Semaphorin 3A delivered by a rapidly polymerizing click hydrogel overcomes impaired implant osseointegration in a rat type 2 diabetes model

Effect of type 2 diabetes mellitus microenvironment on osteogenic capacity of bone marrow mesenchymal stem cells

Type 2 diabetes mellitus (T2DM) often leads to delayed bone regeneration such as slow healing of fractures and bone defects. The number, status and osteogenic differentiation capacity of bone marrow mesenchymal stem cells (BMSCs) are extremely important in bone healing and bone regeneration. The T2DM microenvironment can have irreversible negative effects on BMSCs. In this paper, we review the molecular expression and altered proliferation, migration, and osteogenic differentiation capacity of BMSCs in the microenvironment of T2DM, it provides a new perspective to restore the normal function of T2DM-BMSCs, so as to save the damaged bone regeneration capacity.

The role of semaphorin 3A in the pathogenesis and progression of Alzheimer's disease and other aging-related diseases: A comprehensive review

Aging serves as a pivotal factor in the etiology of numerous diseases, such as Alzheimer's disease (AD), Parkinson's disease, diabetes, osteoarthritis, atherosclerosis and aging-related macular degeneration. Notably, these diseases often interact with AD through various pathways, facilitating the onset or progression of one another. Semaphorin 3 A (Sema3A), a protein that is essential for axonal guidance during neural development, has recently been identified as a novel regulator in the pathogenesis and progression of multiple aging-related diseases. This article provides a comprehensive review of the expression patterns and mechanisms of action of Sema3A in these diseases. Specifically, Sema3A influences the occurrence and development of aging-related diseases by participating in oxidative stress, inflammatory responses, apoptosis, and synaptic plasticity. Therefore, therapeutic strategies targeting Sema3A present promising avenues for delaying the progression of aging-related diseases and offer novel insights and strategies for their treatment.

Bioactive hydrogel formulations for regeneration of pathological bone defects

Bone defects caused by osteoporosis, infection, diabetes, post-tumor resection, and nonunion often cause severe pain and markedly increase morbidity and mortality, which remain a significant challenge for orthopedic surgeons. The precise local treatments for these pathological complications are essential to avoid poor or failed bone repair. Hydrogel formulations serve as injectable innovative platforms that overcome microenvironmental obstacles and as delivery systems for controlled release of various bioactive substances to bone defects in a targeted manner. Additionally, hydrogel formulations can be tailored for specific mechanical strengths and degradation profiles by adjusting their physical and chemical properties, which are crucial for prolonged drug retention and effective bone repair. This review summarizes recent advances in bioactive hydrogel formulations as three-dimensional scaffolds that support cell proliferation and differentiation. It also highlights their role as smart drug-delivery systems with capable of continuously releasing antibacterial agents, anti-inflammatory drugs, chemotherapeutic agents, and osteogenesis-related factors to enhance bone regeneration in pathological areas. Furthermore, the limitations of hydrogel formulations in pathological bone repair are discussed, and future development directions are proposed, which is expected to pave the way for the repair of pathological bone defects.

ZDHHC9-Mediated PKG1 Affects Osteogenesis by Regulating MAMs in T2DM

Palmitoylation is recognized as a prevalent posttranslational modification of proteins, which is highlighted in recent studies as a key player in regulating protein stability, subcellular localization, membrane transport, and other cellular biological processes. However, its role in peri-implant osteogenesis under type 2 diabetes mellitus (T2DM) remains unclear. During this study, the in vitro high-glucose model based on MC3T3-E1 cells demonstrated that a high-glucose environment in vitro markedly inhibited osteoblasts proliferation and osteogenesis; meanwhile, ZDHHC9 emerged as a significantly upregulated protein. Then, Zdhhc9 knockdown improved the dysfunction of osteoblasts and peri-implant osteogenesis of T2DM mice. In addition, co-immunoprecipitation and fluorescence co-localization analysis revealed an interaction between ZDHHC9 and cyclic guanosine monophosphate (GMP)-dependent protein kinase G 1 (PKG1), and silencing of Prkg1 prevented the improvement in osteoblasts with Zdhhc9 knockdown. Furthermore, we verified that Zdhhc9 knockdown and Prkg1 silencing altered the distance between the endoplasmic reticulum and mitochondria and the expression of mitochondria-associated endoplasmic reticulum membranes (MAMs)-related proteins in osteoblasts. Collectively, our data show that ZDHHC9 could regulate MAMs through palmitoylation of PKG1 to induce osteoblast dysfunction in T2DM. ZDHHC9 might become a novel therapeutic target for peri-implant osteogenesis in diabetes patients.

