CXCL12 circadian fluctuations in CXCL12 concentration occur independent of endothelial CXCR7.

A, Blood (left), femur (center), and tibia (right) CXCL12 levels vary 2-fold between 5 am and 8 pm. Error bars represent SEM of 5 repeated measurements per group of mice. B, CXCL12 isoform-specific human blood variations that we use in our model (Eq (1)). CT 24 corresponds to 9 pm while CT 12 corresponds to 9 am. For humans, we offset the time at which the maximum and minimum blood levels occur in the mice by 12 hours because mice are nocturnal. Mice and humans exhibit CXCL12 blood level maxima at night and in the morning, respectively.