Posted on 11/07/2004 7:43:24 AM PST by TomDoniphon68
A male achievement that is perhaps insufficiently celebrated is that with every heartbeat a man generates 1,000 sperm, each of which has taken two months to produce. In a step that brings closer the possibility of making inheritable genetic changes in humans, scientists have succeeded in growing outside the body the special stem cells that direct the remarkably prolific process of sperm production.
Although the method now works just for mice, it may well apply to human cells, since they use the same genetic signals as mouse cells.
Cultivation of the sperm production cells has been a 10-year goal of Dr. Ralph L. Brinster, a reproductive biologist at the University of Pennsylvania School of Veterinary Medicine. The ability to culture the cells is a first step that leads in a number of possible directions. One is correcting the sperm of infertile men. Another, if ethically acceptable, would be genetic engineering in humans. A third is generating embryonic stem cells without the controversial step of making an embryo.
The new method was developed by Dr. Brinster and his colleagues Hiroshi Kubota and Mary R. Avarbock and is reported in the current issue of Proceedings of the National Academy of Sciences.
The ability to cultivate the sperm production cells in large numbers would make it possible to try swapping mutated genes in the cells for normal or improved versions. With infertile men, the sperm production cells could be removed, genetically treated, and put back in the testis, where they should produce normal sperm.
Dr. Brinster said he hoped to learn how to make the sperm production cells produce sperm outside the body. Genetically altered sperm could then be used directly for in vitro fertilization. The technique could be useful in animal breeding; whether it would be considered ethical in human reproduction is likely to be a matter of debate.
The technique may also provide an alternative route for generating embryonic stem cells for use in repairing the body's tissues. The sperm production cells are adult stem cells, which are specialized, self-renewing cells, each type of which is dedicated to repairing or maintaining a specific body tissue. All are descended from embryonic stem cells, the all-purpose cells from which the body is made.
At present, embryonic stem cells are taken from the surplus embryos generated in fertility clinics. The sperm production cells have many of the same characteristics of embryonic stem cells and, Dr. Brinster believes, are only a couple of developmental steps away from them. It may be possible to walk them backward into being embryonic stem cells. These could then be converted into the specialized cell types needed to repair damaged organs.
The new technique "will fuel a major advance in genetic modification for farm animals, endangered species and primates, including humans," Martin M. Matzuk, a reproductive biologist at the Baylor College of Medicine, said in a written commentary.
John Gearhart, a stem cell biologist at Johns Hopkins University, said Dr. Brinster's achievement lay in showing how to grow sperm production cells in a reproducible way.
Isn't science just awesome?
I'd like to start a list of FORBIDDEN sperm donors---
Michael Moore (does he have any?)
sKerry
Its not "science" unless we destroy human life to aid human life. Get with the program.
ROFL
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