Bone regeneration with micro/nano hybrid-structured biphasic calcium phosphate bioceramics at segmental bone defect and the induced immunoregulation of MSCs

Acemannan coated, cobalt-doped biphasic calcium phosphate nanoparticles for immunomodulation regulated bone regeneration

Biomaterials are used as scaffolds in bone regeneration to facilitate the restoration of bone tissues. The local immune microenvironment affects bone repair but the role of immune response in biomaterial-facilitated osteogenesis has been largely overlooked and it presents a major knowledge gap in the field. Nanomaterials that can modulate M1 to M2 macrophage polarization and, thus, promote bone repair are known. This study investigates a novel approach to accelerate bone healing by using acemannan coated, cobalt-doped biphasic calcium phosphate nanoparticles to promote osteogenesis and modulate macrophage polarization to provide a prohealing microenvironment for bone regeneration. Different concentrations of cobalt were doped in biphasic calcium phosphate nanoparticles, which were further coated with acemannan polymer and characterized. The nanoparticles showed >90% cell viability and enhanced cell proliferation along with osteogenic differentiation as demonstrated by the enhanced alkaline phosphatase activity and osteogenic calcium deposition. The morphology of MC3T3-E1 cells remained unchanged even after treatment with nanoparticles. Acemannan coated nanoparticles were also able to decrease the expression of M1 markers, iNOS, and CD68 and enhance the expression of M2 markers, CD206, CD163, and Arg-1 as indicated by RT-qPCR, flow cytometry, and ICC studies. The findings show that acemannan coated nanoparticles can create a supportive immune milieu by inducing and promoting the release of osteogenic markers, and by causing a reduction in inflammatory markers, thus helping in efficient bone regeneration. As per our knowledge, this is the first study showing the combined effect of acemannan and cobalt for bone regeneration using immunomodulation. The work presents a novel approach for enhancing osteogenesis and macrophage polarization, thus, offering a potent strategy for effective bone regeneration.

3D-printed tri-element-doped hydroxyapatite/ polycaprolactone composite scaffolds with antibacterial potential for osteosarcoma therapy and bone regeneration

The resection of malignant osteosarcoma often results in large segmental bone defects, and the residual cells can facilitate recurrence. Consequently, the treatment of osteosarcoma is a major challenge in clinical practice. The ideal goal of treatment for osteosarcoma is to eliminate it thoroughly, and repair the resultant bone defects as well as avoid bacterial infections. Herein, we fabricated a selenium/strontium/zinc-doped hydroxyapatite (Se/Sr/Zn-HA) powder by hydrothermal method, and then employed it with polycaprolactone (PCL) as ink to construct composite scaffolds through 3D printing, and finally introduced them in bone defect repair induced by malignant osteosarcoma. The resultant composite scaffolds integrated multiple functions involving anti-tumor, osteogenic, and antibacterial potentials, mainly attributed to the anti-tumor effects of SeO32-, osteogenic effects of Sr2+ and Zn2+, and antibacterial effects of SeO32- and Zn2+. In vitro studies confirmed that Se/Sr/Zn-HA leaching solution could induce apoptosis of osteosarcoma cells, differentiation of MSCs, and proliferation of MC3T3-E1 while showing excellent antibacterial properties. In vivo tests demonstrated that Se/Sr/Zn-HA could significantly suppress tumors after 8 days of injection, and the Se/Sr/Zn-HA-PCLs scaffold repaired femoral defects effectively after 3 months of implantation. Summarily, the Se/Sr/Zn-HA-PCLs composite scaffolds developed in this study were effective for tumor treatment, bone defect repair, and post-operative anti-infection, which provided a great potential to be a facile therapeutic material for osteosarcoma resection.

Manganese Enhances the Osteogenic Effect of Silicon-Hydroxyapatite Nanowires by Targeting T Lymphocyte Polarization

Biomaterials encounter considerable challenges in extensive bone defect regeneration. The amelioration of outcomes may be attainable through the orchestrated modulation of both innate and adaptive immunity. Silicon-hydroxyapatite, for instance, which solely focuses on regulating innate immunity, is inadequate for long-term bone regeneration. Herein, extra manganese (Mn)-doping is utilized for enhancing the osteogenic ability by mediating adaptive immunity. Intriguingly, Mn-doping engenders heightened recruitment of CD4+ T cells to the bone defect site, concurrently manifesting escalated T helper (Th) 2 polarization and an abatement in Th1 cell polarization. This consequential immune milieu yields a collaborative elevation of interleukin 4, secreted by Th2 cells, coupled with attenuated interferon gamma, secreted by Th1 cells. This orchestrated interplay distinctly fosters the osteogenesis of bone marrow stromal cells and effectuates consequential regeneration of the mandibular bone defect. The modulatory mechanism of Th1/Th2 balance lies primarily in the indispensable role of manganese superoxide dismutase (MnSOD) and the phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK). In conclusion, this study highlights the transformative potential of Mn-doping in amplifying the osteogenic efficacy of silicon-hydroxyapatite nanowires by regulating T cell-mediated adaptive immunity via the MnSOD/AMPK pathway, thereby creating an anti-inflammatory milieu favorable for bone regeneration.

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.

Interaction of Ceramic Implant Materials with Immune System

The immuno-compatibility of implant materials is a key issue for both initial and long-term implant integration. Ceramic implants have several advantages that make them highly promising for long-term medical solutions. These beneficial characteristics include such things as the material availability, possibility to manufacture various shapes and surface structures, osteo-inductivity and osteo-conductivity, low level of corrosion and general biocompatibility. The immuno-compatibility of an implant essentially depends on the interaction with local resident immune cells and, first of all, macrophages. However, in the case of ceramics, these interactions are insufficiently understood and require intensive experimental examinations. Our review summarizes the state of the art in variants of ceramic implants: mechanical properties, different chemical modifications of the basic material, surface structures and modifications, implant shapes and porosity. We collected the available information about the interaction of ceramics with the immune system and highlighted the studies that reported ceramic-specific local or systemic effects on the immune system. We disclosed the gaps in knowledge and outlined the perspectives for the identification to ceramic-specific interactions with the immune system using advanced quantitative technologies. We discussed the approaches for ceramic implant modification and pointed out the need for data integration using mathematic modelling of the multiple ceramic implant characteristics and their contribution for long-term implant bio- and immuno-compatibility.

Nanowhiskers Orchestrate Bone Formation and Bone Defect Repair by Modulating Immune Cell Behavior

Immunomodulatory biomaterials have emerged as promising treatment agents for bone defects. However, it is unclear how such biomaterials control immune cell behaviors to facilitate large-segment bone defect repair. Herein, we fabricated biphasic calcium phosphate ceramics with nanowhisker structures to explore the immunoregulation features and influence on large-segment bone defect repair. We found that the nanowhisker structures markedly facilitated large-segment bone defect repair by promoting bone regeneration and scaffold resorption. Our in vitro experiment and transcriptomic analysis showed that mechanical stress derived from nanowhisker structures may activate the transcription of Egr-1 to induce early switch of macrophage phenotype to M2, which could not only facilitate osteogenic differentiation of BMSCs but also enhance the expression of osteoclast differentiation-regulating genes of M2 macrophage. In vivo study showed that the nanowhisker structures relieved local inflammatory responses by inducing early switch of macrophage phenotype from M1 to M2, which resulted in accelerated osteoclastogenesis for biomaterial resorption and osteogenesis for ectopic bone formation. Hence, we presume that nanowhisker structures may orchestrate bone formation and material resorption coupling to facilitate large-segment bone defect repair by controlling the switch of macrophage phenotype. This study provides new insight into the designing of immunomodulatory tissue engineering biomaterials for treating large-segment bone defects.

