Glycosaminoglycans Research Articles

Advances of Sulfonated Hyaluronic Acid in Biomaterials and Coatings—A Review

Hyaluronic acid (HA) is a non-sulfated glycosaminoglycan (GAG) that is a versatile material whose biological, chemical, and physical characteristics can be deeply tuned to modifications. However, HA is easy to decompose by hyaluronidase in vivo, and this process will reduce its structure and function stability during application. The sulfonation of HA can improve its stability under the action of hyaluronidase. Sulfated hyaluronic acid (S-HA) can be synthesized by many methods, and it shows significantly slower degradation by hyaluronidase compared with HA. In addition, negatively charged S-HA has other advantages such as anti-adhesive activity, anti-inflammatory, macromolecules by electrostatic interactions, stable site absorption of positively charged molecules, and enhancement of growth factor binding ability. It has numerous applications in medical (anti-aging, inflammation, tissue regeneration, cancer therapy, wound healing, and drug delivery) and cosmetics as biomaterials and coatings. In this article, the advances of S-HA for potential application of biomaterials and biomedical coatings will be reviewed and comprehensively discussed.

Immunomodulatory potential of mesenchymal stromal cell-derived extracellular vesicles in chondrocyte inflammation.

Osteoarthritis (OA) affects a large percentage of the population worldwide. Current surgical and nonsurgical concepts for treating OA only result in symptom-modifying effects. However, there is no disease-modifying therapy available. Extracellular vesicles released by mesenchymal stem/stromal cells (MSC-EV) are promising agents to positively influence joint homeostasis in the osteoarthritic surroundings. This pilot study aimed to investigate the effect of characterized MSC-EVs on chondrogenesis in a 3D chondrocyte inflammation model with the pro-inflammatory cytokine TNFα. Bovine articular chondrocytes were expanded and transferred into pellet culture at passage 3. TNFα, human MSC-EV preparations (MSC-EV batches 41.5-EVi1 and 84-EVi), EVs from human platelet lysate (hPL4-EV), or the combination of TNFα and EVs were supplemented. To assess the effect of MSC-EVs in the chondrocyte inflammation model after 14 days, DNA, glycosaminoglycan (GAG), total collagen, IL-6, and NO release were quantified, and gene expression of anabolic (COL-II, aggrecan, COMP, and PRG-4), catabolic (MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5), dedifferentiation (COL-I), hypertrophy (COL-X, VEGF), and inflammatory (IL-8) markers were analyzed; histological evaluation was performed using safranin O/Fast Green staining and immunohistochemistry of COL I and II. For statistical evaluation, nonparametric tests were chosen with a significance level of p < 0.05. TNFα supplementation resulted in catabolic stimulation with increased levels of NO and IL-6, upregulation of catabolic gene expression, and downregulation of anabolic markers. These findings were supported by a decrease in matrix differentiation (COL-II). Supplementation of EVs resulted in an upregulation of the chondrogenic marker PRG-4. All MSC-EV preparations significantly increased GAG retention per pellet. In contrast, catabolic markers and IL-8 expression were upregulated by 41.5-EVi1. Regarding protein levels, IL-6 and NO release were increased by 41.5-EVi1. Histologic and immunohistochemical evaluations indicated a higher differentiation potential of chondrocytes treated with 84-EVi. MSC-EVs can positively influence chondrocyte matrix production in pro-inflammatory surroundings, but can also stimulate inflammation. In this study MSC-EV 41.5-EVi1 supplementation increased chondrocyte inflammation, whereas MSC-84-EVi supplementation resulted a higher chondrogenic potential of chondrocytes in 3D pellet culture. In summary, the selected MSC-EVs exhibited promising chondrogenic effects indicating their significant potential for the treatment of OA; however, the functional heterogeneity in MSC-EV preparations has to be solved.

