Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Aug 4:12:240.
doi: 10.3389/fnagi.2020.00240. eCollection 2020.

Estradiol Replacement at the Critical Period Protects Hippocampal Neural Stem Cells to Improve Cognition in APP/PS1 Mice

Yaoyao Qin  1 , Dong An  1 , Weixing Xu  1 , Xiuting Qi  1 , Xiaoli Wang  1 , Ling Chen  1   2 , Lei Chen  1 , Sha Sha  1   2
Affiliations

Estradiol Replacement at the Critical Period Protects Hippocampal Neural Stem Cells to Improve Cognition in APP/PS1 Mice

Yaoyao Qin et al. Front Aging Neurosci. .

Abstract

It has been suggested that there is a critical window for estrogen replacement therapy (ERT) in postmenopausal women with Alzheimer's disease (AD); however, supporting evidence is lacking. To address this issue, we investigated the effective period for estradiol (E2) treatment using a mouse model of AD. Four-month-old female APPswe/PSEN1dE9 (APP/PS1) mice were ovariectomized (OVX) and treated with E2 for 2 months starting at the age of 4 months (early period), 6 months (mid-period), or 8 months (late period). We then evaluated hippocampal neurogenesis, β-amyloid (Aβ) accumulation, telomerase activity, and hippocampal-dependent behavior. Compared to age-matched wild type mice, APP/PS1 mice with intact ovaries showed increased proliferation of hippocampal neural stem cells (NSCs) at 8 months of age and decreased proliferation of NSCs at 10 months of age; meanwhile, Aβ accumulation progressively increased with age, paralleling the reduced survival of immature neurons. OVX-induced depletion of E2 in APP/PS1 mice resulted in elevated Aβ levels accompanied by elevated p75 neurotrophin receptor (p75NTR) expression and increased NSC proliferation at 6 months of age, which subsequently declined; accelerated reduction of immature neurons starting from 6 months of age, and reduced telomerase activity and worsened memory performance at 10 months of age. Treatment with E2 in the early period post-OVX, rather than in the mid or late period, abrogated these effects, and p75NTR inhibition reduced the overproliferation of NSCs in 6-month-old OVX-APP/PS1 mice. Thus, E2 deficiency in young APP/PS1 mice exacerbates cognitive deficits and depletes the hippocampal NSC pool in later life; this can be alleviated by E2 treatment in the early period following OVX, which prevents Aβ/p75NTR-induced NSC overproliferation and preserves telomerase activity.

Keywords: Alzheimer’s disease (AD); estradiol (E2); hippocampus; neurogenesis; β-amyloid (Aβ).

