Human embryonic stem cells-derived endothelial cell therapy facilitates kidney regeneration by stimulating renal resident stem cell proliferation in acute kidney injury

Endothelial cell therapy has been implicated to enhance tissue regeneration and vascularization in ischemic kidney. However, no published study has yet examined direct effects of endothelial cell treatment in kidney recovery. This study investigated the therapeutic efficacy of endothelial cells in a mouse model with acute kidney injury (AKI). Thus, human embryonic stem cells-derived endothelial cells (hESC-ECs) labeled with a reporter system encoding a double fusion reporter gene for firefly luciferase (Fluc) and green fluorescent protein (GFP) were characterized by Fluc imaging and immunofluoresence staining. Cultured hESC-ECs (1×106) were injected into ischemic kidney shortly after AKI. Survival of the transplanted hESC-ECs was monitored in vivo from day 1 to 14 after endothelial cell transplantation and potential impact of hESC-EC treatment on renal regeneration was assessed by histological analyses. We report that a substantial level of bioluminescence activity was detected 24 h after hESC-EC injection followed by a gradual decline from 1 to 14 d. Human ESC-ECs markedly accelerated kidney cell proliferation in response to ischaemia-induced damage, indicated by an elevated number of BrdU+ cells. Co-expression of Sca-1, a kidney stem cell proliferation marker, and BrdU further suggested that the observed stimulation in renal cell regeneration was, at least in part, due to increased proliferation of renal resident stem cells especially within the medullary cords and arteriole. Differentiation of hESC-ECs to smooth muscle cells was also observed at an early stage of kidney recovery. In summary, our results suggest that endothelial cell therapy facilitates kidney recovery by promoting vascularization, trans-differentiation and endogenous renal stem cell proliferation in AKI.     

Advances in studies on hepatic stem cells

The question whether hepatic stem cells exist or not has been debated for several decades. Current researches confirm that there are hepatic stem cells in the liver. Oval cells, putative bipotential hepatic stem cells, are probably located within canals of Hering, portal tracts or branches of biliary trees. Bone marrow is a potential source of oval cells, indicating that there exists a close relationship between liver and hematopoiesis in adulthood. Hepatic stem cells are able to proliferate in vitro and can be induced to differentiate into hepatocytes. This will provide a promising approach of cell transplantation, tissue engineering and gene therapy for liver diseases. In this review, the evidence of their presence, origin, identification, proliferation in vitro, differentiation by induction, application prospects of hepatic stem cells and future directions for the field are discussed.     

Comparative pluripotency analysis of mouse embryonic stem cells derived from wild-type and infertile hermaphrodite somatic cell nuclear transfer blastocysts

Therapeutic cloning, whereby embryonic stem cells （ESCs） are derived from patient-specific cloned blastocysts via somatic cell nuclear transfer （SCNT）, holds great promise for treating many human diseases using regenerative medicine. Teratoma formation and germline transmission have been used to confirm the pluripotency of mouse stem cells, but human embryonic stem cells （hESCs） have not been proven to be fully pluripotent owing to the ethical impossibility of testing for germ line transmis- sion, which would be the strongest evidence for full pluripotency. Therefore, formation of differentiated cells from the three somatic germ layers within a teratoma is taken as the best indicator of pluripotency in hESC lines. The possibility that these lines lack full multi- or pluripotency has not yet been evaluated. In this study, we established 16 mouse ESC lines, including 3 genetically defective nuclear transfer- ESC （ntESC） lines derived from SCNT blastocysts of infertile hermaphrodite F1 mice and 13 ntESC lines derived from SCNT blastocysts of normal F1 mice. We found that the defective ntESCs expressed all in vitro markers of pluripotency and could form teratomas that included derivatives from all three germ layers, but could not be transmitted via the germ line, in contrast with normal ntESCs. Our results in- dicate that teratoma formation assays with hESCs might be an insufficient standard to assess full pluripotency, although they do define multipotency to some degree. More rigorous standards are required to assess the safety of hESCs for therapeutic cloning.     

