Insertion of gallic acid onto chitosan promotes the differentiation of osteoblasts from murine bone marrow-derived mesenchymal stem cells

Osteoporosis: Causes, Mechanisms, Treatment and Prevention: Role of Dietary Compounds

Osteoporosis is a chronic disease that is characterized by a loss of bone density, which mainly affects the microstructure of the bones due to a decrease in bone mass, thereby making them more fragile and susceptible to fractures. Osteoporosis is currently considered one of the pandemics of the 21st century, affecting around 200 million people. Its most serious consequence is an increased risk of bone fractures, thus making osteoporosis a major cause of disability and even premature death in the elderly. In this review, we discuss its causes, the biochemical mechanisms of bone regeneration, risk factors, pharmacological treatments, prevention and the effects of diet, focusing in this case on compounds present in a diet that could have palliative and preventive effects and could be used as concomitant treatments to drugs, which are and should always be the first option. It should be noted as a concluding remark that non-pharmacological treatments such as diet and exercise have, or should have, a relevant role in supporting pharmacology, which is the recommended prescription today, but we cannot ignore that they can have a great relevance in the treatment of this disease.

High methoxyl pectin grafted onto gallic acid by one- and two-pot redox-pair procedures

The aim of this research was to graft gallic acid (GA) onto high methoxyl pectin (HMP) through the redox-pair of ascorbic acid (Aa) and hydrogen peroxide (H2O2) with one- and two-pot procedures. The effectiveness of the both procedures and the chemical, physical and antioxidant properties of the obtained HMP-GA were evaluated. HMP-GAone-pot (23.3 ± 0.21 mg GA Equivalent (GAE)/g) and HMP-GAtwo-pot (32.3 ± 0.52 mg GAE/g) were best obtained at H2O2/Aa molar ratio-HMP/GA weight ratio of 9.0-0.5 and 16.0-0.5, respectively. The UV-Vis and FT-IR spectra and along with their derivative and thermal gravimetric analyses, revealed differences between HMP-GAone-pot and HMP-GAtwo-pot. The latter exhibited a greater antioxidant capacity than the former in single electron transfer (ET), hydrogen atom transfer (HAT), and ET-HAT mixed assays. The chemical differences can be attributed to side reactions that may have interfered with the grafting reaction. Consequently, HMP-GA, possessing unique antioxidant and prebiotic properties, can be synthesized through redox-pair procedures.

Enhanced osteogenic and ROS-scavenging MXene nanosheets incorporated gelatin-based nanocomposite hydrogels for critical-sized calvarial defect repair

The healing of critical-sized bone defects is a major challenge in the field of bone tissue engineering. Gelatin-related hydrogels have emerged as a potential solution due to their desirable properties. However, their limited osteogenic, mechanical, and reactive oxygen species (ROS)-scavenging capabilities have hindered their clinical application. To overcome this issue, we developed a biofunctional gelatin-Mxene nanocomposite hydrogel. Firstly, we prepared two-dimensional (2D) Ti3C2 MXene nanosheets using a layer delamination method. Secondly, these nanosheets were incorporated into a transglutaminase (TG) enzyme-containing gallic acid-imbedded gelatin (GGA) pre-gel solution to create an injectable GGA-MXene (GM) nanocomposite hydrogel. The GM hydrogels exhibited superior compressive strength (44-75.6 kPa) and modulus (24-44.5 kPa) compared to the GGA hydrogels. Additionally, the GM hydrogel demonstrated the ability to scavenge reactive oxygen species (OH- and DPPH radicals), protecting MC3T3-E1 cells from oxidative stress. GM hydrogels were non-toxic to MC3T3-E1 cells, increased alkaline phosphatase secretion, calcium nodule formation, and upregulated osteogenic gene expressions (ALP, OCN, and RUNX2). The GM400 hydrogel was implanted in critical-sized calvarial defects in rats. Remarkably, it exhibited significant potential for promoting new bone formation. These findings indicated that GM hydrogel could be a viable candidate for future clinical applications in the treatment of critical-sized bone defects.

