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A transplant in time
January 02, 2007Scientists ID time window for effective porcine embryonic tissue transplant
In hemophilia, a mutated gene prevents the production of a critical blood-clotting protein. Treatments for hemophilia and other such genetic diseases, when they exist, may consist of risky blood transfusions or expensive enzyme replacement therapy. But what if the body could be induced to begin producing these proteins, say by transplanting healthy tissue with the abilities that are lacking?
Prof. Yair Reisner and Ph.D. student Anna Aronovich of the Weizmann Institute's Immunology Department, together with colleagues, showed, in research recently published in the Proceedings of the National Academy of Sciences (PNAS), how such a transplant might, in the future, be made feasible.
Previous attempts to treat genetic disease by transplanting (mother to daughter) a spleen, an organ that can manufacture a number of the missing proteins in some such diseases, had made little headway due to the fact that the spleen is home to the immune system's T cells - cells responsible for the severe immune responses against the recipient known as graft-versus-host disease (GVHD).
Reisner and his team revived the idea, with a twist. Over the past several years, he and members of his lab have been experimenting with tissue transplanted from pig embryos - a possible substitute for human donor organs. From this, they have learned that for each type of tissue, there is a window of opportunity during which cells taken from the developing embryo can be most successfully transplanted. Tissues taken too early, when they are still fairly undifferentiated, may form tumors, while those taken too late can be identified as foreign, causing the host to reject them.
By taking spleen tissue from embryonic pigs over the course of gestation, they found that the harmful T cells are not present in the tissue prior to day 42 of gestation. The scientists also found that tissue of this age exhibits optimal growth potential as well as secreting factor VIII, the blood-clotting protein missing in hemophilic patients. Thus, the scientists fixed the ideal time for spleen transplantation at 42 days. Hemophiliac mice with spleen tissue transplanted from pig embryos at this time experienced completely normal blood clotting within a month or two of implantation.
Although a number of problems would need to be surmounted before researchers could begin to think of applying the technique to humans, the Institute team's experiment is "proof of principle" - evidence that transplanted embryonic tissue, whether human or pig, could one day help the body to overcome genetic diseases.
American Committee for the Weizmann Institute of Science
Previous attempts to treat genetic disease by transplanting (mother to daughter) a spleen, an organ that can manufacture a number of the missing proteins in some such diseases, had made little headway due to the fact that the spleen is home to the immune system's T cells - cells responsible for the severe immune responses against the recipient known as graft-versus-host disease (GVHD).
Reisner and his team revived the idea, with a twist. Over the past several years, he and members of his lab have been experimenting with tissue transplanted from pig embryos - a possible substitute for human donor organs. From this, they have learned that for each type of tissue, there is a window of opportunity during which cells taken from the developing embryo can be most successfully transplanted. Tissues taken too early, when they are still fairly undifferentiated, may form tumors, while those taken too late can be identified as foreign, causing the host to reject them.
By taking spleen tissue from embryonic pigs over the course of gestation, they found that the harmful T cells are not present in the tissue prior to day 42 of gestation. The scientists also found that tissue of this age exhibits optimal growth potential as well as secreting factor VIII, the blood-clotting protein missing in hemophilic patients. Thus, the scientists fixed the ideal time for spleen transplantation at 42 days. Hemophiliac mice with spleen tissue transplanted from pig embryos at this time experienced completely normal blood clotting within a month or two of implantation.
Although a number of problems would need to be surmounted before researchers could begin to think of applying the technique to humans, the Institute team's experiment is "proof of principle" - evidence that transplanted embryonic tissue, whether human or pig, could one day help the body to overcome genetic diseases.
American Committee for the Weizmann Institute of Science
Hemophilia Current Events and Hemophilia News RSSResearch highlights need to address hemophilia in developing world
When modern medicine finds a way to treat a medical condition, people often think that the problem is solved. But we also have to find ways to get that treatment into the hands of those who need it.
Governor recognizes stem cell research at Einstein
Albert Einstein College of Medicine of Yeshiva University hosted a roundtable discussion on stem cell research with New York Governor David A. Paterson today.
Jumping genes discovery 'challenges current assumptions'
Jumping genes do most of their jumping, not during the development of sperm and egg cells, but during the development of the embryo itself.
Gene therapy technique thwarts cancer by cutting off tumor blood supply
University of Florida researchers have come up with a new gene therapy method to disrupt cancer growth by using a synthetic protein to induce blood clotting that cuts off a tumor's blood and nutrient supply.
Gene therapy demonstrates benefit in patients with rheumatoid arthritis
Researchers have reported the first clinical evidence that gene therapy reduces symptoms in patients with rheumatoid arthritis, an important milestone for this promising treatment which has endured a sometimes turbulent past.
Redesigned protein accelerates blood clotting
Researchers have made several, subtle changes in the structure of a key protein, dramatically increasing its ability to drive blood clotting, according to a study published in a December edition of the Journal of Thrombosis and Haemostasis.
Mapping a clan of mobile selfish genes
Much of human DNA is the genetic equivalent of e-mail spam: short repeated sequences that have no obvious function other than making more of themselves.
Blood-clotting protein modified for people with hard-to-treat hemophilia
Pathologists at The University of Texas Health Science Center at Houston have developed a chemically modified protein that may help people with a hard-to-treat form of a genetic bleeding disorder known as Hemophilia A.
UF researchers develop improved gene therapy agent
Replacing one amino acid on the surface of a virus that shepherds corrective genes into cells could be the breakthrough scientists have needed to make gene therapy a more viable option for treating genetic diseases such as hemophilia, University of Florida researchers say.
Skin flaps deliver cancer-fighting therapy, ASPS study reveals
Using gene therapy, plastic surgeons have delivered cancer fighting proteins through skin flaps placed on cancerous tumors on rats with a 79 percent reduction in tumor volume.
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