Never give up

Never give up a team of scientists from the University of Pennsylvania in Philadelphia and the University of Texas Southwestern Medical Centre in Dallas have taken the first, albeit small steps towards making the impossible a reality. Yes, a man may be able to father a child even in his 100th year or perhaps even after his death. Two papers published simultaneously in Nature Medicine and Nature reported that M R Avarbook and his colleagues have successfully stored sperm-making stem cells for a long time and later transplanted them between species ( Nature Medicine , Vol 2, No 6; Nature , Vol 381, No 6581).

Stem cells are cells with a potential to renew themselves and give rise to one or more differentiated cell types. The scientists have frozen spermatogonial stem cells capable of differentiating into sperm-making cells, thawed them and literally coaxed them back into making viable sperm. The same team has created history by implanting these stem cells from rat into mice, which then produced rat sperm.

Stem cells find use in cases of acci dental or induced damage as they readily repopulate damaged tissues. While stem cells of the bone marrow, gut and skin have been the subject of many a study, spermatogonial stem cells had not received enough attention. But it is known that they are equally capable of self-renewal else most men would have very short fertile periods.

As Robin Lowell-Badge of the Medical Research Council's National Institute of Medical Research, London, commented on the Nature Medicine study, "Spermatogonial stem cells can be purified but attempts to cryopreserve (preserve under very low temperature) them have so far been unsuccessful.' Lowell-Badge calls these two path-breaking papers "marked advances' on the existing knowledge, holding a great potential for human health as well as other applications.

Freezing sperm for future use has been tried successfully. Both human and animal sperm are routinely stored. But good sperms are always in short supply. Besides, frozen sperms last only for a limited period. But a sperm factory supported by stem cells is at least theoretically not time-bound. As Ralph Brinster, one of the investigators said, stem cells unlike sperms "really embody the essence of the individual', and freezing them confers on them a sort of biological immortality. The results of this study would be quite comforting to those men who may for various reasons run the risk of losing their sperm-making potential. For example, those undergoing radiation therapy or chemotherapy for cancer run the risk of losing their stem cells which may render them permanently infertile. The preservation of stem cells before the therapy and reimplanting them later could possibly help such people avoid sterility.

As for the second experiment, if stem cells from a rat can produce rat sperm inside a mouse's testicles, it should be possible for other mammals to host the stem cells of any other mammal, thus giving biologists striving hard to preserve endangered species, a much-needed break. The genetic material of such animals can be safely preserved for implantation into other related species. At times, an infertile person's stem cells may need just a new environment to start producing sperm again. Therefore, at least theoretically, transplanted into another person or even an animal could make the cells productive.

But there still remain some unanswered questions. Although the rat sperms produced by the mice are morphologically normal, research is yet to ascertain whether or not they are capable of producing viable offspring. Moreover, the spermatogonia may accumulate certain mutations with each round of cell division. Still, the value of these experiments for their application in the genetic manipulation of animals for agricultural or biomedical purposes cannot be underestimated.

In addition to useful and natural options, experiments of this nature always open up bizarre and disturbing possibilities. For instance, there might be the possibility of producing designer children with stem cells from a particularly gifted individual, say from a brilliant scientist or an extremely talented cricketer. And what if a woman is impregnated with sperms, 100 years after the death of their donor. The ethical ramifications are bound to be quite a serious cause of concern.

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