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Under polarized light microscopy, sperm cell heads show birefringence properties
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ICSI under polarized microscopy allows identification of immotile viable sperm cells
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Immotile birefringent sperm cells lead to higher fertilization and cleavage rates
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Head partial birefringence is the strongest predictor for live birth delivery
Abstract
Research question
In sperm samples with complete asthenozoospermia, pregnancies are achieved by intracytoplasmic sperm injection (ICSI), but this condition has a negative impact on fertilization and embryo development owing to the difficulty of identifying viable cells for oocyte injection. Is the selection of sperm cells with head birefringence properties under polarizing light a successful strategy to identify viable spermatozoa?
Design
This study included 192 ICSI cycles with complete asthenozoospermia (83 ejaculated and 109 testicular samples) performed under polarized light. Two types of sperm head birefringence were distinguished: partial (presumably reacted spermatozoa) and total (presumably intact acrosome). In some sperm cells, no birefringence was present. The main outcome of the study was the cumulative live birth rate (cLBR) per ICSI cycle.
Results
Seventy-three deliveries resulted with 38.0% cLBR per ICSI cycle. The injection of birefringent spermatozoa led to significantly higher rates of fertilization, embryo development and implantation compared with the absence of birefringence (P < 0.001). Similarly, the resulting cLBR were 53.6% and 9.0%, respectively (P < 0.001). Spermatozoa with partial head birefringence yielded significantly higher fertilization and embryo utilization rates compared with total birefringence. The cLBR showed the same trend (62.7% and 46.7%, respectively, P = 0.048). Multiple logistic regression analysis showed the pattern of partial birefringence to be strongly associated with live birth rate.
Conclusions
Immotile sperm cells with birefringence properties under polarized light have higher chances of inducing fertilization and embryo development compared with non-birefringent cells. In addition, a pattern of partial birefringence, associated with a reacted acrosome, is the strongest predictive factor for live birth delivery, both in ejaculated and testicular samples.
As recently acknowledged by the World Health Organization (WHO), male infertility is a global health issue affecting millions of couples and individuals (https://www.who.int/news-room/fact-sheets/detail/infertility). There is currently a ubiquitous decline in natural fertility and a significant increase in the use of medically assisted reproduction (MAR) as a strategy to overcome the problems with conceiving (
Population-wide contribution of medically assisted reproductive technologies to overall births in Australia: temporal trends and parental characteristics.
European IVF Monitoring Consortium (EIM), for the European Society of Human Reproduction and Embryology (ESHRE) ART in Europe, 2018: results generated from European registries by ESHRE.
Asthenozoospermia, a decreased or absence of sperm motility in the ejaculate, is a cause of infertility. It is a complex disorder whose aetiology is linked to intrinsic and extrinsic factors (
). In its most severe form, a condition known as complete asthenozoospermia, motility is totally lacking, making it impossible for the sperm cell to autonomously reach and fertilize the oocytes. Absence of sperm motility is also very common in surgically retrieved samples, both from the epididymis and from the testis. For patients with this condition, ICSI represents the only option to achieve fertilization, embryo development and live births.
According to the published literature, sperm motility is a major determinant of the ICSI outcome (
). However, the injection of immotile spermatozoa has been shown to have a negative impact on fertilization and embryo development, although the implantation of the resulting embryos was not decreased (
Abnormal sperm concentration and motility as well as advanced paternal age compromise early embryonic development but not pregnancy outcomes: a retrospective study of 1266 ICSI cycles.
Effect of the male factor on the clinical outcome of intracytoplasmic sperm injection combined with preimplantation aneuploidy testing: observational longitudinal cohort study of 1,219 consecutive cycles.
). This finding suggests that in these cases a good response to hormonal stimulation in the female partner is especially important to compensate for the reduced fertilization capacity of immotile spermatozoa.
