Intrafollicular injection of nanomolecules for advancing knowledge on folliculogenesis in livestock

Despite the progress in assisted reproductive techniques, there is still a lack of rapid and minimally invasive in situ approaches for further enhancements of female fertility. Therefore, we synthesized clinically relevant liposome nanoparticles for ovarian intrafollicular injection to allow in vivo cellular imaging for future drug delivery, using the mare as an animal model. Ovarian follicles of living mares were injected in vivo with fluorescently labeled liposomes. Samples of the follicular wall (mural granulosa, theca interna, and theca externa), granulosa cells, and follicular fluid were harvested 24 h post-injection through the follicle wall biopsy (FWB), flushing, and aspiration techniques, respectively, using a transvaginal ultrasound-guided approach. In parallel, post-mortem dissected, and cultured porcine antral follicles were microinjected with doxorubicin-encapsulated liposomes to assess intracellular delivery potential. All injected mare and pig follicles were macroscopically healthy, and fluorescence imaging revealed successful intrafollicular binding to mural granulosa cells and progressive migration of liposomes to other follicle cell layers (theca interna, and theca externa), regardless of the follicle size. Intracellular delivery of doxorubicin was confirmed in all porcine follicle wall cell types. We conclude that the intrafollicular injection of nanomolecules is a promising approach for real-time monitoring of intrafollicular processes and potential utilization of in vivo cellular drug delivery to assist in follicle disease treatments and fertility improvement.