廖余平,陳翀,李曉紅,王景景,陳以勝,張賽,孫洪濤△
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亞低溫聯(lián)合載神經(jīng)干細(xì)胞的纖維蛋白支架對顱腦創(chuàng)傷的修復(fù)作用
廖余平1,2,陳翀1,李曉紅1,王景景1,陳以勝1,張賽1,孫洪濤1△
摘要:目的研究大鼠顱腦創(chuàng)傷(TBI)后原位移植神經(jīng)干細(xì)胞(NSCs)治療的可能性,探討載有NSCs的纖維蛋白支架及與亞低溫(MHT)聯(lián)合對TBI的治療作用。方法從孕14 d SD大鼠皮質(zhì)組織中分離NSCs,與纖維蛋白支架共培養(yǎng),應(yīng)用掃描電鏡觀察支架及NSCs的形態(tài),并通過免疫熒光檢測細(xì)胞類型。將48只雄性SD大鼠隨機(jī)分成TBI組(A組)、TBI+NSC組(B組)、TBI+MHT組(C組)、TBI+NSC+MHT組(D組),每組12只。A組通過液壓損傷儀行TBI造模;B組TBI后接受NSCs移植治療;C組TBI后接受MHT治療;D組TBI后接受NSCs與MHT聯(lián)合治療。分別在第14、28天通過神經(jīng)功能缺陷評分(mNSS)和水迷宮實驗對大鼠進(jìn)行神經(jīng)功能評價;28 d后取腦組織切片,行細(xì)胞免疫熒光檢測,觀察移植后的NSCs在體內(nèi)分化情況。結(jié)果電鏡掃描顯示,NSCs與纖維蛋白支架共培養(yǎng)3 d后形態(tài)無明顯改變;免疫熒光提示NSCs特異性標(biāo)志物Nestin陽性表達(dá),表明神經(jīng)干細(xì)胞在纖維蛋白支架上存活;D組大鼠的mNSS在第14天和第28天均低于A、B、C各組;水迷宮結(jié)果顯示,D組大鼠逃避潛伏期短于A、B、C各組;D組28 d后腦組織取材可追蹤到BrdU標(biāo)記的神經(jīng)干細(xì)胞分化為了神經(jīng)元。結(jié)論纖維蛋白支架與NSCs生物相容性良好,具有可降解性。亞低溫與載NSCs的纖維蛋白支架對大鼠TBI后的神經(jīng)功能修復(fù)具有協(xié)同作用。
關(guān)鍵詞:顱腦損傷;神經(jīng)干細(xì)胞;纖維蛋白支架;亞低溫
△通訊作者E-mail:chenmo333@163.com
大量的基礎(chǔ)和臨床研究表明,神經(jīng)干細(xì)胞(neu?ral stem cells,NSCs)移植治療顱腦創(chuàng)傷(traumatic brain injury,TBI)的效果不夠理想,其原因主要與NSCs的低存活率有關(guān)[1]。移植干細(xì)胞的大量死亡主要與TBI局部缺血、缺氧、炎癥、水腫的微環(huán)境有關(guān)[2]。移植干細(xì)胞在目標(biāo)部位存活是干細(xì)胞發(fā)揮作用的前提,而影響干細(xì)胞行為的決定性因素主要是局部的微環(huán)境。前期的研究通過皮質(zhì)損傷后直接局部移植NSCs發(fā)現(xiàn),移植細(xì)胞黏附、遷移到損傷區(qū)的比例非常低[3-4],主要是缺乏支撐移植細(xì)胞存活的三維細(xì)胞外基質(zhì)結(jié)構(gòu),細(xì)胞移植后大部分被遷移丟失。本實驗采用纖維蛋白支架模擬細(xì)胞外基質(zhì)結(jié)構(gòu),聯(lián)合亞低溫治療(mild hypothermia treatment,MHT)對TBI大鼠進(jìn)行干預(yù),探討其對TBI的治療效果。
1.1材料孕14 d SD大鼠胎鼠和清潔級260~300 g SD大鼠(購自解放軍軍事醫(yī)學(xué)科學(xué)院);纖維蛋白原、凝血酶、抑肽酶(Sigma,美國);B27、成纖維細(xì)胞生長因子(Fibroblast growth factor,bFGF)、表皮生長因子(epidermal growth factor,EGF)、BrdU(Sigma,美國);DMEM培養(yǎng)基(Gibco,美國);小鼠抗BrdU抗體(Abcam,英國);兔抗NeuN抗體、FITC標(biāo)記的山羊抗小鼠IgG二抗、FITC標(biāo)記的山羊抗兔IgG二抗(Life technology,美國)。
1.2方法
1.2.1NSCs分離與培養(yǎng)孕14 d的SD大鼠胎鼠采用6%水合氯醛(36 mg/kg)進(jìn)行腹腔麻醉,75%乙醇全身消毒,剖腹取胎鼠,取腦,剪碎吹打,加入全培養(yǎng)基[DMEM/F12、20 μg/L EGF、20 μg/L bFGF、1% N2(N-2supplement),2% B274mmol/L谷氨酰胺],于37℃、5%CO2培養(yǎng)箱中培養(yǎng)。培養(yǎng)3~ 4 d離心、棄去上清液,5~7 d后用吸管吹打NSCs球(即形成的細(xì)胞克?。┲瞥蓡渭?xì)胞懸液后繼續(xù)傳代。用10 μmol/L的BrdU標(biāo)記48 h備用。
