Stem cell plasticity, osteogenic differentiation and the third dimension

Different cues present in the cellular environment control basic biological processes. A previously established 3D microwell array was used to study dimensionality-related effects on osteogenic differentiation and plasticity of marrow stromal cells. To enable long-term culture of single cells in the array a novel surface functionalization technique was developed, using the principle of subtractive micro contact printing of fibronectin and surface passivation with a triblock-copolymer. Immunohistochemical stainings showed that when cultivated in 3D microenvironments, marrow stromal cells can be maintained in the wells for up to 7days and be induced to commit to the osteogenic lineage. In conclusion, this work shows the modification of a 3D microwell array allowing the long term study of single stem cell plasticity and fate in controlled microenvironment

Multifunctional nano‐biointerfaces: cytocompatible antimicrobial nanocarriers from stabilizer‐free cubosomes

The rational design of alternative antimicrobial materials with reduced toxicity toward mammalian cells is highly desired due to the growing occurrence of bacteria resistant to conventional antibiotics. A promising approach is the design of lipid‐based antimicrobial nanocarriers. However, most of the commonly used polymer‐stabilized nanocarriers are cytotoxic. Herein, the design of a novel, stabilizer‐free nanocarrier for the human cathelicidin derived antimicrobial peptide LL‐37 that is cytocompatible and promotes cell proliferation for improved wound healing is reported. The nanocarrier is formed through the spontaneous integration of LL‐37 into novel, stabilizer‐free glycerol mono‐oleate (GMO)‐based cubosomes. Transformations in the internal structure of the cubosomes from Pn3m to Im3m‐type and eventually their transition into small vesicles and spherical micelles are demonstrated upon the encapsulation of LL‐37 into their internal bicontinuous cubic structure using small angle X‐ray scattering, cryogenic transmission electron microscopy, and light scattering techniques. Additional in vitro biological assays show the antimicrobial activity of the stabilizer‐free nano‐objects on a variety of bacteria strains, their cytocompatibility, and cell‐ proliferation enhancing effect. The results outline a promising strategy for the comprehensive design of antimicrobial, cytocompatible lipid nanocarriers for the protection and delivery of bioactive molecules with potential for application as advanced wound healing materials

Steering surface topographies of electrospun fibers: understanding the mechanisms

A profound understanding of how to tailor surface topographies of electrospun fibers is of great importance for surface sensitive applications including optical sensing, catalysis, drug delivery and tissue engineering. Hereby, a novel approach to comprehend the driving forces for fiber surface topography formation is introduced through inclusion of the dynamic solvent-polymer interaction during fiber formation. Thus, the interplay between polymer solubility as well as computed fiber jet surface temperature changes in function of time during solvent evaporation and the resultant phase separation behavior are studied. The correlation of experimental and theoretical results shows that the temperature difference between the polymer solution jet surface temperature and the dew point of the controlled electrospinning environment are the main influencing factors with respect to water condensation and thus phase separation leading to the final fiber surface topography. As polymer matrices with enhanced surface area are particularly appealing for sensing applications, we further functionalized our nanoporous fibrous membranes with a phosphorescent oxygen-sensitive dye. The hybrid membranes possess high brightness, stability in aqueous medium, linear response to oxygen and hence represent a promising scaffold for cell growth, contactless monitoring of oxygen and live fluorescence imaging in 3-D cell models

Magnetization transfer MR imaging to monitor muscle tissue formation during myogenic in vivo differentiation of muscle precursor cells

