Therapeutic potential of human olfactory bulb neural stem cells for spinal cord injury in rats.

STUDY DESIGN: Adult human olfactory bulb neural stem cells (OBNSCs) were isolated from human patients undergoing craniotomy for tumor resection. They were genetically engineered to overexpresses green fluorescent protein (GFP) to help trace them following engraftment. Spinal cord injury (SCI) was induced in rats using standard laminectomy protocol, and GFP-OBNSC were engrafted into rat model of SCI at day 7 post injury. Three rat groups were used: (i) Control group, (ii) Sham group (injected with cerebrospinal fluid) and treated group (engrafted with OBNSCs). Tissues from different groups were collected weekly up to 2 months. The collected tissues were fixed in 4% paraformaldehyde, processed for paraffin sectioning, immunohistochemically stained for different neuronal and glial markers and examined with bright-field fluorescent microscopy. Restoration of sensory motor functions we assessed on a weekly bases using the BBB score. OBJECTIVES: To assess the therapeutic potential of OBNSCs-GFP and their ability to survive, proliferate, differentiate and to restore lost sensory motor functions following their engraftment in spinal cord injury (SCI). METHODS: GFP-OBNSC were engrafted into a rat model of SCI at day 7 post injury and were followed-up to 8 weeks using behavioral and histochemical methods. RESULTS: All transplanted animals exhibited successful engraftment. The survival rate was about 30% of initially transplanted cells. Twenty-seven percent of the engrafted cells differentiated along the NG2 and O4-positive oligodendrocyte lineage, 16% into MAP2 and ß-tubulin-positive neurons, and 56% into GFAP-positive astrocytes. CONCLUSION: GFP-OBNSCs had survived for >8 weeks after engraftment and were differentiated into neurons, astrocytes and oligodendrocytes, The engrafted cells were distributed throughout gray and white matter of the cord with no evidence of abnormal morphology or any mass formation indicative of tumorigenesis. However, the engrafted cells failed to restore lost sensory and motor functions as evident from behavioral analysis using the BBB score test.

A RA-dependent, tumour-growth suppressive transcription complex is the target of the PML-RARalpha and T18 oncoproteins.

PML and Tif1a are fused to RARA and Braf, respectively, resulting in the production of PML-RARalpha and Tif1alpha-B-Raf (T18) oncoproteins. Here we show that PML, Tif1alpha and RXRalpha/RARalpha function together in a transcription complex that is dependent on retinoic acid (RA). We found that PML acts as a ligand-dependent coactivator of RXRalpha/RARalpha. PML interacts with Tif1alpha and CBP. In Pml-/- cells, the RA-dependent induction of genes such as RARB2 and the ability of Tif1alpha and CBP to act as transcriptional coactivators on RA are impaired. We show that both PML and Tif1alpha are growth suppressors required for the growth-inhibitory activity of RA. T18, similar to PML-RARalpha, disrupts the RA-dependent activity of this complex in a dominant-negative manner resulting in a growth advantage. Our data define a new pathway for the control of cell growth and tumorigenesis, and provide a new model for the pathogenesis of acute promyelocytic leukaemia (APL).

Role of Bim in apoptosis induced in H460 lung tumor cells by the spindle poison Combretastatin-A4.

The BH3-only Bcl-2 subfamily member Bim is a well known apoptosis promoting protein. However, the mechanisms upstream of mitochondrion membrane permeability by which Bim is involved in apoptosis have been poorly investigated, particularly in response to agents capable of interfering with the cytoskeleton architecture and arresting cells in mitosis. Based on the observation that Bim is sequestered on the microtubule-array by interaction with the light chain of dynein, we have investigated upon depolymerisation, whether Bim could be involved in the commitment of apoptosis. With this purpose H460 Non Small Lung Cancer Cells (NSLC) were treated with the microtubule damaging agent combretastatin-A4 (CA-4) (7.5 nM; 8-48 h), and various parameters were investigated. Upon treatment, cells arrested in mitosis and died through a caspase-3-dependent mitotic catastrophe. Transient knock down of Bim drastically reduced apoptosis, indicating that this protein was involved in cell death as induced by microtubules disorganisation. In response to increasing conditions of microtubules depolymerisation, we found that the protein level of Bim was strongly upregulated in a time-dependent manner at transcriptional level. Furthermore, Bim was released from microtubule-associated components. Bim was translocated to mitochondria, even in a condition of protein synthesis inhibition, where it showed a markedly increased interaction with Bcl-2. In turn, the fraction of Bax bound to Bcl-2 decreases in response to treatment, thereby indicating that Bim possibly promotes Bax release from the pro-survival protein Bcl-2. Overall, we demonstrated that Bim is required for the CA-4-induced cell death in the H460 lung cancer cell line via activation of the mitochondrial signalling pathway. Defining the contribution of Bim to the mechanism of apoptosis may offer some different clues in view of developing new strategies for chemotherapy with CA-4, underlining the relevance of the cytoskeleton integrity in the apoptotic response.

