# Epigenetic Regulation in Cartilage Tissue

> **NIH NIH R01** · WASHINGTON UNIVERSITY · 2024 · $635,532

## Abstract

PROJECT ABSTRACT
 Osteoarthritis (OA) affects the entire joint. There is growing evidence that cartilage
catabolism and synovial inflammation are interdependent and act as primary drivers of OA. In
this competitive renewal, we build upon our findings in the first funding period, and explore the
central hypothesis that cartilage and synovium are key therapeutic targets for the protective
effect of 4-aminobutyrate aminotransferase (ABAT) loss-of-function (LOF) against OA.
 Important discoveries made during the first funding period defined completely novel
targets in the pathogenesis of OA and significantly advanced the field. We discovered that DNA
methyltransferase 3b (Dnmt3b) expression is reduced in murine and human OA chondrocytes,
and drives the disease process. In rigorous genetic mouse models, we established that Dnmt3b
LOF (loss-of function) is catabolic in chondrocytes and accelerates OA, whereas Dnmt3b GOF
(gain of function) is anabolic and protects against OA. Integrated analysis of DNA methyl-seq
and RNA-Seq identified Abat as a key downstream target of Dnmt3b. Dnmt3b was found to
methylate the Abat promoter and suppress its expression, while suppression of Dnmt3b
reduced promoter methylation and increased Abat expression, thereby establishing a reciprocal
Dnmtb3b-Abat axis in articular chondrocytes. Using lentiviral approaches, we showed that Abat
over-expression is catabolic and accelerates OA, while Abat suppression is anabolic and
protects against OA. Vigabatrin, a small-molecule inhibitor of Abat, also blocked the
development of OA and synovial inflammation in mice with knee injury. To i) definitively
establish the Dnmt3b-Abat axis in vivo in cartilage; and ii) determine if Abat LOF protects
against OA by acting on cartilage and/or synovium, we created innovative conditional Abat GOF
and LOF mice. Specific Aim 1 will use conditional Abat GOF/LOF in combination with Dnmt3b
GOF/LOF mouse models to determine whether Abat is the key downstream mediator of Dnmt3b
in regulating cartilage homeostasis. Specific Aim 2 will use tissue specific conditional gene
deletions in cartilage (Aim 2A), in synovial fibroblasts (Aim 2B), and in synovial myeloid cells
(Aim 2C) to determine if the protective effect of Abat LOF against OA is dependent on both
cartilage and synovium. Specific Aim 3 will determine whether siAbat gene therapy using a
peptide nanoparticle delivery platform confers protection against OA in mice. These findings will
definitively show that Abat is the key signal downstream of Dnmt3b, define the relative role of
Abat on cartilage and synovium in protection against OA and pain, and establish delivery of
siAbat nanoparticles as a novel translational approach for the treatment of OA and joint pain.

## Key facts

- **NIH application ID:** 10882613
- **Project number:** 2R01AR069605-06A1
- **Recipient organization:** WASHINGTON UNIVERSITY
- **Principal Investigator:** Regis J O'Keefe
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $635,532
- **Award type:** 2
- **Project period:** 2016-03-01 → 2029-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10882613

## Citation

> US National Institutes of Health, RePORTER application 10882613, Epigenetic Regulation in Cartilage Tissue (2R01AR069605-06A1). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10882613. Licensed CC0.

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