Purpose To determine whether magnetization transfer (MT) magnetic resonance (MR) imaging may serve as a quantitative measure of the degree of fiber formation during differentiation of muscle precursor cells into engineered muscle tissue as a potential noninvasive monitoring tool in mice. Materials and Methods The study was approved by the local ethics committee (no. StV 01/2008) and the local Veterinary Office (license no. 99/2013). Human muscle progenitor cells (hMPCs) derived from rectus abdominis muscles were subcutaneously injected into CD-1 nude mice (CD-1 nude mice, Crl:CD1-Foxn1(nu); Charles River Laboratories, Wilmington, Mass) for development of muscle tissue. The mice underwent MR imaging examinations at 4.7 T at days 1, 3, 7, 14, 21, and 28 after cell transplantation by using a gradient-echo sequence with an MT prepulse and systematic variation of the off-resonance frequency (50-37 500 Hz) at an amplitude of 800°. Direct saturation was estimated from a Bloch equation simulation. The MT ratio (MTR) was correlated to immunohistochemistry findings, Western blot results, and results of myography. Data were analyzed by using one-way or two-way analysis of variance with the Sidak or Tukey multiple comparisons test. Results In the reference skeletal muscle, highest MT was found for 2500 Hz off-resonance frequency with an MTR ± standard deviation of 57.5% ± 3.5. The developing muscle tissue exhibited increasing MT values during the 28 days of myogenic in vivo differentiation and did not reach the values of native skeletal muscle. Mean values of MTR (2500 Hz) for hMPCs were 27.6% ± 6.3 (day 1), 24.7% ± 8.7 (day 3), 28.2% ± 5.7 (day 7), 35.9% ± 5.0 (day 14), 37.0% ± 7.9 (day 21), and 39.9% ± 8.1 (day 28). The results from MT MR imaging correlated qualitatively well with muscle tissue expression of specific skeletal markers, as well as muscle contractility. Conclusion MT MR imaging may be used to noninvasively monitor the process of myogenic in vivo differentiation of hMPCs as a biomarker of the quantity and quality of muscle fiber formation. (©) RSNA, 2016 Online supplemental material is available for this article

Rationally designed ultra-short pulsed laser patterning of zirconia-based ceramics tailored for the bone-implant interface

Ceramic composite materials are increasingly used in dental restoration procedures, but current ceramic surface designs do not yet achieve the osseointegration potential of state-of-the-art titanium implants. Rapid bone tissue integration of an implant is greatly dependent on its surface characteristics, but the material properties of ceramic composite materials interfere with classical surface modification techniques. Here, ultra-short pulsed laser machining, which offers a defined energy input mitigating a heat-affected zone, is explored for surface modification of ceramic composites. Inspired by surface textures of clinically relevant titanium implants, dual roughness surfaces are laser patterned. Raman mapping reveals a negligible effect of ultra-short pulsed laser ablation on material properties, but a laser-induced change in the wetting state is revealed by static contact angle measurements. Laser patterning of surfaces also influences blood coagulation, but not the attachment and spreading of osteoblastic cells. The presented laser machining approach thus allows the introduction of a rational surface design on ceramic composites, holding great promise for the manufacturing of ceramic implants.ISSN:0169-4332ISSN:1873-558

Stem cell plasticity, osteogenic differentiation and the third dimension

ISSN:0957-4530ISSN:1573-483

Viability, Differentiation Capacity, and Detectability of Super-Paramagnetic Iron Oxide-Labeled Muscle Precursor Cells for Magnetic-Resonance Imaging

Cell therapies are a promising approach for the treatment of a variety of human conditions including stress urinary incontinence, but their success greatly depends on the biodistribution, migration, survival, and differentiation of the transplanted cells. Noninvasive in vivo cell tracking therefore presents an important aspect for translation of such a procedure into the clinics. Upon labeling with superparamagnetic iron oxide (SPIO) nanoparticles, cells can be tracked by magnetic resonance imaging (MRI), but possible adverse effect of the labeling have to be considered when labeling stem cells with SPIOs. In this study, human muscle precursor cells (hMPC) were labeled with increasing concentrations of SPIO nanoparticles (100-1600 μg/mL) and cell viability and differentiation capacity upon labeling was assessed in vitro. While a linear dependence between cell viability and nanoparticle concentration could be observed, differentiation capacity was not affected by the presence of SPIOs. Using a nude mouse model, a concentration (400 μg/mL) could be defined that allows reliable detection of hMPCs by MRI but does not influence myogenic in vivo differentiation to mature and functional muscle tissue. This suggests that such an approach can be safely used in a clinical setting to track muscle regeneration in patients undergoing cell therapy without negative effects on the functionality of the bioengineered muscle

