• Sinclair and colleagues show that six chemical combinations reverse cellular age within a week of applying them.
  • Using gene activity-based aging clocks (RNA-seq technology), Sinclair and colleagues confirm the cells’ age reversal after treatment with the chemical combinations.
  • The cells don’t exhibit signs of turning to stem cells, which could potentially trigger cancer in living tissue.

In 2006, Takahashi and Yamanaka demonstrated that expressing four proteins called Yamanaka factors — OCT4, SOX2, KLF4, and c-MYC — enabled cells to reenter a more youthful state where they could be converted to various cell types. This landmark discovery provided hope that increasing these proteins’ abundance in cells could rejuvenate them and restore their younger functional properties. However, the high cost of genetic manipulation techniques (gene therapies) used to increase Yamanaka factor abundance makes them difficult to research and apply to humans. Finding a pill that could have similar effects as Yamanaka factors would save money and time for application.

Published in Aging, Sinclair and colleagues from Harvard Medical School show that six cocktails composed of small molecules used to transform cells to their stem cell state effectively reverse human cell aging. These findings were shown with an assay detecting nuclear compartmentalization and separation of cellular proteins, an indicator of cell rejuvenation, and a gene activity (transcription)-based aging clock. The researchers went on to show that the rejuvenated cells didn’t show signs of becoming stem cells, which can drive excessive cellular growth and proliferation. These findings suggest that developing small molecule cocktails may provide a means to reverse cellular aging without inducing cells to enter their stem cell state, which could one day reverse human aging.

“This new discovery offers the potential to reverse aging with a single pill, with applications ranging from improving eyesight to effectively treating age-related diseases,” said David Sinclair, the study’s principal investigator, in a press release.

Six Chemical Cocktails Effectively Reverse Cellular Aging

To identify molecules that rejuvenate old and senescent cells — cells that no longer replicate and contribute to aging with their release of inflammatory molecules — Sinclair and colleagues curated a list of molecules known to reprogram human connective tissue cells (fibroblasts) to their stem cell state. The researchers tested the molecules on human fibroblasts using a technique measuring the compartmentalization of proteins between the cell’s nucleus and aqueous interior outside of the nucleus (the cytosol). Senescent cells display poor compartmentalization compared to younger cells, and molecules that improve senescent cell compartmentalization rejuvenate the cells, purportedly transforming them to a younger state. Among 80 cocktails tested using this assay, six statistically improved compartmentalization within four days of treatment. These results suggest that this aspect of human cellular aging can be reversed with the addition of the six molecular combinations.

(Yang et al., 2023 | Aging) Treating with the six cocktails effectively restores cell protein compartmentalization, an indicator of rejuvenation. Increased overlap (correlation) between mCherry (labeling cell nucleus proteins) with eGFP (labeling cytosolic proteins) indicates lower compartmentalization in senescent cells (Sene) compared to dormant, quiescent cells (Quie). The cocktails (C1 through C6) effectively restore compartmentalization.

Sinclair and colleagues sought to ensure that gene activity profiles confirmed the human cell rejuvenation with a gene-activity based aging clock. Compared to old and senescent cells, the aging clock confirmed that the six small molecule combinations substantially decreased the cells’ age, transforming them to a more youthful state. Interestingly, three of the six cocktails reduced the cellular age by more than three years after only four days of treatment.

(Yang et al., 2023 | Aging) Compared to old and senescent cells, senescent cells treated with the six cocktails exhibit statistically reduced age. Compared to old cells (Quiescence) and senescent cells (Sene), senescent cells treated with the cocktails (C1 through C6) display markedly reduced ages, with C1, C2, and C3 conferring age reductions of three years or more.

To avoid unabated cellular proliferation and growth, which may precipitate cancer, it’s important that the six cocktails don’t transform senescent cells to stem cells. For this reason, Sinclair and colleagues measured stem cell protein markers — NANOG and EPCAM — in the rejuvenated cells. Importantly, following treatment with the cocktails, neither of these proteins were observed in the cells. These results support that the six cocktails can rejuvenate senescent human cells so that they transform to a younger state without becoming stem cells.

“Until recently, the best we could do was slow aging. New discoveries suggest we can now reverse it,” said David Sinclair, PhD in a press release.

Determining the Lasting Effects of Cellular Rejuvenation

An important remaining question is how long the cocktail-induced cellular rejuvenation effects last. To find answers regarding this issue, future research will need to examine cells for longer periods after removing the cocktails from the cells to make sure they don’t revert to their senescent state. Moreover, these results come from the treatment of cells in laboratory dishes, so it’ll be important to find whether they can be applied to live animals like mice.

If future research shows that the cocktails effectively reverse cell aging in mice, clinical trials will be necessary to find whether they can be applied to humans. Since aging is the single greatest contributor to human disease and suffering, these advances could pave the way for alleviating age-related diseases and possibly reversing physiological processes associated with aging.

(Yang et al., 2023 | Aging) Each of the cocktails used to reverse cellular aging contains five to seven small molecules. The table lists each molecule included in the six cocktails along with their concentrations used to treat human cells.