Comparative materials differences revealed in engineered bone as a function of cell-specific differentiation

Zinc based biodegradable metals for bone repair and regeneration: Bioactivity and molecular mechanisms

Bone fractures and critical-size bone defects are significant public health issues, and clinical treatment outcomes are closely related to the intrinsic properties of the utilized implant materials. Zinc (Zn)-based biodegradable metals (BMs) have emerged as promising bioactive materials because of their exceptional biocompatibility, appropriate mechanical properties, and controllable biodegradation. This review summarizes the state of the art in terms of Zn-based metals for bone repair and regeneration, focusing on bridging the gap between biological mechanism and required bioactivity. The molecular mechanism underlying the release of Zn ions from Zn-based BMs in the improvement of bone repair and regeneration is elucidated. By integrating clinical considerations and the specific bioactivity required for implant materials, this review summarizes the current research status of Zn-based internal fixation materials for promoting fracture healing, Zn-based scaffolds for regenerating critical-size bone defects, and Zn-based barrier membranes for reconstituting alveolar bone defects. Considering the significant progress made in the research on Zn-based BMs for potential clinical applications, the challenges and promising research directions are proposed and discussed.

Effects of stepwise administration of osteoprotegerin and parathyroid hormone-related peptide DNA vectors on bone formation in ovariectomized rat model

Osteoporosis is a metabolic bone disease that impairs bone mineral density, microarchitecture, and strength. It requires continuous management, and further research into new treatment options is necessary. Osteoprotegerin (OPG) inhibits bone resorption and osteoclast activity. The objective of this study was to investigate the effects of stepwise administration of OPG-encoded minicircles (mcOPG) and a bone formation regulator, parathyroid hormone-related peptide (PTHrP)-encoded minicircles (mcPTHrP) in osteoporosis. The combined treatment with mcOPG and mcPTHrP significantly increased osteogenic marker expression in osteoblast differentiation compared with the single treatment groups. A model of postmenopausal osteoporosis was established in 12-week-old female rats through ovariectomy (OVX). After 8 weeks of OVX, mcOPG (80 µg/kg) was administered via intravenous injection. After 16 weeks of OVX, mcPTHrP (80 µg/kg) was injected once a week for 3 weeks. The bone microstructure in the femur was evaluated 24 weeks after OVX using micro-CT. In a proof-of-concept study, stepwise treatment with mcOPG and mcPTHrP on an OVX rat model significantly improved bone microstructure compared to treatment with mcOPG or mcPTHrP alone. These results suggest that stepwise treatment with mcOPG and mcPTHrP may be a potential treatment for osteoporosis.

Exploring the future of regenerative medicine: Unveiling the potential of optical microscopy for structural and functional imaging of stem cells

Regenerative medicine, which utilizes stem cells for tissue and organ repair, holds immense promise in healthcare. A comprehensive understanding of stem cell characteristics is crucial to unlock their potential. This study explores the pivotal role of optical microscopy in advancing regenerative medicine as a potent tool for stem cell research. Advanced optical microscopy techniques enable an in-depth examination of stem cell behavior, morphology, and functionality. The review encompasses current optical microscopy, elucidating its capabilities and constraints in stem cell imaging, while also shedding light on emerging technologies for improved stem cell visualization. Optical microscopy, complemented by techniques like fluorescence and multiphoton imaging, enhances our comprehension of stem cell dynamics. The introduction of label-free imaging facilitates noninvasive, real-time stem cell monitoring without external dyes or markers. By pushing the boundaries of optical microscopy, researchers reveal the intricate cellular mechanisms underpinning regenerative processes, thereby advancing more effective therapeutic strategies. The current study not only outlines the future of regenerative medicine but also underscores the pivotal role of optical microscopy in both structural and functional stem cell imaging.

Quantitative Raman chemical imaging of intracellular drug-membrane aggregates and small molecule drug precipitates in cytoplasmic organelles

Raman confocal microscopes have been used to visualize the distribution of small molecule drugs within different subcellular compartments. This visualization allows the discovery, characterization, and detailed analysis of the molecular transport phenomena underpinning the Volume of Distribution - a key parameter governing the systemic pharmacokinetics of small molecule drugs. In the specific case of lipophilic small molecules with large Volumes of Distribution, chemical imaging studies using Raman confocal microscopes have revealed how weakly basic, poorly soluble drug molecules can accumulate inside cells by forming stable, supramolecular complexes in association with cytoplasmic membranes or by precipitating out within organelles. To study the self-assembly and function of the resulting intracellular drug inclusions, Raman chemical imaging methods have been developed to measure and map the mass, concentration, and ionization state of drug molecules at a microscopic, subcellular level. Beyond the field of drug delivery, Raman chemical imaging techniques relevant to the study of microscopic drug precipitates and drug-lipid complexes which form inside cells are also being developed by researchers with seemingly unrelated scientific interests. Highlighting advances in data acquisition, calibration methods, and computational data management and analysis tools, this review will cover a decade of technological developments that enable the conversion of spectral signals obtained from Raman confocal microscopes into new discoveries and information about previously unknown, concentrative drug transport pathways driven by soluble-to-insoluble phase transitions occurring within the cytoplasmic organelles of eukaryotic cells.

Cemented versus uncemented stems for revision total hip replacement: A systematic review and meta-analysis

BACKGROUND

The popularity of uncemented stems in revision total hip arthroplasty (THA) has increased in the last decade.

AIM

To assess the outcomes of both cemented and uncemented stems after mid-term follow up.

METHODS

This study was performed following both the Preferred Reporting Items for Systematic Reviews and Meta-analyses Statement and the Cochrane Handbook for systematic reviews and meta-analysis guidelines. Articles were chosen irrespective of country of origin or language utilized for the article full texts. This paper included studies that reviewed revision THA for both cemented or uncemented long stems.

RESULTS

Three eligible studies were included in the meta-analysis. Analysis was conducted by using Review Manager version 5.3. We computed the risk ratio as a measure of the treatment effect, taking into account heterogeneity. We used random-effect models. There were no significant differences found for intraoperative periprosthetic fractures [risk ratio (RR) = 1.25; 95% confidence interval (CI): 0.29-5.32; P = 0.76], aseptic loosening (RR = 2.15, 95%CI: 0.81-5.70; P = 0.13), dislocation rate (RR = 0.50; 95%CI: 0.10-2.47; P = 0.39), or infection rate (RR = 0.99, 95%CI: 0.82-1.19; P = 0.89), between the uncemented and the cemented long stems for revision THA after mid-term follow-up.

CONCLUSION

This study has evaluated the mid-term outcomes of both cemented and uncemented stems at first-time revision THA. In summary, there were no significant differences in the dislocation rate, aseptic loosening, intraoperative periprosthetic fracture and infection rate between the two cohorts.

