Yali Zhao

MSCs: Biological characteristics, clinical applications and their outstanding concerns.

Mesenchymal stem cells (MSCs) are multi-potent adult stem cells harboring multi-lineage differentiation potential and immunosuppressive properties that make MSCs an ideal candidate cell type for immunomodulation and regenerative medicine. Currently, MSC-related researches and clinical trials have evoked exciting promise in a variety of disorders and tissue regeneration. However, it must be recognized that several critical potential problems have also emerged from current clinical trials, for example: (1) the indefinite association between the phenotypic characteristics and the biological functions of MSCs; (2) the lack of clinical data to support the long-term safety of MSCs; (3) the need for further clarification of multiple mechanisms of MSC transplant actions in vivo; and (4) the lack of comparability of MSC transplant efficacy. Therefore, MSC-based therapies could not yet be considered a routine treatment in the clinic. Based on these, we proposed that large-scale and multi-center clinical trials of MSC-based therapies should be initiated under strict supervision. These interventions might help to establish a new clinical paradigm to turn MSC transplantation into a routine therapy for at least some diseases in the near future.

The evaluation of catechins that contain a galloyl moiety as potential HIV-1 integrase inhibitors

Four catechins with the galloyl moiety, including catechin gallate (CG), epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), and epicatechin gallate (ECG), were found to inhibit HIV-1 integrase effectively as determined by our ELISA method. In our docking study, it is proposed that when the HIV-1 integrase does not combine with virus DNA, the four catechins may bind to Tyr143 and Gln148, thus altering the flexibility of the loop (Gly140-Gly149), which could lead to an inhibition of HIV-1 integrase activity. In addition, after combining HIV-1 integrase with virus DNA, the four catechins may bind between the integrase and virus DNA, consequently, disrupt this interaction. Thus, the four catechins may reduce the activity of HIV-1 integrase by disrupting its interaction with virus DNA. The four catechins have a highly cooperative inhibitory effect (IC₅₀=0.1 μmol/L). Our study suggests that catechins with the galloyl moiety could be a novel and effective class of HIV-1 integrase inhibitors.

Id2 promotes the invasive growth of MCF-7 and SKOV-3 cells by a novel mechanism independent of dimerization to basic helix-loop-helix factors

BackgroundInhibitor of differentiation 2 (Id2) is a critical factor for cell proliferation and differentiation in normal vertebrate development. Most of the biological function of Id2 has been ascribed to its helix-loop-helix motif. Overexpression of Id2 is frequently observed in various human tumors, but its role for invasion potential in tumor cells is dispute. We aimed to reveal the role of Id2 in invasion potential in poorly invasive and estrogen receptor α (ERα)-positive MCF-7 and SKOV-3 cancer cells.MethodsMCF-7 and SKOV-3 cells were stably transfected with the wild-type, degradation-resistant full-length or helix-loop-helix (HLH)-deleted Id2, respectively. Protein levels of Id2 and its mutants and E-cadherin were determined by western blot analysis and mRNA levels of Id2 and its mutants were determined by RT-PCR. The effects of Id2 and its mutants on cell proliferation were determined by [3H]-thymidine incorporation assay and the 3- [4, 5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) dye method. The in vitro invasion potential of cells was evaluated by Transwell assay. Cell motility was assessed by scratch wound assay. The promoter activity of E-cadherin was determined by cotransfection and luciferase assays.ResultsEctopic transfection of the wild-type Id2 markedly increased the protein and mRNA expression of Id2 in MCF-7 and SKOV-3 cells; the protein level but not mRNA level was further increased by transfection with the degradation-resistant Id2 form. The ectopic expression of Id2 or its mutants did not alter proliferation of either MCF-7 or SKOV-3 cells. Transfection of the wild-type Id2 significantly induced the invasion potential and migratory capacity of cells, which was further augmented by transfection with the degradation-resistant full-length or HLH-deleted Id2. E-cadherin protein expression and transactivation of the proximal E-cadherin promoter were markedly suppressed by the degradation-resistant full-length or HLH-deleted Id2 but not wild-type Id2. Ectopic expression of E-cadherin in MCF-7 and SKOV-3 cells only partially blunted the invasion potential induced by the degradation-resistant HLH-deleted Id2.ConclusionOverexpression of Id2 in ERα-positive epithelial tumor cells indeed increases the cells invasive potential through a novel mechanism independent of dimerization to basic helix-loop-helix factors. E-cadherin contributes only in part to Id2-induced cell invasion when Id2 is accumulated to a higher level in some specific cell types.

