Pro-inflammatory M1 macrophages promote Osteogenesis by mesenchymal stem cells via the COX-2-prostaglandin E2 pathway

Isolation and adipogenic differentiation of murine mesenchymal stem cells harvested from macrophage-depleted bone marrow and adipose tissue

INTRODUCTION AND PURPOSE

Mouse mesenchymal stem cells (MSCs) provide a resourceful tool to study physiological and pathological aspects of adipogenesis. Bone marrow-derived MSCs (BM-MSCs) and adipose tissue-derived MSCs (ASCs) are widely used for these studies. Since there is a wide spectrum of methods available, the purpose is to provide a focused hands-on procedural guide for isolation and characterization of murine BM-MSCs and ASCs and to effectively differentiate them into adipocytes.

METHODS AND RESULTS

Optimized harvesting procedures for murine BM-MSCs and ASCs are described and graphically documented. Since macrophages reside in bone-marrow and fat tissues and regulate the biological behaviour of BM-MSCs and ASCs, we included a procedure to deplete macrophages from the MSC preparations. The identity and stemness of BM-MSCs and ASCs were confirmed by flow cytometry using established markers. Since the composition and concentrations of adipogenic differentiation cocktails differ widely, we present a standardized four-component adipogenic cocktail, consisting of insulin, dexamethasone, 3-isobutyl-1-methylxanthine, and indomethacin to efficiently differentiate freshly isolated or frozen/thawed BM-MSCs and ASCs into adipocytes. We further included visualization and quantification protocols of the differentiated adipocytes.

CONCLUSION

This laboratory protocol was designed as a step-by-step procedure for harvesting murine BM-MSCs and ASCs and differentiating them into adipocytes.

The interactions of macrophages, lymphocytes, and mesenchymal stem cells during bone regeneration

Bone regeneration and repair are crucial to ambulation and quality of life. Factors such as poor general health, serious medical comorbidities, chronic inflammation, and ageing can lead to delayed healing and nonunion of fractures, and persistent bone defects. Bioengineering strategies to heal bone often involve grafting of autologous bone marrow aspirate concentrate (BMAC) or mesenchymal stem cells (MSCs) with biocompatible scaffolds. While BMAC shows promise, variability in its efficacy exists due to discrepancies in MSC concentration and robustness, and immune cell composition. Understanding the mechanisms by which macrophages and lymphocytes - the main cellular components in BMAC - interact with MSCs could suggest novel strategies to enhance bone healing. Macrophages are polarized into pro-inflammatory (M1) or anti-inflammatory (M2) phenotypes, and influence cell metabolism and tissue regeneration via the secretion of cytokines and other factors. T cells, especially helper T1 (Th1) and Th17, promote inflammation and osteoclastogenesis, whereas Th2 and regulatory T (Treg) cells have anti-inflammatory pro-reconstructive effects, thereby supporting osteogenesis. Crosstalk among macrophages, T cells, and MSCs affects the bone microenvironment and regulates the local immune response. Manipulating the proportion and interactions of these cells presents an opportunity to alter the local regenerative capacity of bone, which potentially could enhance clinical outcomes.

A 4D printed nanoengineered super bioactive hydrogel scaffold with programmable deformation for potential bifurcated vascular channel construction

Four-dimensional (4D) printing of hydrogels enabled the fabrication of complex scaffold geometries out of static parts. Although current 4D fabrication strategies are promising for creating vascular parts such as tubes, developing branched networks or tubular junctions is still challenging. Here, for the first time, a 4D printing approach is employed to fabricate T-shaped perfusable bifurcation using an extrusion-based multi-material 3D printing process. An alginate/methylcellulose-based dual-component hydrogel system (with defined swelling behavior) is nanoengineered with carbonized alginate (∼100 nm) to introduce anti-oxidative, anti-inflammatory, and anti-thrombotic properties and shape-shifting properties. A computational model to predict shape deformations in the printed hydrogels with defined infill angles was designed and further validated experimentally. Shape deformations of the 3D-printed flat sheets were achieved by ionic cross-linking. An undisrupted perfusion of a dye solution through a T-junction with minimal leakage mimicking blood flow through vessels is also demonstrated. Moreover, human umbilical vein endothelial and fibroblast cells seeded with printed constructs show intact morphology and excellent cell viability. Overall, the developed strategy paves the way for manufacturing self-actuated vascular bifurcations with remarkable anti-thrombotic properties to potentially treat coronary artery diseases.

Induction of osteoblast apoptosis stimulates macrophage efferocytosis and paradoxical bone formation

Apoptosis is crucial for tissue homeostasis and organ development. In bone, apoptosis is recognized to be a main fate of osteoblasts, yet the relevance of this process remains underexplored. Using our murine model with inducible Caspase 9, the enzyme that initiates intrinsic apoptosis, we triggered apoptosis in a proportion of mature osteocalcin (OCN+) osteoblasts and investigated the impact on postnatal bone development. Osteoblast apoptosis stimulated efferocytosis by osteal macrophages. A five-week stimulation of OCN+ osteoblast apoptosis in 3-week-old male and female mice significantly enhanced vertebral bone formation while increasing osteoblast precursors. A similar treatment regimen to stimulate osterix+ cell apoptosis had no impact on bone volume or density. The vertebral bone accrual following stimulation of OCN+ osteoblast apoptosis did not translate in improved mechanical strength due to disruption of the lacunocanalicular network. The observed bone phenotype was not influenced by changes in osteoclasts but was associated with stimulation of macrophage efferocytosis and vasculature formation. Phenotyping of efferocytic macrophages revealed a unique transcriptomic signature and expression of factors including VEGFA. To examine whether macrophages participated in the osteoblast precursor increase following osteoblast apoptosis, macrophage depletion models were employed. Depletion of macrophages via clodronate-liposomes and the CD169-diphtheria toxin receptor mouse model resulted in marked reduction in leptin receptor+ and osterix+ osteoblast precursors. Collectively, this work demonstrates the significance of osteoblast turnover via apoptosis and efferocytosis in postnatal bone formation. Importantly, it exposes the potential of targeting this mechanism to promote bone anabolism in the clinical setting.

Friend or foe? Inflammation and the foreign body response to orthopedic biomaterials

The use of biomaterials and implants for joint replacement, fracture fixation, spinal stabilization and other orthopedic indications has revolutionized patient care by reliably decreasing pain and improving function. These surgical procedures always invoke an acute inflammatory reaction initially, that in most cases, readily subsides. Occasionally, chronic inflammation around the implant develops and persists; this results in unremitting pain and compromises function. The etiology of chronic inflammation may be specific, such as with infection, or be unknown. The histological hallmarks of chronic inflammation include activated macrophages, fibroblasts, T cell subsets, and other cells of the innate immune system. The presence of cells of the adaptive immune system usually indicates allergic reactions to metallic haptens. A foreign body reaction is composed of activated macrophages, giant cells, fibroblasts, and other cells often distributed in a characteristic histological arrangement; this reaction is usually due to particulate debris and other byproducts from the biomaterials used in the implant. Both chronic inflammation and the foreign body response have adverse biological effects on the integration of the implant with the surrounding tissues. Strategies to mitigate chronic inflammation and the foreign body response will enhance the initial incorporation and longevity of the implant, and thereby, improve long-term pain relief and overall function for the patient. The seminal research performed in the laboratory of Dr. James Anderson and co-workers has provided an inspirational and driving force for our laboratory's work on the interactions and crosstalk among cells of the mesenchymal, immune, and vascular lineages, and orthopedic biomaterials. Dr. Anderson's delineation of the fundamental biologic processes and mechanisms underlying acute and chronic inflammation, the foreign body response, resolution, and eventual functional integration of implants in different organ systems has provided researchers with a strategic approach to the use of biomaterials to improve health in numerous clinical scenarios.