Quantitative chemometric phenotyping of three-dimensional liver organoids by Raman spectral imaging

Confocal Raman spectral imaging (RSI) enables high-content, label-free visualization of a wide range of molecules in biological specimens without sample preparation. However, reliable quantification of the deconvoluted spectra is needed. Here we develop an integrated bioanalytical methodology, qRamanomics, to qualify RSI as a tissue phantom calibrated tool for quantitative spatial chemotyping of major classes of biomolecules. Next, we apply qRamanomics to fixed 3D liver organoids generated from stem-cell-derived or primary hepatocytes to assess specimen variation and maturity. We then demonstrate the utility of qRamanomics for identifying biomolecular response signatures from a panel of liver-altering drugs, probing drug-induced compositional changes in 3D organoids followed by in situ monitoring of drug metabolism and accumulation. Quantitative chemometric phenotyping constitutes an important step in developing quantitative label-free interrogation of 3D biological specimens.

Fundamentals and Applications of Raman-Based Techniques for the Design and Development of Active Biomedical Materials

Raman spectroscopy is an analytical method based on light-matter interactions that can interrogate the vibrational modes of matter and provide representative molecular fingerprints. Mediated by its label-free, non-invasive nature, and high molecular specificity, Raman-based techniques have become ubiquitous tools for in situ characterization of materials. This review comprehensively describes the theoretical and practical background of Raman spectroscopy and its advanced variants. The numerous facets of material characterization that Raman scattering can reveal, including biomolecular identification, solid-to-solid phase transitions, and spatial mapping of biomolecular species in bioactive materials, are highlighted. The review illustrates the potential of these techniques in the context of active biomedical material design and development by highlighting representative studies from the literature. These studies cover the use of Raman spectroscopy for the characterization of both natural and synthetic biomaterials, including engineered tissue constructs, biopolymer systems, ceramics, and nanoparticle formulations, among others. To increase the accessibility and adoption of these techniques, the present review also provides the reader with practical recommendations on the integration of Raman techniques into the experimental laboratory toolbox. Finally, perspectives on how recent developments in plasmon- and coherently-enhanced Raman spectroscopy can propel Raman from underutilized to critical for biomaterial development are provided.

Physiologic Response Evaluation of Human Foetal Osteoblast Cells within Engineered 3D-Printed Polylactic Acid Scaffolds

Large bone defect treatments have always been one of the important challenges in clinical practice and created a huge demand for more efficacious regenerative approaches. The bone tissue engineering (BTE) approach offered a new alternative to conventional bone grafts, addressing all clinical needs. Over the past years, BTE research is focused on the study and realisation of new biomaterials, including 3D-printed supports to improve mechanical, structural and biological properties. Among these, polylactic acid (PLA) scaffolds have been considered the most promising biomaterials due to their good biocompatibility, non-toxic biodegradability and bioresorbability. In this work, we evaluated the physiological response of human foetal osteoblast cells (hFOB), in terms of cell proliferation and osteogenic differentiation, within oxygen plasma treated 3D-printed PLA scaffolds, obtained by fused deposition modelling (FDM). A mechanical simulation to predict their behaviour to traction, flexural or torque solicitations was performed. We found that: 1. hFOB cells adhere and grow on scaffold surfaces; 2. hFOB grown on oxygen plasma treated PLA scaffolds (PLA_PT) show an improvement of cell adhesion and proliferation, compared to not-plasma treated scaffolds (PLA_NT); 3. Over time, hFOB penetrate along strands, differentiate, and form a fibrous matrix, tissue-like; 4. 3D-printed PLA scaffolds have good mechanical behaviour in each analysed configuration. These findings suggest that 3D-printed PLA scaffolds could represent promising biomaterials for medical implantable devices in the orthopaedic field.

Hypoxia mimetics restore bone biomineralisation in hyperglycaemic environments

Diabetic patients have an increased risk of fracture and an increased occurrence of impaired fracture healing. Diabetic and hyperglycaemic conditions have been shown to impair the cellular response to hypoxia, via an inhibited hypoxia inducible factor (HIF)-1α pathway. We investigated, using an in vitro hyperglycaemia bone tissue engineering model (and a multidisciplinary bone characterisation approach), the differing effects of glucose levels, hypoxia and chemicals known to stabilise HIF-1α (CoCl2 and DMOG) on bone formation. Hypoxia (1% O2) inhibited bone nodule formation and resulted in discrete biomineralisation as opposed to the mineralised extracellular collagen fibres found in normoxia (20% O2). Unlike hypoxia, the use of hypoxia mimetics did not prevent nodule formation in normal glucose level. Hyperglycaemic conditions (25 mM and 50 mM glucose) inhibited biomineralisation. Interestingly, both hypoxia mimetics (CoCl2 and DMOG) partly restored hyperglycaemia inhibited bone nodule formation. These results highlight the difference in osteoblast responses between hypoxia mimetics and actual hypoxia and suggests a role of HIF-1α stabilisation in bone biomineralisation that extends that of promoting neovascularisation, or other system effects associated with hypoxia and bone regeneration in vivo. This study demonstrates that targeting the HIF pathway may represent a promising strategy for bone regeneration in diabetic patients.

In vivo non-invasive monitoring of tissue development in 3D printed subcutaneous bone scaffolds using fibre-optic Raman spectroscopy

The development of novel biomaterials for regenerative therapy relies on the ability to assess tissue development, quality, and similarity with native tissue types in in vivo experiments. Non-invasive imaging modalities such as X-ray computed tomography offer high spatial resolution but limited biochemical information while histology and biochemical assays are destructive. Raman spectroscopy is a non-invasive, label-free and non-destructive technique widely applied for biochemical characterization. Here we demonstrate the use of fibre-optic Raman spectroscopy for in vivo quantitative monitoring of tissue development in subcutaneous calcium phosphate scaffolds in mice over 16 weeks. Raman spectroscopy was able to quantify the time dependency of different tissue components related to the presence, absence, and quantity of mesenchymal stem cells. Scaffolds seeded with stem cells produced 3-5 times higher amount of collagen-rich extracellular matrix after 16 weeks implantation compared to scaffolds without. These however, showed a 2.5 times higher amount of lipid-rich tissue compared to implants with stem cells. Ex vivo micro-computed tomography and histology showed stem cell mediated collagen and bone development. Histological measures of collagen correlated well with Raman derived quantifications (correlation coefficient in vivo 0.74, ex vivo 0.93). In the absence of stem cells, the scaffolds were largely occupied by adipocytes. The technique developed here could potentially be adapted for a range of small animal experiments for assessing tissue engineering strategies at the biochemical level.

Clinical Outcomes following Biologically Enhanced Demineralized Bone Matrix Augmentation of Complex Rotator Cuff Repair

Complex rotator cuff tears provide a significant challenge for treating surgeons, given their high failure rate following repair and the associated morbidity. The purpose of this study is to evaluate the clinical outcomes of patients who underwent biologically enhanced demineralized bone matrix augmentation of rotator cuff repairs. Twenty patients with complex rotator cuff tears underwent arthroscopic rotator cuff repair by a single surgeon with demineralized bone matrix (DBM) augmentation that was biologically enhanced with platelet-rich plasma and concentrated bone marrow aspirate. Post-operative MRI was used to determine surgical success. Patient reported outcome measures and range of motion data were collected pre-operatively and at the final post-operative visit for each patient. Ten patients (50%) with DBM augmentation of their arthroscopic rotator cuff repair were deemed non-failures. The failure group had less improvement of visual analogue pain scale (p = 0.017), Simple Shoulder Test (p = 0.032), Single Assessment Numerical Evaluation (p = 0.006) and abduction (p = 0.046). There was no difference between the groups for change in American Shoulder and Elbow Society score (p = 0.096), Constant-Murley score (p = 0.086), forward elevation (p = 0.191) or external rotation (p = 0.333). The present study found that 50% of patients who underwent biologically enhanced DBM augmentation of their rotator cuff repair demonstrated MRI-determined failure of supraspinatus healing.

