Telomere lengths in human oocytes, cleavage stage embryos and blastocysts

Telomeres are repeated sequences that protect the ends of chromosomes and harbour DNA-repair proteins. Telomeres shorten during each cell division in the absence of telomerase. When telomere length becomes critically short, cell senescence occurs. Telomere length therefore reflects both cellular ageing and capacity for division. We have measured telomere length in human germinal vesicle (GV) oocytes and pre-implantation embryos, by quantitative fluorescence in-situ hybridisation (Q-FISH), providing baseline data towards our hypothesis that telomere length is a marker of embryo quality. The numbers of fluorescent foci suggest that extensive clustering of telomeres occurs in mature GV stage oocytes, and in pre-implantation embryos. When calculating average telomere length by assuming that each signal presents one telomere, the calculated telomere length decreased from the oocyte to the cleavage stages, and increased between the cleavage stages and the blastocyst (11.12 vs 8.43 vs 12.22kb respectively, p<0.001). Other methods of calculation, based upon expected maximum and minimum numbers of telomeres, confirm that telomere length in blastocysts is significantly longer than cleavage stages. Individual blastomeres within an embryo showed substantial variation in calculated average telomere length. This study implies that telomere length changes according to the stage of pre-implantation embryo development

Long term effects of micro-surgical testicular sperm extraction on androgen status in patients with non obstructive azoospermia

BACKGROUND: The aim of our study was to review the results of microsurgically performed testicular sperm extraction (TESE) and to evaluate its possible long term effects on serum testosterone (T). METHODS: We operated on 48 men (35 +/- 8 years) with non-obstructive azoospermia (NOA). If no spermatozoa were found following a micro epididymal sperm extraction (Silber et al., 1994) and testicular biopsy, testicular microdissection was performed or multiple microsurgical testicular biopsies were taken. The mean follow-up of the serum T was 2.4 +/- 1.1 years. RESULTS: Sperm was retrieved in 17/48 (35%) of the men. The per couple take home baby rate if sperm was retrieved was 4/17 (24%). Serum T decreased significantly at follow-up (p < 0.05) and 5/31 (16%) de novo androgen deficiencies developed CONCLUSION: In patients with non-obstructive azoospermia in whom no spermatozoa were found following a micro epididymal sperm aspiration and a simple testicular biopsy, we were able to retrieve spermatozoa in 35% of the men. The take home baby rate was 24% among couples with spermatozoa present upon TESE. De novo androgen deficiency occurred in 16% of the male patients following TESE indicating that, in men with NOA, long term hormonal follow up is recommended after TESE

Human sperm handling in intracytoplasmic sperm injection processes: In vitro studies on mouse oocyte activation, embryo development competence and sperm oxidation–reduction potential

Polyvinylpyrrolidone (PVP) and hyaluronic acid (HA) are routinely used in handling spermatozoa for intracytoplasmic sperm injection (ICSI). As there are still concerns about possible adverse effects on the embryo, this study investigated sperm handling in a mouse ICSI model to (i) evaluate oocyte activation after injection of spermatozoa selected for rotational or linear motion in PVP; (ii) assess the effect of sperm selection in PVP, HA and medium on oocyte activation; (iii) examine the effects of PVP and HA on parthenogenetic oocyte activation and embryo development; and (iv) assess the oxidation–reduction potential (ORP) of spermatozoa exposed to PVP, HA or medium. Oocyte activation was higher when spermatozoa exhibited rotational motion rather than linear motion (79% vs. 52%; p = .05). There was no difference in oocyte activation and embryo development after parthenogenetic oocyte activation after sperm injection using PVP, HA or medium-incubated spermatozoa. PVP-selected spermatozoa exhibited lower (p < .0001) ORP levels than using HA. Thus, results indicate that the sperm handling method and the type of medium used impact ICSI outcomes. Overall, sperm incubation in PVP, HA and medium yields similar outcomes with regard to oocyte activation and embryo development. However, PVP provides more antioxidative protection than HA and should therefore be preferred for sperm manipulation

Paternal effects on early embryogenesis

Historically, less attention has been paid to paternal effects on early embryogenesis than maternal effects. However, it is now apparent that certain male factor infertility phenotypes are associated with increased DNA fragmentation and/or chromosome aneuploidies that may compromise early embryonic development. In addition, there is a growing body of evidence that the fertilizing sperm has more function than just carrying an intact, haploid genome. The paternally inherited centrosome is essential for normal fertilization, and the success of higher order chromatin packaging may impact embryogenesis. Epigenetic modifications of sperm chromatin may contribute to the reprogramming of the genome, and sperm delivered mRNA has also been hythesized to be necessary for embryogenesis. There is less information about the epigenetic factors affecting embryogenesis than genetic factors, but the epigenetics of gamete and early embryogenesis is a rapidly advancing field