Diseased states in amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) are characterized by the loss of specific motor neuron subtypes and cell replacement therapy has been proposed as a potential treatment. However intraspinal transplantation of embryonic stem cell-derived motor neurons (ESMN), which represent an essentially unlimited source of replacement cells, into the adult spinal cord generally yields poor outcomes with respect to integration into neural circuits and axon extension. It is feasible that developing a carrier for the transplanted ESMNs that incorporates neurotrophins, axon guidance cues, and extracellular matrix (ECM) components could improve outcomes and represent a general strategy for CNS repair by promoting cell viability and directing axon outgrowth into the musculature. I plan on taking advantage of the bioorthogonality of click chemistry and the robustness of the ESMN differentiation to define an optimal synthetic niche that permits the survival and robust axonal in synthetic PEG-peptide hydrogels. After engineering the hydrogel composition that enables the maximum cell viability and axon outgrowth, I will control the spatial presentation of ECM components, axon guidance cues, and neurotrophins using two-photon confocal microscopy and established photochemistries to direct axon outgrowth. These advances will provide novel insights into the minimal molecular requirements for axon outgrowth and will be combined with the optimized hydrogel to develop an ESMN transplantation platform that will be validated in the spinal cord of chick embryos.
D.D. McKinnon, A.M Kloxin, and K.S. Anseth, "Synthetic hydrogel platform for three-dimensional culture of embryonic stem cell-derived motor neurons," Biomaterials Science (2013).
Compressed Z-stack of ESMNs extending axons through a PEG hydrogel