586 Fig. 3 Pairs of serial sections stained for immunohistochemical detection of Cx32 (left panels, a, c, e, g, punctuated blue spots) or Ki67 (right panels, b, d, f, h, intense blue nuclei). b, d, f, g, h Processed for DPPIV enzyme activity. Note that different rates of Ki67 labelling in nodular hepatocyte clusters (b: 2%, d: 11%, f: 34%), are associated with similar low levels of Cx32 expression (a, c, e). However, signiﬁcant Ki67 labelling in normal hepatocyte clusters (h) is paired with normal distribution of Cx32 gap junction protein (g). See ‘‘Materials and methods’’ for details Histochem Cell Biol (2011) 135:581–591 The expression of MMP-2 in transplanted normal and nodular hepatocytes Matrix metalloproteinases (MMPs) are a family of enzymes that can collectively degrade all components of the extra- cellular matrix. They play fundamental roles in several processes, including tissue remodelling, inﬂammation, wound healing, ﬁbrosis, cell migration, and metastasis, among others (Ellerbroek and Stack 1999). MMPs are syn- thesized as pro-enzymes and are activated upon proteolytic cleavage in the extracellular space (Montironi et al. 2002). MMP-2, also known as gelatinase A, can degrade collagens, gelatin, elastin, ﬁbronectin, laminins, and is possibly involved in the activation of other MMPs, such as MMP-9 and MMP-13 (Fridman et al. 2009). In a previous study, it was found that MMP-2 is expressed at the leading edge of expanding clusters of transplanted normal hepatocytes (Koenig et al. 2005). Given the postulated role of MMP-2 in cell migration, we decided to analyse the pattern of distri- bution of this enzyme in the expanding clusters of normal and nodular cell populations. As illustrated in Fig. 5, a positive immunoﬂuorescent signal corresponding to MMP-2 123