Stem cells tightly regulate dead cell clearance to maintain tissue fitness [ATAC-seq]
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE271006 | GEO | 2024/06/28
REPOSITORIES: GEO
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Project description:Macrophages and dendritic cells have long been appreciated for their ability to migrate to and engulf dying cells and debris, including some of the billions of cells that are naturally eliminated from our body daily. However, a substantial amount of these dying cells are cleared by local tissue cells, so-called ‘non-professional phagocytes’, critical to preserve organismal fitness. How non-professional phagocytes are able to sense and digest nearby apoptotic corpses while still performing their normal tissue functions is unclear. Here, we explore the molecular mechanisms underlying this balancing act. Exploiting the cyclical bouts of tissue regeneration and degeneration during the hair cycle, we show that stem cells can transiently become non-professional phagocytes when confronted with dying cells. Adoption of this phagocytic state requires not only local lipids produced by apoptotic corpses, which are necessary for RXRα activation, but also tissue-specific retinoids able to activate RARg. The dual factor dependency enables tight regulation of the genes requisite to activate phagocytic apoptotic clearance. The tunable phagocytic program we describe here offers an attractive mechanism to offset phagocytic duties against the primary stem cell function of replenishing differentiated cells to preserve tissue integrity during homeostasis. Our findings have broad implications for other non-motile stem or progenitor cells which experience cell death in an immune-privileged niche.
2024-06-28 | GSE270947 | GEO
Project description:Macrophages and dendritic cells have long been appreciated for their ability to migrate to and engulf dying cells and debris, including some of the billions of cells that are naturally eliminated from our body daily. However, a substantial amount of these dying cells are cleared by local tissue cells, so-called ‘non-professional phagocytes’, critical to preserve organismal fitness. How non-professional phagocytes are able to sense and digest nearby apoptotic corpses while still performing their normal tissue functions is unclear. Here, we explore the molecular mechanisms underlying this balancing act. Exploiting the cyclical bouts of tissue regeneration and degeneration during the hair cycle, we show that stem cells can transiently become non-professional phagocytes when confronted with dying cells. Adoption of this phagocytic state requires not only local lipids produced by apoptotic corpses, which are necessary for RXRα activation, but also tissue-specific retinoids able to activate RARg. The dual factor dependency enables tight regulation of the genes requisite to activate phagocytic apoptotic clearance. The tunable phagocytic program we describe here offers an attractive mechanism to offset phagocytic duties against the primary stem cell function of replenishing differentiated cells to preserve tissue integrity during homeostasis. Our findings have broad implications for other non-motile stem or progenitor cells which experience cell death in an immune-privileged niche.
2024-06-29 | GSE271100 | GEO
Project description:Macrophages and dendritic cells have long been appreciated for their ability to migrate to and engulf dying cells and debris, including some of the billions of cells that are naturally eliminated from our body daily. However, a substantial amount of these dying cells are cleared by local tissue cells, so-called ‘non-professional phagocytes’, critical to preserve organismal fitness. How non-professional phagocytes are able to sense and digest nearby apoptotic corpses while still performing their normal tissue functions is unclear. Here, we explore the molecular mechanisms underlying this balancing act. Exploiting the cyclical bouts of tissue regeneration and degeneration during the hair cycle, we show that stem cells can transiently become non-professional phagocytes when confronted with dying cells. Adoption of this phagocytic state requires not only local lipids produced by apoptotic corpses, which are necessary for RXRα activation, but also tissue-specific retinoids able to activate RARg. The dual factor dependency enables tight regulation of the genes requisite to activate phagocytic apoptotic clearance. The tunable phagocytic program we describe here offers an attractive mechanism to offset phagocytic duties against the primary stem cell function of replenishing differentiated cells to preserve tissue integrity during homeostasis. Our findings have broad implications for other non-motile stem or progenitor cells which experience cell death in an immune-privileged niche.
2023-08-07 | GSE230523 | GEO
Project description:Recognition and removal of apoptotic cells by professional phagocytes, including dendritic cells and macrophages, preserve self-tolerance and prevent chronic inflammation and autoimmune pathologies. However the diverse array of phagocytes residing within different tissues combined with the necessarily prompt nature of apoptotic cell clearance has made it difficult to study this process in situ. Thus, the full spectrum of functions executed by tissue resident phagocytes in response to homeostatic apoptosis remains unclear. We used microarrays to characterize the transcriptome within murine intestinal dendritic cells and macrophages both before and after in situ phagocytosis of apoptotic intestinal epithelial cells.
