野生型老齢マウスと老化促進マウス（SAMP1/8）を用いた表皮幹細胞の老化表現型の解析

この博士論文は内容の要約のみの公開（または一部非公開）になっています筑波大学 (University of Tsukuba)201

野生型老齢マウスと老化促進マウス（SAMP1/8）を用いた表皮幹細胞の老化表現型の解析

筑波大学 (University of Tsukuba)201

Glycome profiling by lectin microarray reveals dynamic glycan alterations during epidermal stem cell aging

journal articl

Effect of context exposure after fear learning on memory generalization in mice

BackgroundThe conditions under which memory generalization occurs are not well understood. Although it is believed that fear memory generalization is gradually established after learning, it is not clear whether experiences soon after learning affect generalization.ResultsUsing a contextual fear conditioning paradigm in mice, we found that fear memory generalization occurred when mice were exposed to a familiar, unconditioned context soon after fear learning.ConclusionsOur results suggest that the familiarity of contexts and the timing of their exposure influences memory generalization, which increases our understanding of the mechanisms of generalization

Wild-type and SAMP8 mice show age-dependent changes in distinct stem cell compartments of the interfollicular epidermis.

Delayed wound healing and reduced barrier function with an increased risk of cancer are characteristics of aged skin and one possible mechanism is misregulation or dysfunction of epidermal stem cells during aging. Recent studies have identified heterogeneous stem cell populations within the mouse interfollicular epidermis that are defined by territorial distribution and cell division frequency; however, it is unknown whether the individual stem cell populations undergo distinct aging processes. Here we provide comprehensive characterization of age-related changes in the mouse epidermis within the specific territories of slow-cycling and fast-dividing stem cells using old wild-type, senescence-accelerated mouse prone 1 (SAMP1) and SAMP8 mice. During aging, the epidermis exhibits structural changes such as irregular micro-undulations and overall thinning of the tissue. We also find that, in the old epidermis, proliferation is preferentially decreased in the region where fast-dividing stem cells reside whereas the lineage differentiation marker appears to be more affected in the slow-cycling stem cell region. Furthermore, SAMP8, but not SAMP1, exhibits precocious aging similar to that of aged wild-type mice, suggesting a potential use of this model for aging study of the epidermis and its stem cells. Taken together, our study reveals distinct aging processes governing the two epidermal stem cell populations and suggests a potential mechanism in differential responses of compartmentalized stem cells and their niches to aging

The apoptotosis in the basal layer remains largely unchanged with age.

(A, B) Tail whole-mount epidermal sheets are stained with cleaved caspase-3 (apoptosis marker, red), β4 integrin (basal cell marker, green) and Hoechst (blue). (A) and (B) represent the immunostaining of wild-type young (2-month-old) and old (2-year-old) mice. The area within the red box is shown with higher magnification. Arrowhead represents apoptotic cells in the basal layer (B). Asterisks represent hair follicles. White dotted lines represent the boundary of scale and interscale. Scale bars: 100 μm (left) or 20 μm (right). (C) Quantification of the number of caspase3+/β4 integrin+ cells per an interscale or scale structure. The caspase3+ basal cells are scored from ≥50 interscale or scale IFE structures per mouse. N = 4. Error bars show S.E.M. Mann-Whitney U test. ns: non-significant; P = 0.22 in interscale IFE; P = 0.85 in scale IFE. (D) Quantification of the mean signal intensity of β4 integrin. Signal from whole-mount staining shown in (A, B) is measured. N = 4. Student t-test. ns: not significant. P = 0.93. (E) FACS dot plot shows gates to define basal cells in the interfollicular epidermis (α6 integrin+/CD34−/Sca1+), followed by the analysis for 7-AAD and Annexin V signals. (F, G) The mean signal intensity of α6 integrin (F) and Sca1 (G) measured by FACS. N = 3. Student’s t-test. ns: not significant; P = 0.65 (F); P = 0.66 (G). (H) Graph shows the percentage of apoptotic cells (Annexin V+/7-AAD−) in the basal IFE. N = 3. Student’s t-test. ns: not significant; P = 0.77. (I) Quantification of the number of caspase3+/β4 integrin+ cells in SAM mice at 1-year-old. The caspase3+ basal cells are scored from ≥50 interscale or scale IFE structures per mouse. N = 3. Kruskal-Wallis test for multiple comparison is used. ns: non-significant; SAMR1 vs. SAMP1; P > 0.99. SAMR1 vs. SAMP8; P > 0.99 in the interscale IFE and SAMR1 vs. SAMP1; P > 0.99. SAMR1 vs. SAMP8; P > 0.99 in the scale IFE. (J) Quantification of the mean signal intensity of β4 integrin. Signal from whole-mount staining (S2B Fig) is measured. N = 3. One-way ANOVA. ns: not significant; SAMR1 vs. SAMP1; P = 0.57. SAMR1 vs. SAMP8; P = 0.99.</p

Age-associated structural changes in the tail epidermis.

(A) Schematic diagram of the mouse tail skin. (B) Hematoxylin-eosin stained tail skin sections of young (2-month-old) and old (2-year-old) mice. Arrowheads indicate the micro-undulation in the basal region. Degenerating hair follicle is observed (asterisk). Scale bars: 50 μm. (C) Quantification of the thickness of the scale and interscale IFE. The epidermal thickness is quantified from ≥6 epidermal units per mouse. N = 3. Error bars show S.E.M. Student’s t-test. *; P P = 0.22 (C, the interscale IFE). (D) The proportion of epidermal units harboring micro-undulations. ≥30 epidermal units are counted in each mouse to score micro-undulations of basal regions of the IFE. N = 3. Student’s t-test is used. **; P E) Immunostaining of tail skin sections of young (2-month-old) and old (2-year-old) mice with K14 (basal cell marker, green) and PDGFRα (dermal cell marker, red) antibodies. Hoechst is used to stain nucleus (blue). Arrowheads indicate the micro-undulation. Scale bars: 100 μm. (F, G) Quantification of the mean signal intensity of K14 (F) or PDGFRα (G). The intensity of immunostaining signals in skin section is measured and averaged from ≥50 individual cells per mouse. N = 3. Student’s t-test. ***; P P = 0.46 (F). (H) Immunostaining of tail skin sections of young (2-month-old) and old (2-year-old) mice with α6 integrin (basal cell marker, green) and Collagen IV (basement membrane marker, red). Scale bars: 100 μm. The area within the yellow box is shown with higher magnification. Scale bars: 20 μm. (I) Quantification of the mean signal intensity of α6 integrin. The intensity of immunostaining signals in skin section is measured and averaged from ≥50 individual cells per mouse. N = 3. Student’s t-test. ns: not significant; P = 0.35 (I).</p