H. Messai et al., Articular chondrocytes from aging rats respond poorly to insulin-like growth factor-1: an altered signaling pathway, MECH AGE D, 115(1-2), 2000, pp. 21-37
This study investigates the effect of insulin-like growth factor-1 (IGF-1)
and phorbol 12-myrystate 13-acetate (PMA) on H-3-thymidine. (SO4)-S-35 and
H-3 -glycine incorporations, adenosine 3':5'-cyclic monophosphate (cAMP) pr
oduction and protein kinase C (PKC) activation in cultured rat articular ch
ondrocyte monolayers (RACM) derived from animals of different ages. It was
found that IGF-1 stimulates all these cellular functions in cultures derive
d from all age groups in a concentration dependent manner: although the cel
ls from 14-month old animals responded poorly. IGF-1 also induces in cells
from 1-month old rats an increase in the expression of mRNAs specific for a
ggrecan and type II collagen molecules as shown with RT-PCR. These effects
are mediated via IGF-1 interaction with specific receptors because the mono
clonal antibody against the receptor protein suppresses more than 60% of th
e ligand-induced DNA synthesis. PMA, a direct PKC activator, potentiated IG
F-1-induced effects in all cells but much more strongly in cells from young
than in cells from 14-month old animals. The age-related failure of RACM t
o respond adequately to IGF-1 was correlated with a decrease in IGF-1-induc
ed cAMP production, and IGF-1-induced and PMA-induced PKC activations. Thes
e results show that IGF-1 regulates the synthesis of DNA, proteoglycans (PG
) and collagen II at the level of transcription and suggest that the reduce
d response of cell monolayers derived from 14-month old rats to IGF-1 is pr
obably due to a failure of old cells to adequately transduce IGF-1 receptor
-generated downstream signaling. (C) 2000 Elsevier Science Ireland Ltd. All
rights reserved.