Project description:Apoptosis and clearance of apoptotic cells via efferocytosis are evolutionarily conserved processes that drive tissue repair. However, the mechanisms by which recognition and clearance of apoptotic cells regulate repair are not fully understood. Here, we use single-cell RNA sequencing to provide a map of the cellular dynamics during early inflammation in mouse skin wounds. We find that apoptotic pathways and efferocytosis receptors are elevated in fibroblasts and immune cells, including resident Lyve1+ macrophages, during inflammation.
Project description:Although apoptotic cells (ACs) contain nucleic acids that can be recognized by Toll-like receptors (TLRs), engulfment of ACs does not initiate inflammation in healthy organisms. To better understand this phenomenon, we identified and characterized macrophage populations that continually engulf ACs in several distinct tissues. These macrophages share characteristics compatible with immunologically silent clearance of ACs, including high expression of AC recognition receptors, low expression of TLR9, and reduced TLR responsiveness to nucleic acids. When removed from tissues, these macrophages lose many of these characteristics and generate inflammatory responses to AC-derived nucleic acids, suggesting that cues from the tissue microenvironment are required to program macrophages for silent AC clearance. We show that KLF2 and KLF4 control expression of many genes within this AC clearance program. Coordinated expression of AC receptors with genes that limit responses to nucleic acids may represent a central feature of tissue macrophages that ensures maintenance of homeostasis.
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.
Project description:This a model from the article:
Modelling the onset of Type 1 diabetes: can impaired macrophage phagocytosis make the difference between health and disease?
Maree AF, Kublik R, Finegood DT, Edelstein-Keshet L.Philos Transact A Math Phys Eng Sci.2006 May 15;364(1842):1267-82.
16608707,
Abstract:
A wave of apoptosis (programmed cell death) occurs normally in pancreatic beta-cells of newborn mice. We previously showed that macrophages from non-obese diabetic (NOD) mice become activated more slowly and engulf apoptotic cells at a lower rate than macrophages from control (Balb/c) mice. It has been hypothesized that this low clearance could result in secondary necrosis, escalating inflammation and self-antigen presentation that later triggers autoimmune, Type 1 diabetes (T1D). We here investigate whether this hypothesis could offer a reasonable and parsimonious explanation for onset of T1D in NOD mice. We quantify variants of the Copenhagen model (Freiesleben De Blasio et al. 1999 Diabetes 48, 1677), based on parameters from NOD and Balb/c experimental data. We show that the original Copenhagen model fails to explain observed phenomena within a reasonable range of parameter values, predicting an unrealistic all-or-none disease occurrence for both strains. However, if we take into account that, in general, activated macrophages produce harmful cytokines only when engulfing necrotic (but not apoptotic) cells, then the revised model becomes qualitatively and quantitatively reasonable. Further, we show that known differences between NOD and Balb/c mouse macrophage kinetics are large enough to account for the fact that an apoptotic wave can trigger escalating inflammatory response in NOD, but not Balb/c mice. In Balb/c mice, macrophages clear the apoptotic wave so efficiently, that chronic inflammation is prevented.
This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2011 The BioModels.net Team.
For more information see the terms of use.
To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.
Project description:The role of tissue resident macrophages during tissue regeneration or fibrosis is not well-understood, mainly due to the lack of a specific marker for their identification. Here, we identified two populations of skeletal muscle resident macrophages: TIM4- macrophages which are replenished from the blood and LYVE1+TIM4+ macrophages that locally self-renew (self-renewing resident macrophages, SRRMs). Using a CSF1R inhibition/withdrawal approach to specifically deplete SRRMs, we found that they provide a non-redundant function in clearing damage-induced apoptotic cells early after extensive acute injury. In contrast, in chronic mild injury as seen in a mouse model of Duchenne muscular dystrophy, we showed that depletion of both resident populations through long term CSF1R inhibition changes muscle fiber composition from damage-sensitive glycolytic fibers towards damage-resistant glycolytic-oxidative fibers protecting muscle against contraction induced injury. This later finding reveals a new role for resident macrophages in modulating tissue metabolism and has therapeutic potential in light of the ongoing clinical testing of CSF1R inhibitors.