Biomechanical, Healing and Therapeutic Effects of Stretching: A Comprehensive Review

Characterized in biomedical terms, stretching exercises have been defined as movements applied by external and/or internal forces to increase muscle and joint flexibility, decrease muscle stiffness, elevate the joint range of motion (ROM), increase the length of the “muscle–tendon” morpho-functional unit, and improve joint, muscle, and tendon movements, contraction, and relaxation. The present review examines and summarizes the initial and recent literature data related to the biomechanical, physiological, and therapeutic effects of static stretching (SS) on flexibility and other physiological characteristics of the main structure and the “joint–ligament–tendon–muscle” functional unit. The healing and therapeutic effects of SS, combined with other rehabilitation techniques (massage, foam rolling with and without vibrations, hot/cold therapy, etc.), are discussed in relation to the creation of individual (patient-specific) or group programs for the treatment and prevention of joint injuries, as well as for the improvement of performance in sports. From a theoretical point of view, the role of SS in positively affecting the composition of the connective tissue matrix is pointed out: types I–III collagen syntheses, hyaluronic acid, and glycosaminoglycan (GAG) turnover under the influence of the transforming growth factor beta-1 (TGF-β-1). Different variables, such as collagen type, biochemistry, elongation, and elasticity, are used as molecular biomarkers. Recent studies have indicated that static progressive stretching therapy can prevent/reduce the development of arthrogenic contractures, joint capsule fibrosis, and muscle stiffness and requires new clinical applications. Combined stretching techniques have been proposed and applied in medicine and sports, depending on their long- and short-term effects on variables, such as the ROM, EMG activity, and muscle stiffness. The results obtained are of theoretical and practical interest for the development of new experimental, mathematical, and computational models and the creation of efficient therapeutic programs. The healing effects of SS on the main structural and functional unit—“joint–ligament–tendon–muscle”—need further investigation, which can clarify and evaluate the benefits of SS in prophylaxis and the treatment of joint injuries in healthy and ill individuals and in older adults, compared to young, active, and well-trained persons, as well as compared to professional athletes.

Effect of the chicken zp1 gene on osteoblast mineralization

The aim of this study was to clone the chicken zp1 gene encoding zona pellucida 1 (Zp1) and investigate its tissues expression profile and its effect on osteoblast mineralization. The expression level of zp1 was quantified in various tissues of laying hens and in the tibia of the pre- and post-sexual maturity by RT-qPCR. Zp1 overexpressed vector was transfected into chicken calvarial osteoblasts which were induced differentiation for 8 days, and the extracellular mineral and the expression of mineralization-related genes were detected. The full-length chicken zp1 gene is 3 045 bp, encoding 958 amino acids residuals, and has two N-glycosylation sites. The highest expression level of the zp1 gene was found in the liver, followed by the tibia and yolk membrane, while no expression was detected in the heart and eggshell gland. Compared with the pre-sexual maturity hens, the concentration of estrogen (E2) in plasma, the content of glycosaminoglycan (GAG) and the expression level of the zp1 gene in the tibia with post-sexual maturity were higher. The extracellular matrix and the level of osteoblast mineralization-related genes showed a significantly upregulated expression in chicken calvarial osteoblasts with Zp1 overexpressed and addition of estrogen. The expression of the zp1 gene is tissue-specific and positively regulated osteoblast mineralization under the action of estrogen, laying the foundation for elucidating the functional properties of Zp1 in chicken bones during the egg production period.

Biopolymer collagen-chitosan scaffold containing Aloe vera for chondrogenic efficacy on cartilage tissue engineering

The chondrogenic efficacy of aloe vera blended collagen-chitosan (COL-CS-AV) porous scaffold was investigated using articular chondrocytes in a standard condition. Cytocompatibility was analyzed using fluorescent dyes (calcein AM/ethidium bromide) and the viable cells were quantified by MTT assay. Glycosaminoglycan (GAG) content of ECM was estimated by using 1, 9-Dimethyl methylene Blue (DMMB). The total RNA content was quantified and the cartilage specific genes (col2a1, Acan) were amplified by reverse transcription-PCR from the cell lysate of the scaffolds. Histological examination was made using Haematoxylin and Eosin (H&E), safranin-O, masson's trichrome, alcian blue, and alizarin red to stain the specific component of ECM secreted on the construct. The cartilage specific collagen type II was estimated by immunohistochemistry using monoclonal type II collagen antibody. The results of these studies proved that COL-CS-AV scaffold has more chondrogenic efficacy than COL-CS, thus the aloe vera blend COL-CS-AV scaffold might be used as suitable candidate for cartilage tissue engineering.

Alterations of Plasmatic Biomarkers of Neurodegeneration in Mucopolysaccharidosis Type II Patients Under Enzyme Replacement Therapy.

