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"Neumann, Georg"
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Calcium phosphate surfaces promote osteogenic differentiation of mesenchymal stem cells
Although studies in vivo revealed promising results in bone regeneration after implantation of scaffolds together with osteogenic progenitor cells, basic questions remain how material surfaces control the biology of mesenchymal stem cells (MSC). We used human MSC derived from bone marrow and studied the osteogenic differentiation on calcium phosphate surfaces. In osteogenic differentiation medium MSC differentiated to osteoblasts on hydroxyapatite and BONITmatrix®, a degradable xerogel composite, within 14 days. Cells revealed a higher alkaline phosphatase (ALP) activity and increased RNA expression of collagen I and osteocalcin using real‐time RTPCR compared with cells on tissue culture plastic. To test whether material surface characteristics alone are able to stimulate osteogenic differentiation, MSC were cultured on the materials in expansion medium without soluble additives for osteogenic differentiation. Indeed, cells on calcium phosphate without osteogenic differentiation additives developed to osteoblasts as shown by increased ALP activity and expression of osteogenic genes, which was not the case on tissue culture plastic. Because we reasoned that the stimulating effect on osteogenesis by calcium phosphate surfaces depends on an altered cell–extracellular matrix interaction we studied the dynamic behaviour of focal adhesions using cells transfected with GFP labelled vinculin. On BONITmatrix®, an increased mobility of focal adhesions was observed compared with cells on tissue culture plastic. In conclusion, calcium phosphate surfaces are able to drive MSC to osteoblasts in the absence of osteogenic differentiation supplements in the medium. An altered dynamic behaviour of focal adhesions on calcium phosphate surfaces might be involved in the molecular mechanisms which promote osteogenic differentiation.
Journal Article
Gelatin-Based Hydrogels Promote Chondrogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stem Cells In Vitro
Due to the weak regeneration potential of cartilage, there is a high clinical incidence of articular joint disease, leading to a strong demand for cartilaginous tissue surrogates. The aim of this study was to evaluate a gelatin-based hydrogel for its suitability to support chondrogenic differentiation of human mesenchymal stem cells. Gelatin-based hydrogels are biodegradable, show high biocompatibility, and offer possibilities to introduce functional groups and/or ligands. In order to prove their chondrogenesis-supporting potential, a hydrogel film was developed and compared with standard cell culture polystyrene regarding the differentiation behavior of human mesenchymal stem cells. Cellular basis for this study were human adipose tissue-derived mesenchymal stem cells, which exhibit differentiation potential along the adipogenic, osteogenic and chondrogenic lineage. The results obtained show a promotive effect of gelatin-based hydrogels on chondrogenic differentiation of mesenchymal stem cells in vitro and therefore encourage subsequent in vivo studies.
Journal Article
He has opened Nisaba's house of learning : studies in honor of Åke Waldemar Sjöberg on the occasion of his 89th birthday on August 1st 2013
In He has Opened Nisaba's House of Learning twenty-six scholars honor Åke Sjöberg, former editor of the Pennsylvania Sumerian Dictionary, with studies on Mesopotamian literature, religion, and social, cultural and legal history, including previously unpublished texts.
eBook
EIN LUXUSOBJEKT MIT MILITÄRISCHEM NUTZEN
Pferde spielten im Alten Orient und in Ägypten seit jeher eine besondere Rolle. Sie galten auf Grund ihrer Seltenheit und der aufwendigen Zucht und Ausbildung als äußerst wertvoll und als Luxusgut. Nur die höchste Elite konnte sich Pferde leisten, daher wurden sie vor allem als Zugtiere von Streit- und Prunkwagen sowie in Vorderasien auch als Reittiere im Militär genutzt.
Journal Article
Mechanical characterization of anti-infectious, anti-allergic, and bioactive coatings on orthopedic implant surfaces
In total joint replacement much effort has been made to reduce implant loosening. We investigated different implant coatings (copper integrated titanium dioxide (TiO
2
–Cu), titanium nitride (TiN), plasma polymerized allylamine (PPAAm), and calcium phosphate (CaP)) regarding the adhesion strength and wear resistance. Standardized scratch and adhesive tests were applied. Abrasive wear was measured with artificial bone and bone cement using a special testing machine. All tested coatings have higher bonding strengths than the 22 N/mm
2
required for medical implant surface coatings by ASTM standard 4711-F. Using bone cement, wear testing revealed higher wear rates in most cases. Polished surfaces reduce the amount of wear, whereas rough surfaces highly increase the wear rate due to three-body wear, especially ceramic surfaces. In general, the application of bone cement in conjunction with modified implant surfaces can lead to an increase in wear rate.
