Influence of 5α-dihydrotestosterone and 17β-estradiol on human Sertoli cells metabolism

Sertoli cells metabolize glucose, converting it to lactate that is used by developing germ cells for their energy metabolism. Androgens and oestrogens have metabolic roles that reach far beyond reproductive processes. So, the main purpose of this study was to examine the effect of sex steroid hormones on metabolite secretion/consumption in human Sertoli cells. Human Sertoli cell-enriched primary cultures were maintained in a defined medium for 50 h and glucose, pyruvate, lactate and alanine variations were determined using (1) H-NMR spectra analysis, in the absence or presence of 100 nm 17β-estradiol (E(2) ) or 100 nm 5α-dihydrotestosterone (DHT). The mRNA expression levels of glucose transporters, lactate dehydrogenase and monocarboxylate transporters were also determined using semi-quantitative RT-PCR. Cells cultured in the absence (control) or presence of E(2) consumed the same amounts of glucose at similar rates during the 50 h. During the first 15 h of treatment with DHT, glucose consumption and glucose consumption rate were significantly higher. Nevertheless, DHT-treated cells secreted a significantly lower amount of lactate than control and E(2) -treated cells. Such a decrease was concomitant with a significant decrease in lactate dehydrogenase A mRNA levels after 50 h treatment in DHT-treated groups. Finally, alanine production was significantly increased in E(2) -treated cells after 25 h treatment, which indicated a lower redox/higher oxidative state for the cells on those conditions. These results support the existence of a relationship between sex steroid hormones action and energy metabolism, providing the first assessment of androgens and oestrogens as metabolic modulators of human Sertoli cells.

346 ULTRASTRUCTURE OF A HUMAN GIANT MII OOCYTE: CASE REPORT

The occurrence of giant oocytes has been reported with considerable frequency during IVF procedures in women of all ages and was associated with an increased response to gonadotrophin therapy. Previous studies suggested that giant oocytes, larger in diameter than normal oocytes and either at the GV, MI, or MII stage, might be a source of human digynic triploidy. However, to our knowledge there are no previous reports concerning the ultrastructure of human giant oocytes, and therefore the objective of this study was to characterize a human giant mature metaphase II oocyte from the ultrastuctural point of view. A giant oocyte with a visible polar body was used under informed consent, after controlled superovulation during a IVF treatment cycle. The oocyte was fixed with Karnovsky’s fixative, post-fixed in 2% OsO4 in 0.15 M cacodylate buffer, pH 7.2, dehydrated and embedded in Epon Semithin and ultrathin sections were cut with a diamond Diatome knife (Diatome, Hatfield, PA, USA) in a LKB ultramicrotome. Semithin sections were stained with aqueous azur II and methylene blue (1:1). Ultrathin sections were collected on 200 mesh copper grids (Taab Laboratories Equipment Ltd, Aldermaston, UK) and stained with 3% aqueous uranyl acetate (20 min) and Reynolds lead citrate (10 min). Contrast ultrathin sections were observed in a JEOL 100XII transmission electron microscope (JEOL Ltd., Tokyo, Japan) operated at 60 Kv. Cytogenetic analysis was not performed in this oocyte. At the time of collection, the giant oocyte was 1.4-fold larger than average size oocytes and contained a fragmented polar body. The zona pellucida had a normal loosely fibrillar structure and the perivitelline space was normal containing remnants of follicular cells. The cytoplasmic organelles were no uniformly dispersed with a large organelle-free zone (lake) observed in the periphery of the oocyte cortex and smaller focal lakes visible in the subcortex. Within the cortex the dense cortical vesicles were reduced in number and did not form one or two continuous rows beneath the oolemma. Smooth endoplasmic reticulum (SER) aggregates of tubules were also scarce but underdeveloped SER aggregates of tubules were present in the cortex. The distribution of the SER large and middle vesicles was abnormal: these organelles were nearly absent in the cortex but present in the inner cytoplasm. The content of some vesicles was denser than normal. We also observed the presence of several large secondary lysosomes filled with multiple small and medium lipid droplets (lipofuscin bodies), corresponding to retractile bodies located in the cortex. Large dense vesicles of different densities and volumes were found in the cortex and subcortex. The polar body showed very few cortical vesicles and did not contain mitochondria and SER large or small vesicles. The condensed chromosomes were aligned on the metaphase II plate, in the cortex of the oocyte. The ultrastructural alterations observed in this oocyte corroborated the conclusions of previous genetic studies and confirmed that giant oocytes are immature cytoplasmatically and would be associated with a higher frequency of abnormal development following fertilization. Thus, giant oocytes should not be used in IVF treatments. ASL was supported by FCT, Portugal.

