The expression of TNF-α and IL-1β at four weeks after crush injury. At four weeks after crush injury, specimens from both sem (p38+/−) and wt (p38+/+) mice were processed in the same way as shown in Figure 4. Scale bar indicates 50 μm. The ratio of the immunopositive area of (a) TNF-α and (b) IL-1β to the total area of the field was calculated as the immunopositive rate, respectively. Asterisks indicate significant difference between genotypes (*P <0.05) and N.S. indicates no significant difference.