July 21, 2009 Cancer treatment has come a long way, leading to a multitude of therapy options and improved survival rates. These successes, however, have created a challenge for young cancer patients since chemotherapy and radiation treatments that often save lives threaten fertility. Techniques available to safeguard fertility, such as freezing eggs for later embryo development, have poor odds of success, leaving patients with very limited options for the future.
But that is beginning to change as researchers improve current techniques, mature human eggs in the laboratory, and discover cellular mechanisms that could help preserve and even restore fertility. Researchers will report on these and other findings at the 42nd annual meeting of the Society for the Study of Reproduction (SSR), July 18 to 22, at the David L. Lawrence Convention Center in Pittsburgh.
Summaries of the findings are as follows:
Growing Egg Cells in the Lab
Researchers at Northwestern University are developing a method they hope will help preserve a woman's fertility after radiation and chemotherapy treatment. Led by Teresa K. Woodruff, Ph.D., the team has grown undeveloped human eggs to near maturity in laboratory cultures. During a 30-day experiment, they grew human follicles―tiny sacs that contain immature eggs―in the lab until the eggs they contained were nearly mature. According to Dr. Woodruff, this is the first step in developing a new fertility option for young cancer patients.
Making a More Viable Embryo
Cryopreservation, the process of freezing eggs for later fertilization, has played a major role in assisted reproductive technology for the past two decades. Unfortunately, however, eggs rarely survive the freezing and thawing processes required to develop a viable embryo. A mere half of eggs survive and of these, only 20 percent, once fertilized, result in the birth of a baby. According to David Albertini, Ph.D., University of Kansas Medical Center, clinicians may be waiting too long – three hours – after thawing eggs to initiate fertilization with the sperm, a process necessary to create an embryo. When his research team used confocal microscopy to observe what was happening at a chromosomal level, they found that the structures needed to make the embryo's chromosomes align and divide were in place after only an hour. This indicates a shorter thawing time frame could have greater potential for success.
Restoring Fertility From the Bottom Up
Researchers at Stanford University, led by Renee A. Reijo Pera, Ph.D., have identified several genes involved in the formation of germ cells that give rise to eggs and sperm. These genes, DAZ and DAZL, form the basis of human embryo and germ cell growth and may be a key to understanding human reproductive failure – one of the most common health problems in men and women and a common cause of birth defects. While continued progress in developing germ cells capable of making embryos renders fertility restoration feasible, it also raises significant ethical questions, says Dr. Reijo Pera.
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