Thiolated bone and tendon tissue particles covalently bound in hydrogels for in vivo calvarial bone regeneration

• Published in: Acta biomaterialia 2020-03, Vol.104, p.66-75
• Main Authors: Townsend, Jakob M., Sali, Goksel, Homburg, Hannah B., Cassidy, Nina T., Sanders, Megan E., Fung, Kar-Ming, Andrews, Brian T., Nudo, Randolph J., Bohnstedt, Bradley N., Detamore, Michael S.
• Format: Article
• Language: English
• Subjects: Aged; Animals; Biocompatibility; Biomedical materials; Bone and Bones - drug effects; Bone and Bones - physiology; Bone cements; Bone demineralization; Bone growth; Bone matrix; Bone Regeneration - drug effects; Calvarial bone; Computed tomography; Cross-Linking Reagents - chemistry; Crosslinking; Defects; Head injuries; Humans; Hyaluronic acid; Hyaluronic Acid - pharmacology; Hydrogel; Hydrogels; Hydrogels - pharmacology; In vivo methods and tests; Male; Middle Aged; Modulus of elasticity; Placement; Polymers; Rats, Sprague-Dawley; Recovery; Regeneration; Regeneration (physiology); Rheology; Shearing; Skull - physiology; Sulfhydryl Compounds - pharmacology; Surgical equipment; Tendons - drug effects; Tendons - physiology; Thiolated bone; Thiolated tendon; Tissues; Traumatic brain injury; Yield stress
• ISSN: 1742-7061; 1878-7568
• DOI: 10.1016/j.actbio.2019.12.035

Bone regeneration of large cranial defects, potentially including traumatic brain injury (TBI) treatment, presents a major problem with non-crosslinking, clinically available products due to material migration outside the defect. Commercial products such as bone cements are permanent and thus not conducive to bone regeneration, and typical commercial bioactive materials for bone regeneration do not crosslink. Our previous work demonstrated that non-crosslinking materials may be prone to material migration following surgical placement, and the current study attempted to address these problems by introducing a new hydrogel system where tissue particles are themselves the crosslinker. Specifically, a pentenoate-modified hyaluronic acid (PHA) polymer was covalently linked to thiolated tissue particles of demineralized bone matrix (TDBM) or devitalized tendon (TDVT), thereby forming an interconnected hydrogel matrix for calvarial bone regeneration. All hydrogel precursor solutions exhibited sufficient yield stress for surgical placement and an adequate compressive modulus post-crosslinking. Critical-size calvarial defects were filled with a 4% PHA hydrogel containing 10 or 20% TDBM or TDVT, with the clinical product DBXⓇ being employed as the standard of care control for the in vivo study. At 12 weeks, micro-computed tomography analysis demonstrated similar bone regeneration among the experimental groups, TDBM and TDVT, and the standard of care control DBXⓇ. The group with 10% TDBM was therefore identified as an attractive material for potential calvarial defect repair, as it additionally exhibited a sufficient initial recovery after shearing (i.e., > 80% recovery). Future studies will focus on applying a hydrogel in a rat model for treatment of TBI. Non-crosslinking materials may be prone to material migration from a calvarial bone defect following surgical placement, which is problematic for materials intended for bone regeneration. Unfortunately, typical crosslinking materials such as bone cements are permanent and thus not conducive to bone regeneration, and typical bioactive materials for bone regeneration such as tissue matrix are not crosslinked in commercial products. The current study addressed these problems by introducing a new biomaterial where tissue particles are themselves the crosslinker in a hydrogel system. The current study successfully demonstrated a new material based on pentenoate-modified hyaluronic acid with thiolated demineralized bone