Project description:The role of tissue resident macrophages during tissue regeneration or fibrosis is not well-understood, mainly due to the lack of a specific marker for their identification. Here, we identified two populations of skeletal muscle resident macrophages: TIM4- macrophages which are replenished from the blood and LYVE1+TIM4+ macrophages that locally self-renew (self-renewing resident macrophages, SRRMs). Using a CSF1R inhibition/withdrawal approach to specifically deplete SRRMs, we found that they provide a non-redundant function in clearing damage-induced apoptotic cells early after extensive acute injury. In contrast, in chronic mild injury as seen in a mouse model of Duchenne muscular dystrophy, we showed that depletion of both resident populations through long term CSF1R inhibition changes muscle fiber composition from damage-sensitive glycolytic fibers towards damage-resistant glycolytic-oxidative fibers protecting muscle against contraction induced injury. This later finding reveals a new role for resident macrophages in modulating tissue metabolism and has therapeutic potential in light of the ongoing clinical testing of CSF1R inhibitors.
Project description:PURPOSE: To provide a detailed gene expression profile of the normal postnatal mouse cornea. METHODS: Serial analysis of gene expression (SAGE) was performed on postnatal day (PN)9 and adult mouse (6 week) total corneas. The expression of selected genes was analyzed by in situ hybridization. RESULTS: A total of 64,272 PN9 and 62,206 adult tags were sequenced. Mouse corneal transcriptomes are composed of at least 19,544 and 18,509 unique mRNAs, respectively. One third of the unique tags were expressed at both stages, whereas a third was identified exclusively in PN9 or adult corneas. Three hundred thirty-four PN9 and 339 adult tags were enriched more than fivefold over other published nonocular libraries. Abundant transcripts were associated with metabolic functions, redox activities, and barrier integrity. Three members of the Ly-6/uPAR family whose functions are unknown in the cornea constitute more than 1% of the total mRNA. Aquaporin 5, epithelial membrane protein and glutathione-S-transferase (GST) omega-1, and GST alpha-4 mRNAs were preferentially expressed in distinct corneal epithelial layers, providing new markers for stratification. More than 200 tags were differentially expressed, of which 25 mediate transcription. CONCLUSIONS: In addition to providing a detailed profile of expressed genes in the PN9 and mature mouse cornea, the present SAGE data demonstrate dynamic changes in gene expression after eye opening and provide new probes for exploring corneal epithelial cell stratification, development, and function and for exploring the intricate relationship between programmed and environmentally induced gene expression in the cornea. Keywords: other
Project description:Poor wound healing due to dysregulated tissue repair responses can exacerbate and prolong disease. Successful tissue repair is critically dependent on the timely clearance of apoptotic cells by macrophages in a process termed efferocytosis. Mechanisms and factors that link these two fundamental processes are therefore of great interest. Herein, we observed that a subset of 12-lipoxygenase (ALOX12)-expressing macrophages upregulate the production of host protective autacoids termed maresin conjugates in tissue regeneration (MCTR) during efferocytosis. MCTRs in turn play autocrine and paracrine functions in enhancing the ability of both ALOX12-positive and surrounding ALOX12-negative macrophages to uptake apoptotic cells. These effects of ALOX12-positive macrophages and MCTRs in regulating apoptotic cells clearance was also observed at sites of high apoptotic cell burden in mouse and flatworm models, as the formation of these mediators was upregulated and abrogation of related ALOX activity in mice reduced the ability of macrophages to clear apoptotic cells. Furthermore, add-back of MCTRs rapidly enhanced the efferocytosis capability of macrophages in mice and planarian flatworms. Mechanistic studies in macrophages revealed that MCTRs modulated Rac1 signalling and glycolytic metabolism, two pathways crucial for effective efferocytosis, and enhanced efferocytosis-induced WNT ligand production. Inhibition of Rac1 abrogated the ability of MCTRs to enhance glucose uptake and efferocytosis in vitro, while inhibiting either Rac1, glycolysis, or WNT ligand production prevented MCTR-mediated enhancement of apoptotic cell clearance and tissue regeneration. Taken together, our findings identify a central role for ALOX12-expressing macrophages in the regulation of efferocytosis and tissue repair via the local formation of MCTRs.