幹細胞論壇

美國喬治亞大學的研究團隊日前發現,罹患第一型糖尿病的男性病患可以利用睪丸的精原幹細胞(Spermatogonial Stem Cell;SSC),分化成胰島的β細胞,恢復胰島素的分泌,以降低血糖濃度.

第一型糖尿病為先天性基因的異常導致自體抗體產生,對抗自身的胰島細胞,使胰島素無法正常產生,導致血糖居高不下.第一型糖尿病於任何年齡都可發病,但好發於40歲病人.世界上有5-15%人罹患第一型糖尿病仰賴每天的胰島素施打,並無法作根本的治療.

G. Ian Gallicano科學家日前於美國細胞生物學會(American Society of Cell Biology)上發表研究成果,利用小鼠的動物模式,將一克的睪丸組織分離出一百萬顆精原幹細胞,注射至患有糖尿病老鼠的背部,於一星期內都可以正常分泌胰島素降低血中糖分.

精原幹細胞帶有部份與胰島細胞相同的表面抗原,當離開睪丸組織後,失去原本的營養環境,使細胞恢復原始狀態,能再去分化身體三個胚層.

利用睪丸組織的精原幹細胞進行自體移植,在免疫上不會有排斥的問題.科學家相信,卵巢組織的幹細胞也應具有能力分化出胰島細胞,未來女性糖尿病患也能利用自身幹細胞進行移植.

Sperm stem cells can be turned into insulin-making cells to treat diabetes

Scientists have made insulin-producing cells from sperm stem cells, a technique that could one day be used to treat people with type 1 diabetes.

The disease is caused by the destruction of insulin-producing cells in the pancreas, leading to low levels of the hormone that regulates sugar in the blood. It can develop at any age but usually appears before the age of 40, and particularly in childhood. Around 5-15% of all people with diabetes have type 1 diabetes, which is usually treated with, among other things, daily insulin injections.

In the latest study, G. Ian Gallicano, an associate professor at Georgetown University Medical Centre in Washington DC, transformed the early precursors for human sperm, called spermatogonial stem cells (SSCs), into beta-islet cells, which produce insulin and are normally found in the pancreas. When he transferred these cells into mice, they successfully regulated sugar levels in the rodents' blood.

He presented his team's work today at the American Society of Cell Biology annual meeting in Philadelphia. "No stem cells, adult or embryonic, have been induced to secrete enough insulin yet to cure diabetes in humans, but we know SSCs have the potential to do what we want them to do, and we know how to improve their yield," said Gallicano.

His team extracted human SSCs from the testicles of dead organ donors. "We found that once you take these cells out of the testes niche, they get confused, and will form all three germ layers within several weeks. These are true, pluripotent stem cells," said Gallicano. Pluripotent stem cells can develop into any tissue in the body. Germ layers are groups of cells formed when an embryo grows, each layer corresponding to different cell types in the body.

From a single gram of tissue from human testes, the researchers produced around 1 million stem cells. They showed that these contained biological markers indicating they were similar to beta-islet cells. When these were transplanted into diabetic mice (which were engineered to have no immune system), the rodents' blood sugar levels dropped. This effect lasted for a week, showing that the transplanted cells were producing insulin over this period.

If this technique could be replicated in humans, using a man's own tissue to create replacement insulin would overcome several problems with many of the potential treatments currently being tested for type 1 diabetes. One idea involves transplanting islet cells from dead donors, but this source is limited and the transplant can end up being rejected by the patient's immune system.

Alternative ideas include transplants of adult stem cells that have been reprogrammed to behave like more versatile, embryonic stem cells. Unfortunately, this technique can produce tumours in the tissue.

"This method of obtaining [beta]-islet-like cells solves the problem of immune rejection in male diabetes patients, as treatment based on this research would be autograft, and the cells would be recognised as 'self'," wrote Gallicano in an abstract to his research.

Gallicano added that his work was not confined to treating men. There was no reason, he said, why the fundamental understandings from his team's research could not be extended to egg cells. In women, the precursor stem cells of eggs could be turned into beta-islet-like cells.