TGF-beta1 adenoviral overexpression increases osteogenesis but does not lead to pathologic murine sagittal craniosynostosis

Abstract Introduction: Data indicates that TGF-betas may play an important role in craniosynostosis. In a murine organ culture model, we previously demonstrated that blocking TGF-beta signaling leads to pathologic suture patency. In this study, we investigated both the osteogenic properties of TGF-beta1 and determined whether adenoviral overexpression of TGF-beta1 in a normally patent sagittal (SAG) suture would lead to pathologic suture fusion. Methods: Primary calvarial rat osteoblasts were treated with TGF-beta1 adenovirus or vehicle and cultured for four weeks. Expression of TGF-beta1 was confirmed using quantitative real-time PCR (QRT-PCR) and bone nodule formation assessed with von Kossa staining. The dura mater of 22 day CD-1 mouse calvarial explants were then transfected with adenovirus overexpressing TGF-beta1 or lacZ. SAG sutures were harvested weekly for four weeks and analyzed with H&E as well as beta-galactosidase staining. Results: QRT-PCR data confirmed the marked up regulation of TGF-beta1 mRNA in osteoblasts transfected with the TGF-beta1 overexpression adenovirus. TGF-beta1 adenoviral overexpression led to a 5-fold increase in bone nodule formation compared to untreated osteoblasts. Interestingly TGF-beta1 adenoviral transfection in the underlying dura mater did not lead to pathologic SAG suture fusion in any specimens. Conclusions: TGF-beta1 has potent osteogenic capabilities as demonstrated by a significant increase in bone nodule formation. Although blocking TGF-beta signaling prevents physiologic suture fusion, overexpression of TGF-beta in a normally patent cranial suture does not lead to pathologic craniosynostosis. TGF-beta is potentially necessary but not sufficient in the mechanism of programmed cranial suture fusion.