Inhibition of craniosynostosis and premature suture fusion in <i>Twist1</i> mutant mice with RNA nanoparticle gene therapy

Craniosynostosis is a common birth defect affecting 1 of the 2200 live births causing severe skull and cognitive defects, due to premature cranial suture fusion. The current surgical treatments require invasive calvaria vault remodeling and cranial bone resection in the baby. We demonstrate that inhibition of <i>miR-200a</i> in <i>PMIS-miR-200a</i> mice results in coronal suture fusion (craniosynostosis). Therefore, we use overexpression of <i>miR-200a</i> to prevent suture fusion in <i>Twist1</i> mutant mice, a well-known model for craniosynostosis. We developed a PEGylated-peptide nanoparticle system to deliver plasmid DNA expressing <i>miR-200a</i> directly to the sutures of postnatal day 4 (P4) <i>Twist1</i> mutant mice before suture fusion. Injection of the <i>miR-200a</i> nanoparticles under the scalp before suture fusion at P7 to P10 inhibited suture fusion. Treatments increased Gli1- and Six2-positive suture stem cells and the thickness of the periosteum layer. The treated <i>Twist1^+/-</i> mice increased body weight and were alert and active. We demonstrate an effective noninvasive gene therapy treatment for craniosynostosis.