In vitro osteogenesis of synovium mesenchymal cells induced by controlled release of alendronate and dexamethasone from a sintered microspherical scaffold

Computer-aided patterning of PCL microspheres to build modular scaffolds featuring improved strength and neovascularized tissue integration

In the past decade, modular scaffolds prepared by assembling biocompatible and biodegradable building blocks (e.g. microspheres) have found promising applications in tissue engineering (TE) towards the repair/regeneration of damaged and impaired tissues. Nevertheless, to date this approach has failed to be transferred to the clinic due to technological limitations regarding microspheres patterning, a crucial issue for the control of scaffold strength, vascularization and integration in vivo. In this work, we propose a robust and reliable approach to address this issue through the fabrication of polycaprolactone (PCL) microsphere-based scaffolds with in-silico designed microarchitectures and high compression moduli. The scaffold fabrication technique consists of four main steps, starting with the manufacture of uniform PCL microspheres by fluidic emulsion technique. In the second step, patterned polydimethylsiloxane (PDMS) moulds were prepared by soft lithography. Then, layers of 500 µm PCL microspheres with geometrically inspired patterns were obtained by casting the microspheres onto PDMS moulds followed by their thermal sintering. Finally, three-dimensional porous scaffolds were built by the alignment, stacking and sintering of multiple (up to six) layers. The so prepared scaffolds showed excellent morphological and microstructural fidelity with respect to the in-silico models, and mechanical compression properties suitable for load bearing TE applications. Designed porosity and pore size features enabled in vitro human endothelial cells adhesion and growth as well as tissue integration and blood vessels invasion in vivo. Our results highlighted the strong impact of spatial patterning of microspheres on modular scaffolds response, and pay the way about the possibility to fabricate in silico-designed structures featuring biomimetic composition and architectures for specific TE purposes.

Toward zonally tailored scaffolds for osteochondral differentiation of synovial mesenchymal stem cells

Synovium-derived mesenchymal stem cells (SMSCs) are an emerging cell source for regenerative medicine applications, including osteochondral defect (OCD) repair. However, in contrast to bone marrow MSCs, scaffold compositions which promote SMSC chondrogenesis/osteogenesis are still being identified. In the present manuscript, we examine poly(ethylene) glycol (PEG)-based scaffolds containing zonally-specific biochemical cues to guide SMSC osteochondral differentiation. Specifically, SMSCs were encapsulated in PEG-based scaffolds incorporating glycosaminoglycans (hyaluronan or chondroitin-6-sulfate [CSC]), low-dose of chondrogenic and osteogenic growth factors (TGFβ1 and BMP2, respectively), or osteoinductive poly(dimethylsiloxane) (PDMS). Initial studies suggested that PEG-CSC-TGFβ1 scaffolds promoted enhanced SMSC chondrogenic differentiation, as assessed by significant increases in Sox9 and aggrecan. Conversely, PEG-PDMS-BMP2 scaffolds stimulated increased levels of osteoblastic markers with significant mineral deposition. A "Transition" zone formulation was then developed containing a graded mixture of the chondrogenic and osteogenic signals present in the PEG-CSC-TGFβ1 and PEG-PDMS-BMP2 constructs. SMSCs within the "Transition" formulation displayed a phenotypic profile similar to hypertrophic chondrocytes, with the highest expression of collagen X, intermediate levels of osteopontin, and mineralization levels equivalent to "bone" formulations. Overall, these results suggest that a graded transition from PEG-CSC-TGFβ1 to PEG-PDMS-BMP2 scaffolds elicits a gradual SMSC phenotypic shift from chondrocyte to hypertrophic chondrocyte to osteoblast-like. As such, further development of these scaffold formulations for use in SMSC-based OCD repair is warranted. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2019-2029, 2019.

Polymer coated mesoporous ceramic for drug delivery in bone tissue engineering

Treatment strategy for various bone fracture and defects the researchers are focusing to develop a new carrier for delivering the drug into injured area with controlled and sustained manner using biomaterials with dynamic architecture orientation. Ceramic materials are resembled with bone compositional architecture and better bioactivity, degradability as well as antimicrobial activity made its enormous application in bone tissue engineering (BTE). Current focus in regenerative medicine were orchestration of biomaterials with the capacity of loading the drugs, growth factors, ionic components to promote better healing of bone tissue. Mesoporous type materials owed a great look towards the delivery of drugs, growth factors, etc in BTE because of its unique geometry. So the guest molecules loaded with geometrically organized ceramics would deliver onto the site of injury in controlled manner also the guiding and regulation of delivery of molecules have been controlled with the polymers response to different stimulation or biochemical factors as either scaffold or encapsulated particles for bone regeneration. Hence the review aims to describing the recent progress in bone tissue engineering using the ceramic based mesoporous materials encapsulated with polymers respond to different physiochemical stimulation for the efficient and controlled delivery of drug/growth factors for better bone healing.

