Tolloid protease-mediated regulation of GDF11 in the pathogenesis of atrial fibrosis

The National Heart Lung and Blood Institute awarded President and Fellows of Harvard College $151,040 on February 5, 2026, under the Cardiovascular Diseases Research program (CFDA 93.837) to investigate the role of TOLLOID proteases in atrial fibrosis and atrial fibrillation pathogenesis.

The research uses gene-edited mouse models, both with and without surgically induced atrial fibrosis, to examine how TOLLOID protease-mediated cleavage of Growth Differentiation Factor 11 (GDF11) regulates cardiac fibrosis. GDF11, a member of the TGF-beta superfamily, exhibits anti-fibrotic properties in the heart and represents a therapeutic target for atrial fibrillation, the most common cardiac arrhythmia. Prior work from the recipient's laboratory established methods to differentiate GDF11 from its homolog GDF8 and demonstrated that aptamer-based detection of cleaved GDF11/GDF8 mature domains robustly predicted atrial fibrillation in at-risk patients. Unpublished single-nuclei data from the lab revealed reduced TOLLOID transcript expression in left atrial appendages of atrial fibrillation patients. Exogenous administration of TOLLOID-cleaved GDF11 significantly reduced cardiac fibrosis in preclinical models, supporting TOLLOID protease activity as a vital mechanism in atrial fibrosis pathogenesis.

Performance occurs in Massachusetts. The period of performance extends through November 30, 2028. The award is classified as a Project Grant, an assistance type under the Cardiovascular Diseases Research program.

Abstract

Atrial fibrillation (AF) is the most common cardiac arrhythmia, significantly increasing the risk of myocardial infarction, stroke, and heart failure. Despite its widespread impact, the mechanisms underlying AF remain incompletely understood. A key driver of AF is atrial fibrosis, which alters the heart's structure and disrupts electrical signaling, creating a substrate for arrhythmia initiation and progression. Effective prevention and management of AF, therefore, requires targeted strategies to address fibrosis. Growth differentiation factor 11 (GDF11), a TGF-β superfamily member, has shown anti-fibrotic properties in the heart, distinguishing IT as a promising therapeutic target. Although GDF11 shares ~90% sequence homology with its counterpart GDF8, their biochemical functions are distinct. Recent work from our lab has established methods to reliably differentiate these ligands and highlighted their unique roles in cardiac health. While circulating levels of GDF11 and GDF8 measured by mass spectrometry show no correlation with cardiovascular disease, aptamer- based dual detection of GDF11/8 cleaved mature domains has robustly predicted AF in at-risk patients. The activation of GDF11 requires cleavage of its inhibitory prodomain by tolloid (TLD) proteases, a critical step in enhancing its biological activity. Notably, unpublished single-nuclei data from our lab reveals reduced TLD transcript expression in the left atrial appendages of AF patients. Moreover, exogenous administration of TLD- cleaved GDF11 significantly reduces cardiac fibrosis in preclinical models, underscoring TLD protease activity as a vital mechanism in atrial fibrosis and AF pathogenesis. This proposal aims to investigate the role of TLD proteases in experimental atrial fibrosis through the use of gene-edited mouse models, both with and without surgically induced atrial fibrosis. Additionally, the study will explore the therapeutic potential of exogenous, prodomain-cleaved GDF11. By elucidating the molecular mechanisms linking TLD proteases and atrial fibrosis, this research seeks to advance our understanding of AF pathogenesis and identify novel therapeutic approaches for its treatment.