Catechins containing a galloyl moiety as potential anti-HIV-1 compounds.

Catechins containing galloyl moieties are important natural antioxidant compounds. In this paper, we review the multiple mechanisms whereby catechins containing a galloyl moiety can target key proteins to inhibit sexual transmission of HIV-1, as well as HIV-1 fusion, HIV-1 reverse transcriptase, HIV-1 integrase and HIV-1 protease. Furthermore, catechins with a galloyl moiety can mediate host cell factors such as nitric oxide synthase, nuclear factor-κB and casein kinase II to inhibit HIV-1 infection. The most significant inhibitory effect is blocking gp120 binding to isolated human CD4+ T cells. The multiple mechanisms underlying the anti-HIV activity of galloyl-containing catechins predict that these catechins could be used as alternative therapies in the treatment of HIV infection.

Can controlled cellular reprogramming be achieved using microRNAs

Since a technique was reported for generating induced pluripotent stem cells (iPSCs), various groups worldwide have reprogrammed human and mouse somatic cells into iPSCs using a range of techniques and pluripotency genes. Progress in iPSC research has opened up a novel avenue in autologous regenerative medicine, whereby patient-specific pluripotent cells could potentially be derived from adult somatic cells. However, several limitations currently prohibit their use in clinical settings, including the viral DNA delivery system and the exogenous overexpression of pluripotency genes. New strategies are therefore needed to ensure the safe and efficient production of iPSCs, and to guide their differentiation into the desired lineages required to repair damaged tissue and treat disease. Here, we present an overview of recent research into cellular reprogramming. We focus on the feasibility of microRNA-based strategies for reprogramming somatic cells into pluripotent stem cells, thus obviating the need to introduce viruses or DNA into donor cells, and therefore ameliorating the risks associated with reprogramming techniques. In light of the critical roles of microRNAs in maintaining the pluripotent state and in regulating cell-lineage specification and epigenetic modifications of chromatin, we also discuss the potential role of microRNAs as candidates for controlled cellular reprogramming and induction of cell fate conversion beyond lineages without reversion to a pluripotent state. Further research into the microRNAs involved in iPSC reprogramming and their potential roles in controlled cellular reprogramming will add another dimension to our understanding of the molecular mechanisms involved in cellular reprogramming.

Keratin 18 attenuates estrogen receptor α-mediated signaling by sequestering LRP16 in cytoplasm

BackgroundOncogenesis in breast cancer is often associated with excess estrogen receptor α(ERα) activation and overexpression of its coactivators. LRP16 is both an ERα target gene and an ERα coactivator, and plays a crucial role in ERα activation and proliferation of MCF-7 breast cancer cells. However, the regulation of the functional availability of this coactivator protein is not yet clear.ResultsYeast two-hybrid screening, GST pulldown and coimmunoprecipitation (CoIP) identified the cytoplasmic intermediate filament protein keratin 18 (K18) as a novel LRP16-interacting protein. Fluorescence analysis revealed that GFP-tagged LRP16 was primarily localized in the nuclei of mock-transfected MCF-7 cells but was predominantly present in the cytoplasm of K18-transfected cells. Immunoblotting analysis demonstrated that the amount of cytoplasmic LRP16 was markedly increased in cells overexpressing K18 whereas nuclear levels were depressed. Conversely, knockdown of endogenous K18 expression in MCF-7 cells significantly decreased the cytoplasmic levels of LRP16 and increased levels in the nucleus. CoIP failed to detect any interaction between K18 and ERα, but ectopic expression of K18 in MCF-7 cells significantly blunted the association of LRP16 with ERα, attenuated ERα-activated reporter gene activity, and decreased estrogen-stimulated target gene expression by inhibiting ERα recruitment to DNA. Furthermore, BrdU incorporation assays revealed that K18 overexpression blunted the estrogen-stimulated increase of S-phase entry of MCF-7 cells. By contrast, knockdown of K18 in MCF-7 cells significantly increased ERα-mediated signaling and promoted cell cycle progression.ConclusionsK18 can effectively associate with and sequester LRP16 in the cytoplasm, thus attenuating the final output of ERα-mediated signaling and estrogen-stimulated cell cycle progression of MCF-7 breast cancer cells. Loss of K18 increases the functional availability of LRP16 to ERα and promotes the proliferation of ERα-positive breast tumor cells. K18 plays an important functional role in regulating the ERα signaling pathway.