Midterm results of modern patellofemoral arthroplasty versus total knee arthroplasty for isolated patellofemoral arthritis: systematic review and meta-analysis of comparative studies

BACKGROUND

Both Patellofemoral Arthroplasty (PFA) and Total Knee Arthroplasty (TKA) are accepted surgical options for end-stage isolated patellofemoral osteoarthritis (PFOA). We performed a systematic review and meta-analysis to compare outcomes of PFA and TKA by evaluation of the patient-reported outcome measures (PROMs).

METHODS

We systematically identified publications reporting on patients that underwent either TKA or modern PFA for isolated PFOA. Meta-analysis software was used to screen for potential articles with at least two years' follow-up. Data were extracted and analysed for all PROMs operating time, postoperative inpatient time, complications and cost. We included five studies in our cumulative meta-analysis and reviewed them using Review Manager V.5.0. We computed the risk ratio as a measure of the treatment effect, taking into account heterogeneity. We used random-effect models.

RESULTS

No significant difference was found between both TKA and PFA in the context of operating time. No significant difference after five years' follow-up was found between the two treatment options in terms of UCLA score and patient satisfaction. PFA showed significant improvement in WOMAC score at five-year follow-up, less postoperative inpatient time, better cost-effectiveness and significantly less blood loss.

CONCLUSION

PFA seems to be a viable alternative to TKA for treatment of isolated PFOA in appropriately selected patients. PFA showed less postoperative inpatient time and blood loss with similar PROMs to the TKA. Moreover, it is an economically beneficial joint-preserving procedure.

Identification of an Ultrathin Osteochondral Interface Tissue with Specific Nanostructure at the Human Knee Joint

Cartilage adheres to subchondral bone via a specific osteochondral interface tissue where forces are transferred from soft cartilage to hard bone without conferring fatigue damage over a lifetime of load cycles. However, the fine structure and mechanical properties of the osteochondral interface tissue remain unclear. Here, we identified an ultrathin ∼20-30 μm graded calcified region with two-layered micronano structures of osteochondral interface tissue in the human knee joint, which exhibited characteristic biomolecular compositions and complex nanocrystals assembly. Results from finite element simulations revealed that within this region, an exponential increase of modulus (3 orders of magnitude) was conducive to force transmission. Nanoscale heterogeneity in the hydroxyapatite, coupled with enrichment of elastic-responsive protein-titin, which is usually present in muscle, endowed the osteochondral tissue with excellent mechanical properties. Collectively, these results provide novel insights into the potential design for high-performance interface materials for osteochondral interface regeneration.

Tough, Flexible, and Bioactive Amphoteric Copolymer-Based Hydrogel for Bone Regeneration without Encapsulation of Seed Cells/Simulating Cues

Bone tissue scaffolds with good bulk or surface osteoconductivity are always pursued by biomaterial scientists. In this paper, we design a tough and flexible amphoteric copolymer-based (AC) hydrogel with bioactive groups for bone regeneration. In detail, our hydrogels are copolymerized with N-acyl glycinamide (NAGA), anionic acrylate alendronate (AcAln), and cationic (2-(acryloyloxy)ethyl) trimethyl ammonium chloride (DMAEA-Q) by free radical polymerization. There are three kinds of synergetic physical cross-links among our polyamphion hydrogels: (1) double hydrogen bonds between amide groups in NAGA to provide toughness, (2) hydrogen bonds between dual bisphosphite groups in AcAln, and (3) weak ionic pairs between the anionic bisphosphite groups and the cationic quaternary ammonium groups in DMAEA-Q to offer flexibility. The AC hydrogel shows osteoid-like viscoelasticity, which makes the AC hydrogel osteogenesis inductive. During the repairing process, the bioactive bisphosphite groups accelerate the calcium fixation to expedite the mineralization of the new-formed bone. At the same time, the surface charge property of AC hydrogels also prevents fibrous cyst formation, thus guaranteeing osseointegration. Our in vitro data strongly demonstrate that the AC hydrogel is an excellent matrix to induce osteogenesis of rat bone marrow mesenchymal stem cells. More importantly, the following in vivo experiments further prove that the AC hydrogel can reach satisfactory bone regeneration without encapsulation of seed cells or application of external simulating cues. These exciting results demonstrate that our AC hydrogel is a promising scaffold for bone regeneration. Our work can also inspire the constituent and structure design of biomaterial scaffolds for tissue regeneration.

In Vitro Toxicity of Bone Graft Materials to Human Mineralizing Cells

Bone graft materials from synthetic, bovine, and human sources were analyzed and tested for in vitro cytotoxicity on dental pulp stem cells (DPSCs) and osteosarcoma cells (Saos-2). Raman spectroscopy indicated significant amounts of collagen only in human bone-derived materials, where the mineral to protein ratio was 3.55 ± 0.45, consistent with bone. X-ray fluorescence revealed tungsten (W) concentrations of 463 ± 73, 400 ± 77, and 92 ± 42 ppm in synthetic, bovine, and human bone chips, respectively. When these chips were added to DPSCs on tissue culture plastic, the doubling times after two days were the same as the controls, 16.5 ± 0.5 h. Those cultured with synthetic or bovine chips were 96.5 ± 8.1 and 25.2 ± 1.4 h, respectively. Saos-2 was more sensitive. During the first two days with allogeneic or bovine graft materials, cell numbers declined. When DPSC were cultured on collagen, allogeneic and bovine bone chips did not increase doubling times. We propose cytotoxicity was associated with tungsten, where only the concentration in human bone chips was below 184 ppm, the value reported as cytotoxic in vitro. Cells on collagen were resistant to bone chips, possibly due to tungsten adsorption by collagen.

