Biocompatibility and osteogenic capacity of additively manufactured biodegradable porous WE43 scaffolds: An in vivo study in a canine model.

Magnesium is the most promising absorbable metallic implant material for bone regeneration and alloy WE43 is already FDA approved for cardiovascular applications. This study investigates the cyto- and biocompatibility of novel additively manufactured (AM) porous WE43 scaffolds as well as their osteogenic potential and degradation characteristics in an orthotopic canine bone defect model. The cytocompatibility was demonstrated using modified ISO 10993-conform extract-based indirect and direct assays, respectively. Additionally, degradation rates of WE43 scaffolds were quantified in vitro prior to absorption tests in vivo. Complete blood cell counts, blood biomarker analyses, blood trace element analyses as well as multi-organ histopathology demonstrated excellent biocompatibility of porous y WE43 scaffolds for bone defect repair. Micro-CT analyses further showed a relatively higher absorption rate during the initial four weeks upon implantation (i.e., 36 % ± 19 %) than between four and 12 weeks (41 % ± 14 %), respectively. Of note, the porous WE43 implants were surrounded by newly formed bony tissue as early as four weeks after implantation when unmineralized trabecular ingrowth was detected. After 12 weeks, a substantial amount of mineralized bone was detected inside and around the gradually disappearing implants. This first study on AM porous WE43 implants in canine bone defects demonstrates the potential of this alloy for in vivo applications in humans. Our data further underscore the need to control initial bulk absorption kinetics through surface modifications.

Physiological Mineralization during In Vitro Osteogenesis in a Biomimetic Spheroid Culture Model.

Bone health-targeting drug development strategies still largely rely on inferior 2D in vitro screenings. We aimed at developing a scaffold-free progenitor cell-based 3D biomineralization model for more physiological high-throughput screenings. MC3T3-E1 pre-osteoblasts were cultured in α-MEM with 10% FCS, at 37 °C and 5% CO2 for up to 28 days, in non-adherent V-shaped plates to form uniformly sized 3D spheroids. Osteogenic differentiation was induced by 10 mM ß-glycerophosphate and 50 µg/mL ascorbic acid. Mineralization stages were assessed through studying expression of marker genes, alkaline phosphatase activity, and calcium deposition by histochemistry. Mineralization quality was evaluated by Fourier transformed infrared (FTIR) and scanning electron microscopic (SEM) analyses and quantified by micro-CT analyses. Expression profiles of selected early- and late-stage osteoblast differentiation markers indicated a well-developed 3D biomineralization process with strongly upregulated Col1a1, Bglap and Alpl mRNA levels and type I collagen- and osteocalcin-positive immunohistochemistry (IHC). A dynamic biomineralization process with increasing mineral densities was observed during the second half of the culture period. SEM-Energy-Dispersive X-ray analyses (EDX) and FTIR ultimately confirmed a native bone-like hydroxyapatite mineral deposition ex vivo. We thus established a robust and versatile biomimetic, and high-throughput compatible, cost-efficient spheroid culture model with a native bone-like mineralization for improved pharmacological ex vivo screenings.