Transformation and immortalization of Leydig cells from the Sprague-Dawley rat by an early genetic region of simian virus 40 DNA

Testicular cell lines

The range of in vivo or in vitro immortalized cell lines currently available provides a variety of model systems for studies of normal and pathological cell functions. The cell lines have been derived from spontaneous or experimentally induced tumors, or through in vitro immortalization. The transgenic (TG) techniques provide a powerful approach, allowing the production of in vivo animal models for a variety of diseases, including malignant tumors, through tissue-specific expression of oncogenes or other tumor-promoting genes. The TG techniques also enable the production of cell lines with specific characteristics, through insertion of desired genes into specific cell types, which can then be immortalized upon cell culture. The use of temperature-sensitive immortalizing genes offers an additional advantage of controlling gene expression, including the proliferation and differentiation of the cells to be immortalized. As regards the male reproductive system, a number of cell lines of testicular somatic cells are currently available. This review covers mainly the immortalized cell lines of testicular Leydig and Sertoli cells, with special reference to murine cell lines for the study of testicular endocrine function and tumorigenesis. These cell lines also provide useful tools to investigate the molecular basis of hormone actions and testicular cell interactions.

Nile Red binding to HepG2 cells: an improved assay for in vitro studies of hepatosteatosis

Nile Red is a fluorescent dye used extensively to study fat accumulation in many types of cells; unfortunately protocols that work well for most cells are not effective for studying drug-induced lipid accumulation in cultured liver cells and hepatocyte-derived cell lines. Using human hepatoma (HepG2) cells, we have developed a simple Nile Red binding assay as a screen for steatosis-inducing compounds. Increases in Nile Red binding in response to known hepatotoxic compounds were observed after incubating treated cells with 1 microM Nile Red for several hours, washing away free Nile Red, and then allowing redistribution, and/or clearance of the lipid-indicator dye. Several compounds known to cause hepatic fat accumulation in vivo were examined and most robustly increased Nile Red binding in HepG2 cells. These include estrogen and other steroids, ethionine, cyclosporin A, and valproic acid. Required concentrations for increased Nile Red binding were generally three-fold or more lower than the cytotoxic concentration determined by a resazurin reduction assay in the same cells. Qualitatively similar Nile Red binding results were obtained when primary canine or rat hepatocytes were used. Morphological differences in Nile Red staining were observed by confocal fluorescence microscopy in HepG2 cells after treatment with different compounds and likely reflect distinct toxicological mechanisms.

Establishment of Leydig cell line, TTE1, from transgenic mice harboring temperature-sensitive simian virus 40 large T-antigen gene

A Leydig cell line, TTE1, has been established from transgenic mice harboring a temperature-sensitive simian virus 40 (tsSV40) large T-antigen gene. The cells grew at a permissive temperature (33 degrees C), but growth was markedly prevented at a nonpermissive temperature (39 degrees C). T-antigen was expressed in the nuclei at 33 degrees C but disappeared at 39 degrees C, indicating that the cells show a temperature-sensitive growth phenotype reflected by the tsSV40 large T-antigen. TTE1 cells did not show any colony-forming activity in soft agar and form tumors in subcutaneous tissue in nude mice, indicating that the cells were not transformed. Alkaline phosphatase and 3beta-hydroxysteroid dehydrogenase (HSD) activities or expression of cytokeratin and vimentin were observed. Reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that TTE1 cells expressed mRNAs encoding 17beta-HSD types 1 and 3, and inhibin-alpha. The cells with unique characteristics, therefore, should serve useful model study the function of Leydig cell.

Hormonal regulation of proliferation of granulosa and Leydig cell lines derived from gonadal tumors of transgenic mice expressing the inhibin-alpha subunit promoter/simian virus 40 T-antigen fusion gene

We have produced a transgenic (TG) mouse model expressing the Simian Virus 40 T-antigen (Tag) gene, driven by a 6-kb fragment of the mouse inhibin-alpha subunit promoter (inh-alpha). The mice develop gonadal tumors with 100% penetrance by the age of 5-8 months, of granulosa cell origin in the ovary, and of Leydig cell origin in the testis. In the present study, we characterized the hormonal regulation of proliferation of two immortalized cell lines, BLT-1, originating from a Leydig cell tumor, and NT-1, originating from a granulosa cell tumor. [3H]-thymidine incorporation in both types of cells was stimulated by activin (> or = 10-30 microg/l), while inhibin had no effect. Transforming growth factor (TGF)-beta, at > or = 0.01 microg/l, stimulated proliferation of the granulosa tumor cells, but no effect was found on the Leydig tumor cells. Progesterone inhibited the proliferation of both cell lines, although the granulosa tumor cells were clearly less sensitive than the Leydig cells to this effect ( > or = 3 micromol/l vs. > 10 nmol/l, respectively). hCG had no effect on the Leydig tumor cell DNA synthesis whereas at high concentration (100 microg/l) it stimulated that of the granulosa cells. We also investigated in BLT-1 and NT-1 cells whether the proliferative changes were related to concomitant changes in Tag expression. In BLT-1 cells, this was stimulated by activin, progesterone and hCG, even though the latter substance did not affect cell proliferation. In contrast, TGF-beta inhibited Tag expression. In NT-1 cells, the expression of Tag was stimulated by activin, while hCG had no effect. In contrast, it was reduced by progesterone, inhibin and TGF-beta. In conclusion, our results indicate that the granulosa and Leydig tumor cells, despite similar mechanism of immortalization, respond differently to several mitotic stimuli. The responses in the level of Tag expression in these cells did not always correlate with the changes observed in cell proliferation, indicating the independence of these two phenomena.

Differential expression of insulin-like growth factor binding proteins in murine hematopoietic stromal cell lines

The expression of the insulin-like growth factor (IGF) system in the hematopoietic microenvironment during ontogeny was studied utilizing immortalized murine cell lines established from several sites of hematopoiesis. Conditioned media was obtained from tissue cultures of murine yolk sac endoderm and mesoderm, fetal liver and adult bone marrow stromal cell lines. IGF-I and -II were quantified by radioimmunoassay and RT-PCR. The presence of insulin-like growth factor binding proteins (IGFBPs) in conditioned media was determined by Western ligand blot and Western immunoblot. IGF-I and IGF-II were present in conditioned media from every stromal cell line and differential expression of the IGFBPs was found among the hematopoietic sites. Stimulation of the cell lines with interleukin-1 alpha altered the IGFBPs in yolk sac endoderm and bone marrow conditioned media. We report that IGF-I and -II are expressed in stromal cell lines obtained from different ontogenic sites of hematopoiesis and IGFBPs are differentially expressed by these sites. The expression of IGFBPs, but not IGFs, is in part regulated by interleukin-1 alpha.