Project description:Lymph node (LN) stromal cells, particularly fibroblastic reticular cells (FRCs), provide critical structural support and regulate immunity, tolerance and transport properties of LNs. In many tumors, LN metastasis is predictive of poor prognosis, however, stromal contribution to the evolving microenvironment of tumor draining LNs (TDLN) remains poorly understood. Here we present comparative transcriptional data of resting and TDLN FRCs after different time points of tumor drainage. FRCs were isolated from lymph nodes and FACS sorted based on the expression of CD45-, CD31- and PDPN+
Project description:Fibroblastic reticular cells (FRCs) (CD45- Ter119-MADCAM1- CD21/35- CD31- PDPN-) from skin draining lymph nodes of Grem1-Cre-ERT2.cki; Rosa26-LSL-EYFP mice were sorted and subjected to bulk RNA-seq of Grem1 reporter + and Grem1 reporter - cells.
Project description:The lymph node is home to resident macrophage populations that are essential for healthy immune function and homeostasis. They are involved in multiple processes including the initiation of the local response to pathogens, halting viral and bacterial spread, and clearance of apoptotic cells, but the macrophage niche and factors that create it are largely undefined. Here we analyse fibroblastic reticular cells (FRCs) as an essential component of the lymph node macrophage niche using single-cell RNA-sequencing. Our analysis revealed that most reticular cell subsets within lymph nodes expressed master macrophage regulator CSF1. We further show that signalling through CSF1R was sufficient to support macrophage development, while in the presence of LPS, FRCs underwent a mechanistic switch and maintained support through CSF1R-independent mechanisms. Our data reveal a critically important role for FRCs in the creation of the parenchymal macrophage niche within LNs.
Project description:Lymph node is a secondary lymphoid organ that has structural organization related to their immune function, which is highly ordered and compartmentalized. Lymph nodes shelter immune cells and also fibroblastic-like cells such as fibroblastic reticular cells (FRCs). FRCs have mesodermal origin and are classically characterized by the expression of podoplanin (PDPN/gp38) and lack of CD31 expression. FRCs are implicated in several immune processes but the pathways subjacent their function are still a matter of research. Another cell population found in LNs, the double negative cells (DNCs), are even less known. They do not express PDPN or CD31 markers and a specific marker is absent, their localization within the LN is undefined and their phenotype or function, remain to be clarified. Although these cells have been studied in murine models, studies on human FRCs and DNCs are limited and therefore our study should contribute to the understanding of biology and function of these cells and should promote knowledge of efficiency and disorders in the lymph node immune response. This study evaluates gene expression and secretion of cytokines and chemokines in human-derived FRCs and DNCs during homeostasis and following inflammatory stimuli. Our results demonstrate that cytokines and chemokines secreted by human FRCs and DNCs partially differ from those identified in murine models. In addition, our study demonstrates that DNCs expressed a more varied of cytokines when compared with FRCs, while FRCs expressed a wider chemokines pattern. Such differences maybe related with specific functional differences between those cell populations within LNs.
Project description:Fibroblastic reticular cells (FRCs) are heterogeneous. We use single cell RNA sequencing to identify subsets of FRCs in fat-associated lymphoid clusters (FALC) in the mesenteric adipose tissue
Project description:Communication between tumors and the stroma of tumor draining lymph nodes (TDLNs) exists before metastasis arises, altering structure and function of the TDLN niche. Transcriptional profiling of fibroblastic reticular cells (FRCs), the dominant stromal population of the LN, revealed reprogramming of these cells in immune related pathways, but also in fibroblast activation and mitochondrial function. However, tumor derived factors driving the changes in FRCs remained to be identified. Taking an unbiased approach, we show that lactic acid (LA), a metabolite released by cancer cells, is not only secreted by B16.F10 and 4T1 tumors in high amounts, but that it is also enriched in TDLNs. LA supports an upregulation of Pdpn and Thy1 and downregulation of Il7 in FRCs of TDLNs, making them akin to activated fibroblasts found at the primary tumor site. Furthermore, we show that tumor-derived LA alters mitochondrial function of FRCs of TDLNs. Thus, our results demonstrate a novel mechanism by which a tumor-derived metabolite connected with a low pH environment modulate the function of fibroblasts in TDLNs.
Project description:Gut-draining mesenteric lymph nodes (mLNs) provide the framework to shape intestinal adaptive immune responses. We previously delineated transcriptional signatures in LN stromal cells (SC), pointing to tissue-specific variability in SC composition and immunomodulatory function. Here, using scRNA-seq we dissected the developmental trajectory of SCs within mLNs derived from postnatal to aged mice, and identified two putative progenitors, namely CD34+ SC and fibroblastic reticular stromal cell (FRC) progenitors, which both feed the rapid LN expansion postnatally. We further unraveled the tissue-specific chromatin accessibility and DNA methylation landscape of non-endothelial SCs, and identified a microbiota-independent core epigenomic signature, showcasing differences between SCs from mLN and skin-draining peripheral LN. Irf3 was inferred from the epigenomic landscape of SCs, being dynamically expressed along the differentiation trajectories of FRCs. Lentiviral overexpression of Irf3 in a mesenchymal stem cell line established a Cxcl9+ FRC molecular phenotype. The relevance of Irf3 for SC biology was further underscored by the diminished proportion of Ccl19+ and Cxcl9+ FRCs in LNs from Irf3-/- mice. Together, our data constitute a comprehensive transcriptional and epigenomic map of LNSC development in early life and dissect location-specific, microbiota-independent properties of non-endothelial SCs.