Regenerative potential of glycosaminoglycans for skin and bone

Small and porous ossicles, with flat stapes footplate and incudal fractures in the oim mouse model of osteogenesis imperfecta

Hearing loss affects approximately 70 % of individuals with osteogenesis imperfecta (OI), a genetic connective tissue disorder characterized by bone fragility and deformities. No effective treatments exist for OI hearing loss, and its etiology is unknown limiting the development of new targeted therapies. This work investigates the impact of OI type I collagen mutations on the ossicle bone properties in the homozygous oim mouse model of severe OI, which is known to exhibit hearing loss. The morphology and porosity of the ossicles of 14-week-old oim and wild-type mice were analyzed using high-resolution synchrotron radiation microtomography. Additionally, the collagen fibers structure, bone tissue composition and mechanical properties were evaluated through second harmonic generation microscopy, Raman spectroscopy, and nanoindentation. The results demonstrated that oim ossicles are small, highly porous with an elevated lacunar number density, a flat stapes footplate and a small malleal processus brevis. One-in-two oim ossicles had incudomalleal joint abnormalities, exhibiting either a localized fracture in the incus head or a joint space widening. No differences were observed in collagen fibers structure, bone tissue composition and mechanical properties. These findings suggest that bone fractures observed in the oim incus may contribute to their reported hearing loss. However, the underlying mechanism for these fracture development remains to be investigated, as they do not appear to result from changes in bone tissue properties (collagen fibers organization, tissue composition or mechanical properties). Instead, they may be associated with joint space widening, and possibly altered ossicle chain kinematics.

Exploring a Nitric Oxide-Releasing Celecoxib Derivative as a Potential Modulator of Bone Healing: Insights from Ex Vivo and In Vivo Imaging Experiments

The inducible enzyme cyclooxygenase-2 (COX-2) and the subsequent synthesis of eicosanoids initiated by this enzyme are important molecular players in bone healing. In this pilot study, the suitability of a novel selective COX-2 inhibitor bearing a nitric oxide (NO)-releasing moiety was investigated as a modulator of healing a critical-size bone defect in rats. A 5 mm femoral defect was randomly filled with no material (negative control, NC), a mixture of collagen and autologous bone fragments (positive control, PC), or polycaprolactone-co-lactide (PCL)-scaffolds coated with two types of artificial extracellular matrix (aECM; collagen/chondroitin sulfate (Col/CS) or collagen/polysulfated hyaluronic acid (Col/sHA3)). Bone healing was monitored by a dual-tracer ([18F]FDG/[18F]fluoride) approach using PET/CT imaging in vivo. In addition, ex vivo µCT imaging as well as histological and immunohistochemical studies were performed 16 weeks post-surgery. A significant higher uptake of [18F]FDG, a surrogate marker for inflammatory infiltrate, but not of [18F]fluoride, representing bone mineralization, was observed in the implanted PCL-scaffolds coated with either Col/CS or Col/sHA3. Molecular targeting of COX-2 with NO-coxib had no significant effect on tracer uptake in any of the groups. Histological and immunohistochemical staining showed no evidence of a positive or negative influence of NO-coxib treatment on bone healing.

Management of a carcinoma in situ of the tongue margin, using a Nd:YAG laser, cross-linked hyaluronic acid (xHyA) gel and a porcine pericardium resorbable membrane: a case report

BACKGROUND

Oral tongue squamous cell carcinoma is the most prevalent cancer of the oral cavity. To date, the mainstay management for carcinoma in situ of the oral cavity is the surgical radical removal of the neoplastic tis-sue. This paper describes a new approach in the management of an in situ carcinoma of the tongue margin, treated surgically by the use of Nd:YAG laser, the application of cross-liked hyaluronic acid (xHyA) gel and the placement of a resorbable porcine pericardium membrane (PPM).

CASE PRESENTATION

The case involves a 49-years old male patient with no history of smoking and alcohol use, who presented a non-homogeneous leukoplakia of the right tongue border. The biopsy revealed high-grade lichenoid dysplasia, corresponding to severe epithelial dysplasia or carcinoma in situ (Tis), characterized by full-thickness dysplasia without stromal invasion.

CONCLUSIONS

The case shows that the combined use of Neodimium laser surgery, xHyA gel and PPM is a viable option for promoting soft tissue regeneration in the oral cavity, enabling excellent clinical results in terms of healing medium-sized surgical defects. In addition, compared with other options for the reconstruction of surgical defects of the tongue, the clinical use of the association between these two materials has several biological advantages due to the absence of donor sites and high patient tolerability.

The inducing effect of epidermal growth factor on acellular dermal matrix in a rat model of skin regeneration

OBJECTIVE

Tissue engineering, a novel approach in dermatology, has resulted in the development of scaffolds as skin substitutes that have accelerated wound healing. The aim of the present study was to synthesise acellular dermal matrix (ADM) as a dermal alternative and assess the effect of human epidermal growth factor (EGF) on the proliferation and migration of seeded fibroblast cells.

METHOD

ADM from fresh, full-thickness human skin was developed and characterised. Next, foreskin fibroblast cells were isolated, cultured and characterised. The fibroblast cells were sown into the ADM in two groups: one with EGF and one without EGF. We assessed the adhesion and proliferation of the cells on the scaffold by scanning electron microscopy, and thiazolyl blue tetrazolium bromide and 4',6-diamidino-2-phenylindole staining. For the animal study, 30 rats were divided into two equal groups at random (ADM, ADM+EGF). Wound healing was assessed macroscopically, histologically and by real-time polymerase chain reaction for Bax and Bcl-2 gene expression.

RESULTS

The ADM characterisation results showed that the scaffold was dense and integral with good stretching. The morphology and phenotype of the isolated fibroblast cells confirmed their identity. The fibroblast cells cultured on the ADM showed proliferation, which improved with the addition of EGF. In the animal model, EGF addition caused significantly (p<0.05) improved wound healing compared with isolated ADM; it also resulted in increased Bcl-2 and reduced Bax expressions.

CONCLUSION

A combination of ADM, fibroblast cells and EGFs could serve as skin substitutes and represent a novel therapeutic methodology for treating burns and hard-to-heal wounds.

Biomaterial Cues for Regulation of Osteoclast Differentiation and Function in Bone Regeneration

Tissue regeneration involves dynamic dialogue between and among different cells and their surrounding matrices. Bone regeneration is specifically governed by reciprocity between osteoblasts and osteoclasts within the bone microenvironment. Osteoclast-directed resorption and osteoblast-directed formation of bone are essential to bone remodeling, and the crosstalk between these cells is vital to curating a sequence of events that culminate in the creation of bone tissue. Among bone biomaterial strategies, many have investigated the use of different material cues to direct the development and activity of osteoblasts. However, less attention has been given to exploring features that similarly target osteoclast formation and activity, with even fewer strategies demonstrating or integrating biomaterial-directed modulation of osteoblast-osteoclast coupling. This review aims to describe various biomaterial cues demonstrated to influence osteoclastogenesis and osteoclast function, emphasizing those that enhance a material construct's ability to achieve bone healing and regeneration. Additionally discussed are approaches that influence the communication between osteoclasts and osteoblasts, particularly in a manner that takes advantage of their coupling. Deepening our understanding of how biomaterial cues may dictate osteoclast differentiation, function, and influence on the microenvironment may enable the realization of bone-replacement interventions with enhanced integrative and regenerative capacities.

