The role and immunophenotypic characteristics of myofibroblasts in liver of sheep naturally infected with the lancet liver fluke (Dicrocoelium dendriticum)

- Activated hepatic stellate cells in sheep infected with Dicrocoelium dendriticum express α-SMA, desmin, and vimentin.
- Interface and portal/septal myofibroblasts are α-SMA and vimentin immunopositive in the liver of sheep infected with lancet fluke. The intensity of α-SMA expression may be used as a marker of activated myofibroblasts.
- All populations of myofibroblasts, especially hepatic stellate cells, play an important role in the increased extracellular matrix formation during the parasitic liver fibrosis in sheep naturally infected with D. dendriticum.

The main objective of our research was to examine the role and immunophenotypic characteristics of myofibroblasts in sheep liver naturally infected by the lancet liver fluke (Dicrocoelium dendriticum). In the reported study we analyzed liver samples from 20 adult sheep, 14 infected animals and 6 controls. The liver samples were fixed in 10% buffered formalin, and routinely processed and stained using hematoxylin eosin, the periodic acid-Schiff and Masson-Goldner trichrome methods. The immunohistochemical examination was carried out by the streptavidin biotin (LSAB2) method, using antibodies for α-smooth muscle actin (α-SMA), desmin and vimentin. The histopathological examination revealed liver fibrosis in 6 out of 14 (42.9%) analyzed samples, while different forms of cholangitis were observed in the remaining 8 out of 14 (57.1%). The expression of α-SMA was proven in perisinusoidal hepatic stellate cells, portal/septal myofibroblasts, and interface myofibroblasts. The degree of α-SMA expression and the number of α-SMA immunopositive cells were the most intensive in the liver with fibrosis. Desmin expression in all liver samples of infected sheep was confirmed in hepatic stellate cells and smooth muscle cells. The hepatic stellate cells, portal/septal myofibroblasts, and interface myofibroblasts reacted as vimentin positive cells. In the liver without fibrotic changes hepatic stellate cells and smooth muscle cells were desmin positive. The obtained results suggest that all populations of myofibroblasts, especially hepatic stellate cells, play an important role in the increased extracellular matrix formation during parasitic liver fibrosis in sheep naturally infected with D. dendriticum.