Temporal regulation of the Ihh-PTHrP signaling axis modulates condylar development via angiogenesis

Vismodegib, a Smoothened (Smo) receptor antagonist, effectively suppresses Hedgehog (Hh) signaling activity during embryonic development and is known to influence craniofacial morphogenesis. However, its specific role in temporomandibular joint (TMJ) development remains unclear. In this study, a single dose of vismodegib (150 mg/kg) was administered to pregnant mice at embryonic day 14.5 (E14.5) to investigate its impact on fetal TMJ morphogenesis. At postnatal day 21, offspring from the treatment group exhibited significantly reduced condylar length and bone surface area density compared to vehicle-treated controls. Despite no observable differences in cellular proliferation or apoptosis-as assessed by phospho-Histone H3 (PHH3) and TUNEL assays-angiogenic markers, including VEGF, CD31, and CD34, were markedly upregulated in the condylar region of vismodegib-treated mice. Furthermore, at E15.5, expression of key components of the Ihh-PTHrP signaling axis (Gli1, Ptch1, and PTHrP) was significantly downregulated in the experimental group relative to controls. These findings suggest that vismodegib disrupts TMJ development by inhibiting the Ihh-PTHrP signaling pathway, thereby altering angiogenesis in the condyle and ultimately impairing cartilage growth and structural integrity.