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Articles by Katja Schenke-Layland in JoVE
JoVE Bioengineering
Sem contato, Monitoramento Label livre de células e matriz extracelular utilizando Espectroscopia Raman
1Department of Thoracic and Cardiovascular Surgery and Inter-University Centre for Medical Technology Stuttgart-Tübingen (IZST), Eberhard Karls University, Tübingen, 2Department of Cell and Tissue Engineering, Fraunhofer Institute of Interfacial Engineering and Biotechnology (IGB) Stuttgart, Germany, 3Department for Medical Interfacial Engineering (IGVT), University of Stuttgart, Germany, 4Institute of Tissue Engineering and Regenerative Medicine, Julius-Maximillians University, Würzburg, Germany
A espectroscopia Raman é uma técnica adequada para o contato não, rótulo sem análise de células vivas, tecidos engenharia de construções e tecidos nativos. Fonte específicos impressões digitais espectrais podem ser gerados e analisados utilizando análise multivariada.
Other articles by Katja Schenke-Layland on PubMed
Collagen IV Induces Trophoectoderm Differentiation of Mouse Embryonic Stem Cells
The earliest segregation of lineages in the developing embryo is the commitment of cells to the inner cell mass or the trophoectoderm in preimplantation blastocysts. The exogenous signals that control commitment to a particular cell lineage are poorly understood; however, it has been suggested that extracellular "niche" and extracellular matrix, in particular, play an important role in determining the developmental fate of stem cells. Collagen IV (ColIV) has been reported to direct embryonic stem (ES) cell differentiation to mesodermal lineages in both mouse and human ES cells. To define the effects of ColIV on ES cell differentiation and to identify the resulting heterogeneous cell types, we performed microarray analyses and determined global gene expression. We observed that ColIV induced the expression of mesodermal genes specific to hematopoietic, endothelial, and smooth muscle cells and, surprisingly, also a panel of trophoectoderm-restricted markers. This effect was specific to collagen IV, as no trophoblast differentiation was seen on collagen I, laminin, or fibronectin. Stimulation with basic fibroblast growth factor (FGF) or FGF4 increased the number of trophoectodermal cells. These cells were isolated under clonal conditions and successfully differentiated into a variety of trophoblast derivatives. Interestingly, differentiation of ES cells to trophoblastic lineages was only seen in ES cell lines maintained on embryonic feeder layers and was caudal-type homeobox protein 2 (Cdx2)-dependent, consistent with Cdx2's postulated role in trophoectoderm commitment. Our data suggest that, given the appropriate extracellular stimuli, mouse embryonic stem cells can differentiate into trophoectoderm. Disclosure of potential conflicts of interest is found at the end of this article.
Reprogrammed Mouse Fibroblasts Differentiate into Cells of the Cardiovascular and Hematopoietic Lineages
Forced expression of the four transcription factors Oct4, Sox2, c-Myc, and Klf4 is sufficient to confer a pluripotent state upon the murine fibroblast genome, generating induced pluripotent stem (iPS) cells. Although the differentiation potential of these cells is thought to be equivalent to that of embryonic stem (ES) cells, it has not been rigorously determined. In this study, we sought to identify the capacity of iPS cells to differentiate into Flk1-positive progenitors and their mesodermal progeny, including cells of the cardiovascular and hematopoietic lineages. Immunostaining of tissues from iPS cell-derived chimeric mice demonstrated that iPS cells could contribute in vivo to cardiomyocytes, smooth muscle cells, endothelial cells, and hematopoietic cells. To compare the in vitro differentiation potential of murine ES and iPS cells, we either induced embryoid body (EB) formation of each cell type or cultured the cells on collagen type IV (ColIV), an extracellular matrix protein that had been reported to direct murine ES cell differentiation to mesodermal lineages. EB formation and exposure to ColIV both induced iPS cell differentiation into cells that expressed cardiovascular and hematopoietic markers. To determine whether ColIV-differentiated iPS cells contained a progenitor cell with cardiovascular and hematopoietic differentiation potential, Flk1-positive cells were isolated by magnetic cell sorting and exposed to specific differentiation conditions, which induced differentiation into functional cardiomyocytes, smooth muscle cells, endothelial cells, and hematopoietic cells. Our data demonstrate that murine iPS cells, like ES cells, can differentiate into cells of the cardiovascular and hematopoietic lineages and therefore may represent a valuable cell source for applications in regenerative medicine. Disclosure of potential conflicts of interest is found at the end of this article.
