唐杰 戚孟春 胡靜
(1.上海交通大學(xué)醫(yī)學(xué)院附屬第九人民醫(yī)院 口腔頜面外科,上海 200011;2.河北聯(lián)合大學(xué) 口腔系,唐山 063000;3.四川大學(xué)華西口腔醫(yī)學(xué)院 口腔頜面外科學(xué)教研室,成都 610041)
膠質(zhì)細(xì)胞源性神經(jīng)營養(yǎng)因子在
自體靜脈橋修復(fù)面神經(jīng)缺損中促進(jìn)神經(jīng)再生的效應(yīng)
唐杰1戚孟春2胡靜3
(1.上海交通大學(xué)醫(yī)學(xué)院附屬第九人民醫(yī)院 口腔頜面外科,上海 200011;2.河北聯(lián)合大學(xué) 口腔系,唐山 063000;3.四川大學(xué)華西口腔醫(yī)學(xué)院 口腔頜面外科學(xué)教研室,成都 610041)
目的 旨在研究膠質(zhì)細(xì)胞源性神經(jīng)營養(yǎng)因子(GDNF)在自體靜脈橋修復(fù)面神經(jīng)缺損中促進(jìn)神經(jīng)再生的效應(yīng)。方法 選用36只成年雄性新西蘭大白兔作為實(shí)驗(yàn)動物,切除雙側(cè)10mm長面神經(jīng)頰支,制作面神經(jīng)缺損動物模型。以同側(cè)面后靜脈作為神經(jīng)再生管道,修復(fù)面神經(jīng)缺損。靜脈管腔內(nèi)分別注入生理鹽水(A組,n=16)或GDNF溶液(B組,n=16)。分別于手術(shù)后當(dāng)時,及術(shù)后4、8、16周誘發(fā)面神經(jīng)動作電位,評價神經(jīng)功能。于術(shù)后4、8、16周每組分別隨機(jī)處死6只動物,切取術(shù)區(qū)神經(jīng)標(biāo)本,行組織學(xué)與透射電鏡觀察。結(jié)果 手術(shù)后當(dāng)時,2組實(shí)驗(yàn)動物均無動作電位產(chǎn)生;而術(shù)后4、8、16周,2組均有動作電位出現(xiàn)。除術(shù)后4周時動作電位波寬2組無顯著差異外,B組動作電位的波幅在術(shù)后4周和8周均顯著高于A組(P<0.01),而潛伏期顯著短于A組(P<0.01),波寬在術(shù)后8周顯著高于A組(P<0.01)。術(shù)后16周,除動作電位波幅B組顯著高于A組外(P<0.01),波寬和潛伏期2組均無顯著差異。形態(tài)學(xué)及透射電鏡觀察顯示,B組再生神經(jīng)有更多的成熟的有髓神經(jīng)纖維,更早出現(xiàn)有活力的Schwann細(xì)胞。結(jié)論GDNF在自體靜脈橋修復(fù)面神經(jīng)缺損中可有效促進(jìn)神經(jīng)再生;GDNF復(fù)合自體靜脈橋?yàn)榕R床面神經(jīng)缺損修復(fù)提供了一個極具價值的途徑。
面神經(jīng)缺損; 自體靜脈移植; 膠質(zhì)細(xì)胞源性神經(jīng)營養(yǎng)因子; 動作電位
外傷、腫瘤切除或醫(yī)源性因素很容易造成面神經(jīng)損傷與缺損;自體靜脈作為橋接的管道用來修復(fù)神經(jīng)缺損在臨床及動物實(shí)驗(yàn)中已有較多報道[1-4]。盡管自體靜脈作為神經(jīng)再生的管道有其獨(dú)特的優(yōu)越性,但仍然不能早期很好地恢復(fù)神經(jīng)的功能。有研究[5-7]表明:膠質(zhì)細(xì)胞源性神經(jīng)營養(yǎng)因子(glial cell derived neurotrophic factor,GDNF)對神經(jīng)損傷修復(fù)具有重要作用,能夠促進(jìn)外周神經(jīng)再生,逆轉(zhuǎn)軸突切除引起的運(yùn)動神經(jīng)元的死亡,并能顯著促進(jìn)神經(jīng)外胚層細(xì)胞的存活。其能否應(yīng)用于面神經(jīng)缺損的修復(fù),目前國內(nèi)外還缺乏研究報道。本研究旨在探索GDNF在自體靜脈橋修復(fù)面神經(jīng)缺損中促進(jìn)神經(jīng)再生的作用,以尋求早期恢復(fù)面神經(jīng)功能的有效方法,為臨床上面神經(jīng)缺損修復(fù)提供實(shí)驗(yàn)依據(jù)。
選用36只健康成年雄性新西蘭大白兔作為實(shí)驗(yàn)動物(四川大學(xué)華西實(shí)驗(yàn)動物中心提供),體重2.0~2.5 kg。經(jīng)口外在雙側(cè)下頜骨下緣上方1.5 cm、眶下2 cm,從下頜骨后緣至鼻翼做平行于下頜骨下緣的切口,暴露面后靜脈、嚼肌及腮腺組織。截取長約13~14mm的面后靜脈,生理鹽水沖洗管腔,室溫下置于生理鹽水中待用。自腮腺前緣向前分離面神經(jīng)頰支,節(jié)段性切除10mm,保留分布于上唇方肌的主支,制作面神經(jīng)局部缺損動物模型。同時,以同側(cè)面后靜脈作為修復(fù)神經(jīng)缺損的管道,將靜脈袖套式縫合于神經(jīng)2個殘端的神經(jīng)外膜上,面神經(jīng)殘端插入靜脈腔內(nèi)約2mm[1]。實(shí)驗(yàn)動物隨機(jī)分為A、B組(各18只):A組靜脈管腔內(nèi)注入0.4mL生理鹽水;B組則注入0.4mL GDNF溶液(5 ng·mL-1)??p合手術(shù)創(chuàng)口,常規(guī)動物飼養(yǎng);術(shù)后實(shí)驗(yàn)動物肌注青霉素每天每只80萬單位,連續(xù)肌注3 d,預(yù)防創(chuàng)口感染。
