Extending storage of mitochondria: engineering strategies to enable clinical translation of mitochondrial transplantation

Mitochondrial transplantation can restore bioenergetic function in metabolically compromised cells and tissues, but most protocols require isolation and administration within hours. The extracellular instability of isolated mitochondria prevents conventional manufacturing, release testing, transport, banking, and on-demand clinical use. This narrative review evaluates the mechanisms of post-isolation injury and critically compares short-term storage, artificial cytosolic media, temperature modulation, cryopreservation, membrane-stabilizing sugars, lipid coatings, extracellular-vesicle-based systems, metal-organic frameworks, and vitrification concepts. Evidence is explicitly classified as direct evidence from isolated mitochondria, indirect evidence from cells or tissues, indirect evidence from whole organs or other biological systems, or engineering proposals. Published studies use heterogeneous sources, isolation methods, storage conditions, and endpoints. Membrane potential or ATP content alone is frequently treated as evidence of preservation despite incomplete assessment of coupling, ATP-synthesis capacity, uptake, therapeutic activity, safety, and manufacturing reproducibility. Extended storage is a major enabling requirement, but not the sole determinant, of clinical translation. Progress will require standardized pre-storage acceptance criteria, fresh-mitochondria comparators, multidimensional potency and stability panels, clinically meaningful shipping studies, validated product-release specifications, and in vivo demonstration that stored mitochondria retain efficacy without increased inflammatory or toxic risk.