A novel porous granular scaffold for the promotion of trabecular bone repair by time-dependent alteration of morphology.

Granular scaffolds have been extensively used in the clinic to repair irregular maxillofacial defects. There remain some challenges for the repair of trabecular structures in cancellous bone due to the reticular lamella-like morphology. In this study, we fabricated a novel granular scaffold by rational design of components with different degradation rates so that the morphology of the novel scaffold can evolve to match the growth period of bone cells. Here, polycaprolactone (PCL) was used to fabricate porous microspheres as a skeleton with slow degradation. The macropores were filled with quick degraded gelatin to form complete microspheres. Asynchronous degradation of the two components altered the morphology of the evolutive scaffold from compact to porous, gradually exposing the ridge-like skeletons. This scaffold reversed the decline of cellular adhesion to simple porous skeletons during the initial adhesion. Furthermore, the cells were able to grow into the pores and adhere onto the skeletons with an elongated cellular morphology, facilitating osteogenic differentiation. This novel scaffold was experimentally proven to promote the regeneration of alveolar bone along with a good percentage of bone volume and the formation of trabecular structures. We believe this morphology-evolved scaffold is highly promising for regenerative applications in the clinic.

Superparamagnetic core-shell electrospun scaffolds with sustained release of IONPs facilitating in vitro and in vivo bone regeneration.

Bone tissue engineering (BTE) is a promising approach to recover insufficient bone in dental implantations. However, the clinical application of BTE scaffolds is limited by their low mechanical strength and lack of osteoinduction. In an attempt to circumvent these limitations and improve osteogenesis, we introduced magnetic iron oxide nanoparticles (IONPs) into a core-shell porous electrospun scaffold and evaluated their impact on the physical, mechanical, and biological properties of the scaffold. We used poly(lactic-co-glycolic acid)/polycaprolactone/beta-tricalcium phosphate (PPT) scaffolds with and without γ-Fe2O3 encapsulation, namely PPT-Fe scaffolds and PPT scaffolds, respectively. The γ-Fe2O3 used in the PPT-Fe scaffolds was coated with polyglucose sorbitol carboxymethylether and was biocompatible. Structurally, PPT-Fe scaffolds showed uniform iron distribution encapsulated within the resorbable PPT scaffolds, and these scaffolds supported sustainable iron release. Furthermore, compared with PPT scaffolds, PPT-Fe scaffolds showed significantly better physical and mechanical properties, including wettability, superparamagnetism, hardness, tensile strength, and elasticity modulus. In vitro tests of rat adipose-derived mesenchymal stem cells (rADSCs) seeded onto the scaffolds showed increased expression of integrin ß1, alkaline phosphatase, and osteogenesis-related genes. In addition, enhanced in vivo bone regeneration was observed after implanting PPT-Fe scaffolds in rat calvarial bone defects. Thus, we can conclude that the incorporation of IONPs into porous scaffolds for long-term release can provide a new strategy for BTE scaffold optimization and is a promising approach that can offer enhanced osteogenic capacity in clinical applications.

Thermally induced self-agglomeration 3D scaffolds with BMP-2-loaded core-shell fibers for enhanced osteogenic differentiation of rat adipose-derived stem cells.

INTRODUCTION: Scaffold structure plays a vital role in cell behaviors. Compared with two-dimensional structure, 3D scaffolds can mimic natural extracellular matrix (ECM) and promote cell-cell and cell-matrix interactions. The combination of osteoconductive scaffolds and osteoinductive growth factors is considered to have synergistic effects on bone regeneration. MATERIALS AND METHODS: In this study, core-shell poly(lactide-co-glycolide) (PLGA)/polycaprolactone (PCL)-BMP-2 (PP-B) fibrous scaffolds were prepared through coaxial electrospinning. Next, we fabricated 3D scaffolds based on PP-B fibers with thermally induced self-agglomeration (TISA) method and compared with conventional PLGA/PCL scaffolds in terms of scaffold morphology and BMP-2 release behaviors. Then, rat adipose-derived stem cells (rADSCs) were seeded on the scaffolds, and the effects on cell proliferation, cell morphology, and osteogenic differentiation of rADSCs were detected. RESULTS: The results demonstrated that 3D scaffold incorporated with BMP-2 significantly increased proliferation and osteogenic differentiation of rADSCs, followed by PP-B group. CONCLUSION: Our findings indicate that scaffolds with 3D structure and osteoinductive growth factors have great potential in bone tissue engineering.