1.2.1 神經(jīng)功能恢復(fù)評價 面神經(jīng)功能恢復(fù)評價采用神經(jīng)干動作電位法。測試設(shè)備包括刺激電極和計算機(jī)程控刺激器(中國BL-NewCentury生物機(jī)能實(shí)驗(yàn)軟件)。測試前應(yīng)用測試設(shè)備測定誘發(fā)正常面神經(jīng)神經(jīng)干動作電位的最適刺激強(qiáng)度。
將刺激電極與計算機(jī)程控刺激器的輸出端相連,并將刺激電極置于修復(fù)再生的神經(jīng)近心端,給予1.00 V的單脈沖電刺激(正常面神經(jīng)的最適刺激強(qiáng)度);將記錄電極置于修復(fù)再生神經(jīng)的中份,記錄電極引導(dǎo)的生物電輸入計算機(jī)電位通道接口,經(jīng)程控生物放大器放大,A/D轉(zhuǎn)換,計算機(jī)處理顯示動作電位。
分別于手術(shù)后當(dāng)時、術(shù)后第4、8、16周,從2組動物中隨機(jī)選擇6只動物,全麻下解剖出術(shù)區(qū)面神經(jīng),測定再生神經(jīng)的動作電位。觀察指標(biāo)有神經(jīng)干動作電位的幅度、波寬和潛伏期。
1.2.2 形態(tài)學(xué)及超微結(jié)構(gòu)檢測 于手術(shù)后第4、8、16周,在測定神經(jīng)干動作電位后,麻醉下處死實(shí)驗(yàn)動物(每組每一時間點(diǎn)6只動物),解剖分離再生的面神經(jīng),在距神經(jīng)斷端近中、遠(yuǎn)中各約4mm截取標(biāo)本,標(biāo)記近遠(yuǎn)中方向。左側(cè)面神經(jīng)標(biāo)本用10%中性甲醛固定24~48 h,常規(guī)乙醇脫水、石蠟包埋;并制備5μm厚切片,Harris蘇木精-伊紅染色。
右側(cè)面神經(jīng)標(biāo)本在再生神經(jīng)正中,截取長2mm的標(biāo)本,3%的戊二醛(pH7.3~7.4)4℃固定24 h,磷酸鹽緩沖液沖洗。然后用1%四氧化餓(pH7.3~7.4)4℃二次固定2 h,磷酸鹽緩沖液再次沖洗20min,梯度丙酮逐級脫水,Epon 812環(huán)氧樹脂橫向包埋。制備半薄切片(1μm),美蘭染色,在光鏡下任意選擇15個40μm×40μm的視野,對再生的有髓神經(jīng)纖維用OPTMAS 6.0-2計算機(jī)軟件進(jìn)行計數(shù)。再制備超薄切片,布于覆蓋有Formvar膜的圓形銅載網(wǎng)上,醋酸鈾和枸緣酸鉛雙重染色后透射電鏡觀察,了解神經(jīng)微觀結(jié)構(gòu)及Schwann細(xì)胞再生情況。
1.2.3 統(tǒng)計學(xué)分析 計量資料用均數(shù)±標(biāo)準(zhǔn)差表示。應(yīng)用SPSS 10.0軟件對2組實(shí)驗(yàn)動物再生神經(jīng)動作電位的參數(shù)和再生有髓神經(jīng)纖維數(shù)目進(jìn)行獨(dú)立樣本的t檢驗(yàn),比較2組的差異。P≤0.05表示差異具有統(tǒng)計學(xué)意義。
所有實(shí)驗(yàn)動物均很好地耐受了手術(shù),術(shù)后創(chuàng)口無感染,并能自由取食。本研究成功建立了自體靜脈修復(fù)兔面神經(jīng)缺損的動物模型。
正常面神經(jīng)最適刺激強(qiáng)度(1.00±0.11)V,神經(jīng)動作電位波幅為(12.25±0.33)mV,波寬為9.06ms,潛伏期為(1.26±0.03)ms。2組實(shí)驗(yàn)動物在手術(shù)后當(dāng)時(0周),給予電刺激后均無動作電位產(chǎn)生;而術(shù)后第4、8、16周,均出現(xiàn)動作電位,但動作電位參數(shù)二者有明顯差異(圖1,表1)。
圖1 術(shù)后4周A組(A)和B組(B)再生神經(jīng)動作電位Fig 1 Action potential of group A(A)and group B(B)4 weeks after operation
