The general program of the 7th International Symposium on Spermatology held in Cairns, Australia from October 9-14, 1994 included the following sessions: Genetics of Sperm; Sperm Development; Sperm Morphology and Competition; Advances in Spermatozoal Taxonomy and Phylogeny; Enviromental Spermatology; Human Applied Spermatology; Sperm Movement; Animal Applied Spermatology; Gamete Recognition and Coral Reef Spawning. In addition 3 mid-day workshops completed the list of topics: 1) Advanced Techniques in Sperm Preparation and imaging; 2) Reactive Oxygen Species (ROS) in Semen; and 3) Clinical CASA: the Quest for a Consensus. The following are some of the highlights of the program.
Dr. D. Wolgemuth (USA) updated our knowledge on the genetic regulation of the mammalian spermatogenic cell-cycle. In the last two years work has focused on identifying a number of maturation promoting factors, cyclins (A,B,C, D..H... and their subgroups A1,2, B1,2, etc.) and cyclins dependent kinases (CDKs), involved in the fine regulation of cellular replicative-cycles. Interestingly, from data gathered in mice, each cyclin has a specific site of action during the spermatogenic cycle.
For example, cyclin A is important at G2 phase, with A1 expressed in late pachytene and diplotene and A2 in spermatogonium and in the preleptotene stage. It seems that A2 is expressed only during the early stage of life (day 7 for mice) but not in adult testis. Cyclin B1 is expressed in the early spermatid/round spermatids, while B2 is expressed in pachytene spermatocytes. Cyclins are also located in oocytes and surrounding granulosa cells. The lack of cyclins or presence of mutations in cyclins may alter the spermatogenic cycle and thus render the mouse sterile. In the near future, active ongoing research in this area will identify the precise substrate and the specific stages of meiosis and differentiation where cyclins and CDKs are activein both male and female gametes.
Dr. P. Vogt (Germany) presented an overview of mutations identified on the human Y chromosome linked to azoospermia and to severe oligospermia. These mutations could be classified as interstitial microdeletions mapped to three different subregions of the long arm of chromosome Y. Different phenotypes may thus reflect different genotypes. These mutations were found with a frequency of 5-20% in idiopathic sterile males with azoospermia or severe oligospermia.
Dr. G. Schatten (USA), in a very elegant lecture, illustrated sperm contribution during the process of fertilization. In humans, at the time of fertilization, sperm introduce the centrosome along with the nucleus. The centrosome is the organizer for the activity of the microtubules to allow the two nuclei (sperm and oocyte) to come close together. During interphase the centrosome divides and forms the two spindle poles for the first mitosis. Some cases of male infertility may be due to defective sperm centrosome function. These cases would not be detected until the sperm enters the egg. In order to evaluate the sperm centrosome activity in vitro, Dr. Schatten proposed the development of an assay formed by cell free egg-extract from Xenopus. This assay, if validated, could become an important additional test for male infertility, as has been the hamster penetration test.
Dr. B. Jégou (France) gave a lecture entitled Sertoli and Germ Cells Cross-Talk. There are three distinct pathways of communication: a) by soluble chemical factors; b) by anatomical devices (membrane molecules, adhesion molecules, CAMs, LRP) and morphoregulatory proteins; and c) by transfer of material. Mechanisms of dialogue between late spermatids and Sertoli cells are very interesting: the late spermatids transfer residual bodies in the Sertoli cell at the time of spermiation; these residual bodies undergo phagocytosis by the Sertoli cells. In rats, the incubation of Sertoli cells with residual bodies triggers the production of interleukin 1 (IL-1) and this, in turn, stimulates the production of IL-6. Currently, work is in progress to delineate the metabolic functions of IL-1 and especially IL-6. It is speculated that IL-1 in humans may stimulate the spermatogonial division and the meiotic and mitotic process in vitro. The action of IL-6 is less clear, although it is thought to inhibit germ cell DNA replication.
Dr. A. Wyrobek (USA) presented male reproductive toxicology and heritable effect and discussed the incidence of aneuploidy in ejaculated sperm. After evaluating 10,000 sperm by using FISH, he found that 3% had hyperhaploidy (XX, YY, or XY) and that 80% of the XO cases are paternally derived and 50% of the XXY are also paternally derived. The incidence of aneuploidy in human sperm rises when chemotherapy is given; in patients with HodgkinÕs disease, Dr. Wyrobek found a high number of chromosomally defective sperm. In some men, he reported a stable elevation of aneuploidy frequencies for a particular chromosome. Looking specifically at chromosomes 1, 8, X, and Y he found that the incidence of aneuploidy in the normal population is between 3 to 30 chromosomes over the 10,000 studied. However, in the ejaculate of men after chemotherapy, this incidence rose 5 to 10 times, including cases of hyperploidy XY which produces the Klinefelter syndrome (XXY).
