Cy. Li et al., Effects of insulin-like growth factor 1 and testosterone on the proliferation of antlerogenic cells in vitro, J EXP ZOOL, 284(1), 1999, pp. 82-90
Androgen hormones and growth factors are implicated in pedicle formation an
d antler transformation in deer. The potential to form a pedicle and an ant
ler is only found in the antlerogenic periosteum (AP) overlying the presump
tive antler growth region. Histological studies (Li and Suttie, '94) showed
that AP consists of an inner cellular layer and an outer fibrous layer. Pe
dicle and antler are mainly derived from the cellular layer cells of the AP
. Ossification takes place in four stages: intramembranous (IMO), transitio
nal (OPC), pedicle endochondral (pECO) and antler endochondral (aECO). Howe
ver, the precise mechanism whereby androgen hormones and growth factors con
trol pedicle and antler formation is unknown. The aim of this study was to
use cell culture techniques to investigate how testosterone and IGF1 affect
s the proliferation of antlerogenic cells from the four ossification stages
of pedicle/antler in vitro. The results showed that in serum-free medium I
GF1 stimulated the proliferation of antlerogenic cells from all four ossifi
cation stages in a dose-dependent manner. In contrast, testosterone alone d
id not show any mitogenic effects on these antlerogenic cells. However, in
the presence of IGF1, testosterone increased proliferation of the antleroge
nic cells from the IMO and the OPC stages (pedicle tissue), and reduced pro
liferation of the antlerogenic cells from transformation point (TP) and aEC
O stages (antler tissue). Therefore, the results from the present in vitro
study support the in vivo findings that androgen hormones stimulate pedicle
formation but inhibit antler growth. The change in the mitogenic effects o
f testosterone on antlerogenic cells from positive to negative occurs appro
ximately at the change in ossification type from OPC to pECO. Therefore, th
ese results reinforce the hypothesis that the transformation from a pedicle
to an antler takes place at the time when the ossification type changes fr
om OPC to pECO rather than at the time when the pedicle grows to its full s
pecies-specific height. J. Exp. Zool. 284:82-90, 1999. (C) 1999 Wiley-Liss,
Inc.