Current manufacturing standards for stem cell therapies may be missing a critical flaw: damaged proteins in donor cells. A new review argues that as stem cells expand in the lab, they accumulate senescent cells that can package defective proteins into extracellular vesicles — potentially transmitting harm to patients. Researchers are calling for proteostatic fitness to become a mandatory release criterion before therapies reach the clinic.
When stem cell therapies pass today's quality checks — identity, viability, sterility, genetic stability — they're considered ready for patients. But a new review from researchers at the University of Manitoba and Zhujiang Hospital of Southern Medical University says those checks are missing something important: the protein health of donor cells.
The problem starts during ex vivo expansion, when stem cells are grown in the lab before transplantation. This process drives cellular senescence — a state where cells stop dividing but release inflammatory signals and accumulate misfolded or damaged proteins. Critically, these defects can be packaged into extracellular vesicles (EVs) and transferred to recipient cells, potentially triggering mitochondrial dysfunction and secondary senescence in patients.
Key Takeaways:
Why it matters: Stem cell therapies hold promise for conditions like ALS, graft-versus-host disease, and cardiac repair — but if proteostatic defects go undetected, treatments could inadvertently harm patients. The authors urge the field to add senescence screening and EV cargo profiling as standard release criteria before these therapies scale up.
