Synthesis and biological activities of a library of glycosaminoglycans mimetic oligosaccharides

Next-Generation Biomaterials for Wound Healing: Development and Evaluation of Collagen Scaffolds Functionalized with a Heparan Sulfate Mimic and Fibroblast Growth Factor 2

Fibrosis after full-thickness wound healing-especially after severe burn wounds-remains a clinically relevant problem. Biomaterials that mimic the lost dermal extracellular matrix have shown promise but cannot completely prevent scar formation. We present a novel approach where porous type I collagen scaffolds were covalently functionalized with ReGeneRating Agent (RGTA®) OTR4120. RGTA® is a glycanase-resistant heparan sulfate mimetic that promotes regeneration when applied topically to chronic wounds. OTR4120 is able to capture fibroblast growth factor 2 (FGF-2), a heparan/heparin-binding growth factor that inhibits the activity of fibrosis-driving myofibroblasts. Scaffolds with various concentrations and distributions of OTR4120 were produced. When loaded with FGF-2, collagen-OTR4120 scaffolds demonstrated sustained release of FGF-2 compared to collagen-heparin scaffolds. Their anti-fibrotic potential was investigated in vitro by seeding primary human dermal fibroblasts on the scaffolds followed by stimulation with transforming growth factor β1 (TGF-β1) to induce myofibroblast differentiation. Collagen-OTR4120(-FGF-2) scaffolds diminished the gene expression levels of several myofibroblast markers. In absence of FGF-2 the collagen-OTR4120 scaffolds displayed an inherent anti-fibrotic effect, as the expression of two fibrotic markers (TGF-β1 and type I collagen) was diminished. This work highlights the potential of collagen-OTR4120 scaffolds as biomaterials to improve skin wound healing.

Structural Elucidation of Glycosaminoglycans in the Tissue of Flounder and Isolation of Chondroitin Sulfate C

Glycosaminoglycans (GAGs) are valuable bioactive polysaccharides with promising biomedical and pharmaceutical applications. In this study, we analyzed GAGs using HPLC-MS/MS from the bone (B), muscle (M), skin (S), and viscera (V) of Scophthalmus maximus (SM), Paralichthysi (P), Limanda ferruginea (LF), Cleisthenes herzensteini (G), Platichthys bicoloratus (PB), Pleuronichthys cornutus (PC), and Cleisthenes herzensteini (CH). Unsaturated disaccharide products were obtained by enzymatic hydrolysis of the GAGs and subjected to compositional analysis of chondroitin sulfate (CS), heparin sulfate (HS), and hyaluronic acid (HA), including the sulfation degree of CS and HS, as well as the content of each GAG. The contents of GAGs in the tissues and the sulfation degree differed significantly among the fish. The bone of S. maximus contained more than 12 μg of CS per mg of dry tissue. Although the fish typically contained high levels of CSA (CS-4S), some fish bone tissue exhibited elevated levels of CSC (CS-6S). The HS content was found to range from 10-150 ug/g, primarily distributed in viscera, with a predominant non-sulfated structure (HS-0S). The structure of HA is well-defined without sulfation modification. These analytical results are independent of biological classification. We provide a high-throughput rapid detection method for tissue samples using HPLC-MS/MS to rapidly screen ideal sources of GAG. On this basis, four kinds of CS were prepared and purified from flounder bone, and their molecular weight was determined to be 23-28 kDa by HPGPC-MALLS, and the disaccharide component unit was dominated by CS-6S, which is a potential substitute for CSC derived from shark cartilage.

Protective Effects of a synthetic glycosaminoglycan mimetic (OTR4132) in a rat immunotoxic lesion model of septohippocampal cholinergic degeneration