2016-11-10 | GSE85682 | GEO
Project description:On a daily basis, we turnover billions of apoptotic cells that are removed by professional and non-professional phagocytes1-10. While characterizing the transcriptional program of phagocytes, we discovered a novel solute carrier family (SLC) gene signature (33 SLC members) that is specifically modified during engulfment of apoptotic cells (efferocytosis) but not during antibody-mediated phagocytosis. When we assessed the functional relevance of these SLCs, we noted robust induction of an aerobic glycolysis program in engulfing phagocytes, initiated by SLC2A1-mediated glucose uptake, and suppression of oxidative phosphorylation program. Interestingly, the different steps of phagocytosis10,11, i.e. smell (‘find-me’ signals / sensing factors released by apoptotic cells), taste (phagocyte- apoptotic cell contact), and ingestion (corpse internalization), activated different molecules to promote this glycolytic process. Further, lactate, a natural by-product of aerobic glycolysis12,13, was released from engulfing phagocytes via SLC16A1, an SLC member activated after corpse uptake. While glycolysis within phagocytes contributed to actin polymerization and the continued uptake of corpses, the lactate released via SLC16A1 influenced the establishment of an anti-inflammatory environment. Collectively, these data reveal a novel SLC program activated during efferocytosis, identify a previously unknown reliance on aerobic glycolysis during apoptotic cell uptake, and that glycolytic byproducts of efferocytosis can also influence other cells in the microenvironment.
2018-11-30 | GSE119273 | GEO
Project description:Professional phagocytes (such as macrophages) and non-professional phagocytes (such as epithelial cells) clear billions of apoptotic cells and particles on a daily basis. Since these phagocytes reside in proximity in most tissues, whether cross-communication exists between them during cell clearance, and how this might impact inflammation are not known. Here, we show that macrophages, via the release of a soluble growth factor and microvesicles, redirect the type of particles engulfed by non-professional phagocytes and influence their inflammatory response. During apoptotic cell engulfment or in response to inflammation-associated cytokines, macrophages released insulin-like growth factor 1 (IGF-1). The binding of IGF-1 to its receptor on non-professional phagocytes redirected their phagocytosis, such that uptake of larger apoptotic cells was dampened while engulfment of microvesicles was enhanced. Macrophages were refractory to this IGF-1 mediated engulfment modulation. Macrophages also released microvesicles, whose uptake by epithelial cells, enhanced by IGF-1, led to decreased inflammatory responses by epithelial cells. Consistent with these observations, deletion of IGF-1 receptor in airway epithelial cells led to exacerbated lung inflammation after allergen exposure. These genetic and functional studies reveal a novel IGF-1 and microvesicle-dependent communication between macrophages and epithelial cells that can critically influence the magnitude of tissue inflammation in vivo.
2016-11-01 | GSE89049 | GEO
Project description:The phagocytic elimination of cells undergoing apoptosis is an evolutionarily conserved innate immune mechanism for eliminating unnecessary cells. Previous studies showed an increase in the level of engulfment receptors in phagocytes after the phagocytosis of apoptotic cells, which leads to the enhancement of their phagocytic activity. However, precise mechanisms underlying this phenomenon require further clarification. We found that the pre-incubation of a Drosophila phagocyte cell line with the fragments of apoptotic cells enhanced the subsequent phagocytosis of apoptotic cells, accompanied by an augmented expression of the engulfment receptors Draper and integrin αPS3. The DNA-binding activity of the transcription repressor Tailless was transiently raised in those phagocytes, depending on two partially overlapping signal-transduction pathways for the induction of phagocytosis as well as the occurrence of engulfment. The RNAi knockdown of tailless in phagocytes abrogated the enhancement of both phagocytosis and engulfment receptor expression. Furthermore, the hemocyte-specific RNAi of tailless reduced apoptotic cell clearance in Drosophila embryos. Taken together, we propose the following mechanism for the activation of Drosophila phagocytes after an encounter with apoptotic cells: two partially overlapping signaltransduction pathways for phagocytosis are initiated; transcription repressor Tailless is activated; expression of engulfment receptors is stimulated; and phagocytic activity is enhanced. This phenomenon most likely ensures the phagocytic elimination of apoptotic cells that stimulated phagocytes find thereafter and is thus considered as a mechanism to prime phagocytes in innate immunity.
