An Injectable, biodegradable magnetic hydrogel system for exogenous promotion of muscle mass and regeneration

Muscle atrophy following injury can be alleviated by periodic, lateral muscle compression via massage therapy or via periodically actuated magnetically hydrogel implants that simulate massage. Although contraction parallel to a muscle's contractile axis is well known to be superior to such lateral compression for promoting muscle strengthening in both athletic training and mechanobiology, it is not known whether this is the case for preventing muscle disuse atrophy. To test the hypothesis that axial stretch can alleviate muscle disuse atrophy, we therefore developed an injectable, biodegradable magnetic hydrogel system for exogenous promotion of muscle mass and regeneration through periodic, axial muscle stretch, and tested the system in an animal model of disuse atrophy. The system consists of a biocompatible magnetic hydrogel that can be injected into muscles and actuated to stretch muscles periodically by a wearable device. The hydrogel is durable and self-healing, and when triggered to degrade is flushed from the body over the course of two weeks. Results showed axial muscle stretch to be superior to massage-like compression in maintaining muscle mass and structure in the animal model, and suggests pathways for combatting muscle disuse atrophy during prolonged bed rest, persistent coma, and prolonged spaceflight.