Protective effects of a novel FS-Collagen hydrolysates against UV- and d-galactose-induced skin aging

The oral consumption of collagen hydrolysates derived from various animal tissues has been demonstrated to have beneficial effects on skin health, particularly in combating the signs of aging. Here in this study, a novel animal-derived FS-Collagen hydrolysates were developed and its effects against skin aging was analyzed in a new mice skin aging model established through a combination of UV irradiation and d-galactose induction. 8 Weeks of oral FS-Collagen administration demonstrated significant protective effects against skin aging in mice, evidenced by the preservation of the skin's macroscopic appearance, the restoration of skin composition and structure, an enhancement in antioxidant capacity and the inhibition of inflammation. Additionally, FS-Collagen safeguards skin barrier integrity and cellular connections, particularly by maintaining the expression levels of Dsg1 and Jam-A. In summary, the FS-Collagen exhibits positive effects in countering skin aging and holds promise as an alternative functional nutrition supplement for anti-skin aging care.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10068-024-01660-7.

Fabrication of Bioactive Helix aspersa Extract-Loaded Chitosan-Based Bilayer Wound Dressings for Skin Tissue Regeneration

In recent years, there has been a notable shift toward exploring plant and animal extracts for the fabrication of tissue engineering structures that seamlessly integrate with the human body, providing both biological compatibility and physical reinforcement. In this particular investigation, we synthesized bilayer wound dressings by incorporating snail (Helix aspersa) secretions, comprising mucus and slime, into chitosan matrices via lyophilization and electrospinning methodologies. A nanofiber layer was integrated on top of the porous structure to mimic the epidermal layer for keratinocyte activity as well as acting as an antibacterial barrier against possible infection, whereas a porous structure was designed to mimic the dermal microenvironment for fibroblast activity. Comprehensive assessments encompassing physical characterization, antimicrobial efficacy, in vitro bioactivity, and wound healing potential were conducted on these bilayer dressings. Our findings revealed that the mucus and slime extract loading significantly altered the morphology in terms of nanofiber diameter and average pore size. Snail extracts loaded on a nanofiber layer of bilayer dressings showed slight antimicrobial activity against Staphylococcus epidermidis and Escherichia coli. An in vitro release study of slime extract loaded in the nanofiber layer indicated that both groups 1 and 2 showed a burst release up to 6 h, and a sustained release was observed up to 96 h for group 1, whereas slime extract release from group 2 continued up to 72 h. In vitro bioactivity assays unveiled the favorable impact of mucus and slime extracts on NIH/3T3 fibroblast and HS2 keratinocyte cell attachment, proliferation, and glycosaminoglycan synthesis. Furthermore, our investigations utilizing the in vitro scratch assay showcased the proliferative and migratory effects of mucus and slime extracts on skin cells. Collectively, our results underscore the promising prospects of bioactive snail secretion-loaded chitosan constructs for facilitating skin regeneration and advancing wound healing therapies.

Characterization of gut microbiota in the Uyghur osteopenia population

The objectives of this study were to investigate the composition of gut microbiota and its relationship with bone loss in the Uyghur osteopenia population, identify potential disease-related taxa and collect information for the prevention and treatment of osteopenia in different people by regulating gut microbiota. We selected Uyghur residents, measured their heel BMD, collected faeces and general information, grouped them by BMD level, obtained faecal 16S rRNA sequences, and compared and analysed the differences between the groups. This study showed that the numbers of OTUs and species in the gut microbiota in the osteopenia group were higher than those in the control. At the phylum level, Erysipelotrichia was more abundant in the osteopenia group. At the genus level, Phascolarctobacterium was less abundant, and Ruminiclostridium_5 was more abundant in the osteopenia group compared to the control. Phascolarctobacterium and Z-score were positively correlated, and Ruminiclostridium_5 was negatively correlated with T and Z score. The different composition of the gut microbiota in Uyghur osteopenia patients and controls found in this study fills a knowledge gap in this ethnic group. The relationship between Uyghur osteopenia and BMD-associated bacterial genera deserves further exploration.

Collagen molecular organization preservation in human fascia lata and periosteum after tissue engineering

Large bone defect regeneration remains a major challenge for orthopedic surgeons. Tissue engineering approaches are therefore emerging in order to overcome this limitation. However, these processes can alter some of essential native tissue properties such as intermolecular crosslinks of collagen triple helices, which are known for their essential role in tissue structure and function. We assessed the persistence of extracellular matrix (ECM) properties in human fascia lata (HFL) and periosteum (HP) after tissue engineering processes such as decellularization and sterilization. Harvested from cadaveric donors (N = 3), samples from each HFL and HP were decellularized following five different chemical protocols with and without detergents (D1-D4 and D5, respectively). D1 to D4 consisted of different combinations of Triton, Sodium dodecyl sulfate and Deoxyribonuclease, while D5 is routinely used in the institutional tissue bank. Decellularized HFL tissues were further gamma-irradiated (minimum 25 kGy) in order to study the impact of sterilization on the ECM. Polarized light microscopy (PLM) was used to estimate the thickness and density of collagen fibers. Tissue hydration and content of hydroxyproline, enzymatic crosslinks, and non-enzymatic crosslinks (pentosidine) were semi-quantified with Raman spectroscopy. ELISA was also used to analyze the maintenance of the decorin (DCN), an important small leucine rich proteoglycan for fibrillogenesis. Among the decellularization protocols, detergent-free treatments tended to further disorganize HFL samples, as more thin fibers (+53.7%) and less thick ones (-32.6%) were recorded, as well as less collagen enzymatic crosslinks (-25.2%, p = 0.19) and a significant decrease of DCN (p = 0.036). GAG content was significantly reduced in both tissue types after all decellularization protocols. On the other hand, HP samples were more sensitive to the D1 detergent-based treatments, with more disrupted collagen organization and greater, though not significant loss of enzymatic crosslinks (-37.4%, p = 0.137). Irradiation of D5 HFL samples, led to a further and significant loss in the content of enzymatic crosslinks (-29.4%, p = 0.037) than what was observed with the decellularization process. Overall, the results suggest that the decellularization processes did not significantly alter the matrix. However, the addition of a gamma-irradiation is deleterious to the collagen structural integrity of the tissue.

Benchmarking Water Models in Molecular Dynamics of Protein-Glycosaminoglycan Complexes

Glycosaminoglycans (GAGs) made of repeating disaccharide units intricately engage with proteins, playing a crucial role in the spatial organization of the extracellular matrix (ECM) and the transduction of biological signals in cells to modulate a number of biochemical processes. Exploring protein-GAG interactions reveals several challenges for their analysis, namely, the highly charged and periodic nature of GAGs, their multipose binding, and the abundance of the interfacial water molecules in the protein-GAG complexes. Most of the studies on protein-GAG interactions are conducted using the TIP3P water model, and there are no data on the effect of various water models on the results obtained in molecular dynamics (MD) simulations of protein-GAG complexes. Hence, it is essential to perform a systematic analysis of different water models in MD simulations for these systems. In this work, we aim to evaluate the properties of the protein-GAG complexes in MD simulations using different explicit: TIP3P, SPC/E, TIP4P, TIP4PEw, OPC, and TIP5P and implicit: IGB = 1, 2, 5, 7, and 8 water models to find out which of them are best suited to study the dynamics of protein-GAG complexes. The FF14SB and GLYCAM06 force fields were used for the proteins and GAGs, respectively. The interactions of several GAG types, such as heparin, chondroitin sulfate, and hyaluronic acid with basic fibroblast growth factor, cathepsin K, and CD44 receptor, respectively, are investigated. The observed variations in different descriptors used to study the binding in these complexes emphasize the relevance of the choice of water models for the MD simulation of these complexes.

