Results of intracytoplasmic sperm injection in two infertile patients with abnormal organization of sperm mitochondrial sheaths and severe asthenoteratozoospermia

High percentage of midpiece defects in Brangus bull sperm with no reduction in sperm kinematics

The study investigated midpiece defects in sperm from a 5-year-old Brangus bull with a high rate of semen batch rejection, due to morphologically abnormal sperm, with no reduction in sperm kinematics. A comprehensive evaluation was conducted over a 16-month period, involving 28 ejaculates. Notably, despite the high proportion of midpiece defects (average 37.73%, from 3% to 58%), the study revealed stable sperm production, with no discernible differences in the kinematic data before and after cryopreservation. Electron microscopy identified discontinuities in the mitochondrial sheath, characteristic of midpiece aplasia (MPA). The anomalies were attributed to be of genetic origin, as other predisposing factors were absent. Additionally, the electron microscopy unveiled plasma membrane defects, vacuoles and chromatin decondensation, consistent with previous findings linking acrosome abnormalities with midpiece defects. The findings underscored the necessity of conducting thorough laboratory evaluations before releasing cryopreserved semen for commercialization. Despite substantial morphological alterations, the initial semen evaluation data indicated acceptable levels of sperm kinematics, emphasizing the resilience of sperm production to severe morphological changes. This case report serves as a contribution to the understanding of midpiece defects in bull sperm, emphasizing the need for meticulous evaluation and quality control in semen processing and commercialization.

Equilibration time improves the sperm variables of wild ruminant ejaculated and epididymal sperm cryopreserved by ultra-rapid freezing

This work examines the effect of equilibration time with extender on ultra-rapidly frozen-thawed wild ruminant epididymal (origin: Iberian ibex) and ejaculated (origin: mouflon) sperm variables. Sperm samples were prepared either without prior equilibration, or equilibrated for 30 min before freezing. Higher quality (p < 0.05) frozen-thawed spermatozoa were obtained when equilibration was allowed, for ejaculated sperm in terms of sperm motility, acrosome apical ridge integrity, sperm viability, and percentage of normal cells, and for epididymal sperm in terms of linearity and straightness of sperm movement. The sperm head area, head perimeter, head length and head width were smaller (p < 0.01) in the equilibrated than non-equilibrated frozen-thawed epididymal sperm; no such dimensional changes were recorded for ejaculated sperm. In conclusion, equilibration prior to ultra-rapid freezing improves the cryoresistance of sperm cells, although viable sperm cells can be obtained without equilibration. The epididymal sperm showed greater cryoresistance, supporting the idea that it is more resistant to freeze-thawing than ejaculated sperm.

Biallelic mutations in ARMC12 cause asthenozoospermia and multiple midpiece defects in humans and mice

BACKGROUND

Asthenozoospermia is a major factor contributing to male infertility. The mitochondrial sheath (MS), an important organelle in the midpiece of spermatozoa, is crucial to sperm motility. ARMC12 is a mitochondrial peripheral membrane protein. Deletion of Armc12 impairs the arrangement of MS and causes infertility in mice. However, the role of ARMC12 in human asthenozoospermia remains unknown.

OBJECTIVE

To study the genetic defects in patients with asthenozoospermia.

METHODS

A total of 125 patients with asthenozoospermia and 120 men with proven fertility were recruited. Whole-exome sequencing and Sanger sequencing were performed for genetic analysis. Papanicolaou staining, HE staining, immunofluorescent staining, transmission electron microscopy and field emission scanning electron microscopy were employed to observe the morphological and structural defects of the spermatozoa and testes. Armc12-knockout mice were generated using the CRISPR-Cas9 system. Intracytoplasmic sperm injection was used to treat the patients.

RESULTS

Biallelic ARMC12 mutations were identified in three patients, including homozygous mutations in two siblings from a consanguineous family and compound heterozygous mutations in one sporadic patient. ARMC12 is mainly expressed in the midpiece of elongated and late spermatids in the human testis. The patients' spermatozoa displayed multiple midpiece defects, including absent MS and central pair, scattered or forked axoneme and incomplete plasma membrane. Spermatozoa from Armc12^-/- mice showed parallel defects in the midpiece. Moreover, two patients were treated with intracytoplasmic sperm injection and achieved good outcomes.

