In vitro regulation of expression of cartilage-derived morphogenetic proteins by growth hormone and insulinlike growth factor 1 in the bovine cricoidchondrocyte

Objectives: To delineate the endogenous growth factors that regulate cricoi d cartilage growth at the molecular level. Specifically, to attempt to esta blish the presence of cartilage-derived morphogenetic proteins (CDMPs), car tilage-specific members of the bone morphogenetic protein family, in newbor n bovine cricoid chondrocytes and to assess the expression of these endogen ous growth factors with the addition of exogenous growth hormone or insulin like growth factor 1 in an in vitro chondrocyte culture model. Methods and Design: Basic science molecular biologic research methods, incl uding high-density monolayer and explant chondrocyte cultures with extracti on of messenger RNA and quantitation via Northern blot hybridization via ra diolabeled complementary DNA probes. Setting: Intramural basic science research laboratory. Results: Both CDMP-1 and CDMP-2 were found in newborn cricoid chondrocytes. Addition of exogenous growth hormone did not appear to influence the expre ssion of CDMP-1 or CDMP-2. Addition of exogenous insulinlike growth factor 1 appeared to down-regulate the expression of CDMP-1 but had no effect on t he expression of CDMP-2. No major differences in CDMP level of expression w ere no ted between high-density monolayer cultures vs explant cultures. No tissue specificity differences were noted in regulation of CDMPs between cr icoid and articular chondrocytes. Conclusions: Our preliminary studies indicate the presence of endogenous mo rphogenetic proteins in newborn bovine cricoid chondrocytes. These novel po lypeptide hormones (CDMP-1 and CDMP-2) have not been previously reported in laryngeal cartilage chondrocytes. Change in level of transcription of thes e morphogenetic proteins under various in vitro conditions suggests that th ese proteins are subject to regulation and/or play a regulatory role in cri coid chondrocyte growth and differentiation. Further experimentation is nee ded to confirm these findings.