[Primary culture and identification of rat glomerular podocytes]

OBJECTIVE

To establish an easy and feasible method for primary culture and identification of rat glomerular podocytes.

METHODS

Glomeruli from Sprague-Dawley (SD) rats weighing 60-100 gram were isolated by the method of different size combination of screen. Isolated glomeruli were appropriately digested with 2 g/L type IV collagenase and cultured in 25 cm2 plastic flask coated with rat tail collagen in K1-3T3 medium with ITS-X (containing insulin-transferrin-selenium). Subculture of primary cultured epithelial cells was performed at 9-10 days after implantation of collagenase digested glomeruli. Podocytes were identified by the morphology study with scanning electron microscope and inverted microscope, as well as the immunohistochemistry staining (SP methods) study for the expression of keratin, desmin and Wilms' tumor suppressor-1 (WT-1).

RESULTS

Epithelial cells outgrowth from isolated glomeruli appeared after 3 days primary culture and grew to confluence with cobblestone-appearance at 9-10 days. These cobblestone cells were subcultured at this point and gradually conversed into large, flat arborized cells with well-developed processes and microvilli. These arborized cells were negative expression with desmin staining and showed positive expression of cytokeratin and WT-1, which indicated that they were podocytes.

CONCLUSION

Implantating collagenase digested-glomeruli is an easy and feasible method for primary culture of rat glomerular podocytes. WT-1 may serve as a good marker to identify rat glomerular podocytes.

[Treatment of early avascular necrosis of femoral head by core decompression and transplantation of human hepatic growth factor gene-modified osteoblasts: experiment with rabbits]

OBJECTIVE

To evaluate the effects of transplantation of human hepatocyte growth factor (hHGF) gene-modified osteoblasts combined with core decompression in treatment of avascular necrosis of femoral head (ANFH).

METHODS

The plasmid pcDNA3.1(+)-hHGF containing hHGF gene was constructed. Osteoblasts were isolated from fetal rabbits, cultured, and transfect3d with the plasmid pcDNA3.1(+)-hHGF or blank plasmid pcDNA3.1(+), or used as controls. Thirty-six adult New Zealand rabbits were made into ANFH models, underwent core decompression, and were randomly divided into 3 groups. Group A, transplanted with osteoblasts transfected with pcDNA3.1(+)-hHGF plasmid, Group B, transplanted with osteoblasts not transfected with pcDNA3.1(+)-hHGF plasmid, and Group C, injected with PBS medium. 2, 4, and 8 weeks later samples of femoral head were obtained to undergo CT, histological examination, and capillary ink infusion so as to observe the angiogenesis and osteogenesis.

RESULTS

The pcDNA3.1(+)-hHGF transfected osteoblasts showed stable expression of hHGF. The numbers of newly formed vessels of the femoral heads of the group transfected with pcDNA3.1(+)-hHGF-transfected osteoblasts 2 and 4 weeks later were (29.47 +/- 1.64) and (34.02 +/- 1.72)/cm2 respectively, both significantly higher than those of the group transfected with blank plasmid-transfected osteoblasts [(20.61 +/- 1.91) and (25.57 + 2.20)/cm2 respectively, both P <0. 01]. Eight weeks later the numbers of mature trabecular bone and bone marrow of Groups A and B were significantly higher than those of Group C.

CONCLUSION

Core decompression combined with transplantation of HGF gene-modified osteoblasts promotes angiogenesis, enhances bone formation, and improves the restoration of avascular necrosis of femoral head.

[Inhibitory effect of human brain myelin basic protein on H2O2-induced apoptosis of human lung cancer cell line YTLMC-90]

BACKGROUND & OBJECTIVE

Human brain myelin basic protein (MBP) distributes in nervous system and other tissues extensively, and can be detected in many kinds of tumor cells, such as lung cancer, breast cancer, and neuroglioma. However, it has not been reported whether MBP is relevant to the activity of neural invasion of tumors and whether MBP plays a role in biological behaviors of human lung cancer cells. This study was to investigate the inhibitory effect of MBP on hydrogen peroxide (H2O2)-induced apoptosis of human lung cancer cell line YTLMC-90.

METHODS

YTLMC-90 cells were transfected with plasmid pSVCEPMBPCAT containing MBP cDNA minigene (test group), or empty vector pSVCEPCAT, or received no transfection (control group), and exposed to H2O2. The expression of MBP in YTLMC-90 cells was detected by Western blot. Cell proliferation was measured by MTT assay. The morphologic and ultra-structural changes of apoptotic cells were observed by microscopy with fluorescent staining of acridine orange (AO) and electron microscopy. The DNA fragmentation was examined by agarose gel electrophoresis.