Lactoferrin Mediates Enhanced Osteogenesis of Adipose-Derived Stem Cells: Innovative Molecular and Cellular Therapy for Bone Repair

A prospective source of stem cells for bone tissue engineering is adipose-derived stem cells (ADSCs), and BMP-2 has been proven to be highly effective in promoting the osteogenic differentiation of stem cells. Rarely has research been conducted on the impact of lactoferrin (LF) on ADSCs' osteogenic differentiation. As such, in this study, we examined the effects of LF and BMP-2 to assess the ability of LF to stimulate ADSCs' osteogenic differentiation. The osteogenic medium was supplemented with the LF at the following concentrations to culture ADSCs: 0, 10, 20, 50, 100, and 500 μg/mL. The Cell Counting Kit-8 (CCK-8) assay was used to measure the proliferation of ADSCs. Calcium deposition, alkaline phosphatase (ALP) staining, real-time polymerase chain reaction (RT-PCR), and an ALP activity assay were used to establish osteogenic differentiation. RNA sequencing analysis was carried out to investigate the mechanism of LF boosting the osteogenic development of ADSCs. In the concentration range of 0-100 μg/mL, LF concentration-dependently increased the proliferative vitality and osteogenic differentiation of ADSCs. At a dose of 500 μg/mL, LF sped up and enhanced differentiation, but inhibited ADSCs from proliferating. LF (100 and 500 μg/mL) produced more substantial osteoinductive effects than BMP-2. The PI3 kinase/AKT (PI3K/AKT) and IGF-R1 signaling pathways were significantly activated in LF-treated ADSCs. The in vitro study results showed that LF could effectively promote osteogenic differentiation of ADSCs by activating the PI3K/AKT and IGF-R1 pathways. In our in vitro investigation, an LF concentration of 100 μg/mL was optimal for osteoinduction and proliferation. Our study suggests that LF is an attractive alternative to BMP-2 in bone tissue engineering. As a bioactive molecule capable of inducing adipose stem cells to form osteoblasts, LF is expected to be clinically used in combination with biomaterials as an innovative molecular and cellular therapy to promote bone repair.

Biomaterial-assisted tumor therapy: A brief review of hydroxyapatite nanoparticles and its composites used in bone tumors therapy

Malignant bone tumors can inflict significant damage to affected bones, leaving patients to contend with issues like residual tumor cells, bone defects, and bacterial infections post-surgery. However, hydroxyapatite nanoparticles (nHAp), the principal inorganic constituent of natural bone, possess numerous advantages such as high biocompatibility, bone conduction ability, and a large surface area. Moreover, nHAp's nanoscale particle size enables it to impede the growth of various tumor cells via diverse pathways. This article presents a comprehensive review of relevant literature spanning the past 2 decades concerning nHAp and bone tumors. The primary goal is to explore the mechanisms responsible for nHAp's ability to hinder tumor initiation and progression, as well as to investigate the potential of integrating other drugs and components for bone tumor diagnosis and treatment. Lastly, the article discusses future prospects for the development of hydroxyapatite materials as a promising modality for tumor therapy.

Influence of Bone Substitutes on Mesenchymal Stromal Cells in an Inflammatory Microenvironment

Bone regeneration is driven by mesenchymal stromal cells (MSCs) via their interactions with immune cells, such as macrophages (MPs). Bone substitutes, e.g., bi-calcium phosphates (BCPs), are commonly used to treat bone defects. However, little research has focused on MSC responses to BCPs in the context of inflammation. The objective of this study was to investigate whether BCPs influence MSC responses and MSC-MP interactions, at the gene and protein levels, in an inflammatory microenvironment. In setup A, human bone marrow MSCs combined with two different BCP granules (BCP 60/40 or BCP 20/80) were cultured with or without cytokine stimulation (IL1β + TNFα) to mimic acute inflammation. In setup B, U937 cell-line-derived MPs were introduced via transwell cocultures to setup A. Monolayer MSCs with and without cytokine stimulation served as controls. After 72 h, the expressions of genes related to osteogenesis, healing, inflammation and remodeling were assessed in the MSCs via quantitative polymerase chain reactions. Additionally, MSC-secreted cytokines related to healing, inflammation and chemotaxis were assessed via multiplex immunoassays. Overall, the results indicate that, under both inflammatory and non-inflammatory conditions, the BCP granules significantly regulated the MSC gene expressions towards a pro-healing genotype but had relatively little effect on the MSC secretory profiles. In the presence of the MPs (coculture), the BCPs positively regulated both the gene expression and cytokine secretion of the MSCs. Overall, similar trends in MSC responses were observed with BCP 60/40 and BCP 20/80. In summary, within the limits of in vitro models, these findings suggest that the presence of BCP granules at a surgical site may not necessarily have a detrimental effect on MSC-mediated wound healing, even in the event of inflammation.

Core-Shell Structured Porous Calcium Phosphate Bioceramic Spheres for Enhanced Bone Regeneration

Adequate new bone regeneration in bone defects has always been a challenge as it requires excellent and efficient osteogenesis. Calcium phosphate (CaP) bioceramics, including hydroxyapatite (HA) and biphasic calcium phosphates (BCPs), have been extensively used in clinical bone defect filling due to their good osteoinductivity and biodegradability. Here, for the first time, we designed and fabricated two porous CaP bioceramic granules with core-shell structures, named in accordance with their composition as BCP@HA and HA@BCP (core@shell). The spherical shape and the porous structure of these granules were achieved by the calcium alginate gel molding technology combined with a H₂O₂ foaming process. These granules could be stacked to build a porous structure with a porosity of 65-70% and a micropore size distribution between 150 and 450 μm, which is reported to be good for new bone ingrowth. In vitro experiments confirmed that HA@BCP bioceramic granules could promote the proliferation and osteogenic ability when cocultured with bone marrow mesenchymal stem cells, while inhibiting the differentiation of RAW264.7 cells into osteoclasts. In vivo, 12 weeks of implantation in a critical-sized femoral bone defect animal model showed a higher bone volume fraction and bone mineral density in the HA@BCP group than in the BCP@HA or pure HA or BCP groups. From histological analysis, we discovered that the new bone tissue in the HA@BCP group was invading from the surface to the inside of the granules, and most of the bioceramic phase was replaced by the new bone. A higher degree of vascularization at the defect region repaired by HA@BCP was revealed by 3D microvascular perfusion angiography in terms of a higher vessel volume fraction. The current study demonstrated that the core-shell structured HA@BCP bioceramic granules could be a promising candidate for bone defect repair.

Calcium Phosphate-Based Biomaterials for Bone Repair

Traumatic, tumoral, and infectious bone defects are common in clinics, and create a big burden on patient's families and society. Calcium phosphate (CaP)-based biomaterials have superior properties and have been widely used for bone defect repair, due to their similarities to the inorganic components of human bones. The biological performance of CaPs, as a determining factor for their applications, are dependent on their physicochemical properties. Hydroxyapatite (HAP) as the most thermally stable crystalline phase of CaP is mostly used in the form of ceramics or composites scaffolds with polymers. Nanostructured CaPs with large surface areas are suitable for drug/gene delivery systems. Additionally, CaP scaffolds with hierarchical nano-/microstructures have demonstrated excellent ability in promoting bone regeneration. This review focuses on the relationships and interactions between the physicochemical/biological properties of CaP biomaterials and their species, sizes, and morphologies in bone regeneration, including synthesis strategies, structure control, biological behavior, and the mechanisms of CaP in promoting osteogenesis. This review will be helpful for scientists and engineers to further understand CaP-based biomaterials (CaPs), and be useful in developing new high-performance biomaterials for bone repair.