Reconstruction of Large-scale Defects with a Novel Hybrid Scaffold Made from Poly(L-lactic acid)/Nanohydroxyapatite/Alendronate-loaded Chitosan Microsphere: in vitro and in vivo Studies

A chitosan-based microsphere delivery system has been fabricated for controlled release of alendronate (AL). The present study aimed to incorporate the chitosan/hydroxyapatite microspheres-loaded with AL (CH/nHA-AL) into poly(L-lactic acid)/nanohydroxyapatite (PLLA/nHA) matrix to prepare a novel microspheres-scaffold hybrid system (CM-ALs) for drug delivery and bone tissue engineering application. The characteristics of CM-ALs scaffolds containing 10% and 20% CH/nHA-AL were evaluated in vitro, including surface morphology and porosity, mechanical properties, drug release, degradation, and osteogenic differentiation. The in vivo bone repair for large segmental radius defects (1.5 cm) in a rabbit model was evaluated by radiography and histology. In vitro study showed more sustained drug release of CM-AL-containing scaffolds than these of CM/nHA-AL and PLLA/nHA/AL scaffolds, and the mechanical and degradation properties of CM-ALs (10%) scaffolds were comparable to that of PLLA/nHA control. The osteogenic differentiation of adipose-derived stem cells (ASCs) was significantly enhanced as indicated by increased alkaline phosphates (ALP) activity and calcium deposition. In vivo study further showed better performance of CM-ALs (10%) scaffolds with complete repair of large-sized bone defects within 8 weeks. A microspheres-scaffold-based release system containing AL-encapsulated chitosan microspheres was successfully fabricated in this study. Our results suggested the promising application of CM-ALs (10%) scaffolds for drug delivery and bone tissue engineering.

The Effect of Alendronate Loaded Biphasic Calcium Phosphate Scaffolds on Bone Regeneration in a Rat Tibial Defect Model

This study investigated the effect of alendronate (Aln) released from biphasic calcium phosphate (BCP) scaffolds. We evaluated the in vitro osteogenic differentiation of Aln/BCP scaffolds using MG-63 cells and the in vivo bone regenerative capability of Aln/BCP scaffolds using a rat tibial defect model with radiography, micro-computed tomography (CT), and histological examination. In vitro studies included the surface morphology of BCP and Aln-loaded BCP scaffolds visualized using field-emission scanning electron microscope, release kinetics of Aln from BCP scaffolds, alkaline phosphatase (ALP) activity, calcium deposition, and gene expression. The in vitro studies showed that sustained release of Aln from the BCP scaffolds consisted of porous microstructures, and revealed that MG-63 cells cultured on Aln-loaded BCP scaffolds showed significantly increased ALP activity, calcium deposition, and gene expression compared to cells cultured on BCP scaffolds. The in vivo studies using radiograph and histology examination revealed abundant callus formation and bone maturation at the site in the Aln/BCP groups compared to the control group. However, solid bony bridge formation was not observed at plain radiographs until 8 weeks. Micro-CT analysis revealed that bone mineral density and bone formation volume were increased over time in an Aln concentration-dependent manner. These results suggested that Aln/BCP scaffolds have the potential for controlling the release of Aln and enhance bone formation and mineralization.

Small molecules and their controlled release that induce the osteogenic/chondrogenic commitment of stem cells

Stem cell-based tissue engineering plays a significant role in skeletal system repair and regenerative therapies. However, stem cells must be differentiated into specific mature cells prior to implantation (direct implantation may lead to tumour formation). Natural or chemically synthesised small molecules provide an efficient, accurate, reversible, and cost-effective way to differentiate stem cells compared with bioactive growth factors and gene-related methods. Thus, investigating the influences of small molecules on the differentiation of stem cells is of great significance. Here, we review a series of small molecules that can induce or/and promote the osteogenic/chondrogenic commitment of stem cells. The controlled release of these small molecules from various vehicles for stem cell-based therapies and tissue engineering applications is also discussed. The extensive studies in this field represent significant contributions to stem cell-based tissue engineering research and regenerative medicine.

