Japanese, American and British scientists have carried out a feasibility study on growing transplant organs in a host animal with a view to interspecies grafts (xenografts) between rats and mice. This approach is “far from being at the experimental stage in man” and “will inevitably raise technical difficulties and ethical questions”, but it is under consideration to offset the organ shortage .
In their article published in the Nature journal, scientists explain the process. They have grown a pancreas from murine pluripotent stem cells in rats. Once grafted to type 1 diabetic mice, this pancreas functioned normally. The pluripotent stem cells were injected at an early stage of embryo development in the rat. These embryos did not contain the gene needed to develop a pancreas. Thus, “the rats developed carrying cells from two cell lines – rats and mice – except for the pancreas which developed spontaneously from the murine line. However, the vessels supplying the pancreas were from the rat”. The transplant concerned part of the pancreas – the mass of insulin-producing cells (Islets of Langerhans). The mice received short-term immunosuppressant treatment (five days) to prevent graft rejection. The graft was successful, “probably because vascular elements obtained from rats were rapidly eliminated”.
Can this approach be transposed to other animals and human beings with a host animal? For Sylvaine You, Inserm scientist, “it is far too early to say”. In this case, “the model selected involves two types of rodents”, and in these animals“only one gene determines the growth of the pancreas”. Furthermore, in humans, pluripotent stem cells derived from the adult cells of the recipient would have to be used, which poses “problems of a material and financial nature”.
 In the case of diabetes, pancreatic transplants are carried out in patients for whom treatment has proven ineffective. Three million people have undergone this kind of treatment in France. In 2015, the pancreas represented only 78 of the 5,746 organs that were transplanted.
Le Monde, Paul Benkimoun (25/01/2017)