Rapid and Efficient Conversion of Integration-Free Human Induced Pluripotent Stem Cells to GMP-Grade Culture Conditions

Data suggest that clinical applications of human induced pluripotent stem cells (hiPSCs) will be realized. Nonetheless, clinical applications will require hiPSCs that are free of exogenous DNA and that can be manufactured through Good Manufacturing Practice (GMP). Optimally, derivation of hiPSCs should be rapid and efficient in order to minimize manipulations, reduce potential for accumulation of mutations and minimize financial costs. Previous studies reported the use of modified synthetic mRNAs to reprogram fibroblasts to a pluripotent state. Here, we provide an optimized, fully chemically defined and feeder-free protocol for the derivation of hiPSCs using synthetic mRNAs. The protocol results in derivation of fully reprogrammed hiPSC lines from adult dermal fibroblasts in less than two weeks. The hiPSC lines were successfully tested for their identity, purity, stability and safety at a GMP facility and cryopreserved. To our knowledge, as a proof of principle, these are the first integration-free iPSCs lines that were reproducibly generated through synthetic mRNA reprogramming that could be putatively used for clinical purposes.     

IQPA: Isothermal nucleic acid amplification-based immunoassay using DNAzyme as the reporter system

Immunoassays are often coupled to peroxidase activity for antigen detection. Sensitivity and speed of detection has been increased by the advent of hybrid methods such as immuno-PCR (polymerase chain reaction). However, a more simplified immunoassay that retains both colorimetric peroxidase detection and effective DNA amplification in a setting closer to field application conditions has been nonexistent. Here we describe a method that successfully combines a competitive immunoassay with the new isothermal quadruplex-primed amplification (QPA) to generate excess quadruplex reporter molecules with intrinsic peroxidase DNAzyme activity.     

In <Emphasis Type="Italic">Helicobacter pylori</Emphasis> auto-inducer-2, but not LuxS/MccAB catalysed reverse transsulphuration,regulates motility through modulation of flagellar gene transcription

Background  

LuxS may function as a metabolic enzyme or as the synthase of a quorum sensing signalling molecule, auto-inducer-2 (AI-2); hence, the mechanism underlying phenotypic changes upon luxS inactivation is not always clear. In Helicobacter pylori, we have recently shown that, rather than functioning in recycling methionine as in most bacteria, LuxS (along with newly-characterised MccA and MccB), synthesises cysteine via reverse transsulphuration. In this study, we investigated whether and how LuxS controls motility of H. pylori, specifically if it has its effects via luxS-required cysteine metabolism or via AI-2 synthesis only.     

Giant left atrial appendage

A 42-year-old man was evaluated at our hospital because of paroxysmal atrial fibrillation. Physical examination and ECG during sinus rhythm were unremarkable (no signs of left atrial enlargement).     

Functional and molecular mechanism of intracellular pH regulation in human inducible pluripotent stem cells

AIM To establish a functional and molecular model of the intracellular pH(pH_i) regulatory mechanism in human induced pluripotent stem cells(hiPSCs).METHODS hiP SCs(HPS0077) were kindly provided by Dr. Dai from the Tri-Service General Hospital(IRB No. B-106-09). Changes in the pH_i were detected either by microspectrofluorimetry or by a multimode reader with a pH-sensitive fluorescent probe, BCECF, and the fluorescent ratio was calibrated by the high K~+/nigericin method. NH_4Cl and Na-acetate prepulse techniques were used to induce rapid intracellular acidosis and alkalization, respectively. The buffering power(β) was calculated from the ΔpH_i induced by perfusing different concentrations of(NH_4)_2SO_4. Western blot techniques and immunocytochemistry staining were used to detect the protein expression of pH_i regulators and pluripotency markers.RESULTS In this study, our results indicated that(1) the steadystate pH_i value was found to be 7.5 ± 0.01(n = 20) and 7.68 ± 0.01(n =20) in HEPES and 5% CO_2/HCO_3~- buffered systems, respectively, which were much greater than that in normal adult cells(7.2);(2) in a CO_2/HCO_3~--buffered system, the values of total intracellular buffering power(β) can be described by the following equation: β_(tot) = 107.79(pH_i)~2-1522.2(pH_i) + 5396.9(correlation coefficient R~2 = 0.85), in the estimated pH_i range of 7.1- 8.0;(3) the Na~+/H~+ exchanger(NHE) and the Na~+/HCO_3~- cotransporter(NBC) were found to be functionally activated for acid extrusion for pHi values less than 7.5 and 7.68, respectively;(4) V-ATPase and some other unknown Na~+-independent acid extruder(s) could only be functionally detected for pHi values less than 7.1;(5) the Cl~-/OH~- exchanger(CHE) and the Cl~- /HCO_3 anion exchanger(AE) were found to be responsible for the weakening of intracellular proton loading;(6) besides the CHE and the AE, a Cl~--independent acid loading mechanism was functionally identified; and(7) in hiPSCs, a strong positive correlation was observed between the loss of pluripotency and the weakening of the intracellular acid extrusion mechanism, which included a decrease in the steady-state pH i value and diminished the functional activity and protein expression of the NHE and the NBC.CONCLUSION For the first time, we established a functional and molecular model of a pHi regulatory mechanism and demonstrated its strong positive correlation with hiPSC pluripotency.     

