Characterising skull pathologies in the Sost-deficient mouse for preclinical evaluation of sclerosteosis treatments

Facial paralysis, hearing loss and potentially lethal raised intracranial pressure are primary symptoms of sclerosteosis, an ultra-rare, autosomal recessive high bone mass (HBM) condition that predominantly manifests in skull pathologies. Non-invasive treatment remains an unmet clinical need. Recently, PORCN inhibition has been shown to reduce bone mass in young Sost-deficient (Sost-/-) mice. In this paper, we characterised sclerosteosis skull pathologies at later adult stages using a Sost-/- mouse model, with a view to drug efficacy evaluation. This revealed that male and female 9-month-old Sost-/- mice recapitulate the skull overgrowth and neural impingement of human sclerosteosis. We observed that the foramen magnum was narrowed in Sost-/- mice, and that parietal bone mass and thickness were significantly elevated. Otosclerosis was apparent, and animals exhibited significant hearing loss at age 8-9 months. Further, prominent mandibles highlighted hyperostosis in the jaw. Sexual dimorphism was also evident in the Sost-/- mice, underscoring the importance of including both sexes in HBM studies. This study provides new insight into Sost-/--skull-related pathology and further validates Sost-/- mice as a valuable model for investigating potential treatments for sclerosteosis and other HBM related conditions.