Microvascular response of striated muscle to common arthroplasty-alloys: A comparativein vivo study with CoCrMo, Ti-6Al-4V, and Ti-6Al-7Nb

Impact of Metal Ions on Cellular Functions: A Focus on Mesenchymal Stem/Stromal Cell Differentiation

Metals play a crucial role in the human body, especially as ions in metalloproteins. Essential metals, such as calcium, iron, and zinc are crucial for various physiological functions, but their interactions within biological networks are complex and not fully understood. Mesenchymal stem/stromal cells (MSCs) are essential for tissue regeneration due to their ability to differentiate into various cell types. This review article addresses the effects of physiological and unphysiological, but not directly toxic, metal ion concentrations, particularly concerning MSCs. Overloading or unbalancing of metal ion concentrations can significantly impair the function and differentiation capacity of MSCs. In addition, excessive or unbalanced metal ion concentrations can lead to oxidative stress, which can affect viability or inflammation. Data on the effects of metal ions on MSC differentiation are limited and often contradictory. Future research should, therefore, aim to clarify the mechanisms by which metal ions affect MSC differentiation, focusing on aspects such as metal ion interactions, ion concentrations, exposure duration, and other environmental conditions. Understanding these interactions could ultimately improve the design of biomaterials and implants to promote MSC-mediated tissue regeneration. It could also lead to the development of innovative therapeutic strategies in regenerative medicine.

Development of In Vitro Endothelialised Stents - Review

Endovascular treatment is prevalent as a primary treatment for coronary and peripheral arterial diseases. Although the introduction of drug-eluting stents (DES) dramatically reduced the risk of in-stent restenosis, stent thrombosis persists as an issue. Notwithstanding improvements in newer generation DES, they are yet to address the urgent clinical need to abolish the late stent complications that result from in-stent restenosis and are associated with late thrombus formation. These often lead to acute coronary syndromes with high mortality in coronary artery disease and acute limb ischemia with a high risk of limb amputation in peripheral arterial disease. Recently, a significant amount of research has focused on alternative solutions to improve stent biocompatibility by using tissue engineering. There are two types of tissue engineering endothelialisation methods: in vitro and in vivo. To date, commercially available in vivo endothelialised stents have failed to demonstrate antithrombotic or anti-stenosis efficacy in clinical trials. In contrast, the in vitro endothelialisation methods exhibit the advantage of monitoring cell type and growth prior to implantation, enabling better quality control. The present review discusses tissue-engineered candidate stents constructed by distinct in vitro endothelialisation approaches, with a particular focus on fabrication processes, including cell source selection, stent material composition, stent surface modifications, efficacy and safety evidence from in vitro and in vivo studies, and future directions.

Endothelial and smooth muscle cells derived from human cardiac explants demonstrate angiogenic potential and suitable for design of cell-containing vascular grafts

Background

Endothelial and smooth muscle cells are considered promising resources for regenerative medicine and cell replacement therapy. It has been shown that both types of cells are heterogeneous depending on the type of vessels and organs in which they are located. Therefore, isolation of endothelial and smooth muscle cells from tissues relevant to the area of research is necessary for the adequate study of specific pathologies. However, sources of specialized human endothelial and smooth muscle cells are limited, and the search for new sources is still relevant. The main goal of our study is to demonstrate that functional endothelial and smooth muscle cells can be obtained from an available source—post-surgically discarded cardiac tissue from the right atrial appendage and right ventricular myocardium.

Methods

Heterogeneous primary cell cultures were enzymatically isolated from cardiac explants and then grown in specific endothelial and smooth muscle growth media on collagen IV-coated surfaces. The population of endothelial cells was further enriched by immunomagnetic sorting for CD31, and the culture thus obtained was characterized by immunocytochemistry, ultrastructural analysis and in vitro functional tests. The angiogenic potency of the cells was examined by injecting them, along with Matrigel, into immunodeficient mice. Cells were also seeded on characterized polycaprolactone/chitosan membranes with subsequent analysis of cell proliferation and function.

Results

Endothelial cells isolated from cardiac explants expressed CD31, VE-cadherin and VEGFR2 and showed typical properties, namely, cytoplasmic Weibel-Palade bodies, metabolism of acetylated low-density lipoproteins, formation of capillary-like structures in Matrigel, and production of extracellular matrix and angiogenic cytokines. Isolated smooth muscle cells expressed extracellular matrix components as well as α-actin and myosin heavy chain. Vascular cells derived from cardiac explants demonstrated the ability to stimulate angiogenesis in vivo. Endothelial cells proliferated most effectively on membranes made of polycaprolactone and chitosan blended in a 25:75 ratio, neutralized by a mixture of alkaline and ethanol. Endothelial and smooth muscle cells retained their functional properties when seeded on the blended membranes.