Macrophages modulate mesenchymal stem cell function via tumor necrosis factor alpha in tooth extraction model

Mesenchymal stem cells (MSCs) and macrophages collaboratively contribute to bone regeneration after injury. However, detailed mechanisms underlying the interaction between MSCs and inflammatory macrophages (M1) remain unclear. A macrophage-depleted tooth extraction model was generated in 5-wk-old female C57BL/6J mice using clodronate liposome (12.5 mg/kg/mouse, intraperitoneally) or saline injection (control) before maxillary first molar extraction. Mice were sacrificed on days 1, 3, 5, 7, and 10 after tooth extraction (n = 4). Regenerated bone volume evaluation of tooth extraction socket (TES) and histochemical analysis of CD80+M1, CD206+M2 (anti-inflammatory macrophages), PDGFRα+MSC, and TNF-α+ cells were performed. In vitro, isolated MSCs with or without TNF-α stimulation (10 ng/mL, 24 h, n = 3) were bulk RNA-sequenced (RNA-Seq) to identify TNF-α stimulation-specific MSC transcriptomes. Day 7 micro-CT and HE staining revealed significantly lower mean bone volume (clodronate vs control: 0.01 mm3 vs 0.02 mm3, p<.0001) and mean percentage of regenerated bone area per total TES in clodronate group (41.97% vs 54.03%, p<.0001). Clodronate group showed significant reduction in mean number of CD80+, TNF-α+, PDGFRα+, and CD80+TNF-α+ cells on day 5 (306.5 vs 558.8, p<.0001; 280.5 vs 543.8, p<.0001; 365.0 vs 633.0, p<.0001, 29.0 vs 42.5, p<.0001), while these cells recovered significantly on day 7 (493.3 vs 396.0, p=.0004; 479.3 vs 384.5, p=.0008; 593.0 vs 473.0, p=.0010, 41.0 vs 32.5, p=.0003). RNA-Seq analysis showed that 15 genes (|log2FC| > 5.0, log2TPM > 5) after TNF-α stimulation were candidates for regulating MSC's immunomodulatory capacity. In vivo, Clec4e and Gbp6 are involved in inflammation and bone formation. Clec4e, Gbp6, and Cxcl10 knockdown increased osteogenic differentiation of MSCs in vitro. Temporal reduction followed by apparent recovery of TNF-α-producing M1 macrophages and MSCs after temporal macrophage depletion suggests that TNF-α activated MSCs during TES healing. In vitro mimicking the effect of TNF-α on MSCs indicated that there are 15 candidate MSC genes for regulation of immunomodulatory capacity.

Oncostatin M promotes osteogenic differentiation of tendon-derived stem cells through the JAK2/STAT3 signalling pathway

PURPOSE

Oncostatin M (OSM) is involved in the regulation of osteogenic differentiation and has a major role in the development of heterotopic ossification. The role of OSM in osteogenic differentiation of tendon-derived stem cells (TDSCs) and its mechanism have not been reported. This study aim to investigate the role of OSM in osteogenic differentiation of TDSCs and study the mechanism.

METHODS

TDSCs were differentiated in osteogenic differentiation medium for 7 days. Recombinant OSM was added to the osteogenic differentiation medium for 7 and 14 days. The effect of Janus kinase 2 (JAK2) inhibitor AZD1480 and signal transducer and activator of transcription 3 (STAT3) inhibitor stattic in the presence of recombinant OSM on osteogenic differentiation of TDSCs was examined after differentiation for 7 and 14 days. Alkaline phosphatase and alizarin red staining were used to assess the effects on early and mid-stage osteogenic differentiation, respectively. Western blotting and qPCR were used to assess the expression of receptor and signalling pathway-related proteins and osteogenic marker genes, respectively.

RESULTS

TDSCs were successfully induced to differentiate into osteoblasts. Recombinant OSM promoted osteogenic differentiation of TDSCs to early and mid-stages. After addition of AZD1480 or stattic, decreased alkaline phosphatase and alizarin red staining were observed in the early and mid-stages of osteogenic differentiation. Additionally, decreased expression of receptor and pathway-related proteins, and osteogenic genes was found by western blotting and qPCR, respectively.

CONCLUSION

OSM promotes osteogenic differentiation of TDSCs and the JAK2/STAT3 signalling pathway plays an important role.

T cells and macrophages jointly modulate osteogenesis of mesenchymal stromal cells

Approximately 5%-10% of fractures go on to delayed healing and nonunion, posing significant clinical, economic, and social challenges. Current treatment methods involving open bone harvesting and grafting are associated with considerable pain and potential morbidity at the donor site. Hence, there is growing interest in minimally invasive approaches such as bone marrow aspirate concentrate (BMAC), which contains mesenchymal stromal cells (MSCs), macrophages (Mφ), and T cells. However, the use of cultured or activated cells for treatment is not yet FDA-approved in the United States, necessitating further exploration of optimal cell types and proportions for effective bone formation. As our understanding of osteoimmunology advances, it has become apparent that factors from anti-inflammatory Mφ (M2) promote bone formation by MSCs. Additionally, M2 Mφ promote T helper 2 (Th2) cells and Treg cells, both of which enhance bone formation. In this study, we investigated the interactions among MSCs, Mφ, and T cells in bone formation and explored the potential of subsets of BMAC. Coculture experiments were conducted using primary MSCs, Mφ, and CD4+ T cells at specific ratios. Our results indicate that nonactivated T cells had no direct influence on osteogenesis by MSCs, while coculturing MSCs with Mφ and T cells at a ratio of 1:5:10 positively impacted bone formation. Furthermore, higher numbers of T cells led to increased M2 polarization and a higher proportion of Th2 cells in the early stages of coculture. These findings suggest the potential for enhancing bone formation by adjusting immune and mesenchymal cell ratios in BMAC. By understanding the interactions and effects of immune cells on bone formation, we can develop more effective strategies and protocols for treating bone defects and nonunions. Further studies are needed to investigate these interactions in vivo and explore additional factors influencing MSC-based therapies.

Mg-Cross-Linked Alginate Hydrogel Induces BMSC/Macrophage Crosstalk to Enhance Bone Tissue Regeneration via Dual Promotion of the Ligand-Receptor Pairing of the OSM/miR-370-3p-gp130 Signaling Pathway

Macrophages play a pivotal role in the crosstalk between the immune and skeletal systems, while Mg-based biomaterials demonstrate immunomodulatory capabilities in this procedure. However, the mechanism of how Mg2+ promotes osteogenesis through the interplay of bone marrow-derived mesenchymal stem cells (BMSCs) and macrophages remains undescribed. Here, we demonstrated that a Mg-cross-linked alginate hydrogel exerted a dual enhancement of BMSCs osteogenic differentiation through the ligand-receptor pairing of the OSM/miR-370-3p-gp130 axis. On the one hand, Mg2+, released from the Mg-cross-linked hydrogel, stimulates bone marrow-derived macrophages to produce and secrete more OSM. On the other hand, Mg2+ lowers the miR-370-3p level in BMSCs and in turn, reverses its suppression on gp130. Then, the OSM binds to the gp130 heterodimer receptor and activates intracellular osteogenic programs in BMSCs. Taken together, this study reveals a novel cross-talk pattern between the skeletal and immune systems under Mg2+ stimulation. This study not only brings new insights into the immunomodulatory properties of Mg-based biomaterials for orthopedic applications but also enriches the miRNA regulatory network and provides a promising target to facilitate bone regeneration in large bone defects.

Investigation of the impact of planar microelectrodes on macrophage-mediated mesenchymal stem cell osteogenesis

Osseointegration commences with foreign body inflammation upon implant placement, where macrophages play a crucial role in the immune response. Subsequently, during the intermediate and late stages of osseointegration, mesenchymal stem cells (MSCs) migrate and initiate their osteogenic functions, while macrophages support MSCs in osteogenesis. The utilization of ferroelectric P(VDF-TrFE) covered ITO planar microelectrodes facilitated the simulation of various surface charge to investigate their effects on MSCs' osteogenic differentiation and macrophage polarization and the results indicated a parabolic increase in the promotional effect of both with the rise in piezoelectric coefficient. Furthermore, the surface charge with a piezoelectric coefficient of -18 exhibited the strongest influence on the promotion of M1 polarization of macrophages and the promotion of MSCs' osteogenic differentiation. The impact of macrophage polarization and MSC osteogenesis following the interaction of macrophages affected by surface charge and MSC was ultimately investigated. It was observed that macrophages affected by the surface charge of -18 piezoelectric coefficient still exerted the most profound induced osteogenic effect, validating the essential role of M1-type macrophages in the osteogenic differentiation of MSCs.

The Dysregulation of Essential Fatty Acid (EFA) Metabolism May Be a Factor in the Pathogenesis of Sepsis

I propose that a deficiency of essential fatty acids (EFAs) and an alteration in their (EFAs) metabolism could be a major factor in the pathogenesis of sepsis and sepsis-related mortality. The failure of corticosteroids, anti-TNF-α, and anti-interleukin-6 monoclonal antibodies can be attributed to this altered EFA metabolism in sepsis. Vitamin C; folic acid; and vitamin B1, B6, and B12 serve as co-factors necessary for the activity of desaturase enzymes that are the rate-limiting steps in the metabolism of EFAs. The altered metabolism of EFAs results in an imbalance in the production and activities of pro- and anti-inflammatory eicosanoids and cytokines resulting in both hyperimmune and hypoimmune responses seen in sepsis. This implies that restoring the metabolism of EFAs to normal may form a newer therapeutic approach both in the prevention and management of sepsis and other critical illnesses.

