Fertilization of human oocytes in vitro by spermatozoa from oligozoospermic and normospermic men

Semen parameters on the day of oocyte retrieval predict low fertilization during conventional insemination IVF cycles

PURPOSE

Poor fertilization during conventional IVF is difficult to predict in the absence of abnormal semen parameters; large-scale studies are lacking. The purpose of this study is to evaluate factors associated with low fertilization rates in conventional insemination IVF cycles.

METHODS

A retrospective cohort study evaluating demographic, reproductive evaluation, and IVF cycle characteristics to identify predictors of low fertilization (defined as 2PN/MII ≤ 30% per cycle). Participants were included if they were undergoing their first IVF cycle utilizing fresh autologous oocytes and conventional insemination with male partner's sperm (with normal pretreatment semen analysis). They were randomly divided into a training set and a validation set; validation modeling with logistic regression and binary distribution was utilized to identify covariates associated with low fertilization.

RESULTS

Postprocessing sperm concentration of less than 40 million/ml and postprocessing sperm motility < 50% on the day of retrieval were the strongest predictors of low fertilization in the training dataset. Next, in the validation set, cycles with either low postprocessing concentration (≤ 40 million/ml) or low postprocessing progressive motility (≤ 50%) were 2.9-times (95% CI 1.4, 6.2) more likely to have low fertilization than cycles without either risk factor. Furthermore, cycles with low postprocessing concentration and progressive motility were 13.4 times (95% CI 4.01, 45.06) more likely to have low fertilization than cycles without either risk factor.

CONCLUSIONS

Postprocessing concentration and progressive motility on the day of oocyte retrieval are predictive of low fertilization in conventional IVF cycles with normal pretreatment diagnostic semen analysis parameters.

The postwash total progressively motile sperm cell count is a reliable predictor of total fertilization failure during in vitro fertilization treatment

OBJECTIVE

To predict the chance of total fertilization failure (TFF) before the day of ovum pickup with known semen and female variables.

DESIGN

A statistical model was constructed to predict TFF by retrospective analysis (2,366 couples) and subsequently tested on a new IVF population (917 couples).

SETTING

Academic tertiary referral center.

PATIENT(S)

Three thousand three hundred eighty-three couples who underwent an IVF-ET treatment.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The ability to predict the probability of TFF in IVF.

RESULT(S)

Two variables-postwash total progressively motile sperm cell count (postwash TPMC) and number of follicles-were found to be significant. Taking a probability of 25% as an acceptable risk of TFF, we calculated that a postwash TPMC of <1.1 x 10(6) cells results in a risk of TFF of >25%. Low responders (<4 follicles) needed a postwash TPMC of >2.2 x 10(6) cells to reduce the risk of TFF to <25%. High responders (>15 follicles) needed only 0.35 x 10(6) postwash progressively motile spermatozoa.

CONCLUSION(S)

When postwash TPMC and number of follicles are known and an unacceptable TFF outcome is expected, one can propose an ICSI procedure a few days before the day of ovum pickup.

Sperm count in ejaculates and after sperm selection with discontinuous percoll gradient centrifugation technique, as a prognostic index of IVF outcome

Success of IVF with low sperm count will depend on the retrieval of the maximum number of normal motile sperms, and this makes the selection of an appropriate technique critical. Various in vitro methods have been developed for selecting human sperm cells. Sperm selection using percoll gradient has been reported to yield upto 60% motile and morphologically normal spermatozoa from a normal semen sample. In this study, we have attempted to determine a possible relationship between sperm count in ejaculates before and after selection with percoll gradient centrifugation on one hand, and fertilization, cleavage and pregnancy rates in an IVF program on the other. With increased sperm count at the time of IVF treatment using selected sperm, we observed higher fertilization, cleavage and gestational rates. In conclusion, sperm concentration before and after selection with percoll may be considered a prognostic parameter for the determination of fertilization potential and pregnancy rates in an IVF program.

Actions of progesterone on human sperm: a model of non-genomic effects of steroids

Non-genomic actions of steroids have been extensively studied in the last few years. Among these actions, the non-genomic effect of progesterone (P) on human spermatozoa appears to be very promising, in view of the dramatic effect of this steroid on intracellular calcium, activation of tyrosine kinase, and induction of acrosome reaction. We have shown that the ability of spermatozoa to respond to P increases during the process of capacitation and is not counteracted by the P-receptor antagonist RU486 nor by the GABAA antagonists bicuculline and picrotoxin. We have also shown that P increases tyrosine phosphorylation of a sperm protein of about 97 kDa, suggesting activation of tyrosine kinase(s). In addition, we found that P induces a perturbation of sperm membrane phospholipid metabolism resulting in an increase of synthesis of platelet-activating factor and liberation of arachidonic acid. Results of these biochemical studies indicate that P is able to stimulate several signal transduction pathways in human sperm. We have also investigated responsiveness to P in sperm of oligozoospermic subjects as well as of men undergoing an in vitro fertilization (IVF) program. Our results show that the percentage increases of intracellular calcium and acrosome reaction in response to P is significantly reduced in oligozoospermic men as well as in subjects with reduced fertilization rate. Moreover, in the latter subjects response to P is highly significant correlated to fertilization rate of oocytes. These studies indicate that a biochemical alteration of sperm in their capacity to respond to P might be responsible for reduced fertilizing ability.

