Selective estrogen receptor modulation prevents scoliotic curve progression: radiologic and histomorphometric study on a bipedal C57Bl6 mice model

Deletion of Pax1 scoliosis-associated regulatory elements leads to a female-biased tail abnormality

Adolescent idiopathic scoliosis (AIS), a sideways curvature of the spine, is sexually dimorphic, with increased incidence in females. A genome-wide association study identified a female-specific AIS susceptibility locus near the PAX1 gene. Here, we use mouse enhancer assays, three mouse enhancer knockouts, and subsequent phenotypic analyses to characterize this region. Using mouse enhancer assays, we characterize a sequence, PEC7, which overlaps the AIS-associated variant, and find it to be active in the tail tip and intervertebral disc. Removal of PEC7 or Xe1, a known sclerotome enhancer nearby, or deletion of both sequences lead to a kinky tail phenotype only in the Xe1 and combined (Xe1+PEC7) knockouts, with only the latter showing a female sex dimorphic phenotype. Extensive phenotypic characterization of these mouse lines implicates several differentially expressed genes and estrogen signaling in the sex dimorphic bias. In summary, our work functionally characterizes an AIS-associated locus and dissects the mechanism for its sexual dimorphism.

Upregulated estrogen receptors impairs myogenesis and elevates adipogenesis related factor levels in the paravertebral muscles of patients with idiopathic scoliosis

The prevalence of idiopathic scoliosis (IS) is 2-3% worldwide and is more common in girls. Estrogen receptors (ERs) is supposed to be related to sex differences and development of IS. Meanwhile, paravertebral muscle (PVM) abnormalities play important roles in the pathogenesis of IS. But the changes of ERs between the PVMs from IS patients and controls, and the mechanism by which ERs may affect IS patients remain unclear. Thus, the expression levels of ERs, myogenesis regulator (MYOG) and adipogenesis related factors (CEBPA, PPARγ, FABP4), as well as morphological changes in the PVMs and primary skeletal muscle mesenchymal progenitor cells (hSM-MPCs) of IS patients and controls were investigated. Increased expression levels of ERs and CEBPA, PPARγ, FABP4, together with severe myofiber necrosis and fat infiltration, were found in the PVMs of IS patients. Meanwhile, upregulated ERs, FABP4 and CEBPA, downregulated MYOG and impaired myogenesis were also revealed in the hSM-MPCs of IS patients compared with those of controls. Upregulation of ERs inhibited myogenesis but increased expression of CEBPA and FABP4 in C2C12 myoblasts. Nevertheless, treatment of ER antagonist increased expression of MYOG, enhanced myogenesis and decreased expression of CEBPA and FABP4 in skeletal muscle cells of IS patients. Therefore, our study suggested that PVMs specific upregulation of ERs could impair myogenesis and increase the expression of adipogenesis related factors, further leading to PVMs abnormalities in IS patients.

Deletion of Pax1 scoliosis-associated regulatory elements leads to a female-biased tail abnormality

Adolescent idiopathic scoliosis (AIS), a sideways curvature of the spine, is sexually dimorphic, with increased incidence in females. A GWAS identified a female-specific AIS susceptibility locus near the PAX1 gene. Here, we used mouse enhancer assays, three mouse enhancer knockouts and subsequent phenotypic analyses to characterize this region. Using mouse enhancer assays, we characterized a sequence, PEC7, that overlaps the AIS-associated variant, and found it to be active in the tail tip and intervertebral disc. Removal of PEC7 or Xe1, a known sclerotome enhancer nearby, and deletion of both sequences led to a kinky phenotype only in the Xe1 and combined (Xe1+PEC7) knockouts, with only the latter showing a female sex dimorphic phenotype. Extensive phenotypic characterization of these mouse lines implicated several differentially expressed genes and estrogen signaling in the sex dimorphic bias. In summary, our work functionally characterizes an AIS-associated locus and dissects the mechanism for its sexual dimorphism.

Cerebrospinal fluid velocity changes of idiopathic scoliosis: a preliminary study on 3-T PC-MRI and 3D-SPACE-VFAM data

OBJECTIVES

To the best of our knowledge, there is no study on 3-Tesla (3-T) phase-contrast MRI (PC-MRI) and three-dimensional sampling perfection with application-optimized contrasts using different flip-angle evolutions (3D-SPACE-VFAM) in the evaluation of idiopathic scoliosis. This study aimed to investigate CSF abnormalities in the scoliotic spine using 3-T PC-MRI and 3D-SPACE-VFAM techniques.

METHODS

Thirty-four patients and 14 controls were examined with spinal PC-MRI and T2-weighted 3D-SPACE-VFAM techniques. Inter- and intra-reader agreements of flow-void phenomenon on 3D-SPACE-VFAM images, and velocity values on PC-MRI data were also evaluated.

RESULTS

There are statistically significant differences between scoliosis and control groups based on the highest and mean peak velocity values on PC-MRI images (p = 0.005 and p = 0.023, respectively). The main thoracic (MT) group's highest peak CSF velocity values were higher than the control group (p = 0.022). There is a significant difference between the patient and control groups regarding flow-void phenomenon scores on 3D-SPACE-VFAM images (p = 0.036). Inter- and intra-reader agreement values related to PC-MRI velocity measurements were perfect for all PC-MRI readings. Inter- and intra-reader agreement values of the flow-void phenomenon scores were moderate.

CONCLUSIONS

Our study has led us to conclude that idiopathic scoliosis is associated with CSF flow disturbances in parallel with the literature. MRI can demonstrate these abnormalities in a non-invasive and radiation-free way.

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.

Minodronate treatment improves low bone mass and reduces progressive thoracic scoliosis in a mouse model of adolescent idiopathic scoliosis

Recent studies have shown an association between osteopenia and adolescent idiopathic scoliosis (AIS) and implied that osteopenia plays a causative role in AIS development. This study aimed to determine if minodronate (MIN) treatment could prevent curve progression by increasing bone mass in a thoracic restraint (TR) mouse model, which develops causes the development of thoracic scoliosis similar to human AIS. A total of 100 young female C57BL6J mice were divided into four groups: (1) control with vehicle (CON/VEH; n = 20), (2) control with MIN (CON/MIN; n = 20), (3) TR with vehicle (TR/VEH; n = 30), or (4) TR with MIN (TR/MIN; n = 30). MIN (0.01 mg/kg/week) and vehicle were administered intraperitoneally to their respective groups. TR was performed at age 4 weeks, and the mice were sacrificed at age 9 weeks. Body weights, spine radiographs, femoral bone mineral density (BMD), serum bone marker levels, and histomorphometry of the cancellous bone of the thoracic vertebrae were analyzed. TR significantly reduced weight gain in the TR/VEH group relative to the CON/VEH group. TR also induced osteoporosis with accelerated bone resorption, as indicated by decreases in femoral BMDs and thoracic cancellous bone volume and increases in serum bone resorption marker levels and histomorphometric resorption parameters in the TR/VEH group. MIN partially improved body weight gain and improved poor bone structure relative to the TR/VEH group by suppressing high bone resorption in the TR/MIN mice. MIN significantly reduced the curve magnitudes, as indicated by a 43% lower curve magnitude in the TR/MIN mice than in the TR/VEH mice (17.9 ± 8.9° vs. 31.5 ± 13.1°; p< 0.001). The administration of MIN increased bone mass and reduced the severity of scoliosis in the TR mice. MIN was suggested as a possible inhibitor of scoliosis development.