Dynamic hydrogel-metal-organic framework system promotes bone regeneration in periodontitis through controlled drug delivery

Periodontitis is a prevalent chronic inflammatory disease, which leads to gradual degradation of alveolar bone. The challenges persist in achieving effective alveolar bone repair due to the unique bacterial microenvironment's impact on immune responses. This study explores a novel approach utilizing Metal-Organic Frameworks (MOFs) (comprising magnesium and gallic acid) for promoting bone regeneration in periodontitis, which focuses on the physiological roles of magnesium ions in bone repair and gallic acid's antioxidant and immunomodulatory properties. However, the dynamic oral environment and irregular periodontal pockets pose challenges for sustained drug delivery. A smart responsive hydrogel system, integrating Carboxymethyl Chitosan (CMCS), Dextran (DEX) and 4-formylphenylboronic acid (4-FPBA) was designed to address this problem. The injectable self-healing hydrogel forms a dual-crosslinked network, incorporating the MOF and rendering its on-demand release sensitive to reactive oxygen species (ROS) levels and pH levels of periodontitis. We seek to analyze the hydrogel's synergistic effects with MOFs in antibacterial functions, immunomodulation and promotion of bone regeneration in periodontitis. In vivo and in vitro experiment validated the system's efficacy in inhibiting inflammation-related genes and proteins expression to foster periodontal bone regeneration. This dynamic hydrogel system with MOFs, shows promise as a potential therapeutic avenue for addressing the challenges in bone regeneration in periodontitis.

Advancing Photodynamic Antimicrobial Strategy: Sustainable Fabrication of Novel Lauryl Gallate-Chitosan Hydrophobic Films with Rapid Bacterial Capture and Biofilms Elimination Capabilities for Promoting Wound Healing

Bioinspired photoactive composites, in terms of photodynamic inactivation, cost-effectiveness, and biosafety, are promising alternatives to antibiotics for combating bacterial infections while avoiding antibacterial resistance. However, the weak bacterial membrane affinity of the photoactive substrate and the lack of synergistic antibacterial effect remain crucial shortcomings for their antibacterial applications. Herein, we developed a hydrophobic film from food antioxidant lauryl gallate covalently functionalized chitosan (LG-g-CS conjugates) through a green radical-induced grafting reaction that utilizes synergistic bacteria capture, contact-killing, and photodynamic inactivation activities to achieve enhanced bactericidal and biofilm elimination capabilities. Besides, the grafting reaction mechanism between LG and CS in the ascorbic acid (AA)/H2O2 redox system was further proposed. The LG-g-CS films feature hydrophobic side chains and photoactive phenolic hydroxyl groups, facilitating dual bactericidal activities through bacteria capture and contact-killing via strong hydrophobic and electrostatic interactions with bacterial membranes as well as blue light (BL)-driven photodynamic bacterial eradication through the enhanced generation of reactive oxygen species. As a result, the LG-g-CS films efficiently capture and immobilize bacteria and exhibit excellent photodynamic antibacterial activity against model bacteria (Escherichia coli and Staphylococcus aureus) and their biofilms under BL irradiation. Moreover, LG-g-CS films could significantly promote the healing process of S. aureus-infected wounds. This research demonstrates a new strategy for designing and fabricating sustainable bactericidal and biofilm-removing materials with a high bacterial membrane affinity and photodynamic activity.

