Table 1.

Cellular localization of NGF, TrkA, and p75 immunoreactivity in the non-decalcified young mouse femur.

Tissue	NGF	TrkA	p75
Bone
CD31− blood vessel	√
CD31+ blood vessel	√
Subchondral bone	√
Single cells in bone marrow	√
Sensory nerve fibers		√	√
Sympathetic nerve fibers		√	√
Articular cartilage
Chondrocytes			√

Note. Cells that expressed robust NGF immunoreactivity were observed in CD-31− and CD31+ blood vessels, non-CD-31+ cells in subchondral bone and single or small clusters of non-blood vessel-associated cells in the bone marrow. Both TrkA and p75 were abundantly expressed by nerve fibers innervating NGF+ blood vessels in the marrow and periosteum. Robust expression of p75, but not TrkA, was also observed in cells in the deep and middle zone of the articular cartilage. NGF: nerve growth factor; TrkA: tropomyosin receptor kinase A.