Evaluation of MC3T3-E1 Cell Osteogenesis in Different Cell Culture Media

Novel artificial tricalcium phosphate and magnesium composite graft facilitates angiogenesis in bone healing

BACKGROUND

Bone grafting is the standard treatment for critical bone defects, but autologous grafts have limitations like donor site morbidity and limited availability, while commercial artificial grafts may have poor integration with surrounding bone tissue, leading to delayed healing. Magnesium deficiency negatively impacts angiogenesis and bone repair. Therefore, incorporating magnesium into a synthetic biomaterial could provide an excellent bone substitute. This study aims to evaluate the morphological, mechanical, and biological properties of a calcium phosphate cement (CPC) sponge composed of tetracalcium phosphate (TTCP) and monocalcium phosphate monohydrate (MCPM), which could serve as an excellent bone substitute by incorporating magnesium.

METHODS

This study aims to develop biomedical materials composed mainly of TTCP and MCPM powder, magnesium powder, and collagen. The materials were prepared using a wet-stirred mill and freeze-dryer methods. The particle size, composition, and microstructure of the materials were investigated. Finally, the biological properties of these materials, including 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay for biocompatibility, effects on bone cell differentiation by alkaline phosphatase (ALP) activity assay and tartrate-resistant acid phosphatase (TRAP) activity assay, and endothelial cell tube formation assay for angiogenesis, were evaluated as well.

RESULTS

The data showed that the sub-micron CPC powder, composed of TTCP/MCPM in a 3.5:1 ratio, had a setting time shorter than 15 minutes and a compressive strength of 4.39±0.96 MPa. This reveals that the sub-micron CPC powder had an adequate setting time and mechanical strength. We found that the sub-micron CPC sponge containing magnesium had better biocompatibility, including increased proliferation and osteogenic induction effects without cytotoxicity. The CPC sponge containing magnesium also promoted angiogenesis.

CONCLUSION

In summary, we introduced a novel CPC sponge, which had a similar property to human bone promoted the biological functions of bone cells, and could serve as a promising material used in bone regeneration for critical bone defects.

In vitro evaluation of bone cell response to novel 3D-printable nanocomposite biomaterials for bone reconstruction

Critically-sized segmental bone defects represent significant challenges requiring grafts for reconstruction. 3D-printed synthetic bone grafts are viable alternatives to structural allografts if engineered to provide appropriate mechanical performance and osteoblast/osteoclast cell responses. Novel 3D-printable nanocomposites containing acrylated epoxidized soybean oil (AESO) or methacrylated AESO (mAESO), polyethylene glycol diacrylate, and nanohydroxyapatite (nHA) were produced using masked stereolithography. The effects of volume fraction of nHA and methacrylation of AESO on interactions of differentiated MC3T3-E1 osteoblast (dMC3T3-OB) and differentiated RAW264.7 osteoclast cells with 3D-printed nanocomposites were evaluated in vitro and compared with a control biomaterial, hydroxyapatite (HA). Higher nHA content and methacrylation significantly improved the mechanical properties. All nanocomposites supported dMC3T3-OB cells' adhesion and proliferation. Higher amounts of nHA enhanced cell adhesion and proliferation. mAESO in the nanocomposites resulted in greater adhesion, proliferation, and activity at day 7 compared with AESO nanocomposites. Excellent osteoclast-like cells survival, defined actin rings, and large multinucleated cells were only observed on the high nHA fraction (30%) mAESO nanocomposite and the HA control. Thus, mAESO-based nanocomposites containing higher amounts of nHA have better interactions with osteoblast-like and osteoclast-like cells, comparable with HA controls, making them a potential future alternative graft material for bone defect repair.