Strategies for promoting neurovascularization in bone regeneration

Bone tissue relies on the intricate interplay between blood vessels and nerve fibers, both are essential for many physiological and pathological processes of the skeletal system. Blood vessels provide the necessary oxygen and nutrients to nerve and bone tissues, and remove metabolic waste. Concomitantly, nerve fibers precede blood vessels during growth, promote vascularization, and influence bone cells by secreting neurotransmitters to stimulate osteogenesis. Despite the critical roles of both components, current biomaterials generally focus on enhancing intraosseous blood vessel repair, while often neglecting the contribution of nerves. Understanding the distribution and main functions of blood vessels and nerve fibers in bone is crucial for developing effective biomaterials for bone tissue engineering. This review first explores the anatomy of intraosseous blood vessels and nerve fibers, highlighting their vital roles in bone embryonic development, metabolism, and repair. It covers innovative bone regeneration strategies directed at accelerating the intrabony neurovascular system over the past 10 years. The issues covered included material properties (stiffness, surface topography, pore structures, conductivity, and piezoelectricity) and acellular biological factors [neurotrophins, peptides, ribonucleic acids (RNAs), inorganic ions, and exosomes]. Major challenges encountered by neurovascularized materials during their clinical translation have also been highlighted. Furthermore, the review discusses future research directions and potential developments aimed at producing bone repair materials that more accurately mimic the natural healing processes of bone tissue. This review will serve as a valuable reference for researchers and clinicians in developing novel neurovascularized biomaterials and accelerating their translation into clinical practice. By bridging the gap between experimental research and practical application, these advancements have the potential to transform the treatment of bone defects and significantly improve the quality of life for patients with bone-related conditions.

Properties and antibacterial effectiveness of metal-ion doped borate-based bioactive glasses

Bioactive glasses (BGs) are physiologically reactive surface biomaterials widely used in biomedical applications and various treatments. Borate bioactive glasses (BBGs) are third-generation BGs, and they exhibit superior biodegradable, bioactive, osteoconductive, antibacterial, and biocompatible properties compared to other types of BGs. Certain concentrations of dopant ions can be incorporated into the chemical structure of BBGs to enhance their biological functionalities and antimicrobial properties. It was demonstrated that those ions play a crucial role in the biological responsiveness in vitro and in vivo once in contact with a physiological environment. The dissolution products of ion-doped BBGs were noted in their ability to stimulate gene expression related to cell differentiation and proliferation, promote angiogenesis, display anti-inflammatory effects, and inhibit bacterial growth within a few hours. Thus, metal-ion-doped BBGs address several limitations encountered by biomedical, tissue engineering, and infection control applications. Considering the research studies on BBGs to date, this review aims to analyze metal-ion-doped BBGs based on their primary antibacterial properties and effectiveness.

Semaphorin 3A on Osteoporosis: An Overreview of the Literature

Semaphorin 3A (Sema3A) is a signaling protein that has attracted increasing attention in recent years for its important role in regulating bone metabolism. In this review, we searched different databases with various combinations of keywords to analyze the effects of Sema3A on osteoporosis. Sema3A promotes bone formation and inhibits bone resorption by directly affecting the osteoblast and osteoclast or indirectly targeting the nervous system. The sympathetic nervous system may be the main link between the central nervous system and bone metabolism for Sema3A. In the peripheral nervous system, Sema3A may improve bone quality via sensory nervous innervation. In addition, estrogen is found to regulate Sema3A levels to improve bone homeostasis. Lots of Sema3A agonists have been documented to exhibit anti-osteoporotic potential in preclinical investigations. Therefore, Sema3A can be considered a novel therapeutic target for preserving bone mass, highlighting an alternative strategy for the development of anti-osteoporosis drugs.