Free Radical-Mediated Grafting of Natural Polysaccharides Such as Chitosan, Starch, Inulin, and Pectin with Some Polyphenols: Synthesis, Structural Characterization, Bioactivities, and Applications-A Review

Polyphenols and polysaccharides are very important natural products with special physicochemical properties and extensive biological activities. Recently, polyphenol-polysaccharide conjugates have been synthesized to overcome the limitations of polysaccharides and broaden their application range. Grafted copolymers are produced through chemical coupling, enzyme-mediated, and free radical-mediated methods, among which the free radical-induced grafting reaction is the most cost-effective, ecofriendly, safe, and plausible approach. Here, we review the grafting reactions of polysaccharides mediated by free radicals with various bioactive polyphenols, such as gallic acid (GA), ferulic acid (FA), and catechins. A detailed introduction of the methods and their mechanisms for free radical-mediated grafting is given. Structural characterization methods of the graft products, including thin-layer chromatography (TLC), ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) analysis, and X-ray diffraction (XRD) are introduced. Furthermore, the biological properties of polyphenol-polysaccharide conjugates are also presented, including antioxidant, antibacterial, antidiabetic, and neuroprotection activities, etc. Moreover, the potential applications of polyphenol-polysaccharide conjugates are described. Finally, the challenges and research prospects of graft products are summarized.

Phosphoserine-loaded chitosan membranes promote bone regeneration by activating endogenous stem cells

Bone defects that result from trauma, infection, surgery, or congenital malformation can severely affect the quality of life. To address this clinical problem, a phosphoserine-loaded chitosan membrane that consists of chitosan membranes serving as the scaffold support to accommodate endogenous stem cells and phosphoserine is synthesized. The introduction of phosphoserine greatly improves the osteogenic effect of the chitosan membranes via mutual crosslinking using a crosslinker (EDC, 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide). The morphology of PS-CS membranes was shown by scanning electron microscopy (SEM) to have an interconnected porous structure. The incorporation of phosphoserine into chitosan membranes was confirmed by energy dispersive spectrum (EDS), Fourier Transforms Infrared (FTIR), and X-ray diffraction (XRD) spectrum. The CCK8 assay and Live/Dead staining, Hemolysis analysis, and cell adhesion assay demonstrated that PS-CS membranes had good biocompatibility. The osteogenesis-related gene expression of BMSCs was higher in PS-CS membranes than in CS membranes, which was verified by alkaline phosphatase (ALP) activity, immunofluorescence staining, and real-time quantitative PCR (RT-qPCR). Furthermore, micro-CT and histological analysis of rat cranial bone defect demonstrated that PS-CS membranes dramatically stimulated bone regeneration in vivo. Moreover, H&E staining of the main organs (heart, liver, spleen, lung, or kidney) showed no obvious histological abnormalities, revealing that PS-CS membranes were no additional systemic toxicity in vivo. Collectively, PS-CS membranes may be a promising candidate for bone tissue engineering.

UPLC-ESI-Q-TOF-MSE-based metabolomics analysis of Acer mono sap and evaluation of osteogenic activity in mouse osteoblast cells

Investigation of phytochemicals and bioactive molecules is tremendously vital for the applications of new plant resources in chemistry, food, and medicine. In this study, the chemical profiling of sap of Acer mono (SAM), a Korean syrup known for its anti-osteoporosis effect, was performed using UPLC-ESI-Q-TOF-MS^E analysis. A total of 23 compounds were identified based on the mass and fragmentation characteristics and most of the compounds have significant biomedical applications. The in vitro antioxidant assessment of SAM indicated excellent activity by scavenging DPPH and ABTS-free radicals and were found to be 23.35 mg mL^-1 and 29.33 mg mL^-1, respectively, as IC₅₀ concentrations. As well, the in vitro proliferation effect of the SAM was assessed against mouse MC3T3-E1 cells, and the results showed that the SAM enhanced the proliferation of the cells, and 12.5 mg mL^-1 and 25 mg mL^-1 of SAM were selected for osteogenic differentiation. The morphological analysis clearly evidenced the SAM enhanced the osteogenic activity in MC3T3-E1 cells by the increased deposition of extracellular calcium and nodule formation. Moreover, the qRT-PCR analysis confirmed the increased expression of osteoblast marker gene expression including ALP, osteocalcin, osteopontin, collagen1α1, Runx2, and osterix in SAM-treated MC3T3-E1 cells. Together, these results suggest that SAM possesses osteogenic effects and can be used for bone regeneration and bone loss-associated diseases such as osteoporosis.

