Opantimirs: A class of antagonizing microRNAs that upregulate Opa1 and improve mitochondrial and disuse myopathies.

Alterations in mitochondrial ultrastructure and reduced levels of the crista-shaping protein Opa1 are key features of mitochondrial myopathies and aging. We identify and characterize a biological therapy that improves mitochondrial and disuse myopathy models by boosting Opa1 levels. In silico analysis identifies microRNAs (miRNAs) 128-3p and 148/152-3p family as conserved modulators of OPA1 transcription and elevated in various muscle disorders. These miRNAs target the 3' UTR of murine and human OPA1, reducing its mRNA and protein levels, causing mitochondrial fragmentation and crista disorganization. Genetic experiments confirm that their mitochondrial effects rely on 3' UTR binding. In mitochondrial disease patient cells and murine models, elevated OPA1-specific miRNA levels are reduced by antagonistic miRNAs (Opantimirs), which restore mitochondrial ultrastructure, morphology, and function. In vivo, Opantimirs correct mitochondrial ultrastructure and fiber size in muscles of denervated and Cox15-ablated mice, improving strength in the latter. Thus, biopharmacological correction of the mitochondrial ultrastructure can ameliorate mitochondrial myopathies.