Control of tissue homeostasis by the extracellular matrix: Synthetic heparan sulfate as a promising therapeutic for periodontal health and bone regeneration

Proteoglycans are core proteins associated with carbohydrate/sugar moieties that are highly variable in disaccharide composition, which dictates their function. These carbohydrates are named glycosaminoglycans, and they can be attached to proteoglycans or found free in tissues or on cell surfaces. Glycosaminoglycans such as hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin/heparan sulfate have multiple functions including involvement in inflammation, immunity and connective tissue structure, and integrity. Heparan sulfate is a highly sulfated polysaccharide that is abundant in the periodontium including alveolar bone. Recent evidence supports the contention that heparan sulfate is an important player in modulating interactions between damage associated molecular patterns and inflammatory receptors expressed by various cell types. The structure of heparan sulfate is reported to dictate its function, thus, the utilization of a homogenous and structurally defined heparan sulfate polysaccharide for modulation of cell function offers therapeutic potential. Recently, a chemoenzymatic approach was developed to allow production of many structurally defined heparan sulfate carbohydrates. These oligosaccharides have been studied in various pathological inflammatory conditions to better understand their function and their potential application in promoting tissue homeostasis. We have observed that specific size and sulfation patterns can modulate inflammation and promote tissue maintenance including an anabolic effect in alveolar bone. Thus, new evidence provides a strong impetus to explore heparan sulfate as a potential novel therapeutic agent to treat periodontitis, support alveolar bone maintenance, and promote bone formation.

Studying specificity in protein-glycosaminoglycan recognition with umbrella sampling

In the past few decades, glycosaminoglycan (GAG) research has been crucial for gaining insights into various physiological, pathological, and therapeutic aspects mediated by the direct interactions between the GAG molecules and diverse proteins. The structural and functional heterogeneities of GAGs as well as their ability to bind specific proteins are determined by the sugar composition of the GAG, the size of the GAG chains, and the degree and pattern of sulfation. A deep understanding of the interactions in protein-GAG complexes is essential to explain their biological functions. In this study, the umbrella sampling (US) approach is used to pull away a GAG ligand from the binding site and then pull it back in. We analyze the binding interactions between GAGs of three types (heparin, desulfated heparan sulfate, and chondroitin sulfate) with three different proteins (basic fibroblast growth factor, acidic fibroblast growth factor, and cathepsin K). The main focus of our study was to evaluate whether the US approach is able to reproduce experimentally obtained structures, and how useful it can be for getting a deeper understanding of GAG properties, especially protein recognition specificity and multipose binding. We found that the binding free energy landscape in the proximity of the GAG native binding pose is complex and implies the co-existence of several binding poses. The sliding of a GAG chain along a protein surface could be a potential mechanism of GAG particular sequence recognition by proteins.

Xioglican Cream in Italian Patients with Chronic Venous Disease: A Post-Marketing Study Investigating Effects on Clinical and Cutaneous Signs and Symptoms

INTRODUCTION

The progression of chronic venous disease (CVD) is characterized by edema of the legs and/or venous ulcers of the lower limbs in association with cutaneous signs and/or skin alterations, such as hyperpigmentation, corona phlebectatica, telangiectasia, eczematous dermatitis, lipodermatosclerosis, atrophie blanche, cellulitis, and induration. Xioglican cream is a galactosaminoglycan polysulfate and hyaluronic acid-containing medical device with strong hydrophilic, moisturizing, and soothing properties. This post-marketing observational study evaluated topical Xioglican cream in the amelioration of skin manifestations and clinical signs and symptoms in patients with CVD treated in routine clinical practice.

METHODS

Adult patients (18-75 years) with a clinical diagnosis of C2-C3 CVD according to Clinical, Etiology, Anatomy, and Pathophysiology (CEAP) classification who received 12 weeks of treatment with Xioglican (applied up to 3 times daily), according to investigator decision (and consistent with conventional clinical practice and established standard of care), were enrolled from two study sites in Italy. A range of endpoints were used to evaluate efficacy, safety, effect on patient quality of life (QoL), and patient satisfaction with topical application of Xioglican cream in the physiological restoration of skin signs and symptoms.

RESULTS

In patients with CVD (n = 30), Xioglican cream reduced CVD-related skin manifestations and associated symptoms, with significant reductions in leg circumference [mean ± standard deviation (SD): - 3.21 ± 3.39 cm for left and - 2.92 ± 2.70 cm for right legs, both p < 0.0001] and local edema (- 5.52 ± 7.94 cm, p = 0.0034) and significant improvement in Venous Clinical Severity Scores (mean 0.52 ± 1.94 decrease from baseline, p = 0.1952) observed after 12 weeks. Skin burning, pain, aching or tiredness, and QoL were also significantly improved. There was no change in CEAP classification. Globally, 92.0% of patients were "Very satisfied" or "Satisfied" with the product.

CONCLUSIONS

Topical treatment with Xioglican cream improves the signs, symptoms, and QoL of patients with CVD class C2-C3.

S-Protected Thiolated Chitosan versus Thiolated Chitosan as Cell Adhesive Biomaterials for Tissue Engineering

Chitosan (Ch) and different Ch derivatives have been applied in tissue engineering (TE) because of their biocompatibility, favored mechanical properties, and cost-effectiveness. Most of them, however, lack cell adhesive properties that are crucial for TE. In this study, we aimed to design an S-protected thiolated Ch derivative exhibiting high cell adhesive properties serving as a scaffold for TE. 3-((2-Acetamido-3-methoxy-3-oxopropyl)dithio) propanoic acid was covalently attached to Ch via a carbodiimide-mediated reaction. Low-, medium-, and high-modified Chs (Ch-SS-1, Ch-SS-2, and Ch-SS-3) with 54, 107 and 140 μmol of ligand per gram of polymer, respectively, were tested. In parallel, three thiolated Chs, namely Ch-SH-1, Ch-SH-2, and Ch-SH-3, were prepared by conjugating N-acetyl cysteine to Ch at the same degree of modification to compare the effectiveness of disulfide versus thiol modification on cell adhesion. Ch-SS-1 showed better cell adhesion capability than Ch-SS-2 and Ch-SS-3. This can be explained by the more lipophilic surfaces of Ch-SS as a higher modification was made. Although Ch-SH-1, Ch-SH-2, and Ch-SH-3 were shown to be good substrates for cell adhesion, growth, and proliferation, Ch-SS polymers were superior to Ch-SH polymers in the formation of 3D cell cultures. Cryogels structured by Ch-SS-1 (SSg) resulted in homogeneous scaffolds with tunable pore size and mechanical properties by changing the mass ratio between Ch-SS-1 and heparin used as a cross-linker. SSg scaffolds possessing interconnected microporous structures showed good cell migration, adhesion, and proliferation. Therefore, Ch-SS can be used to construct tunable cryogel scaffolds that are suitable for 3D cell culture and TE.