CONCLUSION

Our findings prove for the first time that defects in ARMC12 cause asthenozoospermia and multiple midpiece defects in humans.

Bi-allelic variants in DNHD1 cause flagellar axoneme defects and asthenoteratozoospermia in humans and mice

Asthenoteratozoospermia, defined as reduced sperm motility and abnormal sperm morphology, is a disorder with considerable genetic heterogeneity. Although previous studies have identified several asthenoteratozoospermia-associated genes, the etiology remains unknown for the majority of affected men. Here, we performed whole-exome sequencing on 497 unrelated men with asthenoteratozoospermia and identified DNHD1 bi-allelic variants from eight families (1.6%). All detected variants were predicted to be deleterious via multiple bioinformatics tools. Hematoxylin and eosin (H&E) staining revealed that individuals with bi-allelic DNHD1 variants presented striking abnormalities of the flagella; transmission electron microscopy (TEM) further showed flagellar axoneme defects, including central pair microtubule (CP) deficiency and mitochondrial sheath (MS) malformations. In sperm from fertile men, DNHD1 was localized to the entire flagella of the normal sperm; however, it was nearly absent in the flagella of men with bi-allelic DNHD1 variants. Moreover, abundance of the CP markers SPAG6 and SPEF2 was significantly reduced in spermatozoa from men harboring bi-allelic DNHD1 variants. In addition, Dnhd1 knockout male mice (Dnhd1^‒/‒) exhibited asthenoteratozoospermia and infertility, a finding consistent with the sperm phenotypes present in human subjects with DNHD1 variants. The female partners of four out of seven men who underwent intracytoplasmic sperm injection therapy subsequently became pregnant. In conclusion, our study showed that bi-allelic DNHD1 variants cause asthenoteratozoospermia, a finding that provides crucial insights into the biological underpinnings of this disorder and should assist with counseling of affected individuals.

Evaluation of Microscopic, Flow Cytometric, and Oxidative Parameters of the Frozen-Thawed Bull Sperm in a Freezing Extender Containing Myo-Inositol

Introduction: This research was conducted to assess the effect of myo-inositol (MYO) in the freezing extender on the semen quality and oxidative stress parameters of frozen-thawed bull sperm. Materials and Methods: Semen samples were obtained from four bulls (n = 24, six ejaculates per bull), twice a week, and diluted into four equal aliquots in freezing extenders containing different concentrations of MYO (0, 2, 3, and 4 mg/mL). After a freezing/thawing process, velocity parameters, plasma membrane integrity, apoptosis status, malondialdehyde level, and oxidative stress parameters were assessed. Results: Supplementation of freezing extender with 3 mg/mL MYO resulted in higher rapid motility (62.22% ± 2.63%), progressive motility (77.45% ± 2.65%), viability (78% ± 0.91%), plasma membrane integrity (86 ± 0.85), catalase (20.03 ± 0.39 U/mL) activity, and lower significance of lipid peroxidation (3.60 ± 0.15 nmol/dL) than those of the control group (p < 0.05). A significantly lower percentage of normal morphology and intact acrosomes were observed for frozen-thawed semen in the extender supplemented with 4 mg/mL MYO than those of the control group (p < 0.05). Freezing of the sperm in the extender containing 3 mg/mL of MYO leads to a higher percentage of live cells (38.3 ± 2.76). Beat-cross-frequency, amplitude of lateral head displacement, linearity, total antioxidant capacity, total peroxidase activity, early apoptotic status, and superoxide dismutase activities were not affected by MYO levels in the extenders (p > 0.05). Conclusion: The findings of this study suggest that the supplementation of the freezing extender with 3 mg/mL MYO resulted in a higher quality of frozen-thawed bull sperm.

Observational retrospective study of Intracytoplasmic sperm injection outcomes of 117 infertile men with severe short tail sperm defect

