Fusion and regenerative therapies: is immortality really recessive?

Harnessing cellular fusion as a potential tool for regenerative therapy has been under tentative investigation for decades. A look back the history of fusion experiments in gerontology reveals that whereas some studies indicate that aging-related changes are conserved in fused cells, others have demonstrated that fusion can be used as a tool to revoke cellular senescence and induce tissue regeneration. Recent findings about the role of fusion processes in tissue homeostasis, replenishment, and repair link insights from fusion studies of previous decades with modern developments in stem cell biology and regenerative medicine. We suggest that age-associated loss of regenerative capacity is associated with a decline of effectiveness in stem cell fusion. We project how studies into the fusion of stem cells with tissue cells, or the fusion between activator stem cells and patient cells might help in the development of applications that "rejuvenate" certain target cells, thereby strategically reinstating a regeneration cascade. The outlook is concluded with a discussion of the next research milestones and the potential hazards of fusion therapies. © 2007 Mary Ann Liebert, Inc.