Aggrecan deficiency does not increase susceptibility to estrogen-induced growth plate senescence.

In growing children, estrogen accelerates skeletal maturation, leading to advanced bone age, earlier growth cessation, and epiphyseal fusion. Children with heterozygous pathogenic variants in the aggrecan gene (ACAN) typically exhibit postnatal growth failure, advanced bone age, and premature growth cessation. To investigate whether accelerated skeletal maturation in aggrecan deficiency reflects increased sensitivity to estrogen-induced growth plate senescence, we used a mouse model carrying a heterozygous truncating variant in Acan (Acan +/-). Consistent with the human phenotype, these mice display postnatal growth failure and early growth cessation. Seven-week-old ovariectomized (OVX) wild-type and Acan +/- mice received weekly estradiol cypionate (0.15 µg/g) or vehicle treatment for 4 weeks. As expected, OVX reduced and estradiol increased uterine weights in both genotypes. In wild-type mice, estradiol treatment significantly reduced tibial growth and several structural markers of growth plate function. In Acan +/- mice, fewer parameters were significantly affected by estradiol treatment. Importantly, we found no evidence that aggrecan deficiency increases susceptibility to estrogen-induced growth plate senescence. These findings challenge the hypothesis that accelerated skeletal maturation in ACAN deficiency reflects heightened estrogen sensitivity and instead point to intrinsic abnormalities of growth plate cartilage as a driver of premature growth cessation.