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Abstract Background TGF beta and its receptors are present in both germ cells and somatic cells of the male gonad. However, knock-out strategies for studying spermatogenesis regulation by TGF beta have been disappointing since TGF beta-or TGF beta receptor-null mice do not survive longer than a few weeks. Methods In the present study, we addressed the role of TGF beta-1 on the completion of meiosis by rat pachytene spermatocytes (PS) cocultured with Sertoli cells. Identification and counting of meiotic cells were performed by cytology and cytometry. Results Under our culture conditions, some PS differentiated into round spermatids (RS). When TGF beta-1 was added to the culture medium, neither the number of PS or of secondary spermatocytes nor the half-life of RS was modified by the factor. By contrast, the number of RS and the amount of TP1 mRNA were lower in TGF beta-1-treated cultures than in control cultures. Very few metaphase I cells were ever observed both in control and TGF beta-1-treated wells. Higher numbers of metaphase II were present and their number was enhanced by TGF beta-1 treatment. A TGF beta-like bioactivity was detected in control culture media, the concentration of which increased with the time of culture. Conclusion These results indicate that TGF beta-1 did not change greatly, if any, the yield of the first meiotic division but likely enhanced a bottleneck at the level of metaphase II. Taken together, our results suggest strongly that TGF beta participates in an auto/paracrine pathway of regulation of the meiotic differentiation of rat spermatocytes.

NGF appears to be involved in spermatogenesis. However, mice lacking NGF or TrkA genes do not survive more than a few days whereas p75NTR knockout mice are viable and fertile. Therefore, we addressed the effect of βNGF on spermatogenesis by using the systems of rat germ cell culture we established previously. βNGF did not modify the number of Sertoli cells, pachytene spermatocytes, secondary spermatocytes nor the half-life of round spermatids, but increased the number of secondary meiotic metaphases and decreased the number of round spermatids formed in vitro. These effects of βNGF were reversible and maximal at about 4 × 10-11 M. Conversely, K252a, a Trk-specific kinase inhibitor, enhanced the number of round spermatids above that of control cultures. The presence of βNGF and its receptors TrkA and p75NTR was investigated in testis sections, in Sertoli cell and germ cell fractions, and in germ cell and Sertoli cell co-cultures. βNGF was detected only in germ cells from pachytene spermatocytes of stages VII up to spermatids of stages IX–X. TrkA and p75NTR were detected in Sertoli cells and in these germ cells. Taken together, these results indicate that βNGF should participate in an auto/paracrine pathway of regulation of the second meiotic division of rat spermatocytes in vivo. J. Cell. Physiol. 210: 51–62, 2007. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Porcine Leydig cells, cultured in a chemically defined medium, express luteotropin/human chorionic gonadotropin (LH/hCG) receptor and mRNA transcripts of several sizes (7.6, 6.7, 5.6, 4.7, 4, 2.6 and 1.4 kb). Incubation of these cells with hCG results in a concentration-dependent decrease of both LH/ hCG receptor number and of all mRNA transcripts with a half-maximal at 0.01 nM. Time-course analysis of the effects of maximal (1 nM) concentration of hCG on both receptor number and mRNA levels results in a lag period of about 6-8 h. Thereafter, the receptor number progressively declines to reach a iow point (20% of control) at 36 h, whereas more than 80% of receptor mRNA were lost between 8-12 h after addition of the hormone. By nuclear run-on assays, we showed that hCG caused a slight reduction (13±2%) in LH/hCG receptor gene transcription, which could not explain the rapid and pronounced mRNA decline observed between 8-12 h. In fact, we estimated that hCG reduced 10-fold (from <22 h to 2 h) the half-life of LH/hCG receptor mRNA. Both actinomycin D and cycloheximide blocked the hCG-induced decrease in both receptor number and mRNA levels. These results indicate that the main mechanism by which hCG regulates its own receptor is by inducing a decrease in the stability of its own receptor mRNA and this effect requires induction of transcription and translation, presumably leading to synthesis of a labile factor(s) which favors the degradation of LH/hCG mRNA. Most of the effects of hCG are mediated by cAMP since treatment of cells with its 8-bromo derivative leads to a similar reduction in the level of LH/hCG receptor and mRNA. Finally, the effects of hCG are reversible, since after withdrawal of the hormone there was a recovery of receptor mRNA followed by receptor number. [ABSTRACT FROM AUTHOR]

Environmental contaminants are suspected to be involved in the epidemic incidence of metabolic disorders, food ingestion being a primarily route of exposure. We hypothesized that life-long consumption of a high-fat diet that contains low doses of pollutants will aggravate metabolic disorders induced by obesity itself. Mice were challenged from preconception throughout life with a high-fat diet containing pollutants commonly present in food (2,3,7,8-tetrachlorodibenzo-p-dioxin, polychlorinated biphenyl 153, diethylhexyl phthalate, and bisphenol A), added at low doses in the tolerable daily intake range. We measured several blood parameters, glucose and insulin tolerance, hepatic lipid accumulation, and gene expression in adult mice. Pollutant-exposed mice exhibited significant sex-dependent metabolic disorders in the absence of toxicity and weight gain. In males, pollutants increased the expression of hepatic genes (from 36 to 88%) encoding proteins related to cholesterol biosynthesis and decreased (40%) hepatic total cholesterol levels. In females, there was a marked deterioration of glucose tolerance, which may be related to the 2-fold induction of estrogen sulfotransferase and reduced expression of estrogen receptor α (25%) and estrogen target genes (>34%). Because of the very low doses of pollutants used in the mixture, these findings may have strong implications in terms of understanding the potential role of environmental contaminants in food in the development of metabolic diseases.

NGF appears to be involved in spermatogenesis. However, mice lacking NGF or TrkA genes do not survive more than a few days whereas p75(NTR) knockout mice are viable and fertile. Therefore, we addressed the effect of betaNGF on spermatogenesis by using the systems of rat germ cell culture we established previously. betaNGF did not modify the number of Sertoli cells, pachytene spermatocytes, secondary spermatocytes nor the half-life of round spermatids, but increased the number of secondary meiotic metaphases and decreased the number of round spermatids formed in vitro. These effects of betaNGF were reversible and maximal at about 4 x 10(-11) M. Conversely, K252a, a Trk-specific kinase inhibitor, enhanced the number of round spermatids above that of control cultures. The presence of betaNGF and its receptors TrkA and p75(NTR) was investigated in testis sections, in Sertoli cell and germ cell fractions, and in germ cell and Sertoli cell co-cultures. betaNGF was detected only in germ cells from pachytene spermatocytes of stages VII up to spermatids of stages IX-X. TrkA and p75(NTR) were detected in Sertoli cells and in these germ cells. Taken together, these results indicate that betaNGF should participate in an auto/paracrine pathway of regulation of the second meiotic division of rat spermatocytes in vivo.