Regulated catalysis of extracellular nucleotides by vascular CD39/ENTPD1 is required for liver regeneration.
OBJECTIVE
Little is known about how endothelial cells respond to injury, regulate hepatocyte turnover and reconstitute the hepatic vasculature. We aimed to determine the effects of the vascular ectonucleotidase CD39 on sinusoidal endothelial cell responses following partial hepatectomy and to dissect purinergic and growth factor interactions in this model.


METHODS
Parameters of liver injury and regeneration, as well as the kinetics of hepatocellular and sinusoidal endothelial cell proliferation, were assessed following partial hepatectomy in mice that do not express CD39, that do not express ATP/UTP receptor P2Y2, and in controls. The effects of extracellular ATP on vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and interleukin-6 responses were determined in vivo and in vitro. Phosphorylation of the endothelial VEGF receptor in response to extracellular nucleotides and growth factors was assessed in vitro.


RESULTS
After partial hepatectomy, expression of the vascular ectonucleotidase CD39 increased on sinusoidal endothelial cells. Targeted disruption of CD39 impaired hepatocellular regeneration, reduced angiogenesis, and increased hepatic injury, resulting in pronounced vascular endothelial apoptosis, and decreased survival. Decreased HGF release by sinusoidal endothelial cells, despite high levels of VEGF, reduced paracrine stimulation of hepatocytes. Failure of VEGF receptor-2/KDR transactivation by extracellular nucleotides on CD39-null endothelial cells was associated with P2Y2 receptor desensitization.


CONCLUSIONS
Regulated phosphohydrolysis of extracellular nucleotides by CD39 coordinates both hepatocyte and endothelial cell proliferation following partial hepatectomy. Lack of CD39 activity is associated with decreased hepatic regeneration and failure of vascular reconstitution.
Beldi
Guido
G
Transplant and Liver Centers, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, Massachusetts 02215, USA.
Wu
Yan
Y
Sun
Xiaofeng
X
Imai
Masato
M
Enjyoji
Keiichi
K
Csizmadia
Eva
E
Candinas
Daniel
D
Erb
Laurie
L
Robson
Simon C
SC
D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis*; D017209:Apoptosis; D001081:Apyrase / Q000096:biosynthesis*; D002384:Catalysis; D049109:Cell Proliferation; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D006498:Hepatectomy; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D015850:Interleukin-6 / Q000378:metabolism; D008099:Liver / Q000293:injuries / Q000378:metabolism / Q000473:pathology*; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D015703:Antigens, CD; D015850:Interleukin-6; D042461:Vascular Endothelial Growth Factor A; D017228:Hepatocyte Growth Factor; D001081:Apyrase; C067869:CD39 antigen