Platelets: A Potential Factor that Offers Strategies for Promoting Bone Regeneration

Bone defects represent a prevalent category of clinical injuries, causing significant pain and escalating health care burdens. Effectively addressing bone defects is thus of paramount importance. Platelets, formed from megakaryocyte lysis, have emerged as pivotal players in bone tissue repair, inflammatory responses, and angiogenesis. Their intracellular storage of various growth factors, cytokines, and membrane protein receptors contributes to these crucial functions. This article provides a comprehensive overview of platelets' roles in hematoma structure, inflammatory responses, and angiogenesis throughout the process of fracture healing. Beyond their application in conjunction with artificial bone substitute materials for treating bone defects, we propose the potential future use of anticoagulants such as heparin in combination with these materials to regulate platelet number and function, thereby promoting bone healing. Ultimately, we contemplate whether manipulating platelet function to modulate bone healing could offer innovative ideas and directions for the clinical treatment of bone defects.

DP7-C/mir-26a system promotes bone regeneration by remodeling the osteogenic immune microenvironment

OBJECTIVE

This study investigates the DP7-C/miR-26a complex as a stable entity resulting from the combination of miR-26a with the immunomodulatory peptide DP7-C. Our focus is on utilizing DP7-C loaded with miR-26a to modulate the immune microenvironment in bone and facilitate osteogenesis.

METHODS

The DP7-C/miR-26a complex was characterized through transmission electron microscopy, agarose electrophoresis, and nanoparticle size potentiometer analysis. Transfection efficiency and cytotoxicity of DP7-C were assessed using flow cytometry and the CCK-8 assay. We validated the effects of DP7-C/miR-26a on bone marrow mesenchymal stem cells (BMSCs) and macrophages RAW 264.7 through gene expression and protein synthesis assays. A comprehensive evaluation of appositional bone formation involved micro-CT imaging, histologic analysis, and immunohistochemical staining.

RESULTS

DP7-C/miR-26a, a nanoscale, and low-toxic cationic complex, demonstrated the ability to enter BMSCs and RAW 264.7 via distinct pathways. The treatment with DP7-C/miR-26a significantly increased the synthesis of multiple osteogenesis-related factors in BMSCs, facilitating calcium nodule formation in vitro. Furthermore, DP7-C/miR-26a promoted M1 macrophage polarization toward M2 while suppressing the release of inflammatory factors. Coculture studies corroborated these findings, indicating significant repair of rat skull defects following treatment with DP7-C/miR-26a.

CONCLUSION

The DP7-C/miR-26a system offers a safer, more efficient, and feasible technical means for treating bone defects.

M1 macrophage-derived oncostatin M induces osteogenic differentiation of ligamentum flavum cells through the JAK2/STAT3 pathway

Background

M1 macrophages (Mφs) are involved in osteogenic differentiation of ligamentum flavum (LF) cells and play an important role in heterotopic ossification. However, the mechanism by which M1 Mφs influence osteogenic differentiation of LF cells has not been studied.

Methods

The effect of conditioned medium including secretions of M1 Mφs (CM-M1) on LF cells was analyzed by GeneChip profiling and ingenuity pathway analysis (IPA). THP-1 cells were polarized into M1 Mφs and CM-M1 was used to induce LF cells. In addition, LF cells were induced by CM-M1 in the presence of cyclooxygenase 2 (COX-2) inhibitors or oncostatin M (OSM)-neutralizing antibodies. Based on the presence of OSM, knockout of OSMR or GP130 receptors, or addition of the Janus kinase 2 (JAK2) inhibitor AZD1480 or signal transducer and activator of transcription 3 (STAT3) inhibitor Stattic were examined for effects on osteogenic differentiation of LF cells. OSM secretion was quantified by ELISA, while qPCR and western blot were used to evaluate expression of osteogenic genes and receptor and signaling pathway-related proteins, respectively.

Results

GeneChip and IPA results indicate that the OSM signaling pathway and its downstream signaling molecules JAK2 and STAT3 are significantly activated. ELISA results indicate that OSM is highly expressed in cells treated with CM-M1 and lowly expressed in cells treated with CM-M1 and a COX-2 inhibitor. Besides, CM-M1 induces osteogenic differentiation of LF cells, which is weakened when COX-2 inhibitors or OSM-neutralizing antibody are added to it. Recombinant OSM could induce osteogenic differentiation of LF cells and upregulate expression of OSMR, GP130, phosphorylated (P)-JAK2, and P-STAT3. Upon knockdown of OSMR or GP130, or the addition of AZD1480 or Stattic, P-JAK2 and P-STAT3 expression were decreased and osteogenic differentiation was reduced.

Conclusion

M1 Mφ-derived OSM induces osteogenic differentiation of LF cells and the JAK2/STAT3 signaling pathway plays an important role.

Temporal gene expression profiling during early-stage traumatic temporomandibular joint bony ankylosis in a sheep model

BACKGROUND

Investigating the molecular biology underpinning the early-stage of traumatic temporomandibular joint (TMJ) ankylosis is crucial for discovering new ways to prevent the disease. This study aimed to explore the dynamic changes of transcriptome from the intra-articular hematoma or the newly generated ankylosed callus during the onset and early progression of TMJ ankylosis.

METHODS

Based on a well-established sheep model of TMJ bony ankylosis, the genome-wide microarray data were obtained from samples at postoperative Days 1, 4, 7, 9, 11, 14 and 28, with intra-articular hematoma at Day 1 serving as controls. Fold changes in gene expression values were measured, and genes were identified via clustering based on time series analysis and further categorised into three major temporal classes: increased, variable and decreased expression groups. The genes in these three temporal groups were further analysed to reveal pathways and establish their biological significance.

RESULTS

Osteoblastic and angiogenetic genes were found to be significantly expressed in the increased expression group. Genes linked to inflammation and osteoclasts were found in the decreased expression group. The various biological processes and pathways related to each temporal expression group were identified, and the increased expression group comprised genes exclusively involved in the following pathways: Hippo signaling pathway, Wnt signaling pathway and Rap 1 signaling pathway. The decreased expression group comprised genes exclusively involved in immune-related pathways and osteoclast differentiation. The variable expression group consisted of genes associated with DNA replication, DNA repair and DNA recombination. Significant biological pathways and transcription factors expressed at each time point postoperatively were also identified.

CONCLUSIONS

These data, for the first time, presented the temporal gene expression profiling and reveal the important process of molecular biology in the early-stage of traumatic TMJ bony ankylosis. The findings might contributed to identifying potential targets for the treatment of TMJ ankylosis.

Regulation of the immune microenvironment by pioglitazone-loaded polylactic glycolic acid nanosphere composite scaffolds to promote vascularization and bone regeneration

Osteogenesis is caused by multiple factors, and the inflammatory response, osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), regeneration of blood vessels, and other factors must be considered in bone tissue engineering. To effectively repair bone defect, it is important to decrease excessive inflammation, enhance the differentiation of mesenchymal stem cells into osteoblasts, and stimulate angiogenesis. Herein, nano-attapulgite (ATP), polyvinyl alcohol (PVA), and gelatin (GEL) scaffolds were produced using 3D printing technology and pioglitazone (PIO)-containing polylactic acid-glycolic acid (PLGA) nanospheres were added. In both in vitro and in vivo studies, material scaffolds with PIO-loaded polylactic acid-glycolic acid nanospheres could reduce the inflammatory response by encouraging macrophage polarization from M1 to M2 and promoting the osteogenic differentiation of BMSCs by activating the BMP2/Smad/RUNX2 signal pathway to repair bone defects. The vascularization of human umbilical vein endothelial cells (HUVECs) through the PI3K/AKT/HIF1-/VEGF pathway was also encouraged. In vivo research using PIO-containing PLGA nanospheres revealed massive collagen deposition in skin models. These findings indicate a potentially effective scaffold for bone healing, when PLGA nanospheres-which contain the drug PIO-are combined with ATP/PVA/GEL scaffolds.

