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.

    一項(xiàng)新的研究偶然發(fā)現(xiàn)了提高干細(xì)胞能力，促進(jìn)受損組織愈合的另一種方法。干細(xì)胞雖然能生長為各種組織，但卻不能一直促進(jìn)新血管的生長，使新組織存活。這項(xiàng)研究的論文發(fā)表在《美國國家科學(xué)院學(xué)報(bào)》上，文中科學(xué)家闡述了解決這一問題的方法。研究人員使用納米粒子將一個(gè)關(guān)鍵基因?qū)�入干�?xì)胞，這個(gè)基因可使細(xì)胞長出新的血管，從而促進(jìn)組織生長。

    納米粒子承載一個(gè)人所共知的可刺激新血管生長的基因 （VEGF） .將改性細(xì)胞注入后腿受傷的白鼠體內(nèi)后，重新生長的修復(fù)創(chuàng)傷的組織中，血管密度是注入未經(jīng)改性的細(xì)胞的白鼠相似組織中的三倍。

    研究人員對納米粒子法持樂觀態(tài)度，然而，他們在論文中稱，這種作用也許是短暫的。他們說，細(xì)胞移植后的頭兩天，白鼠肌肉中VEGF水平顯著增加，但四天之后，干細(xì)胞產(chǎn)生的VEGF水平急劇下降。還說，用病毒傳輸關(guān)鍵基因，從而較長時(shí)間地刺激新血管生長可能是個(gè)好辦法。但是，這種方法必須使用危險(xiǎn)性病毒，并可將病毒帶進(jìn)細(xì)胞的基因組，并永久滯留其中，有可能導(dǎo)致癌癥或免疫反應(yīng)。