A group of Spanish researchers from four different institutions returned to the idea of xenotransplantation, a promising method in the 90s, but now improved with the latest techniques of regenerative medicine and stem cells. The concept is using genetically modified animals to grow human organs, as a hope to end waiting lists for transplants.
The team of scientists, led by Juan Carlos Izpisua, researcher at the Salk Institute in La Jolla (California), have combined such strategies to produce tailored human organs from the patient’s own cells. Instead of growing them in the laboratory, the researchers introduce the cells into an animal embryo, so the organ grows as its own. Somehow, the pig becomes a kind of incubator for the human organ.
Izpisua team has not yet materialize this idea, but has taken the first step to do it in the near future. In the journal Nature, he published their findings regarding a new variety of pluripotent cell (which can give rise to any type of tissue) capable of integrating into an animal embryo. This newly discovered type of stem cell could help provide a model for early human development — and, eventually, allow human organs to be grown in large animals such as pigs for research or therapeutic purposes. With this step, an obstacle in the developing of replacement human organs is overcome.
The new stem cells were called region-selective pluripotent stem cells (rsPSCs). To originate them it is needed adult cells obtained by a skin sample, and then, they are reprogramed to return to a primitive stage. Unlike iPSCs, a type of pluripotent stem cell that can be generated directly from adult cells developed by Nobel Prize winner Shinya Yamanaka, rsPSCs can grow in other species.
For now, the Salk Institute, in collaboration with the Clinic of Barcelona, the Madrid CEMTRO Clinic and the Catholic University of Murcia, have managed to create a human-mouse chimera, a combination of cells from both species. And with it they have shown that their hypothesis is not science fiction. The next step is to verify if it I possible to generate simple human tissue in mice, and then try it in pigs, the best candidates to host human organs.
Izpisua strategy is not the first to use pluripotent stem cells to generate human organs, but the only using other species to develop and incubate them. Why go back to xenotransplantation? “Because try it in a culture dish in a laboratory is doing it in an artificial and totally alien environment. We believe it is more suitable for a future transplantation that the cells are incorporated into developing embryos, so they develop naturally and form organs and tissues from human cells inserted,” Izpisua explained.
The scientist goes further and says that in the future, from a patient’s skin sample it may be possible to obtain rsPSC cells, if necessary, modify their genome to remove the disease, and then incorporate them in an animal embryo.
Co-author Josep Maria Campistol, medical director of the Hospital Clinic of Barcelona, anticipates that the first organ that they will attempt to develop is a pancreas. “Not only because it would be a promise for thousands of diabetics, but because it is one of the simplest organs to start with“. In fact, in the laboratory at Salk Institute, they have already generated a rat’s pancreas in a mouse.
Source: Agencia ID
