Favorable outcome of engraftment of custom designed RADA16-I based hydrogels functionalized with SDF1 or IL4...

Although muscle regeneration capacity is remarkable, under some conditions, such as extensive muscle damage or muscular dystrophies, it may be insufficient, leading to impaired muscle repair and deficits in its structure and function. Among the treatments considered for such conditions are those combining the use of biomaterials, cells, and the addition of selected factors. In the current study we for the first time evaluated potential in vivo effects of hydrogels designed by us, based on RADA16-I hydrogel and modified with IL4 or SDF1 mimicking peptides, as well as verified whether such effects depend on the environment of skeletal muscle, i.e. acutely injured or dystrophic, i.e. chronic one. Since induced pluripotent stem cells (iPSCs) and their derivatives are considered for dysfunctional skeletal muscle therapies, we injected muscles with hydrogels only or with hydrogels and myoblasts derived from human iPSCs (hiPSCs). We found that hydrogels functionalized with SDF1 or IL4 mimicking peptides were successfully engrafted in injured muscles, and that peptide presence had a significant, supporting effect on muscle regeneration manifested by improved treadmill outcome, as well as enhanced expression of myogenesis, angiogenesis, and neurogenesis markers. In the acute injury model, these effects were elevated after co-injection of hydrogels and hiPSC-derived DMD myoblasts. An increased expression of markers of myogenesis, neurogenesis, and angiogenesis was also observed in dystrophic muscles, but only after treatment with an SDF1 functionalized hydrogel. In such an environment, transplanted cells were rapidly removed, so their injection had no influence on observed effects. The muscle environment (acute injury versus dystrophic/chronic) was crucial for the final outcome of hydrogel transplantation, injected alone or with hiPSC-derived myoblasts. This outcome was beneficial but significantly different in both models.