Stretchable and micropatterned membrane for osteogenic differentation of stem cells

Stem cells have emerged as potentially useful cells for regenerative medicine applications. To fully harness this potential, it is important to develop in vitro cell culture platforms with spatially regulated mechanical, chemical, and biological cues to induce the differentiation of stem cells. In this study, a cell culture platform was constructed that used polydopamine (PDA)-coated parafilm. The modified parafilm supports cell attachment and proliferation. In addition, because of the superb plasticity and ductility of the parafilm, it can be easily micropatterned to regulate the spatial arrangements of cells, and can exert different mechanical tensions. Specifically, we constructed a PDA-coated parafilm with grooved micropatterns to induce the osteogenic differentiation of stem cells. Adipose-derived mesenchymal stem cells that were cultured on the PDA-coated parafilm exhibited significantly higher osteogenic commitment in response to mechanical and spatial cues compared to the ones without stretch. Our findings may open new opportunities for inducing osteogenesis of stem cells in vitro using the platform that combines mechanical and spatial cues.

Effects of various extracellular matrix proteins on the growth of HL-1 cardiomyocytes

We present the physical and biochemical effects of extracellular matrixes (ECMs) on HL-1 cardiomyocytes. ECMs play major roles in cell growth, adhesion and the maintenance of native cell functions. We investigated the effects of 6 different cell culture systems: 5 different ECM-treated surfaces (fibronectin, laminin, collagen I, gelatin and a gelatin/fibronectin mixture) and 1 nontreated surface. Surface morphology was scanned and analyzed using atomic force microscopy in order to investigate the physical effects of ECMs. The attachment, growth, viability, proliferation and phenotype of the cells were analyzed using phase-contrast microscopy and immunocytochemistry to elucidate the biochemical effects of ECMs. Our study provides basic information for understanding cell-ECM interactions and should be utilized in future cardiac cell research and tissue engineering.

Delivery of dimethyloxallyl glycine in mesoporous bioactive glass scaffolds to improve angiogenesis and osteogenesis of human bone marrow stromal cells

Development of hypoxia-mimicking bone tissue engineering scaffolds is of great importance in stimulating angiogenesis for bone regeneration. Dimethyloxallyl glycine (DMOG) is a cell-permeable, competitive inhibitor of hypoxia-inducible factor prolyl hydroxylase (HIF-PH), which can stabilize hypoxia-inducible factor 1α (HIF-1α) expression. The aim of this study was to develop hypoxia-mimicking scaffolds by delivering DMOG in mesoporous bioactive glass (MBG) scaffolds and to investigate whether the delivery of DMOG could induce a hypoxic microenvironment for human bone marrow stromal cells (hBMSC). MBG scaffolds with varied mesoporous structures (e.g. surface area and mesopore volume) were prepared by controlling the contents of mesopore-template agent. The composition, large-pore microstructure and mesoporous properties of MBG scaffolds were characterized. The effect of mesoporous properties on the loading and release of DMOG in MBG scaffolds was investigated. The effects of DMOG delivery on the cell morphology, cell viability, HIF-1α stabilization, vascular endothelial growth factor (VEGF) secretion and bone-related gene expression (alkaline phosphatase, ALP; osteocalcin, OCN; and osteopontin, OPN) of hBMSC in MBG scaffolds were systematically investigated. The results showed that the loading and release of DMOG in MBG scaffolds can be efficiently controlled by regulating their mesoporous properties via the addition of different contents of mesopore-template agent. DMOG delivery in MBG scaffolds had no cytotoxic effect on the viability of hBMSC. DMOG delivery significantly induced HIF-1α stabilization, VEGF secretion and bone-related gene expression of hBMSC in MBG scaffolds in which DMOG counteracted the effect of HIF-PH and stabilized HIF-1α expression under normoxic condition. Furthermore, it was found that MBG scaffolds with slow DMOG release significantly enhanced the expression of bone-related genes more than those with instant DMOG release. The results suggest that the controllable delivery of DMOG in MBG scaffolds can mimic a hypoxic microenvironment, which not only improves the angiogenic capacity of hBMSC, but also enhances their osteogenic differentiation.

