All life hinges on the storage and preservation of information. In eukaryotes, two main repositories of information exist: the genome and the epigenome. These information repositories work interdependently to coordinate the production and operation of life’s molecular machinery. However, they differ in fundamental ways.
Genetic information is digital and largely consistent across all cells in the body throughout an individual’s lifespan.
In contrast, epigenetic information, encoded by a less stable digital-analog system, varies between cells and changes in response to the environment and over time.
The Hallmarks of Aging
At least a dozen “hallmarks of aging” contribute to the deterioration and dysfunction of cells as they age. Researchers have gathered compelling evidence, from yeast to mammals, supporting the idea that a loss of epigenetic information, resulting in changes in gene expression, leads to the loss of cellular identity. These findings are consistent with the Information Theory of Aging, which proposes that a decline in information, specifically epigenetic information, triggers a cascade of events, including mitochondrial dysfunction, inflammation, and cellular senescence, leading to a progressive decline in cell and tissue function, manifesting as aging and age-related diseases, including glaucoma.
Here are two related articles specifically connecting this exciting research to vision restoration in glaucoma.
Research from David Sinclair's team: old, blind mice have regained their eyesight : AskGlaucoma
Breakthrough: Restoration of Visual Function in Nonhuman Primates : AskGlaucoma
Cellular Senescence and Aging
Cellular senescence is a state of permanent cell cycle arrest that facilitates wound repair, tissue remodeling, and avoidance of cancer by halting proliferation in aged and damaged cells. Senescence is associated with alterations in cell morphology, chromatin architecture, and the release of inflammatory factors in a process referred to as the senescence-associated secretory phenotype (SASP). The transition to cellular senescence can be initiated by a loss of epigenetic information, as well as telomere shortening, irreparable DNA damage, and cytoplasmic DNA. The accumulation of senescent cells with age promotes inflammation and generates additional reactive oxygen species (ROS), both locally and across the organism, contributing to a broad range of age-related diseases, from macular degeneration, to increased blood pressure, to metabolic dysregulation.
The Promise of Cell Reprogramming
Starting in 1962, Gurdon and others demonstrated that nuclei contain the necessary information to generate new individuals with normal lifespans. In 2006, Takahashi and Yamanaka demonstrated that the expression of four transcription factors, OCT4, SOX2, KLF4, and c-MYC (collectively known as “OSKM”), reprograms the developmental potential of adult cells, enabling them to be converted into various cell types. These findings initiated the field of cell reprogramming, with a string of publications in the 2000s showing that the identity of many different types of adult cells from different species could be erased to become induced pluripotent stem cells, commonly known as “iPSCs”.
The ability of the Yamanaka factors to erase cellular identity raised a key question: is it possible to reverse cellular aging in vivo without causing uncontrolled cell growth and tumorigenesis? Initially, it didn’t seem so, as mice died within two days of expressing OSKM. But work by the Belmonte lab, our lab, and others have confirmed that it is possible to safely improve the function of tissues in vivo by pulsing OSKM expression or by continuously expressing only OSK, leaving out the oncogene c-MYC.
In the optic nerve, for example, expression of a three Yamanaka factor combination safely resets DNA methylomes and gene expression patterns, improving vision in old and glaucomatous mice via a largely obscure mechanism that requires TET DNA demethylases.
Numerous tissues, including brain tissue, kidney, and muscle, have now been reprogrammed without causing cancer. In fact, expression of OSK throughout the entire body of mice extends their lifespan. Together, these results are consistent with the existence of a “back-up copy” of a youthful epigenome, one that can be reset via partial reprogramming to regain tissue function, without erasing cellular identity or causing tumorigenesis.
The Future of Regenerative Medicine
Currently, translational applications that aim to reverse aging, treat injuries, and cure age-related diseases, rely on the delivery of genetic material to target tissues. This is achieved through methods like adeno-associated viral (AAV) delivery of DNA and lipid nanoparticle-mediated delivery of RNA. These approaches face potential barriers to them being used widely, including high costs and safety concerns associated with the introduction of genetic material into the body.
Developing a chemical alternative to mimic OSK’s rejuvenating effects could lower costs and shorten timelines in regenerative medicine development. This advancement might enable the treatment of various medical conditions and potentially even facilitate whole-body rejuvenation, and that's the breakthrough discovery of this research work.
In this study, researchers tested six cocktails of small molecules. Some of the key molecules are common dietary supplements (e.g., forksolin and Alpha-Ketoglutarate (α-KG). At least one is a common fatty acid found in ghee, butter and produced by intestinal microbiota (butyric acid).
