Hippocampal Src kinase is required for novelty-induced enhancement of contextual fear extinction.

Exposure to a novel environment enhances the extinction of contextual fear through the "tagging-and-capture" process. However, the underlying molecular mechanisms of novelty-induced enhancement of fear extinction are still unclear. NMDA receptor activity was recently revealed to be required for the enhancement of fear extinction caused by exposure to novelty. Src family kinases (SFKs) act as a molecular hub for regulation of NMDA receptors. We hypothesized that SFKs might be involved in novelty-induced enhancement of fear extinction. We found that the enhancement of fear extinction induced by novelty exposure is accompanied by Src kinase phosphorylation and activation in a restricted time window. Furthermore, intrahippocampal infusion of SFKs inhibitor PP2 inhibits Src kinase phosphorylation and activation, attenuates the activation of NR2B-containing NMDA receptors, and thereby reverses the enhancement of fear extinction induced by novelty exposure. These results suggested that Src kinase may serve as a behavioral tag in the procedural enhancement of fear extinction by novelty exposure.

Baculovirus-transduced mouse amniotic fluid-derived stem cells maintain differentiation potential.

Amniotic fluid-derived stem cells have attracted considerable attention in the field of regenerative medicine. Approach of genetic modification probably enhances their regenerative potential. In this work, we wanted to determine whether baculovirus as a new gene vector could efficiently and safely transduce mouse amniotic fluid-derived stem cells (mAFSs). Cells were isolated from mouse amniotic fluid and cultured in vitro. These cells were analyzed by examining phenotypes and differentiation potential. They were further transduced with baculovirus. Baculovirus-transduced mAFSs were induced to differentiate into adipogenic, osteogenic, myogenic, and neurogenic lineages. Mouse amniotic fluid-derived stem cells were successfully isolated and cultured in vitro. They were positive for CD29 and Sca-1, but negative for CD34, CD45, or CD11b. Furthermore, they could differentiate into adipocytes, osteocytes, myocytes, and neurocytes in vitro. Baculovirus could efficiently transduced mAFSs. More importantly, baculovirus-transduced mAFSs retained differentiation potential. Thus, baculovirus vector effective and safe transduction is an attractive promise for genetic modification of mAFSs. Baculovirus genetically modified mAFSs will probably be more suitable as vehicles for regenerative medicine.

[Comparison of transduction efficiencies of various gene vectors in human bone-marrow-derived mesenchymal stem cells].

OBJECTIVE: To compare the transduction efficiencies of adenoviral vector, adeno-associated viral vector, baculoviral vector, and plasmid vector in human bone-marrow-derived mesenchymal stem cells (hBMSCs). METHODS: The hBMSCs were cultured in vitro and transducted with the adenoviral vector, adeno-associated viral vector, baculoviral vector, and plasmid vector. The expression of target protein was observed by inverted fluorescent microscopy and flow cytometry. RESULTS: Inverted fluorescent microscopy showed that some of the hBMSCs after transduction expressed the green fluorescent protein (GFP) and the hBMSCs transducted with baculoviral vector expressed more GFP than those of other three vectors. Flow cytometry showed that the transduction efficiencies and mean fluorescence intensities of the adenoviral vector, adeno-associated viral vector, and plasmid vector were 42%, 37%, and 22% and 158, 115, and 77, respectively, which were significantly lower than those of baculoviral vector (70%, P < 0.01; 212, P < 0.05; respectively). CONCLUSION: Compared with the adenoviral vector, adeno-associated viral vector, and plasmid vector, the baculoviral vector has higher transduction efficiency in hBMSCs and therefore may be a more suitable gene vector for research in human gene therapy.

[Construction of herpes simplex virus-1 virion protein 22-mediated microdystrophin gene recombinant adenovirus and study on the property of protein transduction].

OBJECTIVE: To construct the recombinant adenovirus containing herpes simplex virus-1 virion protein (VP) 22 and human microdystrophin gene, then the adenovirus was transfected into C2C12 myoblast and studied on the property of protein transduction with VP22-mediated microdystrophin in C2C12 myoblast. METHODS: The full-length VP22 cDNA was obtained from recombinant plasmid pSINrep5-VP22 with PCR, and the product was directionally inserted into pShuttle-CMV to acquire the plasmid pCMV-VP22. Microdystrophin cDNA was obtained from recombinant plasmid pBSK-micro digested with restrictive endonuclease NotI, and the product was directionally inserted into pCMV-VP22 to acquire the plasmid pCMV-VP22-MICDYS. The plasmid of pCMV-VP22-MICDYS was lined with Pme I, and the fragment containing VP22-microdystrophin was reclaimed and transfected into E1 coli BJ5183 with plasmid pAdeasy-1. After having been screened by selected media, the extracted plasmid of positive bacteria was transfected into HEK293 cells with liposome and was identified by observing the cytopathic effect of cells and by PCR method to acquire the recombinant adenovirus Ad-VP22-MICDYS. Finally, the C2C12 myoblast were transfected with the recombinant adenovirus Ad-VP22-MICDYS and Ad-MICDYS, and the expression of microdystrophin was detected by RT-PCR, Western blot and immunocytochemistry. RESULTS: The recombinant adenovirus including VP22 and microdystrophin gene was successfully constructed. VP22 transferred VP22-microdystrophin fused protein from infected C2C12 myoblast into uninfected cells and enhance the expression of microdystrophin in myoblast. CONCLUSIONS: Recombinant adenovirus containing VP22 and microdystrophin gene was constructed successfully. VP22 can enhance the expression with microdystrophin in myoblast. It lays the foundation for further studying on VP22-mediated recombinant including microdystrophin gene to cure Duchenne muscular dystrophy.