手術(shù)后4周,2組再生神經(jīng)動作電位的波幅和潛伏期比較均有統(tǒng)計學(xué)差異(P<0.01),A組波幅顯著小于B組,而潛伏期長于B組。波寬2組無顯著差異(P>0.05)。手術(shù)后8周,2組神經(jīng)動作電位的波幅、波寬和潛伏期比較均有統(tǒng)計學(xué)差異(P<0.01),A組波幅、波寬顯著小于B組,而潛伏期長于B組。手術(shù)后16周,2組神經(jīng)動作電位除波幅A組顯著小于B組外(P<0.01),波寬和潛伏期二組比較無統(tǒng)計學(xué)差異。手術(shù)后隨著時間的延長,2組神經(jīng)動作電位的波寬和波幅逐漸增加,而潛伏期逐漸縮短,說明神經(jīng)功能趨于正常;但是直到術(shù)后16周,2組面神經(jīng)動作電位3項(xiàng)參數(shù)與正常值比較均有統(tǒng)計學(xué)差異(P<0.01)。
表1 不同時間點(diǎn)再生面神經(jīng)動作電位比較Tab 1 Analysis of action potential of regenerated facial nerve in differentiation time points
術(shù)后4、8周2組再生神經(jīng)纖維經(jīng)常形態(tài)見圖2。
圖2 術(shù)后4、8周2組再生神經(jīng)纖維Fig 2 Regenerated myeliated nerve fibers of two groups after 4 and 8 weeks of operation
手術(shù)后4周,2組靜脈橋管內(nèi)可見再生神經(jīng)纖維形成,成束排列,主要為無髓神經(jīng)纖維,有髓神經(jīng)纖維較少,且髓鞘壁較??;神經(jīng)束間可見新生血管,并可見大量的膠原纖維,鞘壁Schwann細(xì)胞增生活躍,核大,異染色質(zhì)分布不均勻(圖2A,2D)。再生神經(jīng)只占據(jù)靜脈管腔的一部分,且神經(jīng)纖維數(shù)目A組明顯少于B組。手術(shù)后8周,2組再生神經(jīng)纖維數(shù)目均明顯增加(表2)。2組比較,A組神經(jīng)纖維較稀疏,有髓神經(jīng)數(shù)目較少,膠原纖維較多;而B組再生神經(jīng)纖維密集成束,有髓神經(jīng)纖維較多,膠原纖維較少;有髓神經(jīng)纖維髓鞘壁較厚(圖2B,2C)。術(shù)后16周,2組新生神經(jīng)纖維數(shù)目繼續(xù)增加,有髓神經(jīng)纖維數(shù)目在新生軸索中占絕對多數(shù),髓鞘壁進(jìn)一步增厚,少見活躍的Schwann細(xì)胞;但B組神經(jīng)纖維數(shù)目仍明顯多于A組。
表2 2組再生有髓神經(jīng)纖維數(shù)比較Tab 2 Com paration of new ly regenerated m yeliated nerve fibers between two groups ±s
表2 2組再生有髓神經(jīng)纖維數(shù)比較Tab 2 Com paration of new ly regenerated m yeliated nerve fibers between two groups ±s
注:△2組比較,P<0.01。
組別 術(shù)后4周△ 術(shù)后8周△ 術(shù)后16周A 728±36 1 974±86 4 340±179 B 1 623±141 3 012±77 4 697±291
外傷、腫瘤切除或醫(yī)源性因素等很容易造成面神經(jīng)缺損。面神經(jīng)缺損的再生修復(fù)受到許多因素的影響。Longo等[8]認(rèn)為神經(jīng)再生的成功與否有賴于是否存在適宜神經(jīng)再生的生理微環(huán)境。該適宜的生理微環(huán)境包括具有活力的Schwann細(xì)胞、各種神經(jīng)生長因子(nerve growth factors,NGF)、營養(yǎng)因子(nutrient promoting factor,NPF)的參與、局部良好的血液供應(yīng)和供神經(jīng)生長的空間神經(jīng)導(dǎo)管系統(tǒng)。可以作為神經(jīng)再生導(dǎo)管系統(tǒng)的材料有很多,多采用自體導(dǎo)管系統(tǒng)和合成生物材料。后者有硅膠管、膠原管、聚四氟乙烯管等[9-11]。自體導(dǎo)管系統(tǒng)多為自體動、靜脈[1-4]。
自體靜脈作為神經(jīng)再生導(dǎo)管有其獨(dú)特的優(yōu)越性:不會引起免疫反應(yīng)和供區(qū)功能障礙、容易獲取、不需要開辟第二個手術(shù)區(qū);管壁薄,有一定的通透性,既能阻擋周圍結(jié)締組織的長入,又有利于營養(yǎng)物質(zhì)穿透靜脈壁。Levine等[12]的研究還發(fā)現(xiàn)靜脈壁上有神經(jīng)生長因子的表達(dá),在神經(jīng)生長過程中可能會起到促進(jìn)神經(jīng)生長的作用。臨床及實(shí)驗(yàn)研究[1-4]均證明:自體靜脈可用以修復(fù)外周神經(jīng)缺損,使神經(jīng)功能達(dá)到一定程度的恢復(fù)。但是,自體靜脈修復(fù)神經(jīng)缺損是緩慢的過程,而早期神經(jīng)功能的恢復(fù)不僅可盡快行使相應(yīng)的功能,而且可以避免因?yàn)樯窠?jīng)功能缺失而引起的肌肉萎縮。因此,尋求早期促進(jìn)神經(jīng)功能恢復(fù)的方法仍然是神經(jīng)再生修復(fù)領(lǐng)域研究的重點(diǎn)。