Non-Canonical Wnt16 and microRNA-145 Mediate the Response of Human Bone Marrow Stromal Cells to Additively Manufactured Porous 3-Dimensional Biomimetic Titanium-Aluminum-Vanadium Constructs

Metal 3D printing is increasingly being used to manufacture titanium-aluminum-vanadium (Ti6Al4V) implants. In vitro studies using 2D substrates demonstrate that the osteoblastic differentiation of bone marrow stromal cells (MSCs) on Ti6Al4V surfaces, with a microscale/nanoscale surface topography that mimics an osteoclast resorption pit, involves non-canonical Wnt signaling; Wnt3a is downregulated and Wnt5a is upregulated, leading to the local production of BMP2 and semaphorin 3A (sema3A). In this study, it was examined whether the regulation of MSCs in a 3D environment occurs by a similar mechanism. Human MSCs from two different donors were cultured for 7, 14, or 21 days on porous (3D) or solid (2D) constructs fabricated by powder-bed laser fusion. mRNA and secretion of osteoblast markers, as well as factors that enhance peri-implant osteogenesis, were analyzed, with a primary focus on the Wnt family, sema3A, and microRNA-145 (miR-145) signaling pathways. MSCs exhibited greater production of osteocalcin, latent and active TGFβ1, sema3A, and Wnt16 on the 3D constructs compared to 2D, both of which had similar microscale/nanoscale surface modifications. Wnt3a was reduced on 2D constructs as a function of time; Wnt11 and Wnt5a remained elevated in the 3D and 2D cultures. To better understand the role of Wnt16, cultures were treated with rhWnt16; endogenous Wnt16 was blocked using an antibody. Wnt16 promoted proliferation and inhibited osteoblast differentiation, potentially by reducing production of BMP2 and BMP4. Wnt16 expression was reduced by exogenous Wnt16 in 3D cells. Addition of the anti-Wnt16 antibody to the cultures reversed the effects of exogenous Wnt16, indicating an autocrine mechanism. Wnt16 increased miR-145-5p, suggesting a potential feedback mechanism. The miR-145-5p mimic increased Wnt16 production and inhibited sema3A in a 3D porous substrate-specific manner. Wnt16 did not affect sema3A production, but it was reduced by miR-145-5p mimic on the 3D constructs and stimulated by miR-145-5p inhibitor. Media from 7-, 14-, and 21-day cultures of MSCs grown on 3D constructs inhibited osteoclast activity to a greater extent than media from the 2D cultures. The findings present a significant step towards understanding the complex molecular interplay that occurs in 3D Ti6Al4V constructs fabricated by additive manufacturing. In addition to enhancing osteogenesis, the 3D porous biomimetic structure inhibits osteoclast activities, indicating its role in modulating bone remodeling processes. Our data suggest that the pathway mediated by sema3A/Wnt16/miR145-5p was enhanced by the 3D surface and contributes to bone regeneration in the 3D implants. This comprehensive exploration contributes valuable insights to guide future strategies in implant design, customization, and ultimately aims at improving clinical outcomes and successful osseointegration.

Bone Marrow Stromal Cells Generate a Pro-Healing Inflammasome When Cultured on Titanium-Aluminum-Vanadium Surfaces with Microscale/Nanoscale Structural Features

The surface topography and chemistry of titanium-aluminum-vanadium (Ti6Al4V) implants play critical roles in the osteoblast differentiation of human bone marrow stromal cells (MSCs) and the creation of an osteogenic microenvironment. To assess the effects of a microscale/nanoscale (MN) topography, this study compared the effects of MN-modified, anodized, and smooth Ti6Al4V surfaces on MSC response, and for the first time, directly contrasted MN-induced osteoblast differentiation with culture on tissue culture polystyrene (TCPS) in osteogenic medium (OM). Surface characterization revealed distinct differences in microroughness, composition, and topography among the Ti6Al4V substrates. MSCs on MN surfaces exhibited enhanced osteoblastic differentiation, evidenced by increased expression of RUNX2, SP7, BGLAP, BMP2, and BMPR1A (fold increases: 3.2, 1.8, 1.4, 1.3, and 1.2). The MN surface also induced a pro-healing inflammasome with upregulation of anti-inflammatory mediators (170-200% increase) and downregulation of pro-inflammatory factors (40-82% reduction). Integrin expression shifted towards osteoblast-associated integrins on MN surfaces. RNA-seq analysis revealed distinct gene expression profiles between MSCs on MN surfaces and those in OM, with only 199 shared genes out of over 1000 differentially expressed genes. Pathway analysis showed that MN surfaces promoted bone formation, maturation, and remodeling through non-canonical Wnt signaling, while OM stimulated endochondral bone development and mineralization via canonical Wnt3a signaling. These findings highlight the importance of Ti6Al4V surface properties in directing MSC differentiation and indicate that MN-modified surfaces act via signaling pathways that differ from OM culture methods, more accurately mimicking peri-implant osteogenesis in vivo.