Early Economic Analysis of Robotic-Assisted Unicondylar Knee Arthroplasty May Be Cost Effective in Patients with End-Stage Osteoarthritis

Unicondylar knee arthroplasty (UKA), as an alternative to total knee arthroplasty (TKA), has been shown to be an effective option for patients with single-compartment end-stage knee osteoarthritis. Implant survival is contingent upon proper alignment, which has been improved with the advent of robotic-assisted surgery (r-UKA), but whether this outweighs the increased cost of the robotic-assist device has not been analyzed in the literature. The purpose of this study was to investigate the mid-term cost-effectiveness of r-UKA compared with UKA with traditional instrumentation (t-UKA) in the United States. A cost-effectiveness analysis using a four-state Markov model was performed using data from the 2018 National Joint Registry of England and Wales and a retrospective multicenter, cohort study on a cohort of 65-year-old patients having undergone r-UKA. The main outcome was cost per revision avoided and sensitivity analyses were conducted to evaluate the impact of using different model assumptions on the results. The Markov model illustrated that the benefit derived from r-UKA versus t-UKA was beneficial from a payer's perspective. The estimated incremental cost-effectiveness ratio (ICER) was $14,737 per revision avoided in a facility seeing 100 patients a year. Case volume was shown to be the primary variable affecting cost-effectiveness, with the value of r-UKA directly increasing with higher case volumes. Cost-effectiveness analyses demonstrated that the use of r-UKA is an effective alternative to t-UKA in patients with single-compartment knee osteoarthritis. While this study could benefit from longer follow-up clinical studies to illustrate the benefits of r-UKAs beyond the current 2 years time horizon, r-UKAs remained cost-effective, even after investigating several different assumptions.

Bioengineering the ameloblastoma tumour to study its effect on bone nodule formation

Ameloblastoma is a benign, epithelial cancer of the jawbone, which causes bone resorption and disfigurement to patients affected. The interaction of ameloblastoma with its tumour stroma drives invasion and progression. We used stiff collagen matrices to engineer active bone forming stroma, to probe the interaction of ameloblastoma with its native tumour bone microenvironment. This bone-stroma was assessed by nano-CT, transmission electron microscopy (TEM), Raman spectroscopy and gene analysis. Furthermore, we investigated gene correlation between bone forming 3D bone stroma and ameloblastoma introduced 3D bone stroma. Ameloblastoma cells increased expression of MMP-2 and -9 and RANK temporally in 3D compared to 2D. Our 3D biomimetic model formed bone nodules of an average surface area of 0.1 mm² and average height of 92.37 [Formula: see text] 7.96 μm over 21 days. We demonstrate a woven bone phenotype with distinct mineral and matrix components and increased expression of bone formation genes in our engineered bone. Introducing ameloblastoma to the bone stroma, completely inhibited bone formation, in a spatially specific manner. Multivariate gene analysis showed that ameloblastoma cells downregulate bone formation genes such as RUNX2. Through the development of a comprehensive bone stroma, we show that an ameloblastoma tumour mass prevents osteoblasts from forming new bone nodules and severely restricted the growth of existing bone nodules. We have identified potential pathways for this inhibition. More critically, we present novel findings on the interaction of stromal osteoblasts with ameloblastoma.

Tracking the Differentiation Status of Human Neural Stem Cells through Label-Free Raman Spectroscopy and Machine Learning-Based Analysis

The ability to noninvasively monitor stem cells' differentiation is important to stem cell studies. Raman spectroscopy is a non-harmful imaging approach that acquires the cellular biochemical signatures. Herein, we report the first use of label-free Raman spectroscopy to characterize the gradual change during the differentiation process of live human neural stem cells (NSCs) in the in vitro cultures. Raman spectra of 600-1800 cm-1 were measured with human NSC cultures from the undifferentiated stage (NSC-predominant) to the highly differentiated one (neuron-predominant) and subsequently analyzed using various mathematical methods. Hierarchical cluster analysis distinguished two cell types (NSCs and neurons) through the spectra. The subsequently derived differentiation rate matched that measured by immunocytochemistry. The key spectral biomarkers were identified by time-dependent trend analysis and principal component analysis. Furthermore, through machine learning-based analysis, a set of eight spectral data points were found to be highly accurate in classifying cell types and predicting the differentiation rate. The predictive accuracy was the highest using the artificial neural network (ANN) and slightly lowered using the logistic regression model and linear discriminant analysis. In conclusion, label-free Raman spectroscopy with the aid of machine learning analysis can provide the noninvasive classification of cell types at the single-cell level and thus accurately track the human NSC differentiation. A set of eight spectral data points combined with the ANN method were found to be the most efficient and accurate. Establishing this non-harmful and efficient strategy will shed light on the in vivo and clinical studies of NSCs.

A novel engineered vascular construct of stem cell-laden 3D-printed PGSA scaffold enhances tissue revascularization

Development of transplantable engineered tissue has been hampered by lacking vascular network within the engineered tissue. Three-dimensional (3D) printing has emerged as a new technology with great potential in fabrication and customization of geometric microstructure. In this study, utilizing digital light processing system, we manufactured a recently designed novel 3D architecture scaffold with poly(glycerol sebacate) acrylate (PGSA). Vascular construct was subsequently generated by seeding stem cells within this scaffold. PGSA provided inductive substrate in terms of supporting three-germ layer differentiation of embryonic stem cells (ESCs) and also promoting ESCs-derived vascular progenitor cells (VPCs) differentiation into endothelial cells (ECs). Furthermore, the differentiation efficiency of VPCs into ECs on PGSA was much higher than that on collagen IV or fibronectin. The results from seeding VPCs in the rotating hexagonal PGSA scaffold suggest that this architectural framework is highly efficient for cell engraftment in 3D structures. After long-term suspension culture of the VPCs in scaffold under directed EC differentiation condition, VPC-differentiated ECs were populated in the scaffold and expressed EC markers. Transplantation of the vascular construct in mice resulted in formation of new vascular network and integration of the microvasculature within the scaffold into the existing vasculature of host tissue. Importantly, in a mouse model of wound healing, ECs from the transplanted vascular construct directly contributed to revascularization and enhanced blood perfusion at the injured site. Collectively, this transplantable vascular construct provides an innovative alternative therapeutic strategy for vascular tissue engineering.

Biodegradable magnesium combined with distraction osteogenesis synergistically stimulates bone tissue regeneration via CGRP-FAK-VEGF signaling axis

Critical size bone defects are frequently caused by accidental trauma, oncologic surgery, and infection. Distraction osteogenesis (DO) is a useful technique to promote the repair of critical size bone defects. However, DO is usually a lengthy treatment, therefore accompanied with increased risks of complications such as infections and delayed union. Here, we demonstrated that magnesium (Mg) nail implantation into the marrow cavity degraded gradually accompanied with about 4-fold increase of new bone formation and over 5-fold of new vessel formation as compared with DO alone group in the 5 mm femoral segmental defect rat model at 2 weeks after distraction. Mg nail upregulated the expression of calcitonin gene-related peptide (CGRP) in the new bone as compared with the DO alone group. We further revealed that blockade of the sensory nerve by overdose capsaicin blunted Mg nail enhanced critical size bone defect repair during the DO process. CGRP concentration-dependently promoted endothelial cell migration and tube formation. Meanwhile, CGRP promoted the phosphorylation of focal adhesion kinase (FAK) at Y397 site and elevated the expression of vascular endothelial growth factor A (VEGFA). Moreover, inhibitor/antagonist of CGRP receptor, FAK, and VEGF receptor blocked the Mg nail stimulated vessel and bone formation. We revealed, for the first time, a CGRP-FAK-VEGF signaling axis linking sensory nerve and endothelial cells, which may be the main mechanism underlying Mg-enhanced critical size bone defect repair when combined with DO, suggesting a great potential of Mg implants in reducing DO treatment time for clinical applications.