Gallic Acid Ameliorates the Inflammatory State of Periodontal Ligament Stem Cells and Promotes Pro-Osteodifferentiation Capabilities of Inflammatory Stem Cell-Derived Exosomes

The slow proliferation rate and poor osteodifferentiation ability of inflammatory periodontal membrane stem cells extracted from periodontitis tissues (i-PDLSCs) account for poor efficiency in treating inflammatory bone loss. Exosomes reportedly have inducible and relatively stable components, allowing them to promote inflammatory bone repair, but obtaining i-PDLSCs exosomes with the ability to promote osteodifferentiation is challenging. In the present study, i-PDLSCs were extracted from periodontal membrane tissues of patients with severe periodontitis, and in vitro induction with gallic acid (GA) significantly promoted the proliferative activity of i-PDLSCs at a concentration of 10 mM, with TC0 of 11.057 mM and TC50 of 67.56 mM for i-PDLSCs. After mRNA sequencing, we found that GA could alleviate oxidative stress in i-PDLSCs and increase its mitochondrial membrane potential and glucose aerobic metabolism level, thus promoting the osteodifferentiation of i-PDLSCs. After exosomes of i-PDLSCs after GA induction (i-EXO-GA) were isolated by differential centrifugation, we found that 200 ug/mL of i-EXO-GA could remarkably promote the osteodifferentiation of i-PDLSCs. Overall, our results suggest that GA induction can enhance the proliferation and osteodifferentiation in primary cultures of i-PDLSCs in vitro, mediated by alleviating oxidative stress and glycometabolism levels in cells, which further influences the osteodifferentiation-promoting ability of i-EXO-GA. Overall, we provide a viable cell and exosome induction culture method for treating inflammatory alveolar defects associated with periodontitis.

Heme oxygenase-1 induction by gallic acid-g-chitosan is an important event in modulating adipocyte differentiation

Obesity, one of the common worldwide chronic health diseases co-relates with adipogenesis. Adipogenesis is a complex biological action of the emergence of mature adipocytes from the differentiation of pre-adipocytes and the disfunction of this process leads to the development of metabolic issues in obesity. Recently, much attention has been paid to utilizing natural compounds to discover their biological activities. This study focused on investigating the probable anti-adipogenic effects of gallic acid-g-chitosan (GAC) and plain chitosan (PC) through regulating the heme oxygenase-1 (HO-1)/Nrf2 pathway on mesenchymal stem cells. Gallic acid is grafted onto the PC backbone to improve its specific physical and biological properties. GAC showed promising anti-adipogenic effects by enhancing HO-1 expression and lipolysis and as well as suppressing lipid accumulation, reactive oxygen species, and pro-inflammatory cytokines production, transcription factor expression compared to the PC treatment. On the contrary, zinc protoporphyrin ІX (ZnPP), a HO-1 inhibitor reversed these effects of GAC on adipogenesis. Taken all together, this study revealed that grafting GA onto the chitosan improved potential anti-adipogenic activity by induction of the HO-1/Nrf2 pathway on mesenchymal stem cells (MSCs). PRACTICAL APPLICATIONS: GAC is a well-known copolymer with versatile bioactivities such as antimicrobial, antioxidant, and anti-diabetic activity. However, the anti-adipogenic effect of GAC has not been explored in MSCs. This study demonstrated that GAC inhibited adipocyte differentiation in MSCs through HO-1 activation. These findings suggest that GAC can be applied practically from different perspectives. GAC can be applied in the pharmacological industry to the development of anti-obesity drugs, medicinal perspectives for the treatment of obesity and obesity-related diseases, and in the food industry as a functional food to promote health and decrease the risk of diseases.

