The regulation of pedicle initiation by androgens in sika deer (Cervus nippon).

BACKGROUND: Deer antlers have the potential to contribute to a range of novel biomedical models. Although androgen is undoubtedly an undisputed prerequisite for pedicle initiation (initial stage of antler formation), the molecular mechanisms underlying androgen stimulation remain unclear. METHODS: Four juvenile male deer (Cervus nippon) were selected: one intact individual and three castrated ones. The castrates were further divided to receive either testosterone or vehicle injections. The antlerogenic periosteum (AP) tissues overlying each frontal crest were collected at successive time points for subsequent analyses. Proteomic analysis was performed using two-dimensional difference gel electrophoresis (2D-DIGE), while cell proliferation and differentiation were assessed through ex vivo tissue explant cultures, in vitro osteoblast induction, and transcriptomic analyses. RESULTS: Exogenous androgen induced pedicle initiation. Among the differentially-expressed proteins (DEPs) identified, ACTB, VIM, p53, RNASEL, and CALR were notable for their direct interactions with the androgen receptor (AR). Pathways related to the cell cycle, gene expression, protein metabolism, and signal transduction were found to play key roles in activating pedicle initiation. In serum-free medium, testosterone promoted the proliferation of AP cells in ex vivo tissue explant cultures; however, it showed no effect on osteogenic differentiation of these cells. CONCLUSION: Our findings indicate that testosterone serves as the key factor triggering pedicle initiation. However, this effect likely occurs through the promotion of AP cell proliferation rather than their osteogenic differentiation. Furthermore, the results suggest that CALR may play a pivotal role in regulating the transcription of AR downstream genes during pedicle initiation. These results provide new insights into androgen-regulated mechanisms in deer pedicle initiation.