冷冻保存卵子的新技术

    生物谷：美国乔治亚医学院（Medical  College  of  Georgia）的研究者，于近日发表了一项新的冷冻保存人类卵子的技术，造福许多有不孕疑虑的患者。

    患有血癌、子宫颈癌、子宫癌、乳癌与卵巢癌的年轻女性，由于需要辅以化学与放射治疗，可能导致不孕。“若能简单而稳定的确定保存卵母细胞的方法，患者就能先取出卵保存，可以无后顾之忧的治疗。”再生医学与内分泌专家Adelina  M.  Emmi医师表示。“毕竟自己活命与繁衍后代其实同等重要。”

    先前的冷冻保存法是在抗冻处理之后，存放于4度环境后转放在-80度环境下，再转存于-196度的液态氮中。“像精子、血液与胚胎这类组织可以使用渐冻法，使细胞内的水分逐步脱除；”Emmi医师指出：“但人类卵子与卵巢组织不能；有任何冰晶形成的可能，就会伤害到组织。”

    研究者收集由16到37岁女性中，因非癌症卵巢疾病患者的卵巢组织与三个卵子，分别尝试各种修饰过后的超低温冷冻保存法（cryopreservation）。由于超低温冷冻保存法所需的抗冻剂具有毒性，使得在剂量上一直难以掌握；研究者应用了新式的玻璃化技术（Vitrification），掌握了新的配方，能够在短暂回温后不会产生冰晶。 

    “不仅卵子，卵巢组织等也能用同样的方法保存，”低温生物学家Ying  C.  Song博士说。进一步的动物实验显示，回温后的组织能够在老鼠身上再次生长。“我们的长期目标是发展出器官银行保存模式，”Song博士指出，这具有广阔的临床医学应用价值。

英文原文：

Scientists look at slow-freezing techniques for human tissue

Medical Science News

Published: Tuesday, 12-Jun-2007

The goal is to make human eggs, ovarian tissue, blood vessels, even whole organs available when needed.

To get there, researchers are directly comparing slow-freezing techniques, used successfully for decades to preserve sperm and embryos, to a more rapid method of cryopreservation that transforms tissues into durable glass-like structures.

Phase I trials under way at the Medical College of Georgia are comparing the two approaches in human ovarian tissue and eggs, or oocytes, as well as human-like cow ovarian tissue and eggs.

They start with reproductive tissues because young women with cancer produce a compelling need and are a good model for other tissues and organs.

"What we tell patients is that right now the standard of care for people who are going through cancer therapy is to use egg donors later on," says Dr. Adelina M. Emmi, reproductive endocrinologist and medical director of MCG Reproductive Laboratories of Augusta.

Treatment for leukemia and cervical, ovarian, breast or other cancers often leaves women infertile because systemic chemotherapy and more focused radiation therapy, designed to kill rapidly spreading cancer cells, also can destroy dynamic reproductive tissue.

"I don't think when you are faced with the reality that you may die, your fertility is the most important thing you are thinking or talking about, but there are a lot of women interested in talking about it," says Dr. Emmi. She hopes her work with Dr. Ying C. Song, cryobiologist, will one day give her more to say.

They are collecting ovarian tissue from volunteers age 16 to 37 who need the tissue taken for some reason other than cancer, such as a hysterectomy for benign disease, says Dr. Song, MCG clinical associate professor at MCG and director of research for Augusta-based Xytex Research/Xytex International. Collaborators at the University of Texas Health Science Center and M.D. Anderson Cancer Center are doing the same.

 Three human eggs, donated to research because they were inadequate for fertilization, that have been vitrified then warmed.

With some of the tissue, they are using conventional cryopreservation. Chemicals to protect cells from the hazards of freezing are added before taking tissue from the refrigerator temperature of 4 degrees Celsius to minus 80 degrees Celsius over two- and one-half hours. Later, liquid nitrogen takes it to minus 196 degrees

"You put it in a control-rate freezer that takes down the temperature one degree centigrade per minute so it drops the temperature very, very slowly," says Dr. Song.

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