A simple method for assessing hyaluronic acid production by cumulus-oocyte complexes

Abstract

The cumulus expansion of cumulus-oocyte complex (COC) is an essential regulating process of oocyte maturation and as such it is a possible biomarker of the in vitro maturing oocytes quality. Cumulus expansion is usually assessed by non-invasive methods based on visual evaluation with many inaccuracies. On the other hand, analytical measurement of the quantity of hyaluronic acid (HA), the most abundant compound of expanded cumuli, is one of possible methods to evaluate cumulus expansion precisely. Therefore, this study aimed to verify the applicability of HA analysis for evaluating the cumulus expansion and testing oocyte maturation. The COCs were cultured in modified M199 medium for 8-48 h. The samples for the HA analysis were prepared on an 8-hour time scale, and HA retained in COCs was measured using a spectrophotometric method adapted for this purpose. We observed an increasing quantity of HA during the in vitro cultivation. A comparison with expanded COCs' classification or expansion area proved the proposed method of HA analysis suitable for the evaluation of cumulus expansion in vitro. Our findings consider the quantity of HA-expressed cumulus expansion to be a valuable marker of COC quality enabling an adequate oocyte meiotic stage estimation.

Keywords

• oocyte
• meiotic maturation
• cumulus expansion
• glycosaminoglycans
• spectrophotometry