regenerating livers revealed significant inductions in the messenger RNA of TIMP-1, TIMP-3, TIMP-4, MMP-2, MMP-9, MMP-13, MMP-14, and MMP-24, while MMP-15 expression was significantly reduced. Induction of TIMP-1 occurred during the peak of hepatocyte DNA synthesis. Studies using genetically altered mice revealed that TIMP-1 loss of function accelerated hepatocyte cell cycle progression. This finding was demonstrated by earlier expression of cyclin D1, proliferating cell nuclear antigen, and phosphorylated histone H3, which mark the G(1)-S, S, and M phase, respectively. Conversely, TIMP-1 gain of function delayed cell cycle progression. MMP activity was increased in the absence of Timp-1. Examination of hepatocyte growth factor (HGF), and its receptor Met, both of which provide a mitogenic signal for hepatocyte division, showed increased HGF activity in Timp-1(-/-)-regenerating livers. HGF is released from the ECM and is proteolytically processed to its active form. Active HGF was elevated in Timp-1(-/-) mice, leading to increased immunostaining of phosphorylated Met as well as activation of a downstream effector, p38. In conclusion, TIMP-1 is a novel negative regulator of HGF activity during liver regeneration.
authors.affiliation: Department of Medical Biophysics, Ontario Cancer Institute, Toronto, Ontario M5G 2M9, Canada.
authors.forename: Fazilat F
authors.initials: FF
authors.lastname: Mohammed
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Pennington
authors.forename: Zamaneh
authors.initials: Z
authors.lastname: Kassiri
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Rubin
authors.forename: Paul D
authors.initials: PD
authors.lastname: Soloway
authors.forename: Ulrich
authors.initials: U
authors.lastname: Ruther
authors.forename: Dylan R
authors.initials: DR
authors.lastname: Edwards
authors.forename: Rama
authors.initials: R
authors.lastname: Khokha
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D004247:DNA / Q000096:biosynthesis; D017228:Hepatocyte Growth Factor / Q000502:physiology*; D022781:Hepatocytes / Q000166:cytology* / Q000378:metabolism*; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D019715:Tissue Inhibitor of Metalloproteinase-1; D017228:Hepatocyte Growth Factor; D004247:DNA