Distinct roles for non-muscle myosin II isoforms in mouse hepatic stellate cells.

-Background and purpose: Blebbistatin, an inhibitor of myosin-II-specific ATPase, has been used to inhibit contraction of
invertebrate and mammalian muscle preparations containing non-muscle myosin. Activated hepatic stellate cells have contractile
properties and play an important role in the pathophysiology of liver fibrosis and portal hypertension. Therefore, hepatic
stellate cells are considered as therapeutic target cells. In the present study, we studied the effect of blebbistatin during the
transition of mouse hepatic stellate cells into contractile myofibroblasts.
Experimental approach: Effects of blebbistatin on cell morphology were evaluated by phase contrast microscopy. Cell stress
fibres and focal adhesions were investigated by dual immunofluorescence staining and visualized using fluorescence microscopy.
Contractile force generation was examined by silicone wrinkle formation assays and collagen gel contraction assays.
Intracellular Ca2+ release in response to endothelin-1 was measured by using Fluo-4. Cell migration was measured by wound
healing experiments.
Key results: In culture-activated hepatic stellate cells, blebbistatin was found to change both cell morphology and function.
In the presence of blebbistatin, stellate cells became smaller, acquired a dendritic morphology and had less myosin IIAcontaining
stress fibres and vinculin-containing focal adhesions. Moreover, blebbistatin impaired silicone wrinkle formation,
reduced collagen gel contraction and blocked endothelin-1-induced intracellular Ca2+ release. Finally, it promoted woundinduced
cell migration.
Conclusions and implications: By inhibiting myosin II ATPase, blebbistatin has profound effects on the morphology and
function of activated hepatic stellate cells. Our data suggest that myosin II could be a therapeutic target in the treatment of
liver fibrosis and portal hypertension.