The field of stem cell biology had its first major boon when embryonic stem cells (ESCs) were derived from a mouse blastocyst in the 1980’s. ESCs have the potential to form any type of cell in the body, and thus represent a powerful new tool to study and treat a number of diseases that plague modern society. Despite the potential advantages ESCs offer, an embryo is destroyed in the derivation process, which leads to many ethical objections. Further, ESCs are not an exact genetic match to the patient they would be put into, which may lead to problems of graft rejection like we observe with organ transplantation. In 2006, a group of scientists made a revolutionary discovery when they expanded upon the trailblazing efforts of others, who employed somatic cell nuclear transfer and transcription factor based lineage conversion, to discover that a fully differentiated cell could be driven back to an embryonic state through forced expression of four transcription factors: Oct4, Sox2, Klf4, and cMyc (OSKM). These induced pluripotent stem cells (iPSCs) can also become any type of cell in the body and are identical to ESCs in many ways, but have the advantage of being derived from the patient they would be put back into, and do not require the destruction of an embryo. iPSCs offer the ideal tool to study and treat many different diseases including. Alzheimer’s, Parkinson’s, diabetes, Huntington’s, and Huntington-Gilford Progeria Syndrome among many others. Despite the potential for iPSCs, they remain extremely hard to produce. Various reports have described “barriers to reprogramming” that inhibit the conversion of differentiated cells to iPSCs. In the chapters that follow, I present my work uncovering previously unknown barriers to iPSC reprogramming including the formation of a different stem cell type during OSKM mediated reprogramming. Further, I detail my findings that examine the impact of aging on iPSC reprogramming and my findings that cells derived from aged individuals are not rejuvenated during the iPSC reprogramming process as previously hypothesized, but instead maintain the functional defects of old cells. The work presented herein represents my efforts to uncover the mechanisms underlying OSKM reprogramming. Many previously-held conceptions about OSKM reprogramming are not supported by my findings and need to be reassessed. Further, my work should serve as the launching point for future studies aimed at improving iPSC reprogramming efficiency and quality.
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