A review of in vitro cell culture testing methods for bioactive glasses and other biomaterials for hard tissue regeneration

Bioactive glasses are used to regenerate bone by a mechanism which involves surface degradation, the release of ions such as calcium, soluble silica and phosphate and the precipitation of a biomimetic apatite surface layer on the glass. One major area of bioactive glass research is the incorporation of therapeutically active ions to broaden the application range of these materials. When developing such new compositions, in vitro cell culture studies are a key part of their characterisation. However, parameters of cell culture studies vary widely, and depending on the intended use of bioactive glass compositions, different layouts, cell types and assays need to be used. The aim of this publication is to provide materials scientists, particularly those new to cell culture studies, with a tool for selecting the most appropriate assays to give insight into the properties of interest.

Bone-on-a-chip: microfluidic technologies and microphysiologic models of bone tissue

Bone is an active organ that continuously undergoes an orchestrated process of remodeling throughout life. Bone tissue is uniquely capable of adapting to loading, hormonal, and other changes happening in the body, as well as repairing bone that becomes damaged to maintain tissue integrity. On the other hand, diseases such as osteoporosis and metastatic cancers disrupt normal bone homeostasis leading to compromised function. Historically, our ability to investigate processes related to either physiologic or diseased bone tissue has been limited by traditional models that fail to emulate the complexity of native bone. Organ-on-a-chip models are based on technological advances in tissue engineering and microfluidics, enabling the reproduction of key features specific to tissue microenvironments within a microfabricated device. Compared to conventional in-vitro and in-vivo bone models, microfluidic models, and especially organs-on-a-chip platforms, provide more biomimetic tissue culture conditions, with increased predictive power for clinical assays. In this review, we will report microfluidic and organ-on-a-chip technologies designed for understanding the biology of bone as well as bone-related diseases and treatments. Finally, we discuss the limitations of the current models and point toward future directions for microfluidics and organ-on-a-chip technologies in bone research.

The Potential Function of Super Enhancers in Human Bone Marrow Mesenchymal Stem Cells during Osteogenic Differentiation

Super enhancers (SEs) are large clusters of transcriptional activity enhancers, which drive and control the expression of cell identity genes, as well as differentiation of specific cell types. SEs have great application potential in pathogenic mechanism studies in developmental biology, cancer, and other diseases. However, the potential function and regulatory mechanism of SEs in the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) are unknown. Therefore, this study investigated the potential function of SEs in the osteogenic differentiation of hBMSCs and their target genes. Osteogenesis was induced in three hBMSCs groups for 14 days. Further, ChIP-seq was performed on cells before and after osteogenic differentiation. Two target genes were then selected from cells before and after osteogenic differentiation for RT-qPCR. Finally, the selected SE target genes were analyzed by bioinformatics. In total, 1,680 SEs were identified in hBMSCs. After 14 days of osteogenic induction, only 342 SEs were detected in cells, among which 1,380 unique SEs were detected in hBMSCs, 42 unique SEs were found in cells induced by osteoblast differentiation after 14 days, and 300 SEs were common in both groups. Further, 1,680 genes were found to be regulated by SEs in hBMSCs, including 1,094 genes with protein-coding function and 586 noncoding genes. Additionally, 342 genes were regulated by SEs in cells after 14 days of osteogenic differentiation induction, of which 223 and 119 had protein-coding and noncoding functions, respectively. KEGG analysis of SE target genes before and after osteogenic differentiation showed the TGF-β, PI3K-Akt, and ECM receptor signaling pathways as highly enriched and closely related to osteogenic differentiation. Further, RT-qPCR results of four selected target genes confirmed the sequencing results. Taken together, osteogenic differentiation of hBMSCs involves changes in multiple SEs, which may regulate the osteogenic differentiation of hBMSCs by regulating the expression of target genes.

Vibrational Spectroscopy for In Vitro Monitoring Stem Cell Differentiation

Stem cell technology has attracted considerable attention over recent decades due to its enormous potential in regenerative medicine and disease therapeutics. Studying the underlying mechanisms of stem cell differentiation and tissue generation is critical, and robust methodologies and different technologies are required. Towards establishing improved understanding and optimised triggering and control of differentiation processes, analytical techniques such as flow cytometry, immunohistochemistry, reverse transcription polymerase chain reaction, RNA in situ hybridisation analysis, and fluorescence-activated cell sorting have contributed much. However, progress in the field remains limited because such techniques provide only limited information, as they are only able to address specific, selected aspects of the process, and/or cannot visualise the process at the subcellular level. Additionally, many current analytical techniques involve the disruption of the investigation process (tissue sectioning, immunostaining) and cannot monitor the cellular differentiation process in situ, in real-time. Vibrational spectroscopy, as a label-free, non-invasive and non-destructive analytical technique, appears to be a promising candidate to potentially overcome many of these limitations as it can provide detailed biochemical fingerprint information for analysis of cells, tissues, and body fluids. The technique has been widely used in disease diagnosis and increasingly in stem cell technology. In this work, the efforts regarding the use of vibrational spectroscopy to identify mechanisms of stem cell differentiation at a single cell and tissue level are summarised. Both infrared absorption and Raman spectroscopic investigations are explored, and the relative merits, and future perspectives of the techniques are discussed.

Raman Spectroscopy Methods to Characterize the Mechanical Response of Soft Biomaterials

Raman spectroscopy has been used extensively to characterize the influence of mechanical deformation on microstructure changes in biomaterials. While traditional piezo-spectroscopy has been successful in assessing internal stresses of hard biomaterials by tracking prominent peak shifts, peak shifts due to applied loads are near or below the resolution limit of the spectrometer for soft biomaterials with moduli in the kilo- to mega-Pascal range. In this Review, in addition to peak shifts, other spectral features (e.g., polarized intensity and intensity ratio) that provide quantitative assessments of microstructural orientation and secondary structure in soft biomaterials and their strain dependence are discussed. We provide specific examples for each method and classify sensitive Raman characteristic bands common across natural (e.g., soft tissue) and synthetic (e.g., polymeric scaffolds) soft biomaterials upon mechanical deformation. This Review can provide guidance for researchers aiming to analyze micromechanics of soft tissues and engineered tissue constructs by Raman spectroscopy.

