Reprogrammed macrophages targeting MMP9 rejuvenate bone tissue in aging

Researchers have developed an mRNA engineering strategy that converts macrophages into biofactories for anti-MMP9 antibodies, directly targeting and clearing this protein known to accumulate and drive bone degeneration with age. The mechanism centers on apoptosis-mimicking lipid nanoparticles incorporating phosphatidylserine, which tricks innate immune cells into selective uptake and processing of the therapeutic RNA. In aged mice, intravenous injection reduced stem cell senescence, accelerated fracture healing, mitigated cartilage degeneration, and restored the critical osteoblast-osteoclast balance by lowering inflammatory markers (p21 and MMP3). While clinical translation remains years away, this approach represents a fundamentally different therapeutic direction for degenerative bone disorders—targeting root causes rather than symptoms—and establishes proof of concept for protein-replacement mRNA therapies in skeletal regenerative medicine, signaling where the next generation of longevity-focused orthopedic interventions may lead.