Methodology and Characterization of a 3D Bone Organoid Model Derived from Murine Cells

Here, we report on the development of a cost-effective, well-characterized three-dimensional (3D) model of bone homeostasis derived from commonly available stocks of immortalized murine cell lines and laboratory reagents. This 3D murine-cell-derived bone organoid model (3D-mcBOM) is adaptable to a range of contexts and can be used in conjunction with surrogates of osteoblast and osteoclast function to study cellular and molecular mechanisms that affect bone homeostasis in vitro or to augment in vivo models of physiology or disease. The 3D-mcBOM was established using a pre-osteoblast murine cell line, which was seeded into a hydrogel extracellular matrix (ECM) and differentiated into functional osteoblasts (OBs). The OBs mineralized the hydrogel ECM, leading to the deposition and consolidation of hydroxyapatite into bone-like organoids. Fourier-transform infrared (FTIR) spectroscopy confirmed that the mineralized matrix formed in the 3D-mcBOM was bone. The histological staining of 3D-mcBOM samples indicated a consistent rate of ECM mineralization. Type I collagen C-telopeptide (CTX1) analysis was used to evaluate the dynamics of OC differentiation and activity. Reliable 3D models of bone formation and homeostasis align with current ethical trends to reduce the use of animal models. This functional model of bone homeostasis provides a cost-effective model system using immortalized cell lines and easily procured supplemental compounds, which can be assessed by measuring surrogates of OB and OC function to study the effects of various stimuli in future experimental evaluations of bone homeostasis.

Defining the Most Potent Osteoinductive Culture Conditions for MC3T3-E1 Cells Reveals No Implication of Oxidative Stress or Energy Metabolism

The MC3T3-E1 preosteoblastic cell line is widely utilised as a reliable in vitro system to assess bone formation. However, the experimental growth conditions for these cells hugely diverge, and, particularly, the osteogenic medium (OSM)'s composition varies in research studies. Therefore, we aimed to define the ideal culture conditions for MC3T3-E1 subclone 4 cells with regard to their mineralization capacity and explore if oxidative stress or the cellular metabolism processes are implicated. Cells were treated with nine different combinations of long-lasting ascorbate (Asc) and β-glycerophosphate (βGP), and osteogenesis/calcification was evaluated at three different time-points by qPCR, Western blotting, and bone nodule staining. Key molecules of the oxidative and metabolic pathways were also assessed. It was found that sufficient mineral deposition was achieved only in the 150 μg.mL-1/2 mM Asc/βGP combination on day 21 in OSM, and this was supported by Runx2, Alpl, Bglap, and Col1a1 expression level increases. NOX2 and SOD2 as well as PGC1α and Tfam were also monitored as indicators of redox and metabolic processes, respectively, where no differences were observed. Elevation in OCN protein levels and ALP activity showed that mineralisation comes as a result of these differences. This work defines the most appropriate culture conditions for MC3T3-E1 cells and could be used by other research laboratories in this field.

Bovine serum albumin-modified 3D printed alginate dialdehyde-gelatin scaffolds incorporating polydopamine/SiO2-CaO nanoparticles for bone regeneration

Three-dimensional (3D) printing allows precise manufacturing of bone scaffolds for patient-specific applications and is one of the most recently developed and implemented technologies. In this study, bilayer and multimaterial alginate dialdehyde-gelatin (ADA-GEL) scaffolds incorporating polydopamine (PDA)/SiO2-CaO nanoparticle complexes were 3D printed using a pneumatic extrusion-based 3D printing technology and further modified on the surface with bovine serum albumin (BSA) for application in bone regeneration. The morphology, chemistry, and in vitro bioactivity of PDA/SiO2-CaO nanoparticle complexes were characterized (n = 3) and compared with those of mesoporous SiO2-CaO nanoparticles. Successful deposition of the PDA layer on the surface of the SiO2-CaO nanoparticles allowed better dispersion in a liquid medium and showed enhanced bioactivity. Rheological studies (n = 3) of ADA-GEL inks consisting of PDA/SiO2-CaO nanoparticle complexes showed results that may indicate better injectability and printability behavior compared to ADA-GEL inks incorporating unmodified nanoparticles. Microscopic observations of 3D printed scaffolds revealed that PDA/SiO2-CaO nanoparticle complexes introduced additional topography onto the surface of 3D printed scaffolds. Additionally, the modified scaffolds were mechanically stable and elastic, closely mimicking the properties of natural bone. Furthermore, protein-coated bilayer scaffolds displayed controllable absorption and biodegradation, enhanced bioactivity, MC3T3-E1 cell adhesion, proliferation, and higher alkaline phosphatase (ALP) activity (n = 3) compared to unmodified scaffolds. Consequently, the present results confirm that ADA-GEL scaffolds incorporating PDA/SiO2-CaO nanoparticle complexes modified with BSA offer a promising approach for bone regeneration applications.