Bioinspired Laminated Bioceramics with High Toughness for Bone Tissue Engineering

For the research of biomaterials in bone tissue engineering, it is still a challenge to fabricate bioceramics that overcome brittleness while maintaining the great biological performance. Here, inspired by the toughness of natural materials with hierarchical laminated structure, we presented a directional assembly-sintering approach to fabricate laminated MXene/calcium silicate-based (L-M/CS) bioceramics. Benefiting from the orderly laminated structure, the L-M/CS bioceramics exhibited significantly enhanced toughness (2.23 MPa·m^1/2) and high flexural strength (145 MPa), which were close to the mechanical properties of cortical bone. Furthermore, the L-M/CS bioceramics possessed more suitable degradability than traditional CaSiO₃ bioceramics due to the newly formed CaTiSiO₅ after sintering. Moreover, the L-M/CS bioceramics showed good biocompatibility and could stimulate the expression of osteogenesis-related genes. The mechanism of promoting osteogenic differentiation had been shown to be related to the Wnt signaling pathway. This work not only fabricated calcium silicate-based bioceramics with excellent mechanical and biological properties for bone tissue engineering but also provided a strategy for the combination of bionics and bioceramics.

Exosomal PD-L1 induces osteogenic differentiation and promotes fracture healing by acting as an immunosuppressant

A moderate inflammatory response at the early stages of fracture healing is necessary for callus formation. Over-active and continuous inflammation, however, impairs fracture healing and leads to excessive tissue damage. Adequate fracture healing could be promoted through suppression of local over-active immune cells in the fracture site. In the present study, we achieved an enriched concentration of PD-L1 from exosomes (Exos) of a genetically engineered Human Umbilical Vein Endothelial Cell (HUVECs), and demonstrated that exosomes overexpressing PD-L1 specifically bind to PD-1 on the T cell surface, suppressing the activation of T cells. Furthermore, exosomal PD-L1 induced Mesenchymal Stem Cells (MSCs) towards osteogenic differentiation when pre-cultured with T cells. Moreover, embedding of Exos into an injectable hydrogel allowed Exos delivery to the surrounding microenvironment in a time-released manner. Additionally, exosomal PD-L1, embedded in a hydrogel, markedly promoted callus formation and fracture healing in a murine model at the early over-active inflammation phase. Importantly, our results suggested that activation of T cells in the peripheral lymphatic tissues was inhibited after local administration of PD-L1-enriched Exos to the fracture sites, while T cells in distant immune organs such as the spleen were not affected. In summary, this study provides the first example of using PD-L1-enriched Exos for bone fracture repair, and highlights the potential of Hydrogel@Exos systems for bone fracture therapy through immune inhibitory effects.

Preparation of BMP-2/PDA-BCP Bioceramic Scaffold by DLP 3D Printing and its Ability for Inducing Continuous Bone Formation

Digital light processing (DLP)-based 3D printing is suitable to fabricate bone scaffolds with small size and high precision. However, the published literature mainly deals with the fabrication procedure and parameters of DLP printed bioceramic scaffold, but lacks the subsequent systematic biological evaluations for bone regeneration application. In this work, a biphasic calcium phosphate (BCP) macroporous scaffold was constructed by DLP-based 3D printing technique. Furthermore, bone morphogenetic protein-2 (BMP-2) was facilely incorporated into this scaffold through a facile polydopamine (PDA) modification process. The resultant scaffold presents an interconnected porous structure with pore size of ∼570 μm, compressive strength (∼3.6 MPa), and the self-assembly Ca-P/PDA nanocoating exhibited excellent sustained-release property for BMP-2. Notably, this BMP-2/PDA-BCP scaffold presents favorable effects on the adhesion, proliferation, osteogenic differentiation, and mineralization of bone marrow stromal cells (BMSCs). Furthermore, in vivo experiments conducted on rats demonstrated that the scaffolds could induce cell layer aggregation adjacent to the scaffolds and continuous new bone generation within the scaffold. Collectively, this work demonstrated that the BMP-2/PDA-BCP scaffold is of immense potential to treat small craniofacial bone defects in demand of high accuracy.

[Osteoimmunomodulatory effects of inorganic biomaterials in the process of bone repair]

OBJECTIVE

To review the osteoimmunomodulatory effects and related mechanisms of inorganic biomaterials in the process of bone repair.

METHODS

A wide range of relevant domestic and foreign literature was reviewed, the characteristics of various inorganic biomaterials in the process of bone repair were summarized, and the osteoimmunomodulatory mechanism in the process of bone repair was discussed.

RESULTS

Immune cells play a very important role in the dynamic balance of bone tissue. Inorganic biomaterials can directly regulate the immune cells in the body by changing their surface roughness, surface wettability, and other physical and chemical properties, constructing a suitable immune microenvironment, and then realizing dynamic regulation of bone repair.

CONCLUSION

Inorganic biomaterials are a class of biomaterials that are widely used in bone repair. Fully understanding the role of inorganic biomaterials in immunomodulation during bone repair will help to design novel bone immunomodulatory scaffolds for bone repair.

Strategies for advanced particulate bone substitutes regulating the osteo-immune microenvironment

The usage of bone substitute granule materials has improved the clinical results of alveolar bone deficiencies treatment and thus broadened applications in implant dentistry. However, because of the complicated mechanisms controlling the foreign body response, no perfect solution can avoid the fibrotic encapsulation of materials till now, which may impair the results of bone regeneration, even cause the implant materials rejection. Recently, the concept of 'osteoimmunology' has been stressed. The outcomes of bone regeneration are proved to be related to the bio-physicochemical properties of biomaterials, which allow them to regulate the biological behaviours of both innate and adaptive immune cells. With the development of single cell transcriptome, the truly heterogeneity of osteo-immune cells has been clarifying, which is helpful to overcome the limitations of traditional M1/M2 macrophage nomenclature and drive the advancements of particulate biomaterials applications. This review aims at introducing the mechanisms of optimal osseointegration regulated by immune systems and provides feasible strategies for the design of next generation 'osteoimmune-smart' particulate bone substitute materials in dental clinic.

Nano-Hydroxyapatite Bone Scaffolds with Different Porous Structures Processed by Digital Light Processing 3D Printing

The morphologies and structures of the scaffold have a significant influence on their mechanical and biological properties. In this work, different types of porous structures: Triply periodic minimal surface-Schwarz primitive (P), body-centered cubic, and cubic pore-shaped (CPS) hydroxyapatite scaffolds with ~70% porosity were fabricated through digital light processing (DLP) 3D printing technology. The compressive properties and in vitro cell evaluations such as cell proliferation and attachment morphology of these scaffolds were systematically compared. The results showed that the CPS scaffolds exhibited the highest compressive strength (~22.5 MPa) and modulus (~400 MPa). In addition, the CPS scaffolds also performed the most active cell metabolisms as compared to other two structures, which may account for the larger pore size and smaller curvature of the substrate. This study provides a general guidance for the fabrication and selection of porous bone scaffolds processed by DLP 3D printing.