Enhanced Osteogenic Differentiation of Human Mesenchymal Stem Cells on Amine-Functionalized Titanium Using Humidified Ammonia Supplied Nonthermal Atmospheric Pressure Plasma

The surface molecular chemistry, such as amine functionality, of biomaterials plays a crucial role in the osteogenic activity of relevant cells and tissues during hard tissue regeneration. Here, we examined the possibilities of creating amine functionalities on the surface of titanium by using the nonthermal atmospheric pressure plasma jet (NTAPPJ) method with humidified ammonia, and the effects on human mesenchymal stem cell (hMSC) were investigated. Titanium samples were subjected to NTAPPJ treatments using nitrogen (N-P), air (A-P), or humidified ammonia (NA-P) as the plasma gas, while control (C-P) samples were not subjected to plasma treatment. After plasma exposure, all treatment groups showed increased hydrophilicity and had more attached cells than the C-P. Among the plasma-treated samples, the A-P and NA-P showed surface oxygen functionalities and exhibited greater cell proliferation than the C-P and N-P. The NA-P additionally showed surface amine-related functionalities and exhibited a higher level of alkaline phosphatase activity and osteocalcin expression than the other samples. The results can be explained by increases in fibronectin absorption and focal adhesion kinase gene expression on the NA-P samples. These findings suggest that NTAPPJ technology with humidified ammonia as a gas source has clinical potential for hard tissue generation.

TiO2 nanoparticles synergize with substrate mechanics to improve dental pulp stem cells proliferation and differentiation

Multiple studies exist on the influence of TiO₂ nanoparticle uptake on cell behavior. Yet little is known about the lingering influence of nanoparticles accumulation within the external environment which is particularly important to stem cell differentiation. Herein, dental pulp stem cells were cultured on hard and soft polybutadiene substrates, where 0.1 mg/mL rutile TiO₂ nanoparticles were introduced once, 24 h after plating. In the absence of TiO₂, the doubling time on soft substrate is significantly longer, while addition of TiO₂ decreases it to the same level as on the hard substrate. FACS analysis indicates particle uptake initially at 25% is reduced to 2.5% after 14 days. In the absence of TiO₂, no biomineralization on the soft and snowflake-like hydroxyapatite deposits on the hard substrate are shown at week 4. With the addition of TiO₂, SEM/EDAX reveals copious mineral deposition templated on large banded collagen fibers on both substrates. The mineral-to-matrix ratios analyzed by Raman spectroscopy are unremarkable in the absence of TiO₂. However, with addition of TiO₂, the ratios are consistent with native bone on the hard and dentin on the soft substrates. This is further confirmed by RT-PCR, which showed upregulation of markers consistent with osteogenesis and odontogenesis, respectively.

Enhanced In-Silico Polyethylene Wear Simulation of Total Knee Replacements During Daily Activities

A computational wear simulator is an efficient tool for evaluating the wear of artificial knee joints. The classical Archard's wear law-based simulator has questionable accuracy and is focused on walking. In this study, an in silico polyethylene wear simulation of total knee replacements was developed considering the various highly demanding daily activities. A good predicted accuracy (error = 8.1%) was found through comparison of the experimental results. A relatively larger averaged wear loss was found under the loading condition (1.53 mg/mc) of daily activities compared with the walking condition (1.32 mg/mc). The squatting movement (2.57 mg/mc) produces the highest overall wear rate. In addition, a relatively larger amount of wear was found on the medial side knee prosthesis than that on the lateral side. The enhanced in silico polyethylene wear simulator provides an accurate and comprehensive tool for wear prediction in preclinical wear testing.

Mechanobiologically induced bone-like nodules: Matrix characterization from micro to nanoscale

In bone tissue engineering, stem cells are known to form inhomogeneous bone-like nodules on a micrometric scale. Herein, micro- and nano-infrared (IR) micro-spectroscopies were used to decipher the chemical composition of the bone-like nodule. Histological and immunohistochemical analyses revealed a cohesive tissue with bone-markers positive cells surrounded by dense mineralized type-I collagen. Micro-IR gathered complementary information indicating a non-mature collagen at the top and periphery and a mature collagen within the nodule. Atomic force microscopy combined to IR (AFM-IR) analyses showed distinct spectra of "cell" and "collagen" rich areas. In contrast to the "cell" area, spectra of "collagen" area revealed the presence of carbohydrate moieties of collagen and/or the presence of glycoproteins. However, it was not possible to determine the collagen maturity, due to strong bands overlapping and/or possible protein orientation effects. Such findings could help developing protocols to allow a reliable characterization of in vitro generated complex bone tissues.

Molecular imaging of extracellular vesicles in vitro via Raman metabolic labelling

Extracellular vesicles (EVs) are biologically-derived nanovectors important for intercellular communication and trafficking. As such, EVs show great promise as disease biomarkers and therapeutic drug delivery vehicles. However, despite the rapidly growing interest in EVs, understanding of the biological mechanisms that govern their biogenesis, secretion, and uptake remains poor. Advances in this field have been hampered by both the complex biological origins of EVs, which make them difficult to isolate and identify, and a lack of suitable imaging techniques to properly study their diverse biological roles. Here, we present a new strategy for simultaneous quantitative in vitro imaging and molecular characterisation of EVs in 2D and 3D based on Raman spectroscopy and metabolic labelling. Deuterium, in the form of deuterium oxide (D2O), deuterated choline chloride (d-Chol), or deuterated d-glucose (d-Gluc), is metabolically incorporated into EVs through the growth of parent cells on medium containing one of these compounds. Isolated EVs are thus labelled with deuterium, which acts as a bio-orthogonal Raman-active tag for direct Raman identification of EVs when introduced to unlabelled cell cultures. Metabolic deuterium incorporation demonstrates no apparent adverse effects on EV secretion, marker expression, morphology, or global composition, indicating its capacity for minimally obstructive EV labelling. As such, our metabolic labelling strategy could provide integral insights into EV biocomposition and trafficking. This approach has the potential to enable a deeper understanding of many of the biological mechanisms underpinning EVs, with profound implications for the design of EVs as therapeutic delivery vectors and applications as disease biomarkers.

Bone Marrow Aspirate Concentrate: Its Uses in Osteoarthritis

Human bone marrow (BM) is a kind of source of mesenchymal stem cells (MSCs) as well as growth factors and cytokines that may aid anti-inflammation and regeneration for various tissues, including cartilage and bone. However, since MSCs in BM usually occupy only a small fraction (0.001%) of nucleated cells, bone marrow aspirate concentrate (BMAC) for cartilage pathologies, such as cartilage degeneration, defect, and osteoarthritis, have gained considerable recognition in the last few years due to its potential benefits including disease modifying and regenerative capacity. Although further research with well-designed, randomized, controlled clinical trials is needed to elucidate the exact mechanism of BMAC, this may have the most noteworthy effect in patients with osteoarthritis. The purpose of this article is to review the general characteristics of BMAC, including its constituent, action mechanisms, and related issues. Moreover, this article aims to summarize the clinical outcomes of BMAC reported to date.

Bioenergetic-active materials enhance tissue regeneration by modulating cellular metabolic state

Cellular bioenergetics (CBE) plays a critical role in tissue regeneration. Physiologically, an enhanced metabolic state facilitates anabolic biosynthesis and mitosis to accelerate regeneration. However, the development of approaches to reprogram CBE, toward the treatment of substantial tissue injuries, has been limited thus far. Here, we show that induced repair in a rabbit model of weight-bearing bone defects is greatly enhanced using a bioenergetic-active material (BAM) scaffold compared to commercialized poly(lactic acid) and calcium phosphate ceramic scaffolds. This material was composed of energy-active units that can be released in a sustained degradation-mediated fashion once implanted. By establishing an intramitochondrial metabolic bypass, the internalized energy-active units significantly elevate mitochondrial membrane potential (ΔΨm) to supply increased bioenergetic levels and accelerate bone formation. The ready-to-use material developed here represents a highly efficient and easy-to-implement therapeutic approach toward tissue regeneration, with promise for bench-to-bedside translation.