Spheroids as a 3D in vitro model to study bone and bone mineralization

Traumas, fractures, and diseases can severely influence bone tissue. Insight into bone mineralization is essential for the development of therapies and new strategies to enhance bone regeneration. 3D cell culture systems, in particular cellular spheroids, have gained a lot of interest as they can recapitulate crucial aspects of the in vivo tissue microenvironment, such as the extensive cell-cell and cell-extracellular matrix (ECM) interactions found in tissue. The potential of combining spheroids and various classes of biomaterials opens also new opportunities for research within bone tissue engineering. Characterizing cellular organization, ECM structure, and ECM mineralization is a fundamental step for understanding the biological processes involved in bone tissue formation in a spheroid-based model system. Still, many experimental techniques used in this field of research are optimized for use with monolayer cell cultures. There is thus a need to develop new and improving existing experimental techniques, for applications in 3D cell culture systems. In this review, bone composition and spheroids properties are described. This is followed by an insight into the techniques that are currently used in bone spheroids research and how these can be used to study bone mineralization. We discuss the application of staining techniques used with optical and confocal fluorescence microscopy, molecular biology techniques, second harmonic imaging microscopy, Raman spectroscopy and microscopy, as well as electron microscopy-based techniques, to evaluate osteogenic differentiation, collagen production and mineral deposition. Challenges in the applications of these methods in bone regeneration and bone tissue engineering are described. STATEMENT OF SIGNIFICANCE: 3D cell cultures have gained a lot of interest in the last decades as a possible technique that can be used to recreate in vitro in vivo biological process. The importance of 3D environment during bone mineralization led scientists to use this cell culture to study this biological process, to obtain a better understanding of the events involved. New and improved techniques are also required for a proper analysis of this cell model and the process under investigation. This review summarizes the state of the art of the techniques used to study bone mineralization and how 3D cell cultures, in particular spheroids, are tested and analysed to obtain better resolved results related to this complex biological process.

Three-Dimensional Modeling with Osteoblast-like Cells under External Magnetic Field Conditions Using Magnetic Nano-Ferrite Particles for the Development of Cell-Derived Artificial Bone

The progress in artificial bone research is crucial for addressing fractures and bone defects in the aging population. However, challenges persist in terms of biocompatibility and structural complexity. Nanotechnology provides a promising avenue by which to overcome these challenges, with nano-ferrite particles (NFPs) exhibiting superparamagnetic properties. The ability to control cell positioning using a magnetic field opens up new possibilities for customizing artificial bones with specific shapes. This study explores the biological effects of NFPs on osteoblast-like cell lines (MC3T3-E1), including key analyses, such as cell viability, cellular uptake of NFPs, calcification processes, cell migration under external magnetic field conditions, and three-dimensional modeling. The results indicate that the impact of NFPs on cell proliferation is negligible. Fluorescence and transmission electron microscopy validated the cellular uptake of NFPs, demonstrating the potential for precise cell positioning through an external magnetic field. Under calcification-inducing conditions, the cells exhibited sustained calcification ability even in the presence of NFPs. The cell movement analysis observed the controlled movement of NFP-absorbing cells under an external magnetic field. Applying a magnetic field along the z-axis induced the three-dimensional shaping of cells incorporating NFPs, resulting in well-arranged z-axis directional patterns. In this study, NFPs demonstrated excellent biocompatibility and controllability under an external magnetic field, laying the foundation for innovative treatment strategies for customizing artificial bones.

