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神奇干細(xì)胞讓燒傷患者重見光明
Miracle stem cells help burns victims to see clearly again

Dozens of people whose eyes were severely damaged in chemical accidents have had their sight restored with transplants of their own stem cells．
Researchers say the technique returned normal vision to nearly 100 people． They said one of the patients could see clearly for the first time in more than 60 years．

They were incredibly happy． Some said it was a miracle， study leader Graziella Pellegrini of the University of Modena＇s Center for Regenerative Medicine said．
It was not a miracle． It was simply a technique．

Before and after shots that show the success of the stem cell technique
Stem cell transplants offer hope to the thousands of people worldwide every year who suffer chemical burns on their corneas from heavy-duty cleansers or other substances at work or at home．

In the study researchers took a small number of stem cells from a patient＇s healthy eye， multiplied them in the lab and placed them into the burned eye， where they were able to grow new corneal tissue to replace what had been damaged．
Since the stem cells are from their own bodies， the patients do not need to take anti-rejection drugs．

Currently， people with eye burns can get an artificial cornea， a procedure that carries such complications as infection and glaucoma， or they can receive a transplant using stem cells from a cadaver， but that requires taking drugs to prevent rejection．

The Italian study involved 106 patients treated between 1998 and 2007． Most had extensive damage in one eye， and some had such limited vision that they could only sense light， count fingers or perceive hand motions． Many had been blind for years and had had unsuccessful operations to restore their vision．

The cells were taken from the limbus， the rim around the cornea， the clear window that covers the colored part of the eye． In a normal eye， stem cells in the limbus are like factories， churning out new cells to replace dead corneal cells． When an injury kills off the stem cells， scar tissue forms over the cornea， clouding vision and causing blindness．

In the study， published by the New England Journal of Medicine， the doctors removed scar tissue over the cornea and glued the laboratory-grown stem cells over the injured eye．

Researchers followed the patients for an average of three years and some as long as a decade． More than three-quarters regained sight after the transplant． An additional 13 per cent were considered a partial success． Though their vision improved， they still had some cloudiness in the cornea．

Patients with superficial damage were able to see within one to two months． Those with more extensive injuries took several months longer．

The approach would not help people with damage to the optic nerve or macular degeneration， which involves the retina． Nor would it work in people who are completely blind in both eyes， because doctors need at least some healthy tissue that they can transplant．

Adult stem cells， which are found around the body， are different from embryonic stem cells， which come from human embryos and have stirred ethical concerns because removing the cells requires destroying the embryos．

Dr Sophie Deng， a cornea expert at the UCLA＇s Jules Stein Eye Institute， said the biggest advantage was that the Italian doctors were able to expand the number of stem cells in the lab． This technique is less invasive than taking a large tissue sample from the eye and lowers the chance of an eye injury．

The key is whether you can find a good stem cell population and expand it， she said．

　　本文主要內(nèi)容：研究者稱通過干細(xì)胞移植讓幾十位嚴(yán)重化學(xué)損傷患者的眼睛恢復(fù)了視力，特別值得一提的是，有一位失明了60年的患者因此重新獲得光明。干細(xì)胞移植給全世界化學(xué)燒傷角膜患者帶來了希望，在本研究中，從患者健康眼取下很少量干細(xì)胞，然后在實(shí)驗(yàn)室繁殖，移植到患眼，因?yàn)楦杉?xì)胞來自患者，所以很少發(fā)生排斥。這項(xiàng)在意大利完成的研究發(fā)表在《新英格蘭醫(yī)學(xué)雜志》上，該研究最大的優(yōu)勢在于醫(yī)生們能夠在實(shí)驗(yàn)室內(nèi)完成干細(xì)胞繁殖，比起直接從健眼提取大量組織，大大降低了對另一只好眼睛的損傷。但此法并不適用于視神經(jīng)損傷或黃斑變性的患者，對雙眼全部失明的患者同樣療效甚微。加州大學(xué)洛杉磯Jules Stein眼研究所角膜專家Sophie Deng博士說：“關(guān)鍵在于：你能不能找到適合的干細(xì)胞群然后加以繁殖。”
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