美國食品藥物管理局(FDA)已允許胚胎幹細胞對眼底黃斑變性症(Stargardt's macular degeneration)的病患實施臨床試驗.

眼底黃斑變性症(Stargardt's macular degeneration)為體染色體隱性遺傳，也可為顯性遺傳。病理特徵是在視網膜色素上皮有彌漫性黃色斑點，發病年齡大多數在10歲左右，視力會緩慢下降，最終視力多在0.1。

 

今年十月，美國Geron生技公司獲得FDA批准，為一名脊髓損傷患者進行人類胚胎幹細胞臨床治療試驗，成為首家進行人類胚胎幹細胞人體臨床試驗的公司。

而美國Advanced cell techology(ACT)生技公司為第二個獲准利用胚胎幹細胞近進行臨床試驗的公司,注射數千顆的胚胎幹細胞於12名患有先天性眼底黃斑變性症的成人眼睛中,首要目標是評估該治療的安全性,並預計病患需數個禮拜時間進行修補,最快可以在六個星期後重見光明.

此次試驗用的胚胎幹細胞是藉由體外授精,分裂為八個細胞時,取出其中一顆,誘導成視網膜上皮細胞(Retinal Pigment Epithelial;RPE)打入患者的眼睛.此治療已在動物實驗上獲得證實,僅用少量的胚胎幹細胞達到改善情形,希望人體注射大量的胚胎幹細胞能達到相同的功效.

美國Advanced cell techology(ACT)生技公司於11月30日再度向FDA的新藥臨床試驗(IND)提出申請,利用相同的RPE細胞治療乾性老年性黃斑病變(Dry Age-Related Macular Degeneration;Dry AMD).

 估計全世界目前有三千萬的人罹患AMD,其中美國就占有一半的病人.AMD發病年齡主要在65-85歲,因老化使得黃斑的視網膜感光細胞退化,影響視力.

不管是[眼底黃斑變性症]或是[乾性老年性黃斑病變],目前都沒有有效著治療方式,利用胚胎幹細胞的臨床試驗預計將可造福更多的人.

 

Stem cells could help blind patients to see within six weeks

 

Blind patients suffering from a type of eye disease that strikes in childhood will become the second group of people in the world to receive stem cells derived from spare IVF embryos left over from fertility treatment.

The US Food and Drug Administration (FDA) has given the go-ahead for the controversial transplant of embryonic stem cells into the eyes of patients with Stargardt's macular degeneration, where the light-sensitive retina cells at the back of eye are destroyed.

The announcement follows the first injection of embryonic stem cells into a patient in the US who is partially paralysed as a result of a spinal cord injury. Last October, a US biotechnology company, Geron, announced the start of the first clinical trial of embryonic stem cells with the hope of repairing damaged nerves.

Another US biotechnology firm, Advanced Cell Technology, has now been given approval for a second clinical trial involving the injection of thousands of embryonic stem cells into the eyes of a dozen adult patients with a juvenile form of macular degeneration.

Robert Lanza, the company's chief scientific officer, said that the first patient could receive the stem cell transplants early in the new year and although the trial is designed primarily to assess safety, the first signs of visual improvement may be apparent within weeks.

"Talking to the clinicians, we could see something in six weeks, that's when we think we may see some improvements. It really depends on individual patients but that's a reasonable time frame when something may start to happen," Dr Lanza said.

Embryonic stem cells, which are derived from IVF embryos just a few days old, have the ability to develop into any of the dozens of specialised cells of the body. Researchers believe they could revolutionise medicine because of their ability to repair damaged tissues and organs in situ without the need for whole-organ transplants.

However, "pro-life" groups such as the Roman Catholic Church are bitterly opposed to the practice which they say involves the deliberate destruction of potential human beings – even if they are only 3-day old embryos.

Last week, a Glasgow man in his 60s with stroke damage to his brain became the world's first person to receive injections of stem cells derived from an aborted foetus as part of a clinical trial to test the safety of foetal stem cells, which are believed to be less powerful than embryonic stem cells in terms of regenerative ability.

Dr Lanza said that the clinical trial on patients with Stargardt's disease will involve several clinics across America, including the Casey Eye Institute in Portland, Oregon, the University of Massachusetts in Worcester and the New Jersey Medical School, Newark.

The first three patients will receive injections of 50,000 embryonic stem cells, the second set will receive 100,000 cells and the highest dose will be 200,000 cells. Animal studies have shown dramatic improvements in eye sight following the lowest dose, Dr Lanza said. "We've tested these cells in animal models of eye disease. In rats, we've seen 100 per cent improvement in visual performance over untreated animals without any adverse effects," he said.