Effect of exogenous CCL19/CCL21 treatment on the osteogenic potential of AS LT fibroblasts after stimulation for various periods. Five groups were assigned: Grow (standard culture medium), control (osteogenesis-induced culture medium), CCL19 (standard culture medium supplemented with 10 ng/ml CCL19), CCL21 (standard culture medium supplemented with 10 ng/ml CCL21) and CCL19/21 (standard culture medium supplemented with 10 ng/ml CCL19 and 10 ng/ml CCL21). ALL data are compared to the Grow group, and the unpaired t-test was performed. (A) Changes in the mRNA levels of the early bone marker ALP in AS fibroblasts after stimulation for 48 h. The CCL19/CCL21 group displayed the maximal effect (P < 0.01), but the expression of CCL21 did not display a significant change. (B and D) ELISA revealed the secretion of ALP and OCN at various time points (2, 4 or 6 days). (C) Changes in the OCN mRNA levels after CCL19/CCL21 stimulation for 48 h. (E-F) The mRNA levels of the osteogenesis regulators Runx2 and osterix were also up-regulated by CCL19 or CCL21 treatment for 48 h. *P < 0.05; **P < 0.01; n.s. = no significance.