Conclusions

We established endothelial and smooth muscle cell cultures from human right atrial appendage and right ventricle post-operative explants. The isolated cells revealed angiogenic potential and may be a promising source of patient-specific cells for regenerative medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1156-1) contains supplementary material, which is available to authorized users.

Inflammatory response to implantation of transparent nanocrystalline yttria-stabilized zirconia using a dorsal window chamber model

The long-range goal of the windows to the brain (WttB) is to improve patient care by providing a technique for delivery and/or collection of light into/from the brain, on demand, over large areas, and on a chronically-recurring basis without the need for repeated craniotomies. To evaluate the potential of nanocrystalline yttria-stabilized-zirconia (nc-YSZ) cranial implant for optical therapy and imaging, in vivo biocompatibility was studied using the dorsal window chamber model in comparison with control (no implant) and commercially available cranial implant materials (PEEK and PEKK). The host tissue response to implant was characterized by using transillumination and fluorescent microscopy to measure leukocyte adhesion, blood vessel diameter, blood flow rate, and vascular permeability over two weeks. The results indicated the lack of inflammatory reaction of the host tissue to nc-YSZ at the microscopic level, suggesting that nc-YSZ is a good alternative material for cranial implants.

Bone mesenchymal stem cell functions on the hierarchical micro/nanotopographies of the Ti-6Al-7Nb alloy

We investigated the response of rat bone mesenchymal stem cells (BMSC) placed on the titanium-6aluminium-7niobiuim (Ti-6Al-7Nb) alloy modified by hydrofluoric acid etch combined with subsequent anodic oxidation. Pure titanium (Ti) discs and Ti-6Al-7Nb discs were treated by hydrofluoric acid etch and anodic oxidation, and polished pure Ti discs and Ti-6Al-7Nb discs without surface modification served as controls (n=35 in each group). Scanning electron microscopy, atomic force microscopy, and radiographic photoelectron spectroscopy assays were used to detect the properties of the samples' surface. The morphology, adhesion, proliferation, and alkaline phosphatase activity of BMSC were examined using various techniques of microscopic and biological characterisation. The results showed that both Ti-6Al-7Nb samples and the pure Ti samples showed hierarchical micro/nanotopographies, and fluorine emerged on the surfaces of the samples after modification. The hierarchical micro/nanotopographies significantly increased the spreading, adhesion, and proliferation of BMSC and activity of alkaline phosphatase. In addition, modified samples of Ti-6Al-7Nb showed significantly higher alkaline phosphatase activity than modified pure Ti samples (p<0.05). The experiment successfully confirmed that Ti-6Al-7Nb alloy with hierarchical micro/nanotopographies treated by hydrofluoric acid etch and anodic oxidation possessed good biocompatibility, and may be a promising candidate for dental implants.

Metal ions activate vascular endothelial cells and increase lymphocyte chemotaxis and binding

Metal on metal articulations in hip arthroplasty offer advantages, including lower volumetric wear compared to conventional metalonpolyethylene bearings, and increased resistance to dislocation. Reports described early failures, with histologic features similar to a Type IV immune response. Mechanisms by which metal wear products cause this reaction are not completely understood. We hypothesized a mechanism through direct activation of endothelial cells (ECs) by metal ions, resulting in both vasculitis and accumulation of lymphocytes without prior immune sensitization. Effects of metal ions were evaluated using human ECs in culture. Alterations in chemotactic proteins IL8 and MCP1 were assessed, as was upregulation of the adhesion molecule ICAM-1 and lymphocyte binding to ECs. Cobalt increased secretion of IL8 and MCP1 significantly, and upregulated the expression of ICAM-1 in ECs compared to stimulation by chromium and controls. Binding of lymphocytes to ECs and transEC migration were both significantly increased by cobalt but not chromium. These findings suggest that cobalt contributes more to the activation of ECs and lymphocyte binding than chromium without an allergic response. Some of the adverse tissue reactions to implants with components made of cobalt-chromium-molybdenium alloys may be due in part to activation of the endothelium by metal ions.

Improving cytocompatibility of Co28Cr6Mo by TiO2 coating: gene expression study in human endothelial cells

