Tissue Engineering Purposes Research Articles

Fabrication and Plasma Surface Activation of Aligned Electrospun PLGA Fiber Fleeces with Improved Adhesion and Infiltration of Amniotic Epithelial Stem Cells Maintaining their Teno-inductive Potential.

Electrospun PLGA microfibers with adequate intrinsic physical features (fiber alignment and diameter) have been shown to boost teno-differentiation and may represent a promising solution for tendon tissue engineering. However, the hydrophobic properties of PLGA may be adjusted through specific treatments to improve cell biodisponibility. In this study, electrospun PLGA with highly aligned microfibers were cold atmospheric plasma (CAP)-treated by varying the treatment exposure time (30, 60, and 90 s) and the working distance (1.3 and 1.7 cm) and characterized by their physicochemical, mechanical and bioactive properties on ovine amniotic epithelial cells (oAECs). CAP improved the hydrophilic properties of the treated materials due to the incorporation of new oxygen polar functionalities on the microfibers’ surface especially when increasing treatment exposure time and lowering working distance. The mechanical properties, though, were affected by the treatment exposure time where the optimum performance was obtained after 60 s. Furthermore, CAP treatment did not alter oAECs’ biocompatibility and improved cell adhesion and infiltration onto the microfibers especially those treated from a distance of 1.3 cm. Moreover, teno-inductive potential of highly aligned PLGA electrospun microfibers was maintained. Indeed, cells cultured onto the untreated and CAP treated microfibers differentiated towards the tenogenic lineage expressing tenomodulin, a mature tendon marker, in their cytoplasm. In conclusion, CAP treatment on PLGA microfibers conducted at 1.3 cm working distance represent the optimum conditions to activate PLGA surface by improving their hydrophilicity and cell bio-responsiveness. Since for tendon tissue engineering purposes, both high cell adhesion and mechanical parameters are crucial, PLGA treated for 60 s at 1.3 cm was identified as the optimal construct.

Development of hybrid scaffold: Bioactive glass nanoparticles/chitosan for tissue engineering applications.

Bone tissue engineering is gaining popularity as an alternative method for the treatment of osseous defects. A number of biodegradable polymers have been explored for tissue engineering purposes. A new family of biodegradable polymer/bioactive glass composite materials has been designed to be used in bone regeneration approaches. In this work, a hybrid scaffold of chitosan (CH) and bioactive glass nanoparticles (BGN) was prepared by the freeze-gelation method. This method has been studied by adjusting the concentration of acetic acid; this process can influence the structure properties of the scaffold. In this work, several BGN/CH composites have been prepared by varying the proportion of BGN in the hybrid scaffold (20, 40, 60, and 80%). Brunauer-Emmett-Teller results showed the increased surface area and porosity volume of our composite with decreasing BGN proportion. BGN/CH hybrid scaffold was characterized by using physicochemical techniques. Obtained results showed a macroporous morphology of the scaffold with a pore size of about 200 μm, and a homogeneous distribution of the BGN in the CH matrix. X-ray diffraction study confirmed the amorphous state of the BGN/CH hybrid scaffold. Interaction between CH and BGNs in the composite was confirmed. The in vitro assays showed adequate degradation properties, which is essential for the potential replacement by the new tissue. The in vitro bioactivity studies confirmed the formation of an apatite layer on the surface of the hybrid scaffold, which results in a direct bone bonding of the implant. These results indicate that BGN/CH hybrid scaffold developed is a potential candidate for bone tissue engineering.

