To date, the efficacy of replacement therapy by means of autologous stem cells is hindered by at least 3 factors: (i) the lack of sufficient number of autologous stem cells; (ii) the existence of stem cells with aged-phenotype of reduced repair capacity; (iii) the reduced potential of replacement therapy to repair non- or slow-turnover tissues. Lately, groundbreaking research has shown that somatic cells may be reprogrammed to a pluripotent state by the induction of a specific set of genes in vitro – creating induced pluripotent stem cells (iPS). Moreover, there is evidence that the increased expression of specific genes is able to reverse/rejuvenate the aged-phenotype of stem cells. Remarkably, these two methods operate at the epigenetic level as well. Considering the reversibility of cell potency and aged-phenotype, the next logical step toward the goal of organismal rejuvenation is to test the possibility of inducing the pluripotent state in somatic cells in vivo. Such an approach will not only provide enough autologous stem cells to replace old cells as in standard replacement therapy, but may also have the additional beneficial effects of (i) reversing the possible aged-phenotype of iPS and (ii) rejuvenating non- or slow-turnover tissues that otherwise would benefit less from standard replacement therapy.
induced pluripotent stem cells
rejuvenation in vivo