Inter-alpha-trypsin inhibitor is concentrated in the pericellular environment of mouse granulosa cells through hyaluronan-binding

Abstract

Objective: The binary complex involving hyaluronan and inter-alpha trypsin inhibitor (ITI) is an important component of the cumulus oocyte complex. The aim of this study is to investigate the physiological association between ITI and its derivatives and hyaluronan or its binding protein (HABP). Study Design: ITI and its derivatives (heavy chains of ITI and urinary trypsin inhibitor, UTI) were tested for their ability to interact with hyaluronan or HABP. HABP was used to locate the distribution of hyaluronan in mice ovaries. Result: ITI and heavy chains of ITI, but not UTI, could specifically bind to immobilized hyaluronan. Furthermore HABP could specifically bind immobilized hyaluronan with high affinity, and also to immobilized ITI and its derivatives. 6 h after the injection of human chorionic gonadotropin, the hyaluronan staining in the preovulatory ovaries displayed a heterogenous appearance in which the most intense stainings were observed in cumulus oocyte complex. The distribution of ITI was found to be similar to that of hyaluronan. Conclusion: The hyaluronan binding sites of ITI are located in the heavy chains of this molecule. ITI is concentrated in the pericellular environment of granulosa cells through hyaluronan-binding. The altered amount of hyaluronan and ITI in the preovulatory ovaries may contribute to their important clinical characteristics including cumulus oocyte complex expansion.