Mucopolysaccharidosis type II (MPS II) is a disorder caused by a deficient activity of iduronate-2-sulfatase, a lysosomal enzyme responsible for degrading glycosaminoglycans (GAGs). The abnormal storage of GAGs within lysosomes disrupts cellular homeostasis and leads to a severe symptomatology. Patients present neuropsychiatric impairment characterized by mental retardation and impaired cognition. The aim of this study was to quantify four neurodegeneration biomarkers in plasma: brain-derived neurotrophic factor (BDNF), platelet-derived growth factor (PDGF-AA), neural cell adhesion molecule (NCAM) and cathepsin-D, as well as to identify possible correlations with urinary GAGs in seven patients undergoing treatment with ERT (Elaprase® 0.5 mg/kg of body weight). Patients with both severe and attenuated forms of MPS II showed signs of neurodegeneration in neuroimaging exams. Patients have a decrease in BDNF and PDGF-AA concentrations, and an increase in NCAM level compared to controls. No alterations in cathepsin-D concentration were seen. GAGs levels were higher in patients than in controls, but no significant correlations between GAGs and biomarkers were observed. These results evidence that patients have neurodegeneration and that monitoring these biomarkers might be useful for assessing this process. To this date, this is the first work to analyze these plasmatic markers of neurodegeneration in patients.

A glycomic workflow for LC–MS/MS analysis of urine glycosaminoglycan biomarkers in mucopolysaccharidoses

In recent years, several rational designed therapies have been developed for treatment of mucopolysaccharidoses (MPS), a group of inherited metabolic disorders in which glycosaminoglycans (GAGs) are accumulated in various tissues and organs. Thus, improved disease-specific biomarkers for diagnosis and monitoring treatment efficacy are of paramount importance. Specific non-reducing end GAG structures (GAG-NREs) have become promising biomarkers for MPS, as the compositions of the GAG-NREs depend on the nature of the lysosomal enzyme deficiency, thereby creating a specific pattern for each subgroup. However, there is yet no straightforward clinical laboratory platform which can assay all MPS-related GAG-NREs in one single analysis. Here, we developed and applied a GAG domain mapping approach for analyses of urine samples of ten MPS patients with various MPS diagnoses and corresponding aged-matched controls. We describe a nano-LC–MS/MS method of GAG-NRE profiling, utilizing 2-aminobenzamide reductive amination labeling to improve the sensitivity and the chromatographic resolution. Diagnostic urinary GAG-NREs were identified for MPS types IH/IS, II, IIIc, IVa and VI, corroborating GAG-NRE as biomarkers for these known enzyme deficiencies. Furthermore, a significant reduction of diagnostic urinary GAG-NREs in MPS IH (n = 2) and MPS VI (n = 1) patients under treatment was demonstrated. We argue that this straightforward glycomic workflow, designed for the clinical analysis of MPS-related GAG-NREs in one single analysis, will be of value for expanding the use of GAG-NREs as biomarkers for MPS diagnosis and treatment monitoring.

A One-Bead-Per-Saccharide (1BPS) Model for Glycosaminoglycans.

Glycosaminoglycans (GAGs) are polysaccharide compounds that play key roles in various biological processes. GAGs are important structural components of cartilage and the extracellular matrix of the brain. Due to the large size of these polysaccharides, coarse-grained approaches are indispensable for modeling these biopolymers. We develop a one-bead-per-saccharide model of chondroitin sulfates and hyaluronic acid based on an existing three-bead-per-saccharide coarse-grained model. Our coarse graining is carried out by using iterative Boltzmann inversion (IBI), including an additional coupling potential to incorporate the correlation between dihedral angles. The predictions of the model are verified against those of the existing three-bead-per-saccharin model and the experimental radius of gyration for hyaluronic acid.

Microfluidic‐Assisted Interfacial Complexation of Extracellular Matrix Components to Mimic the Properties of Neural Tissues

AbstractAnisotropy is an important cue for neural organization during morphogenesis and healing, contributing to the mechanical and functional properties of neural tissues. The ability to replicate such anisotropy in vitro holds great promise for the development of effective regeneration strategies. In this work, interfacial polyelectrolyte complexation (IPC) is applied to fabricate microfibers from charged ECM components without any chemical modification. Using flow‐focusing microfluidics, collagen (Col) and glycosaminoglycans (GAGs), such as chondroitin sulfate (CS) or heparin (Hep), form Col/CS and Col/Hep interfacial complexes that coalesce as IPC microfibers. These fibers are flexible and absorb large amounts of water but remain stable under physiological conditions. At these conditions, the tensile strength of the assembled Col/GAG microfibers is similar to the strength of the neural tissue. The fibers are biocompatible and biofunctional; PC12 neural cells adhere and orient longitudinally to the fibers. Moreover, Col/CS microfibers promote the formation of neural processes. The results demonstrate that the microfluidic‐assisted IPC complexation enables the assembly of ECM mimics by synergetic integration of anisotropic, chemical, and mechanical cues that boost the development of neural cells.

