Increased pregnancy after reduced male abstinence

Abstract

This study was conducted to test the hypothesis that continuous epididymal sperm depletion after recurrent ejaculations (REC) in contrast to a period of abstinence (ABS) results in a decreased level of sperm DNA fragmentation (SDF) and a consequent increased rate of pregnancy. Forty couples undergoing intra-cytoplasmic injection (ICSI) were asked to abstain from ejaculation for a period of 4 days and then ejaculate once per day for a period of 4 days, followed by a period of abstinence for 12 hours; sperm samples obtained after ABS and REC were assessed for volume, concentration, motility, and SDF and compared in 25 of the patients. Additionally, and in a different experiment, the pregnancy rate of this experimental group (40 couples) was compared to a control group of 150 couples in which the males had abstained from ejaculation for 4 days prior to ejaculation. Sperm selection was performed using density gradient centrifugation prior to ICSI. Semen quality in the REC group that was assessed over the course of the ejaculation schedule showed a decrease in semen volume (67%) and SDF (27%) following sperm selection; there was no difference for sperm motility or sperm concentration. When the pregnancy rate between the 40 couples in the REC group and 150 couples in the control ABS group were compared, the REC group had a pregnancy rate of 56.4% (25/40), whereas the ABS rate was only 43.3% (65/150) (p = 0.030). We conclude that recurrent ejaculation every 24 hours for four days with a final abstinence of 12 hours, combined with sperm selection using density gradient centrifugation, produces a significant increase in pregnancy rate when using ICSI. As ICSI was the strategy selected for fertilization, we propose that the observed reduction in SDF was the primary factor leading to improved reproductive outcome.

Keywords:

• assisted reproduction
• fertility
• male factor
• sperm DNA fragmentation

Introduction

Various strategies are now available to reduce the level of sperm damage in the ejaculate. When intra-cytoplasmic injection (ICSI) is selected for fertilization, most preparatory techniques involve ex vivo selection of a low number of spermatozoa containing the best possible DNA molecule. Thus, the use of magnetic cell sorting with annexinV–conjugated microbeads to target and remove apoptotic or apoptotic-like spermatozoa has now become fashionable [Said et al. 2006]. The use of testicular sperm retrieval is also attracting interest because it is claimed that the level of sperm DNA fragmentation (SDF) is lower than that found in the ejaculate [Greco et al. 2005]. Furthermore, this is the only way patients with severe oligospermia are able to obtain functional syngamy. While high resolution microscopy for selection of better sperm morphology [Bartoov et al. 2003; Antinori et al. 2008] and hyaluronic acid based diluents for the best physiological conditions [Huzar et al. 2003] allow indirect selection of the most capable sperm along with the quality DNA, treatments such as the use of the magnetic beads can potentially lead to compromises in physiological homeostasis of the sperm cell [Salian et al. 2012]. This may well produce cryptic levels of iatrogenic sperm damage that could compromise the reproductive outcome [Goudakou et al. 2012].

While we may expect further advances in these proven technologies, we propose that other less invasive protocols based on an understanding of simple physiology and mechanical manipulation of the sperm cell can be equally, if not more effective in improving outcomes for assisted reproduction technology (ART); this includes the use of recurrent ejaculation to improve standard seminal characteristics [Levitas et al. 2005], and SDF [Gosálvez et al. 2011]. While it might seem logical and intuitive for the male patient to undergo a period of abstinence for 3 to 4 days prior to using his sperm in ART so as to increase the volume and number of spermatozoa available for fertilization, there is currently no medical evidence to support such a claim. The lack of DNA repair in the maturing sperm means that the passage of the ejaculate down the epididymis and its accumulation in the caudal region of the epididymis is a physiological necessity for sperm maturation and future capacitation, but it has no beneficial effect on the DNA molecule. Furthermore, a long period of storage and accumulation of sperm in the cauda epididymidis may expose it to increased damage associated with oxidative stress or even to enzymes released by degenerating spermatozoa with ruptured membranes.

The present experiment was conducted to test the hypothesis that continuous epididymal sperm depletion, using recurrent ejaculations (REC), results in a decreased level of sperm DNA damage when compared to sperm recovered after abstinence (ABS) and this can lead to an increased chance of pregnancy in an ICSI fertilization setting. We propose that when using ICSI sperm, DNA fragmentation is likely to be the most important variable for improving and predicting reproductive outcome, as parameters such as critical sperm concentration, poor membrane quality, sperm motility, or incomplete sperm capacitation are unlikely to be directly invoked as limiting factors for the fertilization of a female gamete.

