Cellular FXIII in Human Macrophage-Derived Foam Cells

Area of Science:

• Biochemistry
• Cell Biology
• Pathology

Background:

• Macrophages are key cells in atherosclerotic plaques and can transform into foam cells.
• Coagulation factor XIII-A (FXIII-A) is a transglutaminase involved in protein cross-linking.
• FXIII-A's role in macrophage foam cell formation and its contribution to plaque structure are not fully understood.

Purpose of the Study:

• To investigate the expression and intracellular content of FXIII-A during macrophage foam cell transformation.
• To determine if FXIII-A plays a role in the structural changes of atherosclerotic plaques.
• To compare FXIII-A changes in macrophage-derived foam cells versus vascular smooth muscle cell-derived foam cells.

Main Methods:

• Cultured human macrophages were transformed into foam cells using oxidized LDL (oxLDL).
• Immunofluorescence staining for FXIII-A and Oil Red O for oxLDL were used to assess FXIII-A retention.
• ELISA and Western blotting were employed to quantify intracellular FXIII-A levels.
• Antibody labeling of iso-peptide bonds demonstrated FXIII-A's cross-linking activity in plaque tissue.

Main Results:

• FXIII-A was retained in macrophages during their transformation into foam cells.
• Intracellular FXIII-A content significantly increased in macrophage-derived foam cells.
• This increase in FXIII-A was specific to macrophages, not observed in vascular smooth muscle cells.
• FXIII-A-containing macrophages were abundant in atherosclerotic plaques and showed evidence of cross-linking activity.

Conclusions:

• Macrophage foam cells accumulate FXIII-A, suggesting a role in plaque stabilization.
• FXIII-A's cross-linking activity within foam cells may contribute to atherosclerotic plaque structurization and lipid core formation.