The effect of preincubation of human spermatozoa in milk on sperm penetration into zona-free hamster oocytes and on sperm binding to the human zona pellucida

Ooplasmic injections of rabbit round spermatid nuclei or intact round spermatids from fresh, cryopreserved and cryostored samples

We compared the outcome of ooplasmic round spermatid nuclear injections (ROSNI) versus intact round spermatid injections (ROSI). Rabbit round spermatid nuclei and intact round spermatids were recovered and injected into rabbit oocytes (groups A and B, respectively). Fertilization, cleavage and embryonic development rates were compared. In additional studies, five protocols for cryopreservation of round spermatids and two protocols for cryostorage of round spermatids were applied. The outcome of ROSNI techniques using frozen-thawed or cryostored-warmed round spermatids was evaluated. The cleavage rate and the overall morula plus blastocyst development rate were significantly larger in group A than group B. ROSNI procedures are superior to ROSI techniques in the rabbit. The largest fertilization, cleavage and embryonic development rates after ROSNI techniques using cryopreserved or cryostored round spermatids were demonstrated in groups of round spermatids in which a mixture of seminal plasma plus test yolk buffer was employed as an extender, and dimethyl sulphoxide plus a high concentration of glycerol served as cryoprotectants. It appears that the seminal plasma contains factors protecting round spermatids during cryopreservation or cryostorage, and/or the employment of two cryoprotectants has a beneficial role in the maintenance of round spermatid reproductive capacity.

Milk versus TEST-yolk--preincubated sperm; in vitro fertilization outcome

OBJECTIVE

Preincubation of sperm in TEST-yolk medium enhances in vitro fertilization (IVF) outcome. However preincubation of sperm in milk at 5 degrees C enhances the results of sperm penetration assay and hemizona assay. This study was therefore performed to determine the influence of milk on in vitro fertilization rate of human oocytes, as compared with TEST-yolk medium.

STUDY DESIGN

Forty-one consecutive couples undergoing an IVF procedure were randomized. Of these 20 couples were admitted for the milk study (group 1) and 21 couples for the TEST-yolk study (group 2). Each ejaculate was Percoll-processed and the sperm pellet was resuspended in 0.5 ml of culture medium. An equal volume of heat-inactivated homogenized cow's milk (95 degrees C, 10 min) was added to sperm suspension from group 1 and an equal volume of TEST-yolk medium was added to sperm suspension from group 2. After 2 h of incubation at 5 degrees C and washing with culture medium at 37 degrees C, oocytes were inseminated. Oocytes from group 1 couples were inseminated with milk-treated spermatozoa and those from group 2 couples with yolk-treated spermatozoa. Oocytes were evaluated for fertilization after 18 h.

RESULTS

Sperm preincubated in milk fertilized 75 out of 100 mature oocytes (75%). TEST-yolk-treated sperm fertilized 45 out of 64 mature oocytes (70%). The difference was not statistically significant.

CONCLUSIONS

Preincubation of spermatozoa in milk, as compared with preincubation in TEST-yolk medium yields a similar IVF outcome, so milk may be a suitable alternative medium for preincubation of spermatozoa to enhance its fertilizing potential.

Effect of milk-yolk on the fertilizing capacity of spermatozoa

Pre-incubation of human sperm in egg yolk based medium (TEST-yolk) as well as milk have been shown to improve sperm fertilizing capacity. The purpose of this study was to compare a combination of these two media, called milk-yolk, against the two established media, in order to test for a possible synergistic effect(s) on sperm functions as measured by sperm motility, acrosome reaction and penetration assay. Statistically, no differences have been observed among the three media, except for SPA outcome in milk-yolk, being significantly lower than the corresponding values for the other two media. In conclusion the beneficial effects of egg yolk and milk appear to be eliminated once both media are combined, resulting in an antagonistic effect on the fertilizing capacity of the spermatozoa.