Chung-Liang Chien

Highly efficient cellular labeling of mesoporous nanoparticles in human mesenchymal stem cells: implication for stem cell tracking

Tracking the distribution of stem cells is crucial to their therapeutic use. However, the usage of current vectors in cellular labeling is restricted by their low internalizing efficiency. Here, we reported a cellular labeling approach with a novel vector composed of mesoporous silica nanoparticles (MSNs) conjugated with fluorescein isothiocyanate in human bone marrow mesenchymal stem cells and 3T3‐L1 cells, and the mechanism about fluorescein isothiocyanate‐conjugated MSNs (FITC‐MSNs) internalization was studied. FITC‐MSNs were efficiently internalized into mesenchymal stem cells and 3T3‐L1 cells even in short‐term incubation. The process displayed a time‐ and concentration‐dependent manner and was dependent on clathrin‐mediated endocytosis. In addition, clathrin‐dependent endocytosis seemed to play a decisive role on more internalization and longer stay of FITC‐MSNs in mesenchymal stem cells than in 3T3‐L1 cells. The internalization of FITC‐MSNs did not affect the cell viability, proliferation, immunophenotype, and differentiation potential of mesenchymal stem cells, and 3T3‐L1 cells. Finally, FITC‐MSNs could escape from endolysosomal vesicles and were retained the architectonic integrity after internalization. We conclude that the advantages of biocompatibility, durability, and higher efficiency in internalization suit MSNs to be a better vector for stem cell tracking than others currently used.

Human Pompe disease induced pluripotent stem cells for pathogenesis modeling, drug testing and disease marker identification

Pompe disease is caused by autosomal recessive mutations in the acid alpha-glucosidase (GAA) gene, which encodes GAA. Although enzyme replacement therapy has recently improved patient survival greatly, the results in skeletal muscles and for advanced disease are still not satisfactory. Here, we report the derivation of Pompe disease-induced pluripotent stem cells (PomD-iPSCs) from two patients with different GAA mutations and their potential for pathogenesis modeling, drug testing and disease marker identification. PomD-iPSCs maintained pluripotent features and had low GAA activity and high glycogen content. Cardiomyocyte-like cells (CMLCs) differentiated from PomD-iPSCs recapitulated the hallmark Pompe disease pathophysiological phenotypes, including high levels of glycogen and multiple ultrastructural aberrances. Drug rescue assessment showed that exposure of PomD-iPSC-derived CMLCs to recombinant human GAA reversed the major pathologic phenotypes. Furthermore, l-carnitine treatment reduced defective cellular respiration in the diseased cells. By comparative transcriptome analysis, we identified glycogen metabolism, lysosome and mitochondria-related marker genes whose expression robustly correlated with the therapeutic effect of drug treatment in PomD-iPSC-derived CMLCs. Collectively, these results demonstrate that PomD-iPSCs are a promising in vitro disease model for the development of novel therapeutic strategies for Pompe disease.

Activation of the transient receptor potential M2 channel and poly(ADP-ribose) polymerase is involved in oxidative stress-induced cardiomyocyte death

Overproduction of reactive oxygen species is one of the major causes of cell death in ischemic–reperfusion (I/R) injury. In I/R animal models, electron microscopy (EM) has shown mixed apoptotic and necrotic characteristics in the same cardiomyocyte. The present study shows that H2O2 activates both apoptotic and necrotic machineries in the same myocyte and that the ultrastructure seen using EM is very similar to that in I/R animal studies. The apoptotic component is caused by the activation of clotrimazole-sensitive, NAD+/ADP ribose/poly(ADP-ribose) polymerase (PARP)-dependent transient receptor potential M2 (TRPM2) channels, which induces mitochondrial [Na+]m (and [Ca2+]m) overload, resulting in mitochondrial membrane disruption, cytochrome c release, and caspase 3-dependent chromatin condensation/fragmentation. The necrotic component is caspase 3-independent and is caused by PARP-induced [ATP]i/NAD+ depletion, resulting in membrane permeabilization. Inhibition of either TRPM2 or PARP activity only partially inhibits cell death, while inhibition of both completely prevents the ultrastructural changes and myocyte death.

zVAD-induced autophagic cell death requires c-Src-dependent ERK and JNK activation and reactive oxygen species generation

