Functional significance of cumulus expansion in the mouse: Roles for the preovulatory synthesis of hyaluronic acid within the cumulus mass

TLDR

Gonadotropin‑stimulated expansion of the mouse cumulus oocyte complex in vitro, measured by a quantitative videographic method, matches the expansion seen in vivo when the medium contains porcine FSH, fetal bovine serum, and either 2.5 mM glucosamine or optimal glutamine and glucose concentrations. The study aimed to investigate how cumulus expansion influences fertilization rates and the maintenance of fertilizability during in‑vitro culture. A quantitative videographic assay was used to monitor cumulus expansion under various supplement conditions, and the effect of the glucosamine‑synthesis inhibitor 6‑diazo‑5‑oxo‑1‑norleucine (DON) was examined both in vitro and by intraperitoneal injection. Cumulus expansion was markedly reduced without glucosamine, completely blocked by DON, and its extent positively correlated with fertilization success; removal or loss of the cumulus led to loss of fertilizability, and DON injection inhibited follicular expansion and suppressed ovulation. © 1993 Wiley‑L.

Abstract

Abstract Gonadotropin‐stimulated expansion of the mouse cumulus oocyte complex (COC) in vitro, measured with a quantitative videographic method, is comparable to that observed to occur in vivo when medium is supplemented with porcine follicle stimulating hormone (pFSH), 10% fetal bovine serum (FBS), and 2.5 mM glucosamine or optimal concentrations of glutamine and glucose. In the absence of glucosamine, the volumetric expansion of COCs in vitro is never more than 25% of that occurring in its presence. The addition of 6‐diazo‐5‐oxo‐1‐norleucine (DON), an inhibitor of glucosamine synthesis to medium supplemented with glutamine and glucose, completely inhibits cumulus expansion in vitro. This system was utilized to examine the relationship between cumulus expansion and fertilization rates, and the maintenance of fertilizability in culture. Successful fertilization (as determined by development to the 2‐cell stage) was correlated with the quantity and quality of the expanded cumulus mass, and conversely, the spontaneous loss or mechanical removal of the cumulus was correlated with a loss of fertilizability following additional incubation in culture medium. In addition, the i.p. injection of DON inhibited cumulus expansion within the intact follicle and suppressed ovulation. © 1993 Wiley‐Liss, Inc.