Ghrelin alleviated TiO NPs-induced inhibition of endochondral osteogenesis and promoted longitudinal growth of long bones in juvenile rats via Wnt/β-catenin signaling pathway.

Titanium dioxide nanoparticles (TiO NPs) are widely used in children's daily necessities and foods, and their health hazards to children have attracted particular attention. Childhood is a critical time for accelerated bone growth and development. Current studies revealed that TiO NPs exposure causes bone damage in juvenile rats; however, the underlying mechanism is unknown. Ghrelin is a polypeptide hormone that is considered to be a candidate factor for regulating bone growth and development. In this research, 3-week-old juvenile male rats were administered 0, 100 or 200 mg/kg TiO NPs and 50 μg/kg ghrelin for 4 weeks to explore the underlying mechanism of TiO NPs-induced bone damage, and the protective effect of ghrelin. Our results revealed that TiO NPs resulted in decreased synthesis of bone growth-related hormones, disturbed bone metabolism, and destruction of bone structure. Further mechanism studies showed that TiO NPs inhibited Wnt/β-catenin pathway, reduced collagen synthesis, inhibited chondrocyte proliferation and differentiation, promoted chondrocyte apoptosis, and inhibited endochondral osteogenesis, ultimately leading to long bone longitudinal growth retardation and osteoporosis. Ghrelin alleviated the negative effects of TiO NPs-induced bone growth in juvenile rats by upregulating the Wnt/β-catenin signaling pathway. This study provided a reference for the clinical treatment of growth retardation and idiopathic short stature in juvenile children caused by environmental pollutants.