Researchers from the University of Pennsylvania College of Veterinary Medicine have overcome a technical hurdle and successfully cultivated mouse spermatogenous stem cells in the laboratory. The researchers transplanted this kind of cells into infertile mice, and as a result these recipient mice became able to produce sperm and eventually produce offspring with the genetic characteristics of the donated mouse. Articles on this study were published in the online edition of Proceedings of the Natioanl Academy of Sciences. The research team successfully modified the culture medium, which contains all the cell growth factors required for the expansion of cells in vitro. Although sperm-derived stem cells cannot fertilize with egg cells, they produce cells that can develop into sperm. In 1994, the research team developed a method for transplantation of spermatogonia stem cells between mice, and recipient mice were able to produce sperm with the genetic characteristics of donated mice. Now that researchers are able to artificially cultivate primordial stem cells, they have sufficient resources for genetic manipulation. For the study, Dr. Kubota and colleagues started with genetically altered mice that express green fluorescent protein (GFP). GFP emits green light at a certain wavelength of light. At an important stage of the experiment, tissues from donated mice were able to emit green light. According to the green light emitted by sperm-derived stem cells, the researchers were able to identify spermatogenous stem cells. Moreover, when these cells are grown and expanded in the recipient mice, spermatogenetic stem cells can also emit green light. Using this technology, researchers are able to develop spermatogenic stem cells with a new gene that can be transplanted to recipient animals, and animals can therefore pass new features to their offspring. This technology may also promote the treatment of patients with male infertility and will encourage researchers to gain insight into the potential of spermatogenetic stem cells. U.S. researchers announced on the 4th that they succeeded in culturing spermatogonial stem cells that can differentiate into spermatozoa into spermatozoa and using the sperm to breed young rats. The study was completed by researchers from the University of Pennsylvania School of Veterinary Medicine at the University of Pennsylvania. The researchers reported in the newly published "Journal of the National Academy of Sciences" that for adult animals, spermatogonial stem cells are the only stem cells that can transmit their genetic information to the next generation. Previously, the main method for scientists to cultivate transgenic animals was to implant the designed genes in early animal embryos. However, by using spermatogonial stem cells to grow spermatozoa in the laboratory, genetically modifying the spermatozoa, and fertilizing egg cells with these spermatozoa, it will be easier to breed animals that carry the set genes. Scientists commented that the results of the researchers at the University of Pennsylvania are expected to open new avenues for breeding genetically modified animals, treating male infertility and enhancing the viability of endangered species. (On May 30, 1996, American scientists recently used mice to successfully secrete rat sperm. This new cross-species sperm secretion method can be used for the treatment of male infertility and the rescue of rare animals. The British "Nature" published today. The magazine published the results of a team of researchers at the University of Pennsylvania who removed stem cells from spermatogonia in the testis of rats and made these stem cells multiply in test tubes, then transplanted them into 10 mice and lost their immunity. In mouse testis, the mice produced rat spermatozoa after a period of time, and the purpose of immunizing mice was to avoid the mice's rejection of implanted rat tissues. In order to find out what kind of spermatogonia cells play a key role in sperm development, the research team genetically modified the experimental rats and added different markers to various spermatogonia. The rat spermatozoa secreted by the mouse were found to be derived from rat spermatogonial stem cells. Today's British "Natural Medicine" magazine published the research. Another related result of the group is that they found that the spermatogonial stem cells can be stored for a long period of time in the frozen state.These two results have broad application prospects in the fields of medicine, species protection and animal husbandry.Firstly, they can be used to treat male infertility. The method is to take the patient's spermatogonial stem cells into a mouse or a healthy near-parent male implanted with the immune system to secrete the patient's own sperm and then perform artificial insemination to give birth to the offspring. Primordial stem cells can develop spermatozoa containing multiple combinations of genes, which, like the normal human sperm excretion process, can avoid the defects of the sperm genes that have been preserved by cryopreservation. Since spermatogonial stem cells can be cryopreserved for a long time, spermatozoa are secreted by this method. Due to this method, it is possible to preserve the spermatogonial stem cells of rare animals and to breed these rare animals as needed, and it is also possible to use this method to cultivate and breed a large number of excellent breeds of livestock.
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