Bull spermatozoa selected by thermotaxis exhibit high DNA integrity,specific head morphometry,and improve ICSI outcome

Background Sperm migration by thermotaxis is a guidance mechanism that operates along the oviduct and it has proved to be a valid method for selecting spermatozoa with low DNA fragmentation(SDF)in mice,humans,and stallions.This study aimed to analyse if bull spermatozoa could be selected by thermotaxis and to assess their quality in terms of SDF as well as determine the presence of a specific sperm subpopulation based on sperm morphometry and assess their fertilizing capacity by ICSI.Methods We used frozen-thawed sperm from 6 bulls and sperm selection by thermotaxis was performed with TALP medium supplemented with 25 mmol/L of HEPES and 5 mmol/L of caffeine.In these conditions,sperm selection was achieved,obtaining a net thermotaxis of 3.6%.Subsequently,we analysed the SDF of the migrated and not-migrated spermatozoa using the neutral COMET assay,and we evaluated the size of the sperm head using Hemacolor■ staining with Motic Images Plus 3 software.Additionally,migrated and not-migrated spermatozoa by thermotaxis were used to fertilize bovine in vitro matured(IVM)oocytes by ICSI,a very inefficient procedure in cattle that is only successful when the oocyte is artificially activated.Results The results showed lower SDF(χ^(2),P<0.001,13.3%reduction,n=8)and lower head size parameters(length and width,P<0.01;and perimeter and area,P<0.001;n=4)in those spermatozoa migrated in comparison to those not-migrated.The distribution of sperm subpopulations structure varied between groups,highlighting cluster 2,characterized by spermatozoa with small head size,and high ellipticity and elongated heads,as the most abundant in the thermotaxis migrated group.When performed ICSI(without oocyte artificial activation)with the thermotactic sperm,the blastocyst rate was 32.2%±9.3%in the group microinjected with the thermotactic spermatozoa vs.8.3%±7.8%in the group of not-migrated sperm(χ^(2),P<0.05).Conclusion Our results showed that bull sperm selection by thermotaxis has a much higher DNA integrity,small and elongated head size parameters,and different sperm subpopulation structure than the not-selected spermatozoa.Additionally,we evidenced that thermotactic spermatozoa improve ICSI success rates.

No difference in high-magnification morphology and hyaluronic acid binding in the selection of euploid spermatozoa with intact DNA

In this study, we compared conventional sperm selection with high-magnification morphology based on the motile sperm organellar morphology examination （MSOME） criteria, and hyaluronic acid （HA） binding for sperm chromosome aneuploidy and DNA fragmentation rates. Semen from 50 severe male factor cases was processed through density gradient centrifugation, and subjected to sperm selection by using the conventional method （control）, high magnification at x6650 or HA binding. Aneuploidy was detected by fluorescence in situ hybridization with probes for chromosomes 13, 18, 21, X and Y, and DNA fragmentation by the terminal deoxynucleotidyl transferase dUTP nick end labelling （TUNEL） method. Spermatozoa selected under high-magnification had a lower DNA fragmentation rate （2.6% vs. 1.7%; P=0.032）, with no significant difference in aneuploidy rate （0.8% vs0.7%; P=0.583）, than those selected by the HA binding method. Spermatozoa selected by both methods had much lower aneuploidy and DNA fragmentation rate than the controls （7% aneuploidy and 26.8% DNA fragmentation rates, respectively）. In the high-magnification group, the aneuploidy rate was lower when the best spermatozoa were selected than when only the second-best spermatozoa were available for selection, but the DNA fragmentation rate was not different. In conclusion, sperm selection under high magnification was more effective than under HA binding in selecting spermatozoa with low DNA fragmentation rate, but the small difference （0.9%） might not be clinically meaningful. Both methods were better than the conventional method of sperm selection.

Sperm preparation： state-of-the-art--physiological aspects and application of advanced sperm preparation methods

For assisted reproduction technologies （ART）, numerous techniques were developed to isolate spermatozoa capable of fertilizing oocytes. While early methodologies only focused on isolating viable, motile spermatozoa, with progress of ART, particularly intracytoplasmic sperm injection （ICSI）, it became clear that these parameters are insufficient for the identification of the most suitable spermatozoon for fertilization. Conventional sperm preparation techniques, namely, swim-up, density gradient centrifugation and glass wool filtration, are not efficient enough to produce sperm populations free of DNA damage, because these techniques are not physiological and not modeled on the stringent sperm selection processes taking place in the female genital tract. These processes only allow one male germ cell out of tens of millions to fuse with the oocyte. Sites of sperm selection in the female genital tract are the cervix, uterus, uterotubal junction, oviduct, cumulus oophorus and the zona pellucida. Newer strategies of sperm preparation are founded oni （i） morphological assessment by means of＇motile sperm organelle morphological examination （MSOM E）＇; （ii） electrical charge; and （ili） molecular binding characteristics of the sperm cell. Whereas separation methods based on electrical charge take advantage of the sperm＇s adherence to a test tube surface or separate in an electrophoresis, molecular binding techniques use Annexin V or hyaluronic acid （HA） as substrates. Techniques in this category are magnet-activated cell sorting, Annexin V-activated glass wool filtration, flow cytometry and picked spermatozoa for ICSI （PICSI） from HA-coated dishes and HA-containing media. Future developments may include Raman microspectrometry, confocal light absorption and scattering spectroscopic microscopy and polarization microscopy.