Intracellular pH regulation in human Sertoli cells: role of membrane transporters

Sertoli cells are responsible for regulating a wide range of processes that lead to the differentiation of male germ cells into spermatozoa. Intracellular pH (pHi) is an important parameter in cell physiology regulating namely cell metabolism and differentiation. However, pHi regulation mechanisms in Sertoli cells have not yet been systematically elucidated. In this work, pHi was determined in primary cultures of human Sertoli cells. Sertoli cells were exposed to weak acids, which caused a rapid acidification of the intracellular milieu. pHi then recovered by a mechanism that was shown to be particularly sensitive to the presence of the inhibitor DIDS (4,4′-diisothiocyanostilbene disulfonic acid). In the presence of amiloride and PSA (picrylsulfonic acid), pHi recovery was also significantly affected. These results indicate that, in the experimental conditions used, pHi is regulated by the action of an Na+-driven HCO3−/Cl−exchanger and an Na+/HCO3−co-transporter and also by the action of the Na+/H+exchanger. On the other hand, pHi recovery was only slightly affected by concanamycin A, suggesting that V-Type ATPases do not have a relevant action on pHi regulation in human Sertoli cells, and was independent of the presence of bumetanide, suggesting that the inhibition of the Na+/K+/Cl−co-transporter does not affect pHi recovery, not even indirectly via the shift of ionic gradients. Finally, pHi was shown to be sensitive to the removal of external Cl−, but not of Na+or K+, evidencing the presence of a membrane Cl−-dependent base extruder, namely the Na+-independent HCO3−/Cl−exchanger, and its role on pHi maintenance on these cells.

Abnormal methylation of imprinted genes in human sperm is associated with oligozoospermia

Genomic imprinting marks in the male germ line are already established in the adult germinal stem cell population. We studied the methylation patterns of H19 and MEST imprinted genes in sperm of control and oligozoospermic patients, by bisulphite genomic sequencing. We here report that 7 out of 15 (46.7%) patients with a sperm count below 10 x 10(6)/ml display defective methylation of H19 and/or MEST imprinted genes. In these cases, hypomethylation was observed in 5.54% (1.2-8.3%) and complete unmethylation in 2.95% (0-5.9%) of H19 clones. Similarly, for the CTCF-binding site 6, hypomethylation occurred in 4.8% (1.2-8.9%) and complete unmethylation in 3.7% (0-6.9%) of the clones. Conversely, hypermethylation occurred in 8.3% (3.8-12.2%) and complete methylation in 6.1% (3.8-7.6%) of MEST clones. Of the seven patients presenting imprinting errors, two had both H19 hypomethylation and MEST hypermethylation, whereas five displayed only one imprinted gene affected. The frequency of patients with MEST hypermethylation was highest in the severe oligozoospermia group (2/5 patients), whereas H19 hypomethylation was more frequent in the moderate oligozoospermia (2/5 patients). In all cases, global sperm genome methylation analysis (LINE1 transposon) suggested that defects were specific for imprinted genes. These findings could contribute to an explanation of the cause of Silver-Russell syndrome in children born with H19 hypomethylation after assisted reproductive technologies (ART). Additionally, unmethylation of the CTCF-binding site could lead to inactivation of the paternal IGF2 gene, and be linked to decreased embryo quality and birth weight, often associated with ART.