Human In Vitro Models of Pediatric Muscular Diseases

Abstract

The development of new therapies for pediatric diseases over the past few decades has been hampered by a lack of human-relevant model systems and inherent challenges with pediatric clinical trials. In particular, many diseases of childhood are rare genetic diseases that limit clinical trial utility due to small patient populations. Recent advances in stem cell, gene editing, and organ on chip technologies present a unique opportunity to develop in vitro analogs of pediatric patients that can potentially expedite drug screening and development. Here, we review the spatiotemporal scales of muscular diseases of childhood in order to specify the design criteria of in vitro disease models requisite for recapitulation of diseased muscle structure and function. Moreover, we review advances in the development of induced pluripotent stem cell-derived muscle, gene editing, as well as approaches to mimic diseased microenvironments in vitro. Next, we present an in vitro model of allergic asthma developed using human cells. We replicated the laminar, anisotropic structure of the human airway musculature through microcontact printing of extracellular matrix protein cues. To mimic the inflammation critical for driving airway dysfunction, we treated the engineered airway smooth muscle tissues with interleukin-13, a known mediator of asthma. We tested our system by replicating the cholinergic challenge, used clinically to diagnose asthma, in vitro. We found that interleukin-13 promoted hypercontractility in the engineered airway smooth muscle, but even hypercontractions could be reversed using standard airway drugs, an important hallmark that distinguishes asthma from other obstructive diseases of the airway. Furthermore, we observed that interleukin-13 promoted greater cell spreading, increased alignment of the actin cytoskeleton, and upregulation of RhoA. As a proof of principle, we targeted the RhoA-ROCK pathway and demonstrated ROCK inhibition could both prevent hypercontractions and improve airway smooth muscle relaxation beyond existing therapies. Lastly, we present a model Duchenne muscular dystrophy (DMD), the most common childhood-lethal genetic disease. Specifically, we sought to recapitulate the impaired muscular repair and contractile weakness of DMD skeletal muscle. We found that myoblasts, a muscle stem cell, from DMD patients failed to align and polarize with respect to the extracellular matrix cues, resulting in poorer muscle formation and maturation. These deficits in muscle formation were reflected by profound contractile weakness in these tissues, as observed in quantitative muscle testing performed clinically. Collectively, these human-derived in vitro diseases models represent substantial progress towards the ultimate goal of replacing animal models with human-based models in preclinical trials.