Differential regulation of caspase-2 in MPP⁺-induced apoptosis in primary cortical neurons.

Parkinson's disease (PD), among the most common neurodegenerative diseases worldwide for which there is no cure, is characterized as progressive dopaminergic neuron loss in the substantia nigra through an unknown mechanism. Administering 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) causes neuronal cell death and Parkinsonism in humans. Commonly used in animal models of PD, MPTP can metabolize to 1-methyl-4-phenylpyridinium (MPP(+)); however, the detailed mechanism through which MPP(+) causes neuronal cell death remains undetermined. Previous reports have indicated those knockout mice with Bcl-2 associated protein X (Bax) or caspase-2, two mitochondrial outer membrane permeabilization inducers, are resistant to MPTP administration, suggesting that mitochondria are involved in MPP(+)-triggered apoptosis. Our previous study showed that MPP(+)-triggered apoptosis can be distinguished from spontaneous apoptosis of primary cortical neurons. In the present study, we verified the involvement of mitochondria in MPP(+)-induced and spontaneous apoptosis in cortical neurons through confocal microscope analysis. We demonstrated that caspase-2 activation is specific to MPP(+)-induced apoptosis and occurs before Bax translocation to the mitochondria. Caspase-2 activation is one of the few early molecular events identified in PD models.

Endogenous KLF4 expression in human fetal endothelial cells allows for reprogramming to pluripotency with just OCT3/4 and SOX2--brief report.

OBJECTIVE: The introduction of 4 transcription factors-c-MYC, OCT3/4, SOX2, and KLF4--can reprogram somatic cells back to pluripotency. However, some of the factors used are oncogenic, making therapeutic application unfeasible. Although the use of adult stem cells expressing high endogenous levels of some of these factors allows for reprogramming with fewer exogenous genes, such cells are rare and may have accumulated genetic mutations. Our goal was to reprogram human somatic cells without oncogenic factors. We found that high endogenous expression of KLF4 in human umbilical vein endothelial cells (HUVECs) allows for generation of induced pluripotent stem cells (iPSCs) with just 2 nononcogenic factors, OCT3/4 and SOX2. METHODS AND RESULTS: HUVECs were infected with lentivirus containing OCT4 and SOX2 for generation of iPSCs. These 2-factor HUVEC iPSCs were morphologically similar to embryonic stem cells, express endogenous pluripotency markers postreprogramming, and can differentiate toward lineages of all 3 germ layers both in vitro and in vivo. CONCLUSIONS: iPSCs can be generated from HUVECs with only 2 nononcogenic factors. The use of fetal cells for reprogramming without oncogenic factors may provide an efficient in vitro model for human iPSC research, as well as a novel source for possible therapeutic use.

Brief report--human embryonic stem cell-derived mesenchymal progenitors possess strong immunosuppressive effects toward natural killer cells as well as T lymphocytes.

The derivation of mesenchymal progenitors from human embryonic stem cells (hESCs) has recently been reported. We studied the immune characteristics of these hESC-derived mesenchymal progenitors (EMPs) and their interactions with T lymphocytes and natural killer cells (NKs), two populations of lymphocytes with important roles in transplantation immunology. EMPs express a number of bone marrow mesenchymal stromal cell (BMMSC) markers, as well as the hESC marker SSEA-4. Immunologically, EMPs do not express HLA-DR or costimulatory molecules. On the other hand, HLA-G, a nonclassic MHC I protein involved in mediating maternal-fetal tolerance, can be found on the surface of EMPs, and its expression is increased after interferon-gamma stimulation. EMPs can suppress CD4(+) or CD8(+) lymphocyte proliferation, similar to BMMSCs. However, EMPs are more resistant to NK-mediated lysis than BMMSCs and can suppress the cytotoxic effects of activated NKs, as well as downregulating the NK-activating receptors NKp30 and NKp46. With their broad immunosuppressive properties, EMPs may represent a new potential cell source for therapeutic use.

Single-step purification of recombinant anthrax lethal factor from periplasm of Escherichia coli.