Differential Expression Profiling of microRNAs in Human Placenta-Derived Mesenchymal Stem Cells Cocultured with Grooved Porous Hydroxyapatite Scaffolds

Scaffold materials used for bone defect repair are often limited by osteogenic efficacy. Moreover, microRNAs (miRNAs) are involved in regulating the expression of osteogenic-related genes. In previous studies, we verified the enhancement of osteogenesis using a grooved porous hydroxyapatite scaffold (HAG). In the present study, we analyzed the contribution of HAG to the osteogenic differentiation of human placenta-derived mesenchymal stem cells (hPMSCs) from the perspective of miRNA differential expression. Furthermore, results showed that miRNAs were differentially expressed in the osteogenic differentiation of hPMSCs cocultured with HAG. In detail, 16 miRNAs were significantly upregulated and 29 miRNAs were downregulated with HAG. In addition, bioinformatics analyses showed that the differentially expressed miRNAs were enriched in a variety of biological processes, including signal transduction, cell metabolism, cell junctions, cell development and differentiation, and that they were associated with osteogenic differentiation through axon guidance, mitogen-activated protein kinase, and the transforming growth factor beta signaling pathway. Furthermore, multiple potential target genes of these miRNAs were closely related to osteogenic differentiation. Importantly, overexpression of miR-146a-5p (an upregulated miRNA) promoted the osteogenic differentiation of hPMSCs, and miR-145-5p overexpression (a downregulated miRNA) inhibited the osteogenic differentiation of hPMSCs.

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.

Osteoporotic bone recovery by a bamboo-structured bioceramic with controlled release of hydroxyapatite nanoparticles

While most bone defects can be repaired spontaneously, the healing process can be complicated due to insufficient bone regeneration when osteoporosis occurs. Synthetic materials that intrinsically stimulate bone formation without inclusion of exogenous cells or growth factors represent a highly desirable alternative to current grafting strategies for the management of osteoporotic defects. Herein, we developed a series of hydroxyapatite bioceramics composed of a microwhiskered scaffold (wHA) reinforced with multiple layers of releasable hydroxyapatite nanoparticles (nHA). These novel bioceramics (nwHA) are tunable to optimize the loading amount of nHA for osteoporotic bone formation. The utility of nwHA bioceramics for the proliferation or differentiation of osteoporotic osteoblasts in vitro is demonstrated. A much more compelling response is seen when bioceramics are implanted in critical-sized femur defects in osteoporotic rats, as nwHA bioceramics promote significantly higher bone regeneration and delay adjacent bone loss. Moreover, the nwHA bioceramics loaded with a moderate amount of nHA can induce new bone formation with a higher degree of ossification and homogenization. Two types of osteogenesis inside the nwHA bioceramic pores were discovered for the first time, depending on the direction of growth of the new bone. The current study recommends that these tailored hybrid micro/nanostructured bioceramics represent promising candidates for osteoporotic bone repair.

Osteoimmune reaction caused by novel silicocarnotite bioceramic promoting osteogenesis through MAPK pathway

The host immune response to implant is a key factor in determining the fate of bone grafts, which is thought to be a regulator of tissue regeneration. Figuring out the...

Enhanced bone regenerative properties of calcium phosphate ceramic granules in rabbit posterolateral spinal fusion through a reduction of grain size

Osteoinductivity is a crucial factor to determine the success and efficiency of posterolateral spinal fusion (PLF) by employing calcium phosphate (Ca-P) bioceramics. In this study, three kinds of Ca-P ceramics with microscale to nanoscale gain size (BCP-control, BCP-micro and BCP-nano) were prepared and their physicochemical properties were characterized. BCP-nano had the spherical shape and nanoscale gain size, BCP-micro had the spherical shape and microscale gain size, and BCP-control (BAM®) had the irregular shape and microscale gain size. The obtained BCP-nano with specific nanotopography could well regulate in vitro protein adsorption and osteogenic differentiation of MC3T3 cells. In vivo rabbit PLF procedures further confirmed that nanotopography of BCP-nano might be responsible for the stronger bone regenerative ability comparing with BCP-micro and BCP-control. Collectedly, due to nanocrystal similarity with natural bone apatite, BCP-nano has excellent efficacy in guiding bone regeneration of PLF, and holds great potentials to become an alternative to standard bone grafts for future clinical applications.

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The nanocrystal of porous BCP ceramic spheres is similar to natural bone apatite.

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BCP nanoceramics is conducive to protein adsorption and osteogenic differentiation of MC3T3 cells.

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Osteoindutivity of BCP ceramics is a crucial factor to determine the sucess and efficiency of PLF.

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BCP ceramic spheres with nanotopography hold great potential in clinical PLF applications.

Nanostructural control of transparent hydroxyapatite nanoparticle films using a citric acid coordination technique

Hydroxyapatite (HA), as the main mineral component in hard tissues, has good biocompatibility. In particular, HA films are widely used as bioactive coatings for artificial bones and dental implants in biomedical fields. However, it is currently difficult to prepare a nanostructure-controlled HA film by a wet process for further applications. Herein, we report the synthesis of HA nanoparticles coordinated by citric acid (Cit/HA) based on the interactions between carboxylate and calcium ions to control the sizes and shapes of the hybrid nanoparticles, to improve their dispersibility in water and to eventually form uniform transparent films with nanospaces, and investigated the film formation mechanism. As compared with the well-known rod-like HA nanoparticles (size: 48 × 15 nm²), we successfully synthesized spherical and negatively charged Cit/HA nanoparticles (size: 25 × 23 nm²) to achieve highly transparent Cit/HA films using the spin-coating technique. The Cit/HA films had uniform and crack-free appearance. About the nanostructures, we found that the Cit/HA film surfaces had meso-scaled nanospaces with a diameter of 4.2 nm based on the regular arrangement of spherical nanoparticles, instead of the HA film with a nanospace diameter of 24.5 nm formed by non-uniform accumulation. Therefore, we successfully achieved the control of the nanospace sizes of the films with the nanoparticle arrangement and realized transparent nanoparticle film formation in a very simple way, which will provide more convenient bioceramic films for biomedical applications.

The Development Tendency of 3D-Printed Bioceramic Scaffolds for Applications Ranging From Bone Tissue Regeneration to Bone Tumor Therapy

Three-dimensional (3D) printing concept has been successfully employed in regenerative medicine to achieve individualized therapy due to its benefit of a rapid, accurate, and predictable production process. Traditional biocomposites scaffolds (SCF) are primarily utilised for bone tissue engineering; nevertheless, over the last few years, there has already been a dramatic shift in the applications of bioceramic (BCR) SCF. As a direct consequence, this study focused on the structural, degeneration, permeation, and physiological activity of 3D-printed BCR (3DP-B) SCF with various conformations and work systems (macros, micros, and nanos ranges), as well as their impacts on the mechanical, degeneration, porosity, and physiological activities. In addition, 3DP-B SCF are highlighted in this study for potential uses applied from bone tissue engineering (BTE) to bone tumor treatment. The study focused on significant advances in practical 3DP-B SCF that can be utilized for tumor treatment as well as bone tissue regeneration (BTR). Given the difficulties in treating bone tumors, these operational BCR SCF offer a lot of promise in mending bone defects caused by surgery and killing any remaining tumor cells to accomplish bone tumor treatment. Furthermore, a quick assessment of future developments in this subject was presented. The study not only summarizes recent advances in BCR engineering, but it also proposes a new therapeutic strategy focused on the extension of conventional ceramics' multifunction to a particular diagnosis.