1.2.2纖維蛋白支架的制備將纖維蛋白原溶解在生理鹽水中,配制成40 g/L的纖維蛋白原溶液(含50 U/mL的抑肽酶)。將凝血酶溶解在40 mmol/L CaCl2溶液中,配制濃度為40 U/mL的凝血酶溶液。將纖維蛋白溶液和凝血酶溶液等體積混合后,置入37℃恒溫箱中,充分孵育10 min,待纖維蛋白完全凝膠后,檢測其性能。
1.2.3纖維蛋白支架的微觀結(jié)構(gòu)將制備的纖維蛋白凝膠樣品采用乙醇溶液進(jìn)行脫水,加入丙酮和醋酸異戊酯進(jìn)行置換,最后采用CO2臨界點干燥法進(jìn)行干燥后噴金,在掃描電鏡下觀察纖維蛋白支架的形態(tài)。
1.2.4纖維蛋白支架與NSCs的生物相容性1×106個NSCs種植于上述制備的纖維蛋白支架上,隔天半量換液。掃描電鏡標(biāo)本制備,48 h、96 h后分別以2.5%戊二醛固定,梯度乙醇脫水,臨界點冷凍干燥,噴金,掃描電鏡觀察細(xì)胞的形態(tài)和分布。免疫熒光標(biāo)本制備,72 h后用4%多聚甲醛固定,10μm冰凍切片,行Nestin免疫熒光染色,觀察細(xì)胞在支架內(nèi)的生長情況。
1.2.5重型腦損傷模型的制作將SD大鼠(n=48)采用抽簽法隨機(jī)分成4組,每組12只。TBI組(A組)大鼠行顱腦液壓沖擊損傷;TBI+NSC組(B組)經(jīng)顱腦液壓沖擊損傷后給予NSC混合支架治療;TBI+MHT組(C組)經(jīng)顱腦液壓沖擊損傷后給予亞低溫治療;TBI+NSC+MHT組(D組)顱腦液壓沖擊損傷后給予NSC混合支架及亞低溫治療。稱質(zhì)量,6%水合氯醛(36 mg/kg)麻醉,固定于立體定向儀,頭皮正中切開,暴露顱骨,以前囟后3.8 mm、中線右側(cè)2.5 mm為中心,開直徑4.0 mm圓形骨窗;用增強(qiáng)型牙科磷酸鋅水門汀將打擊管固定于顱骨上,在管內(nèi)充滿生理鹽水;連接液壓沖擊腦損傷儀的打擊口,調(diào)整沖擊壓為243.18 kPa,平均時程為20 ms。TBI之后、骨蠟止血,大鼠于溫暖、增氧恢復(fù)室、含食物及水的環(huán)境下進(jìn)行飼養(yǎng)。
1.2.6NSCs移植TBI后即刻行混合支架移植,溶解在40 g/L纖維蛋白原中的1×106個NSCs,與溶解在40 mmol/L Ca?Cl2的40 U/mL凝血酶等體積混合(含抑肽酶50 U/mL),移植入損傷近緣,分4個位點注射,每個位點5 μL。
1.2.7亞低溫聯(lián)合治療在進(jìn)行細(xì)胞移植后即刻接受亞低溫治療。用小動物亞低溫治療儀在30 min內(nèi)將全身降溫至肛溫33℃,維持6 h,然后復(fù)溫至37℃,復(fù)溫速度為0.4℃/h。
1.2.8神經(jīng)功能缺陷評分與Morris水迷宮實驗TBI后0、14、28 d分別行單盲神經(jīng)運動功能檢測。在移植后第14天及第28天通過神經(jīng)功能缺陷評分(modified neurological se?verity score,mNSS)進(jìn)行單盲神經(jīng)功能評分。評分由運動(肌張力、異常活動)、感覺(視覺、觸覺、本體感覺)、反射、平衡試驗組成,評分在0~18分,正常為0分,最大神經(jīng)功能缺失為18分。Morris水迷宮實驗測試大鼠的學(xué)習(xí)記憶能力,大鼠TBI前3 d連續(xù)進(jìn)行水迷宮訓(xùn)練,TBI后記錄大鼠從入水到找到平臺所用時間,即逃避潛伏期。
1.3統(tǒng)計學(xué)方法采用SPSS 19.0進(jìn)行統(tǒng)計處理。計量資料以±s表示,組間比較采用單因素方差分析,組間多重比較采用LSD-t檢驗。P < 0.05為差異有統(tǒng)計學(xué)意義。
2.1纖維蛋白支架與NSCs的生物相容性對凝固后的纖維蛋白支架及混合支架行掃描電鏡觀察,單純纖維蛋白支架在掃描電鏡下的孔隙結(jié)構(gòu),見圖1a;共培養(yǎng)支架孔隙之間有細(xì)胞形態(tài),與支架黏附緊密,見圖1b。共培養(yǎng)支架免疫熒光結(jié)果顯示,Nestin呈持續(xù)陽性表達(dá),見圖2。共培養(yǎng)支架免疫熒光以及掃描電鏡觀察提示,纖維蛋白支架是構(gòu)建可降解、生物相容性好的三維支架材料,能為NSCs提供適宜的細(xì)胞外基質(zhì),起到暫時固定NSCs的作用。
Fig.1 Observation of fibrin scaffold and mixed fibrin scaffold by SEM圖1 纖維蛋白支架與混合支架的掃描電鏡觀察
