Latent Nature of Collagen in Promoting Three-Dimensional Adherent Spheroid Formation of Fibroblasts

Abstract

Fibroblast migration in connective tissues is important for remodeling and renewal. Fibroblast spheroids are useful for understanding biological activity in an environment similar to in vivo conditions. Recently, we developed low-adhesive scaffold collagen (LASCol) from type I collagen by actinidain hydrolysis and found that fibroblasts cultured on the LASCol matrix exhibited spontaneous, rapid spheroid formation. In this study, the formation and properties of fibroblast spheroids were characterized in detail. The surfaces of fibroblast spheroids were clearly distinct from those of monolayer fibroblasts, including differences in the number and shape of membrane protrusions. Interestingly, the speed of spheroid formation was maintained at about 0.9 µm/min, even after 24 h of incubation. Our results also indicated that cell proliferation in spheroids stopped and that the relative expression levels of the genes encoding fibronectin, integrin s3, bFGF, PDGF-A, and TGF-s1 increased. LASCol is useful for obtaining adherent spheroids for tissue engineering and drug screening. We demonstrated that collagen has a latent nature in forming three-dimensional adherent spheroids of fibroblasts and in promoting the essential functions of fibroblasts.