Is there a relationship between sperm chromosome abnormalities and sperm morphology?

This review explores the relationship between sperm chromosomal constitution and morphology. With the advent of techniques for obtaining information on the chromosome complements of spermatozoa, this relationship has been studied in fertile men and in men with a high frequency of chromosomal abnormalities. Using human sperm karyotype analysis, no relationship between sperm chromosome abnormalities and morphology was found in fertile men, translocation carriers or post-radiotherapy cancer patients. Fluorescence in situ hybridization (FISH) analysis has not generally revealed a specific association between morphologically abnormal sperm and sperm chromosome abnormalities, but has indicated that teratozoospermia, like other forms of abnormal semen profiles (aesthenozoospermia, oligozoospermia) is associated with a modest increase in the frequency of sperm chromosome abnormalities. However, FISH studies on some infertile men and mouse strains have suggested that certain types of morphologically abnormal spermatozoa, such as macrocephalic multitailed spermatozoa, are associated with a very significantly increased frequency of aneuploidy. Thus, there may be an association between sperm morphology and aneuploidy in infertile men with specific abnormalities.     

Porcine oviduct sperm binding glycoprotein and its deleterious effect on sperm: a mechanism for negative selection of sperm?

In their journey through the oviduct some subpopulations of sperm are preserved in a reservoir, while others are negatively selected. Sperm binding glycoprotein (SBG) is a pig oviductal epithelial cell glycoprotein that produces, under capacitating conditions, acrosome alteration, p97 tyrosine-phosphorylation and reduction of the motility of sperm. In this paper, we show that SBG is accessible at the extracellular surface of the oviductal epithelial cells, supporting a sperm interaction biological role in situ. We analyze the possible dependence of the tyrosine-phosphorylation of p97 on the PKA mechanism, finding that apparently it is not PKA dependent. Also, after SBG treatment the phosphorylated proteins locate mainly at the detached periacrosomal region and at the tail of sperm; the latter may be related to SBG's motility reduction effect. The study of the time course effect of SBG on sperm as detected by chlortetracycline (CTC) staining and of its binding to sperm by immunodetection in conjunction with CTC, shows results in agreement with the hypothesis that this glycoprotein is involved in the alteration of acrosomes in a specific sperm subpopulation. The results suggest that SBG may be part of a mechanism for negative selection of sperm.     

Is the hook of muroid rodent's sperm related to sperm train formation?

Competition between spermatozoa of rival males to gain fertilizations has led to a wide array of modifications in sperm structure and function. Sperm cells of most muroid rodents have hook‐shaped extensions in the apical–ventral tip of the head, but the function of this structure is largely unknown. These ‘hooks’ may facilitate aggregation of spermatozoa in so‐called ‘trains’, as an adaptation to sperm competition, because sperm in trains may swim faster than free‐swimming cells. However, there is controversy regarding the role of the hook in train formation, and in relation to whether it is selected by sperm competition. We examined spermatozoa from muroid rodents with varying levels of sperm competition to assess whether (i) sperm aggregates are common in these taxa, (ii) presence of a hook relates to the formation of sperm aggregations, and (iii) formation of sperm aggregations is explained by sperm competition. Our analyses in 25 muroid species revealed that > 92% of spermatozoa swim individually in all species, with the exception of the wood mouse, Apodemus sylvaticus, which has ~50% spermatozoa swimming freely. Species with hooked spermatozoa had higher sperm competition levels and longer sperm than species whose sperm lack a hook. Neither the presence of hook nor sperm competition levels were related to the percentage of sperm in aggregations. Thus, (i) sperm aggregates in muroid rodents are an exceptional trait found only in a few species, (ii) evolution of the sperm hook is associated to sperm competition levels, but (iii) the hook is unlikely to be related to the formation of sperm aggregates. The evolutionary significance of the sperm head hook thus remains elusive, and future studies should examine potential roles of this pervasive structure in sperm's hydrodynamic efficiency and sperm–female tract interactions.     

Effects of cytoplasmic genes on sperm viability and sperm morphology in a seed beetle: implications for sperm competition theory?

Sperm competition theory predicts that sperm traits influencing male fertilizing ability will evolve adaptively. However, it has been suggested that some sperm traits may be at least partly encoded by mitochondrial genes. If true, this may constrain the adaptive evolution of such traits because mitochondrial DNA (mtDNA) is maternally inherited and there is thus no selection on mtDNA in males. Phenotypic variation in such traits may nevertheless be high because mutations in mtDNA that have deleterious effects on male traits, but neutral or beneficial effects in females, may be maintained by random processes or selection in females. We used backcrossing to create introgression lines of seed beetles (Callosobruchus maculatus), carrying orthogonal combinations of distinct lineages of cytoplasmic and nuclear genes, and then assayed sperm viability and sperm length in all lines. We found sizeable cytoplasmic effects on both sperm traits and our analyses also suggested that the cytoplasmic effects varied across nuclear genetic backgrounds. We discuss some potential implications of these findings for sperm competition theory.     

