In Vitro Innovation of Tendon Tissue Engineering Strategies.

Tendinopathy is the term used to refer to tendon disorders. Spontaneous adult tendon healing results in scar tissue formation and fibrosis with suboptimal biomechanical properties, often resulting in poor and painful mobility. The biomechanical properties of the tissue are negatively affected. Adult tendons have a limited natural healing capacity, and often respond poorly to current treatments that frequently are focused on exercise, drug delivery, and surgical procedures. Therefore, it is of great importance to identify key molecular and cellular processes involved in the progression of tendinopathies to develop effective therapeutic strategies and drive the tissue toward regeneration. To treat tendon diseases and support tendon regeneration, cell-based therapy as well as tissue engineering approaches are considered options, though none can yet be considered conclusive in their reproduction of a safe and successful long-term solution for full microarchitecture and biomechanical tissue recovery. In vitro differentiation techniques are not yet fully validated. This review aims to compare different available tendon in vitro differentiation strategies to clarify the state of art regarding the differentiation process

Enzymatically crosslinked Tyramine-Gellan gum hydrogels as drug delivery system for rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by joint synovial inflammation, as well as cartilage and bone tissue destruction. Current strategies for the treatment of RA can reduce joint inflammation, but the treatment options still represent stability concerns since they are not sufficient and present a fast clearing. Thus, several drug delivery systems (DDS) have been advanced to tackle this limitation. Injectable gellan gum (GG) hydrogels, reduced by physical crosslinking methods, also being proposed as DDS, but this kind of crosslinking can produce hydrogels that become weaker in physiological conditions. Nevertheless, enzymatic crosslinking emerged as an alternative to increase mechanical strength, which can be adjusted by the degree of enzymatic crosslinking. In this study, tyramine-modified gellan gum (Ty-GG) hydrogels were developed via horseradish peroxidase (HRP) crosslinking; and betamethasone was encapsulated within, to increase the specificity and safety in the treatment of patients with RA. Physicochemical results showed that it was possible to modify GG with tyramine, with a degree of substitution of approximately 30%. They showed high mechanical strength and resistance, presenting a controlled betamethasone release profile over time. Ty-GG hydrogels also exhibited no cytotoxic effects and do not negatively affected the metabolic activity and proliferation of chondrogenic primary cells. Furthermore, the main goal was achieved since betamethasone-loaded Ty-GG hydrogels demonstrated to have a more effective therapeutic effect when compared with the administration of betamethasone alone. Therefore, the developed Ty-GG hydrogels represent a promising DDS and a reliable alternative to traditional treatments in patients with RANorte2020 project (“NORTE-08-5369-FSE-000044”), REMIX project (G.A. 778078 — REMIX — H2020-MSCA-RISE-2017), and Gilson Lab, Chonbuk National University, Republic of Korea. The FCT distinction attributed to J. Miguel Oliveira under the Investigator FCT program (IF/01285/2015) is also greatly acknowledged. C. Gonçalves also wish to acknowledge FCT for supporting her research (No. SFRH/BPD/94277/2013

A new viscosupplement based on partially hydrophobic hyaluronic acid: A comparative study

A novel partially hydrophobized derivative of hyaluronic acid (HYADD® 4), containing a low number of C16 side-chains per polysaccharide backbone, provides injectable hydrogels stabilized by side-chain hydrophobic interactions. The rheological properties of Hymovis®, a physical hydrogel based on the hyaluronic acid derivative HYADD® 4, were evaluated using as reference a solution of the parent natural polysaccharide, hyaluronic acid. The rheological measurements were performed both in flow and oscillation regimes at the physiological frequency values of the knee, typically spanning the range from 0.5 Hz (walking frequency) to 3 Hz (running frequency). Moreover, the viscoelastic features of Hymovis® were compared with the market-available viscosupplementation products in view of its use in joint diseases.The different behavior of the investigated materials in crossover frequency measurements and in structure recovery experiments can be explained on the basis of the structural and dynamic properties of the polymeric systems

Collective Dynamics and Transient Behavior of Partially Hydrophobic Hyaluronic Acid Chains

The unique performance of a partially hydrophobic derivative of hyaluronic acid, HYADD4, bearing 2–3 hexadecylic side chains every 100 repeating units, enables hydrogels based on this polymer to be suitably used as a viscosupplement to replace synovial fluid in stressed or injured articular joints. This contribution addresses: i) as to whether there is a self-assembly process driving the HYADD4 hydrogel stabilization and ii) what the characteristics of the long-range dynamics governing the macroscopic viscoelastic behavior are, and to what extent these features are different from those present in the parent polymer (i.e., hyaluronic acid). Mesoscale dynamic and static properties are interpreted in the light of “sticky reptation theory” and evaluated in combination with small-angle neutron scattering results

Synthesis and NMR characterization of new hyaluronan based no-donors

Nitric oxide (NO) and hyaluronic acid (HA), two species widely different in terms of molecular complexity and biological competence, are both known to play an important role in the wound healing process. To combine the properties of HA and NO, we synthesized new NO-donors based on hyaluronic acid derivatives exhibiting a controlled NO-release under physiological conditions (in vitro tests). Since two molecules of NO can form a covalent bond with secondary amines to yield structures, named NONO-ates, able to release NO in solution, we used spermidine bound to HA as the NO-linker. The HA-spermidine derivative was obtained by controlled HA amidation in aqueous media, activating the biopolymer carboxylate groups with a water soluble carbodiimide. The resulting derivative, soluble in water, was fully characterized by high field 1H and 13C NMR spectroscopy. The amount of grafting of spermidine on HA was determined by integration of suitable 1H NMR signals. In addition, cross-linked derivatives of HA were synthesized by the Ugi’s four-component reaction using formaldehyde, cyclohexylisocyanide, and spermidine. The HA-spermidine networks were characterized by 13C CP-MAS NMR spectroscopy. The degree of cross-linking of the networks was also determined. Finally, the release of NO from the swollen hydrogels freshly saturated with NO, in contact with aqueous media, was monitored by means of UV spectrophotometric measurements