2.2NSCs存活情況結(jié)果顯示,D組移植的NSCs能夠存活,并分化為神經(jīng)元,見圖3。
2.3NSCs移植與亞低溫對TBI大鼠mNSS的影響TBI后14 d及28 d,B組或C組處理與A組相比都能促進(jìn)mNSS的降低(P < 0.05);D組的mNSS低于B、C和A組(P < 0.01);B組與C組mNSS比較差異無統(tǒng)計學(xué)意義(P>0.05),見表1。
Tab. 1 Comparison of mNSS score after TBI between four groups表1 TBI后各組mNSS評分比較(n=12,分,±s)
Tab. 1 Comparison of mNSS score after TBI between four groups表1 TBI后各組mNSS評分比較(n=12,分,±s)
**P < 0.01;a與A組比較,b與B組比較,c與C組比較,P < 0.05;表2同
組別A組B組C組D組F TBI后14 d 5.42±1.44 4.17±1.03a4.25±1.22a2.75±1.06abc9.973**TBI后28 d 3.75±0.87 2.83±0.94a2.92±0.90a1.42±0.90abc13.838**
2.4NSCs與亞低溫對TBI大鼠逃避潛伏期的影響TBI后14 d及28 d,B組或C組與A組相比都能促進(jìn)逃避潛伏期的縮短(P < 0.05);D組的逃避潛伏期低于B、C和A組(P < 0.01);B組與C組逃避潛伏期差異無統(tǒng)計學(xué)意義(P>0.05),見表2。
Tab. 2 Comparison of escape latency after TBI between four groups表2 各組Morris水迷宮試驗逃避潛伏期比較(n=12,s,±s)
Tab. 2 Comparison of escape latency after TBI between four groups表2 各組Morris水迷宮試驗逃避潛伏期比較(n=12,s,±s)
組別A組B組C組D組F TBI后14 d 73.00±16.87 55.92±13.64a58.75±21.51a44.75±17.01abc8.473**TBI后28 d 63.25±16.41 49.75±12.14a48.83±16.43a33.83±11.51abc7.878**
筆者前期的研究通過皮質(zhì)損傷后直接局部移植NSCs發(fā)現(xiàn),移植細(xì)胞黏附、遷移到損傷區(qū)的比例非常低,很大部分原因是缺乏支撐移植細(xì)胞存活的三維的細(xì)胞外基質(zhì)結(jié)構(gòu),細(xì)胞移植后大部分隨體液丟失[5]。Karlsson等[1]研究發(fā)現(xiàn),當(dāng)移植組織植入大鼠后保持亞低溫(32~33℃)能改善移植物的存活。聯(lián)合亞低溫治療被廣泛用于TBI治療研究[6-7]。亞低溫對TBI的神經(jīng)保護(hù)作用強(qiáng)調(diào)在TBI后的早期應(yīng)用[8],本實驗TBI后的即刻將實驗大鼠進(jìn)行亞低溫治療。實驗鼠與NSCs來源為同種系,基因型相同,NSCs移植到大鼠體內(nèi)后不產(chǎn)生免疫排斥反應(yīng),因此,實驗過程沒有應(yīng)用免疫抑制藥物。本次研究首次采用載有NSCs的纖維蛋白支架用于TBI的局部治療,采用液壓損傷儀行TBI造模,清除血腫后局部注射混合支架。研究發(fā)現(xiàn)與A組相比,B、C、D組的神經(jīng)功能與認(rèn)知能力得到改善。D組能夠追蹤到BrdU標(biāo)記的NSCs。進(jìn)一步的分析發(fā)現(xiàn),當(dāng)纖維蛋白混合支架聯(lián)合亞低溫治療時具有最大的保護(hù)作用。本研究結(jié)果顯示亞低溫能促進(jìn)移植NSCs的存活,亞低溫與干細(xì)胞對大鼠神經(jīng)功能的保護(hù)優(yōu)于其各自的單獨作用。
3.1亞低溫對急性顱腦創(chuàng)傷的神經(jīng)保護(hù)作用低溫狀態(tài)下腦代謝下降,腦組織對氧氣及葡萄糖的消耗減少,使腦組織易于維持氧的供需平衡,并可以減少和抑制氧自由基及興奮性神經(jīng)遞質(zhì)的生成與釋放[9],亞低溫還可以通過抑制某些炎性介質(zhì)(如花生四烯酸等)的生成及釋放[10],改善腦缺血后血腦屏障的通透性,從而可以減輕血腦屏障的破壞和血管源性腦水腫的發(fā)生,改善微環(huán)境,一方面起到神經(jīng)保護(hù)作用,另一方面可能起到促進(jìn)移植NSCs存活的作用。
