Metabolic reprogramming of macrophages via engineered nanoparticles after volumetric muscle loss
Volumetric muscle loss (VML) injuries are characterized by an exacerbated and chronic inflammatory state that inhibits muscle stem-cell mediated repair, leading to fibrosis and attenuation of neuromuscular strength. The excessive infiltration of myeloid cells in VML injuries leads to the depletion of nutrients needed by myogenic progenitors for tissue repair. Mitigating the inflammatory response and fibrosis are potential approaches to enhance therapies for VML. The adenosine monophosphate-activated protein kinase (AMPK) pathway plays a critical role in myeloid responses to injury by regulating cellular metabolism, suppressing glycolysis, and attenuating fibrosis-inducing pathways such as transforming growth factor-beta (TGFß). AMPK Activation reduces fibrosis and promotes muscle stem cell differentiation, however, a limiting factor of AMPK agonists such as AICAR (5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside) is that these therapies display low bioavailability. As such, there remains an unmet need for strategies to target AMPK in skeletal muscle to enhance therapeutic efficacy and prevent muscle degeneration. To address this need, we used synthetic protein nanoparticles (SPNPs) to encapsulate AICAR. SPNPs can have high drug loading (>10wt%), allow for a sustained release of the packaged drug (72 hours), and have a demonstrated targeting capacity. Increasing the bioavailability of AICAR through packaging into SPNPs would be enabling for improving metabolism after trauma and extensible to other AMPK agonists and small molecules, which in turn can further augment existing regenerative therapies to promote healing Overall design: Quadriceps muscles from mice were given a VML injury and treated with either AICAR and Vehicle loaded SPNPs (x1011 particles) at 1,4,7 days post-injury (dpi). Muscles were collected at 8 dpi, digested into single cell suspensions, FACS sorted to obtain live cells and processed for single cell sequencing.