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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2018)

Skeletal muscle is the most abundant tissue in the body, comprising up to 40% of the total mass. In addition to its most salient role in locomotion, it also plays a central role in metabolic homeostasis. Therefore, injury-, age- and disease-related compromise of skeletal muscle can be extremely detrimental to overall health and quality of life. As such, the development of regenerative therapies for skeletal muscle that contribute to in vivo repair, as well as in vitro strategies that can hasten the development of personalized drug treatment, could be of vital importance. Human induced pluripotent stem cells (hiPSCs) are a powerful tool that can meet both these challenges; they are patient-specific, can give rise to derivatives of all three germ layers, including myogenic progenitors, and are scalable since pluripotent cells readily self-renew in vitro. However, the robust, transgene free myogenic differentiation of hiPSCs remains a hurdle.

In this dissertation, I address these challenges by identifying key time-varying signaling, transcriptional, and epigenetic-related mechanisms that lead to enhanced in vitro myogenesis by comparing the longitudinal transcriptomic profiles of multiple hiPSC lines. Furthermore, I show that targeted genetic perturbation at the outset of differentiation may bias lineage specification to the paraxial mesoderm fate. Finally, through the selective expansion and terminal differentiation of hiPSC-derived myogenic progenitor cell populations, we show that they form functional 3D microtissues in an in vitro skeletal muscle-on-a-chip platform, as well as give rise to dystophin positive fibers in vivo in a murine model of muscular dystrophy.

    Cover page: Elucidation of mechanisms of in vitro myogenesis of human induced pluripotent stem cells with functional validation in vitro and in vivo
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2023)
    INTRODUCTION: B cells play an integral role in the immune response to both dengue fever and COVID-19. Prior scRNAseq analyses of peripheral plasmablasts in COVID-19 have revealed a heterogeneous population with distinct cell subsets associated with proliferation; prior studies in patients with dengue fever have likewise shown the presence of proliferative pre-plasmablasts in the circulation. These findings may have implications for disease severity. In this study, we sought to gain a mechanistic understanding of the intracellular processes in naive and memory B cells that are associated with and may lead to an expanded proliferative plasmablast population in the circulation. METHODS: We analyzed age-controlled (pediatric and adult), peripheral blood mononuclear cell scRNAseq datasets from patients infected with either dengue (primary or secondary) or COVID-19 (non-severe or severe) from previously published studies. Our preliminary analysis showed that pediatric patients with dengue and adults with COVID-19 had an expanded proliferative plasmablast (p-PB) population. By contrast, neither the adults with dengue nor the children with COVID-19 in our dataset had p-PBs. We used this distinctive preliminary signature to guide our analyses design and expanded our analyses to naive and memory B cells. RESULTS: In age/disease conditions with and without p-PBs, we found differences in cell sensing and activation, including via the B cell receptor and downstream signal transduction. Likewise, inflammation was mediated differently: relative to groups without p-PBs, those with p-PBs had increased expression of interferon response and S100 genes (particularly severe COVID-19). Furthermore, several transcription factors at the nexus of activation, inflammation, and cell fate decisions were expressed differently in groups with and without p-PBs. DISCUSSION: We used dengue and COVID-19 infections in adult and pediatric patients (focusing on naive B, memory B, and plasmablast cells) as a model to better understand the mechanisms that may give rise to p-PB populations in the circulation. Our results indicate that a more pro-inflammatory state in naive and memory B cells correlated with - and could influence the generation of- proliferating plasmablasts. Further exploration of these mechanisms will have implications for immune memory, vaccine development, and post-viral autoimmune syndromes.
      Cover page: The Janus face of proliferating plasmablasts in dengue and COVID-19 infections.
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