MR imaging relaxometry allows noninvasive characterization of in vivo differentiation of muscle precursor cells

Purpose To demonstrate the feasibility of in vivo monitoring of the myogenic differentiation process from human muscle precursor cells to mature skeletal muscle tissue by measuring characteristic magnetic resonance (MR) imaging relaxation and diffusion properties as a potential noninvasive diagnostic tool in muscle cell therapy. Materials and Methods The study was approved by the ethics committee for studies in humans and the animal care committee. The hypothesis was tested by means of subcutaneous injection of human muscle precursor cells from the rectus abdominis muscle into nude mice (n = 18). Animals injected with human fibroblasts, prostate cancer cells, or collagen served as control animals (four in each group). T1, T2, T2*, and apparent diffusion coefficients ( ADC apparent diffusion coefficient s) were measured at 4.7-T MR imaging. MR imaging parameters were statistically evaluated by using analysis of variance with Bonferroni correction. The engineered muscle was characterized by means of immunofluorescence, Western blot, and contraction assays. Results Muscle tissue in the early stages of the differentiation process exhibited distinctly higher T1 (mean ± standard deviation, 2242 msec ± 116), T2 (224 msec ± 18), and T2* (33.3 msec ± 3.6) values and ADC apparent diffusion coefficient s (1.53 × 10(-3) mm(2)/sec ± 0.03) compared with those of skeletal muscle. The muscle precursor cells exhibited a nonspecific pattern compared with that in control animals in the early stages. During differentiation, the relaxation and diffusion parameters decreased and approached the values for mature skeletal muscle tissue: T1, 1386 msec ± 88; T2, 32.0 msec ± 4.3; T2*, 10.8 msec ± 0.8; ADC apparent diffusion coefficient , 1.39 × 10(-3) mm(2)/sec ± 0.02 (reference erector spinae muscle tissue: T1, 1417 msec ± 106; T2, 31.0 msec ± 2.4; T2*, 11.3 msec ± 1.7; and ADC apparent diffusion coefficient , 1.40 × 10(-3) mm(2)/sec ± 0.03). Conclusion MR imaging relaxation and diffusion measurements can be used as potential biomarkers for noninvasive in vivo monitoring of the myogenic differentiation process from muscle precursor cells to mature skeletal muscle tissue in muscle cell therapy. © RSNA, 2014 Online supplemental material is available for this article

Enhanced differentiation of human osteoblasts on Ti surfaces pre-treated with human whole blood

Early and effective integration of a metal implant into bone tissue is of crucial importance for its long-term stability. While different material properties including surface roughness and wettability but also initial blood-implant surface interaction are known to influence this osseointegration, implications of the latter process are still poorly understood. In this study, early interaction between blood and the implant surface and how this affects the mechanism of osseointegration were investigated. For this, blood coagulation on a micro-roughened hydrophobic titanium (Ti) surface (SLA-Hphob) and on a hydrophilic micro-roughened Ti surface with nanostructures (SLActive-HphilNS), as well as the effects of whole human blood pre-incubation of these two surfaces on the differentiation potential of primary human bone cells (HBC) was assessed. Interestingly, pre-incubation with blood resulted in a dense fibrin network over the entire surface on SLActive-HphilNS but only in single patches of fibrin and small isolated fiber complexes on SLA-Hphob. On SLActive-HphilNS, the number of HBCs attaching to the fibrin network was greatly increased and the cells displayed enhanced cell contact to the fibrin network. Notably, HBCs displayed increased expression of the osteogenic marker proteins alkaline phosphatase and collagen-I when cultivated on both surfaces upon blood pre-incubation. Additionally, blood pre-treatment promoted an earlier and enhanced mineralization of HBCs cultivated on SLActive-HphilNS compared to SLA-Hphob. The results presented in this study therefore suggest that blood pre-incubation of implant surfaces mimics a more physiological situation, eventually providing a more predictive in vitro model for the evaluation of novel bone implant surfaces