The relationship between keratan sulfate glycosaminoglycan density and mechanical stiffening of CXL treatment

The corneal stroma is primarily composed of collagen fibrils, proteoglycans, and glycosaminoglycans (GAGs). It is known that corneal crosslinking (CXL) treatment improves mechanical properties of the cornea. However, the influence of stromal composition on the strengthening effect of CXL procedure has not been thoroughly investigated. The primary objective of the present research was to characterize the effect of keratan sulfate (KS) GAGs on the efficacy of CXL therapy. To this end, the CXL method was used to crosslink porcine corneal samples from which KS GAGs were enzymatically removed by keratanase II enzyme. Alcian blue staining was done to confirm the successful digestion of GAGs and uniaxial tensile experiments were performed for characterizing corneal mechanical properties. The influence of GAG removal and CXL treatment on resistance of corneal samples against enzymatic pepsin degradation was also quantified. It was found that removal of KS GAGs significantly softened corneal tensile properties (P < 0.05). Moreover, the CXL therapy significantly increased the tensile stiffness of GAG-depleted strips (P < 0.05). GAG-depleted corneal buttons were dissolved in the pepsin digestion solution significantly faster than control samples (P < 0.05). The CXL treatment significantly increased the time needed for complete pepsin digestion of GAG-depleted disks (P < 0.05). Based on these observations, we concluded that KS GAGs play a significant role in defining tensile properties and structural integrity of porcine cornea. Furthermore, the stiffening influence of the CXL treatment does not significantly depend on the density of corneal KS GAGs. The findings of the present study provided new information on the relation between corneal composition and CXL procedure mechanical effects.

The effect of the sulfation patterns of dermatan and chondroitin sulfate from vertebrates and ascidians on their neuritogenic and neuroprotective properties

Neurodegeneration is caused by the progressive loss of the structure and function of neurons, leading to cell death, and it is the main cause of many neurodegenerative diseases. Many molecules, such as glycosaminoglycans (GAGs), have been studied for their potential to prevent or treat these diseases. They are widespread in nature and perform an important role in neuritogenesis and neuroprotection. Here we investigated the neuritogenic and neuroprotective role of Phallusia nigra dermatan sulfate (PnD2,6S) and compared it with two distinct structures of chondroitin sulfate (C6S) and dermatan sulfate (D4S). For this study, a neuro 2A murine neuroblastoma cell line was used, and a chemical lesion was induced by the pesticide rotenone (ROT). We observed that PnD2,6S + ROT had a better neuritogenic effect than either C6S + ROT or D4S + ROT at a lower concentration (0.05 μg/mL). When evaluating the mitochondrial membrane potential, PnD2,6S showed a neuroprotective effect at a concentration of 0.4 μg/mL. These data indicate different mechanisms underlying this neuronal potential, in which the sulfation pattern is important for neuritogenic activity, while for neuroprotection all DS/CS structures had similar effects. This finding leads to a better understanding the chemical structures of PnD2,6S, C6S, and D4S and their therapeutic potential.

Extraction of dermatan sulfate using ionic liquid-assisted enzymatic digestion: An efficient approach

Dermatan sulfate is one of the major glycosaminoglycan (GAG) present in the animal hides, which is a waste/byproduct from meat industry. Efficient utilization of these meat industry wastes is garnering attention because these wastes render a possibility for their conversion into useful products. With the increased concerns over health, various initiatives have been developed to permit more efficient utilization of these by-products and thereby directly impacting environmental sustainability. Herein, we demonstrate for the first time an efficient and environmentally safe ionic liquid-assisted enzymatic process for the extraction of dermatan sulfate from buffalo hides. Dermatan sulfate has been extracted, separated, and purified from the GAG mixture using IL-assisted enzymatic digestions and chromatographic separations. NMR, FT-IR, and ESI-MS measurements showed typical characteristic peaks for dermatan sulfate. The advantages of this eco-friendly process adopted include i) use of fewer chemicals, ii) elimination of harsh chemicals, iii) elimination of various steps and sub-steps, iv) reduction in process time (12 h), and v) increase in extraction yield by 75% when compared to conventional enzymatic process (57%). Thus, the use of ionic liquids alongside enzymes will serve as an efficient methodology for the futuristic development of these derived GAGs for their potential applications.

