Rethinking Mitochondria: The Extracellular Dimension

Mitochondria are essential organelles that transform the energy contained in metabolic substrates into ATP while supporting numerous cellular processes. Traditionally regarded as strictly intracellular, growing evidence now demonstrates that mitochondria and mitochondria-derived components can also be released into the extracellular space, giving rise to extracellular mitochondria. extracellular mitochondria display remarkable heterogeneity, ranging from intact organelles to individual molecular components, free to vesicle-encapsulated structures, and with functional states spanning from severely damaged to metabolically active. Their release is mediated by tightly regulated mechanisms in both living and dying cells, and is influenced by cellular stress, activation state, and pathways that control mitochondrial selection, compartmentalization, trafficking, and extrusion. Extracellular release fulfills multiple functions across the organism, including quality control, modulation of cellular identity, inflammatory signaling, and functional support of recipient cells. In the cardiovascular system, extracellular mitochondria contribute to both homeostasis and disease progression. This review summarizes current knowledge of extracellular mitochondria forms, mechanisms of release, and pathophysiological relevance, and highlights their emerging potential as therapeutic targets in cardiovascular pathophysiology and beyond.