Related Experiment Video
Updated: Oct 2, 2025
Polarization and Characterization of M1 and M2 Human Monocyte-Derived Macrophages on Implant Surfaces
Published on: December 6, 2024
miRNA-Mediated Priming of Macrophage M1 Differentiation Differs in Gram-Positive and Gram-Negative Settings
Georg Riechert1, Daniel Maucher1, Birte Schmidt1
1University Clinic and Outpatient Clinic for Anesthesiology and Operative Intensive Care, University Medicine Halle (Saale), Franzosenweg 1a, 06112 Halle (Saale), Germany.
Abstract:
A proper regulation of macrophage polarization is essential for the organism's health and pathogen control. Differentiation control is known to occur at the transcriptional as well as the posttranscriptional levels. The mechanisms involved, however, have not yet been fully elucidated. In this study, we co-cultured macrophages with viable Gram-positive and Gram-negative bacteria to mimic macrophage differentiation to the M1-like type in an inflammatory milieu. We found that Gram-positive stimulation resulted in increased expressions of miR-7a-5p, miR-148a-3p, miR-155-5p, and miR-351-5p. Of note, these miRNAs were found to target inhibitory mediators of the Rac1-PI3K-Akt pathway and the MyD88-dependent pathway. In contrast, Gram-negative stimulation-induced downregulation of miR-9-5p, miR-27b-3p, miR-93-5p, and miR-106b-5p is known to target key members of the Rac1-PI3K-Akt pathway and the MyD88-dependent pathway. These results, taken together, point to a fine-tuning of macrophage polarization by TLR-induced changes in macrophage miRNA profiles. Here, the miRNA-mediated priming of M1 differentiation seems to differ in the Gram-positive and Gram-negative settings in terms of the mechanism and miRNAs involved.
Insights
Macrophage polarization is crucial for health. This study reveals distinct microRNA (miRNA) profiles triggered by Gram-positive and Gram-negative bacteria, fine-tuning immune responses via key signaling pathways.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Macrophage polarization is vital for immune responses and pathogen control.
- Regulation occurs at transcriptional and posttranscriptional levels, but mechanisms remain unclear.
- MicroRNAs (miRNAs) are key posttranscriptional regulators influencing cellular processes.
Purpose of the Study:
- To investigate the role of miRNAs in macrophage polarization induced by bacterial stimuli.
- To elucidate the specific miRNA profiles associated with Gram-positive versus Gram-negative bacterial exposure.
- To understand how these miRNA changes impact key immune signaling pathways.
Main Methods:
- Co-culture of macrophages with viable Gram-positive and Gram-negative bacteria.
- Analysis of miRNA expression profiles following bacterial stimulation.
- Bioinformatic prediction and validation of miRNA targets in relevant signaling pathways.
Main Results:
- Gram-positive bacteria increased expression of miR-7a-5p, miR-148a-3p, miR-155-5p, and miR-351-5p.
- Gram-negative bacteria decreased expression of miR-9-5p, miR-27b-3p, miR-93-5p, and miR-106b-5p.
- Upregulated and downregulated miRNAs target inhibitory mediators in the Rac1-PI3K-Akt and MyD88-dependent pathways.
Conclusions:
- Toll-like receptor (TLR)-induced changes in macrophage miRNA profiles fine-tune M1 polarization.
- Distinct miRNA-mediated mechanisms are involved in responding to Gram-positive and Gram-negative bacteria.
- This highlights a sophisticated layer of immune regulation at the posttranscriptional level.
