Bioengineering approaches to promote maturity in human skeletal muscle constructs.

Abstract

During ageing, cellular changes impairing normal responses to contractile activity causes our skeletal muscles to atrophy and weaken. Additionally, reduced innervation quality in muscle of older individuals results in denervation atrophy. This declining muscle mass and strength, termed sarcopenia, contributes to frailty and loss of independence in older populations. In order to study sarcopenia pathophysiology, there is a requirement for physiologically relevant in vitro models of mature human skeletal muscle which display neuromuscular junction (NMJ) formation. Recently, the MicroAge project, a UK Space Agency funded mission to the International Space Station, used microgravity to model accelerated musculoskeletal ageing of muscle constructs consisting of human skeletal muscle cells grown in 3D within a hydrogel. This current project aims to explore several bioengineering approaches to promote maturity of these constructs, developing a model of mature human skeletal muscle. The MicroAge constructs will first be characterised against a panel of maturation indices for skeletal muscle, including fibre typing and genetic markers of maturity. Development of a system to simultaneously measure force generation and impedance spectroscopy will evaluate how well impedance spectroscopy monitors tissue maturity as well as being a proxy for force generation during contractions. Subsequently, we aim to implement bioprinting to streamline construct formation, and investigate effects of varying patterns of electrical stimulation on maturity throughout construct differentiation. The longer-term aim is to develop an in vitro NMJ model through innervation of constructs by co-culture with human induced pluripotent stem cells differentiated into neuronal stem cells. Effects of these approaches on construct maturity will be measured by changes to the panel of maturation indices and contractile properties, determining the extent of maturity that can be achieved by human muscle constructs in vitro and producing a platform for screening therapeutic interventions targeting sarcopenia.