Chitosan-Based Scaffolds for Stem Cell Renewal and Differentiation
Leung, Matthew Chi-hang
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Tissue engineering aims to restore function and treat disease through the fabrication of a suitable microenvironmental niche to facilitate recovery and repair. Often, a scaffold is necessary to provide the appropriate spatial, chemical, and mechanical cues in place of the native extracellular matrix. The cellular microenvironment determines cellular behavior and cell fate via contact, nutrient and waste concentration gradients, soluble signaling factors and cell-cell signaling. Thus, an effective tissue engineering scaffold must recapitulate the native extracellular microenvironment to promote the appropriate cellular behavior, and in turn, restoration of function. Chitosan-based materials are an attractive candidate for tissue engineering scaffolds on account of the inherent biocompatibility, biodegradability, availability, and range of processing techniques available. We first fabricated a porous, 3D chitosan-alginate scaffold, which we determined is an effective microenvironment for human embryonic stem cell (hESC) renewal to confluency without the use of feeder cells or conditioned media. Additionally, a technique was developed to dissolve the scaffold and recover hESCs while maintaining pluripotency. Thus, we developed an effective system for the high-density propagation of hESCs, which will be necessary for translation to future clinical applications. Subsequently, we developed an in vitro cell culture system for the myogenic induction of hESCs that integrates soluble factors with aligned chitosan-PCL fibrous ECM . In the course of this combinatorial study, it was determined that aligned chitosan-PCL fibers convey unique microenvironmental stimuli that guide cell differentiation. Finally, the aligned chitosan-PCL fibrous ECM was used to address the limitations of existing tendon grafts. Tenogenic differentiation was induced in human bone marrow stem cells more rapidly and with a greater purity than possible with current techniques. These findings demonstrate the potential use of chitosan-based materials for tissue engineering applications, and that specific microenvironmental cues can be conveyed by rational design of the scaffold to maximize the biological performance of a tissue-engineered construct.