Composite polymer-bioceramic scaffolds with drug delivery capability for bone tissue engineering

INTRODUCTION

Next-generation scaffolds for bone tissue engineering (BTE) should exhibit the appropriate combination of mechanical support and morphological guidance for cell proliferation and attachment while at the same time serving as matrices for sustained delivery of therapeutic drugs and/or biomolecular signals, such as growth factors. Drug delivery from BTE scaffolds to induce the formation of functional tissues, which may need to vary temporally and spatially, represents a versatile approach to manipulating the local environment for directing cell function and/or to treat common bone diseases or local infection. In addition, drug delivery from BTE is proposed to either increase the expression of tissue inductive factors or to block the expression of others factors that could inhibit bone tissue formation. Composite scaffolds which combine biopolymers and bioactive ceramics in mechanically competent 3D structures, including also organic-inorganic hybrids, are being widely developed for BTE, where the affinity and interaction between biomaterials and therapeutic drugs or biomolecular signals play a decisive role in controlling the release rate.

AREAS COVERED

This review covers current developments and applications of 3D composite scaffolds for BTE which exhibit the added capability of controlled delivery of therapeutic drugs or growth factors. A summary of drugs and biomolecules incorporated in composite scaffolds and approaches developed to combine biopolymers and bioceramics in composites for drug delivery systems for BTE is presented. Special attention is given to identify the main challenges and unmet needs of current designs and technologies for developing such multifunctional 3D composite scaffolds for BTE.

EXPERT OPINION

One of the major challenges for developing composite scaffolds for BTE is the incorporation of a drug delivery function of sufficient complexity to be able to induce the release patterns that may be necessary for effective osseointegration, vascularization and bone regeneration. Loading 3D scaffolds with different biomolecular agents should produce a codelivery system with different, predetermined release profiles. It is also envisaged that the number of relevant bioactive agents that can be loaded onto scaffolds will be increased, whilst the composite scaffold design should exploit synergistically the different degradation profiles of the organic and inorganic components.

Local delivery of alendronate eluting chitosan scaffold can effectively increase osteoblast functions and inhibit osteoclast differentiation

The aim of this study was to investigate the effect of alendronate released from chitosan scaffolds on enhancement of osteoblast functions and inhibition of osteoclast differentiation in vitro. The surface and cell morphologies of chitosan scaffolds and alendronate-loaded chitosan scaffolds were characterized by variable pressure field emission scanning electron microscope (VP-FE-SEM). Alendronate was released in a sustained manner. For evaluating osteoblast functions in MG-63 cells, we investigated cell proliferation, alkaline phosphatase (ALP) activity, and calcium deposition. Furthermore, for evaluating inhibition of osteoclast differentiation in RAW 264.7 cells, we investigated tartrate-resistant acid phosphatase (TRAP) activity, TRAP staining, and gene expressions. The in vitro studies revealed that osteoblasts grown on alendronate-loaded chitosan scaffold showed a significant increment in cell proliferation, ALP activity, and calcium deposition as compared to those grown on chitosan scaffolds. In addition, the in vitro study showed that osteoclast differentiation in RAW 264.7 cells cultured on alendronate-loaded chitosan scaffolds was greatly inhibited as compared to those cultured on chitosan scaffolds by the results of TRAP activity, TRAP staining, and gene expressions. Taken together, alendronate-loaded chitosan scaffolds could achieve the dual functions of improvement in osteoblast functions and inhibition of osteoclast differentiation. Thus, alendronate-eluting chitosan substrates are promising materials for enhancing osteoblast functions and inhibiting osteoclast differentiation in orthopedic and dental fields.

Peculiarities of using stem cells for regeneration of the bone and cartilage tissue

Scientific literature about the use of MSC contains clinical and experimental data on the efficiency of cell technologies for restoration of the osteoarticular apparatus. The use of MSC immobilized in the appropriate carriers and differentiation of these cells towards the bone cells and chondrocytes are of crucial importance. However, the use of MSC, both individual and in combination with other preparations and substances has a number of drawbacks and advantages. The absence of published reports on contraindications and complications of cell therapy is worthy of note, because the analysis of unsuccessful application of MSC will help to determine the indication for this treatment, and hence, to improve the efficiency of cell technologies in the future. Wider use of MSC in clinical practice and experimental studies for acceleration of reparative processes in the bone and cartilage tissue seems to be promising.

