The expression of human testis‐specific actin capping protein predicts in vitro fertilization outcomes: A novel biomarker of sperm function for assisted reproductive technology

PURPOSE: Sperm function tests do not adequately assess fertilization potential, and new indices are required. We have previously reported that human testis‐specific actin capping proteins may be involved in both sperm morphology and function. This study aimed to determine whether testis‐specific actin capping proteins can be a predictive marker of IVF success. METHODS: Ninety‐seven infertile couples who underwent IVF at an infertility clinic were included. Sperm were immunohistochemically stained to evaluate capping protein expression, and the percentage of sperms with normal staining was calculated. The relationship between actin capping protein expression and IVF outcomes was examined. RESULTS: The couples were divided into four groups according to the percentage of normally expressing actin capping protein as follows: ≥90% Group Ⅰ, 80%–90% Group Ⅱ, 70%–80% Group Ⅲ, and <70% Group Ⅳ. Multiple regression analysis showed a significant trend in fertilization rates across the 4 groups (p for trend =0.008). There was no significant trend in pregnancy rates (p for trend =0.276). CONCLUSION: The human testis‐specific actin capping protein may be a marker of male contributing factors that predict IVF outcomes.