Three of the cocktails were based on Cocktail 1 as well as two additives (referred to as Cocktail 2 and 3) and the other three based on Cocktail 4 plus additional additives (referred to as Cocktail 5 and 6).
The final concentrations of the chemicals in each cocktail are also provided in the paper in Table 2. These chemical cocktails represent a promising step towards the development of treatments that can reverse cellular aging and potentially rejuvenate the entire body.
The table is reproduced below:
| GING Supplementary Table 2. Cocktail Combinations | |||
|---|---|---|---|
| Cocktail # | Chemicals | Final concentration (μM) | |
| 1 | VPA | 250 | |
| CHIR99021 | 10 | ||
| Repsox-616452 | 10 | ||
| Tranylcypromine | 5 | ||
| Forskolin (FSK) | 50 | ||
| 2 | VPA | 250 | |
| CHIR99021 | 10 | ||
| Repsox-616452 | 10 | ||
| Tranylcypromine | 5 | ||
| Forskolin (FSK) | 50 | ||
| Sodium Butyrate | 200 | ||
| 3 | VPA | 250 | |
| CHIR99021 | 10 | ||
| Repsox-616452 | 10 | ||
| Tranylcypromine | 5 | ||
| Forskolin (FSK) | 50 | ||
| bFGF | 100 ng/ml | ||
| 4 | CHIR99021 | 10 | |
| Repsox-616452 | 10 | ||
| TTNPB | 2 | ||
| Y27632 | 2 | ||
| SAG | 0.5 | ||
| ABT869 | 1 | ||
| 5 | CHIR99021 | 10 | |
| Repsox-616452 | 10 | ||
| TTNPB | 2 | ||
| Y27632 | 2 | ||
| SAG | 0.5 | ||
| ABT869 | 1 | ||
| Sodium Butyrate | 200 | ||
| 6 | CHIR99021 | 10 | |
| Repsox-616452 | 10 | ||
| TTNPB | 2 | ||
| Y27632 | 2 | ||
| SAG | 0.5 | ||
| ABT869 | 1 | ||
| α-KG | 500 |
Here are the descriptions for all the chemicals:
Forskolin (FSK): A natural labdane diterpene produced by the plant Coleus barbatus (Blue Spur Flower). It activates cyclic adenosine monophosphate, which helps regulate blood glucose and fat metabolism levels. It is a common dietary supplement.
Valproic Acid (VPA): A chemical compound widely used as an antiepileptic drug. It regulates ionic currents and facilitates GABAergic over glutamatergic transmission, modulating neurotransmitter release and strengthening the threshold for seizure activity.
CHIR99021: A potent and selective inhibitor of glycogen synthase kinase 3 (GSK3). It promotes cell cycle activity and proliferation, and enhances cardiac differentiation efficiency.
Repsox-616452 (RepSox): A small molecule inhibitor of the transforming growth factor-beta receptor I (TGF-β-RI). It can induce adipogenesis from mouse embryonic fibroblasts and promote the differentiation of brown fat precursor cells.
Tranylcypromine: A monoamine oxidase inhibitor (MAOI) used as an antidepressant. It increases the levels of certain chemicals in the brain that help elevate mood.
Sodium Butyrate (SB): Also called butyric acid. A short-chain fatty acid produced by intestinal microbiota (and found in butter and ghee). It has beneficial effects on metabolic diseases such as obesity and non-alcoholic fatty liver disease (NAFLD).
Basic Fibroblast Growth Factor (bFGF): A member of the fibroblast growth factor family that plays a crucial role in wound healing and embryonic development. It promotes cell proliferation, differentiation, and survival.
TTNPB: A synthetic retinoid (i.e., a vitamin A derivative) that is a potent and selective agonist for the retinoic acid receptor (RAR). It modulates the activity of RAR, which plays a crucial role in cell growth, differentiation, and homeostasis.
Y27632: A selective inhibitor of Rho-associated coiled-coil forming protein serine/threonine kinase (ROCK). It is involved in various cellular functions, including contraction, motility, proliferation, and apoptosis.
SAG (Smoothened Agonist): A small molecule that activates the smoothened receptor, a component of the hedgehog signaling pathway. This pathway plays a crucial role in embryonic development and the maintenance and regeneration of adult tissues by regulating adult stem cells.
ABT869 (Linifanib): An orally active multi-targeted receptor tyrosine kinase inhibitor developed for the treatment of various cancers. It inhibits vascular endothelial growth factor and platelet-derived growth factor receptors.