[A novel polymorphism of IGFBP-3 gene and its relationship with several wool traits in Chinese Merino sheep].

In this study, PCR-SSCP analysis was used to identify genetic variation in IGFBP-3 gene in Chinese Merino and Kazakh sheep. A PCR product of 178 bp corresponding to partial intron1 illustrated three unique binding patterns by SSCP analysis. Frequencies of the genotype AA, AB, BB and allele A, B in Chinese Merino sheep were 0.70, 0.24, 0.06, and 0.82, 0.18 respectively , and they were 0.87, 0.13, 0.00, and 0.93, 0.07 respectively in Kazaka sheep. Sequence analysis revealed a G/T transversion at position 122 of the fragment. This polymorphic locus of IGFBP-3 gene was at Hardy-Weinberg dis-equilibrium (P<0.01) in the two breeds. Different genotypes slightly affected several wool traits of Chinese Merino sheep. The individuals of genotype AA, AB, and BB had no significant difference in post-shearing weight and clean wool rate. Sta-ple length (SL) was decreased with the genotype of AA, AB, and BB, and the difference between AA and AB was significant (P<0.01). Greasy fleece weight (GFW) and follicle density in individuals of genotype AA was significantly lower than that in individuals of genotype AB (P<0.01) and BB (P<0.05); Average fiber diameter (AFD) in individuals of genotype AA was significantly higher than that in individuals of genotype AB (P<0.01) and BB (P<0.05).

[Transduction of various mammalian bone marrow-derived mesenchymal stem cells by baculovirus].

The use of stem cells will lead to novel treatments for a wide range of diseases due to their properties of self-renewing, pluripotent, and undifferentiated state, and the stem cells are usually genetically modified for cell and gene therapy. If the baculovirus, as a new gene vector, can be effectively transduced into various mammalian bone marrow-derived mesenchymal stem cells (BMSCs) in vitro, it will be a better gene vector to genetically modify the stem cells. The aim of the present study is to investigate the transduction efficiency of recombinant baculovirus (BacV-CMV-EGFP), which expressed a reporter gene encoding enhanced green fluorescent protein (EGFP) under a cytomegalovirus immediate early (CMV-IE) promoter, into various mammalian BMSCs. The BMSCs of mouse, rat, porcine, rhesus, and human were cultured primarily in vitro. After more than three passages, the mammalian BMSCs were seeded into dishes and cultured in a humidified incubator at 37 °C with 5% CO(2). When the cells reached about 80% confluence, the complete medium was removed by aspiration. The cells were transduced with recombinant baculovirus at a multiplicity of infection (MOI) of 200 vector genomes/cell with 500 µL PBS at 25 °C for 4 h. At the end of baculovirus transduction, cells were washed and incubated with 2 mL complete medium, and baculovirus-transduced mammalian BMSCs were cultured in a humidified incubator for 2 d. Then, the inverted fluorescent microscope was used to observe GFP expressions in different mammalian BMSCs, and flow cytometry was used to detect the transduction efficiency of baculovirus in various mammalian BMSCs. After more than three passages, the BMSCs of mouse, rat, porcine, rhesus, and human showed a homogeneous spindle-shaped morphology. Compared with the BMSCs of mouse, rat and porcine, the inverted fluorescent microscope observations showed that there were more BMSCs expressing GFP and greater mean fluorescence intensity in rhesus and human transduced with baculovirus. The baculovirus could efficiently transduce into the BMSCs of mouse, rat, porcine, rhesus and human, and the transduction efficiency was (20.21±3.02)%, (22.51±4.48)%, (39.13±5.79)%, (71.16±5.36)% and (70.67±3.74)%, respectively. In conclusion, baculovirus displays different transduction efficiency into various mammalian BMSCs. Due to the high transduction efficiency for primate and human BMSCs, baculovirus is possibly a more suitable gene vector to genetically modify BMSCs of human and primates.

Comparative study of mesenchymal stem cells from C57BL/10 and mdx mice.

BACKGROUND: Human mesenchymal stem cells (MSCs) have been studied and applied extensively because of their ability to self-renew and differentiate into various cell types. Since most human diseases models are murine, mouse MSCs should have been studied in detail. The mdx mouse - a Duchenne muscular dystrophy model - was produced by introducing a point mutation in the dystrophin gene. To understand the role of dystrophin in MSCs, we compared MSCs from mdx and C57BL/10 mice, focusing particularly on the aspects of light and electron microscopic morphology, immunophenotyping, and differentiation potential. RESULTS: Our study showed that at passage 10, mdx-MSCs exhibited increased heterochromatin, larger vacuoles, and more lysosomes under electron microscopy compared to C57BL/10-MSCs. C57BL/10-MSCs formed a few myotubes, while mdx-MSCs did not at the same passages. By passage 21, mdx-MSCs but not C57BL/10-MSCs had gradually lost their proliferative ability. In addition, a significant difference in the expression of CD34, not Sca-1 and CD11b, was observed between the MSCs from the 2 mice. CONCLUSION: Our current study reveals that the MSCs from the 2 mice, namely, C57BL/10 and mdx, exhibit differences in proliferative and myogenic abilities. The results suggest that the changes in mouse MSC behavior may be influenced by lack of dystrophin protein in mdx mouse.