Enhancing productivity for cascade biotransformation of styrene to (S)-vicinal diol with biphasic system in hollow fiber membrane bioreactor

Biotransformation is a green and useful tool for sustainable and selective chemical synthesis. However, it often suffers from the toxicity and inhibition from organic substrates or products. Here, we established a hollow fiber membrane bioreactor (HFMB)-based aqueous/organic biphasic system, for the first time, to enhance the productivity of a cascade biotransformation with strong substrate toxicity and inhibition. The enantioselective trans-dihydroxylation of styrene to (S)-1-phenyl-1,2-ethanediol, catalyzed by Escherichia coli (SSP1) coexpressing styrene monooxygenase and an epoxide hydrolase, was performed in HFMB with organic solvent in the shell side and aqueous cell suspension in the lumen side. Various organic solvents were investigated, and n-hexadecane was found as the best for the HFMB-based biphasic system. Comparing to other reported biphasic systems assisted by HFMB, our system not only shield much of the substrate toxicity but also deflate the product recovery burden in downstream processing as the majority of styrene stayed in organic phase while the diol product mostly remained in the aqueous phase. The established HFMB-based biphasic system enhanced the production titer to 143 mM, being 16-fold higher than the aqueous system and 1.6-fold higher than the traditional dispersive partitioning biphase system. Furthermore, the combination of biphasic system with HFMB prevents the foaming and emulsification, thus reducing the burden in downstream purification. HFMB-based biphasic system could serve as a suitable platform for enhancing the productivity of single-step or cascade biotransformation with toxic substrates to produce useful and valuable chemicals.

     

Differential expression of asialo GM1 on alloreactive cytotoxic T lymphocytes and lymphokine-activated killer cells

The present study was undertaken to examine the differential expression of asialo GM1 (AsGM1) on the responding cells and effectors of alloreactive cytotoxic T lymphocytes (CTL) and lymphokine-induced activated killers (LAK). It was found that AsGM1 was expressed on the 3-day-cultured LAK effectors. Its expression gradually disappeared to the extent that AsGM1 became undetectable after 5 to 6 days of culturing. In contrast, AsGM1 was detected on 3-day CTL generated in mixed-lymphocyte cultures (bulk cultures); however, the levels of AsGM1 expression remained the same for at least 7 days. When examining the expression of AsGM1 on the responding cells, the reciprocal results were obtained. AsGM1 was expressed the LAK responders, but we were unable to demonstrate AsGM1 on CTL responders. Depletion of AsGM1+ cells from the responding population reduced subsequent CTL responses; however, CTL responses could be restored by adding conditioned media containing both interleukin 2 (IL-2) and other helper-T-cell factors and could not be restored by purified IL-2 alone adding at comparable doses. Reconstituting the AsGM1-depleted responders with Lyt-2-depleted splenocytes also restored the CTL response. Furthermore, depletion of AsGM1 cells from the responding population did not reduce the precursor frequency of allo-CTL, whereas the precursor frequency of LAK cells was reduced 42-fold. These findings show that the reduction of CTL responses after depletion of AsGM1+ cells was not due to the removal of precursors; instead, the defect appeared to be in the helper population. We further found that the helper defect was not due to impaired IL-2 production, because the endogenous production of IL-2 AsGM1-depleted responders was not reduced. Therefore, AsGM1+ cells may play a role in the helper pathway other than IL-2 production.