Heparin and Progesterone Exert Synergistic Effects to Improve the In-Vitro Fertilization Rate of Bovine Sperm Bound to Oviduct Cell Aggregates from the Isthmus

SIMPLE SUMMARY: After mating, sperm starts its long journey with the ultimate goal of fertilizing the oocyte. Inside the oviduct, sperm is attached to the surface of epithelial cells. The intact and good-quality sperm are elected and stored. Many infertility-related problems are related to the short life span of the sperm and/or the delay of the capacitation process of sperm attached to the oviduct. Thus, the elongation of the life span of the sperm would be very helpful in overcoming such problems. We hereby aimed to evaluate the fertilization ability of sperm that bind to cell aggregates oviduct (infundibulum-ampulla-isthmus), and assess the effect of heparin and or progesterone on the in-vitro fertilization ability of sperm co-incubated with isthmus cells aggregates. The sperm bound to isthmus aggregates improved the rate of in-vitro fertilization compared to infundibulum and ampulla. Moreover, pre-treatment of mature oocytes with heparin and progesterone plays a coactive role that improves the in-vitro fertilization of sperm bound to cell aggregates from isthmus. In conclusion, binding to isthmus aggregates improves the in-vitro fertilization of bovine sperm. Additionally, heparin together with progesterone, exerts a synergistic action that improves the in-vitro fertilizing potential of sperm attached to isthmus aggregates. ABSTRACT: After the copulation process, some sperm start the long journey with an ultimate goal of fertilizing the oocyte. Inside the oviduct, sperm are stored, waiting for the ovulated oocyte where they bind to the apical surface of the oviduct cells, which in turn hold sperm to form a sperm nest. The essential functions of the sperm reservoir include attaching spermatozoa to oviduct epithelial cells, selecting intact, good-quality sperm with an end result of extending sperm life expectancy. The current study aimed to evaluate the fertilization ability of sperm that bind to cell aggregates from different parts of the oviduct (infundibulum-ampulla-isthmus), and to assess the effect of heparin and or progesterone (P4) on the in-vitro fertilization ability of sperm co-incubated with cell aggregates from the isthmus. In-vitro fertilization was identified as a cleaved oocyte to two cells or more. The sperm bound to cell aggregates from the isthmus improved the rate of in-vitro fertilization (48.09%) compared to aggregates from the infundibulum (36.90%) and ampulla (37.61%). Moreover, pre-treatment of mature COCs with heparin (40 μg/mL) and P4 (80 nanomolar) play a coactive role that improves the in-vitro fertilization ability of sperm bound to cell aggregates from isthmus (63.33%), compared to 42.61% in the absence of cells aggregates. In conclusion, binding to cell aggregates from isthmus improves the in-vitro fertilization ability of Bovine sperm. Additionally, heparin, together with P4, exerts a synergistic action that improves the in-vitro fertilizing potential of sperm attached to cell aggregates from the isthmus of the bovine oviduct.