Human Mesenchymal Stem Cell Morphology and Migration on Microtextured Titanium

Porous 3D Printed Titanium Cages in Anterior Cervical Discectomy and Fusion are Associated With Less Subsidence, Improved Maintenance of Segmental Lordotic Correction, and Similar Clinical Outcomes as Allograft

STUDY-DESIGN

Retrospective chart review.

OBJECTIVES

Investigate radiographic and clinical outcomes of 3D printed titanium cages (3DTC) vs allograft in patients undergoing Anterior cervical discectomy and fusion (ACDF).

METHODS

Consecutive series of patients undergoing ACDF with 3DTC were compared to patients using corticocancellous allograft. Cage subsidence, fusion status, sagittal alignment, and patient-reported-outcomes. Radiographic evaluation was performed on the closing intraoperative x-ray and compared to films at 6-weeks, 6-months, and 1-year. Cage subsidence was calculated based on the amount of settling into superior and inferior endplates compared to the intraoperative x-ray. Fusion was assessed based on < 1 mm of flexion/extension motion. Sagittal alignment parameters and patient-reported-outcomes were measured.

RESULTS

Seventy six-patients/(120 levels) in 3DTC group and 77-patients/(115 levels) in allograft group were evaluated. No significant differences were noted in patient demographics, level fused or the number of levels fused between the groups. The most common level fused was C5-6. 3DTC had a significantly lower subsidence rate at all-time points as compared to allograft (P < .001). 3DTC maintained segmental lordosis better than allograft at all-time points including 1-year postop (P < .001). No significant differences were noted in fusion rate for 3DTC vs allograft at 6-months (P > .05). There were no significant differences in patient-reported-outcomes.

CONCLUSION

3D printed titanium cages had similar patient-reported outcomes and fusion rates as allograft, but less subsidence at all-time points. 3D printed titanium cages better maintained the segmental lordosis at the operative level at all-time points. Although longer term evaluation is needed, based on these results, 3DTC appear to be viable graft options for ACDF that better maintain disc space height and improve segmental lordotic interbody correction.

Multi-DNA-Modified Double-Network Hydrogel with Customized Microstructure: A Novel System for Living Circulating Tumor Cells Capture and Real-Time Detection

The precise and effective isolation of living circulating tumor cells (CTCs) from peripheral blood, followed by their real-time monitoring, is crucial for diagnosing cancer patients. In this study, a cell-imprinted double-network (DN) hydrogel modified with circular multi-DNA (CMD), coined the CMD-imprinted hydrogel with fixed cells as templates (CMD-CIDH), was developed. The hydrogel featured a customized surface for proficient capture of viable CTCs and in situ real-time fluorescent detection without subsequent release. The customized surface, constructed using polyacrylamide/chitosan DN hydrogel as the matrix on the cell template, had a dense network structure, thereby ensuring excellent stability and a low degradation rate. Optimal capture efficiencies, recorded at 93 ± 3% for MCF-7 cells and 90 ± 2% for Hela cells, were achieved by grafting the CMD and adjusting the nodule size on the customized surface. The capture efficiency remained significantly high at 67 ± 11% in simulated breast cancer patient experiments even at a minimal concentration of 5 cells mL-1. Furthermore, CMD grafted onto the surface produced a potent fluorescence signature, enabling in situ real-time fluorescent detection of the target cell's growth state even in complex environments. The customized surface is highly efficient for screening CTCs in peripheral blood and has promising potential for setting up the CTCs culture.

Reducing Cancer Cell Adhesion using Microtextured Surfaces

For the past century, trypsin has been the primary method of cell dissociation, largely without any major changes to the process. Enzymatic cell detachment strategies for large-scale cell culturing processes are popular but can be labor-intensive, potentially lead to the accumulation of genetic mutations, and produce large quantities of liquid waste. Therefore, engineering surfaces to lower cell adhesion strength could enable the next generation of cell culture surfaces for delicate primary cells and automated, high-throughput workflows. In this study, a process for creating microtextured polystyrene (PS) surfaces to measure the impact of microposts on the adhesion strength of cells is developed. Cell viability and proliferation assays show comparable results in two cancer cell lines between micropost surfaces and standard cell culture vessels. However, cell image analysis on microposts reveals that cell area decreases by half, and leads to an average twofold increase in cell length per area. Using a microfluidic-based method up to a seven times greater percentage of cells are removed from micropost surfaces than the flat control surfaces. These results show that micropost surfaces enable decreased cell adhesion strength while maintaining similar cell viabilities and proliferation as compared to flat PS surfaces.