Non-viral gene delivery of HIF-1α promotes angiogenesis in human adipose-derived stem cells

Stable and mature vascular formation is a current challenge in engineering functional tissues. Transient, non-viral gene delivery presents a unique platform for delivering genetic information to cells for tissue engineering purposes and to restore blood flow to ischemic tissue. The formation of new blood vessels can be induced by upregulation of hypoxia-inducible factor-1α (HIF-1), among other factors. We hypothesized that biodegradable polymers could be used to efficiently deliver the HIF-1α gene to human adipose-derived stromal/stem cells (hASCs) and that this treatment could recruit an existing endogenous endothelial cell population to induce angiogenesis in a 3D cell construct in vitro. In this study, end-modified poly(β-amino ester) (PBAE) nanocomplexes were first optimized for transfection of hASCs and a new biodegradable polymer with increased hydrophobicity and secondary amine structures, N'-(3-aminopropyl)-N,N-dimethylpropane-1,3-diamine end-modified poly(1,4-butanediol diacrylate-co-4-amino-1-butanol), was found to be most effective. Optimal PBAE nanocomplexes had a hydrodynamic diameter of approximately 140 nm and had a zeta potential of 30 mV. The PBAE polymer self-assembled with HIF-1α plasmid DNA and treatment of hASCs with these nanocomplexes induced 3D vascularization. Cells transfected with this polymer-DNA complex were found to have 106-fold upregulation HIF-1α expression, an approximately 2-fold increase in secreted VEGF, and caused the formation of vessel tubules compared to an untransfected control. These gene therapy biomaterials may be useful for regenerative medicine. Statement of SignificanceNot only is the formation of stable vasculature a challenge for engineering human tissues in vitro, but it is also of valuable interest to clinical applications such as peripheral artery disease. Previous studies using HIF-1α to induce vascular formation have been limited by the necessity of hypoxic chambers. It would be advantageous to simulate endogenous responses to hypoxia without the need for physical hypoxia. In this study, 3D vascular formation was shown to be inducible through non-viral gene delivery of HIF-1α with new polymeric nanocomplexes. A biodegradable polymer N'-(3-aminopropyl)-N,N-dimethylpropane-1,3-diamine end-modified poly(1,4-butanediol diacrylate-co-4-amino-1-butanol) demonstrates improved transfection of human adipose-derived stem cells. This nanobiotechnology could be a promising strategy for the creation of vasculature for tissue engineering and clinical applications.

Polylactic acid scaffolds obtained by 3D printing and modified by oxygen plasma

The purpose of tissue engineering is to repair, replace, and regenerate tissues and organs. For this aim, materials supports, as polylactic acid (PLA) are used. PLA is a thermoplastic polymer that presents biodegradability, biocompatibility and good processability. PLA scaffolds can accurately constructed by 3D printing. Then, the objectives of this work were to modify the hydrophobic surface of PLA scaffolds using oxygen plasma and to study the cell viability and proliferation. The characterization was done by AFM, contact angle, FTIR and studies of proliferation and cell viability. Results showed that the material acquired hydrophilic properties by the presence of oxygen reactive species and by contact angle decrease. It was also observed an increase in the surface roughness. We can conclude that although the surface modifications were effective and the PLA scaffolds were not cytotoxic, there were no improvements in the proliferation process with the studied osteo-1 lineage cells.

Development of reinforced aldehyde-modified kappa-carrageenan/gelatin film by incorporation of halloysite nanotubes for biomedical applications

Recently, with the progression in tissue engineering, the importance of biocompatible nanocomposite film with suitable properties for potential applications in the biomedical area has been more developed. In this work, nanocomposite films of aldehyde-modified Carrageenan/Gelatin/halloysite nanotubes (AD-Carr/Gel/HNTs) nanocomposite films were successfully fabricated by the solution casting process. Halloysite nanotubes (HNTs) with different concentrations (0.5, 1.0, and 1.5 wt%) loaded into the aldehyde-modified Carrageenan/Gelatin (AD-Carr/Gel). Meanwhile, the developed AD-Carr/Gel/HNTs nanocomposite films were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), mechanical property, water adsorption as well as in vitro degradation. The feasibility and capability of the nanocomposite films were further evaluated by hemocompatibility study, which showed that these nanocomposite films are hemocompatible. Besides, MTT assay revealed that the nanocomposite films are non-toxic, presenting the films as a good candidate to be used for tissue engineering purposes.