Using a partial hippocampal cholinergic denervation model, we assessed the effects of the RGTA^® named OTR4132, a synthetic heparan-mimetic biopolymer with neuroprotective/neurotrophic properties. Long-Evans male rats were injected with the cholinergic immunotoxin 192 IgG-saporin into the medial septum/diagonal band of Broca (0.37 µg); vehicle injections served as controls. Immediately after surgery, OTR4132 was injected into the lateral ventricles (0.25 µg/5 µl/rat) or intramuscularly (1.5 mg/kg). To determine whether OTR4132 reached the lesion site, some rats received intracerebroventricular (ICV) or intramuscular (I.M.) injections of fluorescent OTR4132. Rats were sacrificed at 4, 10, 20, or 60 days post-lesion (DPL). Fluorescein-labeled OTR4132 injected ICV or I.M. was found in the lesion from 4 to 20 DPL. Rats with partial hippocampal cholinergic denervation showed decreases in hippocampal acetylcholinesterase reaction products and in choline acetyltransferase-positive neurons in the medial septum. These lesions were the largest at 10 DPL and then remained stable until 60 DPL. Both hippocampal acetylcholinesterase reaction products and choline acetyltransferase-positive neurons in the medial septum effects were significantly attenuated in OTR4132-treated rats. These effects were not related to competition between OTR4132 and 192 IgG-saporin for the neurotrophin receptor P75 (p75^NTR), as OTR4132 treatment did not alter the internalization of Cy3-labelled 192 IgG. OTR4132 was more efficient at reducing the acetylcholinesterase reaction products and choline acetyltransferase-positive neurons than a comparable heparin dose used as a comparator. Using the slice superfusion technique, we found that the lesion-induced decrease in muscarinic autoreceptor sensitivity was abolished by intramuscular OTR4132. After partial cholinergic damage, OTR4132 was able to concentrate at the brain lesion site possibly due to the disruption of the blood-brain barrier and to exert structural and functional effects that hold promises for neuroprotection/neurotrophism.

Oligosaccharides from Traditional Chinese Herbal Medicines: A Review of Chemical Diversity and Biological Activities

Most of traditional Chinese herbal medicine (TCHM) substances come from medicinal plants, among which oligosaccharides have gradually attracted widespread attention at home and abroad due to their important biological activities and great medicinal potential. Numerous in vitro and in vivo experiments exhibited that oligosaccharides possess various activities, such as antitumor, anti-oxidation, modulate the gut microflora, anti-inflammatory, anti-infection, and immune-regulatory activities. Generally, biological activities are closely related to chemical structures, including molecular weight, monosaccharide composition, glycosidic bond connection, etc. The structural analysis of oligosaccharides is an important basis for studying their structure-activity relationship, but the structural diversity and complexity of carbohydrate compounds limit the study of oligosaccharides activities. Understanding the structures and biological functions of oligosaccharides is important for the development of new bioactive substances with natural oligosaccharides. This review provides a systematic introduction of the current knowledge of the chemical structures and biological activities of oligosaccharides. Most importantly, the reported chemical characteristics and biological activities of the famous TCHM oligosaccharides were briefly summarized, including Morinda officinalis, Rehmannia glutinosa, Arctium lappa, Polygala tenuifolia, Panax ginseng, Lycium barbarum and Astragalus membranaceus. TCHM oligosaccharides play an important role in nutrition, health care, disease diagnosis and prevention as well as have broad application prospects in the field of medicine.

Advances in the Medical Management of Neurotrophic Keratitis

Neurotrophic Keratitis (NK) is a degenerative disorder of the cornea characterized by decreased or absent sensory corneal innervation, corneal epitheliopathy and impaired healing.The clinical presentation of NK can range from persistent epithelial defects to corneal perforation and management is often both challenging and protracted. Historically, the management of NK has consisted of non-specific strategies to facilitate corneal epithelial healing such as lubrication, bandage contact lenses and tarsorrhaphy. Recent advances in the development of therapeutics for NK have provided new and efficacious targeted strategies for its management.In this article, we review recombinant human nerve growth factor (Cenegermin), currently approved for clinical use in the United States and Europe, as well as other promising therapeutic options that are in pre-clinical development such as thymosine β4, connexin43 inhibitors, and artificial extracellular matrix components.

A heparan sulfate-based matrix therapy reduces brain damage and enhances functional recovery following stroke