Transition Networks Unveil Disorder-to-Order Transformations in Aβ Caused by Glycosaminoglycans or Lipids

The aggregation of amyloid-β (Aβ) peptides, particularly of Aβ1−42, has been linked to the pathogenesis of Alzheimer’s disease. In this study, we focus on the conformational change of Aβ1−42 in the presence of glycosaminoglycans (GAGs) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipids using molecular dynamics simulations. We analyze the conformational changes that occur in Aβ by extracting the key structural features that are then used to generate transition networks. Using the same three features per network highlights the transitions from intrinsically disordered states ubiquitous in Aβ1−42 in solution to more compact states arising from stable β-hairpin formation when Aβ1−42 is in the vicinity of a GAG molecule, and even more compact states characterized by a α-helix or β-sheet structures when Aβ1−42 interacts with a POPC lipid cluster. We show that the molecular mechanisms underlying these transitions from disorder to order are different for the Aβ1−42/GAG and Aβ1−42/POPC systems. While in the latter the hydrophobicity provided by the lipid tails facilitates the folding of Aβ1−42, in the case of GAG there are hardly any intermolecular Aβ1−42–GAG interactions. Instead, GAG removes sodium ions from the peptide, allowing stronger electrostatic interactions within the peptide that stabilize a β-hairpin. Our results contribute to the growing knowledge of the role of GAGs and lipids in the conformational preferences of the Aβ peptide, which in turn influences its aggregation into toxic oligomers and amyloid fibrils.

Morquio A Syndrome Case Report and Literature Review

Morquio A syndrome is an autosomal recessive disorder, one of 50 lysosomal storage diseases (LSDs), and is caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS). Deficiency of this enzyme causes specific glycosaminoglycan (GAG) accumulation: keratan sulfate (KS) and chondroitin-6-sulfate (C6S). The majority of KS is produced in the cartilage, therefore, the undegraded substrates accumulate mainly in cartilage and in its extracelluar matrix (ECM), causing direct leads to direct impact on cartilage and bone development and leading to the resultant systemic skeletal spondyloepiphyseal dysplasia. Chondrogenesis, the earliest phase of skeletal formation that leads to cartilage and bone formation is controlled by cellular interactions with the ECM, growth and differentiation factors and other molecules that affect signaling pathways and transcription factors in a temporal-spatial manner. In Morquio A patients, in early childhood or even at birth, the cartilage is disrupted presumably as a result of abnormal chondrogenesis and/or endochondral ossification. The unique clinical features are characterized by a marked short stature, odontoid hypoplasia, protrusion of the chest, kyphoscoliosis, platyspondyly, coxa valga, abnormal gait, and laxity of joints.In spite of many descriptions of the unique clinical manifestations, diagnosis delay still occurs. The pathogenesis of systemic skeletal dysplasia in Morquio A syndrome remains an enigmatic challenge. In this review article, screening, diagnosis, pathogenesis and current and future therapies of Morquio A are discussed.

Actin Cytoskeleton Polymerization and Focal Adhesion as Important Factors in the Pathomechanism and Potential Targets of Mucopolysaccharidosis Treatment.

The main approach used in the current therapy of mucopolysaccharidosis (MPS) is to reduce the levels of glycosaminoglycans (GAGs) in cells, the deposits considered to be the main cause of the disease. Previous studies have revealed significant differences in the expression of genes encoding proteins involved in many processes, like those related to actin filaments, in MPS cells. Since the regulation of actin filaments is essential for the intracellular transport of specific molecules, the process which may affect the course of MPSs, the aim of this study was to evaluate the changes that occur in the actin cytoskeleton and focal adhesion in cells derived from patients with this disease, as well as in the MPS I mouse model, and to assess whether they could be potential therapeutic targets for different MPS types. Western-blotting, flow cytometry and transcriptomic analyses were employed to address these issues. The levels of the key proteins involved in the studied processes, before and after specific treatment, were assessed. We have also analyzed transcripts whose levels were significantly altered in MPS cells. We identified genes whose expressions were changed in the majority of MPS types and those with particularly highly altered expression. For the first time, significant changes in the expression of genes involved in the actin cytoskeleton structure/functions were revealed which may be considered as an additional element in the pathogenesis of MPSs. Our results suggest the possibility of using the actin cytoskeleton as a potential target in therapeutic approaches for this disease.

