Cardiovascular disease (CVD) remains the leading cause of mortality, resulting in 1 out of 4 deaths in the United States at the alarming rate of 1 death every 36 seconds, despite great efforts in ongoing research. In vitro research to study CVDs has had limited success, due to lack of biomimicry and structural complexity of 2D models. As such, there is a critical need to develop a 3D, biomimetic human cardiac tissue within precisely engineered in vitro platforms. This PhD dissertation involved development of an innovative anisotropic 3D human stem cell-derived cardiac tissue on-a-chip model (i.e., heart on-a-chip), with an enhanced maturation tissue state, as demonstrated through extensive biological assessments. To demonstrate the potential of the platform to study cardiac-specific diseases, the developed heart on-a-chip was used to model myocardial infarction (MI) due to exposure to hypoxia. The successful induction of MI on-a-chip (heart attack-on-a-chip) was evidenced through fibrotic tissue response, contractile dysregulation, and transcriptomic regulation of key pathways.This dissertation also described incorporation of CRISPR/Cas9 gene-editing to create a human induced pluripotent stem cell line (hiPSC) with a mutation in KCNH2, the gene implicated in Long QT Syndrome Type 2 (LQTS2). This novel stem cell line, combined with the developed heart on-a-chip technology, led to creation of a 3D human cardiac on-chip tissue model of LQTS2 disease.. Extensive mechanistic biological and electrophysiological characterizations were performed to elucidate the mechanism of R531W mutation in KCNH2, significantly adding to existing knowledge about LQTS2. In summary, this thesis described creation of a LQTS2 cardiac on-a-chip model, incorporated with gene-edited hiPSC-cardiomyocytes and hiPSC-cardiac fibroblasts, to study mechanisms of LQTS2. Overall, this dissertation provides broad impact for fundamental studies toward cardiac biological studies as well as drug screening applications. Specifically, the developed heart on-a-chip from this dissertation provides a unique alternative platform to animal testing and 2D studies that recapitulates the human myocardium, with capabilities to model critical CVDs to study disease mechanisms, and/or ultimately lead to development of future therapeutic strategies.

The CRISPR/Cas9 gene-editing tool is currently in clinical trials as the excitement about its therapeutic potential is exponentially growing. However, many of the developed CRISPR based genome engineering methods cannot be broadly translated in clinical settings due to their unintended consequences. These consequences, such as immune reactions to CRISPR, immunogenic adverse events following receiving of adeno-associated virus (AAV) as one of the clinically relevant delivery agents, and CRISPR off-target activity in the genome, reinforces the necessity for improving the safety of CRISPR and the gene therapy vehicles. Research into designing more advanced CRISPR systems will allow for the increased ability of editing efficiency and safety for human applications. This work 1- develops strategies for decreasing the immunogenicity of CRISPR/Cas9 system components and improving the safety of CRISPR-based gene therapies for human subjects, 2- demonstrates the utility of this system in vivo for transient repression of components of innate and adaptive immunity, and 3- examines an inducible all-in-one CRISPR-based control switch to pave the way for controllable CRISPR-based therapies.

The process of spermatogenesis, the differentiation of sperm stem cells into spermatozoa, produces a diverse array of descendent cells which express varied morphological and genetic traits throughout their maturation. Beginning with primordial germ cells, these sperm progenitors experience twelve stages of differentiation before maturation into their final stage. During their differentiation, these cells reside in the seminiferous tubules within the testes. These tubules are surrounded by somatic cells, primarily Sertoli, Leydig, myoid, and epithelial cells. These cells provide the germ cells with necessary signaling proteins for their progression as well as protection from exterior toxins through the formation of the blood-testis barrier (BTB). However, their close association with germ cells makes extracting these sperm progenitors difficult. Here, I convey the results for an initial trial of harvesting germ cells from two mice. Due to inconclusive qRT-PCR amplification data from the first experiment, future iterations of this harvest will explore other previously published methods. These will include Magnetic-Activated Cell Sorting which will target individual sperm progenitor populations using cell-surface receptors such as GFRα-1 and THY1 to obtain sperm stem cells. Additionally, Fluorescence-Activated Cell Sorting may be useful for obtaining multiple groups of meiotic cell types from a heterogenous cell suspension harvested from the seminiferous tubules through the use of Hoechst 33342 staining. Finally, extraction of spermatozoa from the Cauda Epididymis, a storage site for these mature sperm, can be performed either in conjunction with testes collection during necropsy or as an in vivo technique intended for serial sampling of sperm cells over time. Regardless, it is necessary for these methods to produce populations from spermatogonia to spermatozoa with high purity in order to produce representative qRT-PCR results downstream, indicating either presence or lack of genetic mutation enacted by future CRISPR-Cas9 experiments.

Conservatism is intrinsic to safety of emerging biotechnologies. Fear of unintended consequences, misuse, and bioterror are rightfully essential in our discussions of novel innovations. Clustered regularly Interspaced Short Palindromic Repeats (CRISPR) and its associated proteins are no exception. This review will characterize environmental and health-related risks of CRISPR-applications and expound upon mechanisms that are or can be used to minimize risk. CRISPR is broadening access and simplifying genomic and transcriptomic editing leading to wide-range usage in all of biology. Utilization in gene therapies, gene drives, and agriculture could all be universally impactful applications that need their own safety technologies and guidelines. The initial ethical guidelines and recommendations, that will guide these technologies, are being steadily developed. However, technical advances are required to facilitate safe usage. Since the advent of CRISPR gene editing in 2012 advances to limit off-target edits (both cellular and genomic) have been developed. Delivery systems that use viral or nanoparticle packaging incorporate safety mechanisms to guard against undesirable side effects are being produced and rigorously tested. Besides its applications in basic biology and potential as a gene therapy, CRISPR had humbler beginnings. Industrially it was, albeit unknowingly, used to fend off infection in productions of yogurt batches. This was one of the earliest applications of CRISPR, however with the knowledge we now have ecological and industrial uses of CRISPR have multiplied. Gene drives have the power to spread genetic mutations throughout populations and agricultural uses to better crop genomes are also of interest. These uses have struck a chord with interest groups (environmentalists, anti-GMO groups, etc) who imagine how this technology can drastically alter species with unforeseen evolutionary changes that could reshape present-day ecosystems. This review will describe existing technologies that will safeguard humanity and its interests while fully employing CRISPRs far-reaching potentiality.