Partial cellular reprogramming: A deep dive into an emerging rejuvenation technology.

Cellular senescence and cellular reprogramming represent two fundamentally intertwined processes that profoundly influence aging and cancer. This paper explores how the permanent cell-cycle arrest of senescent cells and the identity-resetting capacity of reprogramming jointly shape biological outcomes in later life and tumor development. We synthesize recent findings to show that senescent cells, while halting the proliferation of damaged cells, can paradoxically promote tissue dysfunction and malignancy via their secretory phenotype. Conversely, induced reprogramming of somatic cells-exemplified by Yamanaka factors-resets cellular age and epigenetic marks, offering a potential to rejuvenate aged cells. Key findings highlight shared mechanisms (e.g., DNA damage responses and epigenetic remodeling) and bidirectional crosstalk between these processes: senescence signals can facilitate neighboring cell plasticity, whereas reprogramming attempts can trigger intrinsic senescence programs as a barrier. In aging tissues, transient (partial) reprogramming has been shown to erase senescence markers and restore cell function without inducing tumorigenesis, underlining a novel strategy to combat age-related degeneration. In cancer, we discuss how therapy-induced senescence of tumor cells may induce stem-cell-like traits in some cells and drive relapse, revealing a delicate balance between tumor suppression and tumor promotion. Understanding the interplay between senescence and reprogramming is crucial for developing innovative therapies. By targeting the senescence-reprogramming axis-for instance, via senolytic drugs, SASP inhibitors, or safe reprogramming techniques-there is significant therapeutic potential to ameliorate aging-related diseases and improve cancer treatment. Our findings underscore that carefully modulating cellular senescence and rejuvenation processes could pave the way for novel regenerative and anti-cancer strategies.

Age-related diseases, including neurodegenerative disorders, cardiovascular diseases, and cancer, are major health concerns globally. Cellular senescence, characterized by irreversible cell cycle arrest, plays a central role in the aging process and the development of these diseases. The mechanistic target of rapamycin (mTOR) pathway, a key regulator of cellular growth and metabolism, has been implicated in both aging and the progression of age-related diseases. Emerging evidence suggests that polyphenols, plant-derived bioactive compounds, can modulate the mTOR pathway and influence cellular senescence. These compounds exhibit antioxidant, anti-inflammatory, and anti-cancer properties, which may help alleviate the detrimental effects of aging and prevent age-related diseases. This review explores the role of polyphenols in modulating the mTOR signaling pathway, with a particular focus on their effects on cellular senescence. We examine how polyphenols can influence the mTOR pathway at different levels, from activation to inhibition, and discuss their potential therapeutic implications in mitigating aging-related cellular dysfunction. Polyphenols such as resveratrol, quercetin, and curcumin have demonstrated mTOR modulation, with studies showing a reduction in cellular senescence markers and improved cellular function. Additionally, the potential for these compounds in clinical applications for age-related diseases is evaluated. The review highlights the need for further research to understand the molecular mechanisms underlying polyphenol action on mTOR and its link to cellular senescence. Ultimately, understanding these interactions could provide new avenues for the development of dietary interventions and pharmaceuticals aimed at promoting healthy aging and preventing age-related diseases.

AI in cellular engineering and reprogramming

Cellular senescence, a hallmark of aging, is defined as irreversible cell cycle arrest in response to various stimuli. It plays both beneficial and detrimental roles in cellular homeostasis and diseases. Quality control (QC) is important for the proper maintenance of cellular homeostasis. The QC machineries regulate the integrity of RNA and protein by repairing or degrading them, and are dysregulated during cellular senescence. QC dysfunction also contributes to multiple age-related diseases, including cancers and neurodegenerative, muscle, and cardiovascular diseases. In this review, we describe the characters of cellular senescence, discuss the major mechanisms of RNA and protein QC in cellular senescence and aging, and comprehensively describe the involvement of these QC machineries in age-related diseases. There are many open questions regarding RNA and protein QC in cellular senescence and aging. We believe that a better understanding of these topics could propel the development of new strategies for addressing age-related diseases.