Generation of tetraploid complementation mice from embryonic stem cells cultured with chemical defined medium

Mouse embryonic stem cells(mESCs)derived from inner cell mass(ICM)of pre-implantation embryos,can maintain undifferentiated state when cultured in N2B27 medium supplemented with GSK3inhibitor CHIR99021 and MEK inhibitor PD0325901(‘‘2i’’)and leukemia inhibitor factor(LIF).Compare to conventional culture medium,all components of this medium are defined.With the N2B27 medium,‘‘2i’’and LIF,mESCs can contribute to the germline of the chimeric embryos,however,whether the‘‘all-ES cells’’mice can been generated by tetraploid complementation is unclear yet,while the tetraploid complementation serve as a golden standard to assess the pluripotency of ES cells.Here,our study showed that mESCs derived and cultured with the N2B27 complete medium could generate fertile mice by tetraploid complementation.In addition,the survival rate of tetraploid complementation mice produced by inbred mES cell lines is higher than the conventional culture condition,and increased the percentage of Oct4 positive cells contrast to conventional medium either.Therefore,the N2B27 medium supplemented with‘‘2i’’and LIF is an alternative choice forthe derivation and long-term culture of mouse embryonic stem cells.     

Differentiation and adaptation epigenetic networks: Translational research in gastric carcinogenesis

There are several kinds of epigenetic networks in the human body including the cell differentiation epigenetic network(DiEN) and the host adaptation epigenetic network(AdEN).DiEN networks are static and cell/tissue-specific.AdEN networks are variable and dependent upon environmental factors.DiEN and AdEN alterations can respectively serve as biomarkers for different kinds of diseases.Cancer is a consequence of accumulated pathophysiological adaptations of tissue stem cells to exposure of environmental carcinogens.Cancer cells are de-differentiated cells that obtain the capacity of unrestricted proliferation,local invasion,and distant migration/metastasis.Both DiEN and AdEN changes can be observed in cancer tissues.Alterations of DNA methylation are the most stable epigenetic modifications and can be sensitively detected in a small cell population.These advantages make DNA methylation the optimal biomarkers for detection of initiated cells in precancerous lesions and metastasis stem cells in cancer tissues.It has been proven that p16 methylation can be used as a diagnostic biomarker to determine malignant potential of epithelium dysplasia in many organs including the stomach.In a large-scale validation study on the DNA methylome of gastric carcinomas(GC),the methylation status of more than 90 CpG islands has been analyzed by DHPLC.Furthermore,GFRA1 demethylation and methylation of SRF and ZNF382 are frequent events during gastric carcinogenesis and consistently correlate to GC metastasis and overall survival of GC patients from China,Japan,and Korea,respectively.In a population study,it has been demonstrated that gradual increasing of plasma miR-211 and other miRNA levels may be an early risk predictor for GC development.     

Advances in the study on induced pluripotent stem cells

Recently, the study on ＂induced pluripotent stem cells＂ （iPS cells） has made a great breakthrough, and it is considered as a new milestone in the history of life science. This progress has updated our traditional concepts about pluripotency control, and provided people with a brand-new strategy for somatic cell nuclear reprogramming. In virtue of its availability and stability, this method holds great potential in both biological and clinical research. In order to introduce this rising field of study, this paper starts with an overview of the development of iPS cell establishment, describes the key steps in generating iPS cells, elaborates several relevant scientific issues, and evaluates its current restrictions and promises in future research.     

Adult neural stem cells-Functional potential and therapeutic applications

The adult brain has been thought traditionally as a structure with a very limited regenerative capacity. It is now evident that neurogenesis in adult mammalian brain is a prevailing phenomenon. Neural stem cells with the ability to self-renew, differentiate into neurons, astrocytes and oligodendrocytes reside in some regions of the adult brain. Adult neurogenesis can be stimulated by many physiological factors including pregnancy. More strikingly, newborn neurons in hippocampus integrally function with local neurons, thus neural stem cells might play important roles in memory and learning function. It seems that neural stem cells could transdifferentiate into other tissues, such as blood cells and muscles. Although there are some impediments in this field, some attempts have been made to employ adult neural stem cells in the cell replacement therapy for traumatic and ischemic brain injuries.     

Effects of L-lactic acid and D,L-lactic acid on viability and osteogenic differentiation of mesenchymal stem cells

Poly(lactic acid) (PLA) and other aliphatic polyesters containing the unit of lactic acid are very popular biodegradable materials. While the degradation products, lactic acids, have been worried to bring with negative influence on biocompatibility, the focused experimental studies are less reported. This study is aimed at an in vitro examination of cytotoxicity of both L-lactic acid and D,L-lactic acid. Mesenchymal stem cells (MSCs) derived from rat bone marrow are employed to test the cytotoxicity of the lactic acids. Considering that the addition of lactic acids not only introduces lactate groups but also alters medium pH and ion strength, these three candidate effects are examined in a decoupled way by setting different comparison groups. The results confirm that the change of medium pH is the predominant factor. It has also been found that D-lactate is more cytotoxic than L-lactate at high concentrations. Yet, either L-or D,L-lactic acids seem acceptable in most of medical applications, because the cytotoxicity is significant only when the concentrations are as high as 20 mmol/L for both of them.     

