The partial head decondensation test is a new, quick method to assess acrosome status in human spermatozoa

Effects of disulfide bond reducing agents on sperm chromatin structural integrity and developmental competence of in vitro matured oocytes after intracytoplasmic sperm injection in pigs

We recently reported that electrical activation followed by secondary chemical activation greatly enhanced the developmental competence of in vitro matured porcine oocytes fertilized by intracytoplasmic sperm injection (ICSI). We hypothesized that sperm treatment with disulfide bond reducing agents will enhance the development competence of porcine embryos produced by this ICSI procedure. We examined the effects of glutathione (GSH), dithiothreitol (DTT), GSH or DTT in combination with heparin on sperm DNA structure, paternal chromosomal integrity, pronuclear formation, and developmental competence of in vitro matured porcine oocytes after ICSI. Acridine orange staining and flow cytometry based sperm chromatin structure assay were used to determine sperm DNA integrity by calculating the cells outside the main population (COMP alphaT). No differences were observed in COMP alphaT values among GSH-treated and control groups. COMP alphaT values in GSH-treated groups were significantly lower than that in DTT-treated groups. Following ICSI, GSH treatments did not significantly alter paternal chromosomal integrity. Paternal chromosomal integrity in sperm treated with DTT plus or minus heparin was also the lowest among all groups. GSH-treated sperm yielded the highest rates of normal fertilization and blastocyst formation, which were significantly higher than that of control and DTT-treated groups. The majority of blastocysts derived from control and GSH-treated spermatozoa were diploid, whereas blastocysts derived from DTT-treated spermatozoa were haploid. In conclusion, sperm treatment with GSH enhanced the developmental capacity of porcine embryos produced by our optimized ICSI procedure.

Evaluation of acrosomal status and sperm viability in fresh and cryopreserved specimens by the use of fluorescent peanut agglutinin lectin in conjunction with hypo-osmotic swelling test

OBJECTIVE

In this study, we evaluated whether the hypo-osmotic swelling test (HOST) can be used as a vital marker in combination with peanut agglutinin (PNA) - labeling in fresh and cryopreserved spermatozoa.

MATERIALS AND METHODS

Human sperm populations were exposed to a hypo-osmotic medium for 60 minutes, and then incubated in a 1 microg/mL solution of the fluorescent dye Hoescht 33258 (H33258) for 10 minutes. Excess stain was removed by washing in phosphate-buffered saline (PBS) solution, and the pellet was resuspended in 100 microL of culture medium. Twenty microliters of this solution were subsequently smeared on a microscope slide, and fixed in ice-cold methanol to permeabilize the sperm membranes. The fixed smears were finally incubated in a 40-microg/mL FITC-PNA solution for 20 minutes. Simultaneous assessment of acrosome and viability scores was done in a fluorescent microscope equipped with appropriate filters and phase contrast illumination. The same slide was examined for FITC-PNA labeling, tail swelling, and for Hoechst-33258 staining by interchanging the filters and phase contrast optics.

RESULTS

In fresh specimens, HOST was found to provide viability assessments comparable to those obtained using the H33258 method (r = 0.95). However, the results of HOST and H33258 were not correlated in cryopreserved specimens (r = 0.22). There was no alteration of PNA-labeling due to the HOST or H33258.

CONCLUSIONS

FITC-PNA labeling in conjunction with the visualization of the morphological change induced by exposure to hypo-osmotic solution provides a simple but effective method for establishing the state of acrosomal membrane and viability in fresh human spermatozoa, but this technique is not reliable for cryopreserved ones.

Protamines and male infertility

Protamines are the major nuclear sperm proteins. The human sperm nucleus contains two types of protamine: protamine 1 (P1) encoded by a single-copy gene and the family of protamine 2 (P2) proteins (P2, P3 and P4), all also encoded by a single gene that is transcribed and translated into a precursor protein. The protamines were discovered more than a century ago, but their function is not yet fully understood. In fact, different hypotheses have been proposed: condensation of the sperm nucleus into a compact hydrodynamic shape, protection of the genetic message delivered by the spermatozoa, involvement in the processes maintaining the integrity and repair of DNA during or after the nucleohistone-nucleoprotamine transition and involvement in the epigenetic imprinting of the spermatozoa. Protamines are also one of the most variable proteins found in nature, with data supporting a positive Darwinian selection. Changes in the expression of P1 and P2 protamines have been found to be associated with infertility in man. Mutations in the protamine genes have also been found in some infertile patients. Transgenic mice defective in the expression of protamines also present several structural defects in the sperm nucleus and have variable degrees of infertility. There is also evidence that altered levels of protamines may result in an increased susceptibility to injury in the spermatozoan DNA causing infertility or poor outcomes in assisted reproduction. The present work reviews the articles published to date on the relationship between protamines and infertility.

Risk assessment of chemicals potentially affecting male fertility

Male reproductive toxicity involves a broad range of targets and mechanisms such as direct effects on the seminiferous epithelium and/or on Leydig and Sertoli cells supporting spermatogenesis, epididymal sperm maturation as well as endocrine disruption. Direct effects on spermatogenesis may be adequately revealed through both reproduction and repeated-dose toxicity studies; however, more research is needed on early markers of effect and on long-term sequelae of short-term exposures. Endocrine-related mechanisms are particularly relevant to subtle, but persistent effects on reproductive development due to altered early programming; the two-generation study is the test of choice, whereas targeted studies on the prepubertal phase are also desirable. Studies using in vitro methods as well as toxicogenomics are increasing; although gaps exist and much validation work is needed, in perspective, such approaches may be important in order to select compound, understand mechanisms, as well identify biomarkers of potential use also in human studies.