Enhanced Osteogenesis of ADSCs by the Synergistic Effect of Aligned Fibers Containing Collagen I.

The topographical features and material composition of scaffolds have a powerful influence on cell behaviors such as proliferation and differentiation. Here, scaffolds consisting of aligned fibers with incorporated bioactive collagen I were tested for their ability to enhance osteogenesis in vitro. Rat adipose-derived mesenchymal stem cells (ADSCs) were seeded on the scaffolds and their morphology, proliferation, and osteogenic differentiation were examined. Aligned scaffolds with collagen I showed the best osteogenic properties. Also, adhesion-related genes showed the higher expression on aligned scaffolds with collagen I. Our findings indicate that fiber alignment combined with incorporation of collagen I increases the capacity of electrospun scaffolds to induce enhanced and directed osteogenesis. Such scaffolds may, therefore, have potential for improving guided oral bone regeneration.

The preosteoblast response of electrospinning PLGA/PCL nanofibers: effects of biomimetic architecture and collagen I.

Constructing biomimetic structure and incorporating bioactive molecules is an effective strategy to achieve a more favorable cell response. To explore the effect of electrospinning (ES) nanofibrous architecture and collagen I (COL I)-incorporated modification on tuning osteoblast response, a resorbable membrane composed of poly(lactic-co-glycolic acid)/poly(caprolactone) (PLGA/PCL; 7:3 w/w) was developed via ES. COL I was blended into PLGA/PCL solution to prepare composite ES membrane. Notably, relatively better cell response was delivered by the bioactive ES-based membrane which was fabricated by modification of 3,4-dihydroxyphenylalanine and COL I. After investigation by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, contact angle measurement, and mechanical test, polyporous three-dimensional nanofibrous structure with low tensile force and the successful integration of COL I was obtained by the ES method. Compared with traditional PLGA/PCL membrane, the surface hydrophilicity of collagen-incorporated membranes was largely enhanced. The behavior of mouse preosteoblast MC3T3-E1 cell infiltration and proliferation on membranes was studied at 24 and 48 hours. The negative control was fabricated by solvent casting. Evaluation of cell adhesion and morphology demonstrated that all the ES membranes were more favorable for promoting the cell adhesion and spreading than the casting membrane. Cell Counting Kit-8 assays revealed that biomimetic architecture, surface topography, and bioactive properties of membranes were favorable for cell growth. Analysis of ß1 integrin expression level by immunofluorescence indicated that such biomimetic architecture, especially COL I-grafted surface, plays a key role in cell adhesion and proliferation. The real-time polymerase chain reaction suggested that both surface topography and bioactive properties could facilitate the cell adhesion. The combined effect of biomimetic architecture with enhanced surface activity by 3,4-dihydroxyphenylalanine-assisted modification and COL I incorporation of PLGA/PCL electrospun membranes could successfully fill osteogenic defects and allow for better cell proliferation and differentiation.

Effect of surface topography and bioactive properties on early adhesion and growth behavior of mouse preosteoblast MC3T3-E1 cells.

The effects of bioactive properties and surface topography of biomaterials on the adhesion and spreading properties of mouse preosteoblast MC3T3-E1 cells was investigated by preparation of different surfaces. Poly lactic-co-glycolic acid (PLGA) electrospun fibers (ES) were produced as a porous rough surface. In our study, coverslips were used as a substrate for the immobilization of 3,4-dihydroxyphenylalanine (DOPA) and collagen type I (COL I) in the preparation of bioactive surfaces. In addition, COL I was immobilized onto porous electrospun fibers surfaces (E-COL) to investigate the combined effects of bioactive molecules and topography. Untreated coverslips were used as controls. Early adhesion and growth behavior of MC3T3-E1 cells cultured on the different surfaces were studied at 6, 12, and 24 h. Evaluation of cell adhesion and morphological changes showed that the all the surfaces were favorable for promoting the adhesion and spreading of cells. CCK-8 assays and flow cytometry revealed that both topography and bioactive properties were favorable for cell growth. Analysis of ß1, α1, α2, α5, α10 and α11 integrin expression levels by immunofluorescence, real-time RT-PCR, and Western blot and indicated that surface topography plays an important role in the early stage of cell adhesion. However, the influence of topography and bioactive properties of surfaces on integrins is variable. Compared with any of the topographic or bioactive properties in isolation, the combined effect of both types of properties provided an advantage for the growth and spreading of MC3T3-E1 cells. This study provides a new insight into the functions and effects of topographic and bioactive modifications of surfaces at the interface between cells and biomaterials for tissue engineering.