Intracytoplasmic sperm injection (ICSI) is increasingly used to treat male-factor infertility when sperm parameters are not proper for intrauterine insemination (IUI) or in vitro fertilization (IVF). Among sperm abnormalities, short tail sperm defect is a rare kind of teratozoospermia, which is a severe cause of male infertility. In this study, we evaluated the ICSI outcomes of infertile men with severely short tail sperm defect. 117 infertile men with primary infertility were included in this study. We evaluated the impact of short tail sperm defect on large ICSI series (228 cycles) outcomes. The fertilisation rate (FR) was 49.0%, the clinical pregnancy rate (PR) was 21.7%, and the delivery rate (DR) was 17.5%. The results of statistical analysis show that there is no relationship between short tail sperm defect and clinical pregnancy. According to the present study, there were patients with successful ICSI outcomes despite the severe defect in their spermatozoa flagella. Our results can be considered in two main aspects: (a) it seems that ICSI could be a proper therapy for infertile men with short-tailed sperm defect and (b) the abnormal sperm morphology (especially in sperm flagellum) is not a reliable predictor for the ICSI outcomes. In conclusion, our study suggests that ICSI should be considered as a proper treatment way for infertile men with severe short tail sperm defect and probably other sperm flagella abnormalities.

Cryopreservation effects on canine sperm morphometric variables and ultrastructure: Comparison between vitrification and conventional freezing

Semen cryopreservation is an increasingly demanded technique in canids, particularly in order to preserve and spread high genetic value material. Sperm vitrification may represent an interesting alternative to costly and time consuming conventional freezing. The objective of this study was to evaluate the effect of sperm vitrification on sperm morphometry and ultrastructure compared to conventional freezing. Pools of nine beagle dogs were both frozen and vitrified. Computerized morphological parameters (length, wide, area and perimeter) and sperm ultrastructure, using scanning and transmission microscopy, were analysed in both fresh and in thawed/warmed samples. There were no differences (p > 0.05) between post-thaw and fresh morphometric variables of the sperm heads. However, cluster analysis revealed that sperm-heads turned out to be smaller after thawing (p < 0.05) in two of the four subpopulations. Vitrification-warming process led to an overall increase in sperm-head size. Furthermore, the sperm head size increased after warming in two subpopulations (p < 0.05). In conclusion, the variations in the sperm head area depended on the cryopreservation procedure (conventional freezing or vitrification). Conventional freezing tended to decrease the head dimensions, at least in some subpopulations, and vitrification led to an overall increase in the sperm head size. Decondensation of chromatin and plasma membrane blebbing in the head region was observed by transmission electron microscopy in several vitrified sperm, which might explain the increase of head dimensions detected by CASA-Morph system.

Disruption of bovine sperm functions in the presence of aplastic midpiece defect

BACKGROUND

Bulls are of great importance in the productive chain and for this reason they should have a good semen quality. There is no doubt that sperm morphology is very important to bull fertility, although little is known about how exactly the abnormal morphologies may affect sperm functions.

OBJECTIVES

To detail the morphological description of the aplastic midpiece defect (AMD), as well as to understand its consequences for male fertility based on membrane and acrosome status, mitochondrial membrane potential and DNA integrity parameters.

MATERIALS AND METHODS

The bulls were divided into two groups: control, consisting of satisfactory potential breeders (n = 3); and AMD, consisting of unsatisfactory potential breeders with a high percentage of AMD (n = 3). Bulls were evaluated by the breeding soundness evaluation; five ejaculates were collected from each animal and analyzed by flow cytometry.

RESULTS

Spermatozoa from AMD group exhibited lower sperm motility and vigor (p < 0.05). In addition, it also exhibited lower mitochondrial membrane potential (p < 0.05), a higher percentage of spermatozoa with DNA fragmentation (p < 0.05), lower acrosome and plasma membrane integrity (p < 0.05), and higher lipid bilayer sperm membrane disorganization (p < 0.05) in comparison with control bulls.

DISCUSSION

These findings may be due to oxidative stress and a reduction of the energy production capacity in addition to an alteration in the structural composition of the sperm cell. Moreover, semen with a high percentage of AMD may also be undergoing apoptosis.

CONCLUSION

Bulls with a high percentage of AMD in their semen are not suitable for reproduction. Furthermore, it suggests there is a putative genetic basis for this sperm defect.

Phenotypic varieties of sperm pathology: Genetic abnormalities or environmental influences can result in different patterns of abnormal spermatozoa

The present paper reviews in detail ultrastructural and molecular studies addressed to characterize different phenotypes of sperm pathology in sterile men. In each case ultrastructural, immunocytochemical, molecular and genetic information is provided to differentiate two main kinds of sperm pathologies: systematic phenotypes with known or suspected genetic origin and non-systematic ones, usually secondary to different pathologies of the male reproductive system. Special attention is paid to detailed ultrastructural features profusely illustrated with electron micrographs. Diagnostic and fertility prognostic values of these phenotypes are also discussed and, when possible, comparison with similar pathologies in mammals and birds are discussed.