Fabrication of a Layered Microstructured Polymeric Microspheres as a Cell Carrier for Nucleus Pulposus Regeneration

This study aimed to investigate the feasibility of nanostructured 3D poly(lactide-co-glycolide) (PLGA) constructs, which are loaded with dexamethasone (DEX) and growth factor embedded hepaiin/poly(L-lysine) nanoparticles by a layer-by-layer system, to serve as an effective scaffold for nucleus pulposus (NP) tissue engineering. Our results demonstrated that the microsphere constructs were capable of simultaneously releasing basic fibroblast growth factor and DEX with approximately zero-order kinetics. The dual bead microspheres showed no cytotoxicity, and promoted the proliferation of the rat mesenchymal stem cells (rMSCs) by lactate dehydrogenase assay and CCK-8 assay. After 4 weeks of culture in vitro, the rMSCs- scaffold hybrids contained significantly higher levels of sulfated GAG/DNA and type-II collagen than the control samples. Moreover, quantity real-time PCR analysis revealed that the expression of disc-matrix proteins, including type-II collagen, aggrecan and versican, in the rMSCs-scaffold hybrids was significantly higher than the control group, whereas the expression of osteogenic differentiation marker type-I collagen was decreased. Taken together, these data indicate that the heparin bound bFGF-coated and DEX-loaded PLGA microsphere constructs is an effective bioactive scaffold for the regeneration of NP tissue.

Proliferation, differentiation and gene expression of osteoblasts in boron-containing associated with dexamethasone deliver from mesoporous bioactive glass scaffolds

Boron is one of the trace elements in the human body which plays an important role in bone growth. Porous mesopore bioactive glass (MBG) scaffolds are proposed as potential bone regeneration materials due to their excellent bioactivity and drug-delivery ability. The aims of the present study were to develop boron-containing MBG (B-MBG) scaffolds by sol-gel method and to evaluate the effect of boron on the physiochemistry of B-MBG scaffolds and the response of osteoblasts to these scaffolds. Furthermore, the effect of dexamethasone (DEX) delivery in B-MBG scaffold system was investigated on the proliferation, differentiation and bone-related gene expression of osteoblasts. The composition, microstructure and mesopore properties (specific surface area, nano-pore volume and nano-pore distribution) of B-MBG scaffolds have been characterized. The effect of boron contents and large-pore porosity on the loading and release of DEX in B-MBG scaffolds were also investigated. The results have shown that the incorporation of boron into MBG scaffolds slightly decreases the specific surface area and pore volume, but maintains well-ordered mesopore structure and high surface area and nano-pore volume compared to non-mesopore bioactive glass. Boron contents in MBG scaffolds did not influence the nano-pore size distribution or the loading and release of DEX. B-MBG scaffolds have the ability to maintain a sustained release of DEX in a long-term span. Incorporating boron into MBG glass scaffolds led to a controllable release of boron ions and significantly improved the proliferation and bone-related gene expression (Col I and Runx2) of osteoblasts. Furthermore, the sustained release of DEX from B-MBG scaffolds significantly enhanced alkaline phosphatase (ALP) activity and gene expressions (Col I, Runx2, ALP and BSP) of osteoblasts. These results suggest that boron plays an important role in enhancing osteoblast proliferation in B-MBG scaffold system and DEX-loaded B-MBG scaffolds show great potential as a release system to enhance osteogenic property for bone tissue engineering application.

Controllable dual-release of dexamethasone and bovine serum albumin from PLGA/β-tricalcium phosphate composite scaffolds

Localized dual-drug delivery from biodegradable scaffolds is an important strategy in tissue engineering. In this study, porous poly(L-lactide-co-glycolide) (PLGA)/β-tricalcium phosphate scaffolds containing both dexamethasone (Dex) and bovine serum albumin (BSA) were prepared by incorporating Dex-loaded and BSA-loaded microspheres into the scaffolds. PLGA microspheres containing Dex or BSA were prepared by spray-drying and double emulsion/solvent evaporation, respectively. In vitro release studies indicated that microspheres prepared from PLGA in 3:1 molar ratio of L-lactide/glycolide and 89.5 kDa relative molecular mass showed prolonged release profiles compared with those prepared from PLGA in 1:1 L-lactide/glycolide molar ratio and 30.5 kDa relative molecular mass. Additionally, introduction of poly(ethylene glycol) in the PLGA chain could improve the encapsulation efficiency and reduce the release rate. Based on the above results, controllable dual-release of Dex and BSA with relatively higher or lower release rate was achieved by incorporating Dex-loaded and BSA-loaded microspheres with different release profiles into the PLGA/β-tricalcium phosphate scaffolds.