A CRISPR interference strategy for gene expression silencing in multiple myeloma cell lines.

BACKGROUND: Multiple myeloma (MM) is the second most common hematologic neoplasm which is characterized by proliferation and infiltration of plasmatic cells in the bone marrow. Currently, MM is considered incurable due to resistance to treatment. The CRISPR/Cas9 system has emerged as a powerful tool for understanding the role of different genetic alterations in the pathogenesis of hematologic malignancies in both cell lines and mouse models. Despite current advances of gene editing tools, the use of CRISPR/Cas9 technology for gene editing of MM have not so far been extended. In this work, we want to repress Rnd3 expression, an atypical Rho GTPase involved in several cellular processes, in MM cell lines using a CRISPR interference strategy. RESULTS: We have designed different guide RNAs and cloning them into a lentiviral plasmid, which contains all the machinery necessary for developing the CRISPR interference strategy. We co-transfected the HEK 293T cells with this lentiviral plasmid and 3rd generation lentiviral envelope and packaging plasmids to produce lentiviral particles. The lentiviral particles were used to transduce two different multiple myeloma cell lines, RPMI 8226 and JJN3, and downregulate Rnd3 expression. Additionally, the impact of Rnd3 expression absence was analyzed by a transcriptomic analysis consisting of 3' UTR RNA sequencing. The Rnd3 knock-down cells showed a different transcriptomic profile in comparison to control cells. CONCLUSIONS: We have developed a CRISPR interference strategy to generate stable Rnd3 knockdown MM cell lines by lentiviral transduction. We have evaluated this strategy in two MM cell lines, and we have demonstrated that Rnd3 silencing works both at transcriptional and protein level. Therefore, we propose CRISPR interference strategy as an alternative tool to silence gene expression in MM cell lines. Furthermore, Rnd3 silencing produces changes in the cellular transcriptomic profile.

Human dental pulp stem cells improve left ventricular function, induce angiogenesis, and reduce infarct size in rats with acute myocardial infarction.

Human dental pulp contains precursor cells termed dental pulp stem cells (DPSC) that show self-renewal and multilineage differentiation and also secrete multiple proangiogenic and antiapoptotic factors. To examine whether these cells could have therapeutic potential in the repair of myocardial infarction (MI), DPSC were infected with a retrovirus encoding the green fluorescent protein (GFP) and expanded ex vivo. Seven days after induction of myocardial infarction by coronary artery ligation, 1.5 x 10(6) GFP-DPSC were injected intramyocardially in nude rats. At 4 weeks, cell-treated animals showed an improvement in cardiac function, observed by percentage changes in anterior wall thickening left ventricular fractional area change, in parallel with a reduction in infarct size. No histologic evidence was seen of GFP+ endothelial cells, smooth muscle cells, or cardiac muscle cells within the infarct. However, angiogenesis was increased relative to control-treated animals. Taken together, these data suggest that DPSC could provide a novel alternative cell population for cardiac repair, at least in the setting of acute MI.

BCR-ABL induces the expression of Skp2 through the PI3K pathway to promote p27Kip1 degradation and proliferation of chronic myelogenous leukemia cells.

Chronic myelogenous leukemia (CML) is characterized by the expression of the BCR-ABL tyrosine kinase, which results in increased cell proliferation and inhibition of apoptosis. In this study, we show in both BCR-ABL cells (Mo7e-p210 and BaF/3-p210) and primary CML CD34+ cells that STI571 inhibition of BCR-ABL tyrosine kinase activity results in a G(1) cell cycle arrest mediated by the PI3K pathway. This arrest is associated with a nuclear accumulation of p27(Kip1) and down-regulation of cyclins D and E. As a result, there is a reduction of the cyclin E/Cdk2 kinase activity and of the retinoblastoma protein phosphorylation. By quantitative reverse transcription-PCR we show that BCR-ABL/PI3K regulates the expression of p27(Kip1) at the level of transcription. We further show that BCR-ABL also regulates p27(Kip1) protein levels by increasing its degradation by the proteasome. This degradation depends on the ubiquitinylation of p27(Kip1) by Skp2-containing SFC complexes: silencing the expression of Skp2 with a small interfering RNA results in the accumulation of p27(Kip1). We also demonstrate that BCR-ABL cells show transcriptional up-regulation of Skp2. Finally, expression of a p27(Kip1) mutant unable of being recognized by Skp2 results in inhibition of proliferation of BCR-ABL cells, indicating that the degradation of p27(Kip1) contributes to the pathogenesis of CML. In conclusion, these results suggest that BCR-ABL regulates cell cycle in CML cells at least in part by inducing proteasome-mediated degradation of the cell cycle inhibitor p27(Kip1) and provide a rationale for the use of inhibitors of the proteasome in patients with BCR-ABL leukemias.

IL1ß induces mesenchymal stem cells migration and leucocyte chemotaxis through NF-κB.

