Macrophage-Mediated Bone Formation in Scaffolds Modified With MSC-Derived Extracellular Matrix Is Dependent on the Migration Inhibitory Factor Signaling Pathway

Tideglusib enhances ALP activity and upregulates RANKL expression in Osteoblast-macrophage Co-cultures within a 3D collagen scaffold

OBJECTIVES

Tideglusib (Tx) is known for its osteogenic potential, yet its effects on the interplay between osteoblasts and M1 macrophages remain underexplored. This in vitro study aimed to isolate and evaluate both the individual and combined roles of M1 macrophages and osteoblasts in macrophage differentiation and osteoblast function, specifically focusing on how these interactions influence protein expression of osteogenesis and osteoclastogenesis in the presence or absence of Tx.

METHODS

Osteoblast and macrophage cells were co-cultured in direct contact for 24 and 48 h, with or without the presence of Tx. ALP activity, the expression of inflammatory-related genes using RT-qPCR, and histological analyses were performed.

RESULTS

Co-culturing osteoblasts and M1 macrophages with Tx increased alkaline phosphatase production, indicative of enhanced osteoblast activity. Histological assessments revealed that Tx treatment contributed to the stability and maintenance of cell morphology within the scaffold, suggesting a supportive environment for cell viability and function. Tx significantly reduced the expression of pro-inflammatory markers, such as TNF-α and IL-1β, in the co-culture at both 24 and 48 h Tx also effectively inhibited osteoclastogenic differentiation in macrophages, thereby diminishing their pro-inflammatory phenotype.

CONCLUSIONS

Tx increased ALP activity and produced a significant up-regulation of RANKL expression, indicating enhanced osteoblast differentiation and osteoclast activation. Tx mitigates macrophage-driven inflammation.

CLINICAL SIGNIFICANCE

Tx may enhance bone regeneration by modulating inflammatory responses and preserving cell integrity.

Enhanced surface hydrophilicity improves osseointegration of titanium implants via integrin-mediated osteoimmunomodulation

Titanium (Ti) implants have become widespread especially in dentistry and orthopedics, where macrophage-driven osteoimmunomodulation is crucial to their success. Hydrophilic modification of Ti represents a promising strategy to enhance its immune and osteogenic responses. Herein, the osteoimmunomodulatory performance and integrin-mediated mechanism of novel non-thermal atmospheric plasma (NTAP) treatment to induce a hydrophilic Ti were investigated for the first time. Compared to a hydrophobic surface, NTAP-modified Ti possessed a 3-fold increase of pro-healing M2 macrophage makers, and the doubled osteogenic differentiation of mesenchymal stem cells was demonstrated in this immune microenvironment, thus improving early osseointegration. Mechanistically, the ameliorative osteoimmunomodulatory properties of NTAP were attributed to its positive and negative modulation in macrophages' integrin β1 or β2, and the subsequent FAK-PI3K/Akt or NF-κB signaling pathway. Collectively, this study highlighted the role of integrins and related signaling pathways in hydrophilic implant-caused macrophage polarization, therefore inventively unveiling the underlying mechanism of NTAP-enhanced osteoimmunomodulation. Furthermore, it established a robust theoretical foundation for the clinical application of this cost-effective, versatile, and transformation-valuable surface engineering strategy for the development of next-generation Ti implants.

Macrophage migration inhibitory factor promotes heterotopic ossification by mediating ROS/HIF-1α positive feedback loop and activating Wnt/β-catenin signaling pathway

BACKGROUND

Heterotopic ossification (HO) refers to the development of bone tissue in areas other than the skeletal system. The development and maturation of the skeletal system are significantly influenced by macrophage migration inhibitory factor (MIF). The objective of this study was to examine the impact of MIF on the in vitro osteogenic differentiation and mineralization of tendon-derived stem cells (TDSCs), mediated by a positive feedback loop involving ROS/HIF-1α/MIF.

METHODS

TDSCs were isolated and identified from the hind limbs of C57/BL6 mice. The functional and procedural roles of MIF in HO, focusing on the impact of MIF on the differentiation of TDSCs into bone-forming cells were investigated in vitro. Seventy-five mice were randomly assigned to five groups. Gene expression and histological analyses of MIF and its receptors, and determine the expression of osteogenic markers in vivo.

RESULTS

The results revealed a positive and concentration-dependent effect of MIF on the osteogenic differentiation of TDSCs. Furthermore, an ROS/HIF-1α/MIF positive loop was detected in the simulated early trauma hypoxic microenvironment, resulting in a 3 to 4 folds increase in MIF expression levels. MIF was also found to enhance double the expression levels of markers associated with bone and cartilage at the site of injury, consequently facilitating the development of HO, which was thought to be associated with the activation of the Wnt/β-catenin pathway.

