Lower WNT16 expression in patients with adolescent idiopathic scoliosis - potential link to lower bone mass in AIS?

Adolescent Idiopathic Scoliosis (AIS) occurs during pubertal rapid growth period and is closely associated with low bone mass. The underlying mechanisms for systemic low bone mass in AIS remains unclear. Wnt signalling pathway is one of the important pathways regulating bone metabolism and influencing bone strength, its family member Wnt16 associates with lower bone mineral density (BMD) in late adulthood, and plays key regulatory role in determining cortical bone quality in adult mice. Our randomized control trial have reported vitamin D (VitD) supplementation significantly improved bone mass and reduced the risk of curve progression in AIS. A case-control study and animal study were employed to answer if WNT16 is associated with the abnormal bone quality in AIS and if the effect of VitD supplementation is associated with Wnt16, respectively. A cohort of 161 AIS and control female subjects were recruited for measurement of anthropometric parameters, bone qualities, and circulating Wnt16 level. In animal study, WT and Wnt16 gKO mice were both subjected to special VitD diet from week 4 and terminated at week 7 and 10 for samples harvesting. AIS showed significantly lower BMD, circulating WNT16 level, and elevated serum level of type I procollagen N-terminal propeptide. Wnt16 gKO mice demonstrated lower cortical bone density compared with WT mice from week 7 of age and Wnt16 gKO were less prone to cortical bone loss induced by high dosage VitD diet. Further study on the biological role of WNT16 and crosstalk with VitD metabolism on bone qualities is warranted which might shed light on prognostic gene of osteopenia and new perspectives for potential target to prevent curve progression.