Activation-induced ubiquitination of the T cell antigen receptor.

The zeta subunit of the T cell antigen receptor (TCR) exists primarily as a disulfide-linked homodimer. This receptor subunit is important in TCR-mediated signal transduction and is a substrate for a TCR-activated protein tyrosine kinase. The zeta chain was found to undergo ubiquitination in response to receptor engagement. This posttranslational modification occurred in normal T cells and tumor lines. Both nonphosphorylated and phosphorylated zeta molecules were modified, and at least one other TCR subunit, CD3 delta, was also ubiquitinated after activation of the receptor. These findings suggest an expanded role for ubiquitination in transmembrane receptor function.

Xeno-free trans-differentiation of adipose tissue-derived mesenchymal stem cells into glial and neuronal cells.

Mesenchymal stem cells (MSCs) are undifferentiated cells that have the ability of self-renewal and trans-differentiation into other cell types. They hold out hope for finding a cure for many diseases. Nevertheless, there are still some obstacles that limit their clinical transplantation. One of these obstacles are the xenogeneic substances added in either proliferation or differentiation media with subsequent immunogenic and infectious transmission problems. In this study, we aimed to replace fetal bovine serum (FBS), the main nutrient source for MSC proliferation with xeno-free blood derivatives. We tested the effect of human activated pure platelet-rich plasma (P-PRP) and advanced platelet-rich fibrin (A-PRF) on the proliferation of human adipose derived-MSCs (AD-MSCs) at different concentrations. For the induction of MSC neural differentiation, we used human cerebrospinal fluid (CSF) at different concentrations in combination with P-PRP to effect xeno-free/species-specific neuronal/glial differentiation and we found that media with 10% CSF and 10% PRP promoted glial differentiation, while media with only 10% PRP induced a neuron-like phenotype.

Potential of Stem Cell-Based Therapy for Ischemic Stroke.

Ischemic stroke is one of the major health problems worldwide. The only FDA approved anti-thrombotic drug for acute ischemic stroke is the tissue plasminogen activator. Several studies have been devoted to assessing the therapeutic potential of different types of stem cells such as neural stem cells (NSCs), mesenchymal stem cells, embryonic stem cells, and human induced pluripotent stem cell-derived NSCs as treatments for ischemic stroke. The results of these studies are intriguing but many of them have presented conflicting results. Additionally, the mechanism(s) by which engrafted stem/progenitor cells exert their actions are to a large extent unknown. In this review, we will provide a synopsis of different preclinical and clinical studies related to the use of stem cell-based stroke therapy, and explore possible beneficial/detrimental outcomes associated with the use of different types of stem cells. Due to limited/short time window implemented in most of the recorded clinical trials about the use of stem cells as potential therapeutic intervention for stroke, further clinical trials evaluating the efficacy of the intervention in a longer time window after cellular engraftments are still needed.

Identification of a family of human F-box proteins.

F-box proteins are an expanding family of eukaryotic proteins characterized by an approximately 40 aminoacid motif, the F box (so named because cyclin F was one of the first proteins in which this motif was identified) [1]. Some F-box proteins have been shown to be critical for the controlled degradation of cellular regulatory proteins [2] [3]. In fact, F-box proteins are one of the four subunits of ubiquitin protein ligases called SCFs. The other three subunits are the Skp1 protein; one of the cullin proteins (Cul1 in metazoans and Cdc53 or Cul A in the yeast Saccharomyces cerevisiae); and the recently identified Roc1 protein (also called Rbx1 or Hrt1). SCF ligases bring ubiquitin conjugating enzymes (either Ubc3 or Ubc4) to substrates that are specifically recruited by the different F-box proteins. The need for high substrate specificity and the large number of known F-box proteins in yeast and worms [2] [4] suggest the existence of a large family of mammalian F-box proteins. Using Skp1 as a bait in a yeast two-hybrid screen and by searching DNA databases, we identified a family of 26 human F-box proteins, 25 of which were novel. Some of these proteins contained WD-40 domains or leucine-rich repeats; others contained either different protein-protein interaction modules or no recognizable motifs. We have named the F-box proteins that contain WD-40 domains Fbws, those containing leucine-rich repeats, Fbls, and the remaining ones Fbxs. We have further characterized representative members of these three classes of F-box proteins.