Alteration of the extracellular matrix (ECM) is one of the major events in the pathogenesis of brain lesions following ischemic stroke. Heparan sulfate mimetics (HSm) are synthetic pharmacologically active polysaccharides that promote ECM remodeling and tissue regeneration in various types of lesions. HSm bind to growth factors, protect them from enzymatic degradation and increase their bioavailability, which promotes tissue repair. As the ECM is altered during stroke and HSm have been shown to restore the ECM, we investigated the potential of HSm4131 (also named RGTA-4131®) to protect brain tissue and promote regeneration and plasticity after a stroke. Methods: Ischemic stroke was induced in rats using transient (1 h) intraluminal middle cerebral artery occlusion (MCAo). Animals were assigned to the treatment (HSm4131; 0.1, 0.5, 1.5, or 5 mg/kg) or vehicle control (saline) groups at different times (1, 2.5 or 6 h) after MCAo. Brain damage was assessed by MRI for the acute (2 days) and chronic (14 days) phases post-occlusion. Functional deficits were evaluated with a battery of sensorimotor behavioral tests. HSm4131-^99mTc biodistribution in the ischemic brain was analyzed between 5 min and 3 h following middle cerebral artery reperfusion. Heparan sulfate distribution and cellular reactions, including angiogenesis and neurogenesis, were evaluated by immunohistochemistry, and growth factor gene expression (VEGF-A, Ang-2) was quantified by RT-PCR. Results: HSm4131, administered intravenously after stroke induction, located and remained in the ischemic hemisphere. HSm4131 conferred long-lasting neuroprotection, and significantly reduced functional deficits with no alteration of physiological parameters. It also restored the ECM, and increased brain plasticity processes, i.e., angiogenesis and neurogenesis, in the affected brain hemisphere. Conclusion: HSm represent a promising ECM-based therapeutic strategy to protect and repair the brain after a stroke and favor functional recovery.

Periodontal reconstruction by heparan sulfate mimetic-based matrix therapy in Porphyromonas gingivalis-infected mice

BACKGROUND

Periodontitis is a set of chronic inflammatory diseases affecting the supporting structures of the teeth, during which a persistent release of lytic enzymes and inflammatory mediators causes a self-perpetuating vicious cycle of tissue destruction and repair. A matrix-based therapy using a heparan sulfate (HS) analogue called ReGeneraTing Agent (RGTA) replaces destroyed HS by binding to available heparin-binding sites of structural molecules, leading to restoration of tissue homeostasis in several inflammatory tissue injuries, including a hamster periodontitis model.

METHODS

The ability of RGTA to restore the periodontium was tested in a model of Porphyromonas gingivalis-infected Balb/cByJ mice. After 12 weeks of disease induction, mice were treated weekly with saline or RGTA (1.5 mg/kg) for 8 weeks. Data were analyzed by histomorphometry.

RESULTS

RGTA treatment restored macroscopic bone loss. This was related to (1) a significant reduction in gingival inflammation assessed by a decrease in infiltrated connective tissue, particularly in cells expressing interleukin 1ß, an inflammatory mediator selected as a marker of inflammation; (2) a normalization of bone resorption parameters, i.e. number, activation and activity of osteoclasts, and number of preosteoclasts; (3) a powerful bone formation reaction. The Sharpey's fibers of the periodontal ligament recovered their alkaline phosphatase coating. This was obtained while P. gingivalis infection was maintained throughout the treatment period.

CONCLUSIONS

RGTA treatment was able to control the chronic inflammation characteristic of periodontitis and blocked destruction of periodontal structures. It ensured tissue regeneration with recovery of the periodontium's anatomy.

A New Matrix Therapy Agent for Faster Corneal Healing and Less Ocular Discomfort Following Epi-off Accelerated Corneal Cross-linking in Progressive Keratoconus

PURPOSE

To investigate the hypothesis that a new matrix therapy agent (ReGeneraTing Agent, [RGTA]) would speed up the corneal reepithelialization, improve stromal healing, and reduce ocular symptoms after epi-off corneal cross-linking (CXL).

METHODS

Sixty eyes of 60 patients with progressive keratoconus were enrolled in the study. Epi-off accelerated CXL was performed in all patients. Sixty eyes were randomized into two groups according to use of RGTA eye drops prior to contact lens fitting at the end. Identical medical agents were started postoperatively for the two groups. All participants were monitored on 3 consecutive days after the CXL. Ocular pain, burning, stinging, tearing, photophobia, conjunctival hyperemia, and corneal healing status were evaluated.

RESULTS

By day 2, 25 eyes (83.3%) with RGTA revealed complete healing compared to 4 eyes (13.3%) that revealed complete healing in the control group (P < .001). All eyes had complete corneal epithelial defect closure by day 3 in both groups. Ocular pain scores were lower in the RGTA group on days 0, 1, and 2 (all P < .05). Burning scores were lower on days 1 and 2; stinging scores on days 2 and 3; tearing scores on days 2 and 3; and photophobia on days 1 and 2 (P < .05) in the RGTA group compared to the control group.