The role of high molecular weight hyaluronic acid in mucoadhesion on an ocular surface model

Hyaluronic acid (HA) is frequently formulated in eye drops to improve the stability of the tear film by hydration and lubrication. Mucoadhesion is related to the ocular residence time and therefore to the effectiveness of the eye drops. The ocular residence time of the HA formulation is correlated with the ability of HA to create specific strong interactions in the ocular surface with the mucus layer, mainly composed of a mixture of secreted mucins (MUC; gel forming MUC5AC and MUC2) and shed membrane-bound soluble mucins (MUC1, MUC4, and MUC16). Dry eye disease (DED) is a multifactorial pathology of the preocular tear film with possible damage to the ocular surface classified in two types: (1) aqueous-deficient dry eye and (2) evaporative dry eye, caused by a decrease in goblet cell density that reduces MUC expression and/or by meibomian gland dysfunction, that results in a drop in the lipidic fraction of the tear film.In this work, the binding affinity between HA and MUC2 has been evaluated with three complementary ap-proaches because the secreted MUCs play a pivotal role in the viscoelastic properties of the tear film: 1. Rheo-logical analysis, measuring the mucoadhesive index and the complex viscosity in relation to MM (Molecular Mass) and concentration; 2. Fluorescence analysis, using a fluorescent hydrophobic probe, to investigate the conformational change of MUC2 during the interaction with the HA polymer; 3. Surface plasmon resonance analysis, used to measure the affinity between MUC2 (immobilized on the surface of a sensor chip) and the HA polymers that flowed on it at the molecular level.For all these tests, the mucoadhesive performance of the natural HA linearly increases with the MM, whereas cross-linked HA and other emollient and gelling agents (formulated in artificial tears) do not show the same mucoadhesive properties (with the exception of xanthan gum). The mucoadhesive performance of high MM HA has also been confirmed in conditions that simulate the pathological condition of the tear film during DED by decreasing the MUC2 or oleic acid concentration. Physico-chemical analysis of a series of marketed artificial tears confirms the linear correlation between the MM of the HA used in the products and the mucoadhesive index measured on the ocular surface model

Photocrosslinked hydrogels from coumarin derivatives of hyaluronic acid for tissue engineering applications

Hydrogels are an increasingly attractive choice in the fields of regenerative medicine, wound care and tissue engineering as important forms of bio-scaffolds. For many clinical needs, injectable in situ crosslinkable hydrogels are strongly preferred, due to treatment effectiveness and ease of use. In this study, hyaluronic acid (HA), containing side-arms linked to photo-active coumarin moieties, was used for the preparation of wall-to-wall hydrogels. This photocrosslinkable HA, hereafter called HA-TEG-coumarin, produces colourless aqueous solutions that solidify upon near-UV irradiation (at a specific wavelength of 365 nm) via a clean [2+2] photocycloaddition reaction, without by-products formation. The crosslinking event, a robust and non-cytotoxic process, does not require catalysts or radical initiators: in the field of hyaluronan photocrosslinking, this innovative feature is significant to ensure the whole biocompatibility and to avoid collateral reactions. Mechanical and rheological tests showed that hyaluronan derivatives became hydrogels after 3\u20135 min of irradiation, with average values for bulk and surface elastic moduli of about 32 kPa and 193 kPa, respectively. Fluorescence recovery after photobleaching (FRAP) assay showed that the hydrogels are porous and allow a good permeation for nutrients and growth factors. Cell metabolism and proliferation assays revealed that hydrogel-encapsulated fibroblasts maintained their viability and that HA-TEG-coumarin sustained the proliferation of non-adherent myoblasts. For all of these reasons and thanks to a safe free-radical approach, this novel hyaluronan coumarin derivative could be a good candidate for tissue engineering and regenerative medicine applications

Il sistema di sorveglianza OKkio alla SALUTE: il ruolo della scuola primaria nella promozione di stili di vita salutari. Risultati 2008 [Surveillance system OKkio alla SALUTE: the role of primary school in the promotion of healthy life style. Results of 2008]

In 2007 the Italian Ministry of Health/CCM promoted and funded the project "System of surveys of behavioral risks in ages 6-17", coordinated by the National Institute of Health. One of the aims of the project is the definition and implementation of a data collection system on the weight of primary school children, their eating habits, physical activity and school initiatives favoring the healthy growth of children, called "OKkio alla SALUTE". In 2008 the first survey of OKkio was conducted in 18 Italian regions. 45,590 third grade school children in 2610 classes participated. Information was collected from 2461 schools. The responses of the head teachers showed that 64% of the schools have a canteen, used by 70% of children. Only 12% of schools include the provision of a balanced mid-morning snack. Frequently there are educational activities related to physical activity and healthy eating that, in some cases, also involve the families of the children. 29% of the schools cannot guarantee two hours of physical activity as suggested by the school curriculum because of the lack or inadequacy of the gym or the structure of the timetables. The information gathered through the cooperation of school administrators, teachers and health workers, has helped to describe the major health educational activities of the school, that is confirmed to be the ideal venue for promoting healthy lifestyles in young people