(-)-Epigallocatechin-3-gallate (EGCG) enhances healing of femoral bone defect

Biomimetic mineralization of collagen from fish scale to construct a functionally gradient lamellar bone-like structure for guided bone regeneration

Wide used guided bone regeneration (GBR) membrane materials, such as collagen, Teflon, and other synthesized polymers, present a great challenge in term of integrating the mechanical property and degradation rate when addressing critical bone defects. Therefore, inspired by the distinctive architecture of fish scales, this study utilized epigallocatechin gallate to modify decellularized fish scales following biomimetic mineralization to fabricate a GBR membrane that mimics the structure of lamellar bone. The structure, physical and chemical properties, and biological functions of the novel GBR membrane were evaluated. Results indicate that the decellularized fish scale with 5 remineralization cycles (5R-E-DCFS) exhibited a composite and structure similar to natural bone and had a special functionally gradient mineral contents character, demonstrating excellent mechanical properties, hydrophilicity, and degradation properties. In vitro, the 5R-E-DCFS membrane exhibited excellent cytocompatibility promoting Sprague-Dawley (SD) rat bone marrow mesenchymal stem cell proliferation and differentiation up-regulating the expression of osteogenic-related genes and proteins. Furthermore, in vivo, the 5R-E-DCFS membrane promoted the critical skull bone defects of SD rats repairment and regeneration. Therefore, this innovative biomimetic membrane holds substantial clinical potential as an ideal GBR membrane with mechanical properties for space-making and suitable degradation rate for bone regeneration to manage bone defects.

Metal-Phenolic Networks-Reinforced Extracellular Matrix Scaffold for Bone Regeneration via Combining Radical-Scavenging and Photo-Responsive Regulation of Microenvironment

The limited regulation strategies of the regeneration microenvironment significantly hinder bone defect repair effectiveness. One potential solution is using biomaterials capable of releasing bioactive ions and biomolecules. However, most existing biomaterials lack real-time control features, failing to meet high regulation requirements. Herein, a new Strontium (Sr) and epigallocatechin-3-gallate (EGCG) based metal-phenolic network with polydopamine (PMPNs) modification is prepared. This material reinforces a biomimetic scaffold made of extracellular matrix (ECM) and hydroxyapatite nanowires (nHAW). The PMPNs@ECM/nHAW scaffold demonstrates exceptional scavenging of free radicals and reactive oxygen species (ROS), promoting HUVECs cell migration and angiogenesis, inducing stem cell osteogenic differentiation, and displaying high biocompatibility. Additionally, the PMPNs exhibit excellent photothermal properties, further enhancing the scaffold's bioactivities. In vivo studies confirm that PMPNs@ECM/nHAW with near-infrared (NIR) stimulation significantly promotes angiogenesis and osteogenesis, effectively regulating the microenvironment and facilitating bone tissue repair. This research not only provides a biomimetic scaffold for bone regeneration but also introduces a novel strategy for designing advanced biomaterials. The combination of real-time photothermal intervention and long-term chemical intervention, achieved through the release of bioactive molecules/ions, represents a promising direction for future biomaterial development.

A Zn2+ cross-linked sodium alginate/epigallocatechin gallate hydrogel scaffold for promoting skull repair

The optimal material for repairing skull defects should exhibit outstanding biocompatibility and mechanical properties. Specifically, hydrogel scaffolds that emulate the microenvironment of the native bone extracellular matrix play a vital role in promoting osteoblast adhesion, proliferation, and differentiation, thereby yielding superior outcomes in skull reconstruction. In this study, a composite network hydrogel comprising sodium alginate (SA), epigallocatechin gallate (EGCG), and zinc ions (Zn2+) was developed to establish an ideal osteogenic microenvironment for bone regeneration. Initially, physical entanglement and hydrogen bonding between SA and EGCG resulted in the formation of a primary network hydrogel known as SA-EGCG. Subsequently, the inclusion of Zn2+ facilitated the creation of a composite network hydrogels named SA-EGCG-Zn2+ via dynamic coordination bonds with SA and EGCG. The engineered SA-EGCG2 %-Zn2+ hydrogels offered an environment mimicking the native extracellular matrix (ECM). Moreover, the sustained release of Zn2+ from the hydrogel effectively enhanced cell adhesion, promoted proliferation, and stimulated osteoblast differentiation. In vitro experiments have shown that SA-EGCG2 %-Zn2+ hydrogels greatly enhance the attachment and growth of osteoblast precursor cells (MC3T3-E1), while also increasing the expression of genes related to osteogenesis in these cells. Additionally, in vivo studies have confirmed that SA-EGCG2 %-Zn2+ hydrogels promote new bone formation and accelerate the regeneration of bone in situ, indicating promising applications in the realm of bone tissue engineering.