Cobalt-based materials are widely used for coronary stents, as well as bone and joint implants. However, their use is associated with high corrosion incidence. Titanium alloys, by contrast, are more biocompatible owing to the formation of a relatively inactive titanium oxide (TiO2) layer on their surface. This study was aimed at improving Co28Cr6Mo alloy cytocompatibility via sol-gel TiO2 coating to reduce metal corrosion and metal ion release. Owing to their role in inflammation and tissue remodelling around an implant, endothelial cells present a suitable in vitro model for testing the biological response to metallic materials. Primary human endothelial cells seeded on Co28Cr6Mo showed a stress phenotype with numerous F-actin fibres absent on TiO2-coated material. To investigate this effect at the gene expression level, cDNA microarray analysis of in total 1301 genes was performed. Compared with control cells, 247 genes were expressed differentially in the cells grown on Co28Cr6Mo, among them genes involved in proliferation, oxidative stress response and inflammation. TiO2 coating reduced the effects of Co28Cr6Mo on gene expression in endothelial cells, with only 34 genes being differentially expressed. Quantitative real-time polymerase chain reaction and protein analysis confirmed microarray data for selected genes. The effect of TiO2 coating can be, in part, attributed to the reduced release of Co(2+), because addition of CoCl2 resulted in similar cellular responses. TiO2 coating of cobalt-based materials, therefore, could be used in the production of cobalt-based devices for cardiovascular and skeletal applications to reduce the adverse effects of metal corrosion products and to improve the response of endothelial and other cell types.

The fatigue life of contoured cobalt chrome posterior spinal fusion rods

Intraoperative contouring of posterior rods in lumbar arthrodesis constructs introduces stress concentrations that can substantially reduce fatigue life. The sensitivity of titanium (Ti) and stainless steel (SS) to intraoperative contouring has been established in the literature; however, notch sensitivity has yet to be quantified for cobalt chrome (CoCr), which is now being advocated for use in posterior arthrodesis constructs. The goal of this study is to evaluate the sensitivity of CoCr rods to intraoperative contouring for posterior lumbar screwrod arthrodesis constructs. In this paper lumbar bilateral vertebrectomy models are constructed based on ASTM F1717-01 with curved rods (26-30 degrees total curvature) and poly-axial pedicle screws. Three types of constructs are assembled: first, 5.5 mm SS rods with SS screws (6.5 x 35 mm), second, 6.0 mm Ti rods with Ti screws (7.5 x 35 mm), and third, 6.0 mm CoCr rods with Ti screws (7.5 x 35 mm). All specimens are tested at 4 Hz in dynamic axial compression-bending with a load ratio of ten and maximum load levels of 250, 400, and 700 N until run-out at 2 000 000 cycles. Results are presented that show that the fatigue life of CoCr constructs tend to be greater than Ti constructs at all levels. At the 400 N maximum loading, CoCr lasts an average of 350 000 cycles longer than the Ti constructs. The CoCr constructs are able to sustain the 250 N load until run-out at 2 000 000 cycles but they fail at high load levels (maximum 700 N). The CoCr constructs fail at the neck of the Ti screw at high loads whereas Ti screws fail at the notch induced by contouring. Since CoCr is compatible with magnetic resonance imaging and has high static strength characteristics, the results of this study suggest that it may be an appropriate substitute for Ti.

Drug release from PLGA microspheres attached to solids using supercritical CO₂

Functionalization of a porous orthopedic implant with dexamethasone, a widely used anti-inflammatory drug, encapsulated within a biodegradable polymer for controlled release could help reduce or eliminate the inflammation response by the local tissue. In this research, we investigated the possibility of using supercritical carbon dioxide (CO₂) for attaching dexamethasone-loaded PLGA (polylactic-co-glycolic acid) microspheres to porous CoCrMo alloy for continuous delivery of dexamethasone. Supercritical CO₂ has been shown to be effective for attachment of PLGA microspheres to glass plates and porous CoCrMo alloy. Attached microspheres showed similar dexamethasone release profiles but different magnitude of burst release. Microspheres attached to the porous alloy samples using supercritical CO₂ at 10 bar and 40 °C for 30 min showed a release profile similar to that of the nonattached microspheres. The microsphere morphology and the release profiles of microspheres attached to the glass plates and to the porous alloy samples suggest that dexamethasone burst release is enhanced by PLGA swelling at higher CO₂ pressures and better dispersion of microspheres. This study shows that microspheres can be incorporated into porous solids using supercritical CO₂, allowing for a wide variety of drug-biodegradable polymer formulations prepared using the proven emulsion/solvent evaporation method to be tested.

Cell type-specific aspects in biocompatibility testing: the intercellular contact in vitro as an indicator for endothelial cell compatibility

Endothelial cells cover the inner surface of blood vessels and form the interface between the blood and the tissues. Endothelial cells are involved in regulating barrier function, which is maintained by the interendothelial cell contacts. These interendothelial cell contacts are established by the interaction of different molecules. The maintenance of the barrier requires an appropriate signalling between these molecules. Thus, a number of different signalling pathways are integrated within interendothelial contacts. Since endothelial cells are important in tissue-implant interactions (especially for stent materials) this study examines the expression pattern of different interendothelial contact molecules to determine the usefulness in the analysis of biocompatibility in vitro. The effects of different pro-inflammatory and toxic stimuli and contact of human microvascular endothelial cells to metallic surfaces were examined for their impact on the pattern of interendothelial contact molecules. Striking modifications in the arrangement of these molecules were induced and the mode of modification was dependent on the tested compound. Thus, examining the pattern of expression of specific interendothelial contact molecules in vitro may be useful for testing the endothelial cell compatibility of biomaterials and their corrosion products.