Reduced osseointegration in disuse and denervation rat models results from impaired cellular responses to multiscale microstructured titanium surfaces

Immobilization-induced skeletal unloading results in muscle atrophy and rapid bone loss, thereby increasing the risk of falling and the need for implant therapy in patients with extended bed rest or neuromuscular injuries. Skeletal unloading causes bone loss by altering bone growth and resorption, suggesting that implant performance might be affected. To test this, we focused on early events in implant osseointegration. We used the rat sciatic neurectomy-induced disuse model under two different settings. In Study 1, 16 Sprague Dawley rats (SD) were separated into control, sham operated+cast immobilization, and sciatic neurectomy+casting groups; titanium implants with multiscale microtextured topography and hydrophilic chemistry (modSLA) were inserted in the distal femoral metaphysis. Neurectomy surgeries and casting were performed at the same surgical setting as implant placement; rats were euthanized 4 weeks post-implantation. In Study 2, we established the unloaded condition before implantation. A total of 12 SD rats were divided into control and sciatic+femoral neurectomy groups. A total of 24 days after sciatic and femoral neurectomy surgery, rats received implants. Study 2 rats were euthanized at 4 weeks post-implantation. MicroCT and histomorphometry showed that trabecular bone and osseointegration were reduced when disuse was established before implantation. Osteoblasts isolated from Study 1 sciatic neurectomy tibial bones exhibited impaired differentiation on modSLA culture disks, revealing a possible mechanism responsible for the decreased osseointegration observed in the Study 2 rats. This study addressed the importance of considering the mechanical unloading and muscle function history before implant insertion and suggests that implant performance was reduced due to poor cellular ability to regenerate.

Strategies for Improving Impaired Osseointegration in Compromised Animal Models

Implant osseointegration is reduced in patients with systemic conditions that compromise bone quality, such as osteoporosis, disuse syndrome, and type 2 diabetes. Studies using rodent models designed to mimic these compromised conditions demonstrated reduced bone-to-implant contact (BIC) or a decline in bone mineral density. These adverse effects are a consequence of disrupted intercellular communication. A variety of approaches have been developed to compensate for the altered microenvironment inherent in compromised conditions, including the use of biologics and implant surface modification. Chemical and physical modification of surface properties at the microscale, mesoscale, and nanoscale levels to closely resemble the surface topography of osteoclast resorption pits found in bone has proven to be a highly effective strategy for improving implant osseointegration. The addition of hydrophilicity to the surface further enhances osteoblast response at the bone-implant interface. These surface modifications, applied either alone or in combination, improve osseointegration by increasing proliferation and osteoblastic differentiation of osteoprogenitor cells and enhancing angiogenesis while modulating osteoclast activity to achieve net new bone formation, although the specific effects vary with surface treatment. In addition to direct effects on surface-attached cells, the communication between bone marrow stromal cells and immunomodulatory cells is sensitive to these surface properties. This article reports on the advances in titanium surface modifications, alone and in combination with novel therapeutics in animal models of human disease affecting bone quality. It offers clinically translatable perspectives for clinicians to consider when using different surface modification strategies to improve long-term implant performance in compromised patients. This review supports the use of surface modifications, bioactive coatings, and localized therapeutics as pragmatic approaches to improve BIC and enhance osteogenic activity from both structural and molecular standpoints.

SiJunZi decoction ameliorates bone quality and redox homeostasis and regulates advanced glycation end products/receptor for advanced glycation end products and WNT/β-catenin signaling pathways in diabetic mice

ETHNOPHARMACOLOGICAL RELEVANCE

SiJunZi decoction (SJZD), one of the traditional Chinese medicine formulas, has been clinically and traditionally used to improve glucose and lipid metabolism and promote bone remodeling.

AIM OF THE STUDY

To study the actions and mechanisms of SJZD on bone remodeling in a type 2 diabetes mouse model.

MATERIALS AND METHODS

Diabetic mice generated with a high-fat diet (HFD) and streptozotocin (STZ) were subjected to SJZD treatment for 8 weeks. Blood glucose and lipid profile, redox status and bone metabolism were determined by ELISA or biochemical assays. Bone quality was evaluated by micro-CT, three-point bending assay and Fourier transform infrared spectrum (FTIR). Bone histomorphometry alterations were evaluated by Hematoxylin-Eosin (H&E), tartrate resistant acid phosphatase (TRAP) staining and Safranin O-fast green staining. The expressions of superoxide dismutase 1 (SOD1), advanced glycation end products (AGEs), receptor for advanced glycosylation end products (RAGE), phosphorylated nuclear factor kappa-B (p-NF-κB), NF-κB, cathepsin K, semaphorin 3A (Sema3A), insulin-like growth factor 1 (IGF1), p-GSK-3β, (p)-β-catenin, Runt-related transcription factor 2 (Runx2) and Cyclin D1 in the femurs and/or tibias were examined by Western blot or immunohistochemical staining. The main constituents in the SJZD aqueous extract were characterized by a HPLC/MS.