The treatment of L929 fibrosarcoma cells with zVAD has been shown to induce necroptosis. However, whether autophagy is involved or not in this event remains controversial. In this study, we re-examined the role of autophagy in zVAD-induced cell death in L929 cells and further elucidated the signaling pathways triggered by caspase inhibition and contributing to autophagic death. First, we found that zVAD can stimulate LC3-II formation, autophagosome and autolysosome formation, and ROS accumulation. Antioxidants, beclin 1 or Atg5 silencing, and class III PtdIns3K inhibitors all effectively blocked ROS production and cell death, suggesting ROS accumulation downstream of autophagy contributes to cell necrosis. zVAD also stimulated PARP activation, and the PARP inhibitor DPQ can reduce zVAD-induced cell death, but did not affect ROS production, suggesting the increased ROS leads to PARP activation and cell death. Notably, our data also indicated the involvement of Src-dependent JNK and ERK in zVAD-induced ROS production and autophagic death. We found caspase 8 is associated with c-Src at the resting state, and upon zVAD treatment this association was decreased and accompanied by c-Src activation. In conclusion, we confirm the autophagic death in zVAD-treated L929 cells, and define a new molecular pathway in which Src-dependent ERK and JNK activation can link a signal from caspase inhibition to autophagy, which in turn induce ROS production and PARP activation, eventually leading to necroptosis. Thus, in addition to initiating proteolytic activity for cell apoptosis, inactivated caspase 8 also functions as a signaling molecule for autophagic death.

Transplantation of Reprogrammed Embryonic Stem Cells Improves Visual Function in a Mouse Model for Retinitis Pigmentosa

Background. To study whether C57BL/6J-Tyrc−2j/J (C2J) mouse embryonic stem (ES) cells can differentiate into retinal pigment epithelial (RPE) cells in vitro and then restore retinal function in a model for retinitis pigmentosa: Rpe65rd12/Rpe65rd12 C57BL6 mice. Methods. Yellow fluorescent protein (YFP)-labeled C2J ES cells were induced to differentiate into RPE-like structures on PA6 feeders. RPE-specific markers are expressed from differentiated cells in vitro. After differentiation, ES cell-derived RPE-like cells were transplanted into the subretinal space of postnatal day 5 Rpe65rd12/Rpe65rd12 mice. Live imaging of YFP-labeled C2J ES cells demonstrated survival of the graft. Electroretinograms (ERGs) were performed on transplanted mice to evaluate the functional outcome of transplantation. Results. RPE-like cells derived from ES cells sequentially express multiple RPE-specific markers. After transplantation, YFP-labeled cells can be tracked with live imaging for as long as 7 months. Although more than half of the mice were complicated with retinal detachments or tumor development, one fourth of the mice showed increased electroretinogram responses in the transplanted eyes. Rpe65rd12/Rpe65rd12 mice transplanted with RPE-like cells showed significant visual recovery during a 7-month period, whereas those injected with saline, PA6 feeders, or undifferentiated ES cells showed no rescue. Conclusions. ES cells can differentiate, morphologically, and functionally, into RPE-like cells. Based on these findings, differentiated ES cells have the potential for the development of new therapeutic approaches for RPE-specific diseases such as certain forms of retinitis pigmentosa and macular degeneration. Nevertheless, stringent control of retinal detachment and teratoma development will be necessary before initiation of treatment trials.

Krüppel-like transcription factor 4 contributes to maintenance of telomerase activity in stem cells.

The zinc finger Krüppel‐like transcription factor 4 (KLF4) has been implicated in cancer formation and stem cell regulation. However, the function of KLF4 in tumorigenesis and stem cell regulation are poorly understood due to limited knowledge of its targets in these cells. In this study, we have revealed a surprising link between KLF4 and regulation of telomerase that offers important insight into how KLF4 contributes to cancer formation and stem cell regulation. KLF4 sufficiently activated expression of the human telomerase catalytic subunit, human telomerase reverse transcriptase (hTERT), in telomerase‐low alternative lengthening of telomeres (ALT), and fibroblast cells, while downregulation of KLF4 reduced its expression in cancerous and stem cells, which normally exhibits high expression. Furthermore, KLF4‐dependent induction of hTERT was mediated by a KLF4 binding site in the proximal promoter region of hTERT. In human embryonic stem cells, expression of hTERT replaced KLF4 function to maintain their self‐renewal. Therefore, our findings demonstrate that hTERT is one of the major targets of KLF4 in cancer and stem cells to maintain long‐term proliferation potential. STEM Cells 2010; 28:1510–1517.

alpha-Internexin is the only neuronal intermediate filament expressed in developing cerebellar granule neurons.

We have used immunocytochemistry and in situ hybridization to examine the distribution of neuronal intermediate filament proteins and their mRNAs in the developing mouse cerebellum. First, we demonstrate that alpha-internexin is abundantly expressed in the developing cerebellum and is the only neuronal intermediate filament protein expressed in developing, including migrating, granule neurons. Second, in granule neuron reaggregates in vitro, alpha-internexin is the only neuronal intermediate filament protein highly expressed in the processes of the cultured granule neurons. This in vitro observation is consistent with results from immunocytochemistry and in situ hybridization studies of developing granule neurons in vivo, which suggest that alpha-internexin is the major neuronal intermediate filament protein in developing granule neurons. Finally, the neurofilament triplet proteins are expressed later, and coexist with alpha-internexin in other cells, including Purkinje cells and interneurons in the mature mouse cerebellum. These changes in neuronal intermediate filament composition may regulate neuronal maturation and axonal stability in cerebellar development. Furthermore, alpha-internexin may play a key role in neurite outgrowth and the establishment of neuronal cytoarchitecture.

