Estrogen receptor alpha (ERα) expression in cartilage affects local gene expression of the neutrophil chemokine CXCL1 but has no effect on systemic neutrophil migration capacity. Col2α1-ERα-/- and wild-type (WT) littermates were treated with placebo or estrogen (E2) (0.83 μg/day) and induced with antigen-induced arthritis. Expression of (A) Cxcl1 and (B) Cxcl5 in the epiphyseal part of the femur. The mRNA level of each gene was adjusted for expression of 18S rRNA. (C) Neutrophil migration was evaluated by analysis of the number of peritoneal exudate cells after induction of inflammation in the peritoneal cavity by using uric acid. *P <0.05, Student t test. Results are shown as mean ± standard error of the mean (n = 4-8).