A seminal perspective on the role of chondroitin sulfate in biomineralization

Chondroitin sulfate (CS) is an important extracellular matrix component of mineralized tissues. It participates in biomineralization, osteoblast differentiation and promotes bone tissue repair in vitro. However, the mechanism in which CS functions is unclear. Accordingly, an in-depth investigation of how CS participates in mineralization was conducted in the present study. Chondroitin sulfate was found to directly induce intrafibrillar mineralization of the collagen matrix. The mineralization outcome was dependent on whether CS remained free in the extracellular matrix or bound to core proteins; mineralization only occurred when CS existed in a free state. The efficacy of mineralization appeared to increase with ascending CS concentration. This discovery spurred the authors to identify the cause of heterotopic ossification in the Achilles tendon. Chondroitin sulfate appeared to be a therapeutic target for the management of diseases associated with heterotopic calcification. A broader perspective was presented on the applications of CS in tissue engineering.

Development of Cissus quadrangularis-Loaded POSS-Reinforced Chitosan-Based Bilayer Sponges for Wound Healing Applications: Drug Release and In Vitro Bioactivity

Nowadays, antibiotic-loaded biomaterials have been widely used in wound healing applications. However, the use of natural extracts has come into prominence as an alternative to these antimicrobial agents in the recent period. Among natural sources, Cissus quadrangularis (CQ) herbal extract is used for treatment of bone and skin diseases in ayurvedic medicine due to its antibacterial and anti-inflammatory effects. In this study, chitosan-based bilayer wound dressings were fabricated with electrospinning and freeze-drying techniques. CQ extract-loaded chitosan nanofibers were coated on chitosan/POSS nanocomposite sponges using an electrospinning method. The bilayer sponge is designed to treat exudate wounds while mimicking the layered structure of skin tissue. Bilayer wound dressings were investigated with regard to the morphology and physical and mechanical properties. In addition, CQ release from bilayer wound dressings and in vitro bioactivity studies were performed to determine the effect of POSS nanoparticles and CQ extract loading on NIH/3T3 and HS2 cells. The morphology of nanofibers was investigated with SEM analysis. Physical characteristics of bilayer wound dressings were determined with FT-IR analysis, swelling study, open porosity determination, and mechanical test. The antimicrobial activity of CQ extract released from bilayer sponges was investigated with a disc diffusion method. Bilayer wound dressings' in vitro bioactivity was examined using cytotoxicity determination, wound healing assay, proliferation, and the secretion of biomarkers for skin tissue regeneration. The nanofiber layer diameter was obtained in the range of 77.9-97.4 nm. The water vapor permeability of the bilayer dressing was obtained as 4021 to 4609 g/m2day, as it is in the ideal range for wound repair. The release of the CQ extract over 4 days reached 78-80% cumulative release. The release media were found to be antibacterial against Gram-negative and Gram-positive bacteria. In vitro studies showed that both CQ extract and POSS incorporation induced cell proliferation as well as wound healing activity and collagen deposition. As a result, CQ-loaded bilayer CHI-POSS nanocomposites were found as a potential candidate for wound healing applications.

Solvent Model Benchmark for Molecular Dynamics of Glycosaminoglycans

In computational studies of glycosaminoglycans (GAGs), a group of anionic, periodic linear polysaccharides, so far there has been very little discussion about the role of solvent models in the molecular dynamics simulations of these molecules. Predominantly, the TIP3P water model is commonly used as one of the most popular explicit water models in general. However, there are numerous alternative explicit and implicit water models that are neglected in the computational research of GAGs. Since solvent-mediated interactions are particularly important for GAG dynamic and structural properties, it would be of great interest for the GAG community to establish the solvent model that is suited the best in terms of the quality of theoretically obtained GAG parameters and, at the same time, would be reasonably demanding in terms of computational resources required. In this study, heparin (HP) was simulated using five implicit and six explicit solvent models with the aim to find out how different solvent models influence HP's molecular descriptors in the molecular dynamics simulations. Here, we initiate the search for the most appropriate solvent representation for GAG systems and we hope to encourage other groups to contribute to this highly relevant subject.

Repulsive Scaling Replica Exchange Molecular Dynamics in Modeling Protein-Glycosaminoglycan Complexes

Glycosaminoglycans are long linear periodic anionic polysaccharides consisting of disaccharide units exhibiting different sulfation patterns forming a highly heterogeneous group of molecules. Due to their flexibility, length, high charge, and periodicity, they are challenging for computational approaches. Despite their biological significance in terms of the important role in various diseases (e.g., Alzheimer, cancer, SARS-CoV-2) and proper cell functioning (e.g., proliferation, maturation), there is a lack of effective molecular docking tools designed specifically for glycosaminoglycans due to their challenging physical-chemical nature. In this chapter we present protocols for the Repulsive Scaling Replica Exchange Molecular Dynamics (RS-REMD) methods to dock glycosaminoglycans with both implicit and explicit solvent models implemented. This novel molecular dynamics-based replica exchange technique should help to elevate our current knowledge on the complexes and interactions between glycosaminoglycans and their protein receptors.

Controlled release of growth factors using synthetic glycosaminoglycans in a modular macroporous scaffold for tissue regeneration

Healthy regeneration of tissue relies on a well-orchestrated release of growth factors. Herein, we show the use of synthetic glycosaminoglycans for controlled binding and release of growth factors to induce a desired cellular response. First, we screened glycosaminoglycans with growth factors of interest to determine kon (association rate constant), koff (dissociation rate constant), and Kd (equilibrium rate constant). As proof-of-concept, we functionalized an elastin-like recombinamer (ELR) hydrogel with a synthetic glycosaminoglycan and immobilized fibroblast growth factor 2 (FGF2), demonstrating that human umbilical vein endothelial cells cultured on top of ELR hydrogel differentiated into tube-like structures. Taking this concept further, we developed a tunable macroporous ELR cryogel material, containing a synthetic glycosaminoglycan and FGF2 that showed increased blood vessel formation and reduced immune response compared to control when implanted in a subcutaneous mouse model. These results demonstrated the possibility for specific release of desired growth factors in/from a modular 3D scaffold in vitro and in vivo.

Explicit solvent repulsive scaling replica exchange molecular dynamics (RS-REMD) in molecular modeling of protein-glycosaminoglycan complexes

Glycosaminoglcyans (GAGs), linear anionic periodic polysaccharides, are crucial for many biologically relevant functions in the extracellular matrix. By interacting with proteins GAGs mediate processes such as cancer development, cell proliferation and the onset of neurodegenerative diseases. Despite this eminent importance of GAGs, they still represent a limited focus for the computational community in comparison to other classes of biomolecules. Therefore, there is a lack of modeling tools designed specifically for docking GAGs. One has to rely on existing docking software developed mostly for small drug molecules substantially differing from GAGs in their basic physico-chemical properties. In this study, we present an updated protocol for docking GAGs based on the Repulsive Scaling Replica Exchange Molecular Dynamics (RS-REMD) that includes explicit solvent description. The use of this water model improved docking performance both in terms of its accuracy and speed. This method represents a significant computational progress in GAG-related research.

Effects of the combination of bone morphogenetic protein-2 and nano-hydroxyapatite on the osseointegration of dental implants

OBJECTIVES

This study aimed to investigate the in vitro osteoinductivity of the combination of bone morphogenetic protein-2 (BMP-2) and nanohydroxyapatite (nHAp) and the in vivo effects of implants coated with nHAp/BMP-2.

MATERIALS AND METHODS

To evaluate the in vitro efficacy of nHAp/BMP-2 on bone formation, bone marrow-derived mesenchymal stem cells (BMMSCs) were seeded onto titanium disks coated with collagen (Col), Col/nHAp, or Col/nHAp/BMP-2. Protein levels were determined by a biochemical assay and reverse transcriptase-polymerase chain reaction. Stem cell differentiation was analyzed by flow cytometry. For in vivo studies with mice, Col, Col/nHAp, and Col/nHAp/BMP-2 were injected in subcutaneous pockets. Titanium implants or implants coated with Col/nHAp/BMP-2 were placed bilaterally on rabbit tibias and evaluated for 4 weeks.

