Cell-derived Extracellular Matrix Proteins in Colloidal Microgel as a Self-Assembly Hydrogel for Regenerative Endodontics

Introduction: This study investigated a colloidal microgel for angiogenic and odontogenic differentiation of cells in the presence of cell-derived extracellular matrix (ECM) proteins using a 3-dimensional culture model. Methods: Viscoelastic properties of human dental pulp were determined to understand the native ECM environment. ECM proteins were extracted from dental pulp stem cell (DPSC) cultures, and MaxGel (Millipore Sigma, Burlington, MA) was used as a commercially available ECM protein. DPSCs were incubated in colloidal microgels in the presence of ECM proteins or gelatin methacryloyl (GelMA) as a bulk hydrogel (n = 9/group). The viability and odontogenic differentiation of DPSCs within hydrogels was determined using viability assays, mineralization staining, calcium and alkaline phosphatase assays, and quantitative polymerase chain reaction for odontogenic gene expression. Angiogenic properties of endothelial cells were determined using tubule formation assays and quantitative polymerase chain reaction to detect angiogenic gene expression. Results: Dental pulp had a higher elastic modulus than the viscous modulus, showing a solidlike response similar to hydrogels. DPSC-derived ECM showed higher collagen and GAG than MaxGel (P < .05). The viability of DPSCs was similar in colloidal microgels, whereas higher cell viability, calcium deposition, and alkaline phosphatase activity were observed in GelMA (P < .05). Colloidal microgels allowed tubule-like structures by endothelial cells, whereas no tubular formation was observed in GelMA. DPSC-derived ECM in colloidal microgel up-regulated odontogenic gene expression, whereas MaxGel up-regulated angiogenic gene expression (P < .05). Conclusions: Colloidal microgels allowed cellular organization that can improve penetration and nutritional supply in a full-length root canal system. The bioactivity of cell-derived ECM proteins can be modified depending on the external stimulus.