Multifaceted Materials for Enhanced Osteogenesis and Antimicrobial Properties on Bioplastic Polyetheretherketone Surfaces: A Review

Implant-associated infections and the increasing number of bone implants loosening and falling off after implantation have become urgent global challenges, hence the need for intelligent alternative solutions to combat implant loosening and falling off. The application of polyetheretherketone (PEEK) in biomedical and medical therapy has aroused great interest, especially because its elastic modulus close to bone provides an effective alternative to titanium implants, thereby preventing the possibility of bone implants loosening and falling off due to the mismatch of elastic modulus. In this Review, we provide a comprehensive overview of recent advances in surface modifications to prevent bone binding deficiency and bacterial infection after implantation of bone implants, starting with inorganics for surface modification, followed by organics that can effectively promote bone integration and antimicrobial action. In addition, surface modifications derived from cells and related products of biological activity have been proposed, and there is increasing evidence of clinical potential. Finally, the advantages and future challenges of surface strategies against medical associated poor osseointegration and infection are discussed, with promising prospects for developing novel osseointegration and antimicrobial PEEK materials.

Evaluation of High-Performance Polyether Ether Ketone Polymer Treated with Piranha Solution and Epigallocatechin-3-Gallate Coating

Background

Dental implantation has become a standard procedure with high success rates, relying on achieving osseointegration between the implant surface and surrounding bone tissue. Polyether ether ketone (PEEK) is a promising alternative to traditional dental implant materials like titanium, but its osseointegration capabilities are limited due to its hydrophobic nature and reduced surface roughness.

Objective

The aim of the study is to increase the surface roughness and hydrophilicity of PEEK by treating the surface with piranha solution and then coating the surface with epigallocatechin-3-gallate (EGCG) by electrospraying technique.

Materials and Methods

The study includes four groups intended to investigate the effect of piranha treatment and EGCG coating: a control group of PEEK discs with no treatment (C), PEEK samples treated with piranha solution (P), a group of PEEK samples coated with EGCG (E), and a group of PEEK samples treated with piranha solution and coated with EGCG (PE). Surface roughness, wettability, and microhardness were assessed through statistical analysis.

Results

Piranha treatment increased surface roughness, while EGCG coating moderated it, resulting in an intermediate roughness in the PE group. EGCG significantly improved wettability, as indicated by the reduced contact angle. Microhardness increased by about 20% in EGCG-coated groups compared to noncoated groups. Statistical analysis confirmed significant differences between groups in all tests.

Conclusion

This study demonstrates the potential of EGCG coating to enhance the surface properties of PEEK as dental implants. The combined piranha and EGCG modification approach shows promise for improved osseointegration, although further vivo research is necessary. Surface modification techniques hold the key to optimizing biomaterial performance, bridging the gap between laboratory findings and clinical implementation in dental implantology.

Pain management for hospitalized patients with rib fractures: A systematic review of randomized clinical trials

STUDY OBJECTIVE

Rib fractures (RF) are common injuries. Multiple analgesia strategies are available for treatment of pain associated with RF. However, the optimal multimodal technique for pain management is not known. The primary aim of this review was to evaluate the status of evidence derived from randomized clinical trials (RCTs) on the effectiveness of pain management modalities for rib fracture pain. Other patient-centered outcomes were secondary objectives.

METHODS

Searches were conducted in MEDLINE, Embase, Scopus, and Cochrane Library. The screening process involved two phases, two researchers independently screened the title and abstract and subsequently screened full text. RCT data were extracted independently by two research team members. Consensus was achieved by comparison and discussion when needed. Risk of bias assessment was performed using the Cochrane Risk of Bias 2 tool.