Identification of the Critical Extracellular Matrix Proteins That Promote Human Embryonic Stem Cell Assembly
Human embryonic stem cells (hESC) exist as large colonies containing tightly adherent, undifferentiated cells. Disaggregation of hESC as single cells significantly affects their survival and differentiation, suggesting that adhesion mechanisms are critical for the assembly and maintenance of hESC colonies. The goal of these studies was to determine the key extracellular matrix (ECM) components that regulate assembly and growth of hESC. Our studies demonstrate that undifferentiated hESC express a specific subtype of laminin (laminin-511) and nidogen-1. The addition of a purified protein complex comprised of human laminin-511 and nidogen-1 to single-cell suspensions of hESC is sufficient to restore hESC assembly in the absence of murine embryonic fibroblasts or exogenous chemicals. The mechanism of hESC aggregation is through binding of the alpha6beta1 integrin receptor highly expressed in the membranes of undifferentiated hESC; aggregation can be inhibited by an antibody against alpha6 and almost completely blocked by an antibody against the beta1 subunit. Reassembly of defined numbers of purified hESC with the laminin-nidogen complex allows consistent production of uniform embryoid bodies (EBs) ("LN-EBs") that differentiate into endodermal, ectodermal, and mesodermal derivatives, and are highly efficient in generating hematoendothelial progenitors. These data reveal for the first time the crucial role of the ECM proteins laminin-511 and nidogen-1 in hESC assembly, and provide a novel practical tool to investigate hESC differentiation in a xenogen-free microenvironment.
The Performance of Ice-free Cryopreserved Heart Valve Allografts in an Orthotopic Pulmonary Sheep Model
Transplantation of cryopreserved heart valves (allografts) is limited by immune responses, inflammation, subsequent structural deterioration and an expensive infrastructure. In previous studies we demonstrated that conventional frozen cryopreservation (FC) is accompanied by serious alterations of extracellular matrix (ECM) structures. As the main culprit of the observed damages ice crystal formation was identified. Objective of this study was the application principles of cryoprotection as observed in nature, occurring in animals or plants, for ice-free cryopreservation (IFC) of heart valves. Using IFC, valves were processed and stored above the glass transition temperature of the cryoprotectant formulation (-124 degrees C) at -80 degrees C to avoid any ice formation, tissue-glass cracking and preserving ECM. After implantation in the orthotopic pulmonary position in sheep, we demonstrate that IFC resulted in cell free matrices, while maintaining crucial ECM-components such as elastin and collagen, translating into superior hemodynamics. In contrast, we reveal that FC valves showed ECM damage that was not restored in vivo, and T-cell inflammation of the stroma with significant leaflet thickening. Compared to currently applied FC practice IFC also reduced infrastructural needs for preservation, storage and shipping. These results have important implications for clinical valve transplantation including the promise of better long-term function and lower costs.
Mapping the First Stages of Mesoderm Commitment During Differentiation of Human Embryonic Stem Cells
Our understanding of how mesodermal tissue is formed has been limited by the absence of specific and reliable markers of early mesoderm commitment. We report that mesoderm commitment from human embryonic stem cells (hESCs) is initiated by epithelial-to-mesenchymal transition (EMT) as shown by gene expression profiling and by reciprocal changes in expression of the cell surface proteins, EpCAM/CD326 and NCAM/CD56. Molecular and functional assays reveal that the earliest CD326-CD56+ cells, generated from hESCs in the presence of activin A, BMP4, VEGF, and FGF2, represent a multipotent mesoderm-committed progenitor population. CD326-CD56+ progenitors are unique in their ability to generate all mesodermal lineages including hematopoietic, endothelial, mesenchymal (bone, cartilage, fat, fibroblast), smooth muscle, and cardiomyocytes, while lacking the pluripotency of hESCs. CD326-CD56+ cells are the precursors of previously reported, more lineage-restricted mesodermal progenitors. These findings present a unique approach to study how germ layer specification is regulated and offer a promising target for tissue engineering.