A bimetallic load-bearing bioceramics of TiO2 @ ZrO2 integrated polycaprolactone fibrous tissue construct exhibits anti bactericidal effect and induces osteogenesis in MC3T3-E1 cells

Bioactive mesoporous binary metal oxide nanoparticles allied with polymeric scaffolds can mimic natural extracellular matrix because of their self-mineralized functional matrix. Herein, we developed fibrous scaffolds of polycaprolactone (PCL) integrating well-dispersed TiO₂@ZrO₂ nanoparticles (NPs) via electrospinning for a tissue engineering approach. The scaffold with 0.1 wt% of bioceramic (TiO₂@ZrO₂) shows synergistic effects on physicochemical and bioactivity suited to stem cell attachment/proliferation. The bioceramics-based scaffold shows excellent antibacterial activity that can prevent implant-associated infections. In addition, the TiO₂@ZrO₂ in scaffold serves as a stem cell microenvironment to accelerate cell-to-cell interactions, including cell growth, morphology/orientation, differentiation, and regeneration. The NPs in PCL exert superior biocompatibility on MC3T3-E1 cells inducing osteogenic differentiation. The ALP activity and ARS staining confirm the upregulation of bone-related proteins and minerals suggesting the scaffolds exhibit osteoinductive abilities and contribute to bone cell regeneration. Based on this result, the bimetallic oxide could become a novel bone ceramic tailor TiO₂@ZrO₂ composite tissue-construct and keep potential nanomaterials-based scaffold for bone tissue engineering strategy.

Calcium silicate enhances immunosuppressive function of MSCs to indirectly modulate the polarization of macrophages

Bioactive silicate ceramics (BSCs) have been widely reported to be able to induce bone tissue regeneration, but the underlying mechanisms have not been fully elucidated. Previous studies have reported that ionic products of BSCs can promote bone regeneration by directly simulating osteogenic differentiation of mesenchymal stem cells (MSCs) and modulating the polarization of macrophages to create a favorable inflammation microenvironment for initiating bone regeneration cascades. However, the immunomodulatory ability of MSCs also plays a critical role in bone regeneration but the effects of BSCs on the immunomodulatory ability of MSCs have been rarely investigated. This study aims to investigate the effects of ionic products of BSCs on the immunoregulatory ability of MSCs to further understand the mechanism of BSCs enhancing bone regeneration. Results showed that ionic products of calcium silicate (CS), one of the representative BSCs, could enhance the immunosuppressive function of human bone marrow mesenchymal stem cells (HBMSCs) by up-regulating the expression of immunosuppressive factors in HBMSCs via NF-κB pathway. In addition, CS-activated HBMSCs showed stronger stimulatory effects on M2 polarization of macrophages than CS ionic products. Furthermore, the macrophages educated by CS-activated HBMSCs showed stronger stimulatory effects on the early osteogenic differentiation of HBMSCs than the ones regulated by CS ionic products. These results not only provide further understanding on the mechanism of BSCs enhancing bone regeneration but also suggest that it is critical to consider the effects of biomaterials on the immunomodulatory function of the tissue forming cells when the immunomodulatory function of biomaterials is investigated.

Comparative characteristic study from bone marrow-derived mesenchymal stem cells

Tissue engineering has been extensively investigated and proffered to be a potential platform for novel tissue regeneration. The utilization of mesenchymal stem cells (MSCs) from various sources has been widely explored and compared. In this regard, MSCs derived from bone marrow have been proposed and described as a promising cell resource due to their high yield of isolated cells with colony-forming potential, self-renewal capacity, MSC surface marker expression, and multi-lineage differentiation capacities in vitro. However, there is evidence for bone marrow MSCs (BM-MSCs) both in vitro and in vivo from different species presenting identical and distinct potential stemness characteristics. In this review, the fundamental knowledge of the growth kinetics and stemness properties of BM-MSCs in different animal species and humans are compared and summarized. Finally, to provide a full perspective, this review will procure results of current information studies focusing on the use of BM-MSCs in clinical practice.

3D-Printed Multifunctional Polyetheretherketone Bone Scaffold for Multimodal Treatment of Osteosarcoma and Osteomyelitis

In this work, we developed the first 3D-printed polyetheretherketone (PEEK)-based bone scaffold with multi-functions targeting challenging bone diseases such as osteosarcoma and osteomyelitis. A 3D-printed PEEK/graphene nanocomposite scaffold was deposited with a drug-laden (antibiotics and/or anti-cancer drugs) hydroxyapatite coating. The graphene nanosheets within the scaffold served as effective photothermal agents that endowed the scaffold with on-demand photothermal conversion function under near-infrared laser irradiation. The bioactive hydroxyapatite coating significantly boosted the stem cell proliferation in vitro and promoted new bone growth in vivo. The presence of antibiotics and anti-cancer drugs enabled eradication of drug-resistant bacteria and ablation of osteosarcoma cancer cells, the treatment efficacy of which can be further enhanced by on-demand laser-induced heating. The promising results demonstrate the strong potential of our multi-functional scaffold in applications such as bone defect repair and multimodal treatment of osteosarcoma and osteomyelitis.

Strategies to address mesenchymal stem/stromal cell heterogeneity in immunomodulatory profiles to improve cell-based therapies

Mesenchymal stromal cells (MSCs) have gained immense attention over the past two decades due to their multipotent differentiation potential and pro-regenerative and immunomodulatory cytokine secretory profiles. Their ability to modulate the host immune system and promote tolerance has prompted several allogeneic and autologous hMSC-based clinical trials for the treatment of graft-versus-host disease and several other immune-induced disorders. However, clinical success beyond safety is still controversial and highly variable, with inconclusive therapeutic benefits and little mechanistic explanation. This clinical variability has been broadly attributed to inconsistent MSC sourcing, phenotypic characterization, variable potency, and non-standard isolation protocols, leading to functional heterogeneity among administered MSCs. Homogeneous MSC populations are proposed to yield more predictable, reliable biological responses and clinically meaningful properties relevant to cell-based therapies. Limited comparisons of heterogeneous MSCs with homogenous MSCs are reported. This review addresses this gap in the literature with a critical analysis of strategies aimed at decreasing MSC heterogeneity concerning their reported immunomodulatory profiles. STATEMENT OF SIGNIFICANCE: This review collates, summarizes, and critically analyzes published strategies that seek to improve homogeneity in immunomodulatory functioning MSC populations intended as cell therapies to treat immune-based disorders, such as graft-vs-host-disease. No such review for MSC therapies, immunomodulatory profiles and cell heterogeneity analysis is published. Since MSCs represent the most clinically studied experimental cell therapy platform globally for which there remains no US domestic marketing approval, insights into MSC challenges in therapeutic product development are imperative to providing solutions for immunomodulatory variabilities.

