Telomere-encoding nucleic acid nanocircles, methods for their preparation, and methods for their use are disclosed. The nanocircles can be constructed containing multiple repeats of the complement of telomere repeat sequences. The telomere-encoding nanocircles are useful for extending telomeres both in vitro and in vivo, for treating macular degeneration, the effects of skin aging, liver degeneration, and cancer. The nanocircles are further useful for treating cell cultures to produce long-lived non-cancerous cell populations. This use has wide applicability in scientific research, tissue engineering, and transplantation.