The importance of transmission electron microscopy analysis of spermatozoa: Diagnostic applications and basic research

This review is aimed at discussing the role of ultrastructural studies on human spermatozoa and evaluating transmission electron microscopy as a diagnostic tool that can complete andrology protocols. It is clear that morphological sperm defects may explain decreased fertilizing potential and acquire particular value in the field of male infertility. Electron microscopy is the best method to identify systematic or monomorphic and non-systematic or polymorphic sperm defects. The systematic defects are characterized by a particular anomaly that affects the vast majority of spermatozoa in a semen sample, whereas a heterogeneous combination of head and tail defects found in variable percentages are typically non-systematic or polymorphic sperm defects. A correct diagnosis of these specific sperm alterations is important for choosing the male infertility's therapy and for deciding to turn to assisted reproduction techniques. Transmission electron microscopy (TEM) also represents a valuable method to explore the in vitro effects of different compounds (for example drugs with potential spermicidal activity) on the morphology of human spermatozoa. Finally, TEM used in combination with immunohistochemical techniques, integrates structural and functional aspects that provide a wide horizon in the understanding of sperm physiology and pathology.

ABBREVIATIONS

transmission electron microscopy: TEM; World Health Organization: WHO; light microscopy: LM; motile sperm organelle morphology examination: MSOME; intracytoplasmic morphologically selected sperm injection: IMSI; intracytoplasmic sperm injection: ICSI; dysplasia of fibrous sheath: DFS; primary ciliary dyskinesia: PCD; outer dense fibers: ODF; assisted reproduction technologies: ART; scanning electron microscopy: SEM; polyvinylpirrolidone: PVP; tert-butylhydroperoxide: TBHP.

Evolutionary defined role of the mitochondrial DNA in fertility, disease and ageing

BACKGROUND

The endosymbiosis of an alpha-proteobacterium and a eubacterium a billion years ago paved the way for multicellularity and enabled eukaryotes to flourish. The selective advantage for the host was the acquired ability to generate large amounts of intracellular hydrogen-dependent adenosine triphosphate. The price was increased reactive oxygen species (ROS) inside the eukaryotic cell, causing high mutation rates of the mitochondrial DNA (mtDNA). According to the Muller's ratchet theory, this accumulation of mutations in asexually transmitted mtDNA would ultimately lead to reduced reproductive fitness and eventually extinction. However, mitochondria have persisted over the course of evolution, initially due to a rapid, extreme evolutionary reduction of the mtDNA content. After the phylogenetic divergence of eukaryotes into animals, fungi and plants, differences in evolution of the mtDNA occurred with different adaptations for coping with the mutation burden within these clades. As a result, mitochondrial evolutionary mechanisms have had a profound effect on human adaptation, fertility, healthy reproduction, mtDNA disease manifestation and transmission and ageing. An understanding of these mechanisms might elucidate novel approaches for treatment and prevention of mtDNA disease.

METHODS

The scientific literature was investigated to determine how mtDNA evolved in animals, plants and fungi. Furthermore, the different mechanisms of mtDNA inheritance and of balancing Muller's ratchet in these species were summarized together with the consequences of these mechanisms for human health and reproduction.

RESULTS

Animal, plant and fungal mtDNA have evolved differently. Animals have compact genomes, little recombination, a stable number of genes and a high mtDNA copy number, whereas plants have larger genomes with variable gene counts, a low mtDNA copy number and many recombination events. Fungal mtDNA is somewhere in between. In plants, the mtDNA mutation rate is kept low by effective ROS defence and efficient recombination-mediated mtDNA repair. In animal mtDNA, these mechanisms are not or less well-developed and the detrimental mutagenesis events are controlled by a high mtDNA copy number in combination with a genetic bottleneck and purifying selection during transmission. The mtDNA mutation rates in animals are higher than in plants, which allow mobile animals to adapt more rapidly to various environmental conditions in terms of energy production, whereas static plants do not have this need. Although at the level of the species, these mechanisms have been extremely successful, they can have adverse effects for the individual, resulting, in humans, in severe or unpredictably segregating mtDNA diseases, as well as fertility problems and unhealthy ageing.