GDNF對神經(jīng)再生有重要促進(jìn)作用。Mograbi等[7]研究表明:GDNF可通過提高Akt活性對抗ERK途徑引起的神經(jīng)外胚層細(xì)胞凋亡。GDNF基因轉(zhuǎn)染的Schwann細(xì)胞可提高運(yùn)動神經(jīng)元存活,并有效促進(jìn)外周神經(jīng)再生[5]。GDNF還可通過作用于Schwann細(xì)胞內(nèi)的信號通路,促進(jìn)其遷移,并在有髓神經(jīng)形成早期發(fā)揮作用[13]。
本研究在采用自體面靜脈橋修復(fù)面神經(jīng)缺損的基礎(chǔ)上,應(yīng)用GDNF來促進(jìn)神經(jīng)的再生修復(fù)。實(shí)驗(yàn)結(jié)果表明,在手術(shù)后4周,應(yīng)用GDNF組面神經(jīng)動作電位的波幅顯著高于對照組,而潛伏期顯著小于對照組;說明實(shí)驗(yàn)組面神經(jīng)功能優(yōu)于對照組,GDNF發(fā)揮了促進(jìn)面神經(jīng)再生的作用。而GDNF的作用在手術(shù)后8周更為明顯,實(shí)驗(yàn)組神經(jīng)動作電位的波幅、波寬均顯著高于對照;而潛伏期則顯著小于對照。到手術(shù)后16周,GDNF的作用明顯減弱,除實(shí)驗(yàn)組波幅顯著高于對照組外,波寬及潛伏期2組均無顯著差異。上述結(jié)果說明,GDNF具有在早期(4、8周)明顯促進(jìn)面神經(jīng)再生的作用,其作用在術(shù)后8周達(dá)到最高;而隨著時間的延長,GDNF的作用逐漸消退。形態(tài)學(xué)及超微結(jié)構(gòu)觀察也表明,GDNF處理組有髓神經(jīng)數(shù)目、Schwann細(xì)胞活躍程度及新生血管情況均明顯優(yōu)于對照組。進(jìn)一步證實(shí)了GDNF促進(jìn)神經(jīng)再生的效應(yīng)。
需要指出的是,在本研究中雖然GDNF可在自體靜脈橋修復(fù)面神經(jīng)缺損中有效促進(jìn)神經(jīng)再生,一定程度上在早期恢復(fù)了面神經(jīng)功能;但GDNF促進(jìn)面神經(jīng)再生的作用仍有限,直到術(shù)后16周,GDNF組再生神經(jīng)功能尚未恢復(fù)正常,這可能與以下2個因素有關(guān):首先,GDNF為膠質(zhì)細(xì)胞源性的神經(jīng)生長因子,需要作用于神經(jīng)節(jié)細(xì)胞才可以起到促進(jìn)神經(jīng)生長的作用[6],本研究是把GDNF注入靜脈的橋管內(nèi),GDNF可能需要沿近心端神經(jīng)軸索上溯至神經(jīng)節(jié)細(xì)胞才能對其產(chǎn)生修復(fù)作用。因此表現(xiàn)為在最早期促進(jìn)神經(jīng)修復(fù)的作用較弱。其次,本實(shí)驗(yàn)為一次性給藥,經(jīng)過長時間機(jī)體的作用,GDNF會被消耗或崩解,這可能是后期GDNF作用有限的原因。如果采用在距離神經(jīng)節(jié)細(xì)胞較近的部位比如莖乳孔給藥,或者采用持續(xù)或多次給藥的方法可能會收到更好的效果。
本研究在采用自體面靜脈橋修復(fù)面神經(jīng)缺損的基礎(chǔ)上,應(yīng)用GDNF有效促進(jìn)了面神經(jīng)缺損的再生,在一定程度上促進(jìn)了神經(jīng)功能的早期修復(fù)。該方法對臨床面神經(jīng)缺損的修復(fù)具有重要的借鑒意義。
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(本文編輯 湯亞玲)
Effect of glial cell derived neurotrophic factor on regeneration of facial nerve defects by autogenous vein conduit
TANG Jie1,QI Meng-chun2,HU Jing3.(1.Dept.of Oral and Maxillofacial Surgery,The Ninth People’s Hospital,Shanghai Jiao Tong University School of Medicine,Shanghai200011,China;2.Dept.of Stomatology, Hebei United University,Tangshan063000,China;3.Dept.of Oral and Maxillofacial Surgery,West China College of Stomatology,Sichuan University,Chengdu610041,China)
