Comparative study of the plasma transfusion between non-exercised and exercised mice on the cognitive function in aged mice

다국어 초록 (Multilingual Abstract)

Aging is affected directly or indirectly by diverse physiological factors. Cognitive functions are decreased with aging process. Exercise is known to improve cognitive functions in the elderly.
The purpose of this study was to evaluate the effect of injection of young plasma on cognitive function in old mice. The effects of young plasma obtained from non-exercised mice and young plasma obtained from exercised mice on cognitive function in old mice were also comparatively investigated. For this study, short-term memory and working memory were evaluated. Neurogenesis, apoptosis, neurotrophic factor expression in the hippocampus were determined. Mice were randomly divided into one (n=10 for each group) of the following five groups : young control group (Y-CON), old control group (O-CON), old exercise group (O+EX), non-exercised plasma transfusion group (NON-TR), exercised plasma transfusion group (EX+TR).
The hippocampal neurogenesis such as DCX and brdU expression and neurotrophic factor such as BDNF and its receptor trkB expression in the old control group was lower than that in the young control group. The hippocampal apoptosis such as bax and bcl-2 expression, and cell death in the old control group was higher than in the young control group. However, plasma injection and treadmill exercise improved neurogenesis, neurotrophic factor, apoptosis in the old mice. Treadmill exercise showed more potent improving effect on the neurogenesis, neurotrophic factor, apoptosis compared to the plasma injection. However, there was no difference between non-exercised plasma and exercised plasma on the neurogenesis, neurotrohic factor and apoptosis. Decreased neurogenesis and neurotrophic factor and increased aptopsis and cell death along with cognitive dysfunction were decreased in old mice. However, treadmill exercise and young plasm injection were improved cognitive dysfunction in old mice. On the other hand, there was no difference between non-exercised plasma and exercised plasma on the cognitive functions.
based on the present results, plasma injection might be a useful strategy to counteract against aging-induced deterioration of cognition as powerful as treadmill exercise. Cognition improving effects of plasma injection could be ascribed to the enhancing neurogenesis and suppressing apoptosis by plasma injection.

국문 초록 (Abstract)

본 연구에서는 선행연구에서 보고된 노화 쥐 운동의 효과성과 젊은 혈장 주입, 운동을 실시한 쥐로부터 얻은 젊은 혈장 수혈이 노화 쥐의 인지기능에 미치는 영향을 비교하기 위하여 실시하였다. 실험을 위해 Bl6 마우스 50마리를 이용하여 5개의 그룹으로 배정하였다(각 그룹 당 10마리, 젊은 대조군 = 8주령, 노화 쥐 19개월령). 노화 쥐의 인지기능을 분석하기 위하여 다음과 같은 분석방법을 사용하였다. 신경세포생성을 알아보기 위하여 DCX, BrdU 면역조직화학법을 실시하였고, 세포사멸을 비교하기 위하여 Bax, Bcl-2 단밸질 발현을, 뇌-신경영양인자를 알아보기 위하여 BDNF와 수용체인 TrkB, 기억력 검사를 위하여 행동분석방법으로 스텝다운검사와 워터메이즈 검사를 실시하였다.
연구결과 세포생성을 알아보기 위해 실시한 DCX, BrdU 면역조직화학법에서 노화운동그룹이 혈장수혈그룹에 비해 유의한 차이를 나타내었고 혈장수혈그룹 간에는 유의한 차이가 나타나지 않았다. 세포사멸을 보기 위하여 실시 한 Bax, Bcl-2 단백질 발현과 면역조직화학법을 이용한 TUNEL 분석결과 노화운동그룹에서 혈장수혈그룹에 비해 유의한 차이를 얻을 수 있었으나, 혈장수혈그룹 간에는 유의한 차이가 나타나지 않았다. 뇌-신경영양인자와 수용체 단백질 발현을 분석한 결과 노화운동그룹이 혈장수혈그룹에 비해 유의한 차이를 나타내었고 혈장수혈그룹 간에는 유의한 차이가 나타나지 않았다. 기억력 측정을 위해 스텝다운과 워터메이즈 검사를 실시하였는데 운동그룹, 혈장수혈그룹 간에 유의한 차이는 없었다.
결론적으로, 선행연구에서 보고하고 있는 직접적인 운동의 효과와 젊은 혈장 주입은 노화 쥐의 인지기능을 개선시키는 것으로 나타났고, 지금까지 독립적으로 효과성을 검증하였는데 본 연구에서 직접적인 운동과 젊은 혈장 주입을 비교 한 결과 직접적인 운동이 젊은 혈장 수혈보다 인지기능 개선에 더 효과적인 것으로 나타났다. 그러나 젊은 쥐의 운동 실시 유·무에 따른 노화 쥐의 인지 기능에 미치는 영향은 차이가 없었다. 따라서 노화 과정에서도 직접적인 운동은 감소되는 인지기능을 개선시킬 수 있는 방법이 될 수 있으며, 운동을 할 수 없는 경우에는 젊은 혈장 수혈이 간접적인 운동의 효과를 볼 수 있는 것으로 생각된다.

목차 (Table of Contents)

• Ⅰ. Introduction 1
• 1. Purpose 4
• 2. Hypotheses 5
• Ⅱ. Review of literature 6
• 1. Parabiosis 6
• 2. Exercise and cognitive functions 9
• 3. Hippocampus and Neurogenesis 11
• 4. Apoptosis 16
• Ⅲ. Materials and Methods 18
• 1. Animals and experimental design 18
• 2. Research process 19
• 3. Exercise protocol 20
• 4. Method of plasma injection 20
• 5. Tissue preparation 21
• 6. Immunohistochemistry 21
• 1) DCX Immunohistochemistry 21
• 2) BrdU Immunohistochemistry 22
• 3) TUNEL staining 23
• 7. Western blot 24
• 8. Behavior test 24
• 1) Step-down avoidance task 24
• 2) Morris water maze task 25
• 9. Statistical analysis 26
• Ⅳ. Results 27
• 1. The effect of plasma injection on the number of DCX-positive cells in the hippocampal dentate gyrus of aged mice 27
• 2. The effect of plasma injection on cell proliferation in the hippocampal dentate gyrus of aged mice 29
• 3. The effect of plasma injection on the expressions of BDNF and TrkB in the hippocampus of aged mice 31
• 4. The effect of plasma injection on the DNA fragmentation in the hippocampus of aged mice 33
• 5. The effect of plasma injection on the expressions of Bax and Bcl-2 in the hippocampus of aged mice 35
• 6. The effect of plasma injection on the short-term memory of aged mice 37
• 7. The effect of plasma injection on the working memory of aged mice 39
• Ⅴ. Discussion 41
• Ⅵ. Conclusion 45
• References 47
• Abstract(Korean) 56