Extracellular Matrix-Derived Hydrogels as Biomaterial for Different Skeletal Muscle Tissue Replacements.

Recently, skeletal muscle represents a complex and challenging tissue to be generated in vitro for tissue engineering purposes. Several attempts have been pursued to develop hydrogels with different formulations resembling in vitro the characteristics of skeletal muscle tissue in vivo. This review article describes how different types of cell-laden hydrogels recapitulate the multiple interactions occurring between extracellular matrix (ECM) and muscle cells. A special attention is focused on the biochemical cues that affect myocytes morphology, adhesion, proliferation, and phenotype maintenance, underlining the importance of topographical cues exerted on the hydrogels to guide cellular orientation and facilitate myogenic differentiation and maturation. Moreover, we highlight the crucial role of 3D printing and bioreactors as useful platforms to finely control spatial deposition of cells into ECM based hydrogels and provide the skeletal muscle native-like tissue microenvironment, respectively.

Antimicrobial Mechanisms and Effectiveness of Graphene and Graphene-Functionalized Biomaterials. A Scope Review.

Bacterial infections represent nowadays the major reason of biomaterials implant failure, however, most of the available implantable materials do not hold antimicrobial properties, thus requiring antibiotic therapy once the infection occurs. The fast raising of antibiotic-resistant pathogens is making this approach as not more effective, leading to the only solution of device removal and causing devastating consequences for patients. Accordingly, there is a large research about alternative strategies based on the employment of materials holding intrinsic antibacterial properties in order to prevent infections. Between these new strategies, new technologies involving the use of carbon-based materials such as carbon nanotubes, fullerene, graphene and diamond-like carbon shown very promising results. In particular, graphene- and graphene-derived materials (GMs) demonstrated a broad range antibacterial activity toward bacteria, fungi and viruses. These antibacterial activities are attributed mainly to the direct physicochemical interaction between GMs and bacteria that cause a deadly deterioration of cellular components, principally proteins, lipids, and nucleic acids. In fact, GMs hold a high affinity to the membrane proteoglycans where they accumulate leading to membrane damages; similarly, after internalization they can interact with bacteria RNA/DNA hydrogen groups interrupting the replicative stage. Moreover, GMs can indirectly determine bacterial death by activating the inflammatory cascade due to active species generation after entering in the physiological environment. On the opposite, despite these bacteria-targeted activities, GMs have been successfully employed as pro-regenerative materials to favor tissue healing for different tissue engineering purposes. Taken into account these GMs biological properties, this review aims at explaining the antibacterial mechanisms underlying graphene as a promising material applicable in biomedical devices.

Zeolite in tissue engineering: Opportunities and challenges.

Tissue engineering and regenerative medicine follow a multidisciplinary attitude to the expansion and application of new materials for the treatment of different tissue defects. Typically, proper tissue regeneration is accomplished through concurrent biocompatibility and positive cellular activity. This can be resulted by the smart selection of platforms among bewildering arrays of structural possibilities with various porosity properties (ie, pore size, pore connectivity, etc). Among diverse porous structures, zeolite is known as a microporous tectosilicate that can potentially provide a biological microenvironment in tissue engineering applications. In addition, zeolite has been particularly appeared promising in wound dressing and bone‐ and tooth‐oriented scaffolds. The wide range of composition and hierarchical pore structure renders the zeolitic materials a unique character, particularly, for tissue engineering purposes. Despite such unique features, research on zeolitic platforms for tissue engineering has not been classically presented. In this review, we overview, classify, and categorize zeolitic platforms employed in biological and tissue engineering applications.

