Hyaluronic acid binding by human sperm indicates cellular maturity, viability, and unreacted acrosomal status

Objective: To test, both in semen and washed-sperm fractions, whether hyaluronic acid (HA) binding is restricted to sperm that have completed cellular maturation. Design: Comparisons of sperm in semen and in HA-bound sperm fractions. Setting: University-based diagnostic and research andrology laboratory. Patient(s): Semen samples originated in men being tested for infertility. Intervention(s): The attributes of sperm maturity were tested by immunocytochemistry with creatine kinase and HspA2 antisera (highlights cytoplasmic retention in diminished-maturity sperm), aniline blue chromatin staining (detects persistent histones), pisum sativum lectin staining (reveals acrosomal integrity), and the FertiLight viability kit (highlights viable and nonviable sperm). Result(s): All markers of sperm maturity and immaturity supported the hypothesis that HA-bound sperm are mature. Nonbinding sperm exhibited cytoplasmic and nuclear properties of diminished maturity. The acrosomal status of HA-bound sperm was either unreacted or slightly capacitated, but not acrosome reacted. Only viable sperm exhibited HA binding. Conclusion(s): Sperm that are able to bind to HA are mature and have completed the spermiogenetic processes of sperm plasma membrane remodeling, cytoplasmic extrusion, and nuclear histone-protamine replacement. Hyaluronic acid-bound sperm show unreacted acrosomes. These studies provide further insights into the relationship between spermiogenesis and sperm function.