Upregulation of CD44 in the inflamed mouse air pouch injected with synthetic lipid A.

Abstract

To investigate aspects of the inflammatory process of the mouse subcutaneous air pouch -- a facsimile synovial cavity -- induced by injection of lipid A, and to determine the expression and upregulation of CD44 in the lining cell layer of the inflamed air pouch. Histological changes of inner walls in the mouse air pouch were evaluated 1, 3, and 7 days after injection of lipid A. Polymorphonuclear cell infiltration in the lining layer reached the maximum one day after injection of 10 microg of lipid A (10/10 mice in Grade 3; p < 0.01), while mononuclear cell infiltration and lining cell hyperplasia reached the maximum 3 days after injection (5/10 mice in Grade 2; 5/10 in Grade 3; p < 0.05; 39+/-11 layers, p < 0.05, respectively). The number of cell depth of CD44 positive lining layers and interleukin 1alpha (IL-1alpha) positive lining layers reached the maximum 3 days after injection (39+/-7 layers, p < 0.01; 35+/-12 layers, p < 0.05, respectively). These findings suggest that CD44 may have some connection with the proinflammatory cytokine IL-1alpha and induce inflammatory responses in the air pouch injected with lipid A.