脳虚血巣周囲組織に出現する神経栄養因子について

ISCHEMIA-INDUCED NEUROTROPHIC ACTIVITY DETECTED IN THE PERIINFARCTED BRAIN TISSUE

　抄録　ラットの中大脳動脈閉塞による虚血性軸索損傷により虚血側の視床ニューロンは逆行性変性に陥るが，虚血巣近傍の大脳皮質ニューロンは生存し続ける。このような差が神経栄養因子に関連したものかどうかを明らかにするため，培養神経細胞を用いて以下の検討を行った。胎性第17日のラット大脳皮質から得た神経細胞をpoly-L-lysineでコーティングした24ウェル内で無血清培養液を用いて低密度培養した。これに虚血後4日および8日の虚血周囲脳抽出液を添加し，神経細胞の生存，突起の伸展・維持に及ぼす効果を検討した。虚血側大脳皮質抽出液添加群は対側皮質抽出液添加群と比べて約50％神経細胞の生存を延長した。しかし視床抽出液添加ではこのような病変側と対側での差は認めなかった。この神経栄養効果は虚血後4日のラット抽出液にはみられず，虚血後8日のものに認められた。またこの効果は抽出液を90℃で10分間熱処理することにより消失した。以上の結果から脳虚血巣周囲の大脳皮質には胎児大脳神経細胞の生存を維持させる因子が存在し，これが虚血によって軸索を損傷されたニューロンの生存に関与していることが示唆される。

In the experimental ischemia induced by occlu-sion of the rat middle cerebral artery, axons of both cortical and thalamic neurons were affected. However, cortical neurons survived thereafter and thalamic neurons died because of retrograde dege-neration. The fate in these two groups of neurons was remarkably different and may be related to neurotrophic activity induced by ischemia. To detect ischemia-induced neurotrophic activity, fetalcortical neuron was cultured and neurotrophic activity was detected by applying tissue extract to the culture system. Fetal neurons obtained from 17 days rat embryo were cultured for 24 hours at 3. 75x 10⁴ cells per 15 mm well in modified Eagle's minimum essential (MEM) supplemented by 10% fetal bovine serum (FBS), then for next 3 to 7 days with Dulbecco's modified Eagle's medium/ Ham's nutrient mixture F-12 (DME/F-12) supple-mented with insulin 5 mg//, transferrin 10 mg//, progesterone 6. 3 Aga, Na₂SeO₃ 5. 2 Aga. The tissue extract was obtained from the rat subjected to ischemia and homogenized with DME/F-12. The homogenate was centrifuged at 100, 000 g for 90 minutes and the supernatant was obtained. Appli-cation of periischemic cortical extract improved neurons' survival by 50% as compared to extract of the contralateral side. However, the thalamic extract of the ischemic side had no neurotrophic activity as compared to the contralateral side. The activity was detected in the extract obtained at 8 days after ischemia but not detected in the extract obtained at 4 days after ischemia. The neurotrophic activity was disappeared by heating the extract at 90°C for 10 minutes. The result indicates that cortical extract at about a week after focal ischemia has neurotrophic activity to fetal cortical neurons. This neurotrophiphic acti-vity may relate to survival of neurons whose axons injured by ischemia.