Interspecies comparison of temporomandibular joint condylar cartilage extracellular matrix from macro to microscopy

Interspecies comparisons of the extracellular matrix of temporomandibular joint (TMJ) condylar cartilage are necessary to elucidate the mechanisms underlying its superior mechanical properties, to guide the construction of animal models of TMJ-related diseases, and to establish standards for the engineering of TMJ condylar cartilage. Here we characterize and compare TMJ condylar cartilage from six different species from a materials science perspective, including structure, composition and mechanical properties from the macroscopic to the microscopic level. The gross morphology showed obvious interspecies differences in size and shape, which may be related to the different joint motion patterns. Although the condylar cartilage of all species can be divided histologically into a superficial fibrous layer and a deep hyaline layer, there are significant interspecies differences in the microstructure of the fibrils in the two layers, mainly in the diameter of the fibrils. Compositionally, there were no significant differences in collagen composition between species, but the content of glycosaminoglycans (GAGs) decreased progressively with increasing body size, with the same results obtained by Safranin O staining and biochemical analysis. Mechanically, the elastic modulus of mouse condylar cartilage was significantly higher than that of the other species and tended to decrease with increasing body size. This study shows that the TMJ condylar cartilage of different species has its own specific structure-composition-mechanics matching characteristics for their unique masticatory stress dissipation, and differences in fibril diameter and GAGs content may be the two ultimate factors influencing the differences in cartilage mechanical properties between species, while the condylar cartilage of pigs is most similar to that of humans, suggesting that pigs may be a suitable animal model for TMJ studies.

V3: an enigmatic isoform of the proteoglycan versican.

V3 is an isoform of the extracellular matrix (ECM) proteoglycan (PG) versican generated through alternative splicing of the versican gene such that the two major exons coding for sequences in the protein core that support chondroitin sulfate (CS) glycosaminoglycan (GAG) chain attachment are excluded. Thus, versican V3 isoform carries no GAGs. A survey of PubMed reveals only 50 publications specifically on V3 versican, so it is a very understudied member of the versican family, partly because to date there are no antibodies that can distinguish V3 from the CS-carrying isoforms of versican, that is, to facilitate functional and mechanistic studies. However, a number of in vitro and in vivo studies have identified the expression of the V3 transcript during different phases of development and in disease, and selective overexpression of V3 has shown dramatic phenotypic effects in "gain and loss of function" studies in experimental models. Thus, we thought it would be useful and instructive to discuss the discovery, characterization, and the putative biological importance of the enigmatic V3 isoform of versican.

Poster 152: Detrimental Effects of Chlorhexidine on Articular Cartilage Viability, Matrix, and Mechanics

