MRI detection of senescent cells in porcine knee joints with a β-galactosidase responsive Gd-chelate.

Senescent cells promote osteoarthritis progression through the secretion of inflammatory mediators. Preclinical studies have identified senescence-associated beta-galactosidase (β-gal) as a biomarker of senescence, but in vivo detection remains challenging. Here, we evaluated whether a β-gal responsive gadolinium (Gd) chelate can non-invasively detect β-gal expressing senescent cells with standard clinical magnetic resonance imaging (MRI) technology in vitro, ex vivo, and in vivo in porcine joints. In vitro studies showed that senescent mesenchymal stromal cells (MSCs) exhibited significant MRI signal enhancement upon incubation with the β-gal responsive Gd-chelate compared to viable control cells. In vivo, intraarticular injection of the probe into pig knee joints revealed its retention and activation by senescent cells in cartilage defects, evidenced by a significant increase in R (1) relaxation rate. MRI-based senescent cell detection holds promise for identifying patients amenable to senolytic therapies, tailoring treatment plans, and monitoring therapy response in real-time.