Do "sperm trading" simultaneous hermaphrodites always trade sperm?

Sperm trading can be a mechanism to solve the conflict oversex roles in hermaphrodites with copulation, sperm competition,and sperm digestion. If present, sperm donation depends on spermreceipt, resulting in conditional reciprocal inseminations.Conditional reciprocity can involve three traded commodities:penis intromissions on a yes-or-no basis, intromission durations(indicating ejaculate size), or sperm transfer. If present,animals that refuse to donate (cheaters) should be desertedby their partner or receive smaller ejaculates. We tested whetherany of these commodities is traded in the simultaneously hermaphroditicsea slug, Chelidonura sandrana. Matings involve a stereotypicsingle sex role alternation. As a result, reciprocity was morefrequent than expected under random mating, supporting tradingof penis intromissions. Contrary to the predictions under tradingof ejaculate sizes, intromission durations were not balancedbetween mating partners. To test trading of sperm transfer itself,we interrupted the sperm groove that transports sperm into thepenis during copulation. Treated animals (experimental cheaters)could still copulate normally but could not transfer sperm.When paired to a cheater, sham-treated control animals did notrespond to the absence of sperm receipt, neither by desertionnor by shortening intromission. We thus reject trading of inseminationdurations and sperm transfer in C. sandrana. Although tradingof intromissions may be present, we discuss why reciprocityin this species may also be a by-product of the mutual willingnessof both partners to donate as well as receive sperm, and notan indicator of sperm trading.     

Inhibiting sperm motility for male contraception: will the sperm tail be its "Achilles heel"?

Blocking sperm motility has great appeal as a male contraceptive. A drug that targets sperm motility might have a very rapid onset of action, possibly allowing for administration immediately prior to intercourse and minimizing concerns about compliance. Promising sperm motility targets include transmembrane calcium channels, a unique adenylyl cyclase, and novel flagellar proteins. Future efforts directed towards effectively antagonizing the activities of these or other such targets will be required to completely impair sperm production, function, or both and create a usable male "pill."     

What women want in their sperm donor: A study of more than 1000 women’s sperm donor selections

Reproductive medicine and commercial sperm banking have facilitated an evolutionary shift in how women are able to choose who fathers their offspring, by notionally expanding women’s opportunity set beyond former constraints. This study analyses 1546 individual reservations of semen by women from a private Australian assisted reproductive health facility across a ten year period from 2006 to 2015. Using the time that each sample was available at the facility until reservation, we explore women’s preference for particular male characteristics. We find that younger donors, and those who hold a higher formal education compared to those with no academic qualifications are more quickly selected for reservation by women. Both age and education as proxies for resources are at the centre of Parental Investment theory, and our findings further build on this standard evolutionary construct in relation to female mate preferences. Reproductive medicine not only provides women the opportunity to become a parent, where previously they would not have been able to, it also reveals that female preference for resources of their potential mate (sperm donor) remain, even when the notion of paternal investment becomes redundant. These findings build on behavioural science’s understanding of large-scale decisions and human behaviour in reproductive medical settings.     

The physiological acquisition of amoeboid motility in nematode sperm: Is the tail the only thing the sperm lost?

Nematode spermatozoa are highly specialized amoeboid cells that must acquire motility through the extension of a single pseudopod. Despite morphological and molecular differences with flagellated spermatozoa (including a non‐actin‐based cytoskeleton), nematode sperm must also respond to cues present in the female reproductive tract that render them motile, thereby allowing them to locate and fertilize the egg. The factors that trigger pseudopod extension in vivo are unknown, although current models suggest the activation through proteases acting on the sperm surface resulting in a myriad of biochemical, physiological, and morphological changes. Compelling evidence shows that pseudopod extension is under the regulation of physiological events also observed in other eukaryotic cells (including flagellated sperm) that involve membrane rearrangements in response to extracellular cues that initiate various signal transduction pathways. An integrative approach to the study of nonflagellated spermatozoa will shed light on the identification of unique and conserved processes during fertilization among different taxa. Mol. Reprod. Dev. 77: 739–750, 2010. © 2010 Wiley‐Liss, Inc.     

