this invention generally relates to methods to obtain mammalian cells and tissues with patterns of gene expression similar to that of a developing mammalian embryo or fetus , and the use of such cells and tissues in the treatment of human disease and age - related conditions . more particularly , the invention relates to methods for identifying , expanding in culture , and formulating mammalian pluripotent stem cells and differentiated cells that differ from cells in the adult human in their pattern of gene expression , and therefore offer unique characteristics that provide novel therapeutic strategies in the treatment of degenerative disease .