Rationalizing a prospective coupling effect of cannabinoids with the current pharmacotherapy for melanoma treatment

Melanoma is one of the leading fatal forms of cancer, yet from a treatment perspective, we have minimal control over its reoccurrence and resistance to current pharmacotherapies. The endocannabinoid system (ECS) has recently been accepted as a multifaceted homeostatic regulator, influencing various physiological processes across different biological compartments, including the skin. This review presents an overview of the pathophysiology of melanoma, current pharmacotherapy used for treatment, and the challenges associated with the different pharmacological approaches. Furthermore, it highlights the utility of cannabinoids as an additive remedy for melanoma by restoring the balance between downregulated immunomodulatory pathways and elevated inflammatory cytokines during chronic skin conditions as one of the suggested critical approaches in treating this immunogenic tumor. This article is categorized under: Cancer > Molecular and Cellular Physiology.

The potential pharmacological mechanism of prunetin against osteoporosis: transcriptome analysis, molecular docking, and experimental approaches

BACKGROUND

Prunetin is an O-methylated isoflavone, known for its beneficial properties. However, its specific pharmacological effects in the treatment of osteoporosis (OP) remain poorly understood. This study aims to elucidate the mechanisms underlying the antiosteoporotic effects of prunetin through a combination of bioinformatics analysis and cell experiments.

METHODS

We gathered predicted targets of prunetin from various online platforms. Differential expression analysis of mRNAs in patients with OP was conducted using the Limma package, based on the GSE35959 dataset. A PPI network diagram was visualized and analyzed using Cytoscape 3.7.2 software. Molecular docking was employed to assess the binding affinity between ligands and receptors, and selected key genes were further validated through cell experiments.

RESULTS

A total of 4062 differentially expressed genes (DEGs) were identified from the GSE35959 dataset. Among these, 58 genes were found to overlap with the targets of prunetin, indicating their potential as therapeutic targets. The enrichment analysis indicated these targets were mainly enriched in MAPK, FoxO, and mTOR signaling pathways. The molecular docking analysis demonstrated that prunetin exhibited strong binding activity with the core targets. Furthermore, cell experiments revealed that prunetin effectively reversed the expression levels of ALB, ESR1, PTGS2, and FGFR1 mRNA in MC3T3-E1 cells treated with dexamethasone (DEX).

CONCLUSION

Our research revealed the multi-pathway and multi-target features of prunetin in treating OP, shedding light on the potential mechanisms underlying the effectiveness of prunetin against OP. These findings serve as a theoretical foundation for future drug development in this field.

Immunomodulation by mesenchymal stem cells during osteogenic differentiation: Clinical implications during bone regeneration

Critical bone defects resulting in delayed and non-union are a major concern in the field of orthopedics. Over the past decade, mesenchymal stem cells (MSCs) have become a promising frontier for bone repair and regeneration owing to their high expansion rate and osteogenic differentiation potential ex vivo. MSCs have also long been associated with their ability to modulate immune response in the recipients. These can even skew the immune response towards pro-inflammatory or anti-inflammatory type by sensing their local microenvironment. MSCs adopt anti-inflammatory phenotype at bone injury site and secrete various immunomodulatory factors such as IDO, NO, TGFβ1 and PGE-2 which have redundant role in osteoblast differentiation and bone formation. As such, several studies have also sought to decipher the immunomodulatory effects of osteogenically differentiated MSCs. The present review discusses the immunomodulatory status of MSCs during their osteogenic differentiation and summarizes few mechanisms that cause immunosuppression by osteogenically differentiated MSCs and its implication during bone healing.

Cu-Sr Bilayer Bioactive Glass Nanoparticles/Polydopamine Functionalized Polyetheretherketone Enhances Osteogenic Activity and Prevents Implant-Associated Infections through Spatiotemporal Immunomodulation

Key factors contributing to implantation failures include implant-associated infections (IAIs) and insufficient osseointegration of the implants. Polyetheretherketone (PEEK) is widely used in orthopedics, yet its clinical applications are restricted due to its poor osteogenic and antibacterial properties as well as inadequate immune responses. To overcome these drawbacks, a novel spatiotemporal immunomodulation approach is proposed, chelating Cu-Sr bilayer bioactive glass nanoparticles (CS-BGNs) onto the PEEK surface via polydopamine (PDA). The CS-BGNs possess a bilayer core-shell structure where copper is distributed in the outer layer and strontium is clustered in the inner layer. The results show that CS-BGNs/PDA functionalized PEEK demonstrates a controlled and sequential release of Cu2+ and Sr2+ . In the early stage, Cu2+ from the outer layer releases rapidly, while Sr2+ from the inner layer releases in the late stage. This well-ordered release pattern modulates the phenotypic transition of macrophages, which induces M1 polarization in the early stage and M2 polarization in the late stage. Combined with the direct effects of Cu2+ and Sr2+ , the spatiotemporal immunomodulation not only benefits the early antibacterial and tissue-healing process, but also promotes the long-term process of osseointegration, providing new perspectives on the design of novel immunomodulatory biomaterials.

Sustained Release of Dexamethasone from 3D-Printed Scaffolds Modulates Macrophage Activation and Enhances Osteogenic Differentiation

Enhancing osteogenesis via modulating immune cells is emerging as a new approach to address the current challenges in repairing bone defects and fractures. However, much remains unknown about the crosstalk between immune cells and osteolineage cells during bone formation. Moreover, biomaterial scaffold-based approaches to effectively modulate this crosstalk to favor bone healing are also lacking. This study is the first to investigate the interactions between macrophages and mesenchymal stem cells (MSCs) in co-cultures with the sustained release of an anti-inflammatory and pro-osteogenesis drug (dexamethasone) from three-dimensional (3D)-printed scaffolds. We successfully achieved the sustained release of dexamethasone from polycaprolactone (PCL) by adding the excipient-sucrose acetate isobutyrate (SAIB). Dexamethasone was released over 35 days in the 17-163 nM range. The osteogenic differentiation of MSCs was enhanced by M1 macrophages at early time points. The late-stage mineralization was dominated by dexamethasone, with little contribution from the macrophages. Besides confirming BMP-2 whose secretion was promoted by both dexamethasone and M1 macrophages as a soluble mediator for enhanced osteogenesis, IL-6 was found to be a possible new soluble factor that mediated osteogenesis in macrophage-MSC co-cultures. The phenotype switching from M1 to M2 was drastically enhanced by the scaffold-released dexamethasone but only marginally by the co-cultured MSCs. Our results offer new insight into macrophage-MSC crosstalk and demonstrate the potential of using drug-release scaffolds to both modulate inflammation and enhance bone regeneration.

Recent advances in immunomodulatory hydrogels biomaterials for bone tissue regeneration

There is a high incidence of fractures in clinical practice and therapy. The repairment of critical size defects in the skeletal system remains a huge challenge for surgeons and researchers, which can be overcame by the application of bone tissue-engineered biomaterials. An increasing number of investigations have revealed that the immune system plays a vital role in the repair of bone defects, especially macrophages, which can modulate the integration of biomaterials and bone regeneration in multiple ways. Therefore, it has become increasingly important in regenerative medicine to regulate macrophage polarization to prevent inflammation caused by biomaterial implantation. Recent studies have stressed the importance of hydrogel-based modifications and the incorporation of various cellular and molecular signals for regulating immune responses to promote bone tissue regeneration and integrate biomaterials. In this review, we first elaborate briefly on the described the general physiological mechanism and process of bone tissue regeneration. Then, we summarized the immunomodulatory role macrophages play in bone repair. In addition, the role of hydrogel-based immune modification targeting macrophage modulation in accelerating and enhancing bone tissue regeneration was also discussed. Finally, we highlighted future directions and research strategies related to hydrogel optimization for the regulation of the immune response during bone regeneration and healing.

Reduced angiogenesis and delayed endochondral ossification in CD163-/- mice highlights a role of M2 macrophages during bone fracture repair

While recent studies showed that macrophages are critical for bone fracture healing, and lack of M2 macrophages have been implicated in models of delayed union, functional roles for specific M2 receptors have yet to be defined. Moreover, the M2 scavenger receptor CD163 has been identified as a target to inhibit sepsis following implant-associated osteomyelitis, but potential adverse effects on bone healing during blockage therapy have yet to be explored. Thus, we investigated fracture healing in C57BL/6 versus CD163-/- mice using a well-established closed, stabilized, mid-diaphyseal femur fracture model. While gross fracture healing in CD163-/- mice was similar to that of C57BL/6, plain radiographs revealed persistent fracture gaps in the mutant mice on Day 14, which resolved by Day 21. Consistently, 3D vascular micro-CT demonstrated delayed union on Day 21, with reduced bone volume (74%, 61%, and 49%) and vasculature (40%, 40%, and 18%) compared to C57BL/6 on Days 10, 14, and 21 postfracture, respectively (p < 0.01). Histology confirmed large amounts of persistent cartilage in CD163-/- versus C57BL/6 fracture callus on Days 7 and 10 that resolves over time, and immunohistochemistry demonstrated deficiencies in CD206+ M2 macrophages. Torsion testing of the fractures confirmed the delayed early union in CD163-/- femurs, which display decreased yield torque on Day 21, and a decreased rigidity with a commensurate increase in rotation at yield on Day 28 (p < 0.01). Collectively, these results demonstrate that CD163 is required for normal angiogenesis, callus formation, and bone remodeling during fracture healing, and raise potential concerns about CD163 blockade therapy.

