Sperm function and assisted reproduction technology

Abstract

The evaluation of different functional sperm parameters has become a tool in andrological diagnosis. These assays determine the sperm's capability to fertilize an oocyte. It also appears that sperm functions and semen parameters are interrelated and interdependent. Therefore, the question arose whether a given laboratory test or a battery of tests can predict the outcome in in vitro fertilization (IVF). One-hundred and sixty-one patients who underwent an IVF treatment were selected from a database of 4178 patients who had been examined for male infertility 3 months before or after IVF. Sperm concentration, motility, acrosin activity, acrosome reaction, sperm morphology, maternal age, number of transferred embryos, embryo score, fertilization rate and pregnancy rate were determined. In addition, logistic regression models to describe fertilization rate and pregnancy were developed. All the parameters in the models were dichotomized and intra- and interindividual variability of the parameters were assessed. Although the sperm parameters showed good correlations with IVF when correlated separately, the only essential parameter in the multivariate model was morphology. The enormous intra- and interindividual variability of the values was striking. In conclusion, our data indicate that the andrological status at the end of the respective treatment does not necessarily represent the status at the time of IVF. Despite a relatively low correlation coefficient in the logistic regression model, it appears that among the parameters tested, the most reliable parameter to predict fertilization is normal sperm morphology. (Reprod Med Biol 2005; 4: 7-30).

Keywords: assisted reproduction; high intra‐ and interindividual variability; multivariate approach; prediction of outcome of IVF; sperm functions.

Figure 1

Schematic depiction of functional parameters of spermatozoa. Note that the function of capacitation goes together with acrosome reaction and sperm hyperactivation. In addition, chromatin decondensation goes together with the condensation of the sperm DNA material during spermatogenesis and subsequent sperm maturation in the epididymis.

Figure 2

Intra‐ and interindividual variation of (a) sperm concentration, (b) morphology, (c) total motility, and (d) progressive motility of four successive examinations of seven different patients who had no therapy. The high variation of these sperm functions is obvious.

Figure 3

Cumulative number of patients for the percentage of acrosome‐reacted spermatozoa after induction by means of the low‐temperature method of 76 patients (a), and of the acrosin activity index measured by means of the gelatinolysis technique (b) of 110 patients. Patients with a fertilization rate higher than 50% show a normal distribution while those who show poor fertilization (fertilization rate < 50%) are left‐shifted. Arrows indicate the cut‐off points of the tests. Patients with a normal acrosome reaction and normal acrosin activity index, but low fertilization probably have fertilization disorders other than decreased acrosome reaction or acrosin activity. Therefore, only in those cases where the specific test, acrosome reaction or acrosin activity, is abnormally low, male infertility can be attributed to that particular sperm function. For patients where these functional tests were normal, the fertility status has therefore to be regarded as unknown. (▪) Fertilization rate < 50%, (□) fertilization rate > 50%.