Expression of neurotrophin-3 in the growing velvet antler of the red deer Cervus elaphus.

Antlers are organs of bone which regenerate each year from the heads of male deer. In addition to bone, support tissues such as nerves also regenerate. Nerves must grow at up to 1 cm/day. The control of this rapid growth of nerves is unknown. We examined the relative expression of neurotrophin-3 (NT-3) mRNA in the different tissues of the growing antler tip and along the epidermal/dermal layer of the antler shaft of the red deer Cervus elaphus, using semi-quantitative reverse transcription-polymerase chain reaction. Expression in the tip was found to be highest in the epidermal/dermal layer and lowest in the cartilaginous layer in all developmental stages examined. These data correlate well with the density and pattern of innervation of these tissues. Along the epidermal/dermal layer of the antler shaft, expression was highest in the segments subjacent to the tip and lowest near the base, arguing for differences in the temporal expression of NT-3 in these segments. The expression of NT-3 in cells isolated from the different layers of 60-day antlers did not mirror that observed when whole tissues were used and may suggest regional specificity of NT-3 expression within antler tissues.