Optimization of trypsin digestion intensity to obtain high-purity in vitro cultured astrocytes / 生理学报

The aim of the present study was to observe the effect of trypsin digestion on the purity of in vitro cultured astrocytes and optimize the culture methods. The cerebral cortical tissue from newborn Sprague Dawley (SD) rats was isolated and digested with 0.25% trypsin for 20, 30, or 40 min. The obtained single cell suspension was then cultured. Once reaching confluence, the cells were shaken at a constant temperature. Then, each of 20 and 30 min groups was subdivided into two groups, the control group with normal digestion and two-time-digestion group, and the cells were passaged and purified. Through inverted phase contrast microscope and MTT assay, cell growth and proliferation were observed, respectively. Immunofluorescence for glial fibrillary acidic protein (GFAP) was used to observe the morphology of astrocytes and to assess their purity in different stages. Flow cytometric analysis was used to detect the apoptotic rates of purified astrocytes. The results showed that, the cells being digested for 20 min usually reached confluence at 9 d after seeding. When the digestion time was extended to 30 min, the cells grew faster and reached confluence at 7 d after seeding, meanwhile the morphology of astrocytes was normal, GFAP positive rate (70.2 ± 4.0)% being much higher than that of the 20 min group (P < 0.05). Compared with 20 min group, 40 min group showed higher GFAP positive rate, whereas the cell proliferation was slower, and cell injury was more obvious. After shaking at constant temperature, two times of trypsin digestion could decrease the number of contaminated cells after passage. The GFAP positive rates of two-time-digestion groups in passage 1 (P1) were higher than those of corresponding control groups, and the GFAP positive rate of 30 min + two-time-digestion group in P1 reached (98.1 ± 1.7)%, which was equivalent to that of the 20 min + control group in P3. However, the apoptotic rate showed no significant difference between these two groups. Based on above mentioned results, we conclude that 30 min + two-time of trypsin digestion effectively improves the purity of astrocytes and shortens the time of primary culture and purification, suggesting that it is a rapid and effective method to obtain astrocytes with high purity in vitro.

Immunization with recombinant HBcAg and β-amyloid peptide fusion protein promotes clearance of intrahippocampally injected β-amyloid peptide in rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the effects of immunization with the fusion protein CAC (a product of prokaryotic expression of recombinant HBcAg and β-amyloid peptide fusion gene) against the toxicity induced by intrahippocampal injection of aggregated β-amyloid peptide (Aβ) in rats.</p><p><b>METHODS</b>SD rats were immunized intraperitoneally with the fusion protein CAC, and the titer of anti-Aβ antibody was evaluated by ELISA. When the titers of the anti-Aβ antibody reached 1:3 000, aggregated Aβ was injected into the CA1 region of the rat hippocampus. Two weeks after Aβ injection, the rats underwent morris water maze test before sacrificed to prepare the brain slices with Congo red and haematoxylin staining.</p><p><b>RESULTS</b>The titer of anti-Aβ antibody reached 1:3 000 after 5 immunizations with the fusion protein. After Aβ injection, the saline-immunized rats showed a reduced cognitive behavior in the Morris water maze test compared to the CAC-immunized rats. In the saline-immunized rats, the neurons around the site of Aβ injection exhibited obvious cell damages with Aβ deposits and glial infiltration, whereas in CAC-immunized rats, Aβ deposits were significantly reduced or even absent.</p><p><b>CONCLUSION</b>Immunization with the fusion protein CAC can inhibit the toxicity induced by intrahippocampal aggregated Aβ injection.</p>

Specific suppression of beta-secretase gene expression by short interfering RNA in mammalian cells / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate whether short interfering RNAs(siRNAs) of beta-site APP cleaving enzyme (BACE) can inhibit the expression of BACE in mammalian cells.</p><p><b>METHODS</b>The gene of EGFP, U6 promoter and beta-secretase targeting siRNA were cloned by PCR, respectively. The PCR products were inserted into plasmid pLXSN. The interfering vector pLXSN/EGFP-U6-siBACE was transferred into SK-N-SH cells to express BACE. The inhibition effect of BACE siRNA on BACE expression was investigated by fluoroscopy and immunohistochemistry method.</p><p><b>RESULT</b>The interfering vector pLXSN/EGFP-U6-siBACE was constructed successfully. The BACE siRNA inhibited the expression of BACE in the SK-N-SH cells specifically and effectively, and the production of A beta was reduced.</p><p><b>CONCLUSION</b>BACE siRNA can inhibit the expression of BACE gene of mammalian cells.</p>