Prolene-Monocryl-composite meshes do not increase microvascular Staphylococcus aureus adherence and do not sensitize for leukocytic inflammation

BACKGROUND AND AIMS

Mesh implantation for hernia repair bears the risk of bacterial mesh infection. In this study, we analyzed whether this complication is supported by an increased interaction of bacteria and leukocytes with the microvascular endothelium at the implantation site.

MATERIALS AND METHODS

Ultrapro meshes were implanted into the dorsal skinfold chamber of Syrian golden hamsters. After 12 days, fluorescein isothiocyanate (FITC)-labeled staphylococci were injected in the animals. Subsequently, we analyzed bacterial adherence, leukocyte-endothelial cell interaction, and microhemodynamics in venules of the mesh border zone and of distant control tissue under baseline conditions and during TNF-alpha-induced inflammation using intravital fluorescence microscopy. The results were compared to animals which did not receive any bacteria.

RESULTS

Under baseline conditions, leukocyte-endothelial cell interaction and bacterial adherence were not affected by the implanted biomaterial. TNF-alpha-induced inflammation significantly increased numbers of adherent leukocytes and bacteria in venules located in direct vicinity to the mesh however without any differences to control tissue. Comparable results were found for the leukocyte-endothelial cell interaction when animals were not exposed to bacteria.

CONCLUSION

Implanted Ultrapro meshes do neither increase microvascular Staphylococcus aureus adherence nor sensitize for leukocytic inflammation. Thus, we suggest that a mesh-induced increase of bacterial adherence in vessels of the implantation site cannot be considered as a primary cause for the development of mesh infection.

Microvasculatory reaction of skeletal muscle to Ti-15Mo in comparison to well-established titanium alloys

Beta-titanium alloys such as Ti-15Mo are increasingly utilized for orthopaedic implant applications because of their excellent corrosion resistance and low elastic modulus. Particularly in osteosynthesis, where the biomaterial stands in direct contact to soft tissue, undesirable biologic reactions may have severe consequences especially in the vulnerable state of trauma and added iatrogenic damage to the microvascular system. In a comparative study we therefore assessed in vivo nutritive perfusion and leukocytic response of striated muscle to the biomaterials Ti-15Mo, Ti-6Al-4V and Ti-6Al-7Nb, thereby drawing conclusions on their short term inflammatory potential. Utilizing the well established skinfold chamber preparation in the hamster and intravital fluorescence microscopy, we could not demonstrate any significant discrepancies between the three alloys. All metals induced an initial moderate inflammatory response in skeletal muscle microcirculation. While recuperation of animals treated with Ti-15Mo and Ti-6Al-7Nb was prompt, we documented a slightly more sluggish recovery of Ti-6Al-4V treated animals. A gross toxicity was not observed for any of the alloys. Conclusively, Ti-15Mo, Ti-6Al-4V and Ti-6Al-7Nb induce an only transient inflammatory answer of the striated muscle microvascular system. Our results indicate that on the microvascular level the tested bulk Ti-alloys do not cause enduring biologic impairment in muscle.

Injectable nanocrystalline hydroxyapatite paste for bone substitution:In vivo analysis of biocompatibility and vascularization

The nanocrystalline hydroxyapatite paste Ostim represents a fully degradable synthetic bone substitute for the filling of bone defects. Herein, we investigated in vivo the inflammatory and angiogenic host tissue response to this biomaterial after implantation. For this purpose, Ostim was implanted into the dorsal skinfold chambers of Syrian golden hamsters. The hydroxyapatite ceramic Cerabone and isogeneic transplanted cancellous bone served as controls. Angiogenesis, microhemodynamics, microvascular permeability, and leukocyte-endothelial cell interaction of the host tissue were analyzed over 2 weeks using intravital fluorescence microscopy. Ostim exhibited good biocompatibility comparable to that of Cerabone and cancellous bone, as indicated by a lack of venular leukocyte activation after implantation. Cancellous bone induced a more pronounced angiogenic response and an increased microvessel density when compared with the synthetic bone substitutes. In contrast to Cerabone, however, Ostim showed a guided neovascularization directed toward areas of degradation. Histology confirmed the ingrowth of proliferating vascularized tissue into the hydroxyapatite paste at sites of degradation, while the hydroxyapatite ceramic was not pierced by new microvessels. Thus, Ostim represents an injectable synthetic bone substitute, which may optimize the conditions for the formation of new bone at sites of bone defects by supporting a guided vascularization during biodegradation.