Human fertilization success depends on the ability of the spermatozoa to undergo capacitation. Even though this process can be conducted in vitro, the optimal time for a sperm cell to complete capacitation in vitro is still under discussion due to the lack of proper capacitation biomarkers. Here, we evaluated the influence of in vitro capacitation time on HSPA2 distribution over human sperm head testing this chaperone as a potential capacitation biomarker. The chaperone was assessed in human spermatozoa from 16 normozoospermic donors using indirect immunofluorescence in uncapacitated, one and four-hour capacitated spermatozoa. The percentage of HSPA2 immunofluorescent cells before and after one hour of capacitation did not differ significantly. However, after four hours of capacitation, we observed a significantly higher percentage of HSPA2 labelled cells. In fluorescent cells analysed before capacitation, we could not identify a predominant distribution pattern. Meanwhile, after capacitation, most sperm showed a highly labelled equatorial band accompanied by a homogeneous fluorescence throughout the acrosomal region. Our findings suggest that HSPA2 needs more than one hour of in vitro capacitation for being correctly distributed in the anterior region of the sperm head. In conclusion, the present study provides solid evidences for the utility of HSPA2 as a biomarker of human sperm in vitro capacitation. Due to its importance during egg-sperm recognition, the use of HSPA2 as a biomarker before an artificial reproduction technique may be suggested, in addition to a longer capacitation time during sperm preparation.

人类受精的成功取决于精子进行获能的能力。尽管这个过程可以在体外进行，但由于缺乏合适的获能生物标志物，精子细胞在体外完成获能的最佳时间仍在讨论中。在这里，我们评估了体外人类精子头部 HSPA2 分布的获能时间测试该伴侣作为潜在的获能生物标志物。在来自 16 名正常精子供体的人类精子中，使用间接免疫荧光法在无能力、1 小时和 4 小时有能力的精子中评估了伴侣蛋白。获能一小时前后HSPA2免疫荧光细胞的百分比没有显着差异。然而，在四个小时的获能后，我们观察到 HSPA2 标记细胞的百分比显着更高。在获能前分析的荧光细胞中，我们无法确定主要的分布模式。同时，在获能后，大多数精子显示出高度标记的赤道带，伴随整个顶体区域的均匀荧光。我们的研究结果表明 HSPA2 需要一个多小时的体外获能以正确分布在精子头部的前部区域。总之，本研究为 HSPA2 作为人类精子体外获能生物标志物的实用性提供了坚实的证据。由于其在卵-精子识别过程中的重要性，除了在精子制备过程中更长的获能时间外，可能建议在人工繁殖技术之前使用 HSPA2 作为生物标志物。