Results

Twenty-one of the 40 patients in the REC group were able to follow the prescribed ejaculation schedule in order to examine changes in seminal characteristics and SDF (Table 1). The Wilcoxon signed-rank test for a non-parametric analysis when comparing two related samples showed that there were significant differences in volume (Z = −3.929; P 0.000) and SDF (Z = −3.991; P 0.000) between the first ejaculate after 4 days ABS and following 4 days of REC; seminal volume reduced by 67% and SDF decreased by approximately 27%. There was no difference in sperm concentration (Z= -0.355; P 0.723) or sperm motility (Z= −1.064; P 0.278).

Table 1. Data and basic descriptive statistics for volume (Vol: ml), concentration (Con: millions per ml), motility (Mot: percent of progressive motility), and sperm DNA fragmentation (SDF: % of sperm DNA fragmentation). The results represented 21 out of 40 patients that were able to provide ejaculates after 4 days of abstinence (ABS) followed by 4 days of recurrent ejaculation (REC).

Patient	Vol-ABS	Vol-REC	Con-ABS	Con-REC	Mot-ABS	Mot-REC	SDF-ABS	SDF-REC
1	2.8	1.2	25	20	38	12	31	22
2	1.5	0.6	16	7	58	42	38	30
3	2.6	0.6	80	65	60	21	36	25
4	4	1.2	62	90	45	49	41	32
5	3.5	3.4	41	22	42	71	16	8
6	8	2.4	26	51	53	60	35	27
7	3.2	1.8	50	75	52	65	31	25
8	2.8	1	95	68	57	45	15	10
9	2.2	1.8	57	40	19	15	29	23
10	3	1.2	75	52	59	42	18	12
11	4	2	48	30	68	43	8	5
12	2.5	0.8	63	95	59	27	22	18
13	7.7	2.6	10	8	15	27	30	24
14	0.8	0.3	12	9	12	20	22	10
15	3.8	3	98	90	35	45	12	11
16	3.5	2	33	48	39	52	38	32
17	3	2.7	30	40	43	50	9	9
18	2.2	2	27	55	22	20	48	27
19	1	1.2	101	75	60	60	24	17
20	5	2.1	14	13	69	55	33	25
21	6	2	54	80	50	42	30	19
Mean	4.3	2.0	48.4	49.2	45.5	41.1	27.0	19.6
SD	2.0	0.6	28.3	28.4	16.6	16.7	10.8	8.3

A correlation analysis was performed (Spearman Rho) to gauge the extent to which increases or decreases in one variable mirrored those in the other variable when ABS and REC values are compared. Values obtained for ABS and REC were positively correlated when volume (Spearman-Rho: 0.676; P 0.01), concentration (Spearman-Rho: 0.800; P 0.01), and SDF (Spearman-Rho: 0.953; P 0.01) were compared. The correlation was low and not significant when values for sperm motility were compared (Spearman-Rho: 0.360; P 0.109). While not of clinical relevance, especially under an ICSI protocol, these results suggest that values for the different variables obtained during ABS could be considered as predictive of those that will be obtained during REC.

The pregnancy rate observed by fetal heartbeat in the REC experimental group was 56.4% (25/40). In comparison, the control group which used sperm from males after a 4 day period of abstinence based on clinic records for similar reproductive scenarios had a pregnancy rate of 43.3% (65/150); this represented a significant (χ2 4.65; df 1; p = 0.030) increase in pregnancy rate of around seven percentage points.

Discussion

This study has revealed that spermatozoa recovered following recurrent ejaculation in human patients every 24 hours for four days with a final abstinence of 12 hours and in combination with sperm selection using density gradient centrifugation and used for ICSI, results in an improved pregnancy rate when compared to patients undergoing abstinence for 4 days. Given this improvement we recommend this simple protocol be carried out as a routine procedure prior to sperm selection and fertilization (Fig. 1).

Figure 1.  Flow chart diagram showing the differences in inter-ejaculation periods in recurrent and abstinence experiments. White circles labeled with SCA (sperm characteristics assessment) indicate the sperm samples which were used for SCA.