With the aim of avoiding the injection of necrotic spermatozoa in the absence of sperm motility, several strategies have been proposed, including exposure to pentoxifylline, hypo-osmotic swelling test, laser assisted sperm selection, magnetic activated cell sorting and polarization microscopy (reviewed by
Under polarized light, the head of viable sperm cells and some parts of the tail look birefringent due to the anisotropic properties of their protoplasmic texture (
). In the head of the mature sperm nucleus, the birefringence effect is provided by the regular and repetitive organization of the nucleoprotein filaments and of the sub-acrosomal protein filaments (
). Alterations of this organized structure occur in defective sperm cells, causing the loss of birefringence properties. Based on these considerations, the presence of head birefringence has been proposed as a criterion to select a viable spermatozoon with the lowest incidence of sperm aneuploidy and the highest chances of DNA integrity (
It was also shown that analysis of the sperm head birefringent patterns permits discrimination between cells with an intact acrosome from those that have already completed the acrosome reaction. As already described, sperm cells with a total birefringent head have an intact acrosome, whereas those with a partial birefringence localized in the post-acrosomal region have already undergone the acrosome reaction (
Preliminary studies supported the use of polarization microscopy during ICSI in the case of samples with total asthenozoospermia, with the best results achieved when injecting cells that had already completed the acrosome reaction (
,). The current study documents the experience derived from the selection of immotile spermatozoa based on their birefringence properties. Both ejaculated samples and testicular samples with total asthenozoospermia were included. The primary outcome was the cumulative live birth delivery rate per ICSI cycle (cLBR).
Materials and methods
Patients
A total of 192 consecutive ICSI cycles from 156 patients were included in the study. All patients had a normal karyotype and the mean female age was 34.9 ± 4.4 years. A severe male factor was indicated as the main cause of infertility. Ejaculated sperm samples with complete asthenozoospermia were used in 83 cycles, and cryopreserved testicular spermatozoa in 109 cycles with non-obstructive azoospermia (
). In all samples, there was a total absence of sperm motility.
Following ovarian stimulation and ovulation induction, oocytes were incubated and inseminated approximately 4–6 h later. ICSI was performed on an inverted microscope (Leica DMIRB; Leica Microsystem, Wetzlar, Germany) equipped with Leica modulation contrast, polarizing and analysing lenses and motorized micromanipulators (TransferMan NK; Eppendorf, McHenry, IL, USA) (
). Briefly, the source of light crossed the polarizing lens, the Hoffman lens, the condenser and the specimen, and passed through a 40 × and a PL Fluotar L63 × objective (Leica Microsystems). The beam of polarized light crossed a compensator and an analyser, and entered the first optical unit where the resulting ray hit a mirror. Then, it reflected along a second optic pathway through which the polarized image of the specimen entered the eyepiece. The images were captured by a camera connected to a monitor.
Sperm cells were scored to identify those with a birefringent head with the 40 × objective, but the 63 × objective was used for a more detailed morphological analysis.
As previously described, two main patterns of sperm head birefringence could be seen (total birefringence and partial birefringence), in addition to total absence of birefringence (Figure 1). A total birefringence was indicative of the presence of an intact acrosome, whereas a partial birefringence, localized in the post-acrosomal region, corresponded to a spermatozoon that had undergone the acrosome reaction (
). Before assessing the birefringence pattern, each sperm cell was repeatedly rotated to exclude any influence by the relative position between the spermatozoa and the light source.
Figure 1Observation of morphologically normal sperm cells by polarized microscopy. Total birefringence: the birefringent aspect of the whole head is related to a cell that still has an intact acrosome. Partial birefringence: the localization of the birefringence in the post-acrosomal region is indicative of a cell that has already undergone the acrosome reaction. No birefringence: the absence of birefringence indicates a cell with a compromised inner structure.
According to previous studies supporting the use of reacted sperm cells for ICSI, the selection of spermatozoa to be injected was based on the following criteria: first priority given to partial birefringence, second priority given to total birefringence, third priority given to absence of birefringence (
). The selection was made among morphologically normal spermatozoa. All oocytes were cultured individually.
The study was given institutional review board approval (ref. 231109) on 23 November 2009.