Human T cell leukemia virus type 1 Tax associates with a molecular chaperone complex containing hTid-1 and Hsp70.

Tax, an oncogenic viral protein encoded by human T cell leukemia virus type 1 (HTLV-1), induces cellular transformation of T lymphocytes by modulating a variety of cellular gene expressions [1]. Identifying cellular partners that interact with Tax constitutes the first step toward elucidating the molecular basis of Tax-induced transformation. Here, we report a novel Tax-interacting protein, hTid-1. hTid-1, a human homolog of the Drosophila tumor suppressor protein Tid56, was initially characterized based on its interaction with the HPV-16 E7 oncoprotein [2]. hTid-1 and Tid56 are members of the DnaJ family [2,3], which contains a highly conserved signature J domain that regulates the activities of heat shock protein 70 (Hsp70) by serving as cochaperone [4-6]. In this context, the molecular chaperone complex is involved in cellular signaling pathways linked to apoptosis, protein folding, and membrane translocation and in modulation of the activities of tumor suppressor proteins, including retinoblastoma, p53, and WT1[7-12]. We find that expression of hTid-1 inhibits the transformation phenotype of two human lung adenocarcinoma cell lines. We show that Tax interacts with hTid-1 via a central cysteine-rich domain of hTid-1 while a signature J domain of hTid-1 mediates its binding to Hsp70 in HEK cells. Importantly, Tax associates with the molecular chaperone complex containing both hTid-1 and Hsp70 and alters the cellular localization of hTid-1 and Hsp70. In the absence of Tax, expression of the hTid-1/Hsp70 molecular complex is targeted to perinuclear mitochondrial clusters. In the presence of Tax, hTid-1 and its associated Hsp70 are sequestered within a cytoplasmic "hot spot" structure, a subcellular distribution that is characteristic of Tax in HEK cells.

Critical role played by cyclin D3 in the MyoD-mediated arrest of cell cycle during myoblast differentiation.

During the terminal differentiation of skeletal myoblasts, the activities of myogenic factors regulate not only tissue-specific gene expressions but also the exit from the cell cycle. The induction of cell cycle inhibitors such as p21 and pRb has been shown to play a prominent role in the growth arrest of differentiating myoblasts. Here we report that, at the onset of differentiation, activation by MyoD of the Rb, p21, and cyclin D3 genes occurs in the absence of new protein synthesis and with the requirement of the p300 transcriptional coactivator. In differentiated myocytes, cyclin D3 also becomes stabilized and is found nearly totally complexed with unphosphorylated pRb. The detection of complexes containing cyclin D3, cdk4, p21, and PCNA suggests that cdk4, along with PCNA, may get sequestered into high-order structures held together by pRb and cyclin D3. Cyclin D3 up-regulation and stabilization is inhibited by adenovirus E1A, and this correlates with the ability of E1A to promote pRb phosphorylation; conversely, the overexpression of cyclin D3 in differentiated myotubes counteracts the E1A-mediated reactivation of DNA synthesis. These results indicate that cyclin D3 critically contributes to the irreversible exit of differentiating myoblasts from the cell cycle.

Genetically unmatched human iPSC and ESC exhibit equivalent gene expression and neuronal differentiation potential.

The potential uniformity between differentiation and therapeutic potential of human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) remains debatable. We studied the gene expression profiles, pathways analysis and the ability to differentiated into neural progenitor cells (NPCs) and motor neurons (MNs) of genetically unmatched integration-free hiPSC versus hESC to highlight possible differences/similarities between them at the molecular level. We also provided the functional information of the neurons derived from the different hESCs and hiPSCs lines using the Neural Muscular Junction (NMJ) Assay. The hiPSC line was generated by transfecting human epidermal fibroblasts (HEF) with episomal DNAs expressing Oct4, Sox2, Klf4, Nanog, L-Myc and shRNA against p53. For the hESCs line, we used the NIH-approved H9 cell line. Using unsupervised clustering both hESCs and hiPSCs were clustered together implying homogeneous genetic states. The genetic profiles of hiPSCs and hESCs were clearly similar but not identical. Collectively, our data indicate close molecular similarities between genetically unmatched hESCs and hiPS in term of gene expression, and signaling pathways. Moreover, both cell types exhibited similar cholinergic motor neurons differentiation potential with marked ability of the differentiated hESCs and hiPSCs-derived MNs to induce contraction of myotubes after 4 days of co-culture.

