Enhancing the Three-Dimensional Structure of Adherent Gingival Fibroblasts and Spheroids via a Fibrous Protein-Based Hydrogel Cover

Abstract

Tissue engineering-based therapies rely on the delivery of monolayered fibroblasts on two-dimensional polystyrene-coated and extracellular matrix (ECM) surfaces to regenerate connective tissues. However, this approach may fail to mimic their three-dimensional (3D) native architecture and function. We hypothesize that ECM fibrous proteins, which direct the migration of cells in vivo, may attach and guide polystyrene- and Matrigel™-ECM (M-ECM)-adherent fibroblasts to rearrangement into large multicellular macrostructures with the ability to proliferate. Gingival monolayered fibroblasts and their derived spheroids were added and adhered to tissue culture polystyrene and M-ECM surfaces. The cells were covered with a layer of collagen1 hydrogel combined with vitronectin, fibronectin or fibrin, or 10% M-ECM. The development of 3D cell constructs was characterized by epifluorescence and confocal scanning microscope image analysis. The ECM turnover and the proliferative capabilities of the fibroblasts were determined via gene expression profiling of collagen1, fibronectin, matrix metalloproteinase/metallopeptidase 2, Nanog, and SRY (sex-determining region Y)-box2 (Sox2). Expression of the Sox2 protein was followed by immunostaining. The collagen1 protein had the strongest effect on monolayered and spheroid cell rearrangements, forming large spherical shapes and fused 3D macroconstructs. The addition of fibrin protein was typically required to achieve a similar effect on M-ECM-adherent monolayered fibroblasts. The spheroid fusion process was followed by an increase in cell density and the formation of tight clusters. The fused spheroids continued to maintain their intracellular ECM turnover and proliferation capacities. Collagen1 is a valuable component in the rearrangement of adherent fibroblast monolayers and spheroids. Fibroblast spheroids should preferably be used as basic building blocks to assemble multicellular connective tissue-like macrostructures.