Despite the prevalence of sarcoidosis, the underlying cause is not well understood. In particular, the initial steps in the formation of granulomas in sarcoidosis and the driving cells are unknown. There is evidence to suggest that macrophage plays a key role in the development of sarcoidosis. In the healthy lung, macrophages form a heterogeneous population with varying ontogenies and functions. We have previously shown that the epigenomic landscape of tissue-resident macrophages are shaped by the local environment. Signals in the environment trigger tissue-specific transcription factors that work in combination with lineage factors to specify the gene regulatory networks (GRN) of macrophages – in other words, the interactions between genes and cis-regulatory elements that regulate gene expression. The plastic nature of macrophage GRN allows them to adopt distinct functions depending on the tissue in which they reside. Moreover, studies in in vitro macrophages have shown that their response to stimuli, such as LPS, is largely determined by their pre-existing epigenomic landscape. The disease environment is likely to provide additional signals that further reprogram the macrophage GRN. In our prior study, we performed bronchoalveolar lavage (BAL) on sarcoidosis patients and healthy controls followed by single-cell RNA-seq. Our preliminary data shows that the macrophage subpopulations in sarcoidosis exhibited distinct transcriptional profiles from those in health. Moreover, different sarcoidosis expressed genes associated with distinct functions and regulatory factors. Thus, we hypothesize that macrophages subpopulations play distinct roles in the development of granulomas in sarcoidosis. To test this hypothesis, we propose to use an established in vitro model of granuloma formation using PBMCs from sarcoidosis patients. In Aim1, we will perform single-cell RNA-seq on our granuloma model to determine the overall cell composition and verify the presence of macrophage subpopulations. We will compare these results to our data from previously collected BAL samples. In Aim 2, we will use RNA interference (RNAi) to target regulatory factors associated with each of our previously identified macrophage subpopulations. We will determine the effect of disrupting the GRN of these subpopulations on granuloma formation in our in vitro model. These results will demonstrate the feasibility and relevance of in vitro granulomas for modelling in vivo disease processes. It will also provide a mechanism to test the role of different macrophage sub-populations and potentially provide targets for therapeutic treatments. As junior investigator aiming to pursue a research program in the functional genomics of sarcoidosis, this study will provide essential preliminary data for future grant applications. In the long term, we hope to extend these studies to a wider cohort in order to better understand the heterogeneity of sarcoidosis and explore the effect of therapeutic interventions.
|Effective start/end date||3/31/21 → 3/30/22|
- American Thoracic Society, Inc. (Letter - 04-13-2021)
- Mallinckrodt plc (Letter - 04-13-2021)
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