2017-03-23 | GSE85429 | GEO
Project description:Phagocytes in different tissues recognize and remove apoptotic cells via the process of efferocytosis. Although it is well-established that efferocytosis elicits an anti-inflammatory response by phagocytes, the molecules and mechanisms that enforce this response in phagocytes are still being defined. In attempting to decipher gene programs induced after a phagocyte ingests a dying cell, we uncovered a chloride-sensing signaling pathway that controls both the ‘appetite’ of a phagocyte and how a phagocyte responds after corpse uptake. First, we noted that within phagocytes that have ingested a corpse, the solute carrier 12 (SLC12) family members SLC12A2 and SLC12A4 are actively modulated. Interfering with SLC12A2, either genetically or pharmacologically, led to significantly enhanced corpse uptake per phagocyte, while loss of SLC12A4 inhibited corpse uptake. Interestingly, when phagocytes with disrupted SLC12A2 engulfed apoptotic corpses, the typical homeostatic efferocytosis signature was perturbed, characterized by loss of the canonical anti-inflammatory program and replaced by pro-inflammatory and oxidative stress-associated gene programs. In further mechanistic studies, we observed efferocytosis was also regulated by the chloride-sensing pathway upstream of SLC12A2, including the kinases WNK1-OSR1-SPAK, and this involved chloride entry/exit across the plasma membrane of phagocytes during corpse engulfment. We also show that the ‘switch’ to pro-inflammatory sensing of apoptotic cells is specifically due to disruption of the chloride-sensing pathway and not due to corpse overload or poor degradation, and that the pro-inflammatory gene signature can be reversed using a chloride ionophore. Collectively, these data identify the WNK1-OSR1-SPAK-SLC12A2/SLC12A4 chloride-sensing pathway and chloride flux in phagocytes as key modifiers of how a phagocyte interprets an engulfed apoptotic corpse.
2020-03-24 | GSE131860 | GEO
Project description:Apoptosis accounts for ~ 90% of homeostatic cell turnover in the body1. While caspase-dependent apoptosis is known to influence immune tolerance, induction of cell proliferation, and tissue regeneration2-4, how these apoptotic cells contribute to such diverse effects is less understood. Soluble factors released from apoptotic cells could be a means of ‘talking’ to healthy cells in the tissue neighborhood. While a few phagocyte-attracting ‘find-me’ signals released from apoptotic cells are known5, the larger ‘metabolite secretome’ from apoptotic cells is not yet defined. Here, via unbiased profiling of the apoptotic cell secretome, we identified 123 metabolites that are specifically released during apoptosis, while cells still retain membrane integrity. Release of ~25 of these metabolites is dependent on Pannexin 1 (Panx1) channels, which are opened by caspase-dependent cleavage during apoptosis. Interestingly, one of the Panx1-dependent metabolites from apoptotic cells is spermidine, a polyamine whose release could be, in part, due to the continued metabolic activity of dying cells. RNAseq analysis of healthy cells exposed to the apoptotic secretome revealed Panx1-dependent gene programs, including genes linked to suppression of inflammation, cell proliferation, and wound healing. Analysis of the apoptotic secretome across cell types and different apoptotic stimuli, identified a core “set” of 8 Panx1-dependent metabolites. Strikingly, a selected cocktail of these metabolites demonstrated significant immunosuppressive effects by potently reducing disease severity in an inflammatory arthritis model and a lung graft rejection model. Collectively, these data advance the concept that apoptotic cells are not ‘inert’ corpses waiting for removal by phagocytes, but rather they actively communicate with the tissue environment through their metabolite secretome, with implications in tissue inflammation.
2020-03-19 | GSE131906 | GEO
Project description:The efficient clearance of dead and dying cells, also known as efferocytosis, is critical to maintain tissue homeostasis. In the bone marrow microenvironment (BMME), this role is primarily fulfilled by professional bone marrow macrophages, but recent work has shown that mesenchymal stromal cells (MSCs) act as a non-professional phagocyte within the BMME. However, little is known about the mechanism and impact of efferocytosis on MSCs in the BMME and on their function. To investigate this, we performed flow cytometric analysis of neutrophil uptake by ST2 cells, a murine bone marrow-derived stromal cell line, and in murine primary bone marrow-derived stromal cells. Transcriptional analysis showed that MSCs possess the necessary receptors and internal processing machinery to conduct efferocytosis, with Axl and Tyro3 serving as the main receptors, while MerTK was not expressed. Moreover, the expression of these receptors was modulated by efferocytic behavior, regardless of apoptotic target. MSCs derived from human bone marrow also demonstrated efferocytic behavior, showing that MSC efferocytosis is conserved. In all MSCs, efferocytosis impaired osteoblastic differentiation. Transcriptional analysis and functional assays identified downregulation in MSC mitochondrial function upon efferocytosis. Experimentally, efferocytosis induced mitochondrial fission in MSCs. Pharmacologic inhibition of mitochondrial fission in MSCs not only decreased efferocytic activity but also rescued osteoblastic differentiation, demonstrating that efferocytosis-mediated mitochondrial remodeling plays a critical role in regulating MSC differentiation. This work describes a novel function of MSCs as non-professional phagocytes within the BMME and demonstrates that efferocytosis by MSCs plays a key role in directing mitochondrial remodeling and MSC differentiation. Efferocytosis by MSCs may therefore be a novel mechanism of dysfunction and senescence. Since our data in human MSCs show that MSC efferocytosis is conserved, the consequences of MSC efferocytosis may impact the behavior of these cells in the human skeleton, including osteoporosis in aging.
2023-07-14 | GSE223279 | GEO