Fertilization assessment and embryo scoring
Approximately 16 h after ICSI, oocytes were observed for the presence of pronuclei and polar bodies. Regularly fertilized oocytes were scored 64 h after insemination. Number and morphology of nuclei and blastomeres, and percentage of fragmentation, were recorded (
Alpha Scientists in Reproductive Medicine and ESHRE Special Interest Group Embryology The Istanbul Consensus workshop on embryo assessment: proceedings of an expert meeting.
). Embryos with regular morphology and development were selected either for transfer or cryopreservation. The embryo utilization rate was the ratio between the number of usable embryos (defined as those suitable for transfer or cryopreservation) and the number of normally fertilized oocytes (
ESHRE Special Interest Group of Embryology; Alpha Scientists in Reproductive Medicine The Vienna consensus: report of an expert meeting on the development of ART laboratory performance indicators.
Embryo transfer was performed on day 3. Internal policy was to transfer one embryo at the first two transfer cycles unless otherwise suggested by other factors such as embryo quality and number of previous attempts. Two was the maximum number of transferred embryos.
The primary outcome of the study was the cLBR per ICSI cycle. Secondary outcome measures were clinical pregnancy rate per embryo transfer, implantation rate and miscarriage rate.
The definition of the clinical parameters was based on the International Glossary on Infertility and Fertility Care (
). Briefly, a clinical pregnancy corresponded to the presence of a gestational sac with fetal heartbeat (FHB). The implantation rate was expressed as the number of gestational sacs with FHB divided by the number of transferred embryos. A miscarriage was a spontaneous pregnancy loss occurring earlier than the 20th gestational week. A live birth delivery was defined as the birth of at least one living infant. The cLBR per ICSI cycle was the number of deliveries with at least one live birth resulting from one oocyte retrieval, including all fresh and/or frozen embryo transfers until one delivery with a live birth occurred or until all embryos were used, whichever occurred first.
Statistical analysis
Data are shown as mean ± SD, or as ratio and percentage. Comparisons between normally distributed continuous variables were made using Student's t-test. Comparisons between categorical variables were tested by using contingency tables and chi-squared test or Fisher's test when necessary. In order to check their association with the main outcome variable (cLBR), a multiple logistic regression was performed setting maternal age, number of inseminated oocytes, paternal age, sperm source, birefringence patterns, number of transferred cycles and number of transferred embryos as independent variables. Consequently, a receiver operating characteristic (ROC) curve was drawn to assess the predictivity of the model, calculating the area under the curve (AUC), sensitivity, specificity, accuracy, negative predictive power and positive predictive power. The Hosmer–Lemeshow and log-likelihood ratio tests were conducted to verify the goodness-of-fit of the model. A value of P < 0.05 was considered as statistically significant.
Results
The 156 couples included in the study underwent 192 ICSI cycles resulting in a 55.0% fertilization rate of the 1339 inseminated oocytes (Table 1). In all, the number of transferred cycles was 222, yielding 83 cumulative clinical pregnancies with an implantation rate of 29.9%. There were 73 live birth deliveries, corresponding to a LBR of 32.9% per transferred cycle, and a cLBR of 38.0% per ICSI cycle, and 46.8% per patient. Comparison between ejaculated and testicular sperm samples showed a significantly higher fertilization rate in ejaculated spermatozoa (61.0% versus 51.2%, P < 0.001), whereas the clinical outcome was substantially comparable, with the only exception of a higher cLBR rate per ICSI cycle in ejaculated spermatozoa (47.0% versus 31.2%, P = 0.0255).
Table 1Laboratory and clinical outcomes in 192 ICSI cycles
In 22 cycles (five in the ejaculated sperm group and 17 from the testicular sample group), no embryo transfer could be performed due to failed fertilization or cleavage arrest. In six cycles (maternal age 36.5 ± 3.8 years, two from the ejaculated sample group and four from the testicular sample group), no fertilization occurred after the insemination of 16 oocytes (3.0 ± 1.8 inseminated oocytes per cycle), whereas in 16 cycles (maternal age 35.6 ± 3.4 years, two from the ejaculated sample group and 14 from the testicular sample group), none of the 41 fertilized oocytes (32.3 fertilization rate over 127 inseminated, 8.5 ± 3.3 inseminated per cycle) cleaved to embryos suitable for transfer or cryopreservation.