CONCLUSION

MIF, which mediates the ROS/HIF-1α/MIF positive feedback loop during the hypoxic phase of HO, triggers the Wnt/β-catenin signaling pathway to enhance the osteogenic differentiation and formation of HO in TDSCs.

Single-cell RNA-sequencing analysis of immune and mesenchymal cell crosstalk in the developing enthesis

Autoimmunity underlies many painful disorders, such as enthesopathies, which localize to the enthesis. From infiltration of the synovium and axial skeleton by B cells, to disturbances in the ratio of M1/M2 enthesis macrophages, to CD8 + T cell mediated inflammation, autoimmune dysregulation is becoming increasingly well characterized in enthesopathies. Tissue resident B cells, macrophages, neutrophils, and T cells have also been localized in healthy human entheses. However, the potential developmental origins, presence, and role of immune cells (ICs) in enthesis development is not known. Here, we use single-cell RNA-sequencing analysis to describe IC subtypes present in the enthesis before, during, and after mineralization, and to infer regulatory interactions between ICs and mesenchymal cells (MCs). We report the presence of nine phenotypically distinct IC subtypes, including B cells, macrophages, neutrophils, and T cells. We find that specific IC subtypes may promote MC-proliferation and differentiation, and that MCs may regulate IC phenotype and autoimmunity. Our findings suggest that bidirectional regulatory interactions between ICs and MCs may be important to enthesis mineralization, and suggest that progenitor MCs have a unique ability to limit autoimmunity during development.

The role of MIF in periodontitis: A potential pathogenic driver, biomarker, and therapeutic target

OBJECTIVE

Periodontitis is an inflammatory disease that involves an imbalance in the oral microbiota, activation of inflammatory and immune responses, and alveolar bone destruction. Macrophage migration inhibitory factor (MIF) is a versatile cytokine involved in several pathological reactions, including inflammatory processes and bone destruction, both of which are characteristics of periodontitis. While the roles of MIF in cancer and other immune diseases have been extensively characterized, its role in periodontitis remains inconclusive.

RESULTS

In this review, we describe a comprehensive analysis of the potential roles of MIF in periodontitis from the perspective of immune response and bone regulation at the cellular and molecular levels. Moreover, we discuss its potential reliability as a novel diagnostic and therapeutic target for periodontitis.

CONCLUSION

This review can aid dental researchers and clinicians in understanding the current state of MIF-related pathogenesis, diagnosis, and treatment of periodontitis.

Hypoxic Extracellular Matrix Preserves Its Competence after Expansion of Human MSCs under Physiological Hypoxia In Vitro

Tissue-relevant O2 levels are considered as an important tool for the preconditioning of multipotent mesenchymal stromal cells (MSCs) for regenerative medicine needs. The present study investigated the quality and functions of the extracellular matrix (ECM) of MSCs under low O2 levels. Human adipose tissue-derived MSCs were continuously expanded under normoxia (20% O2, N) or "physiological" hypoxia (5% O2, Hyp). Decellularized ECM (dcECM) was prepared. The structure of the dcECM was analyzed using confocal laser and scanning electron microscopy. Collagen, dcECM-N, and dcECM-Hyp were recellularized with MSC-N and further cultured at normoxia. The efficacy of adhesion, spreading, growth, osteogenic potential, and paracrine activity of recellularized MSC-N were evaluated. At low O2, the dcECM showed an increased alignment of fibrillar structures and provided accelerated spreading of MSC-N, indicating increased dcECM-Hyp stiffness. We described O2-dependent "ECM-education" of MSC-N when cultured on dcECM-Hyp. This was manifested as attenuated spontaneous osteo-commitment, increased susceptibility to osteo-induction, and a shift in the paracrine profile. It has been suggested that the ECM after physiological hypoxia is able to ensure the maintenance of a low-commitment state of MSCs. DcECM, which preserves the competence of the natural microenvironment of cells and is capable of "educating" others, appears to be a prospective tool for guiding cell modifications for cell therapy and tissue engineering.

Stem Cell Membrane-Coated Microribbon Scaffolds Induce Regenerative Innate and Adaptive Immune Responses in a Critical-Size Cranial Bone Defect Model

Naturally-derived cell membranes have shown great promise in functionalizing nanoparticles to enhance biointerfacing functions for drug delivery applications. However, its potential for functionalizing macroporous scaffolds to enhance tissue regeneration in vivo remains unexplored. Engineering scaffolds with immunomodulatory functions represents an exciting strategy for tissue regeneration but is largely limited to soft tissues. Critical-sized bone defects cannot heal on their own, and the role of adaptive immune cells in scaffold-mediated healing of cranial bone defects remains largely unknown. Here, mensenchymal stem cell membrane (MSCM)-coated microribbon (µRB) scaffolds for treating critical size cranial bone defects via targeting immunomodulation are reported. Confocal imaging and proteomic analyses are used to confirm successful coating and characterize the compositions of cell membrane coating. It is demonstrated that MSCM coating promotes macrophage (Mφ) polarization toward regenerative phenotype, induces CD8+ T cell apoptosis, and enhances regulatory T cell differentiation in vitro and in vivo. When combined with a low dosage of BMP-2, MSCM coating further accelerates bone regeneration and suppresses inflammation. These results establish cell membrane-coated microribbon scaffolds as a promising strategy for treating critical size bone defects via immunomodulation. The platform may be broadly used with different cell membranes and scaffolds to enhance regeneration of multiple tissue types.

