A team of researchers in the Centre for the Biology of Stem Cells and Regenerative Medicine of the Institute of Medical Sciences of Tokyo University has published on the website Molecular Therapy the result of a study undertaken with mice and involving induced pluripotent stem cells (iPS). They discovered how to replace grafts of bone marrow, which carry many risks, by using these reprogrammed cells.
Bone marrow grafts are currently used for immune diseases, for example leukaemia. In this type of disease, it is the hematopoietic stem cells (HSC) present in the bone marrow and "at the origin of all the lines of blood cells" which are damaged and thus can no longer correctly replace the latter. Currently, one of the treatments used consists of "irradiating the bone marrow to destroy all the damaged cells" and to obtain a bone marrow donation "to re-establish all the renewal functions of the blood cells." The team from Tokyo University discovered a new therapeutic approach for replacing bone marrow. Using iPS cells, they managed to "generate HSC cells that can be transplanted successfully in animals carrying a teratoma [i.e. "a tumour consisting of germinal pluripotent cells"], in combination with a method that favours" the renewal of the HSC cells. Thus, "the HSC cells derived from the iPS cells migrate from the teratoma to the bone marrow" and the "successive intravenous injections in an irradiated host [i.e. a host in which all the damaged cells have been destroyed] led to the establishment of a multiple cell line and the long-term restoration of the hemato-lymphopoietic system."
Through this research work, the team "demonstrated that the immunity deficit […] linked to the X chromosome in mice can be treated thanks to HSC cells derived from genetically corrected clone iPS cells."
This new therapeutic approach to replacing bone marrow by using iPS cells rules out any rejection or reaction of the graft against the host.