How a line of embryonic cells is created
Embryonic stem cells are made from the discarded frozen embryos of in vitro infertility procedures.
The couples responsible for these embryos either have succeeded at having as many kids as they want or they no longer can bear the $10,000 expense to have embryos implanted.
Thousands of unwanted frozen embryos are discarded as medical waste every year.
In vitro means “in glass,” referring to the dishes in which eggs were once fertilized. These days, they’re usually plastic.
In the in vitro procedure, a physician collects human eggs by stimulating a woman’s ovaries with hormones and then using a needle to suck the eggs out of budding ova. Not every egg will succeed in becoming an embryo, so the doctor takes many eggs.
For instance, 10 to 20 may be collected. Of those, seven may develop normally. Three will be implanted in the woman, creating a one in three chance of a baby. The other four viable embryos are frozen for future attempts.
Let’s say two of the embryos become children and the couple wants to stop. The frozen embryos can be given to other infertile couples — producing rare “snowflake babies” — or destroyed. About 11,000 frozen embryos were destined to become medical waste in 2003.
Most countries that permit the creation of stem cell lines from embryos have adopted the following guidelines:
n The embryos must be left over with no further purpose of reproduction.
n They must come from couples giving informed consent.
n No monetary reward must be provided.
n The embryos would otherwise be destroyed.
Frozen embryos are stored in small plastic vials, three or four of them together. Each embryo is a tiny ball of 30 to 50 visually indistinguishable cells.
Each is typically frozen at a stage equal to five days of normal development.
To create stem cells, the vials are thawed. Next, the embryos are watched to see which begin developing normally again. Not all will. Those that do can be placed in a dish coated with a special medium — stem cell food. Occasionally, as the stem cells reproduce, some are transported to other dishes.
The trick is to feed them only what they need in order to reproduce but to deprive them of the milieu of signals that will cause them to evolve into other types of cells.
“Stem cells are covered with receptors,” said David Crouse, associate vice chancellor at the University of Nebraska Medical Center in Omaha. “They’re looking for signals. As long as you don’t feed that signal, they just replicate.”
Cell lines can be maintained indefinitely but they can only be allowed to progress up to what would be about their 10th to 14th day of development in the womb. After that, cell evolution progresses to the point they need the environment of a mother to survive.
Not every line of embryonic stem cells will be equally useful for research. Some lines are far more easily influenced than others to turn into certain types of cells. Some lines don’t seem to want to become much of anything.
The reason may be that even in the days-old embryo of 30 to 50 cells, irrevocable steps already have occurred. Some cells, for example, may be on their way to becoming placenta and not baby.
Reach Mark Andersen at 473-7238 or mandersen@journalstar.com.
The couples responsible for these embryos either have succeeded at having as many kids as they want or they no longer can bear the $10,000 expense to have embryos implanted.
Thousands of unwanted frozen embryos are discarded as medical waste every year.
In vitro means “in glass,” referring to the dishes in which eggs were once fertilized. These days, they’re usually plastic.
In the in vitro procedure, a physician collects human eggs by stimulating a woman’s ovaries with hormones and then using a needle to suck the eggs out of budding ova. Not every egg will succeed in becoming an embryo, so the doctor takes many eggs.
For instance, 10 to 20 may be collected. Of those, seven may develop normally. Three will be implanted in the woman, creating a one in three chance of a baby. The other four viable embryos are frozen for future attempts.
Let’s say two of the embryos become children and the couple wants to stop. The frozen embryos can be given to other infertile couples — producing rare “snowflake babies” — or destroyed. About 11,000 frozen embryos were destined to become medical waste in 2003.
Most countries that permit the creation of stem cell lines from embryos have adopted the following guidelines:
n The embryos must be left over with no further purpose of reproduction.
n They must come from couples giving informed consent.
n No monetary reward must be provided.
n The embryos would otherwise be destroyed.
Frozen embryos are stored in small plastic vials, three or four of them together. Each embryo is a tiny ball of 30 to 50 visually indistinguishable cells.
Each is typically frozen at a stage equal to five days of normal development.
To create stem cells, the vials are thawed. Next, the embryos are watched to see which begin developing normally again. Not all will. Those that do can be placed in a dish coated with a special medium — stem cell food. Occasionally, as the stem cells reproduce, some are transported to other dishes.
The trick is to feed them only what they need in order to reproduce but to deprive them of the milieu of signals that will cause them to evolve into other types of cells.
“Stem cells are covered with receptors,” said David Crouse, associate vice chancellor at the University of Nebraska Medical Center in Omaha. “They’re looking for signals. As long as you don’t feed that signal, they just replicate.”
Cell lines can be maintained indefinitely but they can only be allowed to progress up to what would be about their 10th to 14th day of development in the womb. After that, cell evolution progresses to the point they need the environment of a mother to survive.
Not every line of embryonic stem cells will be equally useful for research. Some lines are far more easily influenced than others to turn into certain types of cells. Some lines don’t seem to want to become much of anything.
The reason may be that even in the days-old embryo of 30 to 50 cells, irrevocable steps already have occurred. Some cells, for example, may be on their way to becoming placenta and not baby.
Reach Mark Andersen at 473-7238 or mandersen@journalstar.com.
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