Development and prospect of tissue engineering in urology

Tissue engineering technology and stem cell research based on tissue engineering have made great progresses in overcoming the problems of tissue and organ damage, functional loss and surgical complications. Traditional method is to use biological substitute materials to repair tissues, while tissue engineering technology focuses on combining seed cells with biological materials to form biological tissues with the same structure and function as its own to repair tissue defects. The advantage is that such tissue engineering organs and tissues can solve the problem that the donor material is limited, and effectively reduce complications. The purpose of tissue engineering is to find suitable seed cells and biomaterials which can replace the biological function of original tissue and build suitable microenvironment in vivo. This paper mainly describes current technologies of tissue engineering in various fields of urology, and discusses the future trend of tissue engineering technology in the treatment of complex urinary diseases. The results of this study show that although there are relatively few clinical trials, the good results of the existing studies on animal models reveal a bright future of tissue engineering technology for the treatment of various urinary diseases.

Nanoarchitectured Structure and Surface Biofunctionality of Mesoporous Silica Nanoparticles.

Mesoporous silica nanoparticles (MSNs), one of the important porous materials, have garnered interest owing to their highly attractive physicochemical features and advantageous morphological attributes. They are of particular importance for use in diverse fields including, but not limited to, adsorption, catalysis, and medicine. Despite their intrinsic stable siliceous frameworks, excellent mechanical strength, and optimal morphological attributes, pristine MSNs suffer from poor drug loading efficiency, as well as compatibility and degradability issues for therapeutic, diagnostic, and tissue engineering purposes. Collectively, the desirable and beneficial properties of MSNs have been harnessed by modifying the surface of the siliceous frameworks through incorporating supramolecular assemblies and various metal species, and through incorporating supramolecular assemblies and various metal species and their conjugates. Substantial advancements of these innovative colloidal inorganic nanocontainers drive researchers in promoting them toward innovative applications like stimuli (light/ultrasound/magnetic)-responsive delivery-associated therapies with exceptional performance in vivo. Here, a brief overview of the fabrication of siliceous frameworks, along with discussions on the significant advances in engineering of MSNs, is provided. The scope of the advancement in terms of structural and physicochemical attributes and their effects on biomedical applications with a particular focus on recent studies is emphasized. Finally, interesting perspectives are recapitulated, along with the scope toward clinical translation.

Indirect selective laser sintering-printed microporous biphasic calcium phosphate scaffold promotes endogenous bone regeneration via activation of ERK1/2 signaling

The fabrication technique determines the physicochemical and biological properties of scaffolds, including the porosity, mechanical strength, osteoconductivity, and bone regenerative potential. Biphasic calcium phosphate (BCP)-based scaffolds are superior in bone tissue engineering due to their suitable physicochemical and biological properties. We developed an indirect selective laser sintering (SLS) printing strategy to fabricate 3D microporous BCP scaffolds for bone tissue engineering purposes. The green part of the BCP scaffold was fabricated by SLS at a relevant low temperature in the presence of epoxy resin (EP), and the remaining EP was decomposed and eliminated by a subsequent sintering process to obtain the microporous BCP scaffolds. Physicochemical properties, cell adhesion, biocompatibility, in vitro osteogenic potential, and rabbit critical-size cranial bone defect healing potential of the scaffolds were extensively evaluated. This indirect SLS printing eliminated the drawbacks of conventional direct SLS printing at high working temperatures, i.e. wavy deformation of the scaffold, hydroxyapatite decomposition, and conversion of β-tricalcium phosphate (TCP) to α-TCP. Among the scaffolds printed with various binder ratios (by weight) of BCP and EP, the scaffold with 50/50 binder ratio (S4) showed the highest mechanical strength and porosity with the smallest pore size. Scaffold S4 showed the highest effect on osteogenic differentiation of precursor cells in vitro, and this effect was ERK1/2 signaling-dependent. Scaffold S4 robustly promoted precursor cell homing, endogenous bone regeneration, and vascularization in rabbit critical-size cranial defects. In conclusion, BCP scaffolds fabricated by indirect SLS printing maintain the physicochemical properties of BCP and possess the capacity to recruit host precursor cells to the defect site and promote endogenous bone regeneration possibly via the activation of ERK1/2 signaling.

