Our previous studies discovered that prenatal
caffeine exposure (PCE) could induce
intrauterine growth retardation (IUGR) and long-
bone dysplasia in offspring rats, accompanied by maternal
glucocorticoid over-exposure. This study is to explore whether intrauterine high
glucocorticoid level can cause endochondral ossification retardation and clarify its molecular mechanism in PCE fetal rats. Pregnant Wistar rats were intragastrically administered 30 and 120 mg/kg day of
caffeine during gestational days (GDs) 9-20, then collected fetal serum and femurs at GD20. In vitro, primary chondrocytes were treated with
corticosterone (0-1250 nM),
caffeine (0-100 μM),
mitogen-inducible gene 6 (Mig-6)
siRNA and
epidermal growth factor receptor (EGFR)
siRNA, respectively, or together. Results showed that the hypertrophic chondrocytes zone (HZ) of PCE fetal femur was widened. Meanwhile, the expression levels of chondrocytes terminal differentiation genes in the HZ were decreased, and the chondrocytes apoptosis rate in the HZ was decreased too. Furthermore, PCE upregulated Mig-6 and suppressed EGFR expression in the HZ. In vitro, a high-concentration
corticosterone (1250 nM) upregulated Mig-6 expression, inhibit EGFR/
c-Jun N-terminal kinase (JNK) signaling pathway and terminal differentiation genes expression in chondrocytes and reduced cell apoptosis, and these above alterations could be partly reversed step-by-step after Mig-6 and EGFR knockdown. However,
caffeine concentration dependently increased chondrocyte apoptosis without significant changes in the expression of terminal differentiation genes. Collectively, PCE caused endochondral ossification retardation in the female fetal rats, and its main mechanism was associated with
glucocorticoid (rather than
caffeine)-mediated chondrocyte terminal differentiation suppression by the upregulation of Mig-6 and then inhibition of EGFR/JNK pathway-mediated chondrocyte apoptosis.