MyoD induces retinoblastoma gene expression during myogenic differentiation.

In skeletal muscle cells permanent withdrawal from the cell cycle is a prerequisite for terminal differentiation. The muscle-specific transcription factor MyoD can activate downstream muscle structural genes and myogenic conversion in many different cell types. It has been demonstrated that the product of the retinoblastoma susceptibility gene, with its growth-suppressive activity, is involved in the myogenic function of MyoD (Caruso et al., 1993; Gu et al., 1993). The present study characterises the modulation of retinoblastoma (Rb1) mRNA levels during myogenic differentiation of the murine C2 cell line and provides evidence that the muscle-specific regulatory factor MyoD enhances Rb1 gene transcription. We demonstrate that MyoD mediates the transactivation of a CAT construct whose expression is driven by the human Rb1 gene promoter, and that this is not a consequence of direct binding of MyoD to an E-box DNA sequence motif present in the Rb1 promoter sequences. In addition we have tested the capability of several MyoD mutant proteins of inducing the Rb1 promoter CAT construct. Our results indicate that the MyoD function required for induction of Rb1 promoter activity is distinct from its myogenic function.

Down-regulation of cyclin B1 gene transcription in terminally differentiated skeletal muscle cells is associated with loss of functional CCAAT-binding NF-Y complex.

The observation that cyclin B1 protein and mRNAs are down-regulated in terminally differentiated (TD) C2C12 cells, suggested us to investigate the transcriptional regulation of the cyclin B1 gene in these cells. Transfections of cyclin B1 promoter constructs indicate that two CCAAT boxes support cyclin B1 promoter activity in proliferating cells. EMSAs demonstrate that both CCAAT boxes are recognized by the trimeric NF-Y complex in proliferating but not in TD cells. Transfecting a dominant-negative mutant of NF-YA we provide evidence that NF-Y is required for maximal promoter activity. Addition of recombinant NF-YA to TD C2C12 nuclear extracts restores binding activity in vitro, thus indicating that the loss of NF-YA in TD cells is responsible for the lack of the NF-Y binding to the CCAAT boxes. Consistent with this, we found that the NF-YA protein is absent in TD C2C12 cells. In conclusion, our data demonstrate that NF-Y is required for cyclin B1 promoter activity. We also demonstrate that cyclin B1 expression is regulated at the transcriptional level in TD C2C12 cells and that the switch-off of cyclin B1 promoter activity in differentiated cells depends upon the loss of a functional NF-Y complex. In particular the loss of NF-YA protein is most likely responsible for its inactivation.

Monoclonal antibodies as a tool for structure-function studies of the MDR1-P-glycoprotein.

P-glycoprotein is considered one of the most important member of the rapidly growing superfamily of integral proteins known as the ATP-binding cassette (ABC) which in human also include several other multidrug resistance membrane proteins (i.e., MRP), the product of the cystic fibrosis gene, the TAP-1/TAP2 peptide transporters encoded by the major histocompatibility complex genes and the gene encoding for breast cancer resistance protein (BCRP) also known as MXR1 (mitoxantrone resistance protein). Many monoclonal antibodies (MAbs) reacting with distinct P-glycoprotein domains have been isolated and used to study the molecular organization and cellular functions of this ABC protein. MAbs have been used for multidrug resistance (mdr) gene cloning, delineation of the secondary and tertiary structure of P-glycoprotein and molecular analysis of the mechanisms involved in substrate recognition and transport. The immunodetection of the distinct products of the mdr gene family in normal and malignant cells and tissues has greatly contributed to the understanding of the physiological role of P-glycoprotein and its possible involvement in the refractory of tumors to chemotherapy. The present article deals with the immunological methods used for the structure-function studies of the P-glycoprotein. After introducing the basic structural features of this ABC transporter, the antibody based-approach is discussed with aiming to furnishing methodological perspectives for further investigations of the physiological role of P-glycoprotein and the multidrug resistance phenomenon.

High frequency production of hybridomas secreting antibodies to cell antigens.