Pathogenesis of acquired heterotopic ossification: Risk factors, cellular mechanisms, and therapeutic implications

Heterotopic ossification (HO), including hereditary and acquired HO, is the formation of extraskeletal bone in skeletal muscle and surrounding soft tissues. Acquired HO is often caused by range of motion, explosion injury, nerve injury or burns. Severe HO can lead to pain and limited joint activity, affecting functional rehabilitation and quality of life. Increasing evidence shows that inflammatory processes and mesenchymal stem cells (MSCs) can drive HO. However, explicit knowledge about the specific mechanisms that result in HO and related cell precursors is still limited. Moreover, there are no effective methods to prevent or reduce HO formation. In this review, we provide an update of known risk factors and relevant cellular origins for HO. In particular, we focus on the underlying mechanisms of MSCs in acquired HO, which follow the osteogenic program. We also discuss the latest therapeutic value and implications for acquired HO. Our review highlights the current gaps in knowledge regarding the pathogenesis of acquired HO and identifies potential targets for the prevention and treatment of HO.

Deep Insight into the Role of MIF in Spondyloarthritis

PURPOSE OF REVIEW

Pathological roles of macrophage migration inhibitory factor (MIF) have recently been demonstrated in spondyloarthritis (SpA) preclinical models, identifying MIF as a new treatment target for SpA. However, the specific contribution of MIF and therapeutic potential of MIF-targeted therapies to various tissue types affected by SpA are not well delineated.

RECENT FINDINGS

MIF and its cognate receptor CD74 are extensively involved in the pathogenesis of SpA including inflammation in the spine, joint, eyes, skin, and gut. The majority of the current evidence has consistently shown that MIF drives the inflammation in these distinct anatomical sites. In preclinical models, genetic deletion or blockade of MIF reduces the severity of inflammation. Although MIF is generally an upstream cytokine which regulates downstream effector cytokines, MIF also intensifies type 3 immunity by promoting helper T 17 (Th17) plasticity. MIF- or CD74-targeted therapies have also reported to be well tolerated in clinical trials for other diseases. Recent findings suggest that MIF-CD74 axis is a new therapeutic target for SpA to improve various clinical features. Clinical trials for MIF- or CD74-targeted therapies for SpA patients are warranted.

Extracellular Vesicles Derived from Primed Mesenchymal Stromal Cells Loaded on Biphasic Calcium Phosphate Biomaterial Exhibit Enhanced Macrophage Polarization

Mesenchymal stromal cells (MSC) loaded on biphasic calcium phosphate biomaterial (MSC + BCP) have been used as an advanced therapy medicinal product to treat complex maxillofacial bone defects in patients. Further, MSC-derived extracellular vesicles (EVs) are established vehicles of paracrine factors, supporting inter-cellular communication between MSC and other interacting cell types, such as monocytes/macrophages. However, the information about the immunomodulatory potential of EVs derived from MSC and biomaterial constructs (MSC + BCP:EV) and inflammatory primed constructs (MSCp + BCP:EV) are scarce. Hence, we isolated and characterized EVs from these different systems, and compared their cytokine contents with plastic-adherent MSC-derived EVs (MSC:EV). When EVs from all three MSC systems were added to the primary blood-derived macrophages in vitro, significantly higher numbers of M0 (naive) macrophages shifted to M2-like (anti-inflammatory) by MSCp + BCP:EV treatment. Further, this treatment led to enhanced switching of M1 polarized macrophages to M2 polarized, and conversely, M2 to M1, as evaluated by determining the M1/M2 ratios after treatment. The enhanced macrophage modulation by MSCp + BCP:EV was attributed to their higher immunomodulatory (TNFα, IL1β, IL5), angiogenic (VEGF), and chemokine-rich (RANTES, MCP1, MIP1β) cytokine cargo. In conclusion, we successfully isolated and characterized EVs from MSC + BCP constructs and demonstrated that, depending upon the tissue microenvironment, these EVs contribute towards modulating the macrophage-mediated inflammation and healing responses. The study offers new insights into the use of biomaterial-induced EVs for MSC secretome delivery, as a step towards future 'cell-free' bone regenerative therapies.