RESULTS

SJZD intervention improved glucose and lipid metabolism and preserved bone quality in the diabetic mice, in particular glucose tolerance, lipid profile, bone microarchitecture, strength and material composition. SJZD administration to diabetic mice preserved redox homeostasis in serum and bone marrow, and prevented an increase in AGEs, RAGE, p-NF-κB/NF-κB, cathepsin K, p-GSK-3β, p-β-catenin expressions and a decrease in Sema3A, IGF1, β-catenin, Runx2 and Cyclin D1 expressions in tibias and/or femurs. Thirteen compounds were identified in SJZD aqueous extract, including astilbin, liquiritin apioside, ononin, ginsenoside Re, Rg1, Rb1, Rb2, Ro, Rb3, Rd, notoginsenoside R2, glycyrrhizic acid, and licoricesaponin B2.

CONCLUSIONS

SJZD ameliorates bone quality in diabetic mice possibly via maintaining redox homeostasis. The mechanism governing these alterations are possibly related to effects on the AGEs/RAGE and Wnt/β-catenin signaling pathways. SJZD may offer a novel source of drug candidates for the prevention and treatment of type 2 diabetes and osteoporosis.

Progress in Surface Modification of Titanium Implants by Hydrogel Coatings

Although titanium and titanium alloys have become the preferred materials for various medical implants, surface modification technology still needs to be strengthened in order to adapt to the complex physiological environment of the human body. Compared with physical or chemical modification methods, biochemical modification, such as the introduction of functional hydrogel coating on implants, can fix biomolecules such as proteins, peptides, growth factors, polysaccharides, or nucleotides on the surface of the implants, so that they can directly participate in biological processes; regulate cell adhesion, proliferation, migration, and differentiation; and improve the biological activity on the surface of the implants. This review begins with a look at common substrate materials for hydrogel coatings on implant surfaces, including natural polymers such as collagen, gelatin, chitosan, and alginate, and synthetic materials such as polyvinyl alcohol, polyacrylamide, polyethylene glycol, and polyacrylic acid. Then, the common construction methods of hydrogel coating (electrochemical method, sol-gel method and layer-by-layer self-assembly method) are introduced. Finally, five aspects of the enhancement effect of hydrogel coating on the surface bioactivity of titanium and titanium alloy implants are described: osseointegration, angiogenesis, macrophage polarization, antibacterial effects, and drug delivery. In this paper, we also summarize the latest research progress and point out the future research direction. After searching, no previous relevant literature reporting this information was found.

Osseointegration of Titanium Implants in a Botox-Induced Muscle Paralysis Rat Model Is Sensitive to Surface Topography and Semaphorin 3A Treatment

Reduced skeletal loading associated with many conditions, such as neuromuscular injuries, can lead to bone fragility and may threaten the success of implant therapy. Our group has developed a botulinum toxin A (botox) injection model to imitate disease-reduced skeletal loading and reported that botox dramatically impaired the bone formation and osseointegration of titanium implants. Semaphorin 3A (sema3A) is an osteoprotective factor that increases bone formation and inhibits bone resorption, indicating its potential therapeutic role in improving osseointegration in vivo. We first evaluated the sema3A effect on whole bone morphology following botox injections by delivering sema3A via injection. We then evaluated the sema3A effect on the osseointegration of titanium implants with two different surface topographies by delivering sema3A to cortical bone defect sites prepared for implant insertion and above the implants after insertion using a copper-free click hydrogel that polymerizes rapidly in situ. Implants had hydrophobic smooth surfaces (PT) or multiscale biomimetic micro/nano topography (SLAnano). Sema3A rescued the botox-impaired bone formation. Furthermore, biomimetic Ti implants improved the bone-to-implant contact (BIC) and mechanical properties of the integrated bone in the botox-treated rats, which sema3A enhanced. This study demonstrated the value of biomimetic approaches combining multiscale topography and biologics in improving the clinical outcomes of implant therapy.