Abstract: Synthetic, persistent RNA vectors for controlled expression of one or more heterologous polynucleotide sequences, each of the one or more heterologous polynucleotide sequences encoding for a reprogramming factor, are described. The vectors comprise a mechanism for silencing (off) and initiation or resumption (on) control of expression of the one or more reprogramming factors in the cell, tissue, or organ. Methods of using the vectors are also described, for example, to treat the age-related disease or condition, where the methods provide for treatment of the disease or condition, and in some embodiments, with retention of cellular identity.

Abstract: Methods for treating a cell, tissue, or organ and for treating an age-related disease or condition are provided, where the cell, tissue or organ is contacted with a synthetic, persistent RNA vector comprising one or more heterologous polynucleotide sequences, each of the one or more heterologous polynucleotide sequences encoding for a reprogramming factor. Contacting achieves expression of the one or more reprogramming factors in the cell, tissue, or organ to treat the age-related disease or condition. In an embodiment, the method is used to obtain a rejuvenated cell, tissue, or organ with retention of cellular identity.

Abstract: The subject matter described herein relates to compositions and methods for cellular rejuvenation, tissue engineering, and regenerative medicine by transient exposure of cells or tissues to synthetic, non-integrative mRNAs encoding reprogramming factors. Reprogramming factor encoding polynucleotides and corresponding polypeptides that trigger less immune response, are more stable, and/or exhibit altered activity than wild-type reprogramming factors are provided. RNA vectors expressing one or more of the improved reprogramming factor polynucleotide sequences are also provided.