52 USE OF TRANSWELL CELL CULTURE AND 3-DIMENSIONAL PRINTING TECHNOLOGY TO DEVELOP AN IN VITRO BOVINE OVIDUCT

Abstract

Oviduct epithelial cells (OECs) generate the microenvironment for mammalian fertilization. When cultured in vitro OECs rapidly lose their differentiated cell properties (e.g. secretory activity and cilia), while suspended cells have a limited lifespan. These limitations, likely due to the lack of folded tubular geometry of the oviduct, prompted us to combine transwell cell culture and 3-D printing technologies to mimic the in vivo OEC niche in order to better study the unique role of the oviduct and its microenvironment during the processes of fertilization and early embryonic development. U-shape inserts were 3-D printed using a multi-arm acrylate-based resin (PIC100) on an Envisiontec Perfactory P3 stereolithographer. Post-printing treatments of custom-made tubular transwell inserts were first tested in order to determine any possible negative impact of the plastics on cell growth. Inserts were either untreated, post-cured with 1000 flashes/side (Otoflash, 66 W), post-cured and Soxhlet-extracted overnight in isopropanol, or post-cured and Soxhlet-extracted over the weekend in water at 37°C. The post-cured and Soxhlet-extracted overnight in isopropanol inserts were selected as best pretreatment for culturing OECs. These inserts were mounted with track-etched PET membranes (12 µm thick, 0.4 µm pore diameter) to create a U-shape geometry that allows perfusion. Bovine OECs were obtained by squeezing the whole oviduct collected from slaughterhouse cows (on luteal phase) and cultured as monolayers for 7 days (n = 2 cows). These de-differentiated OECs were seeded on the membranes, grown to confluence (7 days), and cultured (1) at an air-liquid interface for 6 and 14 days (air-liquid culture) or (2) under perfusion (6 mL h^–1) for 6 days (perfusion culture). OECs were also cultured on coverslips as monolayers (2-D culture) for 6 and 14 days. After this period, the OECs were fixed and immune labelled to determine their polarized state. Polarization of OECs (laminin and primary cilia detection) was observed on Day 6 for perfusion culture, on Day 14 for air-liquid culture, and was not detected in 2-D culture. The presence of secondary cilia (acetylated α-tubulin) was observed in 6% of the cells cultured under perfusion at Day 6; secondary cilia was not present in air-liquid or 2-D cultures during the period analysed. In conclusion, post-curing and Soxhlet extraction of leachable compounds is crucial to avoid toxic effects on cell growth. The U-shape custom-designed inserts are able to create a tube-like surface in which bovine oviducal cells can be cultured to confluency and thereafter repolarize (presence of primary cilia and detection of laminin); this polarization occurs faster when the U-shape culture is under perfusion. Further studies will examine the ability of the cells to differentiate further (development of secondary cilia and secretory ability) and support in vitro fertilization. To this end, 3-D designs will be tested to determine their use for live cell imaging and for collecting secreted fluids.