Epigenetic reprogramming of nonreplicating somatic cells for long-term proliferation by temporary cell-cell contact

Embryonic stem (ES) cells are potential sources of tissue regeneration; however, transplanted ES cells produce tumors in the host tissues. In addition, transplantation between genetically unrelated individuals often results in graft rejection. Although the development of patient specific stem cell lines by somatic cell nuclear transfer (SCNT) represents a means of overcoming the problem of rejection, its human application has ethical dilemmas. Adult stem (AS) cells can also differentiate into specialized cells and may provide an alternative source of cells for human applications. In common with other somatic cells, AS cells have limited capacity for proliferation and cannot be produced in large quantities without genetic manipulation. We demonstrate here that nonreplicating mammalian cells can be reprogrammed for long-term proliferation by temporary cell-cell contact through coculture of AS cells with the GM05267-derived F7 mouse cell line. Subsequent elimination of F7 cells from the co-culture allows proliferation of previously nonreplicating cells, colonies of which can be isolated to produce cell lines. We also demonstrate that the epigenetically reprogrammed AS cells, without the physical transfer of either nuclear or cytoplasmic material from other cells, are capable of long-term proliferation and able to relay signals to other nonreplicating cells to reinitiate proliferation with no addition of recombinant factors. The reported cell amplification procedure is methodologically simple and can be easily reproduced. This procedure allows the production of an unlimited number of cells from a limited number of AS cells, making them an ideal source of cells for applications involving autologous cell transplantation.