Insights into OCP identification and quantification in the context of apatite biomineralization

Monitoring apatite formation throughin situRAMAN andex situssNMR spectroscopy.

Osteoinductive Material to Fine-Tune Paracrine Crosstalk of Mesenchymal Stem Cells With Endothelial Cells and Osteoblasts

While stem cell/biomaterial studies provide solid evidences that biomaterial intrinsic cues deeply affect cell fate, current strategies tend to neglect their effects on mesenchymal stem cells (MSCs) secretory activities and resulting cell-crosstalks. The present study aims to investigate the impact of bone-mimetic material (B-MM), with intrinsic osteoinductive property, on MSCs mediator secretions; and to explore underlying effects on cells involved in bone regeneration. Human MSCs were cultured, on B-MM, made from inorganic calcium phosphate supplemented with chitosan and hyaluronic acid biopolymers. Collected MSCs culture media were assessed for mediators release quantification and used further to stimulate endothelial cells (ECs) and alveolar bone derived osteoblasts (OBs). Without osteogenic supplements, MSCs committed into bone lineage forming thus 3D bone-like nodules after 21 days. Despite a weak percentage of cell commitment, our data elucidate new aspects of osteoinductive material effect on MSCs functions through the regulation of the secretion of mediators involved in bone regeneration and subsequently the MSCs/ECs indirect crosstalk with osteogenesis-boosting effect. Using MSCs culture media, we demonstrate a large potential of osteoinductive materials and MSCs in bone regenerative medicine. Such strategies could help to address some insights in cell-free therapies using MSCs derived media.

Rapid fabrication of vascularized and innervated cell-laden bone models with biomimetic intrafibrillar collagen mineralization

Bone tissue, by definition, is an organic–inorganic nanocomposite, where metabolically active cells are embedded within a matrix that is heavily calcified on the nanoscale. Currently, there are no strategies that replicate these definitive characteristics of bone tissue. Here we describe a biomimetic approach where a supersaturated calcium and phosphate medium is used in combination with a non-collagenous protein analog to direct the deposition of nanoscale apatite, both in the intra- and extrafibrillar spaces of collagen embedded with osteoprogenitor, vascular, and neural cells. This process enables engineering of bone models replicating the key hallmarks of the bone cellular and extracellular microenvironment, including its protein-guided biomineralization, nanostructure, vasculature, innervation, inherent osteoinductive properties (without exogenous supplements), and cell-homing effects on bone-targeting diseases, such as prostate cancer. Ultimately, this approach enables fabrication of bone-like tissue models with high levels of biomimicry that may have broad implications for disease modeling, drug discovery, and regenerative engineering.

Bone tissue is a complex organic-inorganic nanocomposite and strategies that replicate the characteristics of bone tissue are scarce. Here the authors demonstrate the deposition of nanoscale apatite in collagen embedded with mesenchymal, vascular and nerve cells, using a protein-guided biomineralization approach.

Live Simultaneous Monitoring of Mineral Deposition and Lipid Accumulation in Differentiating Stem Cells

Mesenchymal stem cells (MSCs) are progenitors for bone-forming osteoblasts and lipid-storing adipocytes, two major lineages co-existing in bone marrow. When isolated in vitro, these stem cells recapitulate osteoblast or adipocyte formation if treated with specialised media, modelling how these lineages interact in vivo. Osteogenic differentiation is characterised by mineral deposits accumulating in the extracellular matrix, typically assessed using histological techniques. Adipogenesis occurs with accumulation of intracellular lipids that can be routinely visualised by Oil Red O staining. In both cases, staining requires cell fixation and is thus limited to end-point assessments. Here, a vital staining approach was developed to simultaneously detect mineral deposits and lipid droplets in differentiating cultures. Stem cells induced to differentiate produced mixed cultures containing adipocytes and bone-like nodules, and after two weeks live cultures were incubated with tetracycline hydrochloride and Bodipy to label mineral- and lipid-containing structures, respectively. Fluorescence microscopy showed the simultaneous visualisation of mineralised areas and lipid-filled adipocytes in live cultures. Combined with the nuclear stain Hoechst 33258, this approach further enabled live confocal imaging of adipogenic cells interspersed within the mineralised matrix. This multiplex labelling was repeated at subsequent time-points, demonstrating the potential of this new approach for the real-time high-precision imaging of live stem cells.

Drug-loaded/grafted peptide-modified porous PEEK to promote bone tissue repair and eliminate bacteria

Bone restoration and related infection in bone defect repair remain thorny problems in clinical practice. Herein, a drug-loaded (chlorogenic acid, CGA)/grafted peptide (BFP) hydrogel system supported on a sulfonated polyetheretherketone (SPEEK) surface is constructed to address the problem of large-scale defects and related infections in clinical bone implantation. Briefly, the encapsulated chlorogenic acid is released during hydrogel degradation and can inhibit the growth of bacteria and provide a bacteria-free environment for new bone formation. In vitro experiments and cell adhesion/proliferation evaluation reveal that the chlorogenic acid-sodium alginate-peptide bridging system shows better bioaffinity than the control groups due to the BFP peptide on the surface of the hydrogel. In addition, bacterial experiments suggest that the released chlorogenic acid has excellent antibacterial activity against gram-negative and gram-positive bacteria. Therefore, the hydrogel bridging system has a prospective application in clinical applications for bone repair.

Multiscale analyses reveal native-like lamellar bone repair and near perfect bone-contact with porous strontium-loaded bioactive glass

The efficient healing of critical-sized bone defects using synthetic biomaterial-based strategies is promising but remains challenging as it requires the development of biomaterials that combine a 3D porous architecture and a robust biological activity. Bioactive glasses (BGs) are attractive candidates as they stimulate a biological response that favors osteogenesis and vascularization, but amorphous 3D porous BGs are difficult to produce because conventional compositions crystallize during processing. Here, we rationally designed a porous, strontium-releasing, bioactive glass-based scaffold (pSrBG) whose composition was tailored to deliver strontium and whose properties were optimized to retain an amorphous phase, induce tissue infiltration and encourage bone formation. The hypothesis was that it would allow the repair of a critical-sized defect in an ovine model with newly-formed bone exhibiting physiological matrix composition and structural architecture. Histological and histomorphometric analyses combined with indentation testing showed pSrBG encouraged near perfect bone-to-material contact and the formation of well-organized lamellar bone. Analysis of bone quality by a combination of Raman spectral imaging, small-angle X-ray scattering, X-ray fluorescence and focused ion beam-scanning electron microscopy demonstrated that the repaired tissue was akin to that of normal, healthy bone, and incorporated small amounts of strontium in the newly formed bone mineral. These data show the potential of pSrBG to induce an efficient repair of critical-sized bone defects and establish the importance of thorough multi-scale characterization in assessing biomaterial outcomes in large animal models.

