Endothelin-1/endothelin B receptor signalling mediates Prx1+ skeletal stem cells senescence: A driver of osteoporotic bone loss

Abstract

Background

Stem cells residing in the perivascular niche are critical for skeletal homeostasis. Vascular endothelin-1 (ET-1) controls stem cell fate in development, but its role in the exhaustion of skeletal stem cells (SSCs) and subsequent bone degeneration in osteoporosis remains poorly understood. This study aimed to determine whether ET-1 signalling drives SSCs senescence and to elucidate the underlying mechanisms.

Methods

We utilised a combination of human single-cell RNA sequencing datasets, murine models of ageing and ovariectomy (OVX), and an endothelial-specific ET-1 overexpression transgenic (TET-1) mouse model. In vitro studies on mesenchymal stem cells (MSCs) employed ET-1 challenge with and without receptor-specific antagonists (BQ123 for ET_AR, BQ788 for ET_BR). The mechanism was further probed using transcriptomic profiling and validated in vivo through Prx1⁺ SSCs-specific ET_BR knockout (Prx1-Cre;ET_BR^fl/fl) and pharmacological inhibition with the ET_BR antagonist BQ788.

Results

In aged and OVX mice, ET_BR expression was significantly upregulated in SSCs concurrent with bone loss. Transgenic ET-1 overexpression recapitulated an aged bone phenotype, inducing SSCs senescence and accelerating bone loss. In vitro, ET-1 triggered MSCs senescence and reactive oxygen species (ROS) accumulation. Such effects were specifically abrogated by ET_BR, but not ET_AR. Transcriptomic analysis revealed that ET-1/ET_BR signalling synergistically dysregulates the PI3K-AKT and p53 pathways to orchestrate senescence. Critically, both genetic knockout of ET_BR in Prx1⁺ SSCs and pharmacological inhibition with BQ788 mitigated oxidative stress, reduced cellular senescence, and preserved bone mass in OVX and aged mice.

Conclusion

This study identified the ET-1/ET_BR signalling axis as a critical driver of osteoporosis by promoting ROS-mediated SSCs senescence. We established a link between vascular ageing and skeletal decline.

The translational potential of this article

This study positioned ET_BR blockade as a promising novel therapeutic strategy for osteoporosis. By targeting the upstream driver of SSCs exhaustion, ET_BR inhibition offers a potential paradigm shift from palliative care to proactive rejuvenation of the osteogenic niche. This approach could counteract both postmenopausal and age-related bone loss by restoring the bone-forming potential of the skeleton, addressing a significant unmet clinical need.