Cell proliferative activity in the kidney of young growing rat analyzed using flash and cumulative labeling with bromodeoxyuridine.

We examined the cell proliferation activity of kidney in young growing rats using flash and cumulative labeling with bromodeoxyuridine (BrdU). Rats were subjected to the study at the age of 6 weeks, and cumulative labeling was carried out for periods of 7 to 28 days. BrdU-positive cells were observed after flash labeling and were increased by cumulative labeling. The positive epithelia were mainly distributed in the cortex and the outer stripe of the outer medulla and were scarce in the inner stripe of the outer medulla and inner medulla throughout all labeling periods. In the tubular epithelium, the majority of positive cells were found in the proximal tubule. In the proximal tubule, positive epithelia were abundant in the medullary rays and in the outer stripe of the outer medulla. In the intermediate tubule to collecting duct, positive epithelia were rare. In the renal corpuscle, positive nuclei were mainly found in the endothelial cells and the mesangial cells and were scarce in the parietal cells of the Bowman's capsule. BrdU-positive nuclei were not observed in podocytes. These results indicate that renal tubules actively grow relative to epithelial proliferation, and that the endothelial cells, the mesangial cells and the parietal cells in the renal corpuscle also proliferate at the age of 6 to 10 weeks in rats. For assessment of renal toxicity using young growing rats, not only the morphologic and physiologic features unique to the kidney but also the growing process of the kidney should be taken into account.

Histopathological analyses of the antitumor activity of anti-glypican-3 antibody (GC33) in human liver cancer xenograft models: The contribution of macrophages.

Previously, we demonstrated the antitumor efficacy of the anti-glypican-3 (GPC3) antibody GC33 in several human liver cancer xenograft models and the important role of antibody-dependent cellular cytotoxicity (ADCC) in the antitumor mechanism of GC33. Involvement of other mechanisms such as modulation of the functions of GPC3 in antitumor activity remains to be elucidated. In this study, we investigated histopathologically time-course changes in xenografts in mice following a single administration of GC33 to clarify the morphological changes contributing to the tumor growth inhibition of GC33, including the changes in GPC3-related factors/components [proliferation, extracellular matrices (ECMs) and macrophage]. Histopathological changes peaked 3-5 d after GC33 administration and included increased tumor cell death, tumor cells with round morphology, multinucleated tumor cells and small spindle/round-like cells (mostly F4/80-positive macrophages). No direct effects of GC33 on proliferation activity of tumor cells were observed. Meanwhile, alteration of ECM structures and a remarkable increase in macrophages was noted in the GC33-treated group. Increase in macrophages was observed mainly in the outer layer of tumor nodules; the area of the increase approximately included the area where the change in tumor cells and ECMs were observed. Interestingly, depletion of macrophages in the xenograft models resulted in a marked reduction of the antitumor activity of GC33. In the in vitro ADCC assay, ADCC was only slightly induced by mouse peritoneal macrophages. These data suggest that macrophages play an important role in the antitumor activity of GC33, which is not likely to be direct ADCC by macrophages themselves.