RESULTS

In the in vitro study, BM-MSCs on Col/nHAp/BMP-2 showed reduced levels of CD73, CD90, and CD105 and increased levels of glycosaminoglycan, osteopontin, and alkaline phosphatase activity. After 4 weeks, the Col/nHAp/BMP-2 implant showed greater bone formation than the control (P=0.07), while no differences were observed in bone implant contact and removal torque.

CONCLUSION

These results suggest that a combination of BMP-2 and an nHAp carrier would activate osseointegration on dental implant surfaces.

Disease-specific glycosaminoglycan patterns in the extracellular matrix of human lung and brain

A wide variety of diseases throughout the mammalian organism is characterized by abnormal deposition of various components of the extracellular matrix (ECM), including the heterogeneous family of glycosaminoglycans (GAGs), which contribute considerably to the ECM architecture as part of the so-called proteoglycans. The GAG's unique sulfation pattern, derived from highly dynamic and specific modification processes, has a massive impact on critical mediators such as cytokines and growth factors. Due to the strong connection between the specific sulfation pattern and GAG function, slight alterations of this pattern are often associated with enormous changes at the cell as well as at the organ level. This review aims to investigate the connection between modifications of GAG sulfation patterns and the wide range of pathological conditions, mainly focusing on a range of chronic diseases of the central nervous system (CNS) as well as the respiratory tract.

Fructus Ligustri Lucidi aqueous extract promotes calcium balance and short-chain fatty acids production in ovariectomized rats

ETHNOPHARMACOLOGICAL RELEVANCE

Fructus Ligustri Lucidi (FLL) is an edible herb with anti-osteoporotic activity, yet whether and how the aqueous extract of this herb affect calcium metabolism in preservation of bone quality remain unclear.

AIM OF THE STUDY

To investigate the effects of FLL aqueous extract on calcium balance and short-chain fatty acids (SCFAs) production in ovariectomized (OVX) rats.

MATERIALS AND METHODS

OVX rats were daily and orally administrated with FLL aqueous extract (3.5 g/kg) for 14 weeks. The levels of N-terminal propeptide of type I collagen (PINP) and C-terminal telopeptide of type I collagen (CTx-I) in rat serum were evaluated by ELISA assays. The concentration of calcium in serum, urine, and feces were determined by biochemical assays. Bone quality was determined by Micro-CT, a three-point bending assay, and Fourier Transform Infrared (FTIR) Spectrometry. The expressions of Calbindin D28K and Calcium-sensing receptor (CaSR) in kidney as well as the Vitamin D receptor (VDR), the transient receptor potential vanilloid receptor 6 (TRPV6), Calbindin D9k in the duodenum were measured by immunohistochemistry, western blotting, or real-time PCR. The short-chain fatty acids (SCFAs) levels in the feces of the cecum were tested by gas chromatograghy.

RESULTS

The administration of FLL to OVX rats resulted in a significant improvement in bone mineral density and biomechanical strength as well as in maintaining bone microstructures and material quality. Meanwhile, the decreased levels of PINP and increased levels of CTx-I in OVX rats were restored by FLL treatment. Additionally, FLL treatment increased calcium absorption, upregulated VDR, TRPV6, Calbindin D9k expressions in the duodenum, Calbindin D28K in kidney, and down-regulated CaSR expression in the kidney, as well as enhanced SCFAs levels in the feces of OVX rats.

CONCLUSIONS

FLL aqueous extract may preserve bone quality through regulation of the calcium balance and intestinal SCFAs production in OVX rats. This offers translational value of FLL into osteoporosis clinical trial.

Identification of intracellular glycosaminoglycan-interacting proteins by affinity purification mass spectrometry

Glycosaminoglycans (GAGs) are essential functional components of the extracellular matrix (ECM). Artificial GAGs like sulfated hyaluronan (sHA) exhibit pro-osteogenic properties and boost healing processes. Hence, they are of high interest for supporting bone regeneration and wound healing. Although sulfated GAGs (sGAGs) appear intracellularly, the knowledge about intracellular effects and putative interaction partners is scarce. Here we used an affinity-purification mass spectrometry-based (AP-MS) approach to identify novel and particularly intracellular sGAG-interacting proteins in human bone marrow stromal cells (hBMSC). Overall, 477 proteins were found interacting with at least one of four distinct sGAGs. Enrichment analysis for protein localization showed that mainly intracellular and cell-associated interacting proteins were identified. The interaction of sGAG with α2-macroglobulin receptor-associated protein (LRPAP1), exportin-1 (XPO1), and serine protease HTRA1 (HTRA1) was confirmed in reverse assays. Consecutive pathway and cluster analysis led to the identification of biological processes, namely processes involving binding and processing of nucleic acids, LRP1-dependent endocytosis, and exosome formation. Respecting the preferentially intracellular localization of sGAG in vesicle-like structures, also the interaction data indicate sGAG-specific modulation of vesicle-based transport processes. By identifying many sGAG-specific interacting proteins, our data provide a resource for upcoming studies aimed at molecular mechanisms and understanding of sGAG cellular effects.

Polymer-Based Nanotherapeutics for Burn Wounds

Burn wounds are complex and intricate injuries that have become a common cause of trauma leading to significant mortality and morbidity every year. Dressings are applied to burn wounds with the aim of promoting wound healing, preventing burn infection and restoring skin function. The dressing protects the injury and contributes to recovery of dermal and epidermal tissues. Polymer-based nanotherapeutics are increasingly being exploited as burn wound dressings. Natural polymers such as cellulose, chitin, alginate, collagen, gelatin and synthetic polymers like poly (lactic-co-glycolic acid), polycaprolactone, polyethylene glycol, and polyvinyl alcohol are being obtained as nanofibers by nanotechnological approaches like electrospinning and have shown wound healing and re-epithelialization properties. Their biocompatibility, biodegradability, sound mechanical properties and unique structures provide optimal microenvironment for cell proliferation, differentiation, and migration contributing to burn wound healing. The polymeric nanofibers mimic collagen fibers present in extracellular matrix and their high porosity and surface area to volume ratio enable increased interaction and sustained release of therapeutics at the site of thermal injury. This review is an attempt to compile all recent advances in the use of polymer-based nanotherapeutics for burn wounds. The various natural and synthetic polymers used have been discussed comprehensively and approaches being employed have been reported. With immense research effort that is currently being invested in this field and development of proper characterization and regulatory framework, future progress in burn treatment is expected to occur. Moreover, appropriate preclinical and clinical research will provide evidence for the great potential that polymer-based nanotherapeutics hold in the management of burn wounds.

Improvement of wound healing by the development of ECM-inspired biomaterial coatings and controlled protein release

Implant design has evolved from biochemically inert substrates, minimizing cell and protein interaction, towards sophisticated bioactive substrates, modulating the host response and supporting the regeneration of the injured tissue. Important aspects to consider are the control of cell adhesion, the discrimination of bacteria and non-local cells from the desired tissue cell type, and the stimulation of implant integration and wound healing. Here, the extracellular matrix acts as a role model providing us with inspiration for sophisticated designs. Within this scope, small bioactive peptides have proven to be miscellaneously deployable for the mediation of surface, cell and matrix interactions. Combinations of adhesion ligands, proteoglycans, and modulatory proteins should guide multiple aspects of the regeneration process and cooperativity between the different extracellular matrix components, which bears the chance to maximize the therapeutic efficiency and simultaneously lower the doses. Hence, efforts to include multiple of these factors in biomaterial design are well worth. In the following, multifunctional implant coatings based on bioactive peptides are reviewed and concepts to implement strong surface anchoring for stable cell adhesion and a dynamic delivery of modulator proteins are discussed.

