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Core Mechanisms

How telomere DNA and ribosomal DNA may function as biological countdown substances that drive cellular senescence through p53-mediated gene-expression programs.

Introductory Overview

TRCS proposes that aging is fundamentally a genetic program regulated through the progressive shortening of telomeres and/or ribosomal DNA (rDNA) arrays via the tumor suppressor protein p53 pathway, rather than being caused by the accumulation of molecular damage.

Within this framework, organismal aging arises from the replicative senescence of adult stem cells, a process co-regulated by telomeres and rDNA through p53-mediated gene-expression programs.

Furthermore, the eleven classical hallmarks of aging are interpreted as downstream consequences of p53 signaling following the shortening of telomere and rDNA arrays.

From a first-principles perspective, the lifespan of a species is ultimately determined by the rate at which telomeres and rDNA arrays shorten over time, a process jointly influenced by genetic and environmental factors.

01

Aging as a Programmed Life Cycle

Over billions of years of evolution, organisms have evolved mechanisms to counteract a wide range of random molecular damage. Furthermore, every living creature follows a relatively rigid timeline governing development, maturation, senescence, and death.

For this reason, ontogeny and aging are inherently a continuous, end-to-end genetic program, a process in which three major sets of genes are expressed in a programmed sequence along the timeline.

The early gene set primarily regulates embryonic development, the middle gene set centers on bodily health and reproduction, and the late gene set is mainly responsible for disrupting normal physiological functions.

Scientific illustration of the silkworm life cycle from eggs and larva to cocoon, adult moth, reproduction, senescence, and death.
Figure 1. The life cycle illustrates the programmed temporal sequence of development, maturation, reproduction, senescence, and death.
Diagram showing adult stem cells producing functional cells through life, with progressive changes associated with aging.
Figure 2. Adult stem cell replicative senescence progressively affects functional cell renewal, tissue integrity, and organismal aging.

02

Adult Stem Cell Replicative Senescence Drives Organismal Aging

Why do organisms age? The tissue cells that make up an organism fall into two categories: terminally differentiated cells and adult stem cells, which account for a very small proportion.

Both types of cells are eliminated by the immune system due to cellular senescence, gene mutations, viral infections, and other factors, and are subsequently replenished through self-renewal and differentiation of adult stem cells.

However, adult stem cells have a limited number of replication cycles. Therefore, the fundamental cause of organismal aging is the replicative senescence of adult stem cells.

03

TRCS Model of Cellular Senescence

Why do cells age? According to the TRCS model of cellular senescence, the progressive shortening of telomeres and/or rDNA arrays gives rise to a temporal concentration gradient of the tumor suppressor protein p53.

As p53 binds to the promoters and enhancers of numerous genes, the synthesis rates of ATP and proteins decline continuously over time.

Meanwhile, the expression of certain genes is specifically upregulated while that of others is specifically downregulated. This cascade drives programmed gene expression, gradually shifting cells from a youthful state to a senescent state.

Reference: https://doi.org/10.13276/j.issn.1674-8913.2021.03.003 (in Chinese)

TRCS model comparing a young cell and a senescent cell with telomere, rDNA, and p53 changes.
Figure 3. TRCS proposes that telomere DNA and/or rDNA array shortening are upstream timing events linked to p53-mediated cellular senescence.
Hourglass with sand representing a biological countdown system for cellular aging.
Figure 4. The hourglass analogy illustrates how countdown substances may function as biological timing elements.

04

Countdown Substances and the Hourglass Analogy

Interpreting the aging mechanism based on TRCS requires identifying upstream countdown substances. In cellular senescence, telomere DNA and rDNA arrays are proposed to function as countdown substances, analogous to sand in an hourglass.

As these countdown substances are consumed over time, they provide a stable biological timing signal that can be translated into downstream gene-expression changes through p53 signaling.

05

p53 as the Central Mediator of Cellular Aging

Within TRCS, p53 acts as the mediator between upstream countdown-substance dynamics and downstream cellular aging phenotypes.

All phenotypes of cellular senescence are interpreted as downstream events induced by countdown substances through p53 signaling.

A variety of factors that modulate the aging rate may affect cellular and organismal aging by regulating the consumption rate of these countdown substances.

Reference: doi: 10.14336/AD.2025.0541

Clockwork mechanism representing p53 as a mediator between upstream biological timing information and downstream aging programs.
Figure 5. p53 is interpreted as a central mediator that transmits upstream biological timing information into downstream aging programs.
Scientific diagram with p53 at the center connecting to multiple downstream aging hallmark nodes.
Figure 6. TRCS interprets the classical hallmarks of aging as downstream events mediated by p53 following telomere and rDNA array shortening.

06

Aging Hallmarks as Downstream Consequences

Under TRCS, the classical hallmarks of aging are not treated as independent primary causes of aging. Instead, they are interpreted as downstream phenotypes induced by telomere and rDNA countdown-substance shortening through p53-mediated pathways.

This interpretation provides a unified causal framework for understanding how multiple aging-associated features may emerge from upstream biological timing mechanisms.

Selected References

Current Framework

TRCS Institute Series No. 1 cover

TRCS Framework Living Preprint

2026

View Publication

Foundational Paper

Aging and Disease 2026 Causality of Aging Hallmarks first page

Aging and Disease

2025

View Publication

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