Mitochondrial Transfer and Mesenchymal Stromal Cells

Among the documented behaviors of mesenchymal stromal cells, one stands out as almost implausible until you read the primary literature: MSCs can donate their own mitochondria to injured cells, and the recipients use them.

The founding observations

In 2006, Spees and colleagues showed cells with nonfunctional mitochondria regaining aerobic respiration after co-culture with stromal cells — the organelles had moved between cells. In 2012, Islam and colleagues demonstrated the phenomenon in living lungs: marrow-derived stromal cells transferred mitochondria to injured alveolar epithelium, and the transfer itself drove the protective effect.

How it happens

The documented routes include tunneling nanotubes — transient membrane bridges between cells — and, notably for the cell-free field, extracellular vesicles, which can carry mitochondria and mitochondrial components as cargo. Transfer appears to be injury-responsive: stressed cells signal, and donor cells answer.

What it means and what it does not

Mitochondrial transfer is an active research frontier across cardiac, pulmonary, neural and musculoskeletal models. It is a documented mechanism, not an approved therapy, and no preparation should be sold on it. But it belongs in any serious account of why the MSC secretome — vesicles included — has attracted the research investment it has: the cargo list keeps proving richer than assumed.