Tetracalcium phosphate and biphasic tetracalcium phosphate/tricalcium phosphate powders' effects evaluation on human osteoblasts.

Calcium ions levels in bone niches have been demonstrated to severely influence new bone formation. Osteoinductive scaffolds containing calcium have been largely studied to control the release of calcium in bone regeneration and tissue engineering purpose. The aim of the present study was, firstly, to synthesize two different resorbable calcium phosphate-based powders, thought to be reservoirs of calcium ions, and secondary, to investigate their effects on human osteoblasts, in order to develop a suitable titanium coating material. Tetracalcium phosphate (A450) and biphasic tetracalcium phosphatae/tricalcium phosphate (A850) powders were prepared with an innovative method. The presence of calcium phosphate structures was chemically confirmed with XRD. Furthermore, powders macroscopic aspect was observed with a stereomicroscope. For in-vitro experiments, human osteoblastic cells were cultured in the presence of A450 and A850, and assayed for viability and metabolic activity through Crystal Violet and MTT, respectively. Our synthesis led to the formation of calcium phosphates in both samples, even though A850 presented a higher level of crystallinity and a more powdery aspects than A450. Both the samples enhanced the viability of cultured cells, inhibiting cell metabolic activity in the case of A850, which furthermore showed to be internalized by cells. We developed two different kind of calcium phosphate-based powders and we tested their effect on human osteoblasts, underlying the possibility of use calcium phosphate-based coatings to enhance cell response on implantable materials.

Electroactive poly (p-phenylene sulfide)/r-graphene oxide/chitosan as a novel potential candidate for tissue engineering

Designing novel biomaterials for tissue engineering purpose is an obvious necessary considering ever increasing need for appropriate biocompatibility and properties to achieve the maximum regeneration. In this research, a new type of biomaterial based on poly (phenylene sulfide) (PPS) and reduced graphene oxide (rGO) was synthesized and applied within chitosan based hydrogel to evaluate its performance as a wound dressing potentially. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM) and compression tests were performed to assess suitability of composite biomaterial. Thermal behavior of the PPS/rGO composite was evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The PPS/rGO composition of 90: 10 (w/w) was selected because of having the highest biocompatibility and utilized in chitosan hydrogel. Chitosan hydrogel swelling ratio was declined from 800 to 200% by PPS/rGO addition; likewise, water vapor transition rate (WVTR) was dropped. A proper biocompatibility and cell attachment was confirmed, where porosity of ca. 80% appeared promising for tissue engineering uses. Overall, the result confirmed the appropriateness of PPS/rGO for tissue engineering uses.

Cellular Geometry Sensing at Different Length Scales and its Implications for Scaffold Design.

Geometrical cues provided by the intrinsic architecture of tissues and implanted biomaterials have a high relevance in controlling cellular behavior. Knowledge of how cells sense and subsequently respond to complex geometrical cues of various sizes and origins is needed to understand the role of the architecture of the extracellular environment as a cell-instructive parameter. This is of particular interest in the field of tissue engineering, where the success of scaffold-guided tissue regeneration largely depends on the formation of new tissue in a native-like organization in order to ensure proper tissue function. A well-considered internal scaffold design (i.e., the inner architecture of the porous structure) can largely contribute to the desired cell and tissue organization. Advances in scaffold production techniques for tissue engineering purposes in the last years have provided the possibility to accurately create scaffolds with defined macroscale external and microscale internal architectures. Using the knowledge of how cells sense geometrical cues of different size ranges can drive the rational design of scaffolds that control cellular and tissue architecture. This concise review addresses the recently gained knowledge of the sensory mechanisms of cells towards geometrical cues of different sizes (from the nanometer to millimeter scale) and points out how this insight can contribute to informed architectural scaffold designs.

Porous zinc scaffolds for bone tissue engineering applications: A novel additive manufacturing and casting approach.