RESULTS

A total of 1344 citations were identified. Title and abstract screening excluded 1128 citations, and full text review excluded 177 articles. A total of 32 RCTs were included in the full review. Multiple analgesia techniques and medications were identified and their effect on pain score and need for rescue opioid analgesia. None of the included studies were judged to have a high risk of bias, while only 10 studies were assessed as having a low risk of bias.

CONCLUSIONS

This systematic review found that studies are of low quality with diverse methodologies and outcomes. A reduction in pain scores was found for epidural analgesia when compared with other modalities. However, the low quality of the evidence necessitates cautious interpretation of this finding. PROSPERO registration: CRD42022376298 (Nov, 16, 2022).

Regulation of the Notch signaling pathway by natural products for cancer therapy

The Notch signaling pathway is an evolutionarily conserved pathway that modulates normal biological processes involved in cellular differentiation, apoptosis, and stem cell self-renewal in a context-dependent fashion. Attributed to its pleiotropic physiological roles, both overexpression and silencing of the pathway are associated with the emergence, progression, and poorer prognosis in various types of cancer. To decrease disease incidence and promote survival, targeting Notch may have chemopreventive and anti-cancer effects. Natural products with profound historical origins have distinguished themselves from other therapies due to their easy access, high biological compatibility, low toxicity, and reliable effects at specific physiological sites in vivo. This review describes the Notch signaling pathway, particularly its normal activation process, and some main illnesses related to Notch signaling pathway dysregulation. Emphasis is placed on the effects and mechanisms of natural products targeting the Notch signaling pathway in diverse cancer types, including curcumin, ellagic acid (EA), resveratrol, genistein, epigallocatechin-3-gallate (EGCG), quercetin, and xanthohumol and so on. Existing evidence indicates that natural products are feasible solution to fight against cancer by targeting Notch signaling, either alone or in combination with current therapeutic agents.

Oxidative Stress and Natural Antioxidants in Osteoporosis: Novel Preventive and Therapeutic Approaches

This review reports in detail the cellular and molecular mechanisms which regulate the bone remodeling process in relation to oxidative stress (OS), inflammatory factors, and estrogen deficiency. OS is considered an important pathogenic factor of osteoporosis, inducing osteocyte apoptosis and varying levels of specific factors, such as receptor activator κB ligand (RANKL), sclerostin, and, according to recent evidence, fibroblast growth factor 23, with consequent impairment of bone remodeling and high bone resorption. Bone loss increases the risk of fragility fractures, and the most commonly used treatments are antiresorptive drugs, followed by anabolic drugs or those with a double effect. In addition, recent data show that natural antioxidants contained in the diet are efficient in preventing and reducing the negative effects of OS on bone remodeling and osteocytes through the involvement of sirtuin type 1 enzyme. Indeed, osteocytes and some of their molecular factors are considered potential biological targets on which antioxidants can act to prevent and reduce bone loss, as well as to promote bone anabolic and regenerative processes by restoring physiological bone remodeling. Several data suggest including antioxidants in novel therapeutic approaches to develop better management strategies for the prevention and treatment of osteoporosis and OS-related bone diseases. In particular, anthocyanins, as well as resveratrol, lycopene, oleuropein, some vitamins, and thiol antioxidants, could have protective and therapeutic anti-osteoporotic effects.

A mechanistic review of chinese medicine polyphenols on bone formation and resorption

Bone reconstruction includes a steady state system of bone formation and bone absorption. This tight coupling requires subtle coordination between osteoblasts and osteoclasts. If this balance is broken, it will lead to bone mass loss, bone density reduction, and bone metabolic diseases, such as osteoporosis. Polyphenols in Chinese herbal medicines are active ingredients in plant extracts with high safety and few side effects, and they can play a role in affecting bone formation and bone resorption. Some of these have estrogen-like effects and can better target bone health in postmenopausal women. The purpose of this review is to provide comprehensive information on the mechanisms underlying the relationship between traditional Chinese medicine polyphenols and bone formation or bone resorption.

