Delivery of transforming growth factor-β3 plasmid in a collagen gel inhibits cranial suture fusion in rats

Objective: Studies described in this paper were designed to test the hypothesis that an increase in nonviral, plasmid-encoded Tgf-β3 production, localized to the rat posterior frontal suture, prevents programmed suture fusion. Design: We developed a gene delivery system based on a dense collagen gel to deliver nonviral plasmids that encode for Tgf-β3. Studies were performed to test the ability of this system to rescue rat cranial suture fusion in vitro and in vivo. Immunohistochemical studies were conducted to characterize the possible mechanisms by which increased production and presence of Tgf-β3 protein interferes with suture fusion. Results: Posterior frontal sutures in the Tgf-β3 plasmid-treated group exhibited 77% to 85% less bony bridging than the collagen control and untreated groups after 15 days in culture. In animals treated with Tgf-β3 plasmid or Tgf-β3 protein, there was a significant reduction in suture fusion in the middle region of the posterior frontal sutures when compared with control groups. In this region the Tgf-β3 plasmid-treated group revealed 70% to 75% less bony bridging than control groups in vivo. Conclusions: Collagen gel can be formulated to provide release of nonviral plasmid DNA that results in cell transfection and elevated Tgf-β3 protein production. Tgf-β3 is an important regulator of suture fusion, and an increase in plasmid-encoded Tgf-β3 protein is effective in inhibiting programmed suture fusion in rats.