Multi-omic rejuvenation of naturally aged tissues by a single cycle of transient reprogramming

Aging; Epigenetic clocks; PluripotencyEnvelliment; Rellotges epigenètics; PluripotènciaEnvejecimiento; Relojes epigenéticos; PluripotenciaThe expression of the pluripotency factors OCT4, SOX2, KLF4, and MYC (OSKM) can convert somatic differentiated cells into pluripotent stem cells in a process known as reprogramming. Notably, partial and reversible reprogramming does not change cell identity but can reverse markers of aging in cells, improve the capacity of aged mice to repair tissue injuries, and extend longevity in progeroid mice. However, little is known about the mechanisms involved. Here, we have studied changes in the DNA methylome, transcriptome, and metabolome in naturally aged mice subject to a single period of transient OSKM expression. We found that this is sufficient to reverse DNA methylation changes that occur upon aging in the pancreas, liver, spleen, and blood. Similarly, we observed reversion of transcriptional changes, especially regarding biological processes known to change during aging. Finally, some serum metabolites and biomarkers altered with aging were also restored to young levels upon transient reprogramming. These observations indicate that a single period of OSKM expression can drive epigenetic, transcriptomic, and metabolomic changes toward a younger configuration in multiple tissues and in the serum

Promoting multi-omic rejuvenation in human and mouse somatic cells by transient reprogramming

Ageing can be defined as the gradual decline in fitness that occurs in most organisms. The ageing process is characterised by a variety of hallmarks at the cellular and molecular levels including alterations in the epigenome. Notably in the case of the epigenome, these alterations can be measured and quantified by epigenetic clocks. These are models that can predict age based on the DNA methylation levels at particular CpG sites and, interestingly, also appear to capture biological age (where relatively fit individuals are predicted to be younger than their chronological age and vice versa). iPSC reprogramming is the process of converting somatic cells, such as fibroblasts, into induced pluripotent stem cells (iPSCs). Amazingly, this process reverses age associated alterations in the epigenome and resets epigenetic clocks to 0 years old. Complete iPSC reprogramming has the major caveat of losing original cell identity and therefore function. This can be difficult to reacquire as differentiation protocols do not exist for all cell types or existing protocols may be inefficient or generate immature cell types rather than mature adult cells. To avoid this problem, we have developed a new method called maturation phase transient reprogramming, where human cells are reprogrammed up to the maturation phase and then the reprogramming factors are withdrawn. This method enabled cells to reacquire their original cell identity and substantially reversed age-associated changes in the transcriptome, proteome and epigenome, with features such as the transcriptome and epigenome appearing to become 30 years younger. In addition, transiently reprogrammed fibroblasts produced more collagen protein suggesting these cells are functionally younger. Finally, we have also carried out transient reprogramming in vivo, where this approach also promotes rejuvenation in the epigenome. Overall, transient reprogramming appears to capable of eliciting cellular and molecular rejuvenation, which may enable us to better understand the ageing process and develop novel anti-ageing therapies in the future

Transcriptome and epigenome diversity and plasticity of muscle stem cells following transplantation.

Adult skeletal muscles are maintained during homeostasis and regenerated upon injury by muscle stem cells (MuSCs). A heterogeneity in self-renewal, differentiation and regeneration properties has been reported for MuSCs based on their anatomical location. Although MuSCs derived from extraocular muscles (EOM) have a higher regenerative capacity than those derived from limb muscles, the molecular determinants that govern these differences remain undefined. Here we show that EOM and limb MuSCs have distinct DNA methylation signatures associated with enhancers of location-specific genes, and that the EOM transcriptome is reprogrammed following transplantation into a limb muscle environment. Notably, EOM MuSCs expressed host-site specific positional Hox codes after engraftment and self-renewal within the host muscle. However, about 10% of EOM-specific genes showed engraftment-resistant expression, pointing to cell-intrinsic molecular determinants of the higher engraftment potential of EOM MuSCs. Our results underscore the molecular diversity of distinct MuSC populations and molecularly define their plasticity in response to microenvironmental cues. These findings provide insights into strategies designed to improve the functional capacity of MuSCs in the context of regenerative medicine

Multi-omic rejuvenation of human cells by maturation phase transient reprogramming.

Funder: Biotechnology and Biological Sciences Research Council; FundRef: http://dx.doi.org/10.13039/501100000268Funder: Milky Way Research FoundationAgeing is the gradual decline in organismal fitness that occurs over time leading to tissue dysfunction and disease. At the cellular level, ageing is associated with reduced function, altered gene expression and a perturbed epigenome. Recent work has demonstrated that the epigenome is already rejuvenated by the maturation phase of somatic cell reprogramming, which suggests full reprogramming is not required to reverse ageing of somatic cells. Here we have developed the first "maturation phase transient reprogramming" (MPTR) method, where reprogramming factors are selectively expressed until this rejuvenation point then withdrawn. Applying MPTR to dermal fibroblasts from middle-aged donors, we found that cells temporarily lose and then reacquire their fibroblast identity, possibly as a result of epigenetic memory at enhancers and/or persistent expression of some fibroblast genes. Excitingly, our method substantially rejuvenated multiple cellular attributes including the transcriptome, which was rejuvenated by around 30 years as measured by a novel transcriptome clock. The epigenome was rejuvenated to a similar extent, including H3K9me3 levels and the DNA methylation ageing clock. The magnitude of rejuvenation instigated by MPTR appears substantially greater than that achieved in previous transient reprogramming protocols. In addition, MPTR fibroblasts produced youthful levels of collagen proteins, and showed partial functional rejuvenation of their migration speed. Finally, our work suggests that optimal time windows exist for rejuvenating the transcriptome and the epigenome. Overall, we demonstrate that it is possible to separate rejuvenation from complete pluripotency reprogramming, which should facilitate the discovery of novel anti-ageing genes and therapies

Multi-omic rejuvenation of naturally aged tissues by a single cycle of transient reprogramming.

The expression of the pluripotency factors OCT4, SOX2, KLF4, and MYC (OSKM) can convert somatic differentiated cells into pluripotent stem cells in a process known as reprogramming. Notably, partial and reversible reprogramming does not change cell identity but can reverse markers of aging in cells, improve the capacity of aged mice to repair tissue injuries, and extend longevity in progeroid mice. However, little is known about the mechanisms involved. Here, we have studied changes in the DNA methylome, transcriptome, and metabolome in naturally aged mice subject to a single period of transient OSKM expression. We found that this is sufficient to reverse DNA methylation changes that occur upon aging in the pancreas, liver, spleen, and blood. Similarly, we observed reversion of transcriptional changes, especially regarding biological processes known to change during aging. Finally, some serum metabolites and biomarkers altered with aging were also restored to young levels upon transient reprogramming. These observations indicate that a single period of OSKM expression can drive epigenetic, transcriptomic, and metabolomic changes toward a younger configuration in multiple tissues and in the serum