A cell that is recently fertilised is termed totipotent, meaning that it has the unlimited capacity to develop into all postembryonic tissues. As the cell develops and divides repeatedly, this potential is briefly retained. Identical twins develop at the stage when the initial egg has divided into two cells, each of which forms a person.
Normally, however, the divisions occur repeatedly within the single embryo, and as they increase in number, some of the developmental potential of the cells is lost. Once the developing embryo has formed a hollow ball of cells, a cluster of them inside are termed pluripotent. These pluripotent cells can not form a placenta and its supporting tissues, so they can not develop into a complete organism, but they can form virtually all the tissues of the human body.
Several private companies own patents protecting different aspects of stem cell therapy. Geron, a biotechnology company based in California, owns substantial Intellectual Property relating to the identification and use of human pluripotent cells, and methods for the isolation and regeneration of human embryonic stem cells.
It is likely that other complementary technologies will also be required to develop stem cell-based therapies. BresaGen has exclusive rights to a patent application which claims an intermediate cell type (EPL cell) that shares most of the characteristics of embryonic stem cells, but can be more easily coaxed to form specific cell types. The therapeutic uses of this cell type and its derivatives are also claimed in the application. The patent application was filed by Adelaide University and was acquired by BresaGen in 1999.