Cellular and Tissue Rejuvenation through Transcriptional Reprogramming

Summary Organismal and cell rejuvenation are exciting new approaches to counteract aging, and recent breakthroughs have brought them to the forefront of aging research. For examples, systemic factors in young blood was found to rejuvenate various mouse tissues and brain function, and partial reprogramming with four stem cell transcription factors (TFs) (Yamanaka factors) rejuvenate tissues and cells and extend the lifespan of mice. These discoveries demonstrate that “young” and “old” can be described as different states, and the “old” state can be reversed back into a “young” state through transcriptional reprogramming. We hypothesized that there might exist many solutions to human cell rejuvenation through transcriptional reprogramming, and some of the solutions may be safer and more potent than Yamanaka factors. In a recently completed project supported by an NIH/NIA R21 grant, the Li lab developed a systematic approach to test this hypothesis and to find the solutions. Using a human cell culture model of replicative aging employed by Hayflick (continuously passaged human fibroblast cells), we developed a high throughput screen using Perturb-seq to identify the potential rejuvenating TFs -- those that when over-expressed or repressed in old cells, are capable of reprogramming the global gene expression program from the old state back to a younger state. We identified four TFs/chromatin modifier (E2F3, EZH2, STAT3, ZFX) that when over-expressed or repressed individually, are able to rejuvenate human fibroblast cells aged in vitro. Here we propose to further test the rejuvenating effect of these four factors in human fibroblast cells aged in vivo in their natural tissue environment, and in mouse liver. We will also develop new technologies to screen for more potent rejuvenating TF combinations and test them in aged human fibroblast cells and in mouse liver. If successful, this proposed study will identify TFs/TF combinations that can rejuvenate in vitro and in vivo aged human fibroblast cells and mouse liver. This will set the stage for transgenic mouse study and translation to human therapies. The methodologies developed in this proposal can be generalized to identify combinatorial transcriptional programs that produce any desired cellular phenotypes, e.g., the reversion of the cellular state from disease to normal in cell culture models of diseases.