ICSI with birefringent versus non-birefringent spermatozoa
As shown in Table 2, 125 ICSI cycles were performed with birefringent spermatozoa, whereas no birefringent sperm cells could be found in the remaining 67 samples. The resulting fertilization rates were 63.9% and 38.4%, respectively (P < 0.001), and the embryo utilization rate was 57.2% versus 40.4%, respectively (P < 0.001). All the 125 cycles injected with birefringent spermatozoa underwent at least one embryo transfer, whereas this occurred in only 45 of the 67 cycles (67.2%) where only non-birefringent sperm cells were available (P < 0.001).
Table 2Laboratory and clinical outcomes according to the presence or absence of birefringence in sperm heads
Outcome
Birefringence
No birefringence
P-value
ICSI cycles
125
67
Age, years
34.7 ± 4.5
35.2 ± 4.1
Testicular samples
59 (47.2)
50 (74.6)
<0.001
Inseminated oocytes
875
464
Fertilized oocytes
559 (63.9)
178 (38.4)
<0.001
Usable embryos
320 (57.2)
72 (40.4)
<0.001
Transferred cycles
168
54
Cycles with at least one embryo transfer
125 (100)
45 (67.2)
<0.001
Clinical pregnancies per embryo transfer
76 (45.2)
7 (13.0)
<0.001
Implantation rate (%)
35.2
10.9
<0.001
Miscarriages
9 (11.8)
1 (14.3)
Deliveries
67
6
Data are presented as n, n (%) or mean ± SD unless otherwise stated.
As illustrated in Figure 2, the LBR per embryo transfer was significantly higher in the samples injected with birefringent spermatozoa (39.9%) when compared with those where ICSI was performed with non-birefringent spermatozoa (11.1%, P < 0.001). The cLBR per ICSI cycle (53.6% versus 9.0%, P < 0.001) and per patient (63.8% versus 9.7%, P < 0.001) followed the same trend (Figure 2).
Figure 2Live birth delivery rate per embryo transfer, and cumulative live birth delivery rate per oocyte aspiration and per patient in 125 intracytoplasmic sperm injection (ICSI) cycles with birefringent sperm heads (blue bars) and in 67 ICSI cycles with no birefringent sperm heads (grey bars). In all cases, the (cumulative) live birth delivery rates were significantly higher in ICSI cycles performed with birefringent sperm heads (39.9%, 53.6% and 63.8%, respectively) compared with ICSI with non-birefringent sperm heads (11.1%, 9.0% and 9.7%, respectively, abcP < 0.001). Values with the same superscript are significantly different.
Whereas the maternal age did not differ significantly between the two groups, the proportion of testicular samples in the group of non-birefringent spermatozoa (74.6%) was significantly higher compared with the group where ICSI was performed with birefringent spermatozoa (47.2%, P < 0.001) (Table 2).
Head birefringence in ejaculated versus testicular sperm samples
Almost half of testicular samples had non-birefringent cells (45.9%), whereas in ejaculated samples, this proportion was significantly lower (20.5%, P < 0.001) (Table 3).
Table 3Presence of head birefringence in ejaculated and testicular sperm samples
In both ejaculated and testicular sample groups, the fertilization rates were higher after the injection of birefringent sperm cells (65.5% in ejaculated samples and 62.3% in testicular samples) than after ICSI with non-birefringent sperm cells (40.4% in ejaculated samples, P < 0.001; 37.8% in testicular samples, P < 0.001). Notably, fertilization rates were similar between ejaculated and testicular samples after the injection of spermatozoa with head birefringence (65.5% and 62.3%, respectively) or without (40.4% and 37.8%, respectively). The clinical outcome followed the same trend with a cLBR that did not differ between ejaculated and testicular samples when injecting birefringent sperm cells (56.1% versus 50.8%) or non-birefringent spermatozoa (11.8% versus 8.0%).
