Figure 4: 5-HT₆R disrupted in vivo calvarial bone regeneration and embryonic calvarial bone development.

(A) Scheme for assessing calvarial defect model. After female 8-week-old ICR mice were acclimated for 2 weeks, calvarial bone from female 10-week-old ICR mice was removed, and the calvarial defect was covered for 8 weeks with a bioabsorbable collagen sponge loaded with ST1936. (B) 3D micro CT (μCT) images from sham (control) and ST1936-treated groups were conducted to visualize and quantify calvarial bone regeneration. (C) Quantitative analysis of the relative percentage of new bone formation was performed by 3D μCT imaging and plotted as individual points. (D) H&E-stained images of the calvarial bone (left) and higher magnification images (right). Arrowhead indicates the defect region and arrows indicate width of bone tissue. Scale bars, 50 μm. (E) Scheme for assessing calvarial bone development by SR6. ST1936 (10 mg/kg, ip) or ST1936 (10 mg/kg, ip)/SB258585 (5 mg/kg, ip) were injected once per day at embryonic periods (E) 6, E9, E12, and E15. All mice had pups at E18 and postnatal 1 day (P1) mice were sacrificed. (F,G) P1 mice from each group were photographed (F) and weighed (G). (H) P1 mice were stained with Alizarin Red (red color) and Alcian Blue (blue color). The panels show calvarial bones consisting of paired frontal bones (F), paired parietal bones (P), and interparietal bone (IP). (I–K) The mRNA levels of Runx2 (I), OCN (J), BSP (K) in the calvarial bones of P1 mice were analyzed by real-time PCR and normalized to that of β-actin. Data shown represent the means ± SEM. *p < 0.05, vs. control. ^#p < 0.05, vs. ST1936 alone.