Figure S5

1. Figure S5 BrdU/Albumin/Hoechst a b 20x 40x Figure S5 Proliferating cells in livers of non-parabiotic and parabiotic mice. a, Non-parabiosed mice show an age-dependent decrease in proliferation of hepatocytes as do isochronically parabiosed mice (see Fig. 3). Non-parabiosed mice were given BrdU injections 5, 3 and 1 day prior to sacrifice. Livers sections were analyzed for hepatocyte proliferation by staining for BrdU incorporation and albumin as in Figure 3. b, Examples of clusters of proliferating cells in aged livers that are not hepatocytes. Parabiotic and non-parabiotic pairs were given BrdU injections 5, 3, and 1 day prior to sacrifice, and livers were analyzed for BrdU incorporation (green). Hepatocytes are identified by staining for albumin (red). Hoechst dye (blue) labels all nuclei. In the fields shown, the vast majority of proliferating cells were albumin-. Of note, such clusters were seen in most old mice in isochronic pairings as well as in non-parabiotic old mice, but not in any of the livers of old mice in heterochronic parabiotic pairings.