Ablation of Discoidin Domain Receptor 1 Provokes an Osteopenic Phenotype by Regulating Osteoblast/Osteocyte Autophagy and Apoptosis

Discoidin domain receptor 1 (DDR1) is a collagen receptor that belongs to the receptor tyrosine kinase family. We have previously shown that DDR1 plays a crucial role during bone development, resulting in dwarfism and a short stature in osteoblast-specific knockout mice (OKO mice). However, the detailed pathophysiological effects of DDR1 on bone development throughout adulthood have remained unclear. This study aims to identify how DDR1 regulates osteoblast and osteocyte functions in vivo and in vitro during bone development in adulthood. The metabolic changes in bone tissues were analyzed using Micro-CT and immunohistochemistry staining (IHC) in vivo; the role of DDR1 in regulating osteoblasts was examined in MC3T3-E1 cells in vitro. The Micro-CT analysis results demonstrated that OKO mice showed a 10% reduction in bone-related parameters from 10 to 14 weeks old and a significant reduction in cortical thickness and diameter compared with flox/flox control mice (FF) mice. These results indicated that DDR1 knockout in OKO mice exhibiting significant bone loss provokes an osteopenic phenotype. The IHC staining revealed a significant decrease in osteogenesis-related genes, including RUNX2, osteocalcin, and osterix. We noted that DDR1 knockout significantly induced osteoblast/osteocyte apoptosis and markedly decreased autophagy activity in vivo. Additionally, the results of the gain- and loss-of-function of the DDR1 assay in MC3T3-E1 cells indicated that DDR1 can regulate the osteoblast differentiation through activating autophagy by regulating the phosphorylation of the mechanistic target of rapamycin (p-mTOR), light chain 3 (LC3), and beclin-1. In conclusion, our study highlights that the ablation of DDR1 results in cancellous bone loss by regulating osteoblast/osteocyte autophagy. These results suggest that DDR1 can act as a potential therapeutic target for managing cancellous bone loss.

The Role of Flavonoids in the Osteogenic Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) play an important role in developing bone tissue engineered constructs due to their osteogenic and chondrogenic differentiation potential. MSC-based tissue engineered constructs are generally considered a safe procedure, however, the long-term results obtained up to now are far from satisfactory. The main causes of these therapeutic limitations are inefficient homing, engraftment, and directional differentiation. Flavonoids are a secondary metabolite, widely existed in nature and have many biological activities. For a long time, researchers have confirmed the anti-osteoporosis effect of flavonoids through in vitro cell experiments, animal studies. In recent years the regulatory effects of flavonoids on mesenchymal stem cells (MSCs) differentiation have been received increasingly attention. Recent studies revealed flavonoids possess the ability to modulate self-renewal and differentiation potential of MSCs. In order to facilitate further research on MSCs osteogenic differentiation of flavonoids, we surveyed the literature published on the use of flavonoids in osteogenic differentiation of MSCs, and summarized their pharmacological activities as well as the underlying mechanisms, aimed to explore their promising therapeutic application in bone disorders and bone tissue engineered constructs.

Analysis of the molecular mechanisms by flavonoids with potential use for osteoporosis prevention or therapy

BACKGROUND

Osteoporosis is the most common skeletal disorder worldwide. Flavonoids have the potential to alleviate bone alterations in osteoporotic patients with the advantage of being safer and less expensive than the conventional therapies.

OBJECTIVE

The main objective is to analyze the molecular mechanisms triggered in bone by different subclasses of flavonoids. In addition, this review provides an up-to-date overview on the cellular and molecular aspects of osteoporotic bones versus healthy bones, and a brief description of some epidemiological studies indicating that flavonoids could be useful for osteoporosis treatment.

METHODS

The PubMed database was searched in the range of years 2001- 2021 using the keywords osteoporosis, flavonoids, and their subclasses such as flavones, flavonols, flavanols, isoflavones, flavanones and anthocyanins, focusing the data on the molecular mechanisms triggered in bone.

RESULTS

Although flavonoids comprise many compounds that differ in structure, their effects on bone loss in postmenopausal women or in ovariectomized-induced osteoporotic animals are quite similar. Most of them increase bone mineral density and bone strength, which occur through enhancement of osteoblastogenesis and osteoclast apoptosis, decrease in osteoclastogenesis as well as increase in neovascularization on the site of the osteoporotic fracture.

