584 Fig. 1 Histochemical staining for DPPIV enzyme activity (orange-rust) in clusters of normal (a) and nodular (b) hepatocytes transplanted into the liver of DPPIV- deﬁcient host rats pre-treated with RS. Immunoﬂuorescence labelling for DPPIV expression (red) in clusters of normal (c) and nodular (d) hepatocytes transplanted as above; DAPI (blue) identiﬁes nuclei. Both enzyme activity and protein distribution were typically associated with the cell membrane in normal hepatocyte clusters (a, c), while they were irregular and diffuse to the cytoplasm in the expanding clusters of nodular hepatocytes (b, d). e, f Two serial cryostat sections of a nodular hepatocyte cluster stained for DPPIV expression (e, orange-rust) and with standard H&E (f). Note the presence of megalocytes in the RS-treated surrounding liver (upper-left). g, h Two serial sections of a large nodular hepatocyte cluster stained for DPPIV (g) and for the presence of CD44 marker (h); CD44- positive non-parenchymal cells are present inside the nodule, while transplanted nodular hepatocytes are negative Histochem Cell Biol (2011) 135:581–591 The expression of Cx32 in transplanted normal and nodular hepatocytes Connexins are the major proteins of gap junctions, which serve to establish communication channels between adja- cent cells. As such, they are involved in both tissue pattern formation and maintenance of integrated cellular functions. Small molecules (\1 kDa in size) can be exchanged through gap junctions, thereby contributing to the functional cooperation of cells within tissues (Vinken et al. 2008). Given their direct involvement in processes related to tissue pattern formation and cell-to-cell communication, we decided to compare the expression of Cx32, the major gap junction protein present in the liver, in the expanding clusters of normal and nodular transplanted hepatocytes. As presented in Fig. 2, Cx32 was regularly found with the typical punctuated pattern of distribution at the cell membrane in small and larger clusters of transplanted 123