RESULTS

After exposed to 200 micromol/L H2O2 for 24 h, the inhibitory rate of cell growth was significantly lower in test group than in empty vector group and control group (36.67% vs. 78.67% and 84.00%, P<0.001). The morphologic and biochemical changes of apoptotic cells, such as shrinkage of cytoplasm and nucleus, fragmentation of chromatin, and ladder pattern of DNA, were commonly observed in cells in control group, but these apoptotic features were not discovered in test group.

CONCLUSION

MBP markedly inhibits H2O2 cytotoxicity to YTLMC-90 cells through promoting cell proliferation and antagonizing H2O2-induced apoptosis.

[Suppressive effect of brain derived neurotrophic factor on H2O2-induced apoptosis in human lung cancer cell YTMLC-90]

BACKGROUND & OBJECTIVE

It has been shown that neurotrophic factors such as nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), and neurotrophin (NT-3/4) are synthesized in a variety of cells inside and outside the nervous system. These factors are not only able to promote neural survival, proliferation and apoptosis of neural cells but also relevant to the activity of neural invasion of tumors. It has not been reported to date whether BDNF may play roles in the biological behavior of human lung cancer cells. The aim of this experiment was to investigate the effect of BDNF on hydrogen peroxide (H2O2)-induced apoptosis in the human lung cancer cell line YTMLC-90.

METHODS

The minigene pSVCEPBFCAT containing the promoter and enhancer elements of the human a1(I) collagen gene(COLIA1) at its 3' terminus followed by hBDNF gene cDNA was transfected and derived BDNF ectopic expression in the human lung cancer cells. The cell proliferation was measured by MTT assay. The morphological and ultra-structural changes of apoptotic cells were observed by microscopy with fluorescent stain of acridine orange and electron microscopy. The DNA fragmentation was examined by agarose gel electrophoresis.

RESULTS

After exposure of growing cells to 200 micromol/L H2O2 for 24 hours, the inhibition rate of cell growth was 30% in the pSVCEPBFCAT-transfected YTMLC-90, 84.60% in controls of non-transfected YTMLC-90, and 80.00% in pSVCEPCAT-transfected YTMLC-90, respectively (P< 0.001). The morphological and biochemical changes of apoptotic cells such as shrinkage of cytoplasm and nucleus,fragmentation of the chromatin, and ladder pattern of DNA were commonly observed in the cell population of controls, but these apoptotic features were not discovered in the pSVCEPBFCAT-transfected YTMLC-90.

CONCLUSION

BDNF markedly inhibits H2O2 cytotoxicity on human lung cancer cell YTMLC-90 by promoting YTMLC-90 proliferation and antagonizing H2O2-induced apoptosis.

[Inhibition of telomerase activity by ribozyme targeted to human telomerase transcriptase]

Human telomerase reverse transcriptase (hTERT) is the catalytic subunit and the key factor which controls the telomerase activity,so it is the best choice to inhibit telomerase through controling hTERT expression.In this work,a hammer head ribozyme directed against the hTERT mRNA (hTERTRZ) was designed and synthesized to serve as a telomerase inhibitor. In order to test its in vitro cleavage activity, two in vitro transcription plasmids containing hTERTRZ and hTERT gene respectively were constructed. Ribozyme RNA and DIG-labeled-hTERT were synthesized by in vitro transcription. In vitro cleavage reactions were carried out by mixing the hTERTRZ with DIG-labeled-hTERT under different reaction conditions, and cleavage bands were detected by digoxin chemiluminescent assay. hTERTRZ showed a specific cleavage activity against the hTERT used as template. To investigate its in vivo effect of telomerase inhibition in tumor cells, a eukaryotic expression plasmid containing the hTERT ribozyme gene was introduced into HeLa cells and hepatoma cells by using LipofectAMINE. In the transfectants, the level of intact hTERT mRNA and the telomerase activity were clearly reduced, and the telomere length of these clones was apparently shortened at the beginning period, then kept a fixed value without further shortening. All the transfectants with ribozyme grew clearly more slowly than the parental cell line. The doubling time of the tansfectants prolonged compared to the negative control, but no apparent apoptosis was shown even at their 37th passage. These findings suggest the potential application of this ribozyme as a new theraputic agent directed against immortalized cancer cells.

[Observation on application of solid phase indirect hemadsorption assay for detection IgM antibodies to tuberculosis in non-serum specimens]

We used solid phase indirect hemadsorption assay (SPIHA) to detect specific IgM antibodies in specimens from cerebrospinal fluid, pleural fluid and ascitic fluid in patients with tuberculosis and compared with the enzyme linked immunosorbent assay (ELISA) and indirect hemagglutination assay (IHA). The result showed that detection of tuberculous specific IgM antibodies in cerebrospinal fluid by SPIHA is important for diagnosing the tuberculous meningitis.