A Novel Design of Power management integrated circuit with 90 plus efficiency used in AC/DC converter

Recently, resonant AC/DC converter has been accepted by the industry. However, the efficiency will be decreased at light load. So, a novel topology with critical controlling mode combined with resonant ones is proposed in this paper. The new topology can correspond to a 90 plus percent of power converting. So，a novel topology of an state of art integrated circuit, which can be used as power management circuit, has been designed based on the above new topology. A simulator which is specifically suitable for the power controller has been founded in this work and it has been used for the simulation of the novel architecture and the proposed integrated circuit.     

Maintenance of human embryonic stem cells on gelatin

Matrigel is routinely used as a coating material in the feeder-free culture system of human embryonic stem cells （hESCs）. However, matrigel is costive and inconvenient to use. In this study, the possibility of using gelatin as an alternative coating material was investigated. The results showed that, after trypsinization, hESCs were maintained undifferentiated on gelatin. These hESCs expressed pluripotent markers, formed teratoma and maintained a normal karyotype. As measured at passage 10, the hESCs expressed a high level of Oct4 on both gelatin and Matrigeh hESCs growing on gelatin formed AP-positive colonies in similar size and number to those growing on Matrigel （P〉 0.05）. Moreover, hESCs growing on gelatin contained a comparable percentage of SSEA-4-positive cells to those growing on Matrigel （95.1% vs.94.3%, P〉 0.05）. H-1 hESCs were maintained undifferentiated on gelatin for 20 passages and remained the stable normal karyotype. This gelatin-based culture protocol may allow us to propagate hESCs in large scale, with less cost.     

Interactions between the nuclear matrix proteins and the 5'-flanking cis-acting elements of the human ε-globin gene

An erythroid-specific nuclear matrix protein (termed ε-NMPk) in K562 cells, which can specifically bind to the positive stage-specific regulatory element (ε-PRE Ⅱ , - 446- - 419 bp) upstream of the human ε-globin gene, has been identified by using gel mobility shift assay. Meanwhile, Southwestern blotting assay showed that the nuclear matrix protein ε-NMPk in K562, cells may be composed of two polypeptides ( ～ 40 ku). In addition, it is observed in the gel mobility shift assay that the nuclear matrix proteins from K562, HEL and Raji cells can bind to the silencer DNA ( - 392- - 177 bp) in the 5'-flanking sequence of human ε-globin gene respectively. However, the shift band K detected in K562 cells is different from shift band H/R in HEL and Raji cells, suggesting that a common nuclear matrix protein may exist in HEL and Raji cells. Results show that the nuclear matrix protein may play an important role in the regulation of the human ε-globin gene expression.     

Inhibition of PKB/Akt activity involved in apigenininduced apoptosis in human gastric carcinoma cells

Apigenin is a flavonoid widely distributed in fruits and vegetables. It possesses growth inhibitory properties against numerous cancer cell lines. However,the molecular mechanism(s) by which api-genin elicits its effects have not been fully elucidated. Here we studied whether apigenin inhibits growth and induces apoptosis in human gastric carcinoma cells. We showed that the flavonoid inhibited growth of the cells and caused apoptosis,as evidenced by DNA Ladder,cleavage of pro-caspase-3 in a time-dependent manner. Induction of apoptosis was dependent on inhibition of the PKB/Akt activity. We found that while apigenin had no effect on the expression of Akt and Bad,it inhibited specific phosphorylation of the two proteins that are associated with pro-survival mechanisms. We propose that this important flavonoid induces apoptosis in gastric cancer cells by inhibiting Akt activity. Since Akt is often activated in cancers,our findings may have clinical implications.     

Realization of a tunable analog predistorter using parallel combination technique for laser driver applications

This paper describes a new approach for designing analog predistorters that can compensate for the nonlinear distortion of laser drivers in a radio-over-fiber(RoF) system.In contrast to previous works,this paper analyzes the transfer characteristics of CMOS transistors,by combining parallel currents of CMOS transistors in various W/L and negative bias voltages to realize the tunable analog predistortion function.The circuit is fabricated by a standard 0.18μm CMOS technology.The core circuit current consumption is only 15 mA and the entire driver circuit works in a band-pass from 1 ~2.2GHz.Experimental results of two-tone tests have shown that with an analog predistortoer the IIP3 of the laser driver circuit has an improvement of 4.91 dB.     