CONCLUSIONS

Understanding the forces and processes that underlie mtDNA evolution among different species increases our knowledge on the detrimental consequences that individuals can have from these evolutionary end-points. Alternative outcomes in animals, fungi and plants will lead to a better understanding of the inheritance of mtDNA disorders and mtDNA-related fertility problems. These will allow the development of options to ameliorate, cure and/or prevent mtDNA diseases and mtDNA-related fertility problems.

Effects of the czech propolis on sperm mitochondrial function

Propolis is a natural product that honeybees collect from various plants. It is known for its beneficial pharmacological effects. The aim of our study was to evaluate the impact of propolis on human sperm motility, mitochondrial respiratory activity, and membrane potential. Semen samples from 10 normozoospermic donors were processed according to the World Health Organization criteria. Propolis effects on the sperm motility and mitochondrial activity parameters were tested in the fresh ejaculate and purified spermatozoa. Propolis preserved progressive motility of spermatozoa in the native semen samples. Oxygen consumption determined in purified permeabilized spermatozoa by high-resolution respirometry in the presence of adenosine diphosphate and substrates of complex I and complex II (state OXPHOSI+II) was significantly increased in the propolis-treated samples. Propolis also increased uncoupled respiration in the presence of rotenone (state ETSII) and complex IV activity, but it did not influence state LEAK induced by oligomycin. Mitochondrial membrane potential was not affected by propolis. This study demonstrates that propolis maintains sperm motility in the native ejaculates and increases activities of mitochondrial respiratory complexes II and IV without affecting mitochondrial membrane potential. The data suggest that propolis improves the total mitochondrial respiratory efficiency in the human spermatozoa in vitro thereby having potential to improve sperm motility.

Morphopathology of Sperm: It's Impact on Fertilization

Terato-, astheno- and necrozoospermia negatively influence fertility prognosis in spontaneous conditions or with the use of various assisted reproductive techniques including conventional in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). The correct identification of sperm pathologies will indicate different fertility potentials and outcomes in assisted reproduction technology. Anomalies of only the spermatozoa flagella bear a promising prognosis, but those affecting the sperm chromatin and the neck region entail an increasing chance of failure, which highlights the differential roles played by specific sperm components in fertilization, implantation and early embryonic development. Sperm pathology therefore allows an understanding of abnormal function that goes beyond that provided by classical sperm morphology classifications that are mainly based on descriptions of abnormal sperm shapes with no insight into the mechanisms or the pathological details.

Tales of the tail and sperm head aches: changing concepts on the prognostic significance of sperm pathologies affecting the head, neck and tail

This article presents an update on the variable prognostic significance of different sperm pathologies in patients with severe male factor infertility due to morphology and motility disorders. Severe asthenozoospermia is one of the leading causes of male infertility as spermatozoa cannot reach the oocyte and/or penetrate normally. Identifying structural causes of sperm immotility was of great concern before the advent of intracytoplasmic sperm injection (ICSI), because immotility was the limiting factor in the treatment of these patients. In these cases, in vitro methods are used to identify live spermatozoa or stimulate sperm motility to avoid selection of non-viable cells. With these advances, fertilization and pregnancy results have improved dramatically. The identification of genetic phenotypes in asthenozoospermia is important to adequately inform patients of treatment outcomes and risks. The one sperm characteristic that seriously affects fertility prognosis is teratozoospermia, primarily sperm head and neck anomalies. Defects of chromatin condensation and acrosomal hypoplasia are the two most common abnormalities in severe teratozoospermia. The introduction of microscopic methods to select spermatozoa and the development of new ones to evaluate sperm quality before ICSI will assure that ultrastructural identification of sperm pathologies will not only be of academic interest, but will also be an essential tool to inform treatment choice. Herein, we review the differential roles played by sperm components in normal fertilization and early embryo development and explore how assisted reproductive technologies have modified our concepts on the prognostic significance of sperm pathologies affecting the head, neck, mid-piece and tail.

Mitochondria in mammalian sperm physiology and pathology: a review

While, for a long time, the role of mitochondria in sperm physiology and pathology has been largely ignored, recent research points out the mitochondria as a major organelle with key roles in sperm function both under physiological and biotechnological conditions. This paper briefly reviews these novel findings regarding the role of mitochondria in sperm, paying special attention to the most practical, readily applicable, aspects of the topic such as their role as a major source of the sublethal damage that sperm experiments after cryopreservation.