CONCLUSIONS

RGTA ophthalmic solution facilitates corneal healing by reconstructing the extracellular matrix in the wound area, leading to an earlier relief of symptoms for patients. [J Refract Surg. 2017;33(3):163-170.].

Wound healing in the eye: Therapeutic prospects

In order to maintain a smooth optical surface the corneal epithelium has to continuously renew itself so as to maintain its function as a barrier to fluctuating external surroundings and various environmental insults. After trauma, the cornea typically re-epithelializes promptly thereby minimizing the risk of infection, opacification or perforation. A persistent epithelial defect (PED) is usually referred to as a non-healing epithelial lesion after approximately two weeks of treatment with standard therapies to no avail. They occur following exposure to toxic agents, mechanical injury, and ocular surface infections and are associated with significant clinical morbidity in patients, resulting in discomfort or visual loss. In the case of deeper corneal injury and corneal pathology the wound healing cascade can also extend to the corneal stroma, the layer below the epithelium. Although significant progress has been made in recent years, pharmaco-therapeutic agents that promote corneal healing remain limited. This article serves as a review of current standard therapies, recently introduced alternative therapies gaining in popularity, and a look into the newest developments into ocular wound healing.

Deciphering the Role of Sulfonated Unit in Heparin-Mimicking Polymer to Promote Neural Differentiation of Embryonic Stem Cells

Glycosaminoglycans (GAGs), especially heparin and heparan sulfate (HS), hold great potential for inducing the neural differentiation of embryonic stem cells (ESCs) and have brought new hope for the treatment of neurological diseases. However, the disadvantages of natural heparin/HS, such as difficulty in isolating them with a sufficient amount, highly heterogeneous structure, and the risk of immune responses, have limited their further therapeutic applications. Thus, there is a great demand for stable, controllable, and well-defined synthetic alternatives of heparin/HS with more effective biological functions. In this study, based upon a previously proposed unit-recombination strategy, several heparin-mimicking polymers were synthesized by integrating glucosamine-like 2-methacrylamido glucopyranose monomers (MAG) with three sulfonated units in different structural forms, and their effects on cell proliferation, the pluripotency, and the differentiation of ESCs were carefully studied. The results showed that all the copolymers had good cytocompatibility and displayed much better bioactivity in promoting the neural differentiation of ESCs as compared to natural heparin; copolymers with different sulfonated units exhibited different levels of promoting ability; among them, copolymer with 3-sulfopropyl acrylate (SPA) as a sulfonated unit was the most potent in promoting the neural differentiation of ESCs; the promoting effect is dependent on the molecular weight and concentration of P(MAG-co-SPA), with the highest levels occurring at the intermediate molecular weight and concentration. These results clearly demonstrated that the sulfonated unit in the copolymers played an important role in determining the promoting effect on ESCs' neural differentiation; SPA was identified as the most potent sulfonated unit for copolymer with the strongest promoting ability. The possible reason for sulfonated unit structure as a vital factor influencing the ability of the copolymers may be attributed to the difference in electrostatic and steric hindrance effect. The synthetic heparin-mimicking polymers obtained here can offer an effective alternative to heparin/HS and have great therapeutic potential for nervous system diseases.

RGTA® or ReGeneraTing Agents mimic heparan sulfate in regenerative medicine: from concept to curing patients

The importance of extracellular matrix (ECM) integrity in maintaining normal tissue function is highlighted by numerous pathologies and situations of acute and chronic injury associated with dysregulation or destruction of ECM components. Heparan sulfate (HS) is a key component of the ECM, where it fulfils important functions associated with tissue homeostasis. Its degradation following tissue injury disrupts this delicate equilibrium and may impair the wound healing process. ReGeneraTing Agents (RGTA^®s) are polysaccharides specifically designed to replace degraded HS in injured tissues. The unique properties of RGTA^® (resistance to degradation, binding and protection of ECM structural and signaling proteins, like HS) permit the reconstruction of the ECM, restoring both structural and biochemical functions to this essential substrate, and facilitating the processes of tissue repair and regeneration. Here, we review 25 years of research surrounding this HS mimic, supporting the mode of action, pre-clinical studies and therapeutic efficacy of RGTA^® in the clinic, and discuss the potential of RGTA^® in new branches of regenerative medicine.