Three Classes of Antioxidant Defense Systems and the Development of Postmenopausal Osteoporosis

Osteoporosis is a common bone imbalance disease that threatens the health of postmenopausal women. Estrogen deficiency accelerates the aging of women. Oxidative stress damage is regarded as the main pathogenesis of postmenopausal osteoporosis. The accumulation of reactive oxygen species in the bone microenvironment plays a role in osteoblast and osteoclast apoptosis. Improving the oxidative state is essential for the prevention and treatment of postmenopausal osteoporosis. There are three classes of antioxidant defense systems in the body to eliminate free radicals and peroxides including antioxidant substances, antioxidant enzymes, and repair enzymes. In our review, we demonstrated the mechanism of antioxidants and their effect on bone metabolism in detail. We concluded that glutathione/oxidized glutathione (GSH/GSSG) conversion involved the PI3K/Akt-Nrf2/HO-1 signaling pathway and that the antioxidant enzyme-mediated mitochondrial apoptosis pathway of osteoblasts was necessary for the development of postmenopausal osteoporosis. Since the current therapeutic effects of targeting bone cells are not significant, improving the systemic peroxidation state and then regulating bone homeostasis will be a new method for the treatment of postmenopausal osteoporosis.

Exosome-functionalized magnesium-organic framework-based scaffolds with osteogenic, angiogenic and anti-inflammatory properties for accelerated bone regeneration

Exosomes derived from human adipose-derived stem cells (hADSCs-Exos) have shown potential as an effective therapeutic tool for repairing bone defects. Although metal-organic framework (MOF) scaffolds are promising strategies for bone tissue regeneration, their potential use for exosome loading remains unexplored. In this study, motivated by the potential advantages of hADSCs-Exos and Mg-GA MOF, we designed and synthesized an exosome-functionalized cell-free PLGA/Mg-GA MOF (PLGA/Exo-Mg-GA MOF) scaffold, taking using of the benefits of hADSCs-Exos, Mg²⁺, and gallic acid (GA) to construct unique nanostructural interfaces to enhance osteogenic, angiogenic and anti-inflammatory capabilities simultaneously. Our in vitro work demonstrated the beneficial effects of PLGA/Exo-Mg-GA MOF composite scaffolds on the osteogenic effects in human bone marrow-derived mesenchymal stem cells (hBMSCs) and angiogenic effects in human umbilical endothelial cells (HUVECs). Slowly released hADSCs-Exos from composite scaffolds were phagocytosed by co-cultured cells, stabilized the bone graft environment, ensured blood supply, promoted osteogenic differentiation, and accelerated bone reconstruction. Furthermore, our in vivo experiments with rat calvarial defect model showed that PLGA/Exo-Mg-GA MOF scaffolds promoted new bone formation and satisfactory osseointegration. Overall, we provide valuable new insights for designing exosome-coated nanocomposite scaffolds with enhanced osteogenesis property.

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PLGA/Exo-Mg-GA MOF scaffolds with nanostructures were synthesized, on which exosomes were densely deposited on the above scaffolds.

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Composite scaffolds with exosomes can actualize the slow release of exosomes, Mg ions and gallic acid.

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PLGA/Exo-Mg-GA MOF scaffolds exhibit great biocompatibility and osteogenic differentiation of hBMSCs.

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PLGA/Exo-Mg-GA MOF scaffolds have excellent osteogenic, pro-angiogenic and anti-inflammatory activity.

Mesenchymal stem cells: ideal seeds for treating diseases

Mesenchymal stem cells (MSCs), a kind of multipotent stem cells with self-renewal ability and multi-differentiation ability, have become the “practical stem cells” for the treatment of diseases. MSCs have immunomodulatory properties and can be used to treat autoimmune diseases, such as systemic lupus erythematosus (SLE) and Crohn’s disease. MSCs also can be used in cancer and aging. At present, many clinical experiments are using MSCs. MSCs can reduce the occurrence of inflammation and apoptosis of tissue cells, and promote the proliferation of endogenous tissue and organ cells, so as to achieve the effect of repairing tissue and organs. MSCs presumably also play an important role in Corona Virus Disease 2019 (COVID-19) infection.