Polypropylene mesh implantation for hernia repair causes myeloid cell-driven persistent inflammation

Area of Science:

• Biomaterials Science
• Immunology
• Surgical Research

Background:

• Polypropylene meshes are widely used for inguinal hernia repair.
• These meshes can elicit foreign body reactions, potentially leading to complications.

Purpose of the Study:

• To functionally characterize myeloid cell-driven inflammation following mesh implantation.
• To elucidate the dynamics and mechanisms of foreign body reactions to implanted biomaterials.

Main Methods:

• Mesh implantation in mice using the onlay technique.
• Analysis of myeloid cell accumulation, phenotype, and spatial distribution.
• Protein mass spectrometry and immunoglobulin deposition assessment.
• Intravital multiphoton microscopy to observe cell motility and recruitment.

Main Results:

• Persistent myeloid cell accumulation and distinct macrophage subsets were observed up to 90 days post-implantation.
• Inflammatory phenotypes were noted in tissue surrounding the biomaterial, while surrounding stroma showed mixed phenotypes.
• Evidence of complement activation, cytokines, and increased immunoglobulin deposition indicated humoral immune responses.
• Myeloid cell recruitment, partly CCR2-dependent, was linked to fibroblast proliferation.

Conclusions:

• Mesh implantation triggers a sustained foreign body reaction dominated by specific macrophage subsets.
• These macrophages play a crucial role in modulating the tissue environment and immune responses around the implant.
• Understanding these mechanisms offers insights into optimizing biomaterial performance and patient outcomes.