Rotary Jet-Spun Polycaprolactone/Hydroxyapatite and Carbon Nanotube Scaffolds Seeded with Bone Marrow Mesenchymal Stem Cells Increase Bone Neoformation

Clinically, bone tissue replacements and/or bone repair are challenging. Strategies based on well-defined combinations of osteoconductive materials and osteogenic cells are promising to improve bone regeneration but still require improvement. Herein, we combined polycaprolactone (PCL) fibers, carbon nanotubes (CNT), and hydroxyapatite (nHap) nanoparticles to develop the next generation of bone regeneration material. Fibers formed by rotary jet spinning (RJS) instead of traditional electrospinning (ES) with embedded bone marrow mesenchymal stem cells (BMMSCs) showed the best outcomes to repair rat calvarial defects after 6 weeks. To understand this, it was observed that different morphologies were formed depending on the manufacturing method used. RJS fibers presented a particular topography with rough fibers, which allowed for better cellular growth and cell spreading in vitro around and into a three-dimensional (3D) mesh, while fibers made by ES were more smooth and cellular growth was only measured on the 3D mesh surface. The fibers with incorporated nHap/CNT nanoparticles enhanced in vitro cell performance as indicated by more cellular proliferation, alkaline phosphatase activity, proliferation, and deposition of calcium. Greater bone neoformation occurred by combining three characteristics: the presence of nHap and CNT nanoparticles, the topography of the RJS fibers, and the addition of BMMSCs. RJS fibers with nanoparticles and seeded with BMMSCs showed 10 136 mm³ of bone neoformation, meaning a 10-fold increase compared to using RJS only and BMMSCs (0.853 mm³) and a 5-fold increase from using ES only (2054 mm³) after 6 weeks of implantation. Conversely, none of these approaches used individually showed any significant difference for in vivo bone neoformation, suggesting that their combination is essential for optimizing bone formation. In summary, our work generated a potential material composed of well-defined combinations of suitable scaffolds seeded with BMMSCs for enhancing numerous orthopedic tissue engineering applications.

Nanoscale Modification of Titanium Implants Improves Behaviors of Bone Mesenchymal Stem Cells and Osteogenesis In Vivo

The surficial micro/nanotopography and physiochemical properties of titanium implants are essential for osteogenesis. However, these surface characters' influence on stem cell behaviors and osteogenesis is still not fully understood. In this study, titanium implants with different surface roughness, nanostructure, and wettability were fabricated by further nanoscale modification of sandblasted and acid-etched titanium (SLA: sandblasted and acid-etched) by H₂O₂ treatment (hSLAs: H₂O₂ treated SLA). The rat bone mesenchymal stem cells (rBMSCs: rat bone mesenchymal stem cells) are cultured on SLA and hSLA surfaces, and the cell behaviors of attachment, spreading, proliferation, and osteogenic differentiation are further analyzed. Measurements of surface characteristics show hSLA surface is equipped with nanoscale pores on microcavities and appeared to be hydrophilic. In vitro cell studies demonstrated that the hSLA titanium significantly enhances cell response to attachment, spreading, and proliferation. The hSLAs with proper degree of H₂O₂ etching (h1SLA: treating SLA with H₂O₂ for 1 hour) harvest the best improvement of differentiation of rBMSCs. Finally, the osteogenesis in beagle dogs was tested, and the h1SLA implants perform much better bone formation than SLA implants. These results indicate that the nanoscale modification of SLA titanium surface endowing nanostructures, roughness, and wettability could significantly improve the behaviors of bone mesenchymal stem cells and osteogenesis on the scaffold surface. These nanoscale modified SLA titanium scaffolds, fabricated in our study with enhanced cell affinity and osteogenesis, had great potential for implant dentistry.

Nanofiber curvature with Rho GTPase activity increases mouse embryonic fibroblast random migration velocity