Identification of sperm morphometric subpopulations in the canine ejaculate: do they reflect different subpopulations in sperm chromatin integrity?

A statistical approach using sequentially principal component analysis (PCA) clustering and discriminant analysis was developed to disclose morphometric sperm subpopulations. In addition, we used a similar approach to disclose subpopulations of spermatozoa with different degrees of DNA fragmentation. It is widely accepted that sperm morphology is a strong indicator of semen quality and since the sperm head mainly comprises the sperm DNA, it has been proposed that subtle changes in sperm head morphology may be related to abnormal DNA content. Semen from four mongrel dogs (five replicates per dog) were used to investigate DNA quality by means of the sperm chromatin structure assay (SCSA), and for computerized sperm morphometry (ASMA). Each sperm head was measured for nine primary parameters: head area (A), head perimeter (P), head length (L), head width (W), acrosome area (%), midpiece width (w), midpiece area (a), distance (d) between the major axes of the head and midpiece, angle (theta) of divergence of the midpiece from the head axis; and four parameters of head shape: FUN1 (L/W), FUN2 (4pi A/P2), FUN3 ((L - W)/(L + W)) and FUN 4 (pi LW/4A). The data matrix consisted of 2361 observations, (morphometric analysis on individual spermatozoa) and 63,815 observations for the DNA integrity. The PCA analysis revealed five variables with Eigen values over 1, representing more than 79% of the cumulative variance. The morphometric data revealed five sperm subpopulations, while the DNA data gave six subpopulations of spermatozoa with different DNA integrity. Significant differences were found in the percentage of spermatozoa falling in each cluster among dogs (p < 0.05). Linear regression models including sperm head shape factors 2, 3 and 4 predicted the amount of denatured DNA within each individual spermatozoon (p < 0.001). We conclude that the ASMA analysis can be considered a powerful tool to improve the spermiogram.     

SpermBlue®: A new universal stain for human and animal sperm which is also amenable to automated sperm morphology analysis

Abstract

Our study was aimed at exploring a simple procedure to stain differentially the acrosome, head, midpiece, and flagellum of human and animal sperm. A further prerequisite was that sperm morphology of the stained samples could be analyzed using automated sperm morphology analysis (ASMA). We developed a new staining process using SpermBlue® fixative and SpermBlue® stain, which are iso-osmotic in relation to semen. The entire fixation and staining processes requires only 25 min. Three main steps are required. First, a routine sperm smear is made by either using semen or sperm in a diluting medium. The smear is allowed to air dry at room temperature. Second, the smear is fixed for 10 min by either placing the slide with the dried smear in a staining tray containing SpermBlue® fixative or by adding 1 ml SpermBlue® fixative to the slide. Third, the fixed smear is stained for 15 min by either immersing the slide in a staining tray containing SpermBlue® stain or adding four drops of SpermBlue® stain to the fixed smear. The stained slide is dipped gently in distilled water followed by air drying and mounting in DPX® or an equivalent medium. The method is simple and suitable for field conditions. Sperm of human, three monkey species, horse, boar, bull, ram, mouse, rat, domestic chicken, fish, and invertebrate species were stained successfully using the SpermBlue® staining process. SpermBlue® stains human and animal sperm different hues or intensities of blue. It is possible to distinguish clearly the acrosome, sperm head, midpiece, principal piece of the tail, and even the short end piece. The Sperm Class Analyzer® ASMA system was used successfully to quantify sperm head and midpiece measurements automatically at either 600 × or 1000 × magnification for most of the species studied.     

Liposome‐mediated DNA transfer to chicken sperm cells

Abstract

The efficacy of using liposomes to transfer DNA to chicken sperm cells was investigated. Liposomes were prepared from dilauroyl (12:0) phosphatidylcholine (DLPC), dimyristoyl (14:0) phosphatidyl choline (DMPC), dipalmitoyl (16:0) phosphatidylcholine (DPPC), egg yolk phosphatidylcholine (EYPC) or lipids extracted from sperm cell membranes. The efficiency of trapping of DNA into the liposomes, transfer of the DNA from the liposomes to the sperm cells and the effect of the liposomes on the fertilizing ability of the sperm cells were determined. Increasing the concentration of lipid in the liposome preparations increased the trapping efficiency of DNA into liposomes but lowered the transfer of DNA to sperm. Including stearylamine (SA) in the liposomes increased the incorporation of DNA into the liposomes and the DNA transfer to sperm cells, while including lauroyllysophosphatidylcholine (LPC) along with SA resulted in the highest transfer efficiency from liposomes to sperm. The transfer of DNA from liposomes to sperm cells was lowered by increasing the number of sperm cells, while decreasing the number of sperm cells lowered the fertility. The sperm cells remained fertile after exposure to low levels of DPPC or lipofectin reagent or to high levels of SA and LPC. The best conditions for liposome‐mediated gene transfer to chicken sperm cells are thus using either lipofectin reagent at .006 to .06 μmol/ml and 5 × 10⁷ sperm or with DPPC liposomes comprised of 10 μmol/ml total lipid including 5 mol% SA and 20 mol% LPC with 2.5 × 10⁸ sperm cells. The use of liposomes to enhance the transfer of DNA to sperm cells may make the use of sperm cells as gene transfer vectors possible.     

