Prolonged active bone remodeling due to local BDNF.

Immunohistochemical staining of cathepsin K, ALP and osteopontin at day 7 (A) and day 28 (B) after osteotomy. Many cathepsin K-positive osteoclasts appeared in the control group at day 7. In contrast, osteopontin-positive lines were prominent in the BDNF-treated bone surface (A, C). At day 28, cathepsin K-positive osteoclasts were scattered on the surface of newly formed bone and bone lacunae in the BDNF group. In addition, osteoblast-lineage cells were strongly immunopositive for ALP, and OPN-positive new bone matrix (arrows) was significantly thicker in the BDNF group (B, C). Bars, 50 μm.