Mechanotransduction arises from information encoded in the shape of materials such as curvature. It induces activation of small GTPase signaling affecting cell phenotypes including differentiation. We carried out a set of preliminary experiments to test the hypothesis that curvature (1/radius) would also affect cell motility due to signal pathway crosstalk. High molecular weight poly (methyl methacrylate) straight nanofibers were electrospun with curvature ranging from 41 to 1 μm-1 and collected on a passivated glass substrate. The fiber curvature increased mouse mesenchymal stem cell aspect ratio (P < 0.02) and decreased cell area (P < 0.01). Despite little effect on some motility patterns such as polarity and persistence, we found selected fiber curvatures can increase normalized random fibroblastic mouse embryonic cell (MEF) migration velocity close to 2.5 times compared with a flat surface (P < 0.001). A maximum in the velocity curve occurred near 2.5 μm-1 and may vary with the time since initiation of attachment to the surface (range of 0-20 h). In the middle range of fiber curvatures, the relative relationship to curvature was similar regardless of treatment with Rho-kinase inhibitor (Y27632) or cdc42 inhibitor (ML141), although it was decreased on most curvatures (P < 0.05). However, below a critical curvature threshold MEFs may not be able to distinguish shallow curvature from a flat surface, while still being affected by contact guidance. The preliminary data in this manuscript suggested the large low curvature fibers were interpreted in a manner similar to a non-curved surface. Thus, curvature is a biomaterial construct design parameter that should be considered when specific biological responses are desired. Statement of integration, innovation, and insight  Replacement of damaged or diseased tissues that cannot otherwise regenerate is transforming modern medicine. However, the extent to which we can rationally design materials to affect cellular outcomes remains low. Knowing the effect of material stiffness and diameter on stem cell differentiation, we investigated cell migration and signaling on fibrous scaffolds. By investigating diameters across orders of magnitude (50-2000 nm), we identified a velocity maximum of ~800 nm. Furthermore, the results suggest large fibers may not be interpreted by single cells as a curved surface. This work presents insight into the design of constructs for engineering tissues.

Can activated titanium interbody cages accelerate or enhance spinal fusion? a review of the literature and a design for clinical trials

While spinal interbody cage options have proliferated in the past decade, relatively little work has been done to explore the comparative potential of biomaterial technologies in promoting stable fusion. Innovations such as micro-etching and nano-architectural designs have shown purported benefits in in vitro studies, but lack clinical data describing their optimal implementation. Here, we critically assess the pre-clinical data supportive of various commercially available interbody cage biomaterial, topographical, and structural designs. We describe in detail the osteointegrative and osteoconductive benefits conferred by these modifications with a focus on polyetheretherketone (PEEK) and titanium (Ti) interbody implants. Further, we describe the rationale and design for two randomized controlled trials, which aim to address the paucity of clinical data available by comparing interbody fusion outcomes between either PEEK or activated Ti lumbar interbody cages. Utilizing dual-energy computed tomography (DECT), these studies will evaluate the relative implant-bone integration and fusion rates achieved by either micro-etched Ti or standard PEEK interbody devices. Taken together, greater understanding of the relative osseointegration profile at the implant-bone interface of cages with distinct topographies will be crucial in guiding the rational design of further studies and innovations.

Nanostructure and biomimetics orchestrate mesenchymal stromal cell differentiation: An in vitro bioactivity study on new coatings for orthopedic applications

The choice of the appropriate material having suitable compositional and morphological surface characteristics, is a crucial step in the development of orthopedic implants. The purpose of this paper is to elucidate, on this regard, the influence of two important hits, i.e., biogenic apatite with bone-like composition and nanostructured morphology, providing the evidence of the efficacy of nanostructured biogenic apatite coatings in favoring adhesion, growth, proliferation, and in vitro osteogenic differentiation of human mesenchymal stromal cells (hMSCs) isolated from the bone marrow. The specific features of this coating in terms of topographical and biochemical cues, obtained by Ionized Jet Deposition, are perceived by hMSCs, as suggested by changes in different morphologic parameters as Aspect Ratio or Elongation index, suggesting the impact exerted by the nanostructure on early adhesion events, cytoskeleton organization, and cells fate. In addition, the nanostructured CaP coating sustained the metabolic activity of the cells and facilitated the osteogenic differentiation of MSC by supporting the osteogenesis-related gene expression. These findings support the use of a combined approach between technological advancement and instructive surfaces, both from the topographical and the biochemical point of view, in order to manufacture smart biomaterials able to respond to different needs of the orthopedic practice.

Biophysical phenotyping of mesenchymal stem cells along the osteogenic differentiation pathway

Mesenchymal stem cells represent an important resource, for bone regenerative medicine and therapeutic applications. This review focuses on new advancements and biophysical tools which exploit different physical and chemical markers of mesenchymal stem cell populations, to finely characterize phenotype changes along their osteogenic differentiation process. Special attention is paid to recently developed label-free methods, which allow monitoring cell populations with minimal invasiveness. Among them, quantitative phase imaging, suitable for single-cell morphometric analysis, and nanoindentation, functional to cellular biomechanics investigation. Moreover, the pool of ion channels expressed in cells during differentiation is discussed, with particular interest for calcium homoeostasis.Altogether, a biophysical perspective of osteogenesis is proposed, offering a valuable tool for the assessment of the cell stage, but also suggesting potential physiological links between apparently independent phenomena.

