Mechanisms of microRNA trafficking to mitochondria in the heart

MicroRNAs (miRNAs) are essential post-transcriptional regulators of gene expression, and accumulating evidence supports their presence and function within mitochondria. These mitochondrial microRNAs (MitomiRs) modulate key processes such as oxidative phosphorylation, ATP production, calcium homeostasis, and reactive oxygen species balance in cardiac tissue. Despite growing recognition of their importance, the mechanisms governing miRNA trafficking to mitochondria remain incompletely understood. This review explores the current knowledge on miRNA biogenesis, mitochondrial import pathways — including the roles of Argonaute 2 (AGO2), the Translocase of the Outer/Inner Mitochondrial Membrane (TOM/TIM) complexes, and Polynucleotide Phosphorylase (PNPase) — and the regulatory impact of specific MitomiRs, such as miR-181c, miR-210, miR-378, let-7b, and miR-1. Understanding how these molecules influence mitochondrial function provides insight into their therapeutic potential in cardiovascular disease.