Dataset Information

Staphylococcus aureus biofilm elicits the expansion, activation and polarization of myeloid-derived suppressor cells in vivo and in vitro.

ABSTRACT: Staphylococcus aureus (S. aureus) is one of the most common causes of biofilm infections in periprosthetic joint infections (PJIs). Accumulating evidence has shown that the immunosuppressive environment established by S. aureus biofilm infection in PJIs involves the presence of myeloid-derived suppressor cells (MDSCs) and M2-macrophages. Due to the diversity of MDSCs, little is known about whether S. aureus biofilm preferentially expands specific MDSC subsets or whether MDSCs can further differentiate into M2-macrophages during S. aureus biofilm infection. Here, we show that in agreement with the results from an established rat PJI model, S. aureus biofilm cocultured with freshly isolated bone marrow cells (BMCs) in vitro significantly increases the proportions of MDSCs, total macrophages and M2-macrophages. Interestingly, we find that treatment of the BMCs in vitro with S. aureus biofilm preferentially promotes the expansion of monocytic MDSCs but not granulocytic MDSCs. Biofilm treatment also substantially enhances the overall MDSC immunosuppressive activity in addition to the MDSC expansion in vitro. Importantly, we provide evidence that S. aureus biofilm is capable of further stimulating the conversion of monocytic MDSCs into M2-macrophages in vitro and in vivo. Collectively, our studies reveal a direct link between MDSCs and M2-macrophages occurring in S. aureus-associated PJIs.

SUBMITTER: Peng KT

PROVIDER: S-EPMC5559065 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Staphylococcus aureus biofilm elicits the expansion, activation and polarization of myeloid-derived suppressor cells in vivo and in vitro.

Peng Kuo-Ti KT Hsieh Ching-Chuan CC Huang Tsung-Yu TY Chen Pei-Chun PC Shih Hsin-Nung HN Lee Mel S MS Chang Pey-Jium PJ

PloS one 20170816 8

Staphylococcus aureus (S. aureus) is one of the most common causes of biofilm infections in periprosthetic joint infections (PJIs). Accumulating evidence has shown that the immunosuppressive environment established by S. aureus biofilm infection in PJIs involves the presence of myeloid-derived suppressor cells (MDSCs) and M2-macrophages. Due to the diversity of MDSCs, little is known about whether S. aureus biofilm preferentially expands specific MDSC subsets or whether MDSCs can further differe ...[more]

PMID: 28813499

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Project description:Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature monocytes and granulocytes. While neutrophils (polymorphonuclear leukocytes [PMNs]) are classically identified as highly differentiated cells specialized for antimicrobial defense, our laboratory has reported minor contributions of PMNs to the immune response during Staphylococcus aureus biofilm infection. However, these two cell types can be difficult to differentiate because of shared surface marker expression. Here we describe a more refined approach to distinguish MDSCs from PMNs utilizing the integrin receptor CD11b combined with conventional Ly6G and Ly6C expression. This approach separated the Ly6G+ Ly6C+ population that we previously identified in a mouse model of S. aureus orthopedic implant infection into two subsets, namely, CD11bhigh Ly6G+ Ly6C+ MDSCs and CD11blow Ly6G+ Ly6C+ PMNs, which was confirmed by characteristic nuclear morphology using cytospins. CD11bhigh Ly6G+ Ly6C+ MDSCs suppressed T cell proliferation throughout the 28-day infection period, whereas CD11blow Ly6G+ Ly6C+ PMNs had no effect early (day 3 postinfection), although this population acquired suppressive activity at later stages of biofilm development. To further highlight the distinctions between biofilm-associated MDSCs and PMNs versus monocytes, transcriptional profiles were compared by transcriptome sequencing (RNA-Seq). A total of 6,466 genes were significantly differentially expressed in MDSCs versus monocytes, whereas only 297 genes were significantly different between MDSCs and PMNs. A number of genes implicated in cell cycle regulation were identified, and in vivo ethynyldeoxyuridine (EdU) labeling revealed that approximately 50% of MDSCs proliferated locally at the site of S. aureus biofilm infection. Based on their similar transcriptomic profiles to those of PMNs, biofilm-associated MDSCs are of a granulocytic lineage and can be classified as granulocytic MDSCs (G-MDSCs).

Project description:Staphylococcus aureus is a leading cause of device-associated biofilm infections, which represent a serious health care concern based on their chronicity and antibiotic resistance. We previously reported that S. aureus biofilms preferentially recruit myeloid-derived suppressor cells (MDSCs), which promote monocyte and macrophage anti-inflammatory properties. This is associated with increased myeloid arginase-1 (Arg-1) expression, which has been linked to anti-inflammatory and profibrotic activities that are observed during S. aureus biofilm infections. To determine whether MDSCs and macrophages utilize Arg-1 to promote biofilm infection, Arg-1 was deleted in myeloid cells by use of Tie-2Cre mice. Despite Arg-1 expression in biofilm-associated myeloid cells, bacterial burdens and leukocyte infiltrates were similar between wild-type (WT) and Arg-1fl/fl;Tie-2Cre conditional knockout (KO) mice from days 3 to 14 postinfection in both orthopedic implant and catheter-associated biofilm models. However, inducible nitric oxide synthase (iNOS) expression was dramatically elevated in biofilm-associated MDSCs from Arg-1fl/fl;Tie-2Cre animals, suggesting a potential Arg-1-independent compensatory mechanism for MDSC-mediated immunomodulation. Treatment of Arg-1fl/fl;Tie-2Cre mice with the iNOS inhibitor N6-(1-iminoethyl)-l-lysine (l-NIL) had no effect on biofilm burdens or immune infiltrates, whereas treatment of WT mice with the Arg-1/ornithine decarboxylase inhibitor difluoromethylornithine (DFMO) increased bacterial titers, but only in the surrounding soft tissues, which possess attributes of a planktonic environment. A role for myeloid-derived Arg-1 in regulating planktonic infection was confirmed using a subcutaneous abscess model, in which S. aureus burdens were significantly increased in Arg-1fl/fl;Tie-2Cre mice compared to those in WT mice. Collectively, these results indicate that the effects of myeloid Arg-1 are context dependent and are manifest during planktonic but not biofilm infection.

Dataset Information

Staphylococcus aureus biofilm elicits the expansion, activation and polarization of myeloid-derived suppressor cells in vivo and in vitro.

Publications

Staphylococcus aureus biofilm elicits the expansion, activation and polarization of myeloid-derived suppressor cells in vivo and in vitro.

Similar Datasets

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