Modulating immune microenvironment during bone repair using biomaterials: Focusing on the role of macrophages

Bone is a self-regenerative tissue that can repair small defects and fractures. In large defects, bone tissue is unable to provide nutrients and oxygen for repair, and autologous grafting is used as the gold standard. As an alternative method, the bone tissue regeneration approach uses osteoconductive biomaterials to overcome bone graft disadvantages. However, biomaterials are considered as foreign components that can stimulate host immune responses. Although traditional principles have been aimed to minimize immune reactions, the design of biomaterials has steadily shifted toward creating an immunomodulatory microenvironment to harness immune cells and responses to repair damaged tissue. Among immune cells, macrophages secrete various immunomodulatory mediators and crosstalk with bone-forming cells and play key roles in bone tissue engineering. Macrophage polarization toward M1 and M2 subtypes mediate pro-inflammatory and anti-inflammatory responses, respectively, which are crucial for bone repairing at different stages. This review provides an overview of the crosstalk between various immune cells and biomaterials, macrophage polarization, and the effect of physicochemical properties of biomaterials on the immune responses, especially macrophages, in bone tissue engineering.

Repair calvarial defect of osteoporotic rats by berberine functionalized porous calcium phosphate scaffold

In this article, we propose a simple scheme of using berberine (BBR) to modify porous calcium phosphate ceramics (named PCPC). These BBR molecules regulate the crystallization of hydroxyapatite nanorods on PCPC. We found that these nanorods and the adsorbed BBR changed the interface micro-environment of PCPC by SEM images. The microenvironment of PCPC surface is essential for promoting BMSCs’ proliferation and differentiation. These results demonstrated that PCPC/BBR markedly improved the bone regeneration of osteoporosis rats. Moreover, PCPC/BBR had significantly increased the expression levels of ALP, osteocalcin and bone morphogenetic protein2 and RUNX2 in BMSCs originated from osteoporosis rats.

Advanced Strategies of Biomimetic Tissue-Engineered Grafts for Bone Regeneration

The failure to repair critical-sized bone defects often leads to incomplete regeneration or fracture non-union. Tissue-engineered grafts have been recognized as an alternative strategy for bone regeneration due to their potential to repair defects. To design a successful tissue-engineered graft requires the understanding of physicochemical optimization to mimic the composition and structure of native bone, as well as the biological strategies of mimicking the key biological elements during bone regeneration process. This review provides an overview of engineered graft-based strategies focusing on physicochemical properties of materials and graft structure optimization from macroscale to nanoscale to further boost bone regeneration, and it summarizes biological strategies which mainly focus on growth factors following bone regeneration pattern and stem cell-based strategies for more efficient repair. Finally, it discusses the current limitations of existing strategies upon bone repair and highlights a promising strategy for rapid bone regeneration.

Application of nanoparticles in bone tissue engineering; a review on the molecular mechanisms driving osteogenesis

The introduction of nanoparticles into bone tissue engineering strategies is beneficial to govern cell fate into osteogenesis and the regeneration of large bone defects. The present study explored the role of nanoparticles to advance osteogenesis with a focus on the cellular and molecular pathways involved. Pubmed, Pubmed Central, Embase, Scopus, and Science Direct databases were explored for those published articles relevant to the involvement of nanoparticles in osteogenic cellular pathways. As multifunctional compounds, nanoparticles contribute to scaffold-free and scaffold-based tissue engineering strategies to progress osteogenesis and bone regeneration. They regulate inflammatory responses and osteo/angio/osteoclastic signaling pathways to generate an osteogenic niche. Besides, nanoparticles interact with biomolecules, enhance their half-life and bioavailability. Nanoparticles are promising candidates to promote osteogenesis. However, the interaction of nanoparticles with the biological milieu is somewhat complicated, and more considerations are recommended on the employment of nanoparticles in clinical applications because of NP-induced toxicities.

Urine-derived stem cells loaded onto a chitosan-optimized biphasic calcium-phosphate scaffold for repairing large segmental bone defects in rabbits

The treatment of large segmental bone defects can be challenging for orthopedic surgeons. The development of bone tissue engineering technology, including the selection of seeding cells and the construction of scaffolds, provides a promising solution. In this study, we investigated osteogenic differentiation of human urine-derived stem cells (hUSCs, a newly identified class of stem cells), and developed a novel porous hybrid scaffold using biphasic calcium phosphate (BCP) bioceramic ornamented with chitosan sponges (CS). We combined hUSCs with a CS/BCP hybrid scaffold to construct tissue-engineered bone and evaluated whether the combination promotes bone regeneration in large segmental bone defects in rabbits. The study showed that hUSCs can differentiate into osteoblasts, and the hUSCs adhered, proliferated, and differentiated on CS/BCP hybrid scaffolds. Micro-computed tomography measurements, biomechanical detection, and histological analyses revealed that the combination of hUSCs and the CS/BCP hybrid scaffold enhanced bone regeneration more effectively compared with conventional pure BCP scaffolds, indicating that hUSCs can be used as a cell source for bone tissue engineering and that cell-scaffold-based biomimetic bone may be a promising approach to the repair of bone defects.

Gradient nanostructured titanium stimulates cell responses in vitro and enhances osseointegration in vivo

Background

Though titanium (Ti) is widely used as dental materials in the clinic, effective methods to treat Ti for higher surface biological activity still lack. Through Surface mechanical attrition treatment (SMAT) technology we could endow Ti with gradient nanostructured surface (GNS Ti). To investigate the biocompatibility of GNS Ti for its further application in dental implant field, we study the effects of GNS Ti on cell responses in vitro and osseointegration of the implant with surrounding bone tissues in vivo.

Methods

In this study, GNS Ti was fabricated by SMAT. In vitro experiment, we co-cultured GNS Ti with bone mesenchymal stem cells (BMSCs), surface characterization was detected by transmission electron microscope (TEM). Adhesion, proliferation and differentiation of BMSCs were evaluated by scanning electron microscope (SEM), MTT, flow cytometry (FCM), alkaline phosphatase (ALP) and osteocalcin (OCN) tests. In vivo experiment, the GNS Ti was implanted into the rabbit mandible. Osteogenesis and osseointegration were evaluated by Micro CT, toluidine blue staining, and immunohistochemical staining at 4, 8, and 12 weeks postoperatively.

Results

Both results showed that compared with the coarse grained (CG) Ti, the GNS Ti stimulated the adhesion, proliferation, and differentiation of BMSCs and improved osteogenesis and osseointegration.

Conclusions

This study indicates that gradient nanostructured Ti is a promising material for dental implant application.

Inflammation and biomaterials: role of the immune response in bone regeneration by inorganic scaffolds

The regulatory role of the immune system in maintaining bone homeostasis and restoring its functionality, when disturbed due to trauma or injury, has become evident in recent years. The polarization of macrophages, one of the main constituents of the immune system, into the pro-inflammatory or anti-inflammatory phenotype has great repercussions for cellular crosstalk and the subsequent processes needed for proper bone regeneration such as angiogenesis and osteogenesis. In certain scenarios, the damaged osseous tissue requires the placement of synthetic bone grafts to facilitate the healing process. Inorganic biomaterials such as bioceramics or bioactive glasses are the most widely used due to their resemblance to the mineral phase of bone and superior osteogenic properties. The immune response of the host to the inorganic biomaterial, which is of an exogenous nature, might determine its fate, leading either to active bone regeneration or its failure. Therefore, various strategies have been employed, like the modification of structural/chemical features or the incorporation of bioactive molecules, to tune the interplay with the immune cells. Understanding how these particular modifications impact the polarization of macrophages and further osteogenic and osteoclastogenic events is of great interest in view of designing a new generation of osteoimmunomodulatory materials that support the regeneration of osseous tissue during all stages of bone healing.