Arctiin attenuates iron overload‑induced osteoporosis by regulating the PI3K/Akt pathway

Iron overload is a prevalent pathological factor observed among elderly individuals and those with specific hematological disorders, and is frequently associated with an elevated incidence of osteoporosis. Although arctiin (ARC) has been shown to possess antioxidant properties and the ability to mitigate bone degeneration, its mechanism of action in the treatment of iron overload‑induced osteoporosis (IOOP) remains incompletely understood. To explore the potential molecular mechanisms underlying the effects of ARC, the MC3T3‑E1 cell osteoblast cell line was used. Cell Counting Kit was used to assess MC3T3‑E1 cell viability. Alkaline phosphatase staining and alizarin red staining were assessed for osteogenic differentiation. Calcein AM assay was used to assess intracellular iron concentration. In addition, intracellular levels of reactive oxygen species (ROS), lipid peroxides, mitochondrial ROS, apoptosis rate and mitochondrial membrane potential changes in MC3T3‑E1 cells were examined using flow cytometry and corresponding fluorescent dyes. The relationship between ARC and the PI3K/Akt pathway was then explored by western blotting and immunofluorescence. In addition, the effects of ARC on IOOP was verified using an iron overload mouse model. Immunohistochemistry was performed to evaluate expression of osteogenesis‑related proteins. Micro-CT and H&E were used to analyze bone microstructural parameters and histomorphometric indices in the bone tissue. Notably, ARC treatment reversed the decreased viability and increased apoptosis in MC3T3‑E1 cells originally induced by ferric ammonium citrate, whilst promoting the formation of mineralized bone nodules in MC3T3‑E1 cells. Furthermore, iron overload induced a decrease in the mitochondrial membrane potential, augmented lipid peroxidation and increased the accumulation of ROS in MC3T3‑E1 cells. ARC not only positively regulated the anti‑apoptotic and osteogenic capabilities of these cells via modulation of the PI3K/Akt pathway, but also exhibited antioxidant properties by reducing oxidative stress. In vivo experiments confirmed that ARC improved bone microarchitecture and biochemical parameters in a mouse model of iron overload. In conclusion, ARC exhibits potential as a therapeutic agent for IOOP by modulating the PI3K/Akt pathway, and via its anti‑apoptotic, antioxidant and osteogenic properties.

Vitamin C Deficiency Deteriorates Bone Microarchitecture and Mineralization in a Sex-Specific Manner in Adult Mice

Vitamin C (VitC) is essential for bone health, and low VitC serum levels increase the risk for skeletal fractures. If and how VitC affects bone mineralization is unclear. Using micro-computed tomography (μCT), histologic staining, as well as quantitative backscattered electron imaging (qBEI), we assessed the effects of VitC on femoral structure and microarchitecture, bone formation, and bone mineralization density distribution (BMDD) in the VitC incompetent Gulo-/- mouse model and wild-type mice. In particular, VitC-supplemented, 20-week-old mice were compared with age-matched counterparts where dietary VitC intake was excluded from week 15. VitC depletion in Gulo-/- mice severely reduced cortical thickness of the diaphyseal shaft and bone volume around the growth plate (eg, bone volume of the primary spongiosa -43%, p < 0.001). Loss of VitC also diminished the amount of newly formed bone tissue as visualized by histology and calcein labeling of the active mineralization front. BMDD analysis revealed a shift to higher calcium concentrations upon VitC supplementation, including higher average (~10% increase in female VitC deficient mice, p < 0.001) and peak calcium concentrations in the epiphyseal and metaphyseal spongiosa. These findings suggest higher bone tissue age. Importantly, loss of VitC had significantly more pronounced effects in female mice, indicating a higher sensitivity of their skeleton to VitC deficiency. Our results reveal that VitC plays a key role in bone formation rate, which directly affects mineralization. We propose that low VitC levels may contribute to the higher prevalence of bone-degenerative diseases in females and suggest leveraging this vitamin against these conditions. © 2023 American Society for Bone and Mineral Research (ASBMR).

