Zipori Dov
Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel.
Blood Cells Mol Dis. 2004 Nov-Dec;33(3):211-5. doi: 10.1016/j.bcmd.2004.08.019.
Plastic behavior of cells is a hallmark of embryonic development. The emergence of primary mesenchyme from within the inner cell mass entails the first epithelial-mesenchymal transition step that is then followed by sequential transitions; the formation of new tissues and organs requires transitions from mesenchyme into epithelium and vice versa. Although it is currently believed that in the adult such transitions do not persist, the frequent occurrence of mesenchymal stem cells (MSCs) in various tissues of the adult organisms, and the reported plasticity of such adult mesenchymal cells, raises the question as to whether the frequency of mesenchymal epithelial transitions in the adult have been underestimated. Indeed, adult mesenchymal stem cells have been reported to differentiate in culture into a multitude of mature cell types including epithelial cells. This opens the way to the use of these stem cells for the construction of new tissues and organs for therapeutic purposes, but the question is still open as to whether mesenchymal stem cells transdifferentiate also in vivo. The molecular mechanism that underlies the plasticity of mesenchymal stem cells and their capacity to transdifferentiate is unresolved. We found that these cells have a promiscuous gene expression pattern; mesenchymal cells, whether primary or cloned cell lines, express T cell receptor (TCR) beta and alpha genes, along with other components of the TCR complex. These cells may therefore be in a standby state, in which many gene families are expressed at a low level thereby making the cell readily capable of shifting fates.
细胞的可塑性是胚胎发育的一个标志。内细胞团中原始间充质的出现是上皮-间充质转化的第一步，随后是一系列的转化；新组织和器官的形成需要间充质向上皮的转化以及上皮向间充质的转化。尽管目前认为在成体中这种转化不会持续存在，但成体生物各种组织中频繁出现的间充质干细胞（MSC）以及报道的这类成体间充质细胞的可塑性，引发了一个问题，即成体中间充质上皮转化的频率是否被低估了。事实上，据报道成体间充质干细胞在培养中可分化为多种成熟细胞类型，包括上皮细胞。这为利用这些干细胞构建用于治疗目的的新组织和器官开辟了道路，但间充质干细胞在体内是否也会发生转分化的问题仍然悬而未决。间充质干细胞可塑性及其转分化能力的分子机制尚未得到解决。我们发现这些细胞具有混杂的基因表达模式；间充质细胞，无论是原代细胞还是克隆细胞系，都表达T细胞受体（TCR）β和α基因以及TCR复合体的其他成分。因此，这些细胞可能处于一种备用状态，其中许多基因家族以低水平表达，从而使细胞能够轻易地改变命运。
