Postdoctoral fellow / Dr UCLA, California, United States
Abstract: Volumetric muscle loss (VML) injuries occur due to orthopedic trauma or the surgical removal of skeletal muscle (SkM) and results in irreversible damage in muscle structure and function due to the loss of a significant portion of SkM. Current clinical options to treat VML are inefficient, as recent advances in tissue engineered SkM offer a potential solution to address lost or damaged muscle tissue but are limited by donor availability and issues associated with immune incompatibility. The use of human induced pluripotent stem cells (hiPSCs) derived SkM is extremely promising for the treatment of VML due to their ability to generate personalized muscle cells in a dish. However, the Pyle lab has shown that currently available protocols for generating hiPSC muscle progenitors (SMPCs) are limited to modeling the embryonic stage of development. We hypothesized that introducing endothelial cells in our established protocol, allowing the co-differentiation of hPSCs into innervated muscle fibers, would enhance the proliferation and the maturity of the SMPCs. To optimize our model, we induced the co-differentiation of the lateral mesoderm along the paraxial mesoderm and the neuroectoderm and then induced the differentiation and proliferation of endothelial cells. After 60 days of differentiation, as shown by immunofluorescence, we obtained vascularized millimeter long fetal muscle bundles innervated by motor neurons capable of repeated contractions and surrounded by a high number of SMPCs. Our snRNAseq analysis, as well as the fusion index of the sorted SMPCs, suggests that the presence of endothelial cells increases the proliferation and enhance the maturity of our SMPCs aligning with our data of fetal in vivo SMPCs. Finally, the engraftment of sorted CD82+/NCAM SMPCs into NSG-mdx mice resulted in the formation of hundreds of dystrophin+ muscle fibers demonstrating the high proliferation and fusion capacity of our SMPCs in vivo. The Pyle lab has shown that fetal SMPCs can better regenerate skeletal muscle compared to embryonic SMPCs and our ongoing studies are evaluating SMPCs and endothelial cells in mouse models of VML for future use in a cell-based therapy for treatment of VML injuries.
Funding Source: Kilian Mazaleyrat acknowledges the support of the UCLA Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research Training Program for resources, mentorship, and funding.