GC-MS based comparative metabolomic analysis of human cancellous bone reveals the critical role of linoleic acid metabolism in femur head necrosis

INTRODUCTION

Femur head necrosis (FHN) is a challenging clinical disease with unclear underlying mechanism, which pathologically is associated with disordered metabolism. However, the disordered metabolism in cancellous bone of FHN was never analyzed by gas chromatography-mass spectrometry (GC-MS).

OBJECTIVES

To elucidate altered metabolism pathways in FHN and identify putative biomarkers for the detection of FHN.

METHODS

We recruited 26 patients with femur head necrosis and 22 patients with femur neck fracture in this study. Cancellous bone tissues from the femoral heads were collected after the surgery and were analyzed by GC-MS based untargeted metabolomics approach. The resulting data were analyzed via uni- and multivariate statistical approaches. The changed metabolites were used for the pathway analysis and potential biomarker identification.

RESULTS

Thirty-seven metabolites distinctly changed in FHN group were identified. Among them, 32 metabolites were upregulated and 5 were downregulated in FHN. The pathway analysis showed that linoleic acid metabolism were the most relevant to FHN pathology. On the basis of metabolites network, L-lysine, L-glutamine and L-serine were deemed as the junctions of the whole metabolites. Finally, 9,12-octadecadienoic acid, inosine, L-proline and octadecanoic acid were considered as the potential biomarkers of FHN.

CONCLUSION

This study provides a new insight into the pathogenesis of FHN and confirms linoleic acid metabolism as the core.

Extracellular ATP-induced calcium oscillations regulating the differentiation of osteoblasts through aerobic oxidation metabolism pathways

INTRODUCTION

The increase of ATP concentration in the extracellular space represents one of the effective signals that stimulate the physiological activities of cells when the bone is exposed to external mechanical stimulation such as stretching and shear stress force throughout life. However, the effects of ATP on osteoblast differentiation and related mechanisms are not well understood.

MATERIALS AND METHODS

In this study, the roles of extracellular ATP on osteoblast differentiation, intracellular calcium ([Ca2+]i) levels, metabolomics, and the expression of proteins related to energy metabolism were investigated.

RESULTS

Our results showed that 100 μM extracellular ATP initiated intracellular calcium ([Ca2+]i) oscillations via the calcium-sensing receptor (P2R) and promoted the differentiation of MC3T3-E1 cells. Metabolomics analysis showed that the differentiation of MC3T3-E1 cells depended on aerobic oxidation, but little glycolysis. Moreover, the differentiation of MC3T3-E1 cells and aerobic oxidation were suppressed with the inhibition of AMP-activated protein kinase (AMPK).

CONCLUSION

These results indicate that calcium oscillations triggered by extracellular ATP can activate aerobic oxidation through AMPK-related signaling pathways and thus promote osteoblast differentiation.

Extracellular Calcium-Induced Calcium Transient Regulating the Proliferation of Osteoblasts through Glycolysis Metabolism Pathways

During bone remodeling, high extracellular calcium levels accumulated around the resorbing bone tissue as soon as the activation of osteoclasts. However, if and how calcium is involved in the regulation of bone remodeling remains unclear. In this study, the effect of high extracellular calcium concentrations on osteoblast proliferation and differentiation, intracellular calcium ([Ca²⁺]_i) levels, metabolomics, and the expression of proteins related to energy metabolism were investigated. Our results showed that high extracellular calcium levels initiated a [Ca²⁺]_i transient via the calcium-sensing receptor (CaSR) and promoted the proliferation of MC3T3-E1 cells. Metabolomics analysis showed that the proliferation of MC3T3-E1 cells was dependent on aerobic glycolysis, but not the tricarboxylic acid cycle. Moreover, the proliferation and glycolysis of MC3T3-E1 cells were suppressed following the inhibition of AKT. These results indicate that calcium transient triggered by high extracellular calcium levels activated glycolysis via AKT-related signaling pathways and ultimately promoted the proliferation of osteoblasts.