Identification of a Pro-Angiogenic Potential and Cellular Uptake Mechanism of a LMW Highly Sulfated Fraction of Fucoidan from Ascophyllum nodosum

Herein we investigate the structure/function relationships of fucoidans from Ascophyllum nodosum to analyze their pro-angiogenic effect and cellular uptake in native and glycosaminoglycan-free (GAG-free) human endothelial cells (HUVECs). Fucoidans are marine sulfated polysaccharides, which act as glycosaminoglycans mimetics. We hypothesized that the size and sulfation rate of fucoidans influence their ability to induce pro-angiogenic processes independently of GAGs. We collected two fractions of fucoidans, Low and Medium Molecular Weight Fucoidan (LMWF and MMWF, respectively) by size exclusion chromatography and characterized their composition (sulfate, fucose and uronic acid) by colorimetric measurement and Raman and FT-IR spectroscopy. The high affinities of fractionated fucoidans to heparin binding proteins were confirmed by Surface Plasmon Resonance. We evidenced that LMWF has a higher pro-angiogenic (2D-angiogenesis on Matrigel) and pro-migratory (Boyden chamber) potential on HUVECs, compared to MMWF. Interestingly, in a GAG-free HUVECs model, LMWF kept a pro-angiogenic potential. Finally, to evaluate the association of LMWF-induced biological effects and its cellular uptake, we analyzed by confocal microscopy the GAGs involvement in the internalization of a fluorescent LMWF. The fluorescent LMWF was mainly internalized through HUVEC clathrin-dependent endocytosis in which GAGs were partially involved. In conclusion, a better characterization of the relationships between the fucoidan structure and its pro-angiogenic potential in GAG-free endothelial cells was required to identify an adapted fucoidan to enhance vascular repair in ischemia.

RGTA®-based matrix therapy - A new branch of regenerative medicine in locomotion

Matrix therapy is an innovative, minimally invasive approach in the field of regenerative medicine, that aims to promote tissue regeneration by reconstructing the cellular microenvironment following tissue injury. This approach has significant therapeutic potential in the treatment of pathologies characterized by tissue inflammation and damage, or following injury, conditions which can be incapacitating and cost-consuming. Heparan sulfate mimics, termed ReGeneraTing Agents (RGTA^®s) have emerged as a unifying approach to treat these diverse pathologies. Today, skin and corneal healing topical products have already been used in clinics, demonstrating a proof of concept in humans. In this review, we present key evidence that RGTA^®s regenerate damaged tissue in bone, muscle, tendon and nerve, with astonishing results. In animal models of bone surgical defects and inflammatory bone loss, RGTA^® induced healing of injured bones by controlling inflammation and bone resorption, and stimulated bone formation by coordinating vascularization, recruitment and differentiation of competent cells from specific niches, restoring tissue quality to that of uninjured tissue, evoking true regeneration. In models of muscle injury, RGTA^® had marked effects on healing speed and quality, evidenced by increased muscle fiber density, maturation, vascularization and reduced fibrosis, more mature motor endplates and functional recovery. Applications merging RGTA^®-based matrix therapy and cell therapy, combining Extra-Cellular Matrix reconstruction with cells required for optimal tissue repair show significant promise. Hence restoration of the proper microenvironment is a new paradigm in regenerative medicine. Harnessing the potential of RGTA^® in this brave, new vision of regenerative therapy will therefore be the focus of future studies.

Surface Proteoglycans as Mediators in Bacterial Pathogens Infections

Infectious diseases remain an important global health problem. The interaction of a wide range of pathogen bacteria with host cells from many different tissues is frequently mediated by proteoglycans. These compounds are ubiquitous complex molecules which are not only involved in adherence and colonization, but can also participate in other steps of pathogenesis. To overcome the problem of microbial resistance to antibiotics new therapeutic agents could be developed based on the characteristics of the interaction of pathogens with proteoglycans.

In vitro and in vivo evaluation of cord blood hematopoietic stem and progenitor cells amplified with glycosaminoglycan mimetic

BACKGROUND

Expansion protocols aim at both increasing the number of umbilical cord blood (UCB) hematopoietic stem cells and progenitor cells (HSPCs) and reducing the period of neutropenia in UCB HSPC graft. Because glycosaminoglycans (GAGs) are known to be important components of the hematopoietic niche and to modulate growth factor effects, we explored the use of GAG mimetic OTR4131 to potentiate HSPC's in vitro expansion and in vivo engraftment.