Alpha-Ketoglutarate (α-KG): A key molecule in the Krebs cycle, playing a pivotal role in energy metabolism, amino acid synthesis, and other essential cellular processes. It serves as a substrate for α-KG-dependent dioxygenases, which are involved in the demethylation of histones and DNA, thereby regulating gene expression. It is a common dietary supplement.
Here are more details of each one:
Valproic Acid (VPA)
Valproic Acid (VPA) is a chemical compound that has been widely used in the medical field, particularly as an antiepileptic drug. It is known to have a broad spectrum of actions, including the regulation of ionic currents and the facilitation of GABAergic over glutamatergic transmission, which indirectly modulates neurotransmitter release and strengthens the threshold for seizure activity. Moreover, VPA has been reported to exert anti-epileptogenic effects through epigenetic mechanisms, including histone deacetylases (HDACs), BDNF and GDNF modulation, which are pivotal to orientate neurons toward a neuroprotective status and promote dendritic spines organization. VPA is also under investigation for its potential benefits in stroke and traumatic brain injury, and as a positive modulator of chemotherapy in cancer treatment. However, it's important to note that VPA can also induce kidney proximal tubular injury and renal failure (Fanconi syndrome; FS), which is a clinical complication.
CHIR99021
CHIR99021 is a potent and selective inhibitor of glycogen synthase kinase 3 (GSK3), which is a serine/threonine protein kinase involved in various cellular processes. It has been widely used in stem cell research due to its ability to maintain self-renewal and pluripotency of embryonic stem cells. CHIR99021 can promote cell cycle activity and proliferation, and it has been found to be particularly effective in enhancing cardiac differentiation efficiency. Moreover, it has been shown to modulate Wnt/β-catenin signaling, which plays a crucial role in stem cell regulation. However, it's important to note that CHIR99021 can also be cytotoxic under certain conditions, such as when cells are in the G1 phase of the cell cycle.
RepSox
Repsox-616452, also known as RepSox, is a small molecule inhibitor of the transforming growth factor-beta receptor I (TGF-β-RI). It has been found to play a significant role in various biological processes. For instance, it can induce adipogenesis from mouse embryonic fibroblasts in fibroblast culture medium. Moreover, it has been reported to promote the differentiation of brown fat precursor cells and induce browning of white fat precursor cells, suggesting potential therapeutic applications for obesity and type 2 diabetes. In the context of neural progenitor cells, RepSox has been used in a chemical cocktail to generate these cells from mouse embryonic fibroblasts under physiological hypoxic conditions. It's important to note that the effects of RepSox can vary depending on the specific cellular context and the presence of other factors.
Tranylcypromine
Tranylcypromine is a monoamine oxidase inhibitor (MAOI) that is used as an antidepressant in the treatment of major depressive disorders. It works by increasing the levels of certain chemicals in the brain that help elevate mood. In addition to its antidepressant properties, tranylcypromine has been found to have other potential therapeutic applications. For instance, it has been used in combination with all-trans-retinoic acid (ATRA) as a salvage therapy for relapsed/refractory acute myeloid leukemia (AML), showing potential in inducing differentiation of AML blasts and leading to clinical response. Moreover, tranylcypromine has been identified as a potent and selective dopamine D3 receptor antagonist, which could have implications for the treatment of certain neurological and psychiatric disorders. Recent research has also suggested that tranylcypromine could have neurotoxic effects in human-induced pluripotent stem cell-derived cerebral organoids, and it has been shown to suppress lesion growth and improve generalized hyperalgesia in a mouse model of induced endometriosis.
Forskolin
Forskolin (FSK) is a natural labdane diterpene produced by the plant Coleus barbatus (Blue Spur Flower). It is widely available as a dietary supplement and it has been used for centuries in various forms of natural medicine. According to Ayurveda and other traditional systems of medicine, forskolin benefits include its ability to help treat heart problems, digestive disorders, skin damage (such as burns or cuts), skin conditions (like eczema and psoriasis), urinary tract infections (UTI), asthma and various other conditions. Modern medicine shows that it activates cyclic adenosine monophosphate. The activation of cAMP is important because cAMP helps regulate blood glucose and fat metabolism levels.
Butyric Acid
Sodium Butyrate (SB) or Butyric Acid is a short-chain fatty acid that is produced by intestinal microbiota. It has been found to have various beneficial effects on health, particularly in relation to metabolic diseases such as obesity and non-alcoholic fatty liver disease (NAFLD). Sodium Butyrate has been shown to attenuate obesity-induced intestinal barrier dysfunction and endotoxemia, and it can induce the expression of antimicrobial peptides. Moreover, it has been found to inhibit hepatic steatosis, improve lipid profile, and improve liver function in a mouse model of NAFLD, largely through the activation of the LKB1-AMPK-Insig signaling pathway. Sodium Butyrate has also been shown to have potential therapeutic applications in the context of ischemic stroke, particularly in patients with type 2 diabetes, by ameliorating the exacerbation of brain infarction.
