Detection of growth factors and proto-oncogene mRNA in the growing tip of red deer (Cervus elaphus) antler using reverse-transcriptase polymerase chain reaction (RT-PCR).

Deer antler is a unique mammalian organ that has an annual cycle of regeneration. The antler grows very rapidly from the tip at up to 1 cm/day in red deer for a 90- to 120-day period. It is hypothesised that locally produced growth factors are required to control and stimulate this growth. The tip of the growing antler from animals whose antlers had been growing for 30, 60, or 90 days was dissected into four zones: epidermis/dermis, reserve mesenchyme, precartilaginous, and cartilaginous. Total RNA was extracted, and the presence of various growth factors and proto-oncogenes was detected using RT-PCR, IGF-I, IGF-II, TGF beta 1, TGF beta 2, c-fos, c-myc, and beta-actin were all present as single bands of the expected molecular weight in the four zones of the antler at each stage of growth. There were higher levels of IGF-I, TGF beta 2, and c-myc relative to beta-actin in the epidermis/dermis layer than in the other three zones. There were no differences in the expression of any of the genes between the three stages of growth. The presence of TGF beta 3 cannot be confirmed since multiple bands were seen in all antler tissues. A single band of the expected size for TGF alpha was seen only in the epidermal/dermal layer of the antler, with multiple bands of different molecular weight being detected in the other zones of the antler. This work has demonstrated the presence of multiple growth factors in the growing deer antler and supports the hypothesis that paracrine/autocrine stimulation is important for regulating antler growth.