Mechanism and application of 3D-printed degradable bioceramic scaffolds for bone repair

Bioceramics have attracted considerable attention in the field of bone repair because of their excellent osteogenic properties, degradability, and biocompatibility. To resolve issues regarding limited formability, recent studies have introduced 3D printing technology for the fabrication of bioceramic bone repair scaffolds. Nevertheless, the mechanisms by which bioceramics promote bone repair and clinical applications of 3D-printed bioceramic scaffolds remain elusive. This review provides an account of the fabrication methods of 3D-printed degradable bioceramic scaffolds. In addition, the types and characteristics of degradable bioceramics used in clinical and preclinical applications are summarized. We have also highlighted the osteogenic molecular mechanisms in biomaterials with the aim of providing a basis and support for future research on the clinical applications of degradable bioceramic scaffolds. Finally, new developments and potential applications of 3D-printed degradable bioceramic scaffolds are discussed with reference to experimental and theoretical studies.

Latest advances: Improving the anti-inflammatory and immunomodulatory properties of PEEK materials

Excellent biocompatibility, mechanical properties, chemical stability, and elastic modulus close to bone tissue make polyetheretherketone (PEEK) a promising orthopedic implant material. However, biological inertness has hindered the clinical applications of PEEK. The immune responses and inflammatory reactions after implantation would interfere with the osteogenic process. Eventually, the proliferation of fibrous tissue and the formation of fibrous capsules would result in a loose connection between PEEK and bone, leading to implantation failure. Previous studies focused on improving the osteogenic properties and antibacterial ability of PEEK with various modification techniques. However, few studies have been conducted on the immunomodulatory capacity of PEEK. New clinical applications and advances in processing technology, research, and reports on the immunomodulatory capacity of PEEK have received increasing attention in recent years. Researchers have designed numerous modification techniques, including drug delivery systems, surface chemical modifications, and surface porous treatments, to modulate the post-implantation immune response to address the regulatory factors of the mechanism. These studies provide essential ideas and technical preconditions for the development and research of the next generation of PEEK biological implant materials. This paper summarizes the mechanism by which the immune response after PEEK implantation leads to fibrous capsule formation; it also focuses on modification techniques to improve the anti-inflammatory and immunomodulatory abilities of PEEK. We also discuss the limitations of the existing modification techniques and present the corresponding future perspectives.

Connection of COX-2 variants to ankylosing spondylitis susceptibility

This study aimed to explore the associations of COX-2 polymorphisms rs5275, rs20417, and rs2745557 with the susceptibility to ankylosing spondylitis among Chinese Han people. Polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) was adopted for genotyping COX-2 polymorphisms rs5275, rs20417, and rs2745557 among 109 AS patients and 122 healthy controls. Genotype distribution in the control group was examined for these three polymorphisms to test whether it conformed to Hardy-Weinberg equilibrium (HWE) expectation. A χ2 -test was employed to compare genotype and allele frequencies between the two groups. Besides this, logistic regression analyses were also performed to adjust age and gender. A p less than .05 represented a significant level. Genotype distribution of our studied polymorphisms showed fine conformity to HWE in the controls. An increasing effect on AS risk was detected for the polymorphism rs5275 under GG versus AA contrast (crude: OR, 3.040; 95% CI, 1.015-9.104), and the adjustment for age and gender did not change such a relationship (adjusted OR, 3.307; 95% CI, 1.065-10.268). After adjusting age and gender, both polymorphisms of rs20417 and rs2745557 demonstrated a negative relationship with the disease susceptibility. The GC genotype and C allele of rs20417 reduced the disease risk to 0.248 (adjusted: 95% CI, 0.089-0.692) and 0.269 (95% CI, 0.098-0.733), respectively, while the AA genotype and A allele of the latter to 0.413 (adjusted: 95% CI, 0.191-0.893) and 0.676 (adjusted: 95% CI, 0.466-0.981), respectively. Among Chinese Han people, COX-2 polymorphism rs5275 may contribute to increased risk of developing AS, while the polymorphisms rs20417 and rs2745557 may offer protection against disease incidence.

Patient-specific primary and pluripotent stem cell-derived stromal cells recapitulate key aspects of arrhythmogenic cardiomyopathy

Primary cardiac mesenchymal stromal cells (C-MSCs) can promote the aberrant remodeling of cardiac tissue that characterizes arrhythmogenic cardiomyopathy (ACM) by differentiating into adipocytes and myofibroblasts. These cells' limitations, including restricted access to primary material and its manipulation have been overcome by the advancement of human induced pluripotent stem cells (hiPSCs), and their ability to differentiate towards the cardiac stromal population. C-MSCs derived from hiPSCs make it possible to work with virtually unlimited numbers of cells that are genetically identical to the cells of origin. We performed in vitro experiments on primary stromal cells (Primary) and hiPSC-derived stromal cells (hiPSC-D) to compare them as tools to model ACM. Both Primary and hiPSC-D cells expressed mesenchymal surface markers and possessed typical MSC differentiation potentials. hiPSC-D expressed desmosomal genes and proteins and shared a similar transcriptomic profile with Primary cells. Furthermore, ACM hiPSC-D exhibited higher propensity to accumulate lipid droplets and collagen compared to healthy control cells, similar to their primary counterparts. Therefore, both Primary and hiPSC-D cardiac stromal cells obtained from ACM patients can be used to model aspects of the disease. The choice of the most suitable model will depend on experimental needs and on the availability of human source samples.

Interaction between Mesenchymal Stem Cells and Immune Cells during Bone Injury Repair

Fractures are the most common large organ trauma in humans. The initial inflammatory response promotes bone healing during the initial post-fracture phase, but chronic and persistent inflammation due to infection or other factors does not contribute to the healing process. The precise mechanisms by which immune cells and their cytokines are regulated in bone healing remain unclear. The use of mesenchymal stem cells (MSCs) for cellular therapy of bone injuries is a novel clinical treatment approach. Bone progenitor MSCs not only differentiate into bone, but also interact with the immune system to promote the healing process. We review in vitro and in vivo studies on the role of the immune system and bone marrow MSCs in bone healing and their interactions. A deeper understanding of this paradigm may provide clues to potential therapeutic targets in the healing process, thereby improving the reliability and safety of clinical applications of MSCs to promote bone healing.

Manganese-Implanted Titanium Modulates the Crosstalk between Bone Marrow Mesenchymal Stem Cells and Macrophages to Improve Osteogenesis

Manganese (Mn) is an essential micronutrient in various physiological processes, but its functions in bone metabolism remain undefined. This is partly due to the interplay between immune and bone cells because Mn plays a central role in the immune system. In this study, we utilized the plasma immersion ion implantation and deposition (PIII&D) technique to introduce Mn onto the titanium surface. The results demonstrated that Mn-implanted surfaces stimulated the shift of macrophages toward the M1 phenotype and had minimal effects on the osteogenic differentiation of mouse bone marrow mesenchymal stem cells (mBMSCs) under mono-culture conditions. However, they promoted the M2 polarization of macrophages and improved the osteogenic activities of mBMSCs under co-culture conditions, indicating the importance of the crosstalk between mBMSCs and macrophages mediated by Mn in osteogenic activities. This study provides a positive incentive for the application of Mn in the field of osteoimmunology.

A new osteogenic protein isolated from Dioscorea opposita Thunb accelerates bone defect healing through the mTOR signaling axis

Delayed bone defect repairs lead to severe health and socioeconomic impacts on patients. Hence, there are increasing demands for medical interventions to promote bone defect healing. Recombinant proteins such as BMP-2 have been recognized as one of the powerful osteogenic substances that promote mesenchymal stem cells (MSCs) to osteoblast differentiation and are widely applied clinically for bone defect repairs. However, recent reports show that BMP-2 treatment has been associated with clinical adverse side effects such as ectopic bone formation, osteolysis and stimulation of inflammation. Here, we have identified one new osteogenic protein, named 'HKUOT-S2' protein, from Dioscorea opposita Thunb. Using the bone defect model, we have shown that the HKUOT-S2 protein can accelerate bone defect repair by activating the mTOR signaling axis of MSCs-derived osteoblasts and increasing osteoblastic biomineralization. The HKUOT-S2 protein can also modulate the transcriptomic changes of macrophages, stem cells, and osteoblasts, thereby enhancing the crosstalk between the polarized macrophages and MSCs-osteoblast differentiation to facilitate osteogenesis. Furthermore, this protein had no toxic effects in vivo. We have also identified HKUOT-S2 peptide sequence TKSSLPGQTK as a functional osteogenic unit that can promote osteoblast differentiation in vitro. The HKUOT-S2 protein with robust osteogenic activity could be a potential alternative osteoanabolic agent for promoting osteogenesis and bone defect repairs. We believe that the HKUOT-S2 protein may potentially be applied clinically as a new class of osteogenic agent for bone defect healing.