The efficiency of various immunization protocols for the production of hybridomas secreting immunoglobulins specific to cell antigens was evaluated in 15 different fusion experiments. Some of these experiments were performed with splenic B-lymphocytes from mice at different stages of immunization. This approach allowed a dynamic analysis of immunocompetent splenic B-lymphocyte production during the immunization cycle.

Antipeptide antibodies: do they distinguish HLA-alloantigens?

Three immune sera, raised in rabbits against synthetic peptides corresponding in sequence to predetermined regions of the HLA-DQ histocompatibility antigens, were tested for their ability to recognize phenotypically distinct human lymphoblastoid cell lines. The immune sera readily recognize the immunogen. When tested on the cells, they react poorly but seem to exhibit a certain degree of specificity. The possibilities in developing true selective reagents for HLA-alloantigens are considered and discussed.

Partial characterization of anti-HLA class II antibodies isolated by aid of sepharose-peptide immunoadsorbents.

Synthetic peptides selected from HLA-DQ and HLA-DP glycoproteins were coupled to Sepharose, and used for the isolation of anti-HLA Class II antibodies from the immune sera of rabbits immunized with human lymphoblastoid cells expressing Class II antigens. Antibodies from early and late bleedings displayed remarkable differences in affinity for peptides and for soluable membrane proteins: these differences might be due to an early immune response directed preferentially against surface linear determinants, and to a late response to assembled (discontinuous) sites. The possibility that such antibodies might be used for the identification of amino acid stretches involved in the formation of the same assembled determinant is considered.

Susceptibility of multidrug-resistant human T-lymphoblastoid CEM cell line to cell-mediated cytolysis.

The using of multidrug-resistant (MDR) cell variants represents one of the major obstacles to an effective cancer therapy based on the administration of cytotoxic compounds. In the present article we describe experimental procedures able to eradicate, in vitro, by using specific immunological reagent, MDR tumor cells. In an allogeneic cell system, natural killer (NK) and lymphokine activated killer (LAK) cells result effective against MDR variants of the human T-lymphoblastoid CEM cell line. Surprisingly effector cells discriminate in their lytic capacity target cells possessing a MDR phenotype. A direct relationship between the degree of relative resistance shown by target cells and cytotoxic level exerted by peripheral lymphocytes stimulated and non by IL-2 was observed. The preincubation of MDR cell variants with a monoclonal antibody (MoAb57) specific for an extramembranal epitope of P-glycoprotein induced, in presence of effector cells, a strong antibody-dependent cell-mediated cytolysis (ADCC). This phenomenon was observed only in MDR variants over-expressing in concomitance with drug-resistance high level of P-glycoprotein. In identical experimental conditions, drug-sensitive parental cells does not show valuable ADCC.

Evidence for GTP-binding protein involvement in the tyrosine phosphorylation of the T cell receptor zeta chain.

The zeta subunit of the T cell receptor (TCR) is a prominent substrate for a TCR-activated tyrosine kinase. Tyrosine phosphorylation of the zeta subunit in response to antibody-mediated receptor cross-linking was synergized in permeabilized T cells by either of two non-hydrolyzable GTP analogues, guanosine 5'-[gamma-thio]triphosphate (GTP gamma S) or guanosine 5'-[beta, gamma-imido]triphosphate Gpp(NH)p. ATP analogues did not significantly affect antibody-induced tyrosine phosphorylation. Unlike the GTP analogues, the GDP analogue guanosine 5'-[beta-thio]diphosphate (GDP beta S) did not enhance phosphorylation of zeta. The effect induced by the GTP analogues required TCR occupancy and was independent of protein kinase C. Taken together these observations implicate a GTP-binding protein in the modulation of TCR-induced tyrosine phosphorylation.

Activation-dependent ubiquitination of a T cell antigen receptor subunit on multiple intracellular lysines.

The T cell antigen receptor zeta chain and other T cell antigen receptor components are ubiquitinated on receptor occupancy. A systematic mutagenesis of the zeta subunit was undertaken to determine the sites of ubiquitination. Ubiquitination was found to occur in the cytoplasmic domain of zeta with multiple lysines serving as sites for mono- and polyubiquitination. The mutation of all potential sites of ubiquitination did not inhibit receptor tyrosine phosphorylation or the ubiquitination of other T cell antigen receptor subunits. Lysines introduced into nonnative positions in the zeta molecule were also able to serve as sites for ubiquitination. These findings demonstrate that once a T cell antigen receptor is targeted for ubiquitination, there is little specificity with regard to the lysine residues that are modified.