Suitability of R. pulmo Jellyfish-Collagen-Coated Well Plates for Cytocompatibility Analyses of Biomaterials

Cytocompatibility analyses of new implant materials or biomaterials are not only prescribed by the Medical Device Regulation (MDR), as defined in the DIN ISO Norm 10993-5 and -12, but are also increasingly replacing animal testing. In this context, jellyfish collagen has already been established as an alternative to mammalian collagen in different cell culture conditions, but a lack of knowledge exists about its applicability for cytocompatibility analyses of biomaterials. Thus, the present study was conducted to compare well plates coated with collagen type 0 derived from Rhizostoma pulmo with plates coated with bovine and porcine collagen. The coated well plates were analysed in vitro for their cytocompatibility, according to EN ISO 10993-5/-12, using both L929 fibroblasts and MC3T3 pre-osteoblasts. Thereby, the coated well plates were compared, using established materials as positive controls and a cytotoxic material, RM-A, as a negative control. L929 cells exhibited a significantly higher viability (#### p < 0.0001), proliferation (## p < 0.01), and a lower cytotoxicity (## p < 0.01 and # p < 0.05)) in the Jellagen® group compared to the bovine and porcine collagen groups. MC3T3 cells showed similar viability and acceptable proliferation and cytotoxicity in all collagen groups. The results of the present study revealed that the coating of well plates with collagen Type 0 derived from R. pulmo leads to comparable results to the case of well plates coated with mammalian collagens. Therefore, it is fully suitable for the in vitro analyses of the cytocompatibility of biomaterials or medical devices.

MiR-181a-5p promotes osteogenesis by targeting BMP3

High-throughput microRNA (miRNA) sequencing of osteoporosis was analyzed from the Gene Expression Omnibus (GEO) database to investigate specific microRNAs that control osteogenesis. MiR-181a-5p was differentially expressed among healthy subjects and those with osteoporosis. Inhibitors and mimics were transfected into cells to modulate miR-181a-5p levels to examine the role in MC3T3-E1 functions. Alkaline phosphatase (ALP) staining and Alizarin Red S (ARS) staining were used for morphological detection, and proteins of ALP and Runt-related transcription factor 2 (RUNX2), as osteogenesis markers, were detected. During the osteogenic differentiation of MC3T3-E1, the transcription level of miR-181a-5p was significantly increased. The inhibition of miR-181a-5p suppressed MC3T3-E1 osteogenic differentiation, whereas its overexpression functioned oppositely. Consistently, the miR-181a-5p antagomir aggravated osteoporosis in old mice. Additionally, we predicted potential target genes via TargetScan and miRDB and identified bone morphogenetic protein 3 (BMP3) as the target gene. Moreover, the reduced expression of miR-181a-5p was validated in our hospitalized osteoporotic patients. These findings have substantial implications for the strategies targeting miR-181a-5p to prevent osteoporosis and potential related fractures.

The effect of culture conditions on the bone regeneration potential of osteoblast-laden 3D bioprinted constructs

Three Dimensional (3D) bioprinting is one of the most recent additive manufacturing technologies and enables the direct incorporation of cells within a highly porous 3D-bioprinted construct. While the field has mainly focused on developing methods for enhancing printing resolution and shape fidelity, little is understood about the biological impact of bioprinting on cells. To address this shortcoming, this study investigated the in vitro and in vivo response of human osteoblasts subsequent to bioprinting using gelatin methacryloyl (GelMA) as the hydrogel precursor. First, bioprinted and two-dimensional (2D) cultured osteoblasts were compared, demonstrating that the 3D microenvironment from bioprinting enhanced bone-related gene expression. Second, differentiation regimens of 2-week osteogenic pre-induction in 2D before bioprinting and/or 3-week post-printing osteogenic differentiation were assessed for their capacity to increase the bioprinted construct's biofunctionality towards bone regeneration. The combination of pre-and post-induction regimens showed superior osteogenic gene expression and mineralisation in vitro. Moreover, a rat calvarial model using microtomography and histology demonstrated bone regeneration potential for the pre-and post-differentiation procedure. This study shows the positive impact of bioprinting on cells for osteogenic differentiation and the increased in vivo osteogenic potential of bioprinted constructs via a pre-induction method. STATEMENT OF SIGNIFICANCE: 3D bioprinting, one of the most recent technologies for tissue engineering has mostly focussed on developing methods for enhancing printing properties, little is understood on the biological impact of bioprinting and /or subsequent in vitro maturation methods on cells. Therefore, we addressed these fundamental questions by investigating osteoblast gene expression in bioprinted construct and assessed the efficacy of several induction regimen towards osteogenic differentiation in vitro and in vivo. Osteogenic induction of cells prior to seeding in scaffolds used in conventional tissue engineering applications has been demonstrated to increase the osteogenic potential of the resulting construct. However, to the best of our knowledge, pre-induction methods have not been investigated in 3D bioprinting.

