Antigenicity of Frozen and Fresh Spermatozoa**Publication No. 943 from the Oregon Regional Primate Research Center. Supported by National Institutes of Health Grant RR00163 and Northwestern University/PARFR Subcontract 7ON under Subcontract AID/csd-3608

Sperm immobilization test and quantitative sperm immobilization test using frozen-thawed sperm preparation applied with computer-aided sperm analysis

PURPOSE

In a previous study, a new method was described using the sperm immobilization test (SIT) with computer-aided sperm analysis (CASA). However, obtaining high-quality sperm as needed was a known issue. Here, we compared the results of using frozen-thawed sperm and fresh sperm for the SIT using the CASA method.

METHODS

For the frozen-thawed preparation, 500 μL of condensed semen and 500 μL of Sperm Freeze were mixed in a cryovial and cryopreserved in liquid nitrogen. Density gradient centrifugation was used for the collection of motile sperm in both the fresh and frozen-thawed sperm preparations. A total of 50 serum samples were prepared for both the fresh and frozen-thawed sperm with each sample tested containing 10 μL of serum, 1 μL of either fresh or frozen motile sperm suspension, and 2 μL of complement. Sperm motilities were measured using CASA after a 1-hour incubation period for both fresh and frozen-thawed sperm.

RESULTS

Both fresh and frozen-thawed sperm reacted similarly when exposed to serum containing sperm-immobilizing antibodies asserting the use of frozen-thawed sperm for the diagnosis of immunological infertility.

CONCLUSION

These results suggest the possibility of using cryopreserved sperm for the SIT when fresh sperm is unavailable.

Effect of freezing-thawing on the expression of mannose-ligand receptors on human spermatozoa: the impact on sperm capacitation and acrosome reaction

The aim of this study was to evaluate the change in the expression of mannose-ligand receptors following a freezing-thawing procedure, in order to assess its impact on sperm capacitation and acrosome reaction. Twenty semen samples were obtained from fertile donors. Sperm samples were divided into two equal volumes. One aliquot was cryopreserved and the other aliquot was incubated at 32 degrees C. After 2 h the frozen sample was thawed and both samples were further incubated at 32 degrees C to allow capacitation. Mannose receptors were examined following 4 and 22 h of incubation using a mannosylated-BSA-FITC probe. The expression of mannose-ligand receptors on the sperm plasma membrane was determined according to the fluorescence pattern: pattern I represents pre-capacitation, pattern II represents capacitated spermatozoa and pattern III represents acrosome-reacted spermatozoa. After 4 h incubation in capacitating medium, the percentages of patterns I, II and III were 90, 7 and 3% for fresh spermatozoa and 89, 8 and 3% for frozen-thawed spermatozoa, respectively (P > 0.05). Following 22 h of incubation, the percentages of patterns I, II and III were 84, 11 and 5 for fresh spermatozoa and 83, 11 and 6% for frozen-thawed spermatozoa, respectively (not significant at P > 0.05). The percentages of patterns II and III in fresh and frozen-thawed spermatozoa were increased by the same magnitude with longer incubation in the capacitating conditions. It was concluded that the freezing-thawing procedure for human spermatozoa does not affect the expression of mannose-ligand receptors and the dynamics of sperm pre-fertilization processes.

Cryopreservation of human semen

A review is given of the techniques for the cryopreservation of human semen, including the preparation of cryoprotective media, the use of ampoules, straws, and pellets, and freezing and thawing techniques. The use of cryopreserved semen for therapeutic artificial insemination by donor is described. The advantages of cryopreserved semen over fresh donor semen mostly lie in the ability to exclude infections before use and the extra convenience, in spite of the lower success rate and increased cost. The recovery of sperm motility on thawing is described, as are other methods for assessing the degree of damage to the spermatozoa by the freezing procedure. The success rates reported by large semen banks are summarized.

Antigenicity of sperm cells after freezing and thawing

Freezing and thawing is thought to result in removal of spermatozoal membrane antigens. We investigated the presence of sperm antigens before and after freezing and thawing by means of the immunoperoxidase assay (IPAMA), sperm immobilization test (SIT), and separation of proteins by gel electrophoresis. The results of the IPAMA and SIT assays showed no difference in the membrane antigens before and after freezing and thawing. Analysis of surface proteins by gel electrophoresis demonstrated that freezing and thawing did not remove any particular group of proteins from the surface membrane of spermatozoa. According to the evidence of the three tests performed, there is no meaningful removal of antigens from the sperm cell surface membrane by the process of freezing, preservation, and thawing when carried out by the specific methods used. This work does not support the suggestion that in cases of immunologic incompatibility between spermatozoa and cervical mucus it would be possible to overcome the couple's infertility by employing the process of freezing, preservation, and thawing.