Sequential Matrix Metalloproteinase-1 Expression Triggered by Infiltrating Monocytic Lineage Cells Modulates Pathophysiological Aspects of Human Nonalcoholic Steatohepatitis

Isao Okazaki,1,* Shinsuke Shibata,2,3,* Wataru Ando,4,* Takayo Yanagawa,5,6 Hiroaki Yokomori,7 Akira Sonoda,8 Norihiko Suzuki,9 Eigoro Yamanouchi,10 Shinya Okada,11 Shinichi Kamikura,11 Kazuaki Hachimura,11 Takashi Takaki,12 Katsuya Otori,4 Yutaka Suzuki,9 Hideyuki Okano,2 Yutaka Inagaki5,6 1Department of Internal Medicine, International University of Health and Welfare (IUHW) Hospital, Nasu-Shiobara City, Tochigi Prefecture, Japan; 2Department of Physiology, Keio University School of Medicine, Shinjuku-Ku, Tokyo, Japan; 3Electron Microscope Laboratory, Keio University School of Medicine, Shinjuku-Ku, Tokyo, Japan; 4Department of Clinical Pharmacy, Kitasato University School of Pharmacy, Minato-Ku, Tokyo, Japan; 5Center for Matrix Biology and Medicine, Tokai University Graduate School of Medicine, Isehara City, Kanagawa Prefecture, Japan; 6Department of Innovative Medical Science, Tokai University School of Medicine, Isehara City, Kanagawa Prefecture, Japan; 7Department of Internal Medicine, Kitasato University Medical Center, Kitamoto City, Saitama Prefecture, Japan; 8Collaborative Research Resources, Core Instrumentation Facility, Keio University School of Medicine, Shinjuku-Ku, Tokyo, Japan; 9Department of Surgery; 10Deparment of Radiology; 11Department of Pathology, IUHW Hospital, Nasu-Shiobara City, Tochigi Prefecture, Japan; 12Division of Electron Microscopy, Showa University School of Medicine, Shinagawa-Ku, Tokyo, Japan*These authors contributed equally to this workCorrespondence: Isao OkazakiHigashi Nippon International University, Iwaki City, Fukushima Prefecture, JapanTel +81-246-35-0001Fax +81-246-25-9188Email okazakiisao@hotmail.co.jpBackground/Aims: Matrix metalloproteinase-1 (MMP-1) is a key enzyme in collagen metabolism and tissue remodeling. We previously reported that MMP-1 expression in monocytes and other types of cells in the liver is associated with disease progression in patients with nonalcoholic steatohepatitis (NASH). To further implicate MMP-1 up-regulation in NASH pathogenesis, we examined dynamic and sequential MMP-1 expression in peripheral blood monocytes and cells in steatotic liver, and attempted to elucidate the mechanism of MMP-1 induction.Methods: Twenty-nine NASH patients and 26 non-NASH subjects were recruited in the study. Their peripheral blood mononuclear cells were isolated and analyzed by fluorescence-activated cell sorting, and liver specimens were subjected to confocal laser-scanning and immunoelectron microscopic examinations. Peripheral blood monocytic lineage cells were co-cultured with steatotic hepatocytes obtained from biopsy specimens to examine MMP-1 induction.Results: Infiltrating monocytes were the earliest to acquire an MMP-1-expressing phenotype among all investigated cell types in early-stage NASH liver. On the other hand, circulating monocytes did not express significant levels of MMP-1 mRNA or protein before infiltrating steatotic liver. Co-culture with steatotic hepatocytes induced MMP-1 expression in otherwise MMP-1-negative peripheral blood monocytic lineage cells. As disease progressed, MMP-1 was sequentially expressed by other types of cells in NASH liver. Notably, clusters of OV-6- or CK19-positive hepatic progenitor cells with a morphological feature of ductular reaction showed strong MMP-1 staining in advanced-stage NASH.Conclusion: MMP-1 up-regulation in infiltrating monocytic lineage cells represents an initial event in early-stage NASH and, together with the subsequent expression in other types of cells, modulates pathophysiological aspects of NASH.Keywords: matrix metalloproteinase-1, nonalcoholic steatohepatitis, monocytic progenitor cells, hepatic progenitor cells, liver fibrosis