CONCLUSION

Several molecules of signaling pathways are involved in the effect of flavonoids on osteoporotic bone. Whether all flavonoids have a common mechanism or they act as ligands of estrogen receptors remain to be established. More clinical trials are necessary to know better their safety, efficacy, delivery and bioavailability in humans, as well as comparative studies with conventional therapies.

Intra-articular low-dose parathyroid hormone (1-34) improves mobility and articular cartilage quality in a preclinical age-related knee osteoarthritis model

Aims

Osteoarthritis (OA) is prevalent among the elderly and incurable. Intra-articular parathyroid hormone (PTH) ameliorated OA in papain-induced and anterior cruciate ligament transection-induced OA models; therefore, we hypothesized that PTH improved OA in a preclinical age-related OA model.

Methods

Guinea pigs aged between six and seven months of age were randomized into control or treatment groups. Three- or four-month-old guinea pigs served as the young control group. The knees were administered 40 μl intra-articular injections of 10 nM PTH or vehicle once a week for three months. Their endurance as determined from time on the treadmill was evaluated before kill. Their tibial plateaus were analyzed using microcalculated tomography (μCT) and histological studies.

Results

PTH increased the endurance on the treadmill test, preserved glycosaminoglycans, and reduced Osteoarthritis Research Society International score and chondrocyte apoptosis rate. No difference was observed in the subchondral plate bone density or metaphyseal trabecular bone volume and bone morphogenetic 2 protein staining.

Conclusion

Subchondral bone is crucial in the initiation and progression of OA. Although previous studies have shown that subcutaneous PTH alleviates knee OA by improving subchondral and metaphyseal bone mass, we demonstrated that intra-articular PTH injections improved spontaneous OA by directly affecting the cartilage rather than the subchondral or metaphyseal bone in a preclinical age-related OA model.

Cite this article: Bone Joint Res 2021;10(8):514–525.

Intra-Articular Injection of (-)-Epigallocatechin 3-Gallate (EGCG) Ameliorates Cartilage Degeneration in Guinea Pigs with Spontaneous Osteoarthritis

Osteoarthritis (OA) is the most prevalent joint disease that causes an enormous burden of disease worldwide. (-)-Epigallocatechin 3-gallate (EGCG) has been reported to reduce post-traumatic OA progression through its anti-inflammatory property. Aging is the most crucial risk factor of OA, and the majority of OA incidences are related to age and not trauma. In this study, we assess whether EGCG can ameliorate cartilage degradation in primary OA. In an in-vitro study, real-time PCR was performed to assess the expression of genes associated with human articular chondrocyte homeostasis. A spontaneously occurring OA model in guinea pigs was used to investigate the effect of EGCG in vivo. OA severity was evaluated using Safranin O staining and Osteoarthritis Research Society International (OARSI) scores, as well as by immunohistochemical (IHC) analysis to determine the protein level of type II collagen (Col II), matrix metalloproteinase 13 (MMP-13), and p16 ink4a in articular cartilage. In the in-vitro study, EGCG increased the gene expression of aggrecan and Col II and decreased the expression of interleukin-1, cyclooxygenase 2, MMP-13, alkaline phosphatase, Col X, and p16 Ink4a; EGCG treatment also attenuated the degraded cartilage with a lower OARSI score. Meanwhile, IHC results showed that EGCG exerted an anti-OA effect by reducing ECM degradation, cartilage inflammation, and cell senescence with a less-immunostained Col II, MMP-13, and p16 Ink4a. In conclusion, these findings suggest that EGCG may be a potential disease-modifying OA drug for the treatment of primary OA.