New insights into the role of glycosaminoglycans in the endosteal bone microenvironment

The bone microenvironment is a complex tissue in which heterogeneous cell populations of hematopoietic and mesenchymal origin interact with environmental cues to maintain tissue integrity. Both cellular and matrix components are subject to physiologic challenges and can dynamically respond by modifying cell/matrix interactions. When either component is impaired, the physiologic balance is lost. Here, we review the current state of knowledge of how glycosaminoglycans - organic components of the bone extracellular matrix - influence the bone micromilieu. We point out how they interact with mediators of distinct signaling pathways such as the RANKL/OPG axis, BMP and WNT signaling, and affect the activity of bone remodeling cells within the endosteal niche summarizing their potential for therapeutic intervention.

Collagen/glycosaminoglycan-based matrices for controlling skin cell responses

Wound healing and tissue regeneration are orchestrated by the cellular microenvironment, e.g. the extracellular matrix (ECM). Including ECM components in biomaterials is a promising approach for improving regenerative processes, e.g. wound healing in skin. This review addresses recent findings for enhanced epidermal-dermal regenerative processes on collagen (coll)/glycosaminoglycan (GAG)-based matrices containing sulfated GAG (sGAG) in simple and complex in vitro models. These matrices comprise 2D-coatings, electrospun nanofibrous scaffolds, and photo-crosslinked acrylated hyaluronan (HA-AC)/coll-based hydrogels. They demonstrated to regulate keratinocyte and fibroblast migration and growth, to stimulate melanogenesis in melanocytes from the outer root sheath (ORS) of hair follicles and to enhance the epithelial differentiation of human mesenchymal stem cells (hMSC). The matrices' suitability for delivery of relevant growth factors, like heparin-binding epidermal growth factor like growth factor (HB-EGF), further highlights their potential as bioinspired, functional microenvironments for enhancing skin regeneration.

Impact of binding mode of low-sulfated hyaluronan to 3D collagen matrices on its osteoinductive effect for human bone marrow stromal cells

Synthetically sulfated hyaluronan derivatives were shown to facilitate osteogenic differentiation of human bone marrow stromal cells (hBMSC) by application in solution or incorporated in thin collagen-based coatings. In the presented study, using a biomimetic three-dimensional (3D) cell culture model based on fibrillary collagen I (3D Col matrix), we asked on the impact of binding mode of low sulfated hyaluronan (sHA) in terms of adsorptive and covalent binding on osteogenic differentiation of hBMSC. Both binding modes of sHA induced osteogenic differentiation. Although for adsorptive binding of sHA a strong intracellular uptake of sHA was observed, implicating an intracellular mode of action, covalent binding of sHA to the 3D matrix induced also intense osteoinductive effects pointing towards an extracellular mode of action of sHA in osteogenic differentiation. In summary, the results emphasize the relevance of fibrillary 3D Col matrices as a model to study hBMSC differentiation in vitro in a physiological-like environment and that sHA can display dose-dependent osteoinductive effects in dependence on presentation mode in cell culture scaffolds.

Biochemical Modification of Titanium Oral Implants: Evidence from In Vivo Studies

The discovery of osseointegration of titanium implants revolutionized the dental prosthesis field. Traditionally, implants have a surface that is processed by additive or subtractive techniques, which have positive effects on the osseointegration process by altering the topography. In the last decade, innovative implant surfaces have been developed, on which biologically active molecules have been immobilized with the aim of increasing stimulation at the implant-biological tissue interface, thus favoring the quality of osseointegration. Among these molecules, some are normally present in the human body, and the techniques for the immobilization of these molecules on the implant surface have been called Biochemical Modification of Titanium Surfaces (BMTiS). Different techniques have been described in order to immobilize those biomolecules on titanium implant surfaces. The aim of the present paper is to present evidence, available from in vivo studies, about the effects of biochemical modification of titanium oral implants on osseointegration.

High sensitivity analysis of nanogram quantities of glycosaminoglycans using ToF-SIMS

Glycosaminoglycans (GAGs) are important biopolymers that differ in the sequence of saccharide units and in post polymerisation alterations at various positions, making these complex molecules challenging to analyse. Here we describe an approach that enables small quantities (<200 ng) of over 400 different GAGs to be analysed within a short time frame (3-4 h). Time of flight secondary ion mass spectrometry (ToF-SIMS) together with multivariate analysis is used to analyse the entire set of GAG samples. Resultant spectra are derived from the whole molecules and do not require pre-digestion. All 6 possible GAG types are successfully discriminated, both alone and in the presence of fibronectin. We also distinguish between pharmaceutical grade heparin, derived from different animal species and from different suppliers, to a sensitivity as low as 0.001 wt%. This approach is likely to be highly beneficial in the quality control of GAGs produced for therapeutic applications and for characterising GAGs within biomaterials or from in vitro cell culture.

High-Throughput Absolute Quantification Sequencing Revealed Osteoporosis-Related Gut Microbiota Alterations in Han Chinese Elderly

Objective

Accumulative evidence suggests that gut microbiota play an important role in bone remodeling and hence bone health maintenance. This study aimed to explore the association of gut microbiota with the risk of osteoporosis and to identify potential disease-related taxa, which may be promising targets in osteoporosis prevention and treatment in the future.

Methods

Absolute quantification 16S ribosomal RNA gene sequencing was used to detect absolute and relative abundances of gut microbiota in 44 patients with osteoporosis and 64 controls. In combination with one of our previous studies, a total of 175 samples were involved in the relative abundance analysis.

Results

Compared with the controls, the patients with osteoporosis had higher absolute and relative abundances of Bacteroidetes phylum, and Bacteroides and Eisenbergiella genera. The absolute abundances of Clostridium_XlVa, Coprococcus, Lactobacillus, and Eggerthella genera increased, and that of the Veillonella genus decreased in the osteoporosis group. As for relative abundance, that of the Parabacteroides and Flavonifractor genera increased, whereas that of the Raoultella genus decreased in the osteoporosis group. Controlling for potential confounders, the associations of Clostridium_XlVa, Coprococcus, and Veillonella genera with the risk of osteoporosis did not maintain significance. Ridge regression analysis suggested that Bacteroides is associated with reduced bone mineral density (BMD) and T-score at lumbar spines, and Anaerovorax is associated with increased BMD at the femoral neck. Functional predictions revealed that 10 Kyoto Encyclopedia of Genes and Genomes pathways were enriched in the osteoporosis group.

Conclusions

Gut microbiota compositions may contribute to the risk of osteoporosis. Several specific taxa and functional pathways are identified to associate with reduced bone density, thus providing epidemiologic evidence for the potential role of aberrant gut microbiota in osteoporosis pathogenesis.