PubMed Disclaimer

Figures

Figure 1
Figure 1
Time chart of the experimental procedure. Horizontal arrow indicates the mouse age (month). ↓, E2/TAPI-2 administration; +, time point of experiment examination; E-E2, early period; M-E2, mid period; L-E2, late period; HE, histological examination; WB, western blotting; BT, behavioral tests.
Figure 2
Figure 2
Abnormal neurogenesis in the dentate gyrus (DG) of APP/PS1 mice. (A) Representative images of 5-bromo-2′-deoxyuridine (BrdU) immunostaining in 6-month-old, 8-month-old, and 10-month-old APP/PS1 mice and age-matched wild-type (WT) mice (upper panels). BrdU+ cells are indicated by black arrows. Scale bar = 50 μm. The bar graphs show the mean number of BrdU+ cells in APP/PS1 mice and WT mice. *P < 0.05 vs. age-matched WT mice (Student’s t-test). (B) Ki67 immunostaining in 6-month-old, 8-month-old, and 10-month-old APP/PS1 mice and age-matched WT mice (upper panels). Ki67+ cells are indicated by white arrows. Scale bar = 50 μm. The bar graphs show the mean number of Ki67+ cells in APP/PS1 mice and WT mice. *P < 0.05 vs. age-matched WT mice (Student’s t-test). (C) Representative pictures of doublecortin (DCX) immunostaining in 6-month-old, 8-month-old, and 10-month-old APP/PS1 mice and age-matched WT mice (upper panels). Scale bar = 50 μm. The bars indicate the mean density of DCX+ cells in APP/PS1 mice and WT mice. **P < 0.01 vs. 10-month-old WT mice (Student’s t-test).
Figure 3
Figure 3
Influence of E2 on the proliferation of neural stem cells (NSCs) and the survival of immature neurons in the DG of APP/PS1 mice. (A,B) Bar graphs showing the numbers of BrdU+ cells in APP/PS1 mice or WT mice that were sham-operated (sham-op; open bars) or OVX (black bars). *P < 0.05 vs. age-matched sham-op APP/PS1 mice; #P < 0.05 and ##P < 0.01 vs. age-matched OVX-APP/PS1 mice (two-way ANOVA). (C,D) The mean density of DCX+ cells in APP/PS1 mice or WT mice. *P < 0.05 and **P < 0.01 vs. age-matched sham-op mic; #P < 0.05 vs. 6-month-old OVX-APP/PS1 mice (two-way ANOVA).
Figure 4
Figure 4
Age-related increase in Aβ accumulation and the influence of E2 on Aβ formation in the hippocampus of APP/PS1 mice. (A,B) Bar graphs showing the level of total Aβ1–42 or Aβ1–40in APP/PS1 mice that were sham-op (open bars) or OVX (black bars). *P < 0.05 vs. 6-month-old sham-op APP/PS1 mice; #P < 0.05 vs. 6-month-old OVX-APP/PS1 mice (two-way ANOVA). (C) Representative images showing Aβ immunostaining in 6-month-old, 8-month-old, and 10-month-old APP/PS1 mice that were sham-op or OVX with vehicle or E2 treatment in the early period (E-E2), mid period (M-E2), or late period (L-E2). The data show the mean counts of Aβ deposits in the hippocampus of APP/PS1 mice. Scale bar = 200 μm.
Figure 5
Figure 5
p75NTR participates in E2-induced protection of NSC proliferation in APP/PS1 mice. (A,B) Influence of E2 on the level of p75NTR in 6-month-old APP/PS1 mice. The upper panels represent representative blots of p75NTR. Bar graphs show the level of p75NTR protein or p75NTR mRNA in APP/PS1 mice or OVX-APP/PS1 mice treated with vehicle or E2 for 2 months. **P < 0.01 vs. sham-op APP/PS1 mice; ##P < 0.01 vs. OVX-APP/PS1 mice (two-way ANOVA). (C,D) Influence of the p75NTR inhibitor TAPI-2 on the excessive proliferation of NSCs and survival of immature neurons in the DG of 6-month-old APP/PS1 mice. The bar graphs show the number of BrdU+ cells and the density of DCX+ cells in APP/PS1 mice or OVX-APP/PS1 mice treated with vehicle or TAPI-2 for 7 days. *P < 0.05 vs. sham-op APP/PS1 mice; #P < 0.05 vs. OVX-APP/PS1 mice (two-way ANOVA).
Figure 6
Figure 6
The administration of E2 in the early period post-OVX rescues the impaired telomerase activity in the DG in aged APP/PS1 mice. (A) Representative RT-polymerase chain reaction (PCR) analysis showing mRNA levels of TERT in 10-month-old APP/PS1 mice that were sham-op or OVX with vehicle or E2 treatment in the early period (E-E2), mid period (M-E2), or late period (L-E2). The bar graphs show the mRNA percentage level of TERT. **P < 0.01 vs. WT mice; #P < 0.05 and ##P < 0.01 vs. sham-op APP/PS1 mice; +P < 0.05 vs. OVX-APP/PS1 mice (two-way ANOVA). (B) Bar graphs showing the quantification of telomerase activity by telomeric repeat amplification protocol (TRAP; ΔFL/ΔR). **P < 0.01 vs. WT mice; #P < 0.05 and ##P < 0.01 vs. sham-op APP/PS1 mice; +P < 0.05 vs. OVX-APP/PS1 mice (two-way ANOVA).
Figure 7
Figure 7
The administration of E2 in the early period post-OVX alleviates the cognitive deficits in aged APP/PS1 mice. (A,B) Influence of E2 treatment in the early period (E-E2), mid period (M-E2), or late period (L-E2) on working memory as assessed by the Y-maze test in 10-month-old APP/PS1 mice. The bar graphs show the spontaneous alternation ratio (%) and the total number of arm entries in the Y-maze test of APP/PS1 mice. **P < 0.01 vs. WT mice; #P < 0.05 and ##P < 0.01 vs. sham-op APP/PS1 mice; ++P < 0.01 vs. OVX-APP/PS1 mice (two-way ANOVA). (C) Spatial learning and memory were assessed by the Morris water maze (MWM). Each point represents the mean latency (sec) to reach the platforms (upper panel) and the swimming speeds (m/s; bottom panel). **P < 0.01 vs. WT mice; #P < 0.05 and ##P < 0.01 vs. sham-op APP/PS1 mice; +P < 0.05 vs. OVX-APP/PS1 mice (repeated measure ANOVA). (D) Probe trial test. The bars represent the percentages of swimming time spent in the platform quadrant. **P < 0.01 vs. WT mice; #P < 0.05 and ##P < 0.01 vs. sham-op APP/PS1 mice; +P < 0.05 vs. OVX-APP/PS1 mice (two-way ANOVA).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Adlaf E. W., Vaden R. J., Niver A. J., Manuel A. F., Onyilo V. C., Araujo M. T., et al. . (2017). Adult-born neurons modify excitatory synaptic transmission to existing neurons. Elife 6:e19886. 10.7554/elife.19886 - DOI - PMC - PubMed
    1. Ager R. R., Davis J. L., Agazaryan A., Benavente F., Poon W. W., LaFerla F. M., et al. . (2015). Human neural stem cells improve cognition and promote synaptic growth in two complementary transgenic models of Alzheimer’s disease and neuronal loss. Hippocampus 25, 813–826. 10.1002/hipo.22405 - DOI - PMC - PubMed
    1. AlMatrouk A., Lemons K., Ogura T., Luo W., Wilson C., Lin W. (2018). Chemical exposure-induced changes in the expression of neurotrophins and their receptors in the main olfactory system of mice lacking TRPM5-expressing microvillous cells. Int. J. Mol. Sci. 19:2939. 10.3390/ijms19102939 - DOI - PMC - PubMed
    1. An K., Liu H. P., Zhong X. L., Deng D. Y. B., Zhang J. J., Liu Z. H. (2017). hTERT-immortalized bone mesenchymal stromal cells expressing rat galanin via a single tetracycline-inducible lentivirus system. Stem Cells Int. 2017:6082684. 10.1155/2017/6082684 - DOI - PMC - PubMed
    1. Baruch-Eliyahu N., Rud V., Braiman A., Priel E. (2019). Telomerase increasing compound protects hippocampal neurons from amyloid β toxicity by enhancing the expression of neurotrophins and plasticity related genes. Sci. Rep. 9:18118. 10.1038/s41598-019-54741-7 - DOI - PMC - PubMed