Intra-Articular Injection of (-)-Epigallocatechin 3-Gallate to Attenuate Articular Cartilage Degeneration by Enhancing Autophagy in a Post-Traumatic Osteoarthritis Rat Model

(-)-Epigallocatechin 3-gallate (EGCG) is the main active green tea catechin and has a wide variety of benefits for health. Post-traumatic osteoarthritis (PTOA) occurs as a consequence of joint injuries that commonly happen in the young population. In this study, we investigated the effects of EGCG on PTOA prevention by using the anterior cruciate ligament transection (ACLT)–OA model and further investigated the roles of autophagy in OA treatment. Our results showed that intra-articular injection of EGCG significantly improved the functional performances and decreased cartilage degradation. EGCG treatment attenuated the inflammation on synovial tissue and cartilage through less immunostained cyclooxygenase-2 and matrix metalloproteinase-13. We further noted EGCG may modulate the chondrocyte apoptosis by activation of the cytoprotective autophagy through reducing the expression of the mTOR and enhancing the expression of microtubule-associated protein light chain 3, beclin-1, and p62. In conclusion, intra-articular injection of EGCG after ACL injury inhibited the joint inflammation and cartilage degradation, thereby increasing joint function. EGCG treatment also reduced the chondrocyte apoptosis, possibly by activating autophagy. These findings suggested that EGCG may be a potential disease-modifying drug for preventing OA progression.

Assessing the analgesic efficacy of oral epigallocatechin-3-gallate on epidural catheter analgesia in patients after surgical stabilisation of multiple rib fractures: a prospective double-blind, placebo-controlled clinical trial

CONTEXT

Thoracic trauma results in multiple rib fractures (MRF), and surgical stabilisation of rib fractures (SSRF) can relieve fracture pain. Epigallocatechin-3-gallate (EGCG) is reported to exhibit beneficial effects in bone-related metabolic and differentiation processes.

OBJECTIVE

To study the clinical effect of EGCG on regional analgesia for pain relief in MRF patients after SSRF.

MATERIALS AND METHODS

Ninety-seven MRF patients (61 males, 36 females) who were on epidural catheter analgesia after SSRF were recruited. They were randomly divided into: oral EGCG 100 mg (oral grade) twice daily for 10 days and placebo groups. Pain scores, incentive spirometry (IS) volumes, respiratory rate and oxygen saturation (SpO₂) were assessed day 10 after SSRF.

RESULTS

Comparing results from the placebo and EGCG group, in the 10-day intervention course, oral EGCG reduced pain score (8 at base line vs. 4 at end of intervention in EGCG group, p < 0.05; 4 in EGCG group vs. 6 in placebo group at end of intervention, p < 0.05), improved IS volume (713 at base line vs. 1072 at end of intervention in EGCG group, p < 0.05; 1072 in EGCG group vs. 953 in placebo group at end of intervention, p < 0.05) and respiratory rate (24 at base line vs. 15 at end of intervention in EGCG group, p < 0.05; 15 in EGCG group vs. 19 in placebo group at end of intervention, p < 0.05). However, no further enhancing effect on SpO₂ was observed in the EGCG group (0.98 in EGCG group vs. 0.98 in placebo group at end of intervention, p > 0.05).

DISCUSSION AND CONCLUSIONS

Although the study is limited by a relatively small sample size and lack of serum factor analysis, the key results and the study design, for the first time, nevertheless pave the way for trials with larger number of patients to understand the effect of EGCG in MRF patients that are undergoing SSRF.

Osteoprotective Roles of Green Tea Catechins

Osteoporosis is the second most common disease only secondary to cardiovascular disease, with the risk of fracture increasing with age. Osteoporosis is caused by an imbalance between osteoblastogenesis and osteoclastogenesis processes. Osteoclastogenesis may be enhanced, osteoblastogenesis may be reduced, or both may be evident. Inflammation and high reactive oxygen enhance osteoclastogenesis while reducing osteoblastogenesis by inducing osteoblast apoptosis and suppressing osteoblastic proliferation and differentiation. Catechins, the main polyphenols found in green tea with potent anti-oxidant and anti-inflammatory properties, can counteract the deleterious effects of the imbalance of osteoblastogenesis and osteoclastogenesis caused by osteoporosis. Green tea catechins can attenuate osteoclastogenesis by enhancing apoptosis of osteoclasts, hampering osteoclastogenesis, and prohibiting bone resorption in vitro. Catechin effects can be directly exerted on pre-osteoclasts/osteoclasts or indirectly exerted via the modulation of mesenchymal stem cells (MSCs)/stromal cell regulation of pre-osteoclasts through activation of the nuclear factor kB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system. Catechins also can enhance osteoblastogenesis by enhancing osteogenic differentiation of MSCs and increasing osteoblastic survival, proliferation, differentiation, and mineralization. The in vitro effects of catechins on osteogenesis have been confirmed in several animal models, as well as in epidemiological observational studies on human subjects. Even though randomized control trials have not shown that catechins provide anti-fracture efficacy, safety data in the trials are promising. A large-scale, placebo-controlled, long-term randomized trial with a tea regimen intervention of optimal duration is required to determine anti-fracture efficacy.