METHODS

UCB CD34+ cells were expanded with serum-free medium, SCF, TPO, FLT3-lig and G-CSF during 12 days in the absence or the presence of increasing OTR4131 concentrations (0-100 μg/mL). Proliferation ratio, cell viability and phenotype, functional assays, migration capacity and NOD-scid/γc(-/-) mice engraftment were assessed after expansion.

RESULTS

At Day 12, ratios of cell expansion were not significantly increased by OTR4131 treatment. Better total nucleated cell viability was observed with the use of 1 μg/mL GAG mimetic compared to control (89.6 % ± 3.7 % and 79.9 % ± 3.3 %, respectively). Phenotype analysis showed a decrease of monocyte lineage in the presence of OTR4131 and HSPC migration capacity was diminished when GAG mimetic was used at 10 μg/mL (10.9 % ± 4.1 % vs. 52.9 % ± 17.9 % for control). HSPC clonogenic capacities were similar whatever the culture conditions. Finally, in vivo experiments revealed that mice successfully engrafted in all conditions, even if some differences were observed during the first month. Three months after graft, bone marrow chimerism and blood subpopulations were similar in both groups.

CONCLUSIONS

UCB HSPCs ex-vivo expansion in the presence of OTR4131 is a safe approach that did not modify cell function and engraftment capacities. In our experimental conditions, the use of a GAG mimetic did not, however, allow increasing cell expansion or optimizing their in vivo engraftment.

Poly(vinyl sulfonate) Facilitates bFGF-Induced Cell Proliferation

Heparin is a highly sulfated polysaccharide and is useful because of its diverse biological functions. However, because of batch-to-batch variability and other factors, there is significant interest in preparing biomimetics of heparin. To identify polymeric heparin mimetics, a cell-based screening assay was developed in cells that express fibroblast growth factor receptors (FGFRs) but not heparan sulfate proteoglycans. Various sulfated and sulfonated polymers were screened, and poly(vinyl sulfonate) (pVS) was identified as the strongest heparin-mimicking polymer in its ability to enhance binding of basic fibroblast growth factor (bFGF) to FGFR. The results were confirmed by an ELISA-based receptor-binding assay. Different molecular weights of pVS polymer were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were able to facilitate dimerization of FGFRs leading to cell proliferation in FGFR-expressing cells, and no size dependence was observed. The data showed that pVS is comparable to heparin in these assays. In addition, pVS was not cytotoxic to fibroblast cells up to at least 1 mg/mL. Together this data indicates that pVS should be explored further as a replacement for heparin.

A microscopic view on the renal endothelial glycocalyx

Endothelial cells perform key homeostatic functions such as regulating blood flow, permeability, and aiding immune surveillance for pathogens. While endothelial activation serves normal physiological adaptation, maladaptation of these endothelial functions has been identified as an important effector mechanism in the progression of renal disease as well as the associated development of cardiovascular disease. The primary interface between blood and the endothelium is the glycocalyx. This carbohydrate-rich gel-like structure with its associated proteins mediates most of the regulatory functions of the endothelium. Because the endothelial glycocalyx is a highly dynamic and fragile structure ex vivo, and traditional tissue processing for staining and perfusion-fixation usually results in a partial or complete loss of the glycocalyx, studying its dimensions and function has proven to be challenging. In this review, we will outline the core functions of the glycocalyx and focus on different techniques to study structure-function relationships in kidney and vasculature.

Healing efficiency of oligosaccharides generated from almond gum (Prunus amygdalus) on dermal wounds of adult rats

Almond gum is a naturally occurring polymer produced by almond trees and shrubs. Its abundance, as well as its low cost production makes it a potential feedstock for use in food and pharmaceuticals. In this regard, almond gum oligosaccharides were enzymatically generated, purified and their monosaccharide composition assessed using gas chromatography-flame ionization detector. Oligosaccharide analyses show that the most prominent residues were galactose and arabinose with traces of xylose, rhamnose, glucose and mannose. The glycosyl linkage positions were analyzed using gas chromatography - mass spectrometry showing a main chain composed of galactose units [→3)-Gal-(1→] branched mainly with arabinose residues [Ara-(1→]. The potent role of the generated oligosaccharides on rats wound healing was investigated. They have been applied either alone or supplemented, as active substance, with cream formulation, on full-thickness wound created on the dorsum of the rats. The effect of oligosaccharides was assessed by measuring the wound closure percentage, reaching an average of around 100% when applied alone or supplemented to cream formulation. The healing percentage for the control group was only 74.3% at the same day. The histological evaluation of skin sections visualized by light microscopy revealed an improved collagen deposition and an increased fibroblast and vascular densities.

