ABSTRACT
Biologics can improve bone formation, but may diffuse away from sites of therapeutic need. We developed a click-chemistry hydrogel that rapidly polymerizes in situ to control delivery of biologics during post-suturectomy resynostosis in 21-day-old male mice. Here, we used this model to determine the role of angiogenesis in post-suturectomy resynostosis and examine whether controlled release of angiogenesis inhibitors could delay bone regeneration. Hydrogels [DB-co-PEG/poly (TEGDMA)-co-(N3-TEGDMA)] were produced containing anti-angiogenic compounds [anti-VEGFA-antibody or hypoxia inducible factor 1α-inhibitor topotecan]. Bioactivity in vitro was assessed by tube length and branching points of endothelial cells in hydrogel-conditioned media. In vivo effects were examined 14 day post-suturectomy, based on the temporal analysis of angiogenic mRNAs during resynostosis following posterior frontal suture removal. MicroCT was used to quantify angiogenesis in contrast-agent-perfused blood vessels and bone defect size in defects receiving hydrogel, anti-VEGFA/hydrogel, or topotecan/hydrogel. Shorter endothelial tube length and less branching were seen in inhibitor-conditioned media (topotecan > AbVEGFA). In vivo, both compounds inhibited angiogenesis compared with hydrogel-only. Anti-VEGFA/hydrogel reduced resynostosis compared with empty defects, but topotecan/hydrogel blocked bone regeneration. We demonstrate that anti-angiogenic compounds can be incorporated into a spontaneously polymerizing hydrogel and remain active over 14 days in vitro and in vivo. Moreover, bone formation can be delayed by inhibiting neovascularization, suggesting possible use as a therapeutic to control resynostosis following suturectomies and potential applications in other conditions where rapid osteogenesis is not desired. © 2017 Wiley Periodicals Inc. J Biomed Mater Res Part A: 105A: 2742-2749, 2017.
Subject(s)
Angiogenesis Inhibitors/administration & dosage , Bone Regeneration/drug effects , Craniosynostoses/therapy , Delayed-Action Preparations/chemistry , Hydrogel, Polyethylene Glycol Dimethacrylate/chemistry , Osteogenesis/drug effects , Polyethylene Glycols/chemistry , Polymethacrylic Acids/chemistry , Angiogenesis Inhibitors/pharmacology , Animals , Craniosynostoses/complications , Disease Models, Animal , Drug Delivery Systems , Male , Mice, Inbred C57BL , Topotecan/administration & dosage , Topotecan/pharmacology , Vascular Endothelial Growth Factor A/antagonists & inhibitorsABSTRACT
Craniosynostosis is the premature fusion of cranial sutures, which can result in progressive cranial deformations, increased intracranial pressure, and restricted brain growth. Most cases of craniosynostosis require surgical reconstruction of the cranial vault with the goal of increasing the intracranial volume and correcting the craniofacial deformities. However, patients often experience rapid post-operative bone regrowth, known as re-synostosis, which necessitates additional surgical intervention. Bone morphogenetic protein (BMP) inhibitors have tremendous potential to treat re-synostosis, but the realization of a clinically viable inhibitor-based therapeutic requires the development of a delivery vehicle that can localize the release to the site of administration. Here, we present an in situ rapidly crosslinking injectable hydrogel that has the properties necessary to encapsulate co-administered proteins and demonstrate that the delivery of rmGremlin1 via our hydrogel system delays bone regrowth in a weanling mouse model of re-synostosis. Our hydrogel is composed of two mutually reactive poly(ethylene glycol) macromolecules, which when mixed crosslink via a bio-orthogonal Cu free click reaction. Hydrogels containing Gremlin caused a dose dependent inhibition of bone regrowth. In addition to craniofacial applications, our injectable click hydrogel has the potential to provide customizable protein, small molecule, and cell delivery to any site accessible via needle or catheter.
Subject(s)
Bone Development/drug effects , Craniosynostoses/drug therapy , Drug Carriers/chemistry , Hydrogel, Polyethylene Glycol Dimethacrylate/chemistry , Intercellular Signaling Peptides and Proteins/administration & dosage , Polyethylene Glycols/chemistry , Animals , Click Chemistry , Copper/chemistry , Craniosynostoses/pathology , Injections , Intercellular Signaling Peptides and Proteins/therapeutic use , Male , Mice , Mice, Inbred C57BL , PolymerizationABSTRACT
The interrelationships among suture fusion, basicranial development, and subsequent resynostosis in syndromic craniosynostosis have yet to be examined. The objectives of this study were to determine the potential relationship between suture fusion and cranial base development in a model of syndromic craniosynostosis and to assess the effects of the syndrome on resynostosis following suturectomy. To do this, posterior frontal and coronal suture fusion, postnatal development of sphenooccipital synchondrosis, and resynostosis in Twist1(+/+) (WT) and Twist1(+/-) litter-matched mice (a model for Saethre-Chotzen syndrome) were quantified by evaluating µCT images with advanced image-processing algorithms. The coronal suture in Twist(+/-) mice developed, fused, and mineralized at a faster rate than that in normal littermates at postnatal days 6-30. Moreover, premature fusion of the coronal suture in Twist1(+/-) mice preceded alterations in cranial base development. Analysis of synchondrosis showed faster mineralization in Twist(+/-) mice at postnatal days 25-30. In a rapid resynostosis model, there was an inability to fuse both the midline posterior frontal suture and craniotomy defects in 21-day-old Twist(+/-) mice, despite having accelerated mineralization in the posterior frontal suture and defects. This study showed that dissimilarities between Twist1(+/+) and Twist1(+/-) mice are not limited to a fused coronal suture but include differences in fusion of other sutures, the regenerative capacity of the cranial vault, and the development of the cranial base.
