Intercellular Mitochondrial Transfer: Implications in Cardiovascular Health.

Mitochondria are important organelles for metabolic homeostasis, cell fate, and survival. Emerging evidence suggests that mitochondria are not confined to the cells. Intercellular mitochondrial transfer (IMT) is increasingly recognized between a variety of cells, including major cell types in the cardiovascular system. Observations made by coculture systems, genetic lineage-tracing approaches, and animal models indicate that mitochondria can be transferred between cardiomyocytes, fibroblasts, endothelial cells, vascular smooth muscle cells, cardiac macrophages, and mesenchymal stromal cells. IMT has also been reported between a remote organ, for example, adipose tissue, and the heart, suggesting that mitochondrial trafficking can mediate communications not only between individual cells but also across organs. Two principal modes of IMT are reported. One involves directed, contact-dependent trafficking of mitochondria through membranous contacts or nanotubes. The other relies on the release of mitochondria, either packaged in membrane-bound vesicles or as free mitochondria, into the extracellular space followed by import into the acceptor cells. Consequences of IMT can be beneficial or detrimental depending on the cell type and the conditions under which the IMT occurs. Mechanisms underlying the transfer or its consequences are not fully understood, however. The role of IMT in cardiovascular health is, therefore, interpreted with certain assumptions. In this review, we first summarize the evidence of IMT in the cardiovascular system and the observed functional outcome. We then aim to identify the knowledge gaps and critical questions to be addressed, followed by a discussion of challenges and opportunities to advance the field.