Cellular senescence is one of the most significant factors involved in aging and age-related diseases. Senescence of vascular smooth muscle cells (VSMCs) adversely affects the function of the cardiovascular system and contributes to the development of atherosclerosis, hypertension, and other cardiovascular diseases. Glucagon-like peptide-1 (GLP-1) is an important incretin hormone involved in insulin release and vascular tone. GLP-1 is quickly degraded by the enzyme dipeptidyl peptidase-4 (DPP-4). Omarigliptin is a new DPP-4 inhibitor that has demonstrated anti-inflammatory and antioxidative stress properties. In the present study, we investigated the effects of the selective DPP-4 inhibitor omarigliptin (OMG) on VSMCs exposed to insult from tumor necrosis factor-α (TNF-α), one of the main inflammatory signaling molecules involved in cellular senescence. We found that OMG could suppress TNF-α-induced expression of pro-inflammatory cytokines (interleukin-1β (IL-1β), IL-6, and IL-8) and inhibit oxidative stress by reducing the production of H2O2 and protein carbonyl. OMG ameliorated the increase in senescence-associated β-galactosidase (SA-β-gal) and telomerase activity induced by TNF-α. The plasminogen activator inhibitor-1 (PAI-1)/p53/p21 pathway is a key inducer of cellular senescence. OMG ameliorated the acetylation of p53 at lysine 382 (K382) and subsequent activation of p21 via inhibition of PAI-1. Importantly, our experiments revealed that blockage of silent information-regulator 1 (SIRT1) abolished the inhibitory effects of OMG on p53 acetylation, SA-β-gal activity, and telomerase activity in VSMCs. These results suggest that OMG may have the potential to delay or prevent the progression of age-related cardiovascular diseases by modulating the activity of SIRT1.

Cellular plasticity of cancer cells is often associated with phenotypic heterogeneity and drug resistance and thus remains a major challenge for the treatment of melanoma and other types of cancer. Melanoma cells have the capacity to switch their phenotype during tumor progression, from a proliferative and differentiated phenotype to a more invasive and dedifferentiated phenotype. However, the molecular mechanisms driving this phenotype switch are not yet fully understood. Considering that cellular heterogeneity within the tumor contributes to the high plasticity typically observed in melanoma, it is crucial to generate suitable models to investigate this phenomenon in detail. Here, we discuss the use of complete and partial reprogramming into induced pluripotent cancer (iPC) cells as a tool to obtain new insights into melanoma cellular plasticity. We consider this a relevant topic due to the high plasticity of melanoma cells and its association with a strong resistance to standard anticancer treatments.

Aging is considered a risk factor for developing many chronic diseases which includes cardiovascular diseases, cancer, and neurodegenerative diseases. Researchers are now showing that many of these diseases are associated with cellular senescence. Cellular senescence is an important process for the removal of damaged cells, but if senescent cells are not removed a chronic pro-inflammatory environment ensues, increasing the risk of many age-related diseases. These cells accumulate as a result of cancer chemotherapy, are associated with age-related diseases, and are important for development. Recent work has shown that specific targeting of senescent cells results in increased life expectancy in a progeroid Ercc1-/Δ mouse model. As such there is great interest in identifying, characterizing and targeting senescent cells. Senescent cells are identified by the release of pro-inflammatory cytokines and chemokines, increased beta galactosidase activity (b-gal), senescence associated heterochromatin foci (SAHF), and changes in morphology which are increased size and a flattened appearance. There is no single good marker for determining senescence, so these cells are identified through the collective interpretation of multiple markers. Senescence associated b-gal (SA-b-gal) is considered the “gold standard” for identifying senescent cell, and it is detected with the blue-green precipitating colorimetric x-gal substrate. However, this substrate is limited use in that it cannot be used in flow cytometry or other fluorescence based platforms. Even though C12FDG, a fluorescein based b-gal substrate, has been used since the mid 90’s, it has limited utility restricted by its lack of fix-ability. Newer b-gal substrates are demonstrated here which do not leak out of cell; enabling researchers to more easily identify and evaluate cellular senescence. In this study we use a fluorescence approach to assess the senescence phenotype based on a combination of western blots, fluorescence based imaging and ICC, flow cytometry, cell sorting, and RT-qPCR. We examined several cell-based models include replicative senescence characterized by telomere shortening in primary fibroblasts, cellular senescence characterized through DNA damage pathway by doxorubicin, oxidative stress senescence induced by confluency in atmospheric oxygen environment (SIPS), and senescence induced with palbociclib treatment (a CDK 4/6 inhibitor). Overall, we found that phenotypic characteristics of senescence vary depending on the cellular model and that a multiplex fluorescence based approach to identifying senescent cells will contribute to the understanding of cellular senescence and the age-related diseases. Citation Format: Scott T. Clarke, Taryn Jackson, Amanda Kelley, Quentin Low, Timothy Huang, Yi-Zhen Hu, Veronica Calderon, Rong Wang, Michael O'Grady. Evaluation of cellular senescence through fluorescence characterization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 898.