Basic Fibroblast Growth Factor
Basic Fibroblast Growth Factor (bFGF), also known as FGF2, is a member of the fibroblast growth factor family that plays a crucial role in wound healing and embryonic development. It is involved in a variety of biological processes, including the promotion of cell proliferation, differentiation, and survival. bFGF has been widely used in tissue engineering and regenerative medicine due to its ability to stimulate the regeneration of tissues such as skin, cartilage, and bone. It has also been found to enhance the healing of burn wounds by promoting cell-induced tissue regeneration. Moreover, bFGF can stimulate the production of extracellular matrix and the formation of new blood vessels, which are essential for wound healing. However, it's important to note that the effects of bFGF can vary depending on the specific cellular context and the presence of other factors.
TTNPB
TTNPB, also known as 4-[(E)-2-(5,6,7,8-Tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)propenyl]benzoic acid, is a synthetic retinoid that is known to be a potent and selective agonist for the retinoic acid receptor (RAR). It has been used in various biological studies due to its ability to modulate the activity of RAR, which plays a crucial role in cell growth, differentiation, and homeostasis. For instance, TTNPB has been found to increase the expression of apo C-III, an antagonist of plasma triglyceride catabolism, which may contribute to the hypertriglyceridemia observed after retinoid therapy. Moreover, TTNPB has been shown to induce striking digit pattern changes when continuously released in an early chick wing bud, suggesting that it may serve as a natural "morphogen" in the limb. However, it's important to note that the effects of TTNPB can vary depending on the specific cellular context and the presence of other factors.
Y27632
Y27632 is a selective inhibitor of Rho-associated coiled-coil forming protein serine/threonine kinase (ROCK). Rho kinases are involved in various cellular functions, including contraction, motility, proliferation, and apoptosis. In the context of the eye, Y27632 has been shown to increase outflow facility, which is the ease with which fluid can exit the eye. This effect is associated with changes in the hydrodynamic patterns of outflow and morphological changes in the inner wall and juxtacanalicular tissue of the eye. In addition to its effects on outflow facility, Y27632 has been found to have other potential therapeutic applications. For instance, it has been used to promote neurite growth in primary cells of cortical neurons and to stimulate axon regeneration and recovery of hindlimb function after spinal cord injury in mice. However, it's important to note that the effects of Y27632 can vary depending on the specific cellular context and the presence of other factors.
SAG
SAG, or Smoothened Agonist, is a small molecule that activates the smoothened receptor, a component of the hedgehog signaling pathway. This pathway plays a crucial role in embryonic development, including the growth of digits on limbs and the organization of the brain. In adults, the hedgehog pathway contributes to the maintenance and regeneration of adult tissues by regulating adult stem cells. SAG has been used in various biological studies due to its ability to modulate the activity of the hedgehog pathway. However, it's important to note that the effects of SAG can vary depending on the specific cellular context and the presence of other factors.
ABT869
ABT869, also known as Linifanib, is an orally active multi-targeted receptor tyrosine kinase inhibitor that has been developed for the treatment of various cancers. It is designed to inhibit vascular endothelial growth factor and platelet-derived growth factor receptors, which play crucial roles in the growth and spread of cancer cells. Linifanib has been in phase III development for liver cancer and phase II development for non-small cell lung cancer, breast cancer, and colorectal cancer in the US, the EU, and other areas of the world. However, it's important to note that the effects of ABT869 can vary depending on the specific cellular context and the presence of other factors.
Alpha-Ketoglutarate (α-KG)
Alpha-Ketoglutarate (α-KG) is a key molecule in the Krebs cycle, playing a pivotal role in energy metabolism, amino acid synthesis, and other essential cellular processes. It is an intermediate in the Krebs cycle, which is the primary metabolic pathway for the aerobic production of energy from carbohydrates and fatty acids. α-KG is also a precursor for the synthesis of glutamate, a neurotransmitter involved in cognitive functions. Moreover, α-KG serves as a substrate for α-KG-dependent dioxygenases, which are involved in the demethylation of histones and DNA, thereby regulating gene expression. Dysregulation of these enzymes has been linked to various diseases, including cancer. Therefore, α-KG and its derivatives have potential therapeutic applications in a wide range of diseases.
Chemically induced reprogramming to reverse cellular aging - PubMed
PMID: 37437248
- DOI: 10.18632/aging.204896
- Free article