Dual stimulus responsive borosilicate glass (BSG) scaffolds promote diabetic alveolar bone defectsrepair by modulating macrophage phenotype

The regeneration of alveolar bone is still clinical challenge, particularly accompanied with diabetes, causing metabolic disorder with a protracted low-grade inflammatory phenotype. As a result, the anticipated loading of biomaterials is highly suspicious in spontaneous modulation of cells function, which is mostly disturbed by constant inflammation. In this study, we developed glucose and hydrogen peroxide dual-responsive borosilicate glass (BSG) scaffolds loaded with epigallocatechin gallate (EGCG) to synergistically modulate the abnormal inflammation of diabetic alveolar bone defects. It was found that the release of EGCG by BSG could directly regulate the shift of macrophages from M1 to the M2 phenotype by promoting autophagy and lessening the inhibition of autophagic flux. Moreover, EGCG can also indirectly regulate the polarization phenotype of macrophages by reducing the activation of NF-κb in stem cells and restoring its immunoregulatory capacity. Therefore, the addition of EGCG to BSG scaffold in diabetes allows for a more striking modulation of the macrophage phenotype in a timely manner. The altered macrophage phenotype reduces local inflammation and thus increases the ability to repair diabetic alveolar bone, showing promise for the treatment of alveolar defect in diabetic patients.

Monitoring mRNA Expression Patterns in Macrophages in Response to Two Different Strains of Probiotics

As an initial study to elucidate the molecular mechanism of how probiotics modulate macrophage activity, we monitored mRNA expression patterns in peritoneal macrophages (PMs) treated with two different strains of probiotics. After treatment with either Weissella cibaria WIKIM28 or Latilactobacillus sakei WIKIM50, total RNAs from PMs were isolated and subjected into gene chip analyses. As controls, mRNAs from vehicle (phosphate-buffered saline, PBS)-treated PMs were also subjected to gene chip analysis. Compared to vehicle (PBS)-treated PMs, WIKIM28-treated and WIKIM50-treated PMs exhibited a total of 889 and 432 differentially expressed genes with expression differences of at least 4 folds, respectively. Compared to WIKIM28-treated PMs, WIKIM50-treated PMs showed 25 up-regulated genes and 21 down-regulated genes with expression differences of more than 2 folds. Interestingly, mRNA transcripts of M2 macrophage polarization marker such as anxa1, mafb, and sepp1 were increased in WIKIM50-treated PMs comparing to those in WIKIM28-treated PMs. Reversely, mRNA transcripts of M1 macrophage polarization marker such as hdac9, ptgs2, and socs3 were decreased in WIKIM50-treated PMs comparing to those in WIKIM28-treated PMs. In agreement with these observations, mRNA expression levels of tumor necrosis factor-α and interleukin-1α were significantly reduced in WIKIM50-treated macrophages compared to those in WIKIM28-treated macrophages. These results may indicate that probiotics can be classified as two different types depending on their ability to convert macrophages into M1 or M2 polarization.

CCL2 promotes osteogenesis by facilitating macrophage migration during acute inflammation

Novel minimally invasive strategies are needed to obtain robust bone healing in complex fractures and bone defects in the elderly population. Local cell therapy is one potential option for future treatment. Mesenchymal stromal cells (MSCs) are not only involved in osteogenesis but also help direct the recruitment of macrophages during bone regeneration via MSC-macrophage crosstalk. The C-C motif chemokine ligand 2 (CCL2) is an inflammatory chemokine that is associated with the migration of macrophages and MSCs during inflammation. This study investigated the use of CCL2 as a therapeutic target for local cell therapy. MSCs and macrophages were isolated from 10 to 12 week-old BALB/c male mice. Genetically modified CCL2 over-expressing MSCs were produced using murine CCL2-secreting pCDH-CMV-mCCL2-copGFP expressing lentivirus vector. Osteogenic differentiation assays were performed using MSCs with or without macrophages in co-culture. Cell migration assays were also performed. MSCs transfected with murine CCL2-secreting pCDH-CMV-mCCL2-copGFP expressing lentivirus vector showed higher levels of CCL2 secretion compared to unaltered MSCs (p < 0.05). Genetic manipulation did not affect cell proliferation. CCL2 did not affect the osteogenic ability of MSCs alone. However, acute (1 day) but not sustained (7 days) stimulation with CCL2 increased the alizarin red-positive area when MSCs were co-cultured with macrophages (p < 0.001). Both recombinant CCL2 (p < 0.05) and CCL2 released from MSCs (p < 0.05) facilitated macrophage migration. We demonstrated that acute CCL2 stimulation promoted subsequent osteogenesis in co-culture of MSCs and macrophages. Acute CCL2 stimulation potentially facilitates osteogenesis during the acute inflammatory phase of bone healing by directing local macrophage migration, fostering macrophage-MSC crosstalk, and subsequently, by activating or licensing of MSCs by macrophage pro-inflammatory cytokines. The combination of CCL2, MSCs, and macrophages could be a potential strategy for local cell therapy in compromised bone healing.

Biomaterial-Assisted Macrophage Cell Therapy for Regenerative Medicine

Although most tissue types are capable of some form of self-repair and regeneration, injuries that are larger than a critical threshold or those occurring in the setting of certain diseases can lead to impaired healing and ultimately loss of structure and function. The immune system plays an important role in tissue repair and must be considered in the design of therapies in regenerative medicine. In particular, macrophage cell therapy has emerged as a promising strategy that leverages the reparative roles of these cells. Macrophages are critical for successful tissue repair and accomplish diverse functions throughout all phases of the process by dramatically shifting in phenotypes in response to microenvironmental cues. Depending on their response to various stimuli, they may release growth factors, support angiogenesis, and facilitate extracellular matrix remodeling. However, this ability to rapidly shift phenotype is also problematic for macrophage cell therapy strategies, because adoptively transferred macrophages fail to maintain therapeutic phenotypes following their administration to sites of injury or inflammation. Biomaterials are a potential way to control macrophage phenotype in situ while also enhancing their retention at sites of injury. Cell delivery systems incorporated with appropriately designed immunomodulatory signals have potential to achieve tissue regeneration in intractable injuries where traditional therapies have failed. Here we explorecurrent challenges in macrophage cell therapy, especially retention and phenotype control, how biomaterials may overcome them, and opportunities for next generation strategies. Biomaterials will be an essential tool to advance macrophage cell therapy for widespread clinical applications.

Macrophages-bone marrow mesenchymal stem cells crosstalk in bone healing

Bone healing is associated with many orthopedic conditions, including fractures and osteonecrosis, arthritis, metabolic bone disease, tumors and periprosthetic particle-associated osteolysis. How to effectively promote bone healing has become a keen topic for researchers. The role of macrophages and bone marrow mesenchymal stem cells (BMSCs) in bone healing has gradually come to light with the development of the concept of osteoimmunity. Their interaction regulates the balance between inflammation and regeneration, and when the inflammatory response is over-excited, attenuated, or disturbed, it results in the failure of bone healing. Therefore, an in-depth understanding of the function of macrophages and bone marrow mesenchymal stem cells in bone regeneration and the relationship between the two could provide new directions to promote bone healing. This paper reviews the role of macrophages and bone marrow mesenchymal stem cells in bone healing and the mechanism and significance of their interaction. Several new therapeutic ideas for regulating the inflammatory response in bone healing by targeting macrophages and bone marrow mesenchymal stem cells crosstalk are also discussed.