Bone Formation in 2D Culture of Primary Cells

Relevance of mineralized nodules in two-dimensional (2D) osteoblast/osteocyte cultures to bone biology, pathology, and engineering is a decades old question, but a comprehensive answer appears to be still wanting. Bone-like cells, extracellular matrix (ECM), and mineral were all reported but so were non-bone-like ones. Many studies described seemingly bone-like cell-ECM structures based on similarity to few select bone features in vivo, yet no studies examined multiple bone features simultaneously and none systematically studied all types of structures coexisting in the same culture. Here, we report such comprehensive analysis of 2D cultures based on light and electron microscopies, Raman microspectroscopy, gene expression, and in situ messenger RNA (mRNA) hybridization. We demonstrate that 2D cultures of primary cells from mouse calvaria do form bona fide bone. Cells, ECM, and mineral within it exhibit morphology, structure, ultrastructure, composition, spatial-temporal gene expression pattern, and growth consistent with intramembranous ossification. However, this bone is just one of at least five different types of cell-ECM structures coexisting in the same 2D culture, which vary widely in their resemblance to bone and ability to mineralize. We show that the other two mineralizing structures may represent abnormal (disrupted) bone and cartilage-like structure with chondrocyte-to-osteoblast transdifferentiation. The two nonmineralizing cell-ECM structures may mimic periosteal cambium and pathological, nonmineralizing osteoid. Importantly, the most commonly used culture conditions (10mM β-glycerophosphate) induce artificial mineralization of all cell-ECM structures, which then become barely distinguishable. We therefore discuss conditions and approaches promoting formation of bona fide bone and simple means for distinguishing it from the other cell-ECM structures. Our findings may improve osteoblast differentiation and function analyses based on 2D cultures and extend applications of these cultures to general bone biology and tissue engineering research. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Tunable mechanical properties of Mo3Se3-poly vinyl alcohol-based/silk fibroin-based nanowire ensure the regeneration mechanism in tenocytes derived from human bone marrow stem cells

Silk fibroin (SF) and poly vinyl alcohol (PVA)-based nanomaterial has exceptional attention in regenerative medicine. However, the preparation of SF and PVA-based nanomaterials in the desired form is complex due to their poor mechanical strength, brittleness, and compatibility. To this end, Mo₃Se₃ is chosen as a bio-nanowire to fabricate by combining PVA and SF to improve the mechanical properties. Physicochemical and structural features of the Mo₃Se₃-PVA-SF nanowire hydrogel (Mo₃Se₃-PVA-SF-NWH) were characterized by field emission scanning electron microscope (FE-SEM). Mechanical properties, degradation ratio, hydrophilicity, water uptake capacity, biocompatibility, and biological activity of the hydrogel were also studied. Superior interactions were formed between the reinforcing molecules of Mo₃Se₃ and PVA/SF in the hydrogel network by introducing Mo₃Se₃ nanowire (NW) into the hydrogel. Conversely, Mo₃Se₃ NW imparts mechanical stability and robustness to the blends (hydrogel) with predictable long-term degradation characteristics. It was proven by in vitro biodegradable rate, and swelling behaviour was varied depending on the concentration of Mo₃Se₃ NW. Mo₃Se₃ reinforced the hydrogels and found high porosity with superior biocompatibility. Excellent cellular adaptation was analyzed by MTT assay, live/dead staining, western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). It revealed moderate toxicity at a concentration of 0.02% among the control samples. There was no discernible difference in 0.01% and 0.005% of Mo₃Se₃-PVA-SF-NWH in tenocytes derived from human bone marrow mesenchymal stem cells (hBMSC). Hence, this Mo₃Se₃-PVA-SF-NWH might be considered biocompatible due to its biological activities and appropriate mechanical properties. Overall, the Mo₃Se₃-PVA-SF-NWH might be considered a biocompatible scaffold for the possible biomedical applications of tendon tissue engineering.