Use of human zonae from cryopreserved oocytes in a test to assess the binding capacity of human spermatozoa

Aged unfertilized oocytes from an assisted conception programme were cryopreserved and then utilized after thawing in a zona-binding assay. Oocytes frozen using dimethyl sulphoxide (DMSO) showed poor survival post-thaw (2/40, 5%) compared to those frozen with propanediol (PROH) (63/134, 47%). When the zonae were exposed to spermatozoa from fertile donors, those frozen with DMSO showed a significantly higher number of bound spermatozoa than did those frozen with PROH (P < 0.002). In both groups, oocytes which failed to survive the freeze-thaw processes had greater numbers of bound spermatozoa than did those which survived (P < 0.05). Oocytes from cases of failed fertilization showed no difference in their rate of sperm binding compared with oocytes from cases in which some fertilization had occurred. Zonae frozen in PROH but which were from oocytes which were not viable after thawing were used to assess the binding of spermatozoa from men who had failed previously to fertilize their partner's oocytes in vitro and spermatozoa from men with poor quality semen and who had elected for treatment by micro-injection sperm transfer. The number of spermatozoa bound to zonae was reduced significantly in both groups compared to a fertile donor.

Treatment of severe male-factor infertility with high concentrations of motile sperm by microinsemination in embryo cryopreservation straws

A microinsemination technique was evaluated for treating our program's most severe cases of male-factor infertility. Oocytes were inseminated with high concentrations of motile sperm (1 to 9 x 10(6)/ml) in 10 to 150 microliters within embryo cryopreservation straws. Fertilization was obtained in 20 of 29 (69%) couples treated by this technique. In the 15 patients in which only embryos generated from the straw technique were transferred, 7 clinical pregnancies resulted (46.7% per transfer). The implantation rate for couples receiving embryos from the straw technique only (12/58; 20.7%) compared favorably to that observed for other cases treated during this same time period with regular insemination techniques (111/766; 14.5%). Clinical pregnancy rates per transfer for IVF-ET, TET, and PROST were 33.0% (1/3), 0% (0/2), and 60.0% (6/10), respectively. The percentage of polyploidic embryos was significantly lower (P less than 0.0001) for male-factor patients treated by the straw technique with high sperm concentrations than for non-male-factor patients treated during this same time period with standard sperm concentrations. Normal births have resulted from straw inseminations with 3.4 x 10(6) and ongoing pregnancies with 5.0 x 10(6) motile sperm/ml. The results of this study suggest that some cases of male-factor infertility can be successfully treated by insemination with high concentrations of motile sperm in embryo cryopreservation straws. A technique of centrifuging sperm in straws was also developed to concentrate the entire fraction of washed sperm into 10 microliters. Further development of this technique may allow treatment of more severe cases of oligo/asthenospermia by microinsemination with high concentrations of motile sperm than is presently possible with standard washing techniques.

Cryopreservation of human embryos at the pronucleate, early cleavage, or expanded blastocyst stages

Supernumerary embryos following treatment by IVF or GIFT were cryopreserved at the pronucleate, early cleavage or expanded blastocyst stages. The success of embryo cryopreservation at these stages was evaluated in terms of (i) the proportion of embryos surviving the freeze/thaw procedure; (ii) the proportion of patients reaching embryo replacement; and (iii) the incidence of pregnancy per replacement. Significantly more embryos survived when frozen/thawed at the pronucleate (44/61; 72%) or early cleavage stages (48/80; 60%), than at the expanded blastocyst stage (13/34; 38%). A significantly higher proportion of patients had embryo replacements when embryos were frozen/thawed at the pronucleate (17/19; 89%) or early cleavage stages (21/24; 88%), than at the expanded blastocyst stage (9/17; 53%). Following replacement of frozen/thawed pronucleate and early cleavage stage embryos, clinical pregnancy rates of 8/17 (47%) and 3/21 (14%) clinical pregnancies were achieved, respectively. No pregnancies were achieved following replacement of frozen/thawed expanded blastocysts.

A guide to upwardly mobile spermatozoa

Morphological comparison of sperm in raw ejaculates and swim-ups showed that the swim-up process does not simply increase the proportion of 'normal' sperm. Rather, sperm of specific morphologies have characteristic grades of upward motility.