Ratajczak J, Miekus K, Kucia M, Zhang J, Reca R, Dvorak P, Ratajczak M Z
Stem Cell Biology Program, James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA.
Leukemia. 2006 May;20(5):847-56. doi: 10.1038/sj.leu.2404132.
Membrane-derived vesicles (MV) are released from the surface of activated eucaryotic cells and exert pleiotropic effects on surrounding cells. Since the maintenance of pluripotency and undifferentiated propagation of embryonic stem (ES) cells in vitro requires tight cell to cell contacts and effective intercellular signaling, we hypothesize that MV derived from ES cells (ES-MV) express stem cell-specific molecules that may also support self-renewal and expansion of adult stem cells. To address this hypothesis, we employed expansion of hematopoietic progenitor cells (HPC) as a model. We found that ES-MV (10 microg/ml) isolated from murine ES cells (ES-D3) in serum-free cultures significantly (i) enhanced survival and improved expansion of murine HPC, (ii) upregulated the expression of early pluripotent (Oct-4, Nanog and Rex-1) and early hematopoietic stem cells (Scl, HoxB4 and GATA 2) markers in these cells, and (iii) induced phosphorylation of MAPK p42/44 and serine-threonine kinase AKT. Furthermore, molecular analysis revealed that ES-MV express Wnt-3 protein and are selectively highly enriched in mRNA for several pluripotent transcription factors as compared to parental ES cells. More important, this mRNA could be delivered by ES-MV to target cells and translated into the corresponding proteins. The biological effects of ES-MV were inhibited after heat inactivation or pretreatment with RNAse, indicating a major involvement of protein and mRNA components of ES-MV in the observed phenomena. We postulate that ES-MV may efficiently expand HPC by stimulating them with ES-MV expressed ligands (e.g., Wnt-3) as well as increase their pluripotency after horizontal transfer of ES-derived mRNA.
膜衍生囊泡（MV）从活化的真核细胞表面释放，并对周围细胞发挥多效性作用。由于体外胚胎干细胞（ES）的多能性维持和未分化增殖需要紧密的细胞间接触和有效的细胞间信号传导，我们推测源自ES细胞的MV（ES-MV）表达干细胞特异性分子，这些分子也可能支持成体干细胞的自我更新和扩增。为了验证这一假设，我们采用造血祖细胞（HPC）的扩增作为模型。我们发现，在无血清培养中从鼠ES细胞（ES-D3）分离的ES-MV（10微克/毫升）显著：（i）提高了鼠HPC的存活率并促进其扩增；（ii）上调了这些细胞中早期多能性（Oct-4、Nanog和Rex-1）和早期造血干细胞（Scl、HoxB4和GATA 2）标志物的表达；（iii）诱导丝裂原活化蛋白激酶p42/44和丝氨酸-苏氨酸激酶AKT的磷酸化。此外，分子分析显示ES-MV表达Wnt-3蛋白，并且与亲代ES细胞相比，在几种多能转录因子的mRNA中选择性高度富集。更重要的是，这种mRNA可以由ES-MV传递到靶细胞并翻译成相应的蛋白质。热灭活或用RNA酶预处理后，ES-MV的生物学效应受到抑制，表明ES-MV的蛋白质和mRNA成分在观察到的现象中起主要作用。我们推测，ES-MV可能通过用ES-MV表达的配体（如Wnt-3）刺激HPC来有效扩增HPC，并在ES衍生的mRNA水平转移后增加其多能性。