Bone quality assessment of osteogenic cell cultures by Raman microscopy

The use of autologous stem/progenitor cells represents a promising approach to the repair of craniofacial bone defects. The calvarium is recognized as a viable source of stem/progenitor cells that can be transplanted in vitro to form bone. However, it is unclear if bone formed in cell culture is similar in quality to that found in native bone. In this study, the quality of bone mineral formed in osteogenic cell cultures were compared against calvarial bone from postnatal mice. Given the spectroscopic resemblance that exists between cell and collagen spectra, the feasibility of extracting information on cell activity and bone matrix quality were also examined. Stem/progenitor cells isolated from fetal mouse calvaria were cultured onto fused-quartz slides under osteogenic differentiation conditions for 28 days. At specific time intervals, slides were removed and analyzed by Raman microscopy and mineral staining techniques. We show that bone formed in culture at Day 28 resembled calvarial bone from 1-day-old postnatal mice with comparable mineralization, mineral crystallinity, and collagen crosslinks ratios. In contrast, bone formed at Day 28 contained a lower degree of ordered collagen fibrils compared with 1-day-old postnatal bone. Taken together, bone formed in osteogenic cell culture exhibited progressive matrix maturation and mineralization but could not fully replicate the high degree of collagen fibril order found in native bone.

Nanolamellar Tantalum Interfaces in the Osteoblast Adhesion

The design of topographically patterned surfaces is considered to be a preferable approach for influencing cellular behavior in a controllable manner, in particular to improve the osteogenic ability of bone regeneration. In this study, we fabricated nanolamellar tantalum (Ta) surfaces with lamellar wall thicknesses of 40 and 70 nm. The cells attached to nanolamellar Ta surfaces exhibited higher protein adsorption and expression of β1 integrin, as compared to the nonstructured bulk Ta, which facilitated the initial cell attachment and spreading. We thus, as expected, observed significantly enhanced osteoblast adhesion, growth, and alkaline phosphatase activity on nanolamellar Ta surfaces. However, the beneficial effects of nanolamellar structures on osteogenesis became weaker as the lamellar wall thickness increased. The interaction between cells and Ta surfaces was examined through adhesion forces using atomic force microscopy. Our findings indicated that the Ta surface with a lamellar wall thickness of 40 nm exhibited the strongest stimulatory effect. The observed strongest adhesion force between the cell-attached tip and the Ta surface with a 40 nm thick lamellar wall encouraged the much stronger binding of cells with the surface and thus well-attached, -stretched, and -grown cells. We attributed this to the increase in the available contact area of cells with the thinner nanolamellar Ta surface. The increased contact area allowed the enhancement of the cell surface interaction strength and, thus, improved osteoblast adhesion. This study suggests that the thin nanolamellar topography shows immense potential in improving the clinical performance of dental and orthopedic implants.

Bone Tissue Engineering Using Human Cells: A Comprehensive Review on Recent Trends, Current Prospects, and Recommendations

The use of proper cells for bone tissue engineering remains a major challenge worldwide. Cells play a pivotal role in the repair and regeneration of the bone tissue in vitro and in vivo. Currently, a large number of differentiated (somatic) and undifferentiated (stem) cells have been used for bone reconstruction alone or in combination with different biomaterials and constructs (e.g., scaffolds). Although the results of the cell transplantation without any supporting or adjuvant material have been very effective with regard to bone healing. Recent advances in bone scaffolding are now becoming new players affecting the osteogenic potential of cells. In the present study, we have critically reviewed all the currently used cell sources for bone reconstruction and discussed the new horizons that are opening up in the context of cell-based bone tissue engineering strategies.

Raman Microscopy and Bone

Raman microscopy is a nondestructive technique requiring minimal sample preparation that can be used to measure the chemical properties of the mineral and collagen parts of bone simultaneously. Modern Raman instruments contain the necessary components and software to acquire the standard information required in most bone studies. The spatial resolution of the technique is about a micron. As it is nondestructive and small samples can be used, it forms a useful part of a bone characterization toolbox.

Strontium/adiponectin co-decoration modulates the osteogenic activity of nano-morphologic polyetheretherketone implant

Polyetheretherketone (PEEK)-based implants have become popular in hard tissue orthopedic and dental field. However, its inherent bio-inertness limited its applications for bone repair/substitution of osteoporosis patients, with poor osteogenesis capability. In order to ameliorate their bioactivity, the 3D porous PEEK substrate was created by sulfonate processing, and the substrate was subsequently incorporated with strontium (Sr) through a hydrothermal reaction in Sr(OH)₂ solutions. The adiponectin (APN) protein membrane was deposited on the substrate via polydopamine-assisted deposition. Surface characterization results disclosed that the nanostructures had been formed on sPEEK-Sr-APN surafces, and APN coatings on the substrates could adjust Sr release rate and further mediate cell-material interactions. in vitro experiments indicated that the cellular effects (proliferation and differentiation) of MC3T3-E1 were significantly increased with Sr/APN coordinated regulation. This study provides bioactive Sr and APN as promising active components for bio-functional bone regeneration/substitution, and optimizes the osteointegration of PEEK implants in clinic.

Site-specific differences in osteoblast phenotype, mechanical loading response and estrogen receptor-related gene expression

The osteoporosis-resistant nature of skull bones implies inherent differences exist between their cellular responses and those of other osteoporosis-susceptible skeletal sites. Phenotypic differences in calvarial and femoral osteoblastic responses to induction of osteogenesis, mechanical loading, estrogen, growth factor and cytokine stimulation were investigated. Primary rat calvarial and femoral adult male osteoblasts were cultured and osteoblastic mineralisation and maturation determined using Alizarin Red staining and expression of osteogenic marker genes assessed. Expression of known mechanically-responsive genes was compared between sites following loading of scaffold-seeded cells in a bioreactor. Cell proliferation and differentiation following growth factor and estrogen stimulation were also compared. Finally expression of estrogen receptors and associated genes during osteogenic differentiation were investigated. Calvarial osteoblasts exhibited delayed maturation (45d. vs 21d.) and produced less mineralised matrix than femoral osteoblasts when osteogenically induced. PDGF-BB and FGF2 both caused a selective increase in proliferation and decrease in osteoblastic differentiation of femoral osteoblasts. Mechanical stimulation resulted in the induction of the expression of Ccl2 and Anx2a selectively in femoral osteoblasts, but remained unchanged in calvarial cells. Estrogen receptor beta expression was selectively upregulated 2-fold in calvarial osteoblasts. Most interestingly, the estrogen responsive transcriptional repressor RERG was constitutively expressed at 1000-fold greater levels in calvarial compared with femoral osteoblasts. RERG expression in calvarial osteoblasts was down regulated during osteogenic induction whereas upregulation occurred in femoral osteoblasts. Bone cells of the skull are inherently different to those of the femur, and respond differentially to a range of stimuli. These site-specific differences may have important relevance in the development of strategies to tackle metabolic bone disorders.