# Role of DNA damage and cellular senescence in osteoarthritis pathophysiology

> **NIH NIH R01** · UNIV OF NORTH CAROLINA CHAPEL HILL · 2024 · $630,255

## Abstract

PROJECT SUMMARY
 A key priority for the NIH is to limit disability caused by osteoarthritis (OA) and other chronic diseases that
emerge with age. Senescent cells within joint tissues contribute to OA, but there is a knowledge gap regarding
the triggers by which decades of aging initiate cellular senescence. One key mediator of senescence in other
contexts is persistent DNA damage and the subsequent activation of a set of signaling pathways known as the
DNA damage response (DDR). The DDR can drive the production of inflammatory and matrix-degrading
molecules collectively known as the senescence-associated secretory phenotype (SASP), which has strong
overlap with catabolic molecules known to contribute to OA. As demonstrated through the use of a single-cell
gel electrophoresis “comet” assay, chondrocytes accumulate significant levels of DNA damage throughout aging
and during OA. This damage is mostly in the form of single-strand breaks (SSBs) but a subset of cells also
harbor double-strand breaks (DSBs). These distinct forms of damage can be initiated in cells from young
cadaveric donors and mice to mimic the levels found in older donors/mice, with methyl methanesulfonate (MMS)
for SSBs, ellipticine for DSBs, and irradiation to generate both SSBs and DSBs. Conversely, the burden of DNA
damage in older cadaveric donors and older mice can be reduced by boosting DNA repair with activation of
Sirtuin 6 (SIRT6) using the small molecule MDL-800. The long-term goal of this work is to catalyze more effective
treatments for OA by determining the mechanisms by which joint cells become senescent. The central
hypothesis is that the accumulation of DNA damage in joint tissues plays a causal role in driving senescence,
the SASP, and subsequent OA. The first aim is to establish the contribution of SSBs and DSBs to senescence
by applying distinct forms of DNA damage (irradiation, MMS, ellipticine) to cadaveric human chondrocytes and
synovial cells. The second aim is to determine the extent to which DNA damage drives senescence and OA in
mice. We also use intra-articular injection of agents to increase damage (MMS or ellipticine) or decrease damage
(MDL-800) in the joints of p16tdTom reporter mice to assess senescence and functional/histologic OA. The third
aim is to define the protein signatures that contribute to progression towards the SASP using a multiplex antibody
staining method known as iterative indirect immunofluorescence imaging (4i) to track the signaling pathways that
are activated in response to DNA damage. The expected outcomes of this work include a better understanding
of the types of DNA damage that lead to senescence in joint tissues and the signaling pathways that link the
DDR to SASP. This work is innovative in that tailored interventions are employed to alter the levels of DNA
damage, with sophisticated readouts of senescence, including 4i for assessing protein signatures and
senescence reporter mice. These contributions are expected to have a...

## Key facts

- **NIH application ID:** 10932966
- **Project number:** 5R01AG081734-02
- **Recipient organization:** UNIV OF NORTH CAROLINA CHAPEL HILL
- **Principal Investigator:** Brian O Diekman
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $630,255
- **Award type:** 5
- **Project period:** 2023-09-30 → 2028-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10932966

## Citation

> US National Institutes of Health, RePORTER application 10932966, Role of DNA damage and cellular senescence in osteoarthritis pathophysiology (5R01AG081734-02). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10932966. Licensed CC0.

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