Programmed BMP-2 release from biphasic calcium phosphates for optimal bone regeneration

This study aimed to fabricate a multi-layered biphasic calcium phosphate (BCP) platform for programmed bone morphogenetic protein-2 (BMP-2) release, which means to block the initial burst release and promote releasing during the differentiation phase of osteogenic cells. And it is to confirm in vivo whether this platform has osteogenic inductivity even when extremely low doses of BMP-2 are loaded compared to the conventional soaking method. Our strategy consisted of preparing a multilayer coating on BCP to minimize the contact between BMP-2 and BCP and allow the loading of BMP-2. The multilayer, which is surface-modified on BCP, is composed of an organosilicate and a natural polymer-based layer-by-layer (LbL) film. We applied (3-Aminopropyl)triethoxysilane (APTES) as an organosilicate was used for amine-functionalized BCP and (collagen/heparin)₅ film was used to delay and sustain BMP-2 release. The coated multilayer not only reduced the initial burst release by more than 50% but also loaded more BMP-2. For in vivo experiment, histomorphometric analysis, it was observed that the BCP platform loaded with extremely low concentration BMP-2 (0.01 mg/ml) induced a significantly larger amount of new bones at 8 weeks compared to the conventional soaking method in the rabbit calvarium onlay graft model.

Artificial Bioaugmentation of Biomacromolecules and Living Organisms for Biomedical Applications

The synergistic union of nanomaterials with biomaterials has revolutionized synthetic chemistry, enabling the creation of nanomaterial-based biohybrids with distinct properties for biomedical applications. This class of materials has drawn significant scientific interest from the perspective of functional extension via controllable coupling of synthetic and biomaterial components, resulting in enhancement of the chemical, physical, and biological properties of the obtained biohybrids. In this review, we highlight the forefront materials for the combination with biomacromolecules and living organisms and their advantageous properties as well as recent advances in the rational design and synthesis of artificial biohybrids. We further illustrate the incredible diversity of biomedical applications stemming from artificially bioaugmented characteristics of the nanomaterial-based biohybrids. Eventually, we aim to inspire scientists with the application horizons of the exciting field of synthetic augmented biohybrids.

The State of the Art and Prospects for Osteoimmunomodulatory Biomaterials

The critical role of the immune system in host defense against foreign bodies and pathogens has been long recognized. With the introduction of a new field of research called osteoimmunology, the crosstalk between the immune and bone-forming cells has been studied more thoroughly, leading to the conclusion that the two systems are intimately connected through various cytokines, signaling molecules, transcription factors and receptors. The host immune reaction triggered by biomaterial implantation determines the in vivo fate of the implant, either in new bone formation or in fibrous tissue encapsulation. The traditional biomaterial design consisted in fabricating inert biomaterials capable of stimulating osteogenesis; however, inconsistencies between the in vitro and in vivo results were reported. This led to a shift in the development of biomaterials towards implants with osteoimmunomodulatory properties. By endowing the orthopedic biomaterials with favorable osteoimmunomodulatory properties, a desired immune response can be triggered in order to obtain a proper bone regeneration process. In this context, various approaches, such as the modification of chemical/structural characteristics or the incorporation of bioactive molecules, have been employed in order to modulate the crosstalk with the immune cells. The current review provides an overview of recent developments in such applied strategies.

Porous polyetheretherketone microcarriers fabricated via hydroxylation together with cell-derived mineralized extracellular matrix coatings promote cell expansion and bone regeneration

Porous microcarriers have aroused increasing attention recently by facilitating oxygen and nutrient transfer, supporting cell attachment and growth with sufficient cell seeding density. In this study, porous polyetheretherketone (PEEK) microcarriers coated with mineralized extracellular matrix (mECM), known for their chemical, mechanical and biological superiority, were developed for orthopedic applications. Porous PEEK microcarriers were derived from smooth microcarriers using a simple wet-chemistry strategy involving the reduction of carbonyl groups. This treatment simultaneously modified surface topology and chemical composition. Furthermore, the microstructure, protein absorption, cytotoxicity and bioactivity of the obtained porous microcarriers were investigated. The deposition of mECM through repeated recellularization and decellularization on the surface of porous MCs further promoted cell proliferation and osteogenic activity. Additionally, the mECM coated porous microcarriers exhibited excellent bone regeneration in a rat calvarial defect repair model in vivo, suggesting huge potential applications in bone tissue engineering.

Biphasic Calcium Phosphate Microparticles Mixed With Autologous Blood: Application for the Reconstruction of a Large Mandibular Bone Defect in a Dog

Large mandibular bone defects can be difficult to treat in dogs, with a high risk of mal or nonunion due to instability and risk of infection. This case report describes the use of autologous clotted blood mixed with biphasic calcium phosphate microparticles to fill a defect in a nonunion fracture and promote bone regeneration in a dog using a 2-stage surgical approach. This new method was designed and tried in a dog with a chronic, unstable mandibular fracture associated with a large sequestrum. Initial treatment involved debridement of the lesion, then the oral wound and oral vestibule were reconstructed in 2 layers. Four weeks later a second stage surgery allowed placement of a pre-contoured maxillofacial plate to bridge the defect, which was filled with a blood/biphasic calcium phosphate compound implant. Cone-beam computed tomography was used prior to the initial surgery for preoperative planning and 3-D printing of a mandibular template for plate contouring. CT was subsequently used to document the healing process, using a bone density measurement tool to assess bone regeneration. Radiographic evidence suggestive of osseointegration was observed within 6 months with effective filling of the defect and restoration of alveolar ridge continuity. A return to normal and atraumatic occlusion was considered excellent. Cone-beam computed tomography was found useful to document radiographic evidence of osseointegration, bone regrowth and remodeling. This case report is to serve as a proof-of-concept study and should be followed by a prospective evaluation.

Challenges and advances in clinical applications of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs), also known as mesenchymal stem cells, have been intensely investigated for clinical applications within the last decades. However, the majority of registered clinical trials applying MSC therapy for diverse human diseases have fallen short of expectations, despite the encouraging pre-clinical outcomes in varied animal disease models. This can be attributable to inconsistent criteria for MSCs identity across studies and their inherited heterogeneity. Nowadays, with the emergence of advanced biological techniques and substantial improvements in bio-engineered materials, strategies have been developed to overcome clinical challenges in MSC application. Here in this review, we will discuss the major challenges of MSC therapies in clinical application, the factors impacting the diversity of MSCs, the potential approaches that modify MSC products with the highest therapeutic potential, and finally the usage of MSCs for COVID-19 pandemic disease.

Effect of Hydrothermal Media on the in-situ Whisker Growth on Biphasic Calcium Phosphate Ceramics

BACKGROUND

There is still a big challenge to achieve a balance between mechanical characteristics and biological properties in biphasic calcium phosphate (BCP) ceramics.

PURPOSE

The present study focused on the in-situ whisker growth on BCP ceramics via different hydrothermal treatments and investigated the influences of these whiskers on the mechanical property and biological performance of the ceramics.

METHODS

Five kinds of BCP ceramics with in-situ whisker growth, ie, BCP-C, BCP-HNO3, BCP-Citric, BCP-NaOH, BCP-CaCl2 and BCP-Na3PO4 were fabricated by different hydrothermal treatments. The phase compositions, morphologies, crystal structures and mechanical strengths of the obtained BCP ceramics were firstly characterized. Then, the in vitro cell adhesion, proliferation and alkaline  phosphatase (ALP) activity of bone marrow stromal cells (BMSCs) on the BCP ceramics were evaluated. Lastly, the effects of in-situ whisker growth on the bone-like apatite formation abilities of BCP ceramics were also investigated by immersing them in simulated body fluid (SBF).