Dr. M. Payne (Australia) presented data on microassisted fertilization. Since the advent of intracytoplasmic sperm injection (ICSI), this Australian group has performed the procedure on 3800 oocytes, reporting a fertilization rate (defined as presence of 2 PN) of 65%. The cleavage rate has been 80%, the pregnancy rate 32% and the abortion rate about 20%. When ICSI was used in cases where only occasional motile sperm were present, the fertilization rate of 65% was maintained and the pregnancy rate was 31%. The use of ICSI with epididymal sperm produced a 70% fertilization rate, but a 25% pregnancy rate. P. Patrizio (USA) presented a summary on the use of epididymal sperm in assisted reproduction. After 200 cycles of microsurgical epididymal sperm aspiration (MESA), it is clear that epididymal sperm of men with congenital absence of the vas deferens (CAVD) have a poor in vitro fertilization rate capacity and most likely this is a reflection either of intrinsic biochemical defects or alteration of the epididymal milieu due to cystic fibrosis mutations. On the other hand, epididymal sperm of men with other kinds of obstructive azoospermia, i.e. vasectomy reversal, ejaculatory ducts obstruction, inflammatory epididymal blockage, have a much higher rate of fertilization. In the first instance, men with CAVD, the fertilization rate without ICSI is only 13%, while in men with acquired obstructions, it is 42% and this may be the real fertilizing capacity of human epididymal sperm. With ICSI, it is possible to improve significantly the fertilization rate of sperm from men with CAVD up to 40%, while there was no improvement with epididymal sperm from men with other kinds of obstruction. Finally, it was demonstrated that the mRNA coding for the protein coded by the cystic fibrosis gene is highly expressed in the cells of the columnar epithelium of the human epididymis, thus supporting the observation that its absence or alteration may affect the IVF capacity (nonmicroassisted) of sperm from men with CAVD.
Dr. J. Cummins (Australia) presented a work entitled Human Male Infertility and Mitochondrial DNA. Mitochondrial DNA is maternally inherited and the mitochondrial function depends on both nuclear and mitochondrial gene products. Mitochondrial DNA is very susceptible to point mutations or deletions and does not contain mechanisms able to repair damages. An injury to the mitochondrial DNA might disrupt the electron transport and, thus, create a dangerous and untimely accumulation of ROS and free radicals. By studying mitochondrial DNA from the testicular biopsies and the semen of 5 young infertile men, he found high levels of minor mutations in testis biopsies similar to those found in advanced age. In addition, he found 3 major deletions commonly associated with mitochondrial disease. Thus, some forms of male infertility may be due to maternal inheritance of defective mitochondrial DNA.
Dr. B. Hinton (USA) discussed the epididymis as a protector of maturing sperm. There are some epididymal proteins that protect sperm from oxidative stress. These enzymes are: a) superoxide dismutase and catalase; b) glutathione S-transferase, peroxidase reductase and glutathione gamma-glutamyl transpeptidase (GGT). The enzyme GGT was discussed in detail. It is present in the epididymal luminal fluid and in the apical cell surface; it is more expressed in the caput-corpus portion than the cauda and has high affinity for oxidized glutathione compared to reduced glutathione. The existence of multiple GGT mRNA has been demonstrated and this may reflect the presence of multiple genes for GGT or variable length of polyadenylate or alternative splicing or transcription from different promoters.
Dr. S. Flaherty (Australia) discussed the ratio of X to Y bearing sperm in samples isolated using two different sperm separation techniques and in men with children of one sex. The two sperm separation techniques were the albumin gradient method used for male sex preselection and the modified swim-up procedure used for female sex preselection. A double label FISH technique (identify X and Y simultaneously) was used for checking the separation results. Surprisingly, the results demonstrated that albumin gradients do not enrich Y-bearing sperm and the modified swim-up procedure does not isolate X-bearing sperm, thus alternative explanations must be sought to justify altered sex ratios reported by using these two techniques. Curiously, men who fathered children of one sex, were not found to have an altered ratio of X and Y bearing sperm.
The meeting was attended by 350 registrants from many countries. The organization by J. Cummins, A. Jequier and M. Bradley was excellent. The next Spermatology Symposium is planned for Montreal in 1998 under the organization of C. Gagnon.
Pasquale Patrizio, USA