Hyaluronan Synthases' Expression and Activity Are Induced by Fluid Shear Stress in Bone Marrow-Derived Mesenchymal Stem Cells

During biomineralization, the cells generating the biominerals must be able to sense the external physical stimuli exerted by the growing mineralized tissue and change their intracellular protein composition according to these stimuli. In molluscan shell, the myosin-chitin synthases have been suggested to be the link for this communication between cells and the biomaterial. Hyaluronan synthases (HAS) belong to the same enzyme family as chitin synthases. Their product hyaluronan (HA) occurs in the bone and is supposed to have a regulatory function during bone regeneration. We hypothesize that HASes’ expression and activity are controlled by fluid-induced mechanotransduction as it is known for molluscan chitin synthases. In this study, bone marrow-derived human mesenchymal stem cells (hMSCs) were exposed to fluid shear stress of 10 Pa. The RNA transcriptome was analyzed by RNA sequencing (RNAseq). HA concentrations in the supernatants were measured by ELISA. The cellular structure of hMSCs and HAS2-overexpressing hMSCs was investigated after treatment with shear stress using confocal microscopy. Fluid shear stress upregulated the expression of genes that encode proteins belonging to the HA biosynthesis and bone mineralization pathways. The HAS activity appeared to be induced. Knowledge about the regulation mechanism governing HAS expression, trafficking, enzymatic activation and quality of the HA product in hMSCs is essential to understand the biological role of HA in the bone microenvironment.

Glycosaminoglycan-Protein Interactions and Their Roles in Human Disease

Glycosaminoglycans (GAGs) are a family of linear and negatively charged polysaccharides that exist ubiquitously on the human cell surface as well as in the extracellular matrix. GAGs interact with a wide range of proteins, including proteases, growth factors, cytokines, chemokines and adhesion molecules, enabling them to mediate many physiological processes, such as protein function, cellular adhesion and signaling. GAG-protein interactions participate in and intervene in a variety of human diseases, including cardiovascular disease, infectious disease, neurodegenerative diseases and tumors. The breakthrough in analytical tools and approaches during the last two decades has facilitated a greater understanding of the importance of GAG-protein interactions and their roles in human diseases. This review focuses on aspects of the molecular basis and mechanisms of GAG-protein interactions involved in human disease. The most recent advances in analytical tools, especially mass spectrometry-based GAG sequencing and binding motif characterization methods, are introduced. An update of selected families of GAG binding proteins is presented. Perspectives on development of novel therapeutics targeting specific GAG-protein interactions are also covered in this review.

Injectable chitosan-quince seed gum hydrogels encapsulated with curcumin loaded-halloysite nanotubes designed for tissue engineering application

The goal of tissue engineering is to assemble functional constructs that restore, maintain, or improve damaged tissues or organs. Hydrogels formed with natural polymers display high potential in artificial scaffolds for tissue repair as they can resemble the extracellular matrices. Thus, the aim of this study was to design nanocomposite hydrogels of chitosan/oxidized-modified quince seed gum/curcumin-loaded in halloysite nanotubes (CS/OX-QSG/CUR-HNTs) for tissue engineering applications. The produced hydrogels were analyzed for thermal stability, degradation, swelling ratio, gelling time and mechanical properties. The results showed that with increasing content of OX-QSG, thermal stability, swelling ratio, and degradation rate of hydrogels were improved. Notably, the optimal CS/OX-QSG hydrogel with ratio of 25:75 exhibited rapid gelation behavior (<50 s) and improved compressive strength (3.96 ± 0.64 MPa), representing the suitable hydrogel for application in tissue engineering. The MTT test showed that these hydrogels were non-toxic and any reduction or stop of NIH-3 T3 cells growth wasn't observed over time. In addition, CS/OX-QSG 25:75 hydrogels containing CUR-HNTs with 10 and 30% content was significantly (P < 0.05) enhanced cell growth and proliferation (around 150%). Obtained results illustrated that CS/OX-QSG hydrogels with ratio of 25:75 and the content of 30% CUR-HNTs can be an effective scaffold for application in tissue engineering.

Functions of, and replenishment strategies for, chondroitin sulfate in the human body

Chondroitin sulfate (CS) belongs to a class of molecules called glycosaminoglycans (GAGs). These are long, linear chains of polysaccharides comprising alternating amino sugars and hexuronic acid. Similar to other GAGs, CS is important in a multitude of biological activities. Alteration of CS levels has been implicated in several pathological conditions, including osteoarthritis (OA) and other inflammatory diseases, as well as physiological conditions, such as aging. Therefore, devising replenishment strategies for this molecule is an important area of research. In this review, we discuss the nature of CS, its function in different organs, and its implications in health and disease. We also describe different methods for the exogenous administration of CS.

Topical Application of Peptide-Chondroitin Sulfate Nanoparticles Allows Efficient Photoprotection in Skin

In this article, we describe a method of delivery of chondroitin sulfate to skin as nanoparticles and demonstrate its anti-inflammatory and antioxidant role using UV irradiation as a model condition. These nanoparticles, formed through electrostatic interactions of chondroitin sulfate with a skin-penetrating peptide, were found to be homogenous with positive surface charges and stable at physiological and acidic pH under certain conditions. They were able to enter into the human keratinocyte cell line (HaCaT), artificial skin membrane (mimicking the human skin), and mouse skin tissue unlike free chondroitin sulfate. The preapplication of nanoparticles also exhibited reduced levels of oxidative stress, cyclobutane pyrimidine dimer formation, TNF-α, and so on in UV-B-irradiated HaCaT cells. In an acute UV-B irradiation mouse model, their topical application resulted in reduced epidermal thickness and sunburn cells, unlike in the case of free chondroitin sulfate. Thus, a completely noninvasive method was used to deliver a bio-macromolecule into the skin without using injections or abrasive procedures.

pH-Triggered Adhesiveness and Cohesiveness of Chondroitin Sulfate-Catechol Biopolymer for Biomedical Applications

Nature provides biomaterials that tend to be effective to control both their adhesive and cohesive properties. A catecholamine motif found in the marine mussels, the mytilus edulis foot protein, can play adhesiveness and cohesiveness. Particularly, acidic pH drives catechol (Cat) to have adhesive function, resulting in surface coating, while basic pH allows to enhance its cohesive properties, resulting in the formation of hydrogels. In this work, we demonstrated the usefulness of Cat-conjugated chondroitin sulfate (CS) as a platform for mesenchymal stem cell culture, utilizing the adhesive property of CS-Cat as coating for different substrates and the cohesive properties as hydrogel for cells encapsulation. To prepare the CS-Cat biopolymer, dopamine (DP) was coupled to the CS by carbodiimide coupling reaction and the Cat content was determined by UV-Vis spectroscopy (4.8 ± 0.6%). To demonstrate the adhesive properties of the biopolymer, PLA, PCL, TiO₂, and SiO₂ substrates were immersed in CS-Cat solution (pH < 2). Following the coating, the surfaces became highly hydrophilic, exhibiting a contact angle less than 35°. Also, in the presence of an oxidizing agent at pH 8, CS-Cat solution immediately became a hydrogel, as shown by inverted-vial test. Finally, immortalized TERT human mesenchymal stem cells (Y201) confirmed the high cytocompatibility of the biopolymer. The CS-Cat coating significantly enabled the Y201 adhesion onto PLA substrates, while the prepared hydrogel demonstrated to be a suitable environment for the encapsulation of cells as suitable bioink for further bioprinting applications.

