美國(guó)科學(xué)家日前在動(dòng)物大腦內(nèi)植入由胚胎干細(xì)胞培育的神經(jīng)細(xì)胞后發(fā)現(xiàn),，它能夠與其原來(lái)的神經(jīng)細(xì)胞進(jìn)行成功聯(lián)接整合,。此研究成果已經(jīng)發(fā)表在1月20日出版的《神經(jīng)科學(xué)》雜志上,。
健康大腦細(xì)胞之間的聯(lián)接是穩(wěn)定和精確的,，這樣才能確保動(dòng)物正常行為的進(jìn)行,。這一新發(fā)現(xiàn)首次表明,，干細(xì)胞不僅可以培育成為特定的腦細(xì)胞，而且這些由干細(xì)胞培育出來(lái)的腦細(xì)胞還能精確地進(jìn)行聯(lián)接,。
由斯坦福大學(xué)醫(yī)學(xué)院(Stanford Medical School)的詹姆斯·魏曼（James Weimann）博士領(lǐng)導(dǎo)的這支神經(jīng)科學(xué)家組成的小組,，在這項(xiàng)研究中將目光集中在大腦皮層內(nèi)傳送信息的細(xì)胞上，其中一些細(xì)胞負(fù)責(zé)對(duì)肌肉的控制,?；加屑顾钃p傷和肌萎縮側(cè)索硬化癥（ALS）的動(dòng)物個(gè)體將會(huì)導(dǎo)致這些腦細(xì)胞損傷或者丟失。魏曼表示：“實(shí)驗(yàn)證實(shí)，這些由干細(xì)胞培育出來(lái)的腦細(xì)胞能夠長(zhǎng)出聯(lián)連大腦皮層和脊髓的神經(jīng)纖維,。”
為了讓新細(xì)胞能夠成功在大腦里面進(jìn)行聯(lián)接,，研究人員首先必須將非專業(yè)化的干細(xì)胞培育成大腦皮層的特定細(xì)胞,。他們將胚胎干細(xì)胞放在培養(yǎng)皿中進(jìn)行培育,，直到這些細(xì)胞顯示出與成熟的神經(jīng)細(xì)胞相同的許多特征。然后研究人員將培育出來(lái)的神經(jīng)細(xì)胞移植到新生小鼠的大腦中,，具體而言,，是將神經(jīng)細(xì)胞移植到大腦皮層負(fù)責(zé)視覺(jué)、觸覺(jué)和運(yùn)動(dòng)的區(qū)域中,。
直到現(xiàn)在,，如何使這些移植細(xì)胞進(jìn)行正確的聯(lián)接，一直是神經(jīng)系統(tǒng)移植治療中的一個(gè)根本性的問(wèn)題,。在這種情況下,，首先要保證將這些細(xì)胞移植到恰當(dāng)?shù)牡胤剑@樣這些細(xì)胞在成熟后才能在適當(dāng)?shù)拇竽X結(jié)構(gòu)內(nèi)進(jìn)行聯(lián)接,。比如,，正確移植到視覺(jué)皮層的細(xì)胞通常會(huì)聯(lián)接到大腦深處的上丘和腦橋位置，而不會(huì)聯(lián)接到脊髓里,。而移植到腦皮層運(yùn)動(dòng)區(qū)的細(xì)胞會(huì)跟脊髓進(jìn)行聯(lián)接而不是上丘和腦橋,。
雖然沒(méi)有參與這項(xiàng)研究，但是干細(xì)胞生物學(xué)領(lǐng)域?qū)＜荫R亨德拉（Mahendra Rao）對(duì)研究成果進(jìn)行了肯定,，他表示：“該研究證實(shí)了移植的腦細(xì)胞可以在年幼動(dòng)物中進(jìn)行聯(lián)接,。”研究人員還將用于培訓(xùn)可移植細(xì)胞的兩種方法進(jìn)行了比對(duì)，但是僅有其中一種方法達(dá)到了預(yù)期的效果,。馬亨德拉說(shuō)：“研究人員獲得了一種如何培育出合適移植腦細(xì)胞的方法,，這為讓這些細(xì)胞發(fā)揮實(shí)際應(yīng)用邁出了一大步。
目前研究人員正在成年小鼠身上進(jìn)行試驗(yàn),，以探討成年小鼠大腦內(nèi)植入由胚胎干細(xì)胞培育的神經(jīng)細(xì)胞,，是否也會(huì)與其原來(lái)的神經(jīng)細(xì)胞進(jìn)行成功聯(lián)接，如果取得肯定的效果,，將會(huì)進(jìn)一步在人腦內(nèi)進(jìn)行試驗(yàn),。魏曼以及他的同事們也希望弄清楚這些移植的細(xì)胞是如何“知道”采取正確的方法進(jìn)行聯(lián)接的，以及這些聯(lián)接是否會(huì)產(chǎn)生正確的行為,，比如引起視覺(jué)和運(yùn)動(dòng)方面的相關(guān)反應(yīng),。（生物谷Bioon.com）
生物谷推薦原始出處：
The Journal of Neuroscience, January 20, 2010, 30(3):894-904; doi:10.1523/JNEUROSCI.4318-09.2010
Murine Embryonic Stem Cell-Derived Pyramidal Neurons Integrate into the Cerebral Cortex and Appropriately Project Axons to Subcortical Targets
Makoto Ideguchi,1 Theo D. Palmer,2 Lawrence D. Recht,1 and James M. Weimann1
1Departments of Neurology and 2Neurosurgery, Stanford Medical School, Stanford, California 94305
Although embryonic stem (ES) cells have been induced to differentiate into diverse neuronal cell types, the production of cortical projection neurons with the correct morphology and axonal connectivity has not been demonstrated. Here, we show that in vitro patterning is critical for generating neural precursor cells (ES-NPCs) competent to form cortical pyramidal neurons. During the first week of neural induction, these ES-NPCs begin to express genes that are specific for forebrain progenitors; an additional week of differentiation produces mature neurons with many features of cortical pyramidal neurons. After transplantation into the murine cerebral cortex, these specified ES-NPCs manifest the correct dendritic and axonal connectivity for their areal location. ES-NPCs transplanted into the deep layers of the motor cortex differentiate into layer 5 pyramidal neurons and extend axons to distant subcortical targets such as the pons and as far caudal as the pyramidal decussation and descending spinal tract and, importantly, do not extend axons to inappropriate targets such as the superior colliculus (SC). ES-NPCs transplanted into the visual cortex extend axons to the dorsal aspect of the SC and pons but avoid ventral SC and the pyramidal tract, whereas cells transplanted deep into the somatosensory cortex project axons to the ventral SC, avoiding the dorsal SC. Thus, these data establish that ES-derived cortical projection neurons can integrate into anatomically relevant circuits.