As a degradable metal, zinc (Zn) has attracted an immense amount of interest as the next generation of bioresorbable implants thanks to its modest corrosion rate and its vital role in bone remodeling, yet very few studies have thoroughly investigated its functionality as a porous implant for bone tissue engineering purposes. Zn bone scaffolds with two different pore sizes of 900μm and 2mm were fabricated using additive manufacturing-produced templates combined with casting. The compressive properties, corrosion rates, biocompatibility, and antibacterial performance of the bioscaffolds were examined and compared to a non-porous control. The resulting textured and porous Zn scaffolds exhibit a fully interconnected pore structure with precise control over topology. As pore size and porosity increased, mechanical strength decreased, and corrosion rate accelerated. Cell adhesion and growth on scaffolds were enhanced after an ex vivo pretreatment method. In vitro cellular tests confirmed good biocompatibility of the scaffolds. As porosity increased, potent antibacterial rates were also observed. Taken together, these results demonstrate that Zn porous bone scaffolds are promising for orthopedic applications.

Mechanical modeling of silk fibroin/TiO2 and silk fibroin/fluoridated TiO2 nanocomposite scaffolds for bone tissue engineering

Biocompatible and biodegradable three-dimensional scaffolds are commonly porous which serve to provide suitable microenvironments for mechanical supporting and optimal cell growth. Silk fibroin (SF) is a natural and biomedical polymer with appropriate and improvable mechanical properties. Making a composite with a bioceramicas reinforcement is a general strategy to prepare a scaffold for hard tissue engineering applications. In the present study, SF was separately combined with titanium dioxide (TiO2) and fluoridated titanium dioxide nanoparticles (TiO2-F) as bioceramic reinforcements for bone tissue engineering purposes. At the first step, SF was extracted from Bombyx mori cocoons. Then, TiO2 nanoparticles were fluoridated by hydrofluoric acid. Afterward, SF/TiO2 and SF/TiO2-F nanocomposite scaffolds were prepared by freeze-drying method to obtain a porous microstructure. Both SF/TiO2 and SF/TiO2-F scaffolds contained 0, 5, 10, 15 and 20 wt% nanoparticles. To evaluate the efficacy of nanoparticles addition on the mechanical properties of the prepared scaffolds, their compressive properties were assayed. Likewise, the pores morphology and microstructure of the scaffolds were investigated using scanning electron microscopy. In addition, the porosity and density of the scaffolds were measured according to the Archimedes’ principle. Afterward, compressive modulus and microstructure of the prepared scaffolds were evaluated and modeled by Gibson–Ashby’s mechanical models. The results revealed that the compressive modulus predicted by the mechanical model exactly corresponds to the experimental one. The modeling approved the honeycomb structure of the prepared scaffolds which possess interconnected pores.

Plasma treatment and chitosan coating: a combination for improving PET surface properties

There are growing advantages of using electrospun poly(ethylene terephthalate) (PET) mats for tissue engineering purposes. However, because of poor surface physicochemical properties, using PET as a biomaterial may have some serious problems, such as poor wettability, inappropriate surface roughness and consequently weak cell attachment. To avoid such complications, in the present study, a combination of nanosecond pulsed plasma surface modification and chitosan coating was used as a versatile solution for tackling the mentioned problems. The effects of plasma treatment and chitosan coating were characterized by scanning electron microscopy, goniometry, weight loss study and X-ray photoelectron spectroscopy. The results showed that plasma modification resulted in the introduction of active polar oxygen (O)-containing functional groups onto the PET surface. The PET mat exhibited over 30 and 25% enhancement of hydroxyl and carboxyl groups after plasma treatment, respectively. Consequently, the oxygen/carbon (C) ratio increased from 0·36 to 0·73. These modifications led to improvement of physical properties, such as a significant increase in wettability and chitosan deposition. Chitosan coating introduced new nitrogen (N)-containing functional groups, which were absent in the uncoated PET. Plasma treatment increased the nitrogen/carbon ratio of chitosan-coated samples by a factor of 2. The obtained results suggest an enhancement in surface physicochemical properties with noteworthy potential applications in tissue engineering scaffolds.

