Tiny bricks for oral bioprinting: Exploring gingiva and dental pulp-derived organ building blocks

This study developed and compared organ building blocks derived from human gingiva- and dental pulp-derived stromal cells as potential cellular components for periodontal tissue engineering and 3D bioprinting. Five OBB designs were evaluated: gingiva-only, pulp-only, a 1:1 mixture of gingiva and pulp cells, pulp-core OBBs surrounded by gingival cells, and gingiva-core OBBs surrounded by pulp cells. All OBBs compacted substantially during culture, although their morphology, cell packing, spreading behavior, stiffness, extracellular matrix organization, sprouting, and metabolic characteristics depended on cell composition and spatial arrangement. Pulp-derived OBBs formed the densest structures and were mechanically stiffest, whereas gingiva-derived OBBs were softer and exhibited stronger spreading behavior. At day 3, pulp-derived OBBs had an average Young’s modulus of 1.6 ± 0.6 kPa compared with 0.8 ± 0.5 kPa for gingiva-derived OBBs; by day 7, pulp-derived OBB stiffness increased to 3.7 ± 1.7 kPa while gingiva-derived OBBs remained approximately 0.8 ± 0.4 kPa. Mixed and layered two-cell OBBs exhibited intermediate mechanical properties near 1 kPa at day 3, with some groups stiffening during further culture. Collagen I accumulated centrally within all OBB types, while fibronectin formed distributed extracellular networks. Two-cell OBBs generally spread and sprouted more effectively than monoculture OBBs when transferred to adhesive surfaces or embedded in PEG-modified fibrin hydrogel. Fluorescence lifetime imaging also revealed distinct metabolic profiles between pulp- and gingiva-derived cells. The authors concluded that combining the two oral stromal cell types improved the structural, mechanical, and functional characteristics of OBBs and that mixed or layered OBB designs could provide customizable cellular building blocks for future periodontal bioprinting applications.