Cerebral autoregulation according to the degree of damage in ischemia-reperfusion brain injury
허혈-재관류 뇌 손상 모델에서 손상정도에 따른 대뇌자동조절능
- 주제(키워드) cardiac arrest , post-cardiac arrest brain injury , cerebral autoregulation , early prognostic prediction
- 주제(DDC) 570
- 발행기관 아주대학교
- 지도교수 홍지만
- 발행년도 2022
- 학위수여년월 2022. 2
- 학위명 석사
- 학과 및 전공 일반대학원 의생명과학과
- 실제URI http://www.dcollection.net/handler/ajou/000000031471
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Cardiac arrest (CA), one of the major causes of mortality worldwide, is characterized as no sign of blood circulation due to disruption of the heart’s mechanical activity. In particular, when blood supply is not provided promptly to the brain, it leads to cerebral vascular dysfunction, which leads to irreversible tissue damage. This injury is called post-CA brain injury and is directly related to the prognosis of resuscitated patients regarding post-CA syndrome. Hitherto, therapeutic hypothermia has been the standard management for patients with CA, but due to multiple drugs and massive devices, the prognosis is determined 72 hours after CA onset. It is important to evaluate brain injury early and accurately to withdraw futile prolongation treatment and achieve meaningful neurological recovery. Cerebral autoregulation (AR) is the ability to maintain consistent cerebral blood flow (CBF) despite extensive variation in arterial blood pressure through neurovascular unit interaction. When CBF is reduced below the accommodation range due to ischemia, cerebral AR is impaired and brain damage occurs. Depending on the level of AR impairment, brain damage can be classified into three stages: I, II, and III. Stage I brain damage is potentially reversible when managed with appropriate treatment. However, current prognostic modalities are used to filter out the patients in the incurable stage. Therefore, in this study, we aimed to investigate the feasibility of early prognostic discrimination using cerebral AR, and factors related to impaired cerebral AR. First, we established an ischemia-reperfusion brain injury animal model in which damage to the cerebral cortex was given differentially. To provide differential damage to the brain in Wistar rats, transient middle cerebral artery occlusion (tMCAO) was combined to a conventional CA animal model: the 4-vessel occlusion model. MCAO duration was set as 0, 15, 30, and 60 minutes. As a result, at 0.5, 24, 48, and 72 hours after surgery, brain injury severity and body weight decreased, while neurological dysfunction increased. In addition, we confirmed through histological analysis that cortical infarct volume and inflammatory response increased according to brain injury severity 72 hours after surgery. Second, we investigated impaired cerebral AR by brain injury severity in ischemia-reperfusion brain injury models. To evaluate cerebral AR, we measured the CBF before and after injecting 50mg/kg acetazolamide. The CBF image was obtained at 0.5, 24, 48, and 72 hours after surgery. As a result, impairment of cerebral AR became severe at 24 hours postoperatively according to brain injury severity. Furthermore, the 72-hour postoperative survival rate was determined by the degree of cerebral AR impairment. Finally, we investigated expression of cerebral AR-related factors (Rho-associated protein kinase II [ROCK2], myosin phosphatase target subunit [MYPT], and endothelial nitric oxide synthase [eNOS]) and inflammatory response (glial fibrillary acidic protein [GFAP]) and apoptosis (bcl-2 associated X protein [Bax] and b-cell lymphoma 2 [Bcl-2]) related factors in the ischemia-reperfusion brain injury models. To evaluate the expression of related factors the core region of brain injury was obtained at 24 and 72 hours after surgery through dissection. As a result, 24 hours after surgery, expression of ROCK2 and MYPT were decreased in the moderate and severe cortical injury groups compared to the sham group. In addition, there was no difference of eNOS expression among groups. At 72 hours postoperative, GFAP and Bax expression increased while Bcl-2 decreased according to brain injury severity. In conclusion, these results indicate that cerebral AR is impaired according to the brain injury severity at 24 hours, and is associated the 72-hour postoperative prognosis. This suggests the possibility of early prognosis prediction through cerebral AR.
more목차
Ⅰ. INTRODUCTION １
A. Post-cardiac arrest syndrome １
B. Cerebral autoregulation ２
C. Associated factors of cerebral autoregulation ３
D. Prognostic assessments after cardiac arrest ４
E. Aims of study ５
Ⅱ. MATERIALS AND METHODS ８
A. Ethics statement ８
B. Animal care conditions and universal procedures ８
C. Establishment of animal models ８
D. In vivo brain imaging １０
1. Measurement of cerebral blood flow １０
2. Evaluation of autoregulation １０
E. Neurobehavioral tests １０
1. Modified neurological severity score １１
2. Neurologic deficit scores １１
F. Brain tissue section １１
G. Cresyl violet staining １２
1. Evaluation of cerebral cortical infarction １２
2. Hippocampus scoring １２
H. Immunohistochemistry １３
I. Western blot １３
J. Statistical analyses １４
Ⅲ. RESULTS １８
A. Comparison of ischemia-reperfusion brain injury models １８
1. Changes in survival rate, body weight, neurological function, and CBF compared between sham and cortical injury groups １８
2. Comparison of cell viability and inflammatory responses in the hippocampus and cerebral cortex among sham and cortical injury groups ２４
B. Cerebral autoregulation and associated factors ２９
1. Correlation of impaired cerebral autoregulation and brain injury severity in sham and cortical injury groups ２９
2. Expression of factors associated with impaired cerebral autoregulation in sham and cortical injury groups ３１
Ⅳ. DISCUSSION ３３
Ⅴ. CONCLUSION ３７
REFERENCES ３８
국문요약 ４５
