PhD Proposal Examination – Christine Nguyen (Stewart lab)

PhD Proposal Examination

Friday April 21^st, 1:10 pm – Room CCT 2150, University of Toronto at Mississauga

Christine Nguyen (Stewart lab)

“The Characterization of the Electrophysiological Properties of Three-Dimensional Bioengineered Human Skeletal Muscle and Neuromuscular Junctions“

Abstract

Two-dimensional (2D) in vitro models of human skeletal muscle lack the architecture and contractile properties of a native muscle fiber, limiting them from being used for in vitro neuromuscular junction (NMJ) experimentation. A new method for creating three-dimensional (3D) human skeletal muscle tissues from human primary myogenic progenitors has been reported. The bioengineered muscle tissues are contractile, mimic’s clinical responses to drugs, and possess the epilson acetylcholine receptor (AChR) unit expressed in mature NMJs. Central to the communication of neurons and cells is the synapse, where transmission occurs via electrical and chemical signals between the close apposition of the pre- and post-synaptic cell membrane. At the vertebrate NMJ, acetylcholine is released from the pre-synaptic nerve terminal where it binds to AChRs on the postsynaptic muscle fiber. The flow of cations into the postsynaptic muscle cell induces a change in the membrane voltage that activates the muscle. The characterization of electrical properties of the muscle cells at rest, and when excited is crucial to advancing our understanding of the bioengineered muscles functionality. This proposed thesis will characterize the electrical properties in vitro 3D skeletal muscle tissue, and use it as the foundation for studying synaptic transmission of skeletal muscle tissues co-cultured with human pluripotent stem cell (hPSC) derived motor neurons (MN). Duchenne’s muscular dystrophy (DMD) is a fatal muscle disorder involving the skeletal muscle system. Little is known regarding the functional properties of the NMJ in DMD patients due to difficulties of in vivo experiments, and the lack of in vitro models. A new in vitro system of the NMJ will allow for further analysis in studying the integrity of skeletal muscles with regards to neuromuscular activity. Electrophysiological analyses of the model NMJ will be studied in both normal muscle cells, as well as in mutant cells with DMD.