Kupffer cells are mandatory for adequate liver regeneration by mediating hyperperfusion via modulation of vasoactive proteins.
OBJECTIVE
Physiological liver regeneration requires adequate microvascular perfusion after partial hepatectomy. Although Kupffer cells (KCs) are known to play a key role in modulating hepatocyte proliferation, their impact on regulating hepatic microcirculation during liver regeneration has so far been disregarded. With respect to their expression and modulation of vasoactive mediators, KCs may provide important signals that regulate hepatic perfusion during liver regeneration.


METHODS
Intravital fluorescence microscopy, immunohistochemistry, Western blot analysis, and RT-PCR were used to analyze livers of KC-depleted mice (liposome-encapsulated clodronate application) and KC-competent mice at days 3, 5, and 8 after 68% hepatectomy.


RESULTS
Selective and long-lasting KC elimination limited the resection-associated hyperperfusion, as evidenced by an only 1.7- to 2-fold increase of sinusoidal volumetric blood flow and shear stress in contrast to a 3.5- to 5-fold increase in KC-competent mice. In accordance to that livers of KC-depleted mice showed an altered pattern of vasoregulatory gene expression. KC-depleted mice failed to show resection-induced increase of HO-1 and eNOS protein expression, but revealed a reduction of hepatic eNOS and HO-1 protein levels to 22 and 12% of the corresponding values in KC-competent mice. In addition, the eNOS inhibitory protein caveolin-1 was increased in KC-depleted animals prior to as well as after resection. Furthermore, resection-associated accumulation of ET-1 mRNA was absent in KC-depleted livers. Finally, liver mass restoration was impaired, with a regain of only 79% weight within 8 days after resection in KC-depleted mice.


CONCLUSIONS
The present study documents a remarkable change of the vasoactive mediator profile upon KC-depletion and liver resection, limiting intrahepatic hyperperfusion. Therefore, KC-dependent molecular mechanisms seem to be mandatory in regulating vasotonus during the process of liver regeneration and therewith maintaining intrahepatic shear stress as a trigger of hepatic proliferation.
Abshagen
Kerstin
K
Institute for Experimental Surgery, University of Rostock, Rostock, Germany.
Eipel
Christian
C
Kalff
Jörg C
JC
Menger
Michael D
MD
Vollmar
Brigitte
B
D000818:Animals; D001794:Blood Pressure; D051242:Caveolin 1 / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D019332:Endothelin-1 / Q000235:genetics / Q000378:metabolism; D005260:Female; D051547:Heme Oxygenase-1 / Q000378:metabolism; D007728:Kupffer Cells / Q000166:cytology / Q000502:physiology*; D008102:Liver Circulation / Q000502:physiology*; D008115:Liver Regeneration / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008833:Microcirculation / Q000502:physiology; D008856:Microscopy, Fluorescence; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013943:Thymol; D014661:Vasoconstriction / Q000502:physiology*
D051242:Caveolin 1; D019332:Endothelin-1; C007905:Hartman's solution; D012333:RNA, Messenger; D013943:Thymol; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D051547:Heme Oxygenase-1