Vitamin A Deficiency Induces Congenital Vertebral Malformation via Retinoic Acid Signaling Mediated Sclerotome Dysplasia.

Objective: Congenital vertebral malformations (CVMs) arise from abnormal sclerotome development. Our previous study has indicated that vitamin A deficiency (VAD) induced congenital spinal deformity in rats. However, the phenotype observed through x-ray and the mechanism were still unclear.

Methods: Rats in VAD group were fed with a diet without added vitamin A, while rats in control group were fed with a normal diet. After mating, embryos were collected, and neonatal rats were euthanized. Micro-computed tomography and x-ray were utilized to detect the vertebral malformation. We applied whole mount in situ hybridization to visualize the expression patterns of Pax1 and Raldh-2 in embryos. Laser capture microdissection combined RNA-seq of sclerotome was performed.

Results: The incidence of CVMs in neonatal rats was 32.65% in VAD group and 0% in control group. All malformations observed were butterfly vertebrae. In VAD group, we observed downregulation of Pax1 in sclerotome and Raldh-2 in somite. The enriched gene ontology terms were related to developmental process of skeletal system. The enriched pathways were related to osteoblast and osteoclast differentiation, somitogenesis, and retinol metabolism. Real-time quantitative polymerase chain reaction validated that retinoic acid (RA) signaling was downregulated in the sclerotome, leading to the suppression of osteoblast differentiation through a non-Smad-dependent bone morphogenetic protein (BMP) signaling pathway.

Conclusion: We established a VAD-induced CVMs model. Non-Smad-dependent BMP pathway and RA signaling pathway may be related to the pathogenesis of CVMs. Our findings demonstrate that VAD may be one of the causes of CVMs, which is hypothesized to serve as a novel therapeutic target for the nonsurgical treatment of CVMs in the future.