The morphological properties and biocompatibility studies of synthesized nanocomposite foam from modified polyethersulfone/graphene oxide using supercritical CO2

In this study, octadecyl amine modified graphene oxide nanoparticles were used as a potential nucleating agent in the foaming process of the polymer, to increase its functions, especially for tissue engineering purposes. It has been established that the nucleation in the polymer depends on four factors of the nanoparticle weight percentage, foaming temperature, saturation pressure and the foaming time; however, it was found that the most important and effective variables are the nanoparticle weight percentage and then the foaming temperature followed by foaming time. Polymer foams have particularly good dimensional stability, and a proper change in the process variables can control the internal structure of the foam. In this study, adding 8% of modified graphene oxide as the nucleating agent, reduced the average diameter of polyethersulfone foam cells from 4.6 to 2.7 μm, or an increase of 40 °C in foaming temperature, increased the average diameter of the cells from 2.7 to 4.3 µm. Also, the toxicity tests and biocompatibility studies showed that the porous substance made by this method is nontoxic and can be used as a scaffold in the living bodies.

Halogen-Mediated Partial Oxidation of Polyvinyl Alcohol for Tissue Engineering Purposes.

Partial oxidation of polyvinyl alcohol (PVA) with potassium permanganate turned out to be an efficient method to fabricate smart scaffolds for tissue engineering, endowed with biodegradation and protein delivery capacity. This work considered for the first time the use of halogens (bromine, chlorine and iodine) as less aggressive agents than potassium permanganate to perform controlled PVA oxidation, in order to prevent degradation of polymer molecular size upon chemical modification. Oxidized PVA solutions were chemically characterized (i.e., dinitrophenylhydrazine assay, viscosity measurements, molecular size distribution) before preparing physically cross-linked hydrogels. Scaffolds were assessed for their mechanical properties and cell/tissue biocompatibiliy through cytotoxic extract test on IMR-90 fibroblasts and subcutaneous implantation into BALB/c mice. According to chemical investigations, bromine and iodine allowed for minor alteration of polymer molecular weight. Uniaxial tensile tests demonstrated that oxidized scaffolds had decreased mechanical resistance to deformation, suggesting tunable hydrogel stiffness. Finally, oxidized hydrogels exhibited high biocompatibility both in vitro and in vivo, resulting neither to be cytotoxic nor to elicit severe immunitary host reaction in comparison with atoxic PVA. In conclusion, PVA hydrogels oxidized by halogens were successfully fabricated in the effort of adapting polymer characteristics to specific tissue engineering applications.

DNA hypomethylation during MSC chondrogenesis occurs predominantly at enhancer regions

Regulation of transcription occurs in a cell type specific manner orchestrated by epigenetic mechanisms including DNA methylation. Methylation changes may also play a key role in lineage specification during stem cell differentiation. To further our understanding of epigenetic regulation in chondrocytes we characterised the DNA methylation changes during chondrogenesis of mesenchymal stem cells (MSCs) by Infinium 450 K methylation array. Significant DNA hypomethylation was identified during chondrogenic differentiation including changes at many key cartilage gene loci. Integration with chondrogenesis gene expression data revealed an enrichment of significant CpGs in upregulated genes, while characterisation of significant CpG loci indicated their predominant localisation to enhancer regions. Comparison with methylation profiles of other tissues, including healthy and diseased adult cartilage, identified chondrocyte-specific regions of hypomethylation and the overlap with differentially methylated CpGs in osteoarthritis. Taken together we have associated DNA methylation levels with the chondrocyte phenotype. The consequences of which has potential to improve cartilage generation for tissue engineering purposes and also to provide context for observed methylation changes in cartilage diseases such as osteoarthritis.