(A) To determine if annexin 2 is able to prevent degradation of CXCL12, biotinylated CXCL12 (bCXCL12) was incubated with annexin 2 for 2.5h at 4°C, and then incubated with elastase or CD26/dipeptidyl peptidase IV. Degradation of bCXCL12 was determined by Western blots. (B) Identical studies were performed as reported for (A), however in this case the Western blots were stained for annexin 2. (C-G) To validate that annexin 2 does not regulate CXCL12 degradation, anxa2+/+ and anxa2−/− animals were administered G-CSF or vehicle (0.9% saline) by intraperitoneal injection at 250μg/kg (100 μl) per day for 5 days. The bones were harvested and processed for (C) immunohistochemistry (original magnification at 40x, Bar = 100 microns) or (D) Real time RT-PCR was performed to determine annexin 2 levels. (E) Representitive immunohistochemistry for CXCL12 was performed (original magnification at 40x. Bar = 100 microns). (F) CXCL12 mRNA was examined by real time RT-PCR. (G) CXCL12 expression in the marrow extracellular fluids was evalulated by Elisa. Data are presented as the mean ± standard error of the mean. *P<0.05 as determined by Student-T test.