Liquid flow in scaffold derived from natural source: experimental observations and biological outcome

This study investigates the biological effects on a 3D scaffold based on hydroxyapatite cultured with MC3T3 osteoblasts in response to flow-induced shear stress (FSS). The scaffold adopted here (B-HA) derives from the biomorphic transformation of natural wood and its peculiar channel geometry mimics the porous structure of the bone. From the point of view of fluid dynamics, B-HA can be considered a network of micro-channels, intrinsically offering the advantages of a microfluidic system. This work, for the first time, offers a description of the fluid dynamic properties of the B-HA scaffold, which are strongly connected to its morphology. These features are necessary to determine the FSS ranges to be applied during in vitro studies to get physiologically relevant conditions. The selected ranges of FSS promoted the elongation of the attached cells along the flow direction and early osteogenic cell differentiation. These data confirmed the ability of B-HA to promote the differentiation process along osteogenic lineage. Hence, such a bioactive and naturally derived scaffold can be considered as a promising tool for bone regeneration applications.

Current Methods in the Study of Nanomaterials for Bone Regeneration

Nanomaterials show great promise as bone regeneration materials. They can be used as fillers to strengthen bone regeneration scaffolds, or employed in their natural form as carriers for drug delivery systems. A variety of experiments have been conducted to evaluate the osteogenic potential of bone regeneration materials. In vivo, such materials are commonly tested in animal bone defect models to assess their bone regeneration potential. From an ethical standpoint, however, animal experiments should be minimized. A standardized in vitro strategy for this purpose is desirable, but at present, the results of studies conducted under a wide variety of conditions have all been evaluated equally. This review will first briefly introduce several bone regeneration reports on nanomaterials and the nanosize-derived caveats of evaluations in such studies. Then, experimental techniques (in vivo and in vitro), types of cells, culture media, fetal bovine serum, and additives will be described, with specific examples of the risks of various culture conditions leading to erroneous conclusions in biomaterial analysis. We hope that this review will create a better understanding of the evaluation of biomaterials, including nanomaterials for bone regeneration, and lead to the development of versatile assessment methods that can be widely used in biomaterial development.

miR-6315 Attenuates Methotrexate Treatment-Induced Decreased Osteogenesis and Increased Adipogenesis Potentially through Modulating TGF-β/Smad2 Signalling

Methotrexate (MTX) treatment for childhood malignancies has shown decreased osteogenesis and increased adipogenesis in bone marrow stromal cells (BMSCs), leading to bone loss and bone marrow adiposity, for which the molecular mechanisms are not fully understood. Currently, microRNAs (miRNAs) are emerging as vital mediators involved in bone/bone marrow fat homeostasis and our previous studies have demonstrated that miR-6315 was upregulated in bones of MTX-treated rats, which might be associated with bone/fat imbalance by directly targeting Smad2. However, the underlying mechanisms by which miR-6315 regulates osteogenic and adipogenic differentiation require more investigations. Herein, we further explored and elucidated the regulatory roles of miR-6315 in osteogenesis and adipogenesis using in vitro cell models. We found that miR-6315 promotes osteogenic differentiation and it alleviates MTX-induced increased adipogenesis. Furthermore, our results suggest that the involvement of miR-6315 in osteogenesis/adipogenesis regulation might be partially through modulating the TGF-β/Smad2 signalling pathway. Our findings indicated that miR-6315 may be important in regulating osteogenesis and adipogenesis and might be a therapeutic target for preventing/attenuating MTX treatment-associated bone loss and marrow adiposity.