Symphytum officinale augments osteogenesis in human bone marrow-derived mesenchymal stem cells in vitro as they differentiate into osteoblasts

ETHNOPHARMACOLOGICAL RELEVANCE

Mesenchymal stem cells (MSCs) are multipotent stem cells possessing regenerative potential. Symphytum officinale (SO) is a medicinal plant and in homoeopathic literature, believed to accelerate bone healing.

AIM OF THE STUDY

This study aimed to determine if homoeopathic doses of SO could augment osteogenesis in MSCs as they differentiate into osteoblasts in vitro.

MATERIALS AND METHODS

Bone marrow samples were obtained from patients who underwent bone grafting procedures (n = 15). MSCs were isolated, expanded and characterized by flow cytometry (CD90, CD105). Cytotoxicity of SO was evaluated by MTT assay. Osteogenic differentiation was induced in MSCs with β-glycerophosphate, ascorbic acid and dexamethasone over 2 weeks. Different homoeopathic doses of SO (MT, 3C, 6C, 12C and 30C) were added to the basic differentiation medium (BDM) and efficiency of MSCs differentiating into osteoblasts were measured by evaluating expression of Osteocalcin using flow cytometry, and alkaline phosphatase activity using ELISA. Gene expression analyses for osteoblast markers (Runx-2, Osteopontin and Osteocalcin) were evaluated in differentiated osteoblasts using qPCR.

RESULTS

Flow cytometry (CD90, CD105) detected MSCs isolated from bone marrow (93-98%). MTT assay showed that the selected doses of SO did not induce any cytotoxicity in MSCs (24 hours). The efficiency of osteogenic differentiation (2 weeks) for different doses of Symphytum officinale was determined by flow cytometry (n = 10) for osteoblast marker, Osteocalcin, and most doses of Symphytum officinale enhanced osteogenesis. Interestingly, gene expression analysis for Runx-2 (n = 10), Osteopontin (n = 10), Osteocalcin (n = 10) and alkaline phosphatase activity (n = 8) also showed increased osteogenesis with the addition of Symphytum officinale to BDM, specially mother tincture.

CONCLUSIONS

Our findings suggest that homoeopathic dose (specially mother tincture) of Symphytum officinale has the potential to enhance osteogenesis.

Human mesenchymal stem cell morphology, migration, and differentiation on micro and nano-textured titanium

Orthopedic implants rely on facilitating a robust interaction between the implant material surface and the surrounding bone tissue. Ideally, the interface will encourage osseointegration with the host bone, resulting in strong fixation and implant stability. However, implant failure can occur due to the lack of integration with bone tissue or bacterial infection. The chosen material and surface topography of orthopedic implants are key factors that influence the early events following implantation and may ultimately define the success of a device. Early attachment, rapid migration and improved differentiation of stem cells to osteoblasts are necessary to populate the surface of biomedical implants, potentially preventing biofilm formation and implant-associated infection. This article explores these early stem cell specific events by seeding human mesenchymal stem cells (MSCs) on four clinically relevant materials: polyether ether ketone (PEEK), Ti6Al4V (smooth Ti), macro-micro rough Ti6Al4V (Endoskeleton®), and macro-micro-nano rough Ti6Al4V (nanoLOCK®). The results demonstrate the incorporation of a hierarchical macro-micro-nano roughness on titanium produces a stellate morphology typical of mature osteoblasts/osteocytes, rapid and random migration, and improved osteogenic differentiation in seeded MSCs. Literature suggests rapid coverage of a surface by stem cells coupled with stimulation of bone differentiation minimizes the opportunity for biofilm formation while increasing the rate of device integration with the surrounding bone tissue.

Canine amniotic membrane mesenchymal stromal/stem cells: Isolation, characterization and differentiation

The amniotic membrane can be considered as one of the sources of isolation of these cells, since it is found in the fetal maternal interface and has low immunogenicity. Mesenchymal stromal/stem cells (MSCs) have not been identified in canine amniotic membrane (AMC). Therefore, our objective was to isolate, culture, characterize and differentiate cells derived from canine amniotic membrane (AMC) and to verify its immunological and tumorigenic potential. For this, 12 dogs fetuses of each gestational age 32, 43 and 55 days were used, and the isolation and culture of the AMC were performed. We observed that the cells presented fibroblastoid morphology and high confluence even after freezing. We also observed that, when induced, they were able to differentiate into osteogenic, adipogenic, and chondrogenic cells, as well as being CD34- and CD105+. Regarding the immunological markers, we found that IL-1, IL-2, IL-6, IL-10 and MHC II were not expressed, whereas MHC I was expressed. After application of AMC cells in nude mice we can verify that there was no tumor formation. Based on this, we conclude that canine amniotic membrane is a good and accessible source for obtaining MSCs of low immunogenic and tumorigenic potential for veterinary therapeutic applications.

