Age-dependent changes of p53 and p63 immunoreactivities in the mouse hippocampus

Abstract

P53 and its family member p63 play important roles in cellular senescence and organismal aging. In this study, p53 and p63 immunoreactivity were examined in the hippocampus of young, adult and aged mice by using immunohistochemistry. In addition, neuronal distribution and degeneration was examined by NeuN immunohistochemistry and fluoro-Jade B fluorescence staining. Strong p53 immunoreactivity was mainly expressed in pyramidal and granule cells of the hippocampus in young mice. p53 immunoreactivity in the pyramidal and granule cells was significantly reduced in the adult mice. In the aged mice, p53 immunoreactivity in the pyramidal and granule cells was more significantly decreased. p63 immunoreactivity was strong in the pyramidal and granule cells in the young mice. p63 immunoreactivity in these cells was apparently and gradually decreased with age, showing that p63 immunoreactivity in the aged granule cells was hardly shown. However, numbers of pyramidal neurons and granule cells were not significantly decreased in the aged mice with normal aging. Taken together, this study indicates that there are no degenerative neurons in the hippocampus during normal aging, showing that p53 and p63 immunoreactivity in hippocampal neurons was progressively reduced during normal aging, which might be closely related to the normal aging processes.

Keywords: Aging process; Granule cells; Hippocampus; Mouse; Pyramidal neurons; p53; p63.

Fig. 1

a-l p53 immunohistochemistry in the hippocampus of the young (a, d, g, j), adult (b, e, h, k) and aged (c, f, i, l) mice. p53 immunoreactivity is shown in the pyramidal cells (arrows) and granule cells (asterisk) in the young mouse hippocampus. p53 immunoreactivity in these cells is significantly and gradually decreased during aging process. GCL, granule cell layer; ML, molecular layer; PL, polymorphic layer; SO, stratum oriens; SP, stratum pyramidale; SR, stratum radiatum. Scale bar = 400 μm (A-C) and 100 μm (D-L). (M) ROD as % of p53 immunoreactive cells in the hippocampus (n = 7 per group; ^*P < 0.05, significantly different from the young group, ^†P < 0.05, significantly different from the adult group). The bars indicate the means ± SEM

Fig. 2

A-L p63 immunohistochemistry in the hippocampus of the young (a, d, g, j), adult (b, e, h, k) and aged (c, f, i, l) mice. p63 immunoreactivity is found in pyramidal cells (arrows) and granule cells (asterisk) in the young mouse hippocampus. p63 immunoreactivity is gradually reduced during aging, showing that p63 immunoreactivity is hardly shown in aged granule cells (arrowhead). GCL, granule cell layer; ML, molecular layer; PL, polymorphic layer; SO, stratum oriens; SP, stratum pyramidale; SR, stratum radiatum. Scale bar = 400 μm (A-C and a-c) and 100 μm (D-L and d-l). (M) Relative optical density (ROD) as % of p63 immunoreactive cells in the hippocampus (n = 7 per group; ^*P < 0.05, significantly different from the young group, ^†P < 0.05, significantly different from the adult group). The bars indicate the means ± SEM

Fig. 3

A-I, a-i NeuN immunohistochemistry (A-I) and F-J B fluorescence staining (a-i) in the hippocampus of the young (A, D, G, a, d, g), adult (B, E, H, b, e, h), and aged (C, F, I, c, f, i) mice. In all groups, NeuN immunoreactive neurons are mainly found in the stratum pyramidale (SP) and granule cell layer (GCL), and numbers of NeuN immunoreactive neurons is not significantly different among all the groups. In addition, No F-J B positive cells are detected in any groups. Scale bar = 100 μm. (j) The mean number of NeuN immunoreactive neurons in the hippocampus (n = 7 per group). The bars indicate the means ± SEM