Protein Transduction Domain-Mediated Delivery of Recombinant Proteins and In Vitro Transcribed mRNAs for Protein Replacement Therapy of Human Severe Genetic Mitochondrial Disorders: The Case of Sco2 Deficiency

• Published in: Pharmaceutics Vol. 15; no. 1; p. 286
• Main Authors: Miliotou, Androulla N, Foltopoulou, Parthena F, Ingendoh-Tsakmakidis, Alexandra, Tsiftsoglou, Asterios S, Vizirianakis, Ioannis S, Pappas, Ioannis S, Papadopoulou, Lefkothea C
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 14.01.2023; MDPI
• Subjects: Adenosine; Alzheimer's disease; Cytochrome; Energy; Fatty acids; Genetic disorders; in vitro transcribed mRNA (IVT-mRNA); Metabolism; Mitochondria; mitochondrial disorders; Mitochondrial DNA; Nervous system; Oxidation; Peptides; Phosphorylation; protein replacement therapy; protein transduction domain technology; Proteins; recombinant proteins; Review; Sco2; protein transduction domain technology; recombinant proteins; Sco2; in vitro transcribed mRNA (IVT-mRNA); mitochondrial disorders; protein replacement therapy
• ISSN: 1999-4923; 1999-4923
• DOI: 10.3390/pharmaceutics15010286

Mitochondrial disorders represent a heterogeneous group of genetic disorders with variations in severity and clinical outcomes, mostly characterized by respiratory chain dysfunction and abnormal mitochondrial function. More specifically, mutations in the human gene, encoding the mitochondrial inner membrane Sco2 cytochrome oxidase (COX) assembly protein, have been implicated in the mitochondrial disorder fatal infantile cardioencephalomyopathy with COX deficiency. Since an effective treatment is still missing, a protein replacement therapy (PRT) was explored using protein transduction domain (PTD) technology. Therefore, the human recombinant full-length mitochondrial protein Sco2, fused to TAT peptide (a common PTD), was produced (fusion Sco2 protein) and successfully transduced into fibroblasts derived from a /COX-deficient patient. This PRT contributed to effective COX assembly and partial recovery of COX activity. In mice, radiolabeled fusion Sco2 protein was biodistributed in the peripheral tissues of mice and successfully delivered into their mitochondria. Complementary to that, an mRNA-based therapeutic approach has been more recently considered as an innovative treatment option. In particular, a patented, novel PTD-mediated IVT-mRNA delivery platform was developed and applied in recent research efforts. PTD-IVT-mRNA of full-length was successfully transduced into the fibroblasts derived from a /COX-deficient patient, translated in host ribosomes into a nascent chain of human Sco2, imported into mitochondria, and processed to the mature protein. Consequently, the recovery of reduced COX activity was achieved, thus suggesting the potential of this mRNA-based technology for clinical translation as a PRT for metabolic/genetic disorders. In this review, such research efforts will be comprehensibly presented and discussed to elaborate their potential in clinical application and therapeutic usefulness.