神奇干细胞让烧伤患者重见光明
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．

　　本文主要内容：研究者称通过干细胞移植让几十位严重化学损伤患者的眼睛恢复了视力，特别值得一提的是，有一位失明了60年的患者因此重新获得光明。干细胞移植给全世界化学烧伤角膜患者带来了希望，在本研究中，从患者健康眼取下很少量干细胞，然后在实验室繁殖，移植到患眼，因为干细胞来自患者，所以很少发生排斥。这项在意大利完成的研究发表在《新英格兰医学杂志》上，该研究最大的优势在于医生们能够在实验室内完成干细胞繁殖，比起直接从健眼提取大量组织，大大降低了对另一只好眼睛的损伤。但此法并不适用于视神经损伤或黄斑变性的患者，对双眼全部失明的患者同样疗效甚微。加州大学洛杉矶Jules Stein眼研究所角膜专家Sophie Deng博士说：“关键在于：你能不能找到适合的干细胞群然后加以繁殖。”
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　（黄正 译）