In using ICSI, a marked decrease in seminal volume between ABS and REC ejaculates presents no practical disadvantage. Additionally, no significant differences were observed in sperm motility or sperm concentration, but again these parameters do not compromise the selection of suitable spermatozoa for ICSI. Given this information, it is clear that the main factor explaining the improvement in pregnancy rate of this study is likely attributable to a reduction in sperm DNA damage. Our data is therefore further evidence of the importance of sperm DNA fragmentation for predicting and/or improving pregnancy, not only for humans [Evenson et al. 1999; Zini and Libman 2006; Bungum 2012] but also in other animal models [Kumar et al. 2013].

In general, sperm selection using density gradient centrifugation or swim-up techniques is associated with a decrease in the levels of sperm DNA damage [Zini et al. 2000; Gosálvez et al. 2010; Enciso et al. 2011]; some studies have also shown the benefit of using selected spermatozoa to improve pregnancy [Ng et al. 1992; Tanpaichitr et al. 1988]. This technical practice no doubt increases the probability of selecting a sperm free of DNA damage prior to ICSI. However, it should also be noted that while the incidence of SDF in the selected population may be reduced after these procedures, there is still a reasonable chance of accidently selecting a single spermatozoa containing non-reparable DNA damage that was not previously excluded in the selection procedure. In fact, in some cases, the level of SDF may even increase in the selected sample when compared to the level of SDF in the neat sperm sample [Gosálvez et al. 2010; Santiso et al. 2010]. We must therefore consider that the possibility exists that while sperm selection prior to ICSI is efficient at removing DNA damaged spermatozoa, it probably does not remove sufficient spermatozoa harboring apparently sub-lethal DNA damage to increase reproductive outcome.

In our study we have provided evidence that REC in association with sperm density gradient centrifugation may be acting in a synergistic manner to reduce SDF to produce a better sperm sample for use with ICSI. It is important to stress that the net effect for pregnancy under our experimental conditions was achieved after recurrent ejaculation combined with sperm selection plus ICSI. Probably with natural intercourse or intrauterine artificial insemination, the effect of ABS on pregnancy rate would be less, or non-existent. As previously reported by De Jonge et al. [2004], frequent ejaculation increases the percentage of sperm with immature chromatin within 1 day of ejaculation; similarly, Ollero et al. [2001] has demonstrated that most sperm with DNA damage are low density immature spermatozoa that possess residual cytoplasm (cytoplasmic droplets) around the midpiece and which are therefore isolated in the low density layers of the density gradient centrifugation. One possible explanation for the high recovery of sperm with intact DNA in our study is that recurrent ejaculation has resulted in a shift to a more immature population. Nevertheless, this population also contains a proportion, albeit smaller, of mature damaged and non-damaged sperm DNA. Following density gradient centrifugation, the immature spermatozoa (good and bad in terms of DNA quality) are removed, so that the resultant pellet is likely to contain a higher proportion of mature sperm with intact DNA; this then represents a synergistic benefit associated with innate physiology of sperm maturation and the centrifugal properties of the immature sperm cell. In addition and more obviously, recurrent ejaculation reduces the incidence of ‘old’ or degenerating spermatozoa in the cauda epididymidis and the subsequent accompanying negative effects of possible oxidative stress associated with sperm storage. This could be one of the reasons why we are obtaining larger differences in SDF reduction after ABS combined with sperm selection, than when neat and ABS samples without sperm selection are compared [Gosálvez et al. 2011]. Additionally, we must bear in mind that the levels of sperm DNA damage are lower in sperm samples recruited from immature testicular sperm tissues than those detected in ejaculated spermatozoa [Greco et al. 2005; Meseguer et al. 2009]. We do not discard that this fact is also contributing to a partial reduction in the level of sperm containing damaged DNA due to sperm passage acceleration through the epididymis when REC is practiced. While not tested in this experiment, because the system could be very stressful for patients, more intense recurrent ejaculation may produce even greater reduction in the incidence of sperm DNA fragmentation. For example, Gosálvez et al. [2011] has shown that ejaculations three hours apart can result in a massive reduction of SDF by as much as 50% when the first ejaculation is compared with the second ejaculation after sperm selection using a standard gradient centrifugation protocol.