Neural stem cell transplantation in the repair of spinal cord injury

Neural stem cells are a pronising candidate for neural transplantation aimed at neural cell replacement and repair of the damaged host central nervous system (CNS). Recent studies using neural stem cells have shown that implanted neural stem cells can effectively incorporate into the damaged CNS and differentiate into neurons, astrocytes, and oligodendrocytes. The recent explosion in the field of neural stem cell research has provided insight into the inductive factors influencing neural stem cell differentiation and may yield potential therapies for several neurological disorders, including spinal cord injury. In this review, we summarize recent studies involving neural stem cell biology in both rodents and humans. We also discuss unique advantages and possible mechanisms of using neural stem cell trans plantation in the repair of spinal cord injury.     

Regulation between nitric oxide and MAPK signal transduction in mammals

Nitric oxide (NO) is an important biological messenger in the regulation of tissue homeostasis. It exhibits a wide range of effects during physiological and pathophysiological processes. Typical beneficial properties of NO include the regulation of vascular tone,the protection of cells against apoptosis, the modulation of immune responses, and the killing of microbial pathogens. On the other hand,NO may cause severe vasodilation and myocardial depression during bacterial sepsis or act as a cytotoxic and tissue-damaging molecule in autoimmune diseases. Mitogen-activated protein kinase (MAPK) is a family of serine/threonine protein kinases that are widely distributed in mammalian cells. MAPK cascade plays pivotal roles in gene expression, cell proliferation, differentiation, neuronal survival and programmed cell death under a variety of experimental conditions. MAPKs transduce the signal for the cellular response to extracellular stresses or stimuli. The relation between them, however, has never been reviewed. Based on our researches and other reports in the field, we review their reciprocal regulatory functions.     

Corrosion of magnesium and magnesium –calcium alloy in biologically-simulated environment

A study of biocompatibility and corrosion of both metallic magnesium(Mg) and a magnesium alloy containing 1% calcium(Mg–Ca) were investigated in in vitro culture conditions with and without the presence of bone marrow derived human mesenchymal stem cells(h MSCs).Chemical analysis of the degraded samples was performed using XRD and FEGSEM. The results from the XRD analysis strongly suggested that crystalline phase of magnesium carbonate was present on the surface of both the Mg and Mg–Ca samples. Flame absorption spectrometry was used to analyse the release of magnesium and calcium ions into the cell culture medium. Magnesium concentration was kept consistently at a level ranging from 40 to 80 m M for both Mg and Mg–Ca samples. No cell growth was observed when in direct contact with the metals apart from a few cells observed at the bottom of culture plate containing Mg–Ca alloy. In general, in vitro study of corrosion of Mg–Ca in a biologicallysimulated environment using cell culture medium with the presence of h MSCs demonstrated close resemblances to in vivo corrosion. Although in vitro corrosion of Mg–Ca revealed slow corrosion rate and no immediate cytotoxicity effects to h MSCs, its corrosion rate was still too high to achieve normal stem cell growth when cells and alloys were cultured in vitro in direct contact.     

C-terminal domain of Chk1 regulates its subcellular location and kinase activity for DNA repair

Effector kinase Chk1 is an evolutionarily conserved protein kinase. It is a key mediator linking the mechanisms that monitor DNA integrity to components of the cell cycle engine. In this study, recombinant vectors pEGFP-C1-Chk1/C 288/C 334/C 368 were constructed and transfected into HeLa cells to study the effect of the Chk1 regulatory domain on the regulation of subcellular Chk1 location in response to DNA damage. We found that DNA damage-induced nuclear accumulation is regulated by 34 amino acids (334–368) in the C-terminal regulatory domain. Recombinant vectors pXJ41-Chk1/C 288/C 334/C 368 were co-transfected with reporter plasmid pEGFP-N2 into HeLa cells to study the repair abilities of the different human Chk1 truncation mutants. In addition, recombinant vectors were transfected into HeLa cells to study the effects of the different truncation mutants on the cell cycle. Furthermore, to study the kinase activity of the different truncation mutants, Ser216 phosphorylation of Cdc25C was studied by Western blot analysis. We found that the enzymatic activity of C 368, missing the 108 C-terminal amino acids (368–476), was higher than that of full-length Chk1, and C 368 delayed the cell cycle progression. The enzymatic activity of C 334, missing the 142 C-terminal amino acids (334–476), was equivalent to that of full-length Chk1. C 288, missing the 188 C-terminal amino acids (288–476), had almost no enzymatic activity, suggesting that the regulatory domain contains both inhibitory and regulatory elements. This study provides useful information for further research on Chk1 function.