Bioactive Nanofibers Induce Neural Transdifferentiation of Human Bone Marrow Mesenchymal Stem Cells

The combination of biomaterials with stem cells is a promising therapeutic strategy to repair traumatic injuries in the central nervous system, and human bone marrow mesenchymal stem cells (BMSCs) offer a clinically translatable option among other possible sources of stem cells. We report here on the use of a supramolecular bioactive material based on a peptide amphiphile (PA), displaying a laminin-mimetic IKVAV sequence to drive neural transdifferentiation of human BMSCs. The IKVAV-PA self-assembles into supramolecular nanofibers that induce neuroectodermal lineage commitment after 1 week, as evidenced by the upregulation of the neural progenitor gene nestin ( NES) and glial fibrillary acidic protein ( GFAP). After 2 weeks, the bioactive IKVAV-PA nanofibers induce significantly higher expression of neuronal markers β-III tubulin (TUJ-1), microtubule-associated protein-2 (MAP-2), and neuronal nuclei (NEUN), as well as the extracellular matrix laminin (LMN). Furthermore, the human BMSCs exposed to the biomaterial reveal a polarized cytoskeletal architecture and a decrease in cellular size, resembling neuron-like cells. We conclude that the investigated supramolecular biomaterial opens the opportunity to transdifferentiate adult human BMSCs into neuronal lineage.

Human dental pulp stem cell adhesion and detachment in polycaprolactone electrospun scaffolds under direct perfusion

Cell adhesion in three-dimensional scaffolds plays a key role in tissue development. However, stem cell behavior in electrospun scaffolds under perfusion is not fully understood. Thus, an investigation was made on the effect of flow rate and shear stress, adhesion time, and seeding density under direct perfusion in polycaprolactone electrospun scaffolds on human dental pulp stem cell detachment. Polycaprolactone scaffolds were electrospun using a solvent mixture of chloroform and methanol. The viable cell number was determined at each tested condition. Cell morphology was analyzed by confocal microscopy after various incubation times for static cell adhesion with a high seeding density. Scanning electron microscopy images were obtained before and after perfusion for the highest flow rate tested. The wall pore shear stress was calculated for all tested flow rates (0.005–3 mL/min). An inversely proportional relationship between adhesion time with cell detachment under perfusion was observed. Lower flow rates and lower seeding densities reduced the drag of cells by shear stress. However, there was an operational limit for the lowest flow rate that can be used without compromising cell viability, indicating that a flow rate of 0.05 mL/min might be more suitable for the tested cell culture in electrospun scaffolds under direct perfusion.

Repositioning Titanium: An In Vitro Evaluation of Laser-Generated Microporous, Microrough Titanium Templates As a Potential Bridging Interface for Enhanced Osseointegration and Durability of Implants

Although titanium alloys remain the preferred biomaterials for the manufacture of biomedical implants today, such devices can fail within 15 years of implantation due to inadequate osseointegration. Furthermore, wear debris toxicity due to alloy metal ion release has been found to cause side-effects including neurotoxicity and chronic inflammation. Titanium, with its known biocompatibility, corrosion resistance, and high elastic modulus, could if harnessed in the form of a superficial scaffold or bridging device, resolve such issues. A novel three-dimensional culture approach was used to investigate the potential osteoinductive and osseointegrative capabilities of a laser-generated microporous, microrough medical grade IV titanium template on human skeletal stem cells (SSCs). Human SSCs seeded on a rough 90-µm pore surface of ethylene oxide-sterilized templates were observed to be strongly adherent, and to display early osteogenic differentiation, despite their inverted culture in basal conditions over 21 days. Limited cellular migration across the template surface highlighted the importance of high surface wettability in maximizing cell adhesion, spreading and cell-biomaterial interaction, while restricted cell ingrowth within the conical-shaped pores underlined the crucial role of pore geometry and size in determining the extent of osseointegration of an implant device. The overall findings indicate that titanium only devices, with appropriate optimizations to porosity and surface wettability, could yet play a major role in improving the long-term efficacy, durability, and safety of future implant technology.