3.2纖維蛋白支架的優(yōu)點在組織工程技術(shù)領(lǐng)域,三維的支架結(jié)構(gòu)用于調(diào)節(jié)以及引導(dǎo)細(xì)胞生長并促進(jìn)組織再生,支架需具有良好生物相容性、能進(jìn)行生物降解、促進(jìn)細(xì)胞以及生物材料相互作用。一些天然的生物材料如纖維蛋白支架能為宿主提供一個類似的細(xì)胞外基質(zhì)結(jié)構(gòu)。自體纖維蛋白支架因其低纖維蛋白原濃度、不引起炎癥反應(yīng),更適合細(xì)胞的生長[11]。采用纖維蛋白支架模擬NSCs的細(xì)胞外基質(zhì)結(jié)構(gòu),能為移植NSCs提供一暫時的立體生長環(huán)境,防止其隨體液丟失。
3.3神經(jīng)干細(xì)胞的作用機(jī)制研究表明,NSCs移植保護(hù)神經(jīng)系統(tǒng)免受炎癥損傷通過多重機(jī)制,不單是直接的細(xì)胞替代,NSCs能到達(dá)靶器官,并分化成合適的細(xì)胞系[12]。移植細(xì)胞可能在解剖上重建損傷的大腦,移植細(xì)胞與宿主細(xì)胞形成突觸連接,外生的細(xì)胞進(jìn)入顱內(nèi)可以產(chǎn)生神經(jīng)營養(yǎng)因子和生長因子,移植細(xì)胞可以促進(jìn)內(nèi)源性細(xì)胞產(chǎn)生神經(jīng)營養(yǎng)因子和生長因子。內(nèi)源性細(xì)胞和外源性細(xì)胞是動態(tài)變化的,對微環(huán)境都非常敏感,外源性細(xì)胞具有向損傷處遷移的特性[13]。
亞低溫對TBI具有神經(jīng)保護(hù)作用,細(xì)胞移植也廣泛用于中樞神經(jīng)損傷的修復(fù)研究,本研究將亞低溫與神經(jīng)干細(xì)胞聯(lián)合,發(fā)現(xiàn)亞低溫能促進(jìn)移植NSCs的存活,兩者聯(lián)合對神經(jīng)功能的修復(fù)具有協(xié)同作用,但其協(xié)同的機(jī)制以及潛在的應(yīng)用價值有待進(jìn)一步研究。
(圖2、3見插頁)
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(2015-05-05收稿2015-09-25修回)
(本文編輯李鵬)
作者單位:1腦創(chuàng)傷與神經(jīng)疾病研究所,武警后勤學(xué)院附屬醫(yī)院腦科醫(yī)院,天津市神經(jīng)創(chuàng)傷修復(fù)重點實驗室(郵編300162);2遼寧醫(yī)學(xué)院,武警后勤學(xué)院附屬醫(yī)院研究生培養(yǎng)基地
Experimental study of combination of mild hypothermia and fibrin scaffold carrying neural stem cells on repairing traumatic brain injury
LIAO Yuping1,2, CHEN Chong1, LI Xiaohong1, WANG Jingjing1, CHEN Yisheng1, ZHANG Sai1, SUN Hongtao1△
1 Institute of Traumatic Brain Injury and Neurology, Brain Hospital of Affiliated Hospital of Logistics College of Chinese People′s Armed Police Forces, Tianjin Key Labrotary of Neurotrauma Repair, Tianjin 300162, China;
2 Liaoning Medical University, Postgraduate Training Base of Affiliated Hospital of the Logistics University of CAPF
△Corresponding Author E-mail:chenmo333@163.com
Abstract:Objective To investigate the possibility of therapy method in orthotropic transplant fibrin scaffold mixedbook=182,ebook=59neural stem cells (NSCs) after traumatic brain injury (TBI), and combined effects of that fibrin scaffold with mild hypothermia (MHT) on TBI in rats. Methods Neural stem cells were separated from E14 Sprague-Dawley rats, and were co-cultured with