It’s probably too early in the research to confidently test rejuvenating small-molecule cocktails, but down the line, I think this will be a very promising avenue for the ITP to test
One of the most effective current rejuvenation cocktails is VC6TF, which consists of valproic acid (HDAC inhibitor), CHIR-99021 (GSK-3 inhibitor), E-616452 (TGFβRI inhibitor), tranylcypromine (irreversible MAO inhibitor that also inhibits the histone demethylase KDM1A), and forskolin (adenylyl cyclase activator currently being tested in the ITP).
Right now we have results on various cocktails showing rejuvenation in human fibroblasts, but we need to know which of these cocktails can also rejuvenate transcriptome and reduce epigenetic age in various mice tissues, without loss of cellular identity. We also need to know the minimum concentrations needed for each component of the cocktail, to make delivery feasible and minimize off-target toxicity.
Follow-up studies are underway to elucidate the cellular machinery that mediates these rejuvenative effects, with an emphasis on the mechanisms by which cells apparently write then later read a “backup copy” of earlier epigenetic information to reset chromatin structures and reestablish youthful gene expression patterns.
^ There is more work being done on this as we speak.
Although I don’t find it a convincing idea that cells contain a backup of epigenetic information, perhaps they meant that as an analogy? I think that cell type-specific epigenetic marks are (obviously) thermodynamically favorable, at least in newly differentiated cells. This is due to cell type-specific complements of transcription factors and other DNA-binding proteins which favor certain loci and create stable methylation patterns at those loci, and this steady-state is obviously favored in the presence of youthful metabolome, youthful proteome, and youthful values of other high-level information like electric and ionic gradients.
Over time, or perhaps even shortly after differentiation, some of those loci-specific DNA-binding proteins are lost, and the youthful patterns of DNA methylation are no longer thermodynamically favorable. This in turn further changes the patterns of DNA-binding proteins, which further changes the DNA methylation. It’s a vicious cycle.
From this perspective, cellular rejuvenation is more like folding a protein than it is burning a CD. If you can push the proteome (and especially the DNA-binding subset of the proteome) and the metabolome towards a newly differentiated/youthful state, you get youthful DNA methylation for free, since those patterns of DNA methylation are favorable under those conditions.
So it’s about finding small molecules which can mimic or induce that initial set of DNA-binding proteins, and perhaps that might be a different set of molecules for each cell type. And as far as essential organs go, you’re only as good as your weakest one, so you would have scheduled pulses of each cocktail for each organ to avoid interactions and minimize extended exposure (in this view you’re resetting the clock and not just slowing the rate it ticks, so pulsing should work just fine).