Angiogenic Potential of Gellan-Gum-Based Hydrogels for Application in Nucleus Pulposus Regeneration: In Vivo Study
Department of Polymer Engineering, 3B's Research Group-Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Guimarães, Portugal. Tissue Engineering Part A
(Impact Factor: 4.64).
03/2012; 18(11-12):1203-12. DOI: 10.1089/ten.TEA.2011.0632
Hydrogels for nucleus pulposus (NP) regeneration should be able to comprise a nonangiogenic or even antiangiogenic feature. Gellan gum (GG)-based hydrogels have been reported to possess adequate properties for being used as NP substitutes in acellular and cellular strategies, due to its ability to support cell encapsulation, adequate mechanical properties, and noncytotoxicity. In this study, the angiogenic response of GG-based hydrogels was investigated by performing the chorioallantoic membrane assay. The convergence of macroscopic blood vessels toward the GG, ionic-crosslinked methacrylated GG (iGG-MA), and photo-crosslinked methacrylated GG (phGG-MA) hydrogel discs was quantified. Gelatin sponge (GSp) and filter paper (FP) alone and with vascular endothelial growth factor were used as controls of angiogenesis. The images obtained were digitally processed and analyzed by three independent observers. The macroscopic blood vessel quantification demonstrated that the GG-based hydrogels are not angiogenic as compared with FP controls. No statistical differences between the GG-based hydrogels tested in respect to its angiogenic ability were observed. Hematoxylin and eosin staining and SNA-lectin immunohistochemistry assay indicated that the iGG-MA and phGG-MA hydrogels do not allow the ingrowth of chick endothelial cells, following 4 days of implantation. On the contrary, GG, GSp, and FP controls allowed cell infiltration. The histological data also indicated that the GG-based hydrogels do not elicit any acute inflammatory response. The results showed that the GG, iGG-MA, and phGG-MA hydrogels present different permeability to cells but functioned as a physical barrier for vascular invasion. These hydrogels present promising and tunable properties for being used as NP substitutes in the treatment of degenerative intervertebral disc.
Available from: Joaquim Miguel Oliveira
- "For NP regeneration alone, numerous hydrogels have been developed to support native NP cells (NPCs) (i.e., acellular scaffolds, or for carrying mesenchymal stem cells or NPCs, alginate , carboxymethylcellulose , and hyaluronan , among others  ). Methacrylated gellan gum (GG- MA) hydrogels have been suggested as a suitable platform both to support NPCs and to avoid angiogenesis, which contributes to maintaining hypoxia levels inside the NP, thus stimulating NPC's phenotype  . "
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ABSTRACT: Degeneration of the intervertebral disc (IVD) represents a significant musculoskeletal disease burden. Tissue Engineering has been proposing several strategies comprising the use of biodegradable materials to prepare scaffolds that can present similar mechanical properties to native IVD tissues. However, this might be insufficient, since the patient’s intervertebral space geometry must be replicated to allow the appropriate implant fixation and integration. Herein, it is proposed the use of Reverse Engineering and Rapid Prototyping techniques applied to rabbit models aiming to prepare custom-tailored annulus fibrosus scaffolds. The IVD reverse engineered architecture was obtained by means of micro-Computed Tomography acquisition and three-dimensional modelling, resulting in a computer-aided design that replicates the original rabbit IVD. Later, a fused deposition modelling three-dimensional printer was used to produce the scaffolds with different geometries from the computer-aided design, using polycaprolactone (PCL) with 100% infill density. The microstructure of the PCL scaffolds was investigated by scanning electron microscopy (SEM), which allowed observing an adequate fusion adhesion between layers. The SEM images revealed that, until a moderate resolution, the porosities manually designed in the computer-aided design model were successfully replicated. The PCL scaffolds’ three-dimensional architecture was also assessed by means of micro-Computed Tomography analysis. Compressive stiffness was determined using a mechanical testing system. Results showed higher values as compared to that of human IVDs (5.9-6.7 kN/mm vs. 1.2 kN/mm, respectively). In vitro studies were performed to investigate possible cytotoxicity of the polycaprolactone scaffolds’ leachables. The results showed that the custom-tailored PCL scaffolds do not have any deleterious cytotoxic effect over annulus fibrosus cells and mouse lung fibroblasts cell line. This study proposed a simple, rapid and low-cost strategy to fabricate custom-tailored annulus fibrosus scaffolds. In the future, this strategy might be used in association with nucleus pulposus regeneration strategies that can possibly allow developing tissue engineered total disc replacement implants specific to each patient, aiming at full IVD regeneration.
Available from: Lucília Silva
- "When compared to other animal-extracted, natural polymers, for instance the hyaluronic acid extracted from rooster combs , it represents a lower risk of disease transmission. So far, the possibility of tuning GG hydrogels in terms of cross-linking degree and related mechanical properties, as well as their ability for in situ gelation, has allowed GG hydrogels to be proposed for different regenerative medical applications    . On the other hand, like most natural polymers , its relatively poor mechanical properties narrow the scope of its applications in tissue engineering . "
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ABSTRACT: This work presents bioactive-glass-reinforced gellan-gum spongy-like hydrogels (GG-BAG) as novel hydrophilic materials for use as the scaffolding in bone-tissue engineering. The reinforcement with bioactive-glass particles resulted in an improvement to the microstructure and to the mechanical properties of the material. These mechanical properties were found to be dependent on the composition and improved with the amount of bioactive glass; however, values necessary to accommodate biomechanical loading were not achieved in this study. Nevertheless, by incorporating the bioactive-glass particles, the composite material acquired the ability to form an apatite layer when soaked in simulated body fluid. Furthermore, human-adipose-derived stem cells were able to adhere and spread within the gellan-gum, spongy-like hydrogels reinforced with the bioactive glass, and remain viable, which is an important result when considering their use in bone-tissue engineering. Thus, hydrogels based on gellan gum and bioactive glass are promising biomaterials for use either alone or with cells, and with the potential for use in osteogenic differentiation.
Available from: Tomasz Osmałek
- "The value of Young's modulus was similar to the value reported for human nucleus pulposus (Leahy and Hukins, 2001). It was also shown that methacrylated gellan protected nucleus pulposus by acting as a barrier for angiogenesis (Silva-Correia et al., 2012). Shin et al. (2012) designed hydrogels for encapsulation of human fibroblasts consisting of two interpenetrating networks of methacrylated gellan gum and methacrylated gelatin. "
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ABSTRACT: Over the past few decades, microbial polysaccharides have been under intense investigation due to their advantageous physicochemical properties. A great structural diversity of these biomolecules has led to multiple applications in food industry, personal care products, pharmacy and medicine. Currently, one of the most widely studied and fully described member of this group is gellan. It is a linear polymer produced by Sphingomonas elodea. A polymer chain of gellan consists of a tetrasaccharide repeating unit of l-rhamnose, d-glucose and d-glucuronate. So far most of the studies have been focused on the application of gellan as a food ingredient. However, due to the unique structure and beneficial properties, gellan is currently described as a potent multifunctional additive for various pharmaceutical products. Specific gelling properties in different media led to the development of controlled release forms based on gellan. Various formulations have been studied including oral, ophthalmic, nasal and other. Recent reports suggest that gellan-based materials can also be used in regenerative medicine, stomatology or gene transfer technology.
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