Objectives: Chlorhexidine gluconate (CHG) is commonly used in antiseptic irrigation solutions for bacterial decontamination during orthopaedic surgery. Although the chondrotoxicity of CHG to articular cartilage has been reported, CHG irrigation is utilized by some surgeons to limit surgical site infection and to salvage grafts after accidental contamination during joint surgery. The full extent of CHG irrigation-related chondrotoxicity, as well as its effects on articular cartilage extracellular matrix and mechanical properties, are unknown. The purpose of this study was to determine the in vitro effects of a single one-minute CHG exposure on the viability, biochemical content, and mechanics of native articular cartilage explants. Methods: Articular cartilage explants (n=6 per group) were harvested from the femoral condyles of the porcine stifle and sectioned at the tidemark. Explants were bathed in Irrisept® chlorhexidine solution (0.05% CHG in sterile water) at varying concentrations (0% control, 0.01% CHG, and 0.05% CHG) to stimulate surgical irrigation for 1 minute, followed by complete phosphate-buffered saline wash and culture. After seven days of culture in chondrogenic medium, the explants were analyzed for viability (live/dead assay); collagen content (hydroxyproline assay); glycosaminoglycan (GAG) content (dimethyl methylene blue assay); and compressive mechanical testing (creep indentation testing). Statistical analyses were performed using a one-way ANOVA with post hoc Tukey test. Results: Seven days after CHG exposure, a dose-dependent decrease in mean chondrocyte viability was observed in the CHG groups (p&lt;0.001), with &lt;3% viability observed in the 0.05% CHG group (Figure 1). There was no significant difference in mean collagen content per wet weight among groups. Conversely, 0.05% CHG exposure led to a decrease in mean GAG per wet weight compared to negative control (p=0.029) and 0.01% CHG (p=0.046) (Figure 2). These changes in GAG content corresponded to observed changes in the compressive mechanical properties of the explants. A dose-dependent decrease in mean aggregate modulus and shear modulus was observed after CHG exposure (p&lt;0.029), indicating weakening of the cartilage matrix and increased deformation in response to compressive loads (Figure 3). Conclusions: One-minute CHG exposure to articular cartilage explants led to dose-dependent decreases in chondrocyte viability, GAG content, and compressive mechanical properties. These detrimental effects were observed for both 0.05% and 0.01% CHG concentrations. There is a paucity of literature examining the effects of CHG on articular cartilage matrix and mechanics, and the findings of this study suggest a lack of matrix maintenance following cell death, raising concern for risk of mechanical failure of the cartilage tissue. Clinicians should be judicious regarding the use of CHG irrigation at these concentrations in the presence of native articular cartilage.

Ocular perspective of mucopolysaccharidosis

Abstract A hereditary condition known as mucopolysaccharidosis is characterized by a lack of enzymes necessary for the breakdown of glycosaminoglycans (GAGs). GAG is improperly broken down, resulting in extensive lysosomal buildup throughout the different organs. From minor systemic and ocular involvement to a severe phenotype that can be lethal even in the few months of life, the clinical spectrum varies. Physical and cognitive skills are further hampered by visual impairment brought on by corneal clouding, retinopathy, and optic nerve involvement. Enzyme replacement therapy and bone marrow transplants are two examples of treatment methods that help patients live longer and better lives. The preferred course of treatment for people with visibly significant corneal clouding is keratoplasty. A thorough preoperative evaluation and patient counseling regarding the anticipated visual outcomes as well as postoperative complications such as graft re-opacification, rejection, and glaucoma should be conducted. Future therapies such as substrate reduction therapy and targeted gene therapy may be able to reverse corneal clouding. These therapeutic approaches are still in the testing phase.

Evaluation of Non-Cross Linked Xeno-Free Hyaluronic Acid Solutions as Visco Elastic Biomaterials.

Hyaluronic acid (HA) is a naturally occurring biodegradable, high molecular weight, non-sulfated glycosaminoglycan (GAG) polymer known for its excellent biocompatibility. HA-based products are widely used as viscosupplements, dermal fillers, and ophthalmic lubricants in clinical settings. Although animal and bacterial-derived HA are commonly reported, plant-sourced HA is not frequently reported. In this study, we have evaluated various viscoelastic properties of one such plant-based HA solution and propose them as an alternative to existing animal/bacteria-sourced HA. The viscoelastic properties of plant-sourced HA solution of various concentrations (0.1%, 0.5%, 1%, and 2% in PBS) were studied using a rheometer at 37°C. Flow curves, amplitude sweep studies, and frequency sweep studies were performed and compared for all HA solutions. The HA solutions displayed shear-thinning behavior, which is an important characteristic of an injectable biomaterial. The 0.1 and 0.5% HA were found to have viscoelastic properties appropriate for eye lubricants, while 1 and 2% HA solutions showed properties suitable for soft tissue fillers. Frequency sweep studies indicated that all the samples are typically viscoelastic liquids with a loss modulus (G″) higher than the storage modulus (G'). This indicated that the samples needed further processing like crosslinking of HA or using higher molecular weight HA to be suitable as viscosupplements. However, the frequency sweep studies also indicated that these solutions can be used as soft tissue fillers of any type based on the G' and tan δ values. The plant-sourced HA solutions are found to exhibit good shear-thinning properties with viscoelastic properties suitable for eye lubricants and soft tissue fillers. However, to be used as viscosupplements, the viscoelastic properties of HA solutions have to be further modified through non-toxic crosslinking strategies, and hydrophobic derivatives as well as by using high molecular weight HAs.