Evaluation of different methodologies for primary human dermal fibroblast spheroid formation: automation through 3D bioprinting technology

Cell spheroids have recently emerged as an effective tool to recapitulate native microenvironments of living organisms in an in vitro scenario, increasing the reliability of the results obtained and broadening their applications in regenerative medicine, cancer research, disease modeling and drug screening. In this study the generation of spheroids containing primary human dermal fibroblasts was approached using the two-widely employed methods: hanging-drop and U-shape low adhesion plate (LA-plate). Moreover, extrusion-based three-dimensional (3D) bioprinting was introduced to achieve a standardized and scalable production of cell spheroids, decreasing considerably the possibilities of human error. This was ensured when U-shape LA-plates were used, showing an 85% formation efficiency, increasing up to a 98% when it was automatized using the 3D bioprinting technologies. However, sedimentation effect within the cartridge led to a reduction of 20% in size of the spheroid during the printing process. Hyaluronic acid (HA) was chosen as viscosity enhancer to supplement the bioink and overcome cell sedimentation within the cartridge due to the high viability values exhibited by the cells-around 80%-at the used conditions. Finally, (ANCOVA) of spheroid size over time for different printing conditions stand out HA 0.4% (w/v) 60 kDa as the viscosity-improved bioink that exhibit the highest cell viability and spheroid formation percentages. Besides, not only did it ensure cell spheroid homogeneity over time, reducing cell sedimentation effects, but also wider spheroid diameters over time with less variability, outperforming significantly manual loading.

Automated summary

Cell spheroids are an effective tool for recapitulating native microenvironments in vitro, and have broad applications in regenerative medicine, cancer research, disease modeling, and drug screening. This study compares different methods for generating spheroids and introduces 3D bioprinting for standardized and scalable production. The use of U-shape LA-plates combined with 3D bioprinting technology significantly increased formation efficiency. However, sedimentation effects and reduced spheroid size were observed during the printing process. The addition of hyaluronic acid as a viscosity enhancer improved cell viability and spheroid formation, with HA 0.4% (w/v) 60 kDa showing the best results.