RESULTS

The results demonstrated that the hydrothermal conditions, especially the hydrothermal media, were crucial to determine the phase composition and morphology of the in-situ whisker. Especially among the five media used (HNO3, Citric, NaOH, CaCl2 and Na3PO4), the Na3PO4 treatment resulted in the shortest whisker with a unique hollow structure, and kept the original biphasic composition. All five kinds of whiskers increased the mechanical strength of BCP ceramics to some extent, and showed the good ability of bone-like apatite formation. The in vitro cell study demonstrated that the in-situ whisker growth had no adverse but even positive effect on the adhesion, proliferation and ALP activity of BMSCs.

CONCLUSION

Due to the growth of in-situ whiskers, the mechanical property and biological performance of the obtained BCP ceramics could increase simultaneously. Therefore, in-situ whiskers growth offers a promising strategy for the expanded application of BCP ceramics to meet the requirements of regenerative medicine.

Construction of a hierarchical micro & nanoporous surface for loading genistein on the composite of polyetheretherketone/tantalum pentoxide possessing antibacterial activity and accelerated osteointegration

Nanoporous tantalum pentoxide (NTP) particles with a pore size of about 10 nm were synthesized and blended with polyetheretherketone (PEEK) to fabricate a PEEK/NTP composite (PN). Subsequently, PN was treated by concentrated sulfuric acid to create a microporous surface (pore size of around 2 μm) on sulfonated PN (SPN), which formed a hierarchical micro & nanoporous surface. Compared with PN, the porous surface of SPN exhibited higher roughness, hydrophilicity, and surface energy. In addition, genistein (GT) was loaded into the porous surface of SPN (SPNG), which showed high GT loading capacity and sustained release of GT into phosphate buffered saline (PBS). Moreover, SPNG revealed excellent antibacterial activity, which inhibited bacterial (E. coli and S. aureus) growth in vitro due to the synergistic effects of both sulfonic acid (SO3H) groups and the sustained release of GT. Compared with PN, SPN significantly improved the adhesion, proliferation, and osteogenic differentiation of bone mesenchymal stem cells in vitro. Moreover, compared with SPN, SPNG further enhances the cell responses. Compared with PN, SPN remarkably improved bone formation and osteointegration in vivo. Furthermore, compared with SPN, SPNG further enhanced the osteointegration. In short, SPNG with a micro & nanoporous surface, SO3H groups, and the sustained release of GT exhibited antibacterial activity and accelerated osteointegration, which would have tremendous potential as drug-loaded implants for bone substitute.

Crystallization of carboplatin-loaded onto microporous calcium phosphate using high-vacuum method: Characterization and release study

Drug delivery systems are a new approach to increase therapeutic efficacy and to reduce the side effects of traditional treatments. Calcium phosphates (CaPs) have been studied as drug delivery systems, especially in bone diseases. However, each system has some particularities that depend on the physical and chemical characteristics of the biomaterials and drug interaction. In this work, granulated CaPs were used as a matrix for loading the anticancer drug carboplatin using the high-vacuum method. Five compositions were applied: hydroxyapatite (HA), β-tricalcium phosphate (β-TCP), biphasic HAp 60%/β-TCP 40% (BCP), β-TCP/MgO nanocomposite, and β-TCP/SiO2 nanocomposite. Carboplatin drug in 50, 60, and 70 mg/g was precipitated on the surface of CaPs. Morphological, chemical and surface modifications in the carboplatin-CaPs were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), backscattered electron microscopy (BSE), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transform infrared (FT-IR), and Raman spectroscopy. The characterization of the CaP-carboplatin biomaterials showed heterogeneous crystalline precipitation of the drug, and no morphological modifications of the CaPs biomaterials. The in vitro release profile of carboplatin from CaPs was evaluated by the ultraviolet-visible (UV-Vis) method. The curves showed a burst release of upon 60% of carboplatin loaded followed by a slow-release of the drug for the time of the study. The results were typical of a low-interaction system and physisorption mechanism. The high-vacuum method permitted to load the high amount of carboplatin drug on the surface of the biomaterials despite the low interaction between carboplatin and CaPs.

3D Printing of Bioinspired Biomaterials for Tissue Regeneration

Biological systems, which possess remarkable functions and excellent properties, are gradually becoming a source of inspiration for the fabrication of advanced tissue regeneration biomaterials due to their hierarchical structures and novel compositions. It would be meaningful to learn and transfer the characteristics of creatures to biomaterials design. However, traditional strategies cannot satisfy the design requirements of the complicated bioinspired materials for tissue regeneration. 3D printing, as a rapidly developing new technology that can accurately achieve multimaterial and multiscale fabrication, is capable of optimizing the fabrication of bioinspired materials with complex composition and structure. This review summarizes the recent developments in 3D-printed bioinspired biomaterials for multiple tissue regeneration, and especially highlights the progresses on i) traditional bioinspired designs for biomaterials fabrication, ii) biological composition inspired designs for the 3D-printed biomaterials, and iii) biological structure inspired designs for the 3D-printed biomaterials. Finally, the challenges and prospects for the development of 3D-printed bioinspired biomaterials are discussed.

A biomimetically hierarchical polyetherketoneketone scaffold for osteoporotic bone repair

Osteoporotic fractures are prevalent in society, and their incidence appears to be increasing as the worldwide population ages. However, conventional bone repair materials hardly satisfy the requirements for the repair of pathological fractures. Here, we developed a biomimetic polyetherketoneketone scaffold with a functionalized strontium-doped nanohydroxyapatite coating for osteoporotic bone defect applications. The scaffold has a hierarchically porous architecture and mechanical strength similar to that of osteoporotic trabecular bone. In vitro and in vivo studies demonstrated that the scaffold could promote osteoporotic bone regeneration and delay adjacent bone loss via regulating both osteoblasts and osteoclasts. In addition, the correlations between multiple preimplantation and postimplantation parameters were evaluated to determine the potential predictors of in vivo performance of the material. The current work not only develops a promising candidate for osteoporotic bone repair but also provides a viable approach for designing other functional biomaterials and predicting their translational value.

Human Teeth-Derived Bioceramics for Improved Bone Regeneration

Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) is one of the most promising candidates of the calcium phosphate family, suitable for bone tissue regeneration due to its structural similarities with human hard tissues. However, the requirements of high purity and the non-availability of adequate synthetic techniques limit the application of synthetic HAp in bone tissue engineering. Herein, we developed and evaluated the bone regeneration potential of human teeth-derived bioceramics in mice's defective skulls. The developed bioceramics were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (FE-SEM). The developed bioceramics exhibited the characteristic peaks of HAp in FTIR and XRD patterns. The inductively coupled plasma mass spectrometry (ICP-MS) technique was applied to determine the Ca/P molar ratio in the developed bioceramics, and it was 1.67. Cytotoxicity of the simulated body fluid (SBF)-soaked bioceramics was evaluated by WST-1 assay in the presence of human alveolar bone marrow stem cells (hABMSCs). No adverse effects were observed in the presence of the developed bioceramics, indicating their biocompatibility. The cells adequately adhered to the bioceramics-treated media. Enhanced bone regeneration occurred in the presence of the developed bioceramics in the defected skulls of mice, and this potential was profoundly affected by the size of the developed bioceramics. The bioceramics-treated mice groups exhibited greater vascularization compared to control. Therefore, the developed bioceramics have the potential to be used as biomaterials for bone regeneration application.