Unlocking Therapeutic Potential: Harnessing Extracellular Vesicles and miRNAs to Combat Muscle Wasting Disorders

Approximately 40% of the human body’s mass is comprised of skeletal muscle, making it the largest organ in the human body. These muscles play a crucial role in providing stability, supporting movement, and maintaining the integrity of internal organs. Importantly, skeletal muscles possess the inherent ability to grow and regenerate, whether in response to injury or as a result of physiological conditions such as exercise. This study explores the intrinsic regenerative capabilities of skeletal muscle and their potential application in addressing chronic muscle illnesses, muscle wasting associated with aging, and specific neuromuscular pathologies like Duchenne muscular dystrophy (DMD). There is presently no cure for such muscle wasting conditions, but a potential solution involves utilizing stem cell therapy. Nevertheless, before therapeutic applications can be considered viable, challenges like limited accessibility, regulation of cell destiny, and paracrine effects on the host tissue must be tackled. Therefore, current research is focusing more on the potential of cell-free therapeutics, including the abundance of extracellular vesicles (EVs) and their cargo in the skeletal muscle niche. Our research focuses on EVs, which include exosomes, microvesicles, and apoptotic bodies, which play a crucial role in intercellular communication. We identify key microRNAs (miRNAs/miRs) within the EVs that could serve as therapeutic targets, as well as utilize EVs as delivery vehicles.

In the first aspect of our research, we analyzed the content of extracellular vesicles derived from animal models with muscle hypertrophy and wasting due to a chronic disease and aging. Through transcriptome, protein cargo, and miRNA analysis, we identified a hypertrophic miRNA signature, including miR-1 and miR-208a, with potential applications in mitigating muscle wasting. In vitro experiments using mesoangioblasts (MABs), adult stem cells associated with blood vessels, showed an increased efficiency in myogenic differentiation when exposed to this signature. Furthermore, we administered these miRNA-treated MABs into the leg muscles of immunodeficient mice undergoing muscle injury and age-related deterioration, resulting in improved muscle weight and cross-sectional area. Our findings demonstrate that miRNAs originating from EVs replicate the muscle-enhancing effects observed in a mouse model of muscle hypertrophy.

In the second part of our study, we focused on using small EVs (<200 nm) as delivery vehicles for potent molecules, particularly miRNAs, to address muscle-related pathologies, specifically muscular dystrophy. We identified a novel pro-myogenic miRNA cocktail (miRNA-146b and miRNA-212) and tested its efficacy on myoblasts, including those derived from DMD and isogenic control induced pluripotent stem cells (iPSCs). Furthermore, we explored the use of EVs as delivery vehicles for these miRNAs, with comparisons indicating superior efficiency over synthetic nanoparticles. Our study also ventures into in vivo applications, demonstrating successful delivery of the pro-myogenic miRNA combination to the hindlimb muscles of immunodeficient β-sarcoglycan-null mice using custom-engineered EVs. Additionally, we expanded our investigations into three-dimensional (3D) cell culture, employing iPSC-derived skeletal muscle spheroids to better replicate real tissue conditions.

Overall, this research sheds light on the therapeutic potential of extracellular vesicles and their miRNA cargo in promoting muscle regeneration. The identified miRNA signatures, delivery mechanisms using EVs, and insights from 3D cell culture models collectively contribute to advancing cell-free therapeutics for various muscle-related pathologies.