L'irradiation des spermatozoïdes au laser HeNe à faible énergie chez la souris et chez l'homme

INTRODUCTION. The effects of low energy He-Ne 630 laser (LEL) irradiation on various aspects of cell metabolism, including proliferation, respiration, ATP synthesis and Ca²⁺ uptake, have been recently recognized in somatic cells, animal spermatozoa and embryonic cells. OBJECTIVES. 1- To analyze the in vitro effects of LEL irradiation on the mouse IVF model. 2- To assess the effects of experimental LEL irradiation on human spermatozoa in the sperm-zona free hamster egg penetration (SPA) model. MATERIAL & METHODS. 1- In a mouse IVF model, pooled oocytes were incubated for 24 h. with LEL-irradiated and non-irradiated epididymal mouse spermatozoa. The percentage of fertilized eggs, intracellular Ca²⁺ and Ca²⁺ uptake as well as the effects of reactive oxygen scavengers were compared in the two groups. 2- In the enhanced SPA model, with overnight TEST-Yolk preincubation, LEL-irradiated and non-irradiated ejaculated spermatozoa from 43 infertile men were incubated for 3 h with fresh zona-free hamster eggs. The percentage of eggs penetrated (SPA%) by irradiated or control sperm was compared. Acrosome reaction (AR) and Hemizona Assay (HZA) were also performed on the same ejaculates. RESULTS. 1- In mice, brief LEL irradiation enhanced intracellular Ca²⁺ influx and increased the in vitro fertilization capacity of spermatozoa. Mitochondrial Ca²⁺ transport mechanisms and H₂O₂ appeared to be involved in these LEL effects. 2- In the 43 male patients, AR and SPA were correlated, while SPA and HZA were poorly correlated. In the whole group, the mean SPA% of LEL-irradiated and control sperm were not significantly different: 49.8 ± 39.9 and 51.0 ± 34.9, respectively. No significant change was observed in 50% of cases. Following irradiation, SPA% increased in 25% of cases and decreased in 25% of cases. However, classifying all cases according to the SPA cut-off point of 30% as poor and good sperm in this enhanced SPA model, showed that LEL irradiation significantly increased SPA% only in the poor sperm subgroup (n=16) from 5.5 ± 8.9 to 23.1 ± 25.2 (p<0.0001). This increase was observed in 50% of these patients. In the good sperm category (n=27), no improvement of SPA% was observed. On the contrary, LEL irradiation decreased SPA% from 76.1 ± 24.4 to 67.6 ± 28. CONCLUSION. In a mouse IVF model, LEL irradiation of spermatozoa improved intracellular Ca²⁺influx and egg fertilization. H₂O₂ seems to participate in the biochemical cascade transforming light signals into a biological response. In man, using the SPA model, LEL sperm irradiation might improve the penetration capacity only in the case of poor quality sperm, by increasing sperm egg penetration in one half of cases, otherwise LEL is ineffective. Further studies are required to confirm these results, but LEL should not be considered for clinical use until its safety has been proven. (Supported by grants from the Chief Scientist Office, Ministry of Health).