Novel mutation in ODF2 causes multiple morphological abnormalities of the sperm flagella in an infertile male

Numerous genes have been associated with multiple morphological abnormalities of the sperm flagella(MMAF),which cause severe asthenozoospermia and lead to male infertility,while the causes of approximately 50%of MMAF cases remain unclear.To reveal the genetic causes of MMAF in an infertile patient,whole-exome sequencing was performed to screen for pathogenic genes,and electron microscope was used to reveal the sperm flagellar ultrastructure.A novel heterozygous missense mutation in the outer dense fiber protein 2(ODF2)gene was detected,which was inherited from the patient’s mother and predicted to be potentially damaging.Transmission electron microscopy revealed that the outer dense fibers were defective in the patient’s sperm tail,which was similar to that of the reported heterozygous Odf2 mutation mouse.Immunostaining of ODF2 showed severe ODF2 expression defects in the patient’s sperm.Therefore,it was concluded that the heterozygous mutation in ODF2 caused MMAF in this case.To evaluate the possibility of assisted reproductive technology(ART)treatment for this patient,intracytoplasmic sperm injection(ICSI)was performed,with the help of a hypo-osmotic swelling test and laser-assisted immotile sperm selection(LAISS)for available sperm screening,and artificial oocyte activation with ionomycin was applied to improve the fertilization rate.Four ICSI cycles were performed,and live birth was achieved in the LAISS-applied cycle,suggesting that LAISS would be valuable in ART treatment for MMAF.

Influence of in vitro capacitation time on structural and functional human sperm parameters

A cascade of dramatic physiological events is linked to the sperm acrosome reaction and binding to the oocyte's zona pellucida during human sperm capacitation.However,structural and functional sperm changes during capacitation currently remain poorly defined.Here,we performed a multibiomarker approach based on the utilization of sperm concentration,motility,viability,morphology,acrosome reaction,tyrosine phosphorylation,DNA fragmentation,and lectin-binding sites to analyze the impact caused by swim-up selection times(uncapacitated,1 h capacitated,and 4 h capacitated)on sperm function and structure in normozoospermic samples.We found that a 4 h swim-up capacitation increased sperm quality,because a large number of cells with normal morphology and lower DNA fragmentation rates were recovered.Furthermore,the long-term capacitation induced a higher percentage of cells with tyrosine phosphorylation of the principal piece as well as a redistribution of lectin-binding sites.Overall,the multivariate biomarkers analyzed showed a less variable distribution on spermatozoa recovered after 4 h capacitation than that with the shorter capacitation time.These findings stress the importance of capacitation time as a relevant factor in sperm quality with potential biological reproductive implications both for basic research and in assisted reproduction techniques.

Oviductal epithelial cells selected boar sperm according to their functional characteristics

The interaction of oviductal epithelial cells （OECs） with the spermatozoa has beneficial effects on the sperm functions. The aim of this study is to evaluate the in vitro fertilizing capacity of incubating spermatozoa previously selected by density gradient in OEC and determinate some sperm characteristics that could explain the results obtained. In this study, we assessed in vitro fertilization （IVF）, tyrosine phosphorylation, phosphatidylserine translocation, nuclear DNA fragmentation, and chromatin decondensation. Three experimental sperm groups, previously selected by Percoll gradient, were established according to the origin of the sperm used for IVF： （i） W30 group： spermatozoa were incubated with oocytes in the absence of OEC; （ii） NB group： after sperm incubation in OEC, the unbound spermatozoa were incubated with oocytes, in the absence of OEC; and （iii） B group： after sperm incubation with OEC, the bound spermatozoa were incubated with oocytes in the OEC plates. The results showed that sperm from the NB group led to a lower IVF yield, accompanied by low penetration rates （NB： 19.6%, B： 94.9%, and W30： 62.9%; P 〈 0.001） and problems of nuclear decondensation. Moreover, higher levels of tyrosine phosphorylation were observed in the NB group compared with the W30 and B groups （NB： 58.7%, B： 2.5%, and W30： 4.5%; P 〈 0.01）. A similar trend was observed in phosphatidylserine translocation （NB： 93.7%, B. 5.7%, and W30： 44.2%; P 〈 0.01）. These results demonstrate that the OEC exerts a rigorous degree of sperm selection, even within an already highly selected population of spermatozoa, and can capture the best functional spermatozoa for fertilization.