Immune Dysregulation in Sarcoidosis

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Abstract Sarcoidosis is a poorly characterized immune disorder that has often been called the “Great Imitator” due to its similarity to a variety of other diseases and the difficulty of diagnosis. The disease causes aggregates of immune cells called granulomas to form in various tissues, causing organ damage and eventual death in severe cases. Sarcoidosis etiology remains largely unknown, with no clear trigger and symptoms that can disappear on their own or worsen despite treatment. Current research has uncovered associations with some common bacterial species as well as immune dysregulation, especially in the T helper 1, T helper 17, and T regulatory cell populations. However, progress in the field has been hampered in part by the complexity of the disease and limitations in current models. We hypothesize that distinct subpopulations of T cells drive immune dysregulation and progression in sarcoidosis. We further hypothesize that this dysregulation differentiates sarcoidosis from other granulomatous processes and provides a basis for disease specific modeling and drug discovery. Aim 1 will apply recently developed single-cell level sequencing techniques to better elucidate the complex network of gene and cell interactions involved in pathogenesis. Samples of sarcoidosis patient granulomas and peripheral blood mononuclear cells (PBMCs) will be analyzed via single-cell RNA sequencing. Their transcriptomes will be compared to the PBMCs of control subjects as well as control granulomas formed by stimulation of control PBMCs with purified protein derivative. Cells will be identified by their gene expression profiles, then assessed for differences in gene expression and regulation in sarcoidosis compared to controls. We will use this data to develop a transcriptomic atlas of cell types and regulatory networks in sarcoidosis. Aim 2 will use this atlas to evaluate in vitro sarcoidosis models which successfully utilized patient samples to elucidate differences between disease and controls. Granulomas created using each model will be analyzed via single-cell RNA-seq and compared to our sarcoidosis transcriptomic atlas. This approach fosters detailed evaluation of the sarcoidosis immune environment and the evaluation of the capability of existing sarcoidosis models to mimic sarcoidosis. This project integrates recent advances in sequencing and bioinformatics to uncover mechanisms involved in sarcoidosis. The single-cell transcriptomic atlas of sarcoidosis granulomas and PBMCs will interrogate cellular interactions that regulate immune dysfunction in sarcoidosis, providing new points of focus for further mechanistic research. Our analysis of sarcoidosis models will guide further model design, and design of high throughput biomarker and drug screens for sarcoidosis. This project has the potential to improve the specificity and efficacy of treatment, as well as the ease of diagnosis. The multidisciplinary research also lays the groundwork for my training as a physician scientist while exploring a key clinical question.