fibrin scaffold. Scanning electron microscope was used for observing neural stem cell surface morphology in fibrin scaf?fold, and immunofluorescent staining was introduced for detecting cell types. Forty-eight male Sprague-Dawley rats were randomly divided into four groups: TBI group (A), TBI+NSC group (B), TBI+MHT group (C) and TBI+NSC+MHT group (D). TBI model was built with fluid percussion device in group A. Group B was treated with fibrin scaffold carrying neural stem cells after TBI. Group C was treated with MHT for 6 hours after TBI. Fibrin scaffold mixed BrdU labeled neural stem cells were co-transplanted into cortex damage area of group D and mild hypothermia was given for 6 hours. mNSS (modified neuro?logical severity score) and Morris water maze were examined to evaluate the neurologic function at 14 and 28 days after TBI. The rats were sacrificed at 28 days for brain slices. Immunofluorescent staining was used to examine the migration and differ?ention of NSCs in vivo. Results No obvious morphology changes were observed in NSCs, which were co-cultured in fibrin scaffold. The specific marker Nestin was expressed in detected NSCs by immunofluorescence, which indicated that NSCs were still alive in the co-coture fibrin scaffold. The mNSS scores were significantly lower in group D than those of groupA, B and C at day-14 and day-28 (P < 0.05). Results of Morris water maze showed that the escape latency was significantly short?er in group D than that of group A, B and C (P < 0.05). BrdU labled NSCs was found differentiated into neurons in group D at day 28. ConclusionFibrin scaffold and NSCs have a good biocompatibility and biodegradablity. MHT and fibrin scaffold jointed NSCs improve neurologic function in rat TBI model with the synergistic reaction.
Key words:traumatic brain injury;neural stem cells;fibrin scaffold;mildhypothermia
中圖分類號:R651.15
文獻(xiàn)標(biāo)志碼:A
DOI:10.11958/58859
基金項目:國家自然科學(xué)基金資助項目(81471275,81341113,81271392,81401067);天津市應(yīng)用基礎(chǔ)與前沿技術(shù)研究計劃項目(14JCQN?JC10200)
作者簡介:廖余平(1989),男,碩士研究生,主要從事中樞神經(jīng)創(chuàng)傷修復(fù)研究