Mesenchymal stem cells are often transplanted into inflammatory environments where they are able to survive and modulate host immune responses through a poorly understood mechanism. In this paper we analyzed the responses of MSC to IL-1ß: a representative inflammatory mediator. Microarray analysis of MSC treated with IL-1ß revealed that this cytokine activateds a set of genes related to biological processes such as cell survival, cell migration, cell adhesion, chemokine production, induction of angiogenesis and modulation of the immune response. Further more detailed analysis by real-time PCR and functional assays revealed that IL-1ß mainly increaseds the production of chemokines such as CCL5, CCL20, CXCL1, CXCL3, CXCL5, CXCL6, CXCL10, CXCL11 and CX(3)CL1, interleukins IL-6, IL-8, IL23A, IL32, Toll-like receptors TLR2, TLR4, CLDN1, metalloproteins MMP1 and MMP3, growth factors CSF2 and TNF-α, together with adhesion molecules ICAM1 and ICAM4. Functional analysis of MSC proliferation, migration and adhesion to extracellular matrix components revealed that IL-1ß did not affect proliferation but also served to induce the secretion of trophic factors and adhesion to ECM components such as collagen and laminin. IL-1ß treatment enhanced the ability of MSC to recruit monocytes and granulocytes in vitro. Blockade of NF-κß transcription factor activation with IκB kinase beta (IKKß) shRNA impaired MSC migration, adhesion and leucocyte recruitment, induced by IL-1ß demonstrating that NF-κB pathway is an important downstream regulator of these responses. These findings are relevant to understanding the biological responses of MSC to inflammatory environments.

Cardiac transcription factors driven lineage-specification of adult stem cells.

Differentiation of human bone marrow mesenchymal stem cells (hBMSC) into the cardiac lineage has been assayed using different approaches such as coculture with cardiac or embryonic cells, treatment with factors, or by seeding cells in organotypic cultures. In most cases, differentiation was evaluated in terms of expression of cardiac-specific markers at protein or molecular level, electrophysiological properties, and formation of sarcomers in differentiated cells. As observed in embryonic stem cells and cardiac progenitors, differentiation of MSC towards the cardiac lineage was preceded by translocation of NKX2.5 and GATA4 transcription factors to the nucleus. Here, we induce differentiation of hBMSC towards the cardiac lineage using coculture with neonatal rat cardiomyocytes. Although important ultrastructural changes occurred during the course of differentiation, sarcomerogenesis was not fully achieved even after long periods of time. Nevertheless, we show that the main cardiac markers, NKX2.5 and GATA4, translocate to the nucleus in a process characteristic of cardiac specification.

Mesenchymal stem cells provide better results than hematopoietic precursors for the treatment of myocardial infarction.

OBJECTIVES: The purpose of this study was to compare the ability of human CD34(+) hematopoietic stem cells and bone marrow mesenchymal stem cells (MSC) to treat myocardial infarction (MI) in a model of permanent left descendent coronary artery (LDA) ligation in nude rats. BACKGROUND: Transplantation of human CD34(+) cells and MSC has been proved to be effective in treating MI, but no comparative studies have been performed to elucidate which treatment prevents left ventricular (LV) remodelling more efficiently. METHODS: Human bone marrow MSC or freshly isolated CD34(+) cells from umbilical cord blood were injected intramyocardially in infarcted nude rats. Cardiac function was analyzed by echocardiography. Ventricular remodelling was evaluated by tissue histology and electron microscopy, and neo-formed vessels were quantified by immunohistochemistry. Chronic local inflammatory infiltrates were evaluated in LV wall by hematoxylin-eosin staining. Apoptosis of infarcted tissue was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. RESULTS: Both cell types induced an improvement in LV cardiac function and increased tissue cell proliferation in myocardial tissue and neoangiogenesis. However, MSC were more effective for the reduction of infarct size and prevention of ventricular remodelling. Scar tissue was 17.48 +/- 1.29% in the CD34 group and 10.36 +/- 1.07% in the MSC group (p < 0.001 in MSC vs. CD34). Moreover, unlike MSC, CD34(+)-treated animals showed local inflammatory infiltrates in LV wall that persisted 4 weeks after transplantation. CONCLUSIONS: Mesenchymal stem cells might be more effective than CD34(+) cells for the healing of the infarct. This study contributes to elucidate the mechanisms by which these cell types operate in the course of MI treatment.

Cardiac differentiation is driven by NKX2.5 and GATA4 nuclear translocation in tissue-specific mesenchymal stem cells.

Myocardial infarction is a major public health problem that causes significant mortality despite recent advances in its prevention and treatment. Therefore, approaches based on adult stem cells represent a promising alternative to conventional therapies for this life-threatening condition. Mesenchymal stem cells (MSCs) are self-renewing pluripotent cells that have been isolated from multiple tissues and differentiate to various cell types. Here we have analyzed the capacity of MSCs from human bone marrow (BMSC), adipose tissue (ATSC), and dental pulp (DPSC) to differentiate to cells with a cardiac phenotype. Differentiation of MSCs was induced by long-term co-culture with neonatal rat cardiomyocytes (CMs). Shortly after the establishment of MSC-CM co-cultures, expression of connexin 43 and the cardiac-specific markers troponin I, beta-myosin heavy chain, atrial natriuretic peptide, and alpha-sarcomeric actinin was detected in BMSCs, ATSCs, and DPSCs. Expression of differentiation markers increased over time in the co-cultures, reaching the highest levels at 4 weeks. Translocation of the transcription factors NKX2.5 and GATA4 to the nucleus was observed in all three cultures of MSCs during the differentiation process; moreover, nuclear localization of NKX2.5 and GATA4 correlated with expression of alpha-sarcomeric actinin. These changes were accompanied by an increase in myofibril organization in the resulting CM-like cells as analyzed by electron microscopy. Thus, our results provide novel information regarding the differentiation of tissue-specific MSCs to cardiomyocytes and support the potential use of MSCs in cell-based cardiac therapies.