A more detailed representation of treated samples is given in Table 4, which shows the laboratory and clinical outcomes in relation to the pattern of birefringence of the injected spermatozoa in ejaculated and testicular sperm samples. The main significant differences related to the injection of birefringent sperm head cells (irrespective of the type of birefringence) and the injection of spermatozoa with no birefringence heads. No relevant differences were detected between ejaculated and testicular sperm cells within the same type of birefringence pattern.
Table 4Laboratory and clinical outcomes according to the birefringence patterns of the injected ejaculated and testicular spermatozoa
ICSI with birefringent spermatozoa: partial birefringence versus total birefringence
Based on the results from previous studies, priority was given to the injection of morphologically normal spermatozoa with partial head birefringence (
). Therefore, each sample was carefully scored at ICSI to identify this type of cell.
In 51 cycles, ICSI was performed using morphologically normal spermatozoa with partial head birefringence; in 45 cycles only morphologically normal sperm cells with total birefringence were found for injection, and in the remaining 29 cycles both types were used because not enough spermatozoa with partial birefringence were present to inseminate all the oocytes collected (Table 5). Fertilization and embryo utilization rates were significantly higher in the group of partial birefringence (68.9% and 68.3%, respectively) compared with total birefringence (58.6%, P = 0.0062, and 52.1%, P = 0.0008, respectively). The same trend was recorded for the clinical outcome (cLBR 62.7% versus 46.7%, P = 0.048). In the mixed group, results did not differ significantly from the other two groups.
Table 5Laboratory and clinical outcomes according to the birefringence patterns of the injected spermatozoa
Figure 3 displays the fertilization rates and cLBR in ejaculated and testicular samples according to the patterns of birefringence. All birefringent patterns showed an improved outcome in comparison with the injection of non-birefringent spermatozoa. Despite a trend apparently favouring the use of sperm cells with partial head birefringence over those with total birefringence, no significant differences were detected.
Figure 3Fertilization and cumulative live birth delivery rates according to the head birefringence patterns in the 192 intracytoplasmic sperm injection samples; 83 were ejaculated (green bars) and 109 were testicular samples (blue bars). (A) The injection of birefringent spermatozoa produced a significantly higher fertilization rate both in ejaculated and testicular sperm samples compared with non-birefringent spermatozoa (acdefP < 0.001; bP = 0.0104), irrespective of the type of birefringence. (B) The cumulative live birth delivery rate was significantly higher after the injection of birefringent sperm cells compared with non-birefringent spermatozoa, both in ejaculated and surgically retrieved sperm samples (gP = 0.0006; hP = 0.0324; iP = 0.0064; jkP < 0.001; lP = 0.0116). The different patterns of birefringence did not have a significant effect on the outcome. Values with the same superscript are significantly different.
Multiple logistic regression analysis and ROC curve
The results of the multiple logistic regression analysis are reported in Table 6. As expected, an increased maternal age was negatively associated with the cLBR showing an odds ratio (OR) of 0.78 (95% confidence interval [CI] 0.68–0.88, P < 0.0001). Coherently, the number of inseminated oocytes was positively related to the cLBR with an OR of 1.15 (95% CI 1.03–1.31, P = 0.0197).
ICSI with spermatozoa showing a partial birefringence pattern resulted in an OR of 5.58 (95% CI 2.45–13.56, P < 0.0001). Accordingly, a ROC curve was plotted displaying an AUC of 0.81 (95% CI 0.74–0.87, P < 0.0001) (Figure 4A). The specificity and the sensitivity of the model were 81.00% and 68.57%, respectively, resulting in an accuracy of 75.88%; the negative predictive value and the positive predictive value were 78.64% and 71.64%, respectively (Figure 4B).
