Titanium-Enriched Hydroxyapatite–Gelatin Scaffolds with Osteogenically Differentiated Progenitor Cell Aggregates for Calvaria Bone Regeneration

Abstract

Adequate bony support is the key to re-establish both function and esthetics in the craniofacial region. Autologous bone grafting has been the gold standard for regeneration of problematic large bone defects. However, poor graft availability and donor-site complications have led to alternative bone tissue-engineering approaches combining osteoinductive biomaterials and three-dimensional cell aggregates in scaffolds or constructs. The goal of the present study was to generate novel cell aggregate-loaded macroporous scaffolds combining the osteoinductive properties of titanium dioxide (TiO 2 ) with hydroxyapatite-gelatin nanocomposites (HAP-GEL) for regeneration of craniofacial defects. Here we investigated the in vivo applicability of macroporous (TiO 2 )-enriched HAP-GEL scaffolds with undifferentiated and osteogenically differentiated multipotent adult progenitor cell (MAPC and OD-MAPC, respectively) aggregates for calvaria bone regeneration. The silane-coated HAP-GEL with and without TiO 2 additives were polymerized and molded to produce macroporous scaffolds. Aggregates of the rat MAPC were precultured, loaded into each scaffold, and implanted to rat calvaria criticalsize defects to study bone regeneration. Bone autografts were used as positive controls and a poly(lacticco-glycolic acid) (PLGA) scaffold for comparison purposes. Preimplanted scaffolds and calvaria bone from pig were tested for ultimate compressive strength with an Instron 4411 Ò and for porosity with microcomputerized tomography (mCT). Osteointegration and newly formed bone (NFB) were assessed by mCT and nondecalcified histology, and quantified by calcium fluorescence labeling. Results showed that the macroporous TiO 2 -HAP-GEL scaffold had a comparable strength relative to the natural calvaria bone (13.8 -4.5 MPa and 24.5 -8.3 MPa, respectively). Porosity was 1.52 -0.8 mm and 0.64 -0.4 mm for TiO 2 -HAP-GEL and calvaria bone, respectively. At 8 and 12 weeks postimplantation into rat calvaria defects, greater osteointegration and NFB were significantly present in the TiO 2 -enriched HAP-GEL constructs with OD-MAPCs, compared to the undifferentiated MAPCloaded constructs, cell-free HAP-GEL with and without titanium, and PLGA scaffolds. The tissue-engineered TiO 2 -enriched HAP-GEL constructs with OD-MAPC aggregates present a potential useful therapeutic approach for calvaria bone regeneration.

Biomaterials for Craniofacial Bone Engineering

“…However, recent advances in 3-dimensional printing techniques, such as robocasting, have enabled scaffold manufacture with highly controlled pore architecture and morphology (Ricci et al, 2012). A study from the National Institute of Dental and Craniofacial Research demonstrated that the combination of titanium dioxide with a hydroxyapatite-gelatin macroporous scaffold had comparable strength relative to natural calvarial bone in a study of rat critical-sized calvarial defects (Ferreira et al, 2013).…”

In-situ hybridization of calcium silicate and hydroxyapatite-gelatin nanocomposites enhances physical property and in vitro osteogenesis

“…All animal care and experimental procedures were approved by the University of North Carolina at Chapel Hill Institutional Animal Care and Use Committee (IACUC09-270.0) in compliance with the NIH Guide for Care and Use of Laboratory Animals. All surgical procedures were followed the same protocol as previously described [23]. Briefly, an 8 mm critical-sized defect was created on the calvarium.…”

“…After 12 weeks postoperatively, each calvarium was harvested, sectioned (nondecalcified), and stained with Steven's Blue and counterstained with Van Gieson. The process of the non-decalcified section was well described in previous study [23]. The medial sagittal sections were chosen and acquired color images using a light microscope (Nikon Eclipse Ti-U, Nikon, Japan) mounted with an Olympus DP12 camera.…”

Effects of oestrogen deficiency and 17β-estradiol therapy on bone healing in calvarial critical size defects treated with bovine bone graft

“…1 A variety of bone grafting or substitutes [2][3][4][5] have been placed in these defects in order to facilitate and/or promote bone healing. However, the problems associated with bone healing followed bone reconstruction may be associated more with systemic skeletal disorders.…”