Purpose: To explore the role of lumican in polymorphonuclear neutrophil granulocyte (PMN) migration in corneal stroma after bacterial infection.
Methods: Lumican wild-type (Lum+/+) green fluorescent protein (GFP)-positive PMNs were transplanted into lumican knockout (Lum−/−) and heterozygous control (Lum+/−) mice followed by corneal stromal injection of Staphylococcus aureus conjugated with pH-sensitive dye that expresses fluorescein when trapped in lysosomes.
Results: In Lum+/− corneal stroma, many small triangular or spindle-shaped cells labeled by pH-sensitive dye appeared within 10 minutes after S. aureus injection, whereas in Lum−/− corneal stroma, large cells or large cell complexes (morphologically, macrophages and macrophage-derived lymphatic vessels) appeared. Transplanted GFP-positive PMNs appeared in Lum+/− corneal stroma within 1 hour after S. aureus injection and were concentrated in the central injection area at 2 hours after injection. In Lum−/−, on the other hand, relatively few GFP-positive cells were observed in corneal stroma even ≤ 24 hours after injection of bacteria.
Conclusions: Extracellular lumican is required for PMN migration in corneal stroma. In lumican null mouse cornea, macrophages and macrophage-derived lymphatic vessels act as first defense against staphylococcal infection.