UC San Diego

Tissue engineered therapies have demonstrated promise for multiple injuries and diseases that in particular affect muscle. Over the last decade, many groups have shown that these therapies could provide an alternate avenue for biological therapies that obviate the need for systemic drugs, invasive procedures, and repeated treatments. In particular, cell therapy has shown much promise in repairing damaged muscle tissue. This has mainly been exemplified in damaged cardiac tissue but more recently has been used to treat skeletal muscle ailments such as peripheral artery disease (PAD). PAD effects over 27 million people in Europe and North America alone. This chronic disease is typically caused by an atherosclerosis of the leg, decreasing blood flow, and leading to eventual muscle atrophy. This can cause extreme pain at rest and could lead to amputation. Skeletal myoblast cell therapy has been shown to be a promising therapy by increasing blood vessel formation by paracrine signaling and repairing damaged muscle by engraftment into host tissue. However, few of these cells upon injection stay viable and localized to the site of delivery. The inability to administer, remain viable, and engraft efficiently has led scientists to explore alternative ways to deliver these cells. In this thesis, we examine the behavior of myoblasts in response to fibroblasts via a state-of-the- art co-culture device in vitro. Next, we make the system more physiologically relevant by adding a substrate that can be tuned to a specific stiffness. Then we utilize previous co-culture findings and implement them into a decellularized skeletal muscle matrix hydrogel (SkECM) that can be easily injected in vivo. We show that combining both myoblasts and fibroblasts in the SkECM improves myoblast differentiation and metabolic activity when cultured in 3D. We also show that the SkECM and fibroblasts promote myoblast engraftment in muscle tissue compared to injections in saline. Lastly, we demonstrate an increase in blood perfusion in ischemic limbs when myoblasts are injected with SkECM. This work provides a way to study myoblast differentiation and viability in vitro and a delivery system that improves on the current method used in clinical trials for PAD treatment