Figure 4Receiver operating characteristic (ROC) curve and predicted probability for the prediction of live birth delivery in intracytoplasmic sperm injection (ICSI) cycles with immotile spermatozoa showing a partial birefringence pattern. ICSI with partially refringent spermatozoa had an odds ratio of 5.58 (95% confidence interval [CI] 2.45–13.56, P < 0.0001). (A) The ROC curve displayed an area under the curve (AUC) of 0.81 (95% CI 0.74–0.87, P < 0.0001). The specificity and the sensitivity of the model were 81.00% and 68.57%, respectively, resulting in an accuracy of 75.88%. (B) The negative predictive value and the positive predictive value were 78.64% and 71.64%, respectively. The predicted probability of live birth delivery is expressed as a function of the observed cases (observed no = no delivery, observed yes = live birth delivery).
Both the Hosmer–Lemeshow test and the log-likelihood ratio test confirmed the goodness-of-fit of the model (P = 0.2862 and P < 0.0001, respectively).
Discussion
This study reports on an experience with the use of polarizing microscopy in 192 ICSI cycles with complete asthenozoospermia. In all, 73 deliveries were recorded, corresponding to 38.0% cLBR per ICSI cycle (Table 1).
The first consideration emerging from the dataset was that sperm cells with head birefringence properties under polarized light are more able to induce fertilization, embryo development and implantation than those with no birefringence (Table 2). Accordingly, the cLBR per ICSI cycle was 53.6% in samples injected with birefringent spermatozoa versus 9.0% in the absence of birefringence (P < 0.001; Figure 2). These results propose polarizing microscopy as an effective tool in the case of immotile spermatozoa, as it enables the identification of those with a normal protoplasmic structure (presumably viable) from those with structural defects (presumably non-viable). The correlation between birefringence properties and the sperm structural normality has been supported by TEM analyses (
). The longitudinally and orderly oriented nucleoprotein filaments in the sperm nucleus and in the acrosomal region give sperm cells a typical birefringence appearance when observed under polarizing light (
). In addition, the birefringence patterns vary depending on the status of the acrosome, enabling the distinction between cells with an intact acrosome from those that have already completed the acrosome reaction (Figure 1). This finding was confirmed by TEM and by the labelling of sperm cells with fluorescein isothiocyanate Pisum Sativum agglutinin (PSA-FITC), which is uniformly green in cells with an intact acrosome, whereas in reacted spermatozoa the fluorescence is localized in an equatorial green band (
In the group presenting with total absence of sperm head birefringence, the majority of samples had been surgically retrieved, suggesting that testicular spermatozoa could have a higher incidence of sperm cells with protoplasmic abnormalities (Table 2). However, data from the literature generally report testicular spermatozoa having a similar or a better performance than ejaculated spermatozoa in men with total asthenozoospermia (
Reproductive outcomes of testicular versus ejaculated sperm for intracytoplasmic sperm injection among men with high levels of DNA fragmentation in semen: systematic review and meta-analysis.
). Looking at the current results, the data presented in Tables 3 and 4 show a similar performance when comparing birefringent spermatozoa from ejaculated versus testicular spermatozoa or non-birefringent spermatozoa from ejaculated versus testicular spermatozoa. This was confirmed by the multiple logistic regression analysis that indicated the sperm source (ejaculated or testicular) as a factor with no effect on the primary outcome of the study (Table 6). Conversely, significant differences were found between birefringent and non-birefringent spermatozoa within both subgroups (ejaculated and testicular spermatozoa), implying that the presence of birefringence was the key factor related to the outcome of the studied samples, irrespective of the sperm origin (Table 6).
According to these findings, the process of identifying viable spermatozoa is especially important in samples with complete asthenozoospermia. It is well known that the success of ICSI is generally independent of the sperm basic indices and source, with the exception of complete immotility, which negatively impact on fertilization, embryo development and clinical pregnancy rate (
). The current results suggest sperm selection under polarized light as a valuable strategy for the identification of viable cells.
The second consideration emerging from the analysis of this data was the different outcome related to the observed pattern of birefringence. As illustrated in Table 5, the injection of sperm cells with partial birefringence (presumably reacted spermatozoa) yielded significantly higher fertilization and embryo utilization rates compared with total birefringence (presumably intact acrosome). The cLBR showed the same trend (62.7% and 46.7%, respectively, P = 0.048).