Deciphering the emerging interrelationship between cellular senescence and extracellular vesicles: Implications for therapy and diagnosis.

Cellular senescence, a term originally used to define the characteristics of normal human fibroblasts that reached their replicative limit, is an important factor for ageing, age-related diseases including cancer, and cell reprogramming. These outcomes are mediated by senescence-associated changes in gene expressions, which sometimes lead to the secretion of pro-inflammatory factors, or senescence-associated secretory phenotype (SASP) that contribute to paradoxical pro-tumorigenic effects. p53 functions as a transcription factor in cell-autonomous responses such as cell-cycle control, DNA repair, apoptosis, and cellular senescence, and also non-cell-autonomous responses to DNA damage by mediating the SASP function of immune system activation. The human TP53 gene encodes twelve protein isoforms, which provides an explanation for the pleiotropic p53 function on cellular senescence. Recent reports suggest that some short isoforms of p53 may modulate gene expressions in a full-length p53-dependent and -independent manner, in other words, some p53 isoforms cooperate with full-length p53, whereas others operate independently. This review summarizes our current knowledge about the biological activities and functions of p53 isoforms, especially Δ40p53, Δ133p53α, and p53β, on cellular senescence, ageing, age-related disorder, reprogramming, and cancer. Numerous cellular and animal model studies indicate that an unbalance in p53 isoform expression in specific cell types causes age-related disorders such as cancer, premature ageing, and degenerative diseases.

In this review, we seek a novel strategy for establishing a rejuvenating microenvironment through senescent cells specific reprogramming. We suggest that partial reprogramming can produce a secretory phenotype that facilitates cellular rejuvenation. This strategy is desired for specific partial reprogramming under control to avoid tumour risk and organ failure due to loss of cellular identity. It also alleviates the chronic inflammatory state associated with ageing and secondary senescence in adjacent cells by improving the senescence-associated secretory phenotype. This manuscript also hopes to explore whether intervening in cellular senescence can improve ageing and promote damage repair, in general, to increase people’s healthy lifespan and reduce frailty. Feasible and safe clinical translational protocols are critical in rejuvenation by controlled reprogramming advances. This review discusses the limitations and controversies of these advances’ application (while organizing the manuscript according to potential clinical translation schemes) to explore directions and hypotheses that have translational value for subsequent research.

Cellular senescence, an irreversible state of growth arrest, underlies organismal aging and age-related diseases. Recent evidence suggests that aging intervention based on inhibition of cellular senescence might be a promising strategy for treatment of aging and age-related diseases. Embryonic stem cells (ESCs) and ESC conditioned medium (CM) have been suggested as a desirable source for regenerative medicine. However, effects of ESC-CM on cellular senescence remain to be determined. We found that treatment of senescent human dermal fibroblasts with CM from mouse ESCs (mESCs) decreases senescence phenotypes. We found that platelet-derived growth factor BB in mESC-CM plays a critical role in antisenescence effect of mESC-CM through up-regulation of fibroblast growth factor 2. We confirmed that mESC-CM treatment accelerates the wound-healing process by down-regulating senescence-associated p53 expression in in vivo models. Taken together, our results suggest that mESC-CM has the ability to suppress cellular senescence and maintain proliferative capacity. Therefore, this strategy might emerge as a novel therapeutic strategy for aging and age-related diseases.

Cellular senescence contributes to tissue and organismal aging, tumor suppression and progress, tissue repair and regeneration, and age-related diseases. Thus, aging intervention might be beneficial for treatment and prevention of diverse age-related diseases. In the present study, we investigated whether four compounds purified from Inula japonica exert inhibitory activity against cellular senescence induced by adriamycin in human umbilical vein endothelial cells (HUVECs). Among them, compound 4 (quercetagetin 3,4'-dimethyl ether) showed inhibitory activity against cellular senescence, which was confirmed by senescence-associated β-galactosidase (SA-β-gal) activity, p53 and p21 protein levels, and intracellular ROS levels. Compound 4 also reduced SA-β-gal activity in HUVECs under replicative senescence. These results suggest that compound 4 represses cellular senescence in HUVECs and might be useful for the development of dietary supplements or cosmetics that alleviate tissue aging or age-related diseases.