Thrombomodulin Functional Domains Support Osteoblast Differentiation and Bone Healing in Diabetes in Mice

Thrombomodulin (TM) is a transmembrane glycoprotein that contains five functional domains. Soluble TM (sTM), comprising extracellular domains TMD1 (lectin-like), TMD2 (epidermal growth factor [EGF]-like repeat containing), and TMD3 (serine-threonine rich), can be shed from cells by the intramembrane protease rhomboid-like-2 (RHBDL2). TM is expressed by osteoblasts, yet its role there has not been determined. Herein we aimed to investigate the properties of TM and its domains in osteoblast function and bone repair following injury in diabetes. In response to a scratch injury of cultured osteoblast-like MG63 cells, expression of TM and RHBDL2 was enhanced, with increased release of sTM. Conditioned media from the injured cells promoted osteoblast migration, an effect that was lacking with conditioned media from MG63 cells in which TM was silenced by shRNA. Exogenous recombinant TMD1 had no effect on osteoblast activities or on bone repair in vivo. However, TM domains 2 and 3 (TMD2/3), induced MG63 cell migration, proliferation and mineralization in vitro, and when locally administered in mice, improved in vivo healing of injured calvarium. This beneficial effect of TMD2/3, mediated via fibroblast growth factor receptor (FGFR)/ERK signaling pathways, was also observed in vitro under high glucose conditions where endogenous TM expression was reduced, and in vivo in diabetic mice following tibia fracture or calvarium injury, where the osteoblastic response and healing were otherwise dampened. Taken together, osteoblast TM participates in bone healing, and recombinant TMD2/3 holds promise as a novel therapy for diabetic bone defect healing. © 2020 American Society for Bone and Mineral Research.

Green Tea Catechin (-)-Epigallocatechin-3-Gallate (EGCG) Facilitates Fracture Healing

Green tea drinking can ameliorate postmenopausal osteoporosis by increasing the bone mineral density. (-)-Epigallocatechin-3-gallate (EGCG), the abundant and active compound of tea catechin, was proven to be able to reduce bone loss and ameliorate microarchitecture in female ovariectomized rats. EGCG can also enhance the osteogenic differentiation of murine bone marrow mesenchymal stem cells and inhibit the osteoclastogenesis in RAW264.7 cells by modulation of the receptor activator of nuclear factor-kB (RANK)/RANK ligand (RANKL)/osteoprotegrin (OPG) (RANK/RANKL/OPG) pathway. Our previous study also found that EGCG can promote bone defect healing in the distal femur partially via bone morphogenetic protein-2 (BMP-2). Considering the osteoinduction property of BMP-2, we hypothesized that EGCG could accelerate the bone healing process with an increased expression of BMP-2. In this manuscript, we studied whether the local use of EGCG can facilitate tibial fracture healing. Fifty-six 4-month-old rats were randomly assigned to two groups after being weight-matched: a control group with vehicle treatment (Ctrl) and a study group with 10 µmol/L, 40 µL, EGCG treatment (EGCG). Two days after the operation, the rats were treated daily with EGCG or vehicle by percutaneous local injection for 2 weeks. The application of EGCG enhanced callus formation by increasing the bone volume and subsequently improved the mechanical properties of the tibial bone, including the maximal load, break load, stiffness, and Young’s modulus. The results of the histology and BMP-2 immunohistochemistry staining showed that EGCG treatment accelerated the bone matrix formation and produced a stronger expression of BMP-2. Taken together, this study for the first time demonstrated that local treatment of EGCG can accelerate the fracture healing process at least partly via BMP-2.

Analysis of β-lactoglobulin–epigallocatechin gallate interactions: the antioxidant capacity and effects of polyphenols under different heating conditions in polyphenolic–protein interactions

A β-Lg-EGCG covalent conjugate is formed by linking the amino group of a lysine residue and EGCG; the antioxidant capacity of EGCG induced by β-Lg–EGCG covalent conjugates causes a significant decrease.

