Macrophage-related immune responses to polyetherketoneketone bone implants: Single-cell transcriptome analysis

Area of Science:

• Biomaterials Science
• Immunology
• Regenerative Medicine

Background:

• Polyetherketoneketone (PEKK) is a potential alternative to titanium (Ti) for bone implants.
• PEKK's inferior osseointegration compared to Ti is linked to poor understanding of early immune responses.

Purpose of the Study:

• Investigate distinct early macrophage responses to Ti and PEKK implants.
• Characterize macrophage polarization and intercellular interactions in the bone marrow microenvironment.

Main Methods:

• Single-cell RNA sequencing of bone marrow post-implantation.
• Analysis of macrophage phenotype, polarization dynamics, and cell-cell crosstalk.

Main Results:

• Ti implants recruited CD99+ macrophages, creating an anti-inflammatory environment promoting osseointegration.
• PEKK implants recruited ICAM1+ macrophages, causing inflammation and hematopoietic stem cell (HSC) stress.
• Ti facilitated CD99-dependent macrophage-T cell crosstalk (Th2 response); PEKK induced ICAM1-driven HSC necroptosis.

Conclusions:

• Early macrophage responses dictate clinical outcomes for bone implant materials.
• Material-dependent macrophage polarization (CD99+ vs. ICAM1+) is key to osseointegration differences.
• PEKK's inflammatory response disrupts hematopoietic homeostasis, unlike Ti.