Mechanism of retarded liver regeneration in plasminogen activator-deficient mice: impaired activation of hepatocyte growth factor after Fas-mediated massive hepatic apoptosis.
Urokinase-type plasminogen activator (uPA) is implicated in the regulation of hepatic regeneration by activating hepatocyte growth factor (HGF). Here, we investigated its role in the hepatic regeneration after Fas-mediated massive hepatocyte death employing mice deficient in either uPA or its inhibitor, plasminogen activator inhibitor-1 (PAI-1). We measured kinetics of hepatic levels of proliferating cell nuclear antigen (PCNA)-labeling index, plasmin activity, mature HGF, and its phosphorylated receptor, c-Met. In the genetically targeted and wild-type mice, hepatocytes fell into the same extent of apoptosis 6 to 12 hours after an intraperitoneal injection with anti-Fas antibody, as judged from histologic analysis and a histon-DNA enzyme-linked immunosorbent assay (ELISA). In the wild-type mice, mature HGF emerged in the liver 6 hours following anti-Fas injection, and hepatic PCNA-labeling index started to increase following 24 hours and peaked at 48 hours. In the uPA(-/-) mice, emergence of mature HGF was delayed 12 hours and hepatic regeneration peaked at 96 hours. Supplementation with the uPA gene to the uPA(-/-) mice by in vivo lipofection restored hepatic plasmin levels, and improved a delay in the expression of both mature HGF and phosphorylated c-Met, accompanying a normal rate of liver regeneration. In contrast, PAI-1(-/-) mice showed accelerated liver regeneration; mature HGF emerged as early as 3 hours, and PCNA-labeling index increased at 24 hours. This accelerated regeneration was abolished by administration with anti-HGF antibody. These results strongly suggest a physiologic role of uPA in the proteolytic maturation of HGF, and thereby in hepatic regeneration after Fas-mediated massive hepatocyte death.
Department of Pathology, Gifu University School of Medicine, Gifu, Japan. shimim-gif@umin.ac.jp
M
M
Shimizu
A
A
Hara
M
M
Okuno
H
H
Matsuno
K
K
Okada
S
S
Ueshima
O
O
Matsuo
M
M
Niwa
K
K
Akita
Y
Y
Yamada
N
N
Yoshimi
T
T
Uematsu
S
S
Kojima
S L
SL
Friedman
H
H
Moriwaki
H
H
Mori
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D018076:DNA, Complementary / Q000235:genetics; D017228:Hepatocyte Growth Factor / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D008099:Liver / Q000473:pathology / Q000503:physiopathology*; D008115:Liver Regeneration / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D014162:Transfection; D014568:Urokinase-Type Plasminogen Activator / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D019014:fas Receptor / Q000502:physiology*
D000906:Antibodies; D018076:DNA, Complementary; D018809:Proliferating Cell Nuclear Antigen; D019014:fas Receptor; D017228:Hepatocyte Growth Factor; D014568:Urokinase-Type Plasminogen Activator