A new study may have hit upon another way to improve stem cells' ability to help repair damaged tissue. While stem cells can rapidly grow into any kind of new tissue, they aren't always able to encourage new blood vessels to grow so that the tissue stays alive. But in a new study, published in the Proceedings of the National Academy of Sciences, scientists describe a way around the problem. The researchers used nanoparticles to ferry a key gene into the stem cells, which caused the cells to recruit new blood vessels, thus fueling tissue growth.

    The nanoparticles carried a gene （VEGF） that is known to stimulate new blood vessel growth. When the modified cells were injected into mice whose hind limbs had been injured, the tissue that regrew to repair the damage had three times the blood vessel density of similar tissue in mice given unmodified cells. Four weeks later, only 20 per cent of the mice given modified cells had lost limbs, compared with 60 per cent in mice that received unmodified cells.

    The researchers are optimistic about the nanoparticle approach, however they state in the study that the effect may be transient. They note that there was a significant increase in VEGF levels in mouse muscle two days following cell grafting, but VEGF levels produced by the cells dropped sharply after four days. They say that using a virus to transmit the gene may be a better approach to stimulate new blood vessels over a longer period of time. However, the viral approach is not without risks–viruses can integrate into the genome of cells and linger permanently, potentially causing cancer or immune reactions.

    一项新的研究偶然发现了提高干细胞能力，促进受损组织愈合的另一种方法。干细胞虽然能生长为各种组织，但却不能一直促进新血管的生长，使新组织存活。这项研究的论文发表在《美国国家科学院学报》上，文中科学家阐述了解决这一问题的方法。研究人员使用纳米粒子将一个关键基因导入干细胞，这个基因可使细胞长出新的血管，从而促进组织生长。

    纳米粒子承载一个人所共知的可刺激新血管生长的基因 （VEGF） .将改性细胞注入后腿受伤的白鼠体内后，重新生长的修复创伤的组织中，血管密度是注入未经改性的细胞的白鼠相似组织中的三倍。

    研究人员对纳米粒子法持乐观态度，然而，他们在论文中称，这种作用也许是短暂的。他们说，细胞移植后的头两天，白鼠肌肉中VEGF水平显着增加，但四天之后，干细胞产生的VEGF水平急剧下降。还说，用病毒传输关键基因，从而较长时间地刺激新血管生长可能是个好办法。但是，这种方法必须使用危险性病毒，并可将病毒带进细胞的基因组，并永久滞留其中，有可能导致癌症或免疫反应。