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Objective: The pore size of the scaffold is a critical factor in repairing large bone defect. Here, we investigated the potential of bone regeneration using novel nanocomposite polydopamine-laced hydroxyapatite collagen calcium silicate (HCCS-PDA) scaffolds with two different pore sizes, 250 and 500 μm.Samples/setting: A total of 12 male Sprague-Dawley rats were implanted with HCCS-PDA scaffold with pore size of either 250 or 500 μm into surgically created critical-sized defect (CSD).Methods: HCCS-PDA scaffolds were fabricated using mould printing technique. The effect of pore size on mechanical strength of the scaffolds was assessed by compression testing. After seeding with rat mesenchymal stem cells (rMSCs), the scaffolds were implanted, and new bone formation was evaluated using microCT and histomorphometric analysis after 8 weeks.Results: MicroCT and histology analysis demonstrated restricted peripheral new bone formation in either dural or periosteal side and limited new bone formation in the 250 μm pore scaffold. Conversely, the 500-μm pore scaffold showed more penetration of new bone into the scaffold and greater bone regeneration in the rat CSD.Conclusion: Based on our results, which demonstrated improved new bone formation in 500 μm pores scaffold, we can conclude that effective scaffold pore size that induces osteointegration and bone regeneration is around 500 μm for HCCS-PDA nanocomposite scaffold. [ABSTRACT FROM AUTHOR]

Bioluminescent imaging (BLI) has emerged as a popular in vivo tracking modality in bone regeneration studies stemming from its clear advantages: non-invasive, real-time, and inexpensive. We recently adopted bioluminescence resonance energy transfer (BRET) principle to improve BLI cell tracking and generated the brightest bioluminescent signal known to date, which thus enables more sensitive real-time cell tracking at deep tissue level. In the present study, we brought BRET-based cell tracking strategy into the field of bone tissue engineering for the first time. We labeled rat mesenchymal stem cells (rMSCs) with our in-house BRET-based GpNLuc reporter and evaluated the cell tracking efficacy both in vitro and in vivo. In scaffold-free spheroid 3D culture system, using BRET-based GpNLuc labeling resulted in significantly better correlation to cell numbers than a fluorescence based approach. In scaffold-based 3D culture system, GpNLuc-rMSCs displayed robust bioluminescence signals with minimal background noise. Furthermore, a tight correlation between BLI signal and cell number highlighted the robust reliability of using BRET-based BLI. In calvarial critical sized defect model, robust signal and the consistency in cell survival evaluation collectively supported BRET-based GpNLuc labeling as a reliable approach for non-invasively tracking MSC. In summary, BRET-based GpNLuc labeling is a robust, reliable, and inexpensive real-time cell tracking method, which offers a promising direction for the technological innovation of BLI and even non-invasive tracking systems, in the field of bone tissue engineering. [ABSTRACT FROM AUTHOR]

Scaffolds that are used for bone repair should provide an adequate environment for biomineralization by mesenchymal stem cells (MSCs). Recently, decellularized pulp matrices (DPM) have been utilized in endodontics for their high regenerative potential. Inspired by the dystrophic calcification on the pulp matrix known as pulp stone, we developed acellular pulp bioscaffolds and examined their potential in facilitating MSCs mineralization for bone defect repair. Pulp was decellularized, then retention of its structural integrity was confirmed by histological, mechanical, and biochemical evaluations. MSCs were seeded and proliferation, osteogenic gene expression, and biomineralization were assessed to verify DPM's osteogenic effects in vitro. MicroCT, energy-dispersive X-ray (EDX), and histological analyses were used to confirm that DPM seeded with MSCs result in greater mineralization on rat critical-sized defects than that without MSCs. Overall, our study proves DPM's potential to serve as a scaffolding material for MSC-mediated bone regeneration for future craniofacial bone tissue engineering. [ABSTRACT FROM AUTHOR]

Although bone marrow–derived mesenchymal stem cells (MSCs) have been extensively explored in bone tissue engineering, only few studies using mesenchymal stem cells from mandible (M-MSCs) have been reported. However, mesenchymal stem cells from mandible have the potential to be as effective as femur-derived mesenchymal stem cells (F-MSCs) in regenerating bone, especially in the orofacial regions, which share embryonic origin, proximity, and accessibility. M-MSCs were isolated and characterized using mesenchymal stem cell–specific markers, colony forming assay, and multi-potential differentiation. In vitro osteogenic potential, including proliferation, osteogenic gene expression, alkaline phosphatase activity, and mineralization, was examined and compared. Furthermore, in vivo bone formations of F-MSCs and M-MSCs in rat critical sized defect were evaluated using microCT and histology. M-MSCs from rat could be successfully isolated and expanded while preserving their MSC's characteristics. M-MSCs demonstrated a comparable proliferation and mineralization potentials and in vivo bone formation as F-MSCs. M-MSCs is a promising cell source candidate for craniofacial bone tissue engineering. [ABSTRACT FROM AUTHOR]