基因微陣列分析缺血/灌流對人類肝切除手術引發之相關細胞凋亡基因表現之研究(2/2)

Abstract

缺血會引起實驗動物細胞凋亡 (apoptosis)及萎縮(atrophy)是已知的。在缺 血／灌流對實驗動物造成傷害的正確機制 及媒介質迄今仍不十分清楚。在我們先前 研究大鼠的肝臟缺血60 分鐘再灌流24 小 時的過程中，藉由TUNEL 分析及配合清晰 之DNA ladder bands 的結果顯示當肝臟再 灌流6 小時之肝細胞的死亡達到最高峰。 然而在缺血終止時bax RNA、bcl-x RNA、 bcl-xL 卻有表現，此舉顯示此時相關之細 胞凋亡基因可能已開始表現。我們更進一 步地做了一個研究以便於了解間歇性缺血 (intermittent ischemia)再灌流6 小時對大鼠 肝臟誘發細胞凋亡之影響，並與連續性缺 血(continuous ischemia)作一比較。結果顯 示，在再灌流6 小時的時間點，間歇性缺 血對大鼠肝臟造成之傷害較連續性缺血嚴 重，而且當間歇性缺血時間越久則肝細胞 受傷愈嚴重，至於bax、 bcl-xL、fas 亦皆 有表現。 我們強烈相信缺血／灌流在病人切除 肝臟手術過程中誘發之細胞凋亡之分子機 制是非常值得研究的。所以我們針對間歇 性缺血及連續性缺血在病人切除肝臟手術 過程中誘發的細胞凋亡做一研究。我們將 利用基因微陣列更進一步分析相關之細胞 凋亡基因的表現。故本計畫之焦點在於正 確且客觀地探討間歇性缺血vs.連續性缺血 對切肝手術病人傷害的程度，以及被誘發 之早期細胞凋亡之相關基因產生的傷害或 保護之表現情形。 我們對10 個因肝癌在臺大醫院做肝切 除手術的病人設計了以下實驗：(1)肝臟未 缺血時（即時間原點），(2)當缺血的時間 點為15 及30 分鐘，(3)再灌流時間點分別 為5、15 及30 分鐘時，收集肝臟檢體及抽 取病人血液並分離出血清。萃取肝臟檢體 的RNA 進行9600 點的基因微陣列實驗， 統計分析結果發現相對於時間原點有顯著 差異表現的基因，在缺血時有13 個，再灌 流時有31 個，其中重複的有5 個。

Ischemia is known to be a cause of apoptosis and atrophy in experimental animals. Until today, the exact mechanisms and mediators involved in ischemia / reperfusion injury remains unclear. In our previous study on rats, liver was ischemia 60 minutes followed by reperfusion for 24 hours. Results showed that the death of hepatocytes is maximal after reperfusion for 6 hours by TUNEL assay and clear DNA ladder bands. Whereas the expressions of bax RNA, bcl-x RNA, and bcl-xL were not negative at the end of ischemia, which imply the regulated apoptosis related genes might have been expressed at this time. Furthermore, we made a study to recognize the effect of intermittent ischemia following reperfusion for 6 hours induction apoptosis on rats' liver, and the continuous ischemia was compared. The finding showed that the injury of intermittent ischemia was more serious than that of continuous ischemia after reperfusion for 6 hours. And the longer time of intermittent ischemia, the more hepatocytes were damaged. The expression of bax, bcl-xL and fas all were positive. We strongly believe it is worth to investigate the molecular mechanisms of induced apoptosis by ischemia / reperfusion during liver resection operations in human patients. So we made a study to test the effects of continuous and intermittent ischemia on induction of hepatocytes death during liver resection in human patients. In addition, we investigated the expression of related apoptotic genes by cDNA microarray. Therefore the focus of our project was exploring objectively and correctly the injury of intermittent vs. continuous ischemia on liver surgery in human patients, and the expression of apoptosis-related genes which makes induction of damage or protective effects during early state. We designed the experiments on liver resection operations of 10 liver cancer patients in National Taiwan University Hospital. The liver specimens and serum were collected at the time points of 0, 15 and 30 minutes in ischemia condition, and following the reperfusion time points of 5, 15 and 30 minutes. We extracted the RNA of liver specimens and then performed the cDNA microarray experiments which used the 9600 -clones chips. After statistic analysis, we found out some genes significantly different from those expressed at the control time point, ischemia 0 minutes. There were 13 different expression genes in period of ischemia and 31 genes in period of reperfusion. Among them 5 genes were overlapping.