While we are cautious about the use of recurrent ejaculation as a strategy that can be universally applied across all patients to decrease the level of sperm DNA damage, it is nonetheless a simple non-invasive approach that may have synergistic effects with other strategies conducted to decrease the level of sperm DNA fragmentation for ART. From the present experiments, we observed only two major limitations to the use of REC: by men suffering from severe oligozoospermia and by males that experience problems physically performing recurrent erections/ejaculations. We conclude that recurrent ejaculation every 24 hours for four days with a final abstinence of 12 hours, combined with sperm selection using density gradient centrifugation, produces a significant increase in pregnancy rate when using ICSI. As ICSI was the strategy selected for fertilization, we propose that the observed reduction in SDF was the primary factor leading to improved reproductive outcome.

Materials and Methods

This work compares the effects of ABS versus REC on sperm characteristics and involved two sets of patients, an experimental group of 40 couples and a control group of 150 couples; the final rate of pregnancy was compared between these groups. This study was randomized and the criteria to be included in each cohort were: 1) fertilization using ICSI with non-severe male factor and 2) ovodononation with non-severe male factor. Azoospermic, oligospermic, and astenospermic with less than 10% of a + b sperm motility were excluded from this study. All patients in this study consented to their participation according to Spanish legislation and confidentiality and following adherence to Spanish government ethical standards and the internal ethics committee of the clinic (GINEM/RES-01/2010).

Experimental design

The experimental group included 40 males of couples that initially were able to complete an ABS period. The final structure of this cohort consisted of 30 ICSI with no severe male factor and 10 couples participating in ovodonation. The 40 couples in the experimental group proceeded to conduct recurrent ejaculation consisting of one ejaculation each day for 4 d and a 12 h abstinence before the final ejaculation. The final ejaculation was used for analysis of sperm characteristics and represented the seminal characteristics of the patient at the time of fertilization. The sperm characteristics considered in this experiment included volume, sperm concentration, sperm motility, and SDF and they were assessed as depicted in the flow chart diagram (Fig. 1 upper panel for REC and lower panel for ABS in the same patients). Sperm characteristics assessment (SCA) is denoted with open circles in Figure 1. Sperm concentration and motility were assessed with a CASA system (Microptic, Barcelona, Spain) and the sperm DNA fragmentation (SDF) was evaluated with Halosperm (Halotech, SL. Madrid, Spain) on recently ejaculated neat semen samples. For sperm selection prior to ICSI, a density gradient centrifugation using a 80/40 sperm filter gradient (Cryos International, Aarhus, Denmark) was used. Samples were centrifuged at 300g for 20 min and the different fractions aspirated, re-suspended in 2 mL of Sperm Wash medium (Cryos International, Aarhus, Denmark). From the experimental group only 21 patients were able to undergo seminal analysis of all the ejaculations in the protocols in order to compare the sperm values before and after ABS. However, all 40 males from each couple completed the required ejaculatory schedule in order to produce the final (recurrent semen sample) used for ICSI. All these sperm samples were used for ICSI and the final results of pregnancy from this group (30 couples with ICSI and 10 with ICSI plus ovodonation and ICSI) were determined by fetal heart beat measured by ultrasound 5 weeks after embryo transfer. A control group of 150 couples was assessed as a comparison with the experimental group for pregnancy rate using the same proportion of cases (115 ICSI and 35 ovodonation and ICSI) as that produced in the experimental group. The males of the couples in this group engaged in abstinence from 3-4 d prior to ejaculation. This group was generated using all the cycles performed at the clinic during 2011.

For statistical analysis, SPSS v.15.0 for Windows (SPSS Inc., Chicago, IL, USA) was employed. Wilcoxon signed-rank tests for a non-parametric analysis were used to compare two related samples and Spearman Rho for correlation analysis. Observed frequencies of pregnancy in the different experimental conditions were compared using a chi-square incorporating Yates' correction.

Abbreviations

SDF:	=	sperm DNA fragmentation
REC:	=	recurrent ejaculations
ABS:	=	abstinence period
ICSI:	=	intra-cytoplasmic injection
ART:	=	assisted reproductive techniques
SCA:	=	sperm characteristics assessment.

Acknowledgments

The authors thank Prof. Godfrey M. Hewitt and Steve Johnston for critical reading of the manuscript.

Declaration of interest: This work was partially supported by a grant (BFU2010-16738) from Ministerio de Ciencia y Tecnología, Spain (MCYT). The authors report no conflicts of interest.

Author contributions: Conceived and designed the experiments: PS-M, FS-M; Performed the experiments: PS-M, FS-M, MG-M; Analyzed the data: JG; Wrote the manuscript: JG, PS-M.