There are no conclusive data in the literature about the effect of the acrosome status on injected spermatozoa. Some studies report better fertilization and embryo development when ICSI is performed with acrosome-reacted spermatozoa (
Structure-based redesigning of pentoxifylline analogs against selective phosphodiesterases to modulate sperm functional competence for assisted reproductive technologies.
). These results are not surprising, if the biological events that occur at fertilization are considered. In in-vivo conception and in conventional IVF, the fusion of the two gametes ensures the loss of the acrosome vesicle before the entrance of the sperm cell into the ooplasm (
). This step is bypassed during ICSI, where the status of the acrosome of the injected spermatozoa is unknown when the spermatozoa are selected under non-polarized light. Therefore, although the membrane is intentionally damaged by the ICSI needle just before the injection, a proportion of the injected spermatozoa probably have an intact acrosome. There is no doubt that the release of acrosomal enzymes into the ooplasm is not a natural event that could be harmful to the oocyte, as proven in the hamster (
With the aim of verifying the effect of the birefringence patterns on the clinical outcome, a multiple logistic regression analysis was performed; this indicated the pattern of partial birefringence as strongly associated with live birth delivery in ICSI cycles with immotile spermatozoa (Figure 4). As expected, the clinical outcome was dependent on maternal age and number of inseminated oocytes, but when controlling for these factors, the birefringent pattern appeared to be the crucial factor related to live birth delivery. The specificity and sensitivity of the model resulting in an accuracy of 75.88%, and the negative and positive predictive values of 78.64% and 71.64%, respectively, supported the proposed approach as a method with great potential in cases of couples undergoing ICSI due to complete asthenozoospermia.
In conclusion, immotile sperm cells with birefringence properties under polarized light possess higher chances of inducing fertilization and embryo development compared with non-birefringent cells. In addition, a pattern of partial birefringence, associated with a reacted acrosome, is the strongest predictive factor for live birth delivery, both in ejaculated and testicular samples. This method could also represent a diagnostic tool that, in patients with complete asthenozoospermia in the ejaculate, could be used to decide whether to recommend a surgical retrieval aimed at collecting spermatozoa of better quality.
Data Availability
Data will be made available on request.
References
Al-Malki A.H.
Alrabeeah K.
Mondou E.
Brochu-Lafontaine V.
Phillips S.
Zini A.
Testicular sperm aspiration (TESA) for infertile couples with severe or complete asthenozoospermia.
Abnormal sperm concentration and motility as well as advanced paternal age compromise early embryonic development but not pregnancy outcomes: a retrospective study of 1266 ICSI cycles.
Population-wide contribution of medically assisted reproductive technologies to overall births in Australia: temporal trends and parental characteristics.
Reproductive outcomes of testicular versus ejaculated sperm for intracytoplasmic sperm injection among men with high levels of DNA fragmentation in semen: systematic review and meta-analysis.
Effect of the male factor on the clinical outcome of intracytoplasmic sperm injection combined with preimplantation aneuploidy testing: observational longitudinal cohort study of 1,219 consecutive cycles.
Structure-based redesigning of pentoxifylline analogs against selective phosphodiesterases to modulate sperm functional competence for assisted reproductive technologies.
Maria Cristina Magli is an embryologist who has been coordinating the laboratories of the Italian Society for the Study of Reproductive Medicine since 1995. In ESHRE, she coordinated the Special Interest Group in Embryology, was a member of the Executive Committee and Chair of ESHRE between 2019 and 2021. She is currently Immediate Past-Chair of the Society.
Key message
Immotile spermatozoa with birefringence properties under polarized light have higher chances of inducing fertilization and embryo growth than non-birefringent cells. A pattern of partial birefringence, associated with a reacted acrosome, is the strongest predictive factor for live birth delivery, both in ejaculated and testicular samples.
Article info
Publication history
Published online: November 30, 2022
Accepted:
November 25,
2022
Received in revised form:
November 5,
2022
Received:
August 24,
2022
Declaration: The authors report no financial or commercial conflicts of interest.
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