(-)-Epigallocatechin-3-Gallate Decreases Osteoclastogenesis via Modulation of RANKL and Osteoprotegrin

Osteoporosis is the second most common epidemiologic disease in the aging population worldwide. Previous studies have found that frequent tea drinkers have higher bone mineral density and less hip fracture. We previously found that (-)-epigallocatechin gallate (EGCG) (20⁻100 µmol/L) significantly suppressed receptor activator of nuclear factor-kB ligand (RANKL)-induced osteoclastogenesis and pit formation via inhibiting NF-κB transcriptional activity and nuclear transport of NF-κB in RAW 264.7 cells and murine primary bone marrow macrophage cells. The most important regulation in osteoclastogenesis is the receptor activator of nuclear factor-kB/RANKL/osteoprotegrin (RANK/RANKL/OPG) pathway. In this study, we used the coculture of RAW 264.7 cells and the feeder cells, ST2, to evaluate how EGCG regulated the RANK/RANKL/OPG pathway in RAW 264.7 cells and ST2 cells. We found EGCG decreased the RANKL/OPG ratio in both mRNA expression and secretory protein levels and eventually decreased osteoclastogenesis by TRAP (+) stain osteoclasts and TRAP activity at low concentrations-1 and 10 µmol/L-via the RANK/RANKL/OPG pathway. The effective concentration can be easily achieved in daily tea consumption. Taken together, our results implicate that EGCG could be an important nutrient in modulating bone resorption.

Natural Products as Potential Bone Therapies

Demands for natural products, in the form of botanicals, dietary supplements, and herbal medicine, for management of chronic diseases are increasing globally. Natural products might be an alternative for the management of bone health to meet the demands of a growing aging population. Different types of natural products, including Chinese herbal medicine decoctions, herbs, and isolated phytochemicals, have been demonstrated to exert bone protective effects. The most common types of bone protective bioactives are flavonoids, stilbene, triterpenoids, coumestans, lignans, and phenolic acid. The actions of natural products can be mediated by acting systemically on the hormonal axis or locally via their direct or indirect effects on osteogenesis, osteoclastogenesis, as well as adipogenesis. Furthermore, with the use of metabolomic and microbiome approaches to understand the actions of natural products, novel mechanisms that involve gut-brain-bone axis are also revealed. These studies provide evidence to support the use of natural products as bone therapeutics as well as identify new biological targets for novel drug development.

(-)-Epigallocatechin-3-Gallate (EGCG) Enhances Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

Osteoporosis is the second most-prevalent epidemiologic disease in the aging population worldwide. Cross-sectional and retrospective evidence indicates that tea consumption can mitigate bone loss and reduce risk of osteoporotic fractures. Tea polyphenols enhance osteoblastogenesis and suppress osteoclastogenesis in vitro. Previously, we showed that (-)-epigallocatechin-3-gallate (EGCG), one of the green tea polyphenols, increased osteogenic differentiation of murine bone marrow mesenchymal stem cells (BMSCs) by increasing the mRNA expression of osteogenesis-related genes, alkaline phosphatase activity and, eventually, mineralization. We also found that EGCG could mitigate bone loss and improve bone microarchitecture in ovariectomy-induced osteopenic rats, as well as enhancing bone defect healing partially via bone morphogenetic protein 2 (BMP2). The present study investigated the effects of EGCG in human BMSCs. We found that EGCG, at concentrations of both 1 and 10 µmol/L, can increase mRNA expression of BMP2, Runx2, alkaline phosphatase (ALP), osteonectin and osteocalcin 48 h after treatment. EGCG increased ALP activity both 7 and 14 days after treatment. Furthermore, EGCG can also enhance mineralization two weeks after treatment. EGCG without antioxidants also can enhance mineralization. In conclusion, EGCG can increase mRNA expression of BMP2 and subsequent osteogenic-related genes including Runx2, ALP, osteonectin and osteocalcin. EGCG further increased ALP activity and mineralization. Loss of antioxidant activity can still enhance mineralization of human BMSCs (hBMSCs).