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

Abstract

Background/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

Acknowledgments

We are grateful to the staff, especially doctors, nurses, and expert nutritionists of the “NASH Education Admission Program” at the Surgical Department in IUHW Hospital. We thank Ms. Cecilia Hamagami for assistance with the English revision of the manuscript, and Editage for English language editing.

Author Contributions

All authors made substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; took part in drafting the article or revising it critically for important intellectual content; gave final approval of the version to be published; and agree to be accountable for all aspects of the work.

Disclosure

The authors have declared that no conflicts of interest exist.