Lethal toxin (LT) that composed by protective antigen and lethal factor (LF) is the major virulence factor of Bacillus anthracis. The treatments of LT in animals could reproduce most manifestations of B. anthracis infections that greatly improves our knowledge in LT-mediated pathogenesis and facilitates anthrax-related researches without having to directly contact the hazardous bacterium B. anthracis. The recombinant protein of LF (rLF), however, still lacks a simple purification method. Herein, we developed single-step nickel affinity purification of rLF with yield up to 3mg/l. By fusion to the leader sequence of outer membrane protein OmpA, rLF could easily be purified from the periplasm of Escherichia coli. To investigate whether the rLT is functional in our system, both wild type rLF and the catalytic mutant rLF that contains a single amino acid substitution at zinc-binding site (LF(E687A)), were subjected to macrophage cytotoxicity analysis. Our data showed that the rLT is fully functional, while the LF(E687A) fail to induce cell death of tested macrophage cells. These findings suggested that the purification protocol herein is a user-friendly method that allows researchers to obtain the functional rLF by single-step purification.

Surface expression of HLA-G is involved in mediating immunomodulatory effects of placenta-derived multipotent cells (PDMCs) towards natural killer lymphocytes.

Interactions between maternal natural killer lymphocytes (NKs) and fetal tissues are important in mediating maternal-fetal tolerance. We therefore investigated the interactions of NKs to placenta-derived multipotent cells (PDMCs) isolated from the term human placenta. PDMCs have similar cell surface marker expression as bone marrow mesenchymal stem cells (BMMSCs) and additionally express human embryonic stem cell markers SSEA-4 and CD-9. Differentiation into the tri-mesodermal lineages of osteoblastic, adipocytic, and chondrogenic phenotypes can be readily achieved under the appropriate conditions. We found that PDMCs are more resistant to NK-mediated lysis than the major histocompatibility complex (MHC) class-I null target cell K562, and can suppress NK secretion of interferon-γ (IFN-γ). Moreover, as third-party cells, PDMCs suppressed the cytotoxic effects of cytokine-stimulated NKs on K562. Pretreatment of PDMCs with IFN-γ, a proinflammatory cytokine, surprisingly enhanced such immunosuppressive effects. Cell-cell contact between NKs and PDMCs is required for suppressive effects, which are partially mediated by slight upregulation of the NK inhibitory receptor killer inhibitory receptor and downregulation of the activating receptor NKp30. Moreover, enhancement of PDMC suppressive effects is also mediated by IFN-γ-induced surface expression of HLA-G--an immunomodulatory nonclassical MHC class I molecule--on PDMCs, as seen by partial reversibility with HLA-G neutralizing antibodies. With its broad immunosuppressive properties, PDMCs may represent a potential cell source for therapeutic use.

Multilineage differentiation and characterization of the human fetal osteoblastic 1.19 cell line: a possible in vitro model of human mesenchymal progenitors.

The in vitro study of human bone marrow mesenchymal stromal cells (BMMSCs) has largely depended on the use of primary cultures. Although these are excellent model systems, their scarcity, heterogeneity, and limited lifespan restrict their usefulness. This has led researchers to look for other sources of MSCs, and recently, such a population of progenitor/stem cells has been found in mesodermal tissues, including bone. We therefore hypothesized that a well-studied and commercially available clonal human osteoprogenitor cell line, the fetal osteoblastic 1.19 cell line (hFOB), may have multilineage differentiation potential. We found that undifferentiated hFOB cells possess similar cell surface markers as BMMSCs and also express the embryonic stem cell-related pluripotency gene, Oct-4, as well as the neural progenitor marker nestin. hFOB cells can also undergo multilineage differentiation into the mesodermal lineages of chondrogenic and adipocytic cell types in addition to its predetermined pathway, the mature osteoblast. Moreover, as with BMMSCs, under neural-inducing conditions, hFOB cells acquire a neural-like phenotype. This human cell line has been a widely used model of normal osteoblast differentiation. Our data suggest that hFOB cells may provide for researchers an easily available, homogeneous, and consistent in vitro model for study of human mesenchymal progenitor cells.