Estrogen promotes the onset and development of idiopathic scoliosis via disproportionate endochondral ossification of the anterior and posterior column in a bipedal rat model

This study aimed to verify the effects of estrogen on the onset and development of adolescent idiopathic scoliosis and the mechanisms associated with these effects by constructing a pubescent bipedal rat model. Experiments were conducted to investigate whether scoliosis progression was prevented by a Triptorelin treatment. One hundred twenty bipedal rats were divided into female, OVX (ovariectomy), OVX + E2, Triptorelin, sham, and male groups. According to a spinal radiographic analysis, the scoliosis rates and curve severity of the female and OVX + E2 groups were higher than those in the OVX, Triptorelin, and male groups. The measurements obtained from the sagittal plane of thoracic vertebrae CT confirmed a relatively slower growth of the anterior elements and a faster growth of the posterior elements between T11 and T13 in the female and OVX + E2 groups than in the OVX and Triptorelin groups. Histomorphometry and immunohistochemistry revealed a significantly longer hypertrophic zone of the vertebral cartilage growth plates that expressed more type X collagen and less type II collagen in the OVX and Triptorelin groups than in the female and OVX + E2 groups. Ki67 immunostaining confirmed an increase in the proliferation of vertebral growth plate chondrocytes in the OVX group compared with the female and OVX + E2 groups. In conclusion, estrogen obviously increased the incidence of scoliosis and curve severity in pubescent bipedal rats. The underlying mechanism may be a loss of coupling of the endochondral ossification between the anterior and posterior columns. Triptorelin decreased the incidence of scoliosis and curve magnitudes in bipedal female rats. Treatments that reduce estrogen levels may prevent the development of spinal curvature associated with adolescent idiopathic scoliosis, curvature of the spine. Estrogen has been linked to scoliosis in the past, but the nature of this relationship remains controversial. Researchers led by Caixia Xu and Peiqiang Su of the First Affiliated Hospital of Sun Yat-sen University in Guangzhou, China, used a rat scoliosis model to assess how the absence of estrogen influences the onset and severity of this disorder. They demonstrate that rats with greatly reduced estrogen levels (resulting from ovary removal) have a lower incidence of scoliosis than untreated females, with affected animals exhibiting milder spinal curvature.The researchers observed similar lower incidence in female rats treated with triptorelin, a drug that dramatically reduces estrogen levels, further supporting a prominent role for this hormone in spinal development.