Part I - A Microfluidic Method for the Selection of Undifferentiated Human Embryonic Stem Cells and in Situ Analysis
Conventional cell-sorting methods such as FACS or MACS can suffer from certain shortcomings such as lengthy sample preparation time, cell modification through antibody labeling, and exposure to high shear forces or metallic microparticles. In light of these drawbacks, we have recently developed a novel, label-free, microfluidic platform that can not only sort cells with minimal sample preparation but also enable analysis of cells in situ. In contrast to MACS or FACS, cells sorted by our method have very high viability (~90%). In this part of my thesis, I first describe existing antibody-functionalized microfluidic devices for cell sorting as well those designed for human embryonic stem cell (hESC) sorting. I then demonstrate the utility of our platform to sort undifferentiated human embryonic stem cells (hESCs) from a heterogeneous population, achieving ~60% average purity of the cells expressing a marker of interest. I also discuss future strategies to improve sorting efficiency. Overall, our platform technology could be applied to other cell types beyond hESCs and to a variety of heterogeneous cell populations.
Part II - Attenuation of TGF-β Signaling via Incorporation of a Dominant-negative TGF-β Type II Receptor Promotes Improved Muscle Regeneration in Murine Skeletal Myoblasts
Skeletal muscle stem cells known as satellite cells are responsible for muscle regeneration. Upon muscle injury or exercise, quiescent satellite cells become activated, proliferate as myogenic precursors, differentiate into myoblasts, and ultimately fuse into new, multinucleated myofibers. Unfortunately, this paradigm breaks down with aging and multiple factors contribute to a build-up of scar tissue instead of new muscle. Among these negative contributors are some members of the TGF-β family of signaling molecules. After an introduction to muscle regeneration and satellite cells, the adult skeletal muscle stem cells, I will discuss how biomaterials can help improve muscle regeneration and recent advances in combating TGF-β-induced impairment in muscle repair. I will then discuss the work I have done in improving skeletal muscle repair by attenuating the effects of TGF-β signaling via incorporation of a dominant-negative TGF-β type II receptor.