In vitro development of domestic cat embryos following intra-cytoplasmic sperm injection with testicular spermatozoa

The objective was to assess the ability of testicular spermatozoa to fertilize in vitro matured domestic cat oocytes and support blastocyst formation in vitro following intra-cytoplasmic sperm injection (ICSI). After IVM, oocytes were randomly and equally allocated among treatment groups (ICSI with testicular spermatozoa, ICSI with ejaculated spermatozoa, sham ICSI, and control IVF). At 18 h after either injection or insemination, the percentage of fertilized oocytes (per total metaphase II oocytes) was ∼65% after ICSI with testicular or ejaculated spermatozoa (P > 0.05), which was less (P < 0.05) than control IVF (∼90%). On Day 7, the percentage of cleaved embryos (per total metaphase II oocytes) was ∼60% after ICSI with testicular or ejaculated spermatozoa (P > 0.05), which also was less (P < 0.05) than control IVF (∼85%). After ICSI with testicular spermatozoa, the percentage of blastocysts (per total cleaved embryos) was ∼11.0%, which was less (P < 0.05) than ICSI with ejaculated spermatozoa (∼21.0%); the latter was less (P < 0.05) than control IVF (∼43.0%). No blastocyst formation was observed after sham ICSI. For the first time in the domestic cat, this study demonstrated the fertilizing ability and developmental potential of intra-testicular spermatozoa delivered directly into intra-ovarian oocytes matured in vitro.