Journal Article
Cellular investigations on electrochemically deposited calcium phosphate composites
Electrochemically deposited calcium phosphate (CaP) coatings are fast resorbable and existent only during the first period of osseointegration. In the present study, composite coatings with varying solubility (hydroxyapatite (HA), brushite with less HA and monetite (M) with less HA) were prepared and the influence of the degradation and the reprecipitation of CaP on osteoblastic cells were investigated. On the brushite composite coating a new precipitated, finely structured CaP phase was observed during immersion in cell culture medium with or without osteoblastic cells. The surface morphology of monetite and HA coatings were entirely unmodified under the same conditions. So it could be assumed that electrochemically deposited brushite with less HA acts as a precursor for new precipitated CaP. On this surface osteoblastic cells revealed a well-spread morphology with pronounced actin cytoskeleton and demonstrated good proliferation behaviour. Thus we suggest that brushite seems to be especially suitable for coating of implants as a matrix for nucleation and growth of new bone.
Journal Article
Assessment of the genetic stability of GMOs with a detailed examination of MON810 using Scorpion probes
For the cultivation and maintenance of seeds, genetic mutations have to be avoided as much as possible. According to the Directive 2001/18/EC, genetic stability has to be proven for the approval of GMOs [
1
]. The investigation of genetic stability can be performed with various methods, but Southern blots are most commonly used. In this study, a different method, a real-time PCR involving Scorpion primer, was developed for the analysis of DNA rearrangements in GMOs. The advantage of this method is that already small changes in sequence can be detected. In addition, large numbers of samples can be tested at once in a single PCR run. Possible alterations in the region of the Scorpion primer can be detected by differences in the real-time PCR plots. The sequence that was analysed contained 130 nucleotides. The sensitivity of Scorpion primers to measure genetic stability was verified in experiments with plasmids that had only minor sequence alterations in the target region. Such small differences led to a total reduction of the fluorescence signal, even in heterozygous samples where the unaltered template was present as well. Scorpion primers were then used to investigate the transgenic sequences of 567 individual seeds of MON810 for maize at the 5′ and the 3′ region of the insert. In combination with SYBR green, the screening procedure allowed a selection of samples for further analysis. If a sample showed low fluorescence with the Scorpion primer but a normal amplification with SYBR green, then the integrity of the insert was checked by sequencing. The results, however, gave no indication of a mutation or rearrangement of MON810 seeds. In additional experiments, the reliability of the method was studied by determining several parameters that are required for a validation, e.g., specificity, cross-reactivity, dynamic range, correlation of the template concentration and the corresponding Ct values, PCR efficiency, relative repeatability standard deviation (RSDr) relative reproducibility standard deviation (RSDR).
Journal Article
Evaluation of Adh1 alleles and transgenic soybean seeds using Scorpion PCR and HRM analysis
The identification of both approved and non-approved genetically modified organisms (GMOs) is an integral part of GMO biosafety legislation in many countries. One aspect that may affect PCR-based detection of a GMO lies within the analysis of its genetic stability, as sequence alterations or DNA instabilities may impede quantification by PCR. Genetic stability can be analyzed using various methods, yet many of these methods have distinct disadvantages, including low sensitivity. In this study, high resolution melting (HRM) analysis and real-time PCR with Scorpion primers were used as a method to analyze the 3′ end of RR soybeans (RR 40-3-2) in a large number of samples (
n
= 1,034). No evidence for the occurrence of mutation events was found, implying that the nucleotide sequence of this region is unlikely to be unstable and is well suited as a target for the quantification of RR soybeans. Additionally, and as a preparative work for an optimization of the method, a 174 bp region of the first intron of the Adh1 gene was analyzed in several varieties of maize with different GMO events using the same approach. The results show that 2 alleles are present. In further experiments, the different alleles were cloned into plasmids to generate homozygous plasmids from heterozygous templates in order to generate for a more precise analysis. The overall methodological aim of these studies was to compare HRM analysis with Scorpion primer PCR. Both methods were capable of differentiating between the 2 homozygous and heterozygous alleles. For a better discrimination, however, we conclude that it is most reliable to consider the results of both methods. This dual approach is assumed to be an effective tool as an accurate, high-throughput means of the screening of GMOs for potential genetic instabilities that may interfere with the detection and identification of specific GM events.
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