Pollen and sperm heteromorphism: convergence across kingdoms?

Sperm competition theory predicts that males should produce many, similar sperm. However, in some species of animals and plants, males exhibit a heteromorphism that results in the production of at least two different types of sperm or pollen grains. In animals, sperm heteromorphism typically corresponds to the production of one fertile morph and one (or more) sterile morph(s), whereas in plants two or more pollen morphs (one of which can be either sterile or fertile) are produced in all flowers but sometimes in different anthers. Heteromorphism has arisen independently several times across phyla and at different phylogenetic levels. Here, we compare and contrast sperm and pollen heteromorphism and discuss the evolutionary hypotheses suggested to explain heteromorphism in these taxa. These hypotheses include facilitation, nutritive contribution, blocking, cheap filler, sperm flushing or killing for animals; outcrossing and precise cross-pollen transfer or bet-hedging strategy for plants; cryptic female choice for both. We conclude that heteromorphism in the two phyla is most likely linked to a general evolutionary response to sexual selection, either to increase one male's sperm or pollen success in competition with other males, or mediate male/female interactions. Therefore, although sperm and pollen are not homologous, we suggest that heteromorphism represents an example of convergence across kingdoms.     

Trypanosomes and mammalian sperm: one of a kind?

Flagellar-mediated motility is an indispensable function for cell types as evolutionarily distant as mammalian sperm and kinetoplastid parasites, a large group of flagellated protozoa that includes several important human pathogens. Despite the obvious importance of flagellar motility, little is known about the signalling processes that direct the frequency and wave shape of the flagellar beat, or those that provide the motile cell with the necessary environmental cues that enable it to aim its movement. Similarly, the energetics of the flagellar beat and the problem of a sufficient ATP supply along the entire length of the beating flagellum remain to be explored. Recent proteome projects studying the flagella of mammalian sperm and kinetoplastid parasites have provided important information and have indicated a surprising degree of similarities between the flagella of these two cell types.     

In cryptozoospermia or severe oligozoospermia is sperm freezing useful?

Background

Intracytoplasmic Sperm Injection (ICSI) is an Assisted Reproduction Technique (ART) which offers the chance to conceive to patients presenting very low sperm counts (cryptozoospermia/severe oligozoospermia). Sperm freezing before the oocyte pick-up, can prevent from a lack of spermatozoa on the day of the ICSI. It can avoid the cancellation of the ICSI or the use of TESE (Testicular sperm extraction). The objective of this study was to analyse the practice of sperm freezing for these patients in our center over 8 years and the rate of use of these frozen sperms. We also compared the outcome of ICSIs with frozen versus ejaculated sperm.

Material and methods

We performed a retrospective epidemiological study between 2004 and 2011. We recruited all the patients having a sperm count below 1 Million/mL and who were waiting for their first ICSI attempt.

Results

169 patients were recruited: 84 cryopreserved their sperm before the ICSI (secured ICSI) while 85 did not (non-secured ICSI). Both groups were split in cryptozoospermia (<10³ spermatozoa/ml): 19 and 17 patients respectively, very severe oligozoospermia (10³–10⁵/ml): 37 and 13 patients, and severe oligozoospermia (10⁵–10⁶/ml): 28 and 55 patients. The part of secured ICSI significantly increased from 29% during 2004–2007 to 74% during 2008–2011(p?=?0.0029) and the frozen sperm was used in 5.9% of the cases. Median age was significantly higher in the non secured ICSI group (33.57 vs 35.52 for men, p?=?0.0069 and 30.45 vs 32.26 for women, p?=?0.025) but no significant difference was found in the outcome of the ICSI between frozen-thawed sperm and fresh ejaculated sperm.

Conclusion

Sperm freezing before ICSI for severe oligozoospermic and cryptozoospermic patients significantly increased in our practice but the rate of use remain very low. This encourages to define more accurate criteria leading to sperm freezing.