iAT2s spheroids are a powerful tool for modelling patient specific disease phenotypes. However, the extra-cellular matrix (ECM) used in their production, Matrigel is mouse derived, varying in composition from lot to lot, leading to heterogeneous spheroids. Synthetic hydrogels may serve as alternative ECMs with customisable physiochemical properties. The Rastrum 3D-bioprinting system incorporates synthetic ECMs to deposit cells consistently, producing homogenous spheroids.

In this experiment we investigated if iAT2 spheroids could be bio-printed and maintain similar growth and phenotypic markers seen in Matrigel grown spheroids.

A ECM was designed incorporating fibronectin, laminin, collagen IV and hyaluronic acid with a stiffness of 0.7 KPa. A single cell suspension of iAT2s, carrying a tdTomato reporter for surfactant protein C, was resuspended in the Rastrum cartridge or in Matrigel. As seeding density is crucial for iAT2 growth and phenotype maintenance, cells were seeded at 3 densities, 500, 1,000 and 5,000 cells/ml in 7.2ml (Rastrum) and 8ml (Matrigel) droplets in a 96-well plate.

After 2 weeks Spheroid formation and growth was observed at all seeding densities in the Matrigel iAT2s, while similar formation only occurred at the highest cell density in the bio-printed cells. However, the printed spheroids maintained the alveolar marker CPM and tdTomato expression of 98.7% and 97% respectively, levels similar to those seen in the Matrigel.

We anticipate that further experiments optimising the seeding conditions and adjustable ECM properties could produce iAT2 spheroids comparable to those grown in Matrigel with the added benefits of consistency and scalability.