New insights into ToF-SIMS imaging in osteoporotic bone research

The present work focuses on the application of time-of-flight secondary ion mass spectrometry (ToF-SIMS) in osteoporotic bone research. In order to demonstrate the benefit, the authors present concrete application examples of ToF-SIMS in three different areas of bone research. ToF-SIMS as a mass spectrometric imaging technique allows simultaneous visualization of mineralized and nonmineralized bone tissue as well as implanted biomaterials and bone implant interphases. In the first example, the authors show that it is possible to study the incorporation and distribution of different components released from bone filler materials into bone with a single mass spectrometric measurement. This not only enables imaging of nonstained bone cross sections but also provides further insights beyond histologically obtained information. Furthermore, they successfully identified several mass fragments as markers for newly formed cartilage tissue and growth joint in bone. Different modes of ToF-SIMS as well as different SIMS instruments (IONTOF's TOF.SIMS 5 and M6 Hybrid SIMS, Ionoptika's J105) were used to identify these mass signals and highlight the high versatility of this method. In the third part, bone structure of cortical rat bone was investigated from bone sections embedded in technovit (polymethyl methacrylate, PMMA) and compared to cryosections. In cortical bone, they were able to image different morphological features, e.g., concentric arrangement of collagen fibers in so-called osteons as well as Haversian canals and osteocytes. In summary, the study provides examples of application and shows the strength of ToF-SIMS as a promising analytical method in the field of osteoporotic bone research.

Marine-Derived Polymeric Materials and Biomimetics: An Overview

The review covers recent literature on the ocean as both a source of biotechnological tools and as a source of bio-inspired materials. The emphasis is on marine biomacromolecules namely hyaluronic acid, chitin and chitosan, peptides, collagen, enzymes, polysaccharides from algae, and secondary metabolites like mycosporines. Their specific biological, physicochemical and structural properties together with relevant applications in biocomposite materials have been included. Additionally, it refers to the marine organisms as source of inspiration for the design and development of sustainable and functional (bio)materials. Marine biological functions that mimic reef fish mucus, marine adhesives and structural colouration are explained.

3D Extracellular Matrix Mimics: Fundamental Concepts and Role of Materials Chemistry to Influence Stem Cell Fate

Synthetic 3D extracellular matrices (ECMs) find application in cell studies, regenerative medicine, and drug discovery. While cells cultured in a monolayer may exhibit unnatural behavior and develop very different phenotypes and genotypes than in vivo, great efforts in materials chemistry have been devoted to reproducing in vitro behavior in in vivo cell microenvironments. This requires fine-tuning the biochemical and structural actors in synthetic ECMs. This review will present the fundamentals of the ECM, cover the chemical and structural features of the scaffolds used to generate ECM mimics, discuss the nature of the signaling biomolecules required and exploited to generate bioresponsive cell microenvironments able to induce a specific cell fate, and highlight the synthetic strategies involved in creating functional 3D ECM mimics.

Aquaculture and its by-products as a source of nutrients and bioactive compounds

Underutilized marine resources (e.g., algae, fish, and shellfish processing by-products), as sustainable alternatives to livestock protein and interesting sources of bioactive compounds, have attracted the attention of the researchers. Aquatic products processing industries are growing globally and producing huge amounts of by-products that often discarded as waste. However, recent studies pointed out that marine waste contains several valuable components including high-quality proteins, lipids, minerals, vitamins, enzymes, and bioactive compounds that can be used against cancer and some cardiovascular disorders. Besides, previously conducted studies on algae have shown the presence of some unique biologically active compounds and valuable proteins. Hence, this chapter points out recent advances in this area of research and discusses the importance of aquaculture and fish processing by-products as alternative sources of proteins and bioactive compounds.

An in vitro model to evaluate the properties of matrices produced by fibroblasts from osteogenesis imperfecta and Ehlers-Danlos Syndrome patients

AIM OF THE STUDY

Osteogenesis imperfecta and Ehlers Danlos syndrome are hereditary disorders caused primarily by defective collagen regulation. Osteogenesis imperfecta patients were divided to haploinsufficient and dominant negative depending on the effect of COL1A1 and COL1A2 mutations whereas Ehlers Danlos syndrome patients had a mutation in PLOD1. Although collagen abnormalities have been extensively studied in monolayer cultures, there are no reports about 3D in vitro models which may reflect more accurately the dynamic cell environment. This is the first study presenting the structural and mechanical characterization of a 3D cell-secreted model using primary patient fibroblasts.

MATERIALS AND METHODS

Fibroblasts from patients with osteogenesis imperfecta and Ehlers Danlos syndrome were cultured with ascorbic acid for 5 weeks. The effect of mutations on cytosolic and secreted collagen was tested by electrophoresis following incubation with radiolabeled ¹⁴C proline. Extracellular matrix was studied in terms of collagen fiber orientation, stiffness, as well as glycosaminoglycan and collagen content.

RESULTS AND CONCLUSIONS

Osteogenesis imperfecta patients with haploinsufficient mutations had higher percentage of anisotropic collagen fibers alignment compared to other patient groups; all patients had a lower percentage of anisotropic samples compared to healthy controls. This correlated with higher average stiffness in the control group. Glycosaminoglycan content was lower in the control and haploinsufficient groups. In cells with PLOD1 mutations, there were no differences in PLOD2 expression. This proof of concept study was able to show differences in collagen fiber orientation between different patient groups which can potentially pave the way towards the development of 3D models aiming at improved investigation of disease mechanisms.

Evaluation of the protein and bioactive compound bioaccessibility/bioavailability and cytotoxicity of the extracts obtained from aquaculture and fisheries by-products

Bioavailability, bioaccessibility, bioactivity and cytotoxicity define if a bioactive compound obtained from aquaculture and associated by-products can be assimilated and used for the body in a safe and efficient way. Four models are used to evaluate the bioavailability: in vitro (simulated gastrointestinal digestion using intestinal epithelial Caco-2 cell cultures); ex vivo (gastrointestinal organs or organoids in laboratory conditions); in situ (intestinal perfusion in animals) and in vivo (animal studies and human studies). In vitro models are very effective, predicting in vivo actions since they evaluate multiple conditions regardless physiological effects. However, in vivo systems are essential for the validation of the results. The use of a combined model between human digestion and cell culture-based models would solve these difficulties, allowing valid conclusions. These studies must be completed with the evaluation of cytotoxicity and oxidative stress markers, providing most accurate results regarding the adverse effect on the body. These methods would test the effect of food structure, food composition, dietary factors and the effect of food processing on bioavailability. Further studies should be carried out to establish a standardized method and achieve a balance between the use of in vivo and in vitro systems.

Interactions between Sclerostin and Glycosaminoglycans

Sclerostin (SOST) is a glycoprotein having many important functions in the regulation of bone formation as a key negative regulator of Wnt signaling in bone. Surface plasmon resonance (SPR), which allows for a direct quantitative analysis of the label-free molecular interactions in real-time, has been widely used for the biophysical characterization of glycosaminoglycan (GAG)-protein interactions. In the present study, we report kinetics, structural analysis and the effects of physiological conditions (e.g., salt concentrations, Ca²⁺ and Zn²⁺concentrations) on the interactions between GAGs and recombinant human (rh) and recombinant mouse (rm) SOST using SPR. SPR results revealed that both SOSTs bind heparin with high affinity (rhSOST-heparin, K_D~36 nM and rmSOST-heparin, K_D~77 nM) and the shortest oligosaccharide of heparin that effectively competes with full size heparin for SOST binding is octadecasaccharide (18mer). This heparin binding protein also interacts with other highly sulfated GAGs including, disulfated-dermatan sulfate and chondroitin sulfate E. In addition, liquid chromatography-mass spectrometry was used to characterize the structure of sulfated GAGs that bound to SOST.