Fig. 4.

Immunofluorescences in liver sections from normal and autosomal dominant polycystic kidney disease (ADPKD) patients (3–4 μm thick) indicating the colocalization of two specific immunoreactions to co-staining: (A) proliferating cell nuclear antigen (PCNA) (a marker of cellular proliferation) and FSH receptor (FSHR). Normal biliary epithelium does not show proliferative activity [nuclei are negative for proliferating cell nuclear antigen (PCNA)] and it is negative for FSHR. In small cysts, cholangiocyte proliferation increases, as it is evident with more PCNA positive nuclei, and they start to express also FSHR. In large cysts, the number of PCNA positive nuclei enhances and FSHR is present almost in all cells. (B) Phospho-extracellular-regulated kinase (p-ERK) and FSHR expression. A normal bile duct shows negativity for both FSHR and pERK. In a small cyst, the biliary epithelium starts to express FSHR and pERK that co-localize in the same cells. In the end, in the largest cysts we find a higher presence of the receptor and the phosphorylated protein. Co-localization of PCNA and FSHR was associated with increased cellular growth in cholangiocytes expressing FSHR. Simultaneously, FSHR expression is apparently linked to the phosphorylation of ERK. Original magnification, 40×.