ObjectiveTo study the effects of glial cell derived neurotrophic factor(GDNF)on regeneration of facial nerve defects by autogenous facial vein conduit.MethodsThirty-six rabbits were used in this study and 10 mm-length facial nerve defects were made on both sides of all animals.The nerve gaps were bridged using autoge-nous posterior facial vein graft of the same side.The animals
injection of either saline(group A,n= 16)or GDNF(group B,n=16)into the veins.Nerve function was evaluated by evoking nerve action potential immediately after operation and 4,8 and 16 weeks after operation.Regenerated nerve samples were harvested at 4,8, and 16 weeks after operation and processed for histology and transmitting electron microscopic examination(TEM). Results Action potential did not exist immediately after operation but it was evoked at 4,8,and 16 weeks in both groups.At 4 and 8 weeks after operation,the amplitude and width of action potential were significantly higher in group B than group A(P<0.01),except wave width at 4 weeks,which showed no significant differences,while the latency period was significantly shorter in group B than that in group A(P<0.01).At 16 weeks,action potential was similar between two groups,except wave amptitude,which was higher in group B than group A(P<0.01).Morphologic and TEMexaminations showed more matured myelinated nerve fibers and active Schwann’s cells in group B when compared group A during the whole regeneration process.ConclusionGDNF can promote nerve regeneration at early stage during reconstruction of facial nerve defects by autogenous faical vein conduit and combination of GDNF and autogenous vein graft provides a valuable method for clinical reconstruction of facial nerve defects.
facial nerve defect; autogenous vein graft; glial cell derived neurotrophic factor; action potential
R 622
A
10.3969/j.issn.1000-1182.2011.01.021
1000-1182(2011)01-0087-05
2010-04-10;
2010-06-24
四川省科技攻關(guān)基金資助項(xiàng)目(05SG022-019-3)
唐杰(1973—),女,河南人,副主任醫(yī)師,博士
胡靜,Tel:028-85502339