Figure 1.

Localization of NGF and p75 expressing cells in the distal head of the non-decalcified young mouse femur. An image of a Safranin O-stained section of the distal end of the femur (A) and a confocal image (B) showing the localization of NGF (yellow) and p75 (green) expressing cells in a section that was serially adjacent to (A). Note that in the confocal image shown in (B), the same section has simultaneously been stained with antibodies raised against NGF and p75. The NGF expressing cells are confined to a subpopulation of cells located at the subchondral zone/articular cartilage interface (B), whereas cells that robustly express p75 are located in deep and middle zone of the articular cartilage. Note that the high-power image of NGF-expressing cells shown in (C), which were obtained in tissue sections adjacent to that shown in (B), suggests these NGF+ cells do not have the morphology of endothelial cells, blood vessel-associated cells, or chondrocytes, whereas the p75 expressing cells in the deep (D) and middle (E) zone of the articular cartilage have the location and morphology of chondrocytes. Also note that p75 expressing nerve fibers were not observed near the NGF+ cells in the subchondral bone. The H&E stained section in (A) is 20 µm thick and the z-stacks of the confocal images shown in (B–E)=60 µm.