The response of human macrophages to 3D printed titanium antibacterial implants does not affect the osteogenic differentiation of hMSCs

Macrophage responses following the implantation of orthopaedic implants are essential for successful implant integration in the body, partly through intimate crosstalk with human marrow stromal cells (hMSCs) in the process of new bone formation. Additive manufacturing (AM) and plasma electrolytic oxidation (PEO) in the presence of silver nanoparticles (AgNPs) are promising techniques to achieve multifunctional titanium implants. Their osteoimmunomodulatory properties are, however, not yet fully investigated. Here, we studied the effects of implants with AgNPs on human macrophages and the crosstalk between hMSCs and human macrophages when co-cultured in vitro with biofunctionalised AM Ti6Al4V implants. A concentration of 0.3 g/L AgNPs in the PEO electrolyte was found to be optimal for both macrophage viability and inhibition of bacteria growth. These specimens also caused a decrease of the macrophage tissue repair related factor C-C Motif Chemokine Ligand 18 (CCL18). Nevertheless, co-cultured hMSCs could osteogenically differentiate without any adverse effects caused by the presence of macrophages that were previously exposed to the PEO (±AgNPs) surfaces. Further evaluation of these promising implants in a bony in vivo environment with and without infection is highly recommended to prove their potential for clinical use.

Potential application of inorganic nano-materials in modulation of macrophage function: Possible application in bone tissue engineering

Nanomaterials indicate unique physicochemical properties for drug delivery in osteogenesis. Benefiting from high surface area grades, high volume ratio, ease of functionalization by biological targeting moieties, and small size empower nanomaterials to pass through biological barriers for efficient targeting. Inorganic nanomaterials for bone regeneration include inorganic synthetic polymers, ceramic nanoparticles, metallic nanoparticles, and magnetic nanoparticles. These nanoparticles can effectively modulate macrophage polarization and function, as one of the leading players in osteogenesis. Bone healing procedures in close cooperation with the immune system. Inflammation is one of the leading triggers of the bone fracture healing barrier. Macrophages commence anti-inflammatory signaling along with revascularization in the damaged site to promote the formation of a soft callus, bone mineralization, and bone remodeling. In this review, we will discuss the role of macrophages in bone hemostasis and regeneration. Furthermore, we will summarize the influence of the various inorganic nanoparticles on macrophage polarization and function in the benefit of osteogenesis.

Macrophage polarization in bone implant repair: A review

Macrophages (MΦ) are highly adaptable and functionally polarized cells that play a crucial role in various physiological and pathological processes. Typically, MΦ differentiate into two distinct subsets: the proinflammatory (M1) and anti-inflammatory (M2) phenotypes. Due to their potent immunomodulatory and anti-inflammatory properties, MΦ have garnered significant attention in recent decades. In the context of bone implant repair, the immunomodulatory function of MΦ is of paramount importance. Depending on their polarization phenotype, MΦ can exert varying effects on osteogenesis, angiogenesis, and the inflammatory response around the implant. This paper provides an overview of the immunomodulatory and inflammatory effects of MΦ polarization in the repair of bone implants.

Therapeutic Agent-Loaded Fibrous Scaffolds for Biomedical Applications

Tissue engineering is a sophisticated field that involves the integration of various disciplines, such as clinical medicine, material science, and life science, to repair or regenerate damaged tissues and organs. To achieve the successful regeneration of damaged or diseased tissues, it is necessary to fabricate biomimetic scaffolds that provide structural support to the surrounding cells and tissues. Fibrous scaffolds loaded with therapeutic agents have shown considerable potential in tissue engineering. In this comprehensive review, we examine various methods for fabricating bioactive molecule-loaded fibrous scaffolds, including preparation methods for fibrous scaffolds and drug-loading techniques. Additionally, we delved into the recent biomedical applications of these scaffolds, such as tissue regeneration, inhibition of tumor recurrence, and immunomodulation. The aim of this review is to discuss the latest research trends in fibrous scaffold manufacturing methods, materials, drug-loading methods with parameter information, and therapeutic applications with the goal of contributing to the development of new technologies or improvements to existing ones.

A surface metal ion-modified 3D-printed Ti-6Al-4V implant with direct and immunoregulatory antibacterial and osteogenic activity

The high concentration of antibacterial metal ions may exhibit unavoidable toxicity to cells and normal tissues. The application of antibacterial metal ions to activate the immune response and induce macrophages to attack and phagocytose bacteria is a new antimicrobial strategy. Herein, 3D-printed Ti-6Al-4V implants modified by copper, and strontium ions combined with natural polymers were designed to treat implant-related infections and osseointegration disorders. The polymer-modified scaffolds rapidly released a large amount of copper and strontium ions. During the release process, copper ions were employed to promote the polarization of M1 macrophages, thus inducing a proinflammatory immune response to inhibit infection and achieve the immune antibacterial activity. Meanwhile, copper and strontium ions promoted the secretion of bone-promoting factors by macrophages, induced osteogenesis and showed immunomodulatory osteogenesis. This study proposed immunomodulatory strategies based on the immunological characteristics of target diseases and provided ideas for the design and synthesis of new immunoregulatory biomaterials.

Research Progress of Macrophages in Bone Regeneration

Bone tissue regeneration plays an increasingly important role in contemporary clinical treatment. The reconstruction of bone defects remains a huge challenge for clinicians. Bone regeneration is regulated by the immune system, in which inflammation is an important regulating factor in bone formation and remodeling. As the main cells involved in inflammation, macrophages play a key role in osteogenesis by polarizing into different phenotypes during different stages of bone regeneration. Considering this, this review mainly summarizes the function of macrophage in bone regeneration based on mesenchymal stem cells (MSCs), osteoblasts, osteoclasts, and vascular cells. In conclusion, anti-inflammatory macrophages (M2) have a greater potentiality to promote bone regeneration than M0 and classically activated proinflammatory macrophages (M1). In the fracture and bone defect models, tissue engineering materials can induce the transition from M1 to M2, alter the bone microenvironment, and promote bone regeneration through interactions with bone-related cells and blood vessels. The review provides a further understanding of macrophage polarization behavior in the evolving field of bone immunology.

Macrophage response mediated by extracellular matrix: recent progress

Biomaterials are one of efficient treatment options for tissue defects in regenerative medicine. Compared to synthetic materials which tend to induce chronic inflammatory response and fibrous capsule, extracellular matrix (ECM) scaffold materials composed of biopolymers are thought to be capable of inducing a pro-regenerative immune microenvironment and facilitate wound healing. Immune cells are the first line of response to implanted biomaterials. In particular, macrophages greatly affect cell behavior and the ultimate treatment outcome based on multiple cell phenotypes with various functions. The macrophage polarization status is considered as a general reflection of the characteristics of the immune microenvironment. Since numerous reports has emphasized the limitation of classical M1/M2 nomenclature, high-resolution techniques such as single-cell sequencing has been applied to recognize distinct macrophage phenotypes involved in host responses to biomaterials. After reviewing latest literatures that explored the immune microenvironment mediated by ECM scaffolds, this paper describe the behaviors of highly heterogeneous and plastic macrophages subpopulations which affect the tissue regeneration. The mechanisms by which ECM scaffolds interact with macrophages are also discussed from the perspectives of the ECM ultrastructure along with the nucleic acid, protein, and proteoglycan compositions, in order to provide targets for potential therapeutic modulation in regenerative medicine.

Polarization Behavior of Bone Macrophage as Well as Associated Osteoimmunity in Glucocorticoid-Induced Osteonecrosis of the Femoral Head

Glucocorticoid-induced osteonecrosis of the femoral head (GIONFH) is a disabling disease with high mortality in China but the detailed molecular and cellular mechanisms remain to be investigated. Macrophages are considered the key cells in osteoimmunology, and the cross-talk between bone macrophages and other cells in the microenvironment is involved in maintaining bone homeostasis. M1 polarized macrophages launch a chronic inflammatory response and secrete a broad spectrum of cytokines (eg, TNF-α, IL-6 and IL-1β) and chemokines to initiate a chronic inflammatory state in GIONFH. M2 macrophage is the alternatively activated anti-inflammatory type distributed mainly in the perivascular area of the necrotic femoral head. In the development of GIONFH, injured bone vascular endothelial cells and necrotic bone activate the TLR4/NF-κB signal pathway, promote dimerization of PKM2 and subsequently enhance the production of HIF-1, inducing metabolic transformation of macrophage to the M1 phenotype. Considering these findings, putative interventions by local chemokine regulation to correct the imbalance between M1/M2 polarized macrophages by switching macrophages to an M2 phenotype, or inhibiting the adoption of an M1 phenotype appear to be plausible regimens for preventing or intervening GIONFH in the early stage. However, these results were mainly obtained by in vitro tissue or experimental animal model. Further studies to completely elucidate the alterations of the M1/M2 macrophage polarization and functions of macrophages in glucocorticoid-induced osteonecrosis of the femoral head are imperative.