Cellular senescence (CS) is an important contributor to aging and age-related diseases such as Alzheimer's Disease (AD). Senescent cells are characterized by a durable cell cycle arrest and the acquisition of a senescence-associated secretory phenotype (SASP). Clearance of senescent astrocytes and microglia in an AD mouse model prevented tau-dependent pathology and cognitive decline suggesting pharmacological agents targeting CS might provide novel therapeutic approaches for AD. The tumor suppressor gene p53 plays a pivotal role in the initiation and maintenance of CS. Upregulation of p53 induces tau phosphorylation and inhibition of p53 has been shown to attenuate amyloid-beta mediated neuronal death. Our lab has shown delta133p53 regulates replicative CS by acting as a dominant-negative to full-length p53. We observe high levels of delta133p53 in proliferative cells, while conversely senescent cells, such as astrocytes from AD patients, have decreased levels of the isoform. Overexpression of delta133p53 restores the replicative capacity of near-senescent astrocytes and decreases the secretion of several SASP factors including interleukin 6 (IL-6). Our study aims at identifying small molecule compounds that increase delta133p53 expression to counteract CS. We developed a cell-based high-throughput screening assay using cell lines generated to express a translational reporter system, where the delta133p53 cDNA sequence is cloned in frame with the GFP. The biological activity of the fusion protein was confirmed by evaluating its nuclear localization, autophagic degradation and ability to inhibit CS. In collaboration with the National Center for Advancing Translational Sciences (NCATS), we screened two large chemical libraries consisting of approximately 8,500 compounds. Following the fluorescent-based primary screening assay, 95 compounds were screened in a secondary assay to evaluate their efficacy at reducing astrocyte secretion of IL-6 following irradiation. We are currently confirming the activity of 13 compounds on endogenous delta133p53 levels. We will further validate the candidate compounds by assessing their effect on DNA damage, cell proliferation, SASP and CS. Additionally, we plan to screen the Genesis Chemical Library (95,744 compounds), that contains novel chemotypes which have the potential to form new drugs. This first drug discovery program to target delta133p53 could potentially lead to the development of a first-in-class drug.

Aging is a progressive degenerative process involving a chronic low-grade inflammation and the accumulation of senescent cells. One major issue is to reveal the mechanisms which promote the deposition of pro-inflammatory senescent cells within tissues. The accumulation involves mechanisms which increase cellular senescence as well as those inhibiting the clearance of senescent cells from tissues. It is known that a persistent inflammatory state evokes a compensatory immunosuppression which inhibits pro-inflammatory processes by impairing the functions of effector immune cells, e.g., macrophages, T cells and natural killer (NK) cells. Unfortunately, these cells are indispensable for immune surveillance and the subsequent clearance of senescent cells, i.e., the inflammation-induced counteracting immunosuppression prevents the cleansing of host tissues. Moreover, senescent cells can also repress their own clearance by expressing inhibitors of immune surveillance and releasing the ligands of NKG2D receptors which impair their surveillance by NK and cytotoxic CD8+ T cells. It seems that cellular senescence and immunosuppression establish a feed-forward process which promotes the aging process and age-related diseases. I will examine in detail the immunosuppressive mechanisms which impair the surveillance and clearance of pro-inflammatory senescent cells with aging. In addition, I will discuss several therapeutic strategies to halt the degenerative feed-forward circuit associated with the aging process and age-related diseases.

Cellular senescence, a permanent state of cell cycle arrest, is believed to have originally evolved to limit the proliferation of old or damaged cells. However, it has been recently shown that cellular senescence is a physiological and pathological program contributing to embryogenesis, immune response, and wound repair, as well as aging and age-related diseases. Unlike replicative senescence associated with telomere attrition, premature senescence rapidly occurs in response to various intrinsic and extrinsic insults. Thus, cellular senescence has also been considered suppressive mechanism of tumorigenesis. Current studies have revealed that therapy-induced senescence (TIS), a type of senescence caused by traditional cancer therapy, could play a critical role in cancer treatment. In this review, we outline the key features and the molecular pathways of cellular senescence. Better understanding of cellular senescence will provide insights into the development of powerful strategies to control cellular senescence for therapeutic benefit. Lastly, we discuss existing strategies for the induction of cancer cell senescence to improve efficacy of anticancer therapy.