FGF2, LIF, and IGF1 supplementation during in vitro maturation or culture improves equine ICSI embryo development in...

Ovum pickup (OPU) combined with intracytoplasmic sperm injection (ICSI) has reshaped equine assisted reproduction, enabling embryo production from mares and stallions with constrained breeding opportunities; however, limited efficiency of in vitro maturation (IVM) and in vitro culture (IVC) continues to hinder embryo production. Growth factor supplementation with fibroblast growth factor 2 (FGF2), leukemia inhibitory factor (LIF), and insulin-like growth factor 1 (IGF1) in combination (FLI) has been shown to enhance oocyte and embryo developmental competence in several species.

This study evaluated whether FLI supplementation during IVM or IVC improves developmental outcomes of equine ICSI embryos and whether responses are influenced by donor mare age.

Oocytes were assigned to IVM with or without FLI or cultured post-ICSI in IVC media with or without FLI. Developmental outcomes, including maturation, cleavage, blastocyst formation, blastocyst diameter, and pregnancy establishment, were assessed across defined donor-mare age categories.

FLI supplementation did not affect overall maturation or cleavage rates. Blastocyst formation was significantly increased only in oocytes from middle-aged mares when FLI was added during either IVM or IVC. Supplementation during IVC also increased blastocyst diameter. Pregnancy establishment to Day 45 was marginally higher for embryos derived from FLI-treated oocytes, particularly following vitrification.

These findings showed age-dependent responses to FLI, with the greatest benefit in middle-aged mares, supporting further molecular studies of its developmental effects.

These results indicated that FLI supplementation can be incorporated into equine OPU-ICSI systems to improve clinical embryo production outcomes, particularly for middle-aged donor mares.