Unveiling the Time Course Mechanism of Bone Fracture Healing by Transcriptional Profiles

BACKGROUND

Bone fracture healing is a time-consuming and high-priority orthopedic problem worldwide.

OBJECTIVE

Discovering the potential mechanism of bone healing at a time course and transcriptional level may better help manage bone fracture.

METHODS

In this study, we analyze a time-course bone fracture healing transcriptional dataset in a rat model (GSE592, GSE594, and GSE1371) of Gene Expression Omnibus (GEO). RNA was obtained from female Sprague-Dawley rats with a femoral fracture at the initial time (day 3) as well as early (week 1), middle (week 2), and late (week 4) time periods, with nonfracture rats used as control. Gene Ontology (GO) functional analysis and pathway examinations were performed for further measurements of GSEA and hub genes.

RESULTS

Results indicated that the four stages of bone fracture healing at the initial, early, middle, and late time periods represent the phases of hematoma formation, callus formation, callus molding, and mature lamellar bone formation, respectively. Extracellular organization was positively employed throughout the four stages. At the hematoma formation phase, the muscle contraction process was downregulated. Antibacterial peptide pathway was downregulated at all phases. The upregulation of Fn1 (initial, early, middle, and late time periods), Col3a1 (initial, early, and middle time periods), Col11a1 (initial and early time periods), Mmp9 (middle and late time periods), Mmp13 (early, middle, and late time periods) and the downregulation of RatNP-3b (initial, early, middle, and late time periods) were possible symbols for bone fracture healing and may be used as therapeutic targets.

CONCLUSION

These findings suggest some new potential pathways and genes in the process of bone fracture healing and further provide insights that can be used in targeted molecular therapy for bone fracture healing.

Strategies of Macrophages to Maintain Bone Homeostasis and Promote Bone Repair: A Narrative Review

Bone homeostasis (a healthy bone mass) is regulated by maintaining a delicate balance between bone resorption and bone formation. The regulation of physiological bone remodeling by a complex system that involves multiple cells in the skeleton is closely related to bone homeostasis. Loss of bone mass or repair of bone is always accompanied by changes in bone homeostasis. However, due to the complexity of bone homeostasis, we are currently unable to identify all the mechanisms that affect bone homeostasis. To date, bone macrophages have been considered a third cellular component in addition to osteogenic spectrum cells and osteoclasts. As confirmed by co-culture models or in vivo experiments, polarized or unpolarized macrophages interact with multiple components within the bone to ensure bone homeostasis. Different macrophage phenotypes are prone to resorption and formation of bone differently. This review comprehensively summarizes the mechanisms by which macrophages regulate bone homeostasis and concludes that macrophages can control bone homeostasis from osteoclasts, mesenchymal cells, osteoblasts, osteocytes, and the blood/vasculature system. The elaboration of these mechanisms in this narrative review facilitates the development of macrophage-based strategies for the treatment of bone metabolic diseases and bone defects.

Morinda officinalis polysaccharide enable suppression of osteoclastic differentiation by exosomes derived from rat mesenchymal stem cells

CONTEXT

Morinda officinalis F.C. How. (MO) (Rubiaceae) can strengthen bone function.

OBJECTIVE

To examine the functional mechanism and effect of MO polysaccharides (MOPs) in rats with glucocorticoid-induced osteoporosis (GIOP).

MATERIALS AND METHODS

Rats with GIOP were treated with 5, 15 or 45 mL/kg of MOP [n = 15 for each dose, intraperitoneal (i.p.) injection every other day for 8 weeks]. The body weight of rats and histomorphology of bone tissues were examined. Bone marrow mesenchymal stem cells (BMSCs)-derived exosomes (Exo) were collected and identified. Bone marrow-derived macrophages (BMMs) were induced to differentiate into osteoclasts and treated with BMSC-Exo for in vitro studies.

RESULTS

MOP reduced the body weight (5, 15, or 45 mg/kg MOP vs. phosphate-buffered saline: 8%, 15% and 25%, p < 0.01), elevated the bone volume to tissue volume (BV/TV), mean trabecular thickness (Tb.Th), mean trabecular number (Tb.N) and mean connectivity density (Conn.D) (40-86%, p < 0.01), decreased the mean trabecular separation/spacing (Tb.Sp) (22-37%, p < 0.01), increased the cortical bone continuity (35-90%, p < 0.01) and elevated RUNX family transcription factor 2 and RANK levels (5-12%, p < 0.01), but suppressed matrix metallopeptidase 9 and cathepsin K levels (9-20%, p < 0.01) in femur tissues. BMSC-Exo from MOP-treated rats (MOP-Exo) suppressed osteoclastic differentiation and proliferation of BMMs. The downregulation of microRNA-101-3p (miR-101-3p) or the upregulation of prostaglandin-endoperoxide synthase 2 (PTGS2) blocked the functions of MOP-Exo.

DISCUSSION AND CONCLUSIONS

MOP inhibits osteoclastic differentiation and could potentially be used for osteoporosis management. This suppression may be enhanced by the upregulation of miR-101-3p or the inhibition of PTGS2.

Role of Mesenchymal Stem Cells and Their Paracrine Mediators in Macrophage Polarization: An Approach to Reduce Inflammation in Osteoarthritis

Osteoarthritis (OA) is a low-grade inflammatory disorder of the joints that causes deterioration of the cartilage, bone remodeling, formation of osteophytes, meniscal damage, and synovial inflammation (synovitis). The synovium is the primary site of inflammation in OA and is frequently characterized by hyperplasia of the synovial lining and infiltration of inflammatory cells, primarily macrophages. Macrophages play a crucial role in the early inflammatory response through the production of several inflammatory cytokines, chemokines, growth factors, and proteinases. These pro-inflammatory mediators are activators of numerous signaling pathways that trigger other cytokines to further recruit more macrophages to the joint, ultimately leading to pain and disease progression. Very few therapeutic alternatives are available for treating inflammation in OA due to the condition's low self-healing capacity and the lack of clear diagnostic biomarkers. In this review, we opted to explore the immunomodulatory properties of mesenchymal stem cells (MSCs) and their paracrine mediators-dependent as a therapeutic intervention for OA, with a primary focus on the practicality of polarizing macrophages as suppression of M1 macrophages and enhancement of M2 macrophages can significantly reduce OA symptoms.

Immediate to short-term inflammatory response to biomaterial implanted in calvarium of mice

Scaffolds made of biodegradable materials play a very important role in repairing bone defects. Our study was conducted with the aim of investigating inflammation, vascular changes, and tissue necrosis after the placement of 3D printed scaffolds composed of beta-tricalcium phosphate (TCP-β) on the calvarial bone defect of mice. Eight samples of scalp tissue in mice were examined in four groups (one-week control, two-week control, one-week experiment, and two-week experiment). Mice with routine bone defects were selected as the control group and mice with bone defects with β-TCP scaffolds were selected as the experimental group (TCP). The groups were evaluated in terms of inflammatory cells, osteoblast and osteoclast cells, vascular changes, and the number of resorption pit and empty lacuna. The results demonstrated a decrease in inflammatory cells and an increase in osteoclast and osteoblast cells in bone defect sites placed with TCP-β scaffolds (p<0.05). The results of histological staining showed pit resorption and further vascularization in the place of TCP-β scaffolds, but these changes were not statistically significant (p>0.05). Examining the number of empty lacunae in the bone defect site showed that TCP-β could significantly reduce the number of these lacunae in the bone defect sites placed with TCP-β scaffolds (p<0.05). 3D printed scaffolds composed of TCP-β that were implanted in bone defect sites were effective in reducing the inflammatory responses, emptying lacunae and increasing bone regeneration.

Engineering immunomodulatory hydrogels and cell-laden systems towards bone regeneration

The well-known synergetic interplay between the skeletal and immune systems has changed the design of advanced bone tissue engineering strategies. The immune system is essential during the bone lifetime, with macrophages playing multiple roles in bone healing and biomaterial integration. If in the past, the most valuable aspect of implants was to avoid immune responses of the host, nowadays, it is well-established how important are the crosstalks between immune cells and bone-engineered niches for an efficient regenerative process to occur. For that, it is essential to recapitulate the multiphenotypic cellular environment of bone tissue when designing new approaches. Indeed, the lack of osteoimmunomodulatory knowledge may be the explanation for the poor translation of biomaterials into clinical practice. Thus, smarter hydrogels incorporating immunomodulatory bioactive factors, stem cells, and immune cells are being proposed to develop a new generation of bone tissue engineering strategies. This review highlights the power of immune cells to upgrade the development of innovative engineered strategies, mainly focusing on orthopaedic and dental applications.