PiggyBac transposon-mediated, reversible gene transfer in human embryonic stem cells.

Permanent and reversible genetic modifications are important approaches to study gene function in different cell types. They are also important for stem cell researchers to explore and test the therapeutic potential of stem cells. The piggyBac transposon from insects is a rising nonviral system that efficiently mutagenizes and mediates gene transfer into the mammalian genome. It is also characterized by its precise excision, leaving no trace sequence behind so that the genomic integrity of the mutated cell can be restored. Here, we use an optimized piggyBac transposon system to mediate gene transfer and expression of a bifunctional fluorescent reporter in human embryonic stem (ES) cells. We provide molecular evidence for transposase-mediated piggyBac integration events and functional evidence for successful expression of a transferred fluorescent protein genes in human ES cells and their in vitro differentiated derivatives. We also demonstrate that the integrated piggyBac transposon can be removed and an undisrupted insertion site can be restored, which implies potential applications for its use in gene therapy and genetics studies.

Involvement of NO/cGMP signaling in the apoptotic and anti-angiogenic effects of β-lapachone on endothelial cells in vitro

Neovascularization is an essential process in tumor development, it is conceivable that anti‐angiogenic treatment may block tumor growth. In angiogenesis, nitric oxide (NO) is an important factor which mediates vascular endothelial cell growth and migration. β‐Lapachone (3,4‐dihydro‐2,2‐dimethyl‐2H‐naphtho‐[1,2‐b]pyran‐5,6‐dione), a natural product extracted from the lapacho tree (Tabebuia avellanedae), has been demonstrated to possess anti‐cancer and anti‐viral effects. Whether β‐lapachone can induce endothelial cell death or has an anti‐angiogenic effect is still an enigma. We investigated the in vitro effect of β‐lapachone on endothelial cells, including human vascular endothelial cell line, EAhy926, and human umbilical vascular endothelial cells (HUVEC). Our results revealed that (1) the intracellular cGMP levels and the mitochondria membrane potential (MMP) decreased, and calpain and caspases were activated, during β‐lapachone‐induced endothelial cell death; (2) co‐treatment with calpain inhibitors (ALLM or ALLN) or the intracellular calcium chelator, BAPTA, but not the general caspase inhibitor, zVAD‐fmk, provided significant protection against apoptosis by preventing the β‐lapachone‐induced MMP decrease and cytoplasmic calcium increase; (3) addition of NO downregulated the β‐lapachone‐induced cGMP depletion and protected the cells from apoptosis by blocking the MMP decrease and the calcium increase; and (4) exogenous NO protects endothelial cells against the cell death induced by β‐lapachone, but not the anti‐angiogenic effect. From all the data above, we demonstrated that NO can attenuate the apoptotic effect of β‐lapachone on human endothelial cells and suggest that β‐lapachone may have potential as an anti‐angiogenic drug. J. Cell. Physiol. 211: 522–532, 2007.

Nuclear efflux of heterogeneous nuclear ribonucleoprotein C1/C2 in apoptotic cells: a novel nuclear export dependent on Rho-associated kinase activation

Using a proteomic approach, we searched for protein changes dependent on Rho-associated kinase (ROCK) during phorbol-12-myristate-13-acetate (PMA)-induced apoptosis. We found that heterogeneous nuclear ribonucleoprotein C1 and C2 (hnRNP C1/C2), two nuclear restricted pre-mRNA binding proteins, are translocated to the cytosolic compartment in a ROCK-dependent manner in PMA-induced pro-apoptotic cells, where nuclear envelopes remain intact. The subcellular localization change of hnRNP C1/C2 appears to be dependent on ROCK-mediated cytoskeletal change and independent of caspase execution and new protein synthesis. Such a ROCK-dependent translocation is also seen in TNFα-induced apoptotic NIH3T3 cells. By overexpressing the dominant active form of ROCK, we showed that a ROCK-mediated signal is sufficient to induce translocation of hnRNP C1/C2. Deletion experiments indicated that the C-terminal 40-amino-acid region of hnRNP C1/C2 is required for ROCK-responsive translocation. By using nuclear yellow fluorescent protein (YFP) fusion, we determined that the C-terminal 40-amino-acid region of hnRNP C1/C2 is a novel nuclear export signal responsive to ROCK-activation. We conclude that a novel nuclear export is activated by the ROCK signaling pathway to exclude hnRNP C1/C2 from nucleus, by which the compartmentalization of specific hnRNP components is disturbed in apoptotic cells.