New strategies for cartilage regeneration exploiting selected glycosaminoglycans to enhance cell fate determination

Most research strategies for cartilage tissue engineering use extended culture with complex media loaded with costly GFs (growth factors) to drive tissue assembly and yet they result in the production of cartilage with inferior mechanical and structural properties compared with the natural tissue. Recent evidence suggests that GAGs (glycosaminoglycans) incorporated into tissue engineering scaffolds can sequester and/or activate GFs and thereby more effectively mimic the natural ECM (extracellular matrix). Such approaches may have potential for the improvement of cartilage engineering. However, natural GAGs are structurally complex and heterogeneous, making structure–function relationships hard to determine and clinical translation difficult. Importantly, subfractions of GAGs with specific chain lengths and sulfation patterns have been shown to activate key signalling processes during stem cell differentiation. In addition, recently, GAGs have been bound to synthetic biomaterials, such as electrospun scaffolds and hydrogels, in biologically active conformations, and methods to purify and select affinity-matched GAGs for specific GFs have also been developed. The identification and use of specific GAG moieties to promote chondrogenesis is therefore an exciting new avenue of research. Combining these with synthetic biomaterials may allow a more effective mimicry of the natural ECM, reduction in the need for expensive GFs, and perhaps the deposition of an articular cartilage-like matrix in a clinically relevant manner.

Glycosaminoglycan mimetic associated to human mesenchymal stem cell-based scaffolds inhibit ectopic bone formation, but induce angiogenesis in vivo

Tissue engineering approaches to stimulate bone formation currently combine bioactive scaffolds with osteocompetent human mesenchymal stem cells (hMSC). Moreover, osteogenic and angiogenic factors are required to promote differentiation and survival of hMSC through improved vascularization through the damaged extracellular matrix (ECM). Glycosaminoglycans (GAGs) are ECM compounds acting as modulators of heparin-binding protein activities during bone development and regenerative processes. GAG mimetics have been proposed as ECM stabilizers and were previously described for their positive effects on bone formation and angiogenesis after local treatment. Here, we developed a strategy associating the GAG mimetic [OTR4120] with bone substitutes to optimize stem cell-based therapeutic products. We showed that [OTR4120] was able to potentiate proliferation, migration, and osteogenic differentiation of hMSC in vitro. Its link to tricalcium phosphate/hydroxyapatite scaffolds improved their colonization by hMSC. Surprisingly, when these combinations were tested in an ectopic model of bone formation in immunodeficient mice, the GAG mimetics inhibit bone formation induced by hMSC and promoted an osteoclastic activity. Moreover, the inflammatory response was modulated, and the peri-implant vascularization stimulated. All together, these findings further support the ability of GAG mimetics to organize the local ECM to coordinate the host response toward the implanted biomaterial, and to inhibit the abnormal bone formation process on a subcutaneous ectopic site.

Tetrasaccharide iteration synthesis of a heparin-like dodecasaccharide and radiolabelling for in vivo tissue distribution studies

Heparin-like oligosaccharides mediate numerous important biological interactions, of which many are implicated in various diseases. Synthetic improvements are central to the development of such oligosaccharides as therapeutics and, in addition, there are no methods to elucidate the pharmacokinetics of structurally defined heparin-like oligosaccharides. Here we report an efficient two-cycle [4+4+4] tetrasaccharide-iteration-based approach for rapid chemical synthesis of a structurally defined heparin-related dodecasaccharide, combined with the incorporation of a latent aldehyde tag, unmasked in the final step of chemical synthesis, providing a generic end group for labelling/conjugation. We exploit this latent aldehyde tag for ³H radiolabelling to provide the first example of this kind of agent for monitoring in vivo tissue distribution and in vivo stability of a biologically active, structurally defined heparin related dodecasaccharide. Such studies are critical for the development of related saccharide therapeutics, and the data here establish that a biologically active, synthetic, heparin-like dodecasaccharide provides good organ distribution, and serum lifetimes relevant to developing future oligosaccharide therapeutics.

Heparin-like oligosaccharides are implicated in various diseases. Hansen et al. report an efficient two-cycle [4+4+4] tetrasaccharide-iteration-based approach to synthesize a structurally defined heparin dodecasaccharide with a latent aldehyde tag for labelling and conjugation.