美國(guó)科學(xué)家4月28日在新一期美國(guó)《國(guó)家科學(xué)院院刊》（PNAS）上發(fā)表報(bào)告說(shuō),，他們?cè)趯?shí)驗(yàn)鼠的腦垂體中首次發(fā)現(xiàn)了成體干細(xì)胞。
成體干細(xì)胞是分化能力稍遜于胚胎干細(xì)胞的一類(lèi)重要干細(xì)胞,，存在于成年機(jī)體內(nèi),，可以不斷分化并修復(fù)受損組織、替代凋亡細(xì)胞等,?？蒲腥藛T此前曾報(bào)告在毛囊、肝臟,、肌肉等組織或器官中發(fā)現(xiàn)過(guò)成體干細(xì)胞,，但從未在腦垂體中發(fā)現(xiàn)這種干細(xì)胞。
垂體是大腦內(nèi)分泌激素的腺體。人腦內(nèi)的垂體大小僅如豌豆,，分泌的激素負(fù)責(zé)調(diào)控體內(nèi)各處的正常運(yùn)轉(zhuǎn),。老鼠的垂體從胚胎階段即開(kāi)始發(fā)育，但出生幾星期后,，垂體還會(huì)經(jīng)歷第二個(gè)發(fā)育高峰期,。
美國(guó)科爾德斯普林實(shí)驗(yàn)室等機(jī)構(gòu)的科學(xué)家在新研究中發(fā)現(xiàn)，實(shí)驗(yàn)鼠的腦垂體中共有6個(gè)主要的干細(xì)胞系,，每一個(gè)干細(xì)胞都能分化出這6個(gè)干細(xì)胞系并分泌不同的激素,。科學(xué)家說(shuō),，正是這類(lèi)干細(xì)胞不斷分化,，使得實(shí)驗(yàn)鼠在出生后腦垂體仍然經(jīng)歷發(fā)育高峰。
由于垂體分泌的激素與外界的壓力,、環(huán)境變化以及懷孕等自身變化息息相關(guān),，科學(xué)家認(rèn)為，有關(guān)成體干細(xì)胞的新發(fā)現(xiàn)表明,，即便發(fā)育到了青春期甚至成年期,，老鼠的腦垂體仍然可通過(guò)成體干細(xì)胞分化的途徑，不斷適應(yīng)身體內(nèi)外的變化,。
通常的成體干細(xì)胞在胚胎發(fā)育期也作出分化貢獻(xiàn),，并在機(jī)體成年后一直保持干細(xì)胞的“身份”。與此不同的是,，在實(shí)驗(yàn)鼠腦垂體中發(fā)現(xiàn)的成體干細(xì)胞在胚胎時(shí)期沒(méi)有作出任何貢獻(xiàn),。科學(xué)家因此推斷,，成年老鼠的腦垂體中有兩種看似一樣,、實(shí)則不同的激素分泌細(xì)胞，一種直接來(lái)自胚胎發(fā)育時(shí)期,，另一種是出生以后才出現(xiàn)的,，這可以使它們以不同的方式適應(yīng)不斷變化的生長(zhǎng)條件。（來(lái)源：新華網(wǎng) 張忠霞）
生物谷推薦原始出處：
（PNAS）,，doi：10.1073/pnas.0801644105,，Anatoli S. Gleiberman，Grigori Enikolopov
Genetic approaches identify adult pituitary stem cells
Anatoli S. Gleiberman*,, Tatyana Michurina, Juan M. Encinas, Jose L. Roig, Peter Krasnov, Francesca Balordi, Gord Fishell, Michael G. Rosenfeld*,¶, and Grigori Enikolopov,¶
*Howard Hughes Medical Institute, Department of Medicine, University of California at San Diego School of Medicine, La Jolla, CA 92093-0648; Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724; and Smilow Neuroscience Program and Department of Cell Biology, New York University School of Medicine, New York, NY 10016
Contributed by Michael G. Rosenfeld, February 21, 2008 (sent for review January 11, 2008)
Abstract
Adult tissues undergo continuous cell turnover in response to stress, damage, or physiological demand. New differentiated cells are generated from dedicated or facultative stem cells or from self-renewing differentiated cells. Here we describe a different stem cell strategy for tissue maintenance, distinct from that observed for dedicated or facultative stem cells. We report the presence of nestin-expressing adult stem cells in the perilumenal region of the mature anterior pituitary and, using genetic inducible fate mapping, demonstrate that they serve to generate subsets of all six terminally differentiated endocrine cell types of the pituitary gland. These stem cells, while not playing a significant role in organogenesis, undergo postnatal expansion and start producing differentiated progeny, which colonize the organ that initially entirely consisted of differentiated cells derived from embryonic precursors. This generates a mosaic organ with two phenotypically similar subsets of endocrine cells that have different origins and different life histories. These parallel but distinct lineages of differentiated cells in the gland may help the maturing organism adapt to changes in the metabolic regulatory landscape.
