Abstract
In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized drugs or understand the tissue development process. Several studies have attempted to fabricate biological tissue in vitro. However, controlling the growth and morphology of the fabricated tissue remains a challenge. Therefore, new techniques are required to modulate tissue growth. RGD (arginine-glycine-aspartic acid), which is an integrin-binding domain of fibronectin, has been found to enhance cell adhesion and survival; it has been used to modify substrates for in vitro cell culture studies or used as tissue engineering scaffolds. In addition, this study shows novel functions of the RGD peptide, which enhances tissue growth and modulates tissue morphology in vitro. When an isolated submandibular gland (SMG) was cultured on an RGD-modified alginate hydrogel sheet, SMG growth including bud expansion and cleft formation was dramatically enhanced. Furthermore, we prepared small RGD-modified alginate beads and placed them on the growing SMG tissue. These RGD-modified beads successfully induced cleft formation at the bead position, guiding the desired SMG morphology. Thus, this RGD-modified material might be a promising tool to modulate tissue growth and morphology in vitro for biological tissue fabrication.
Highlights
Recent advancement of material sciences in combination with cell and molecular biology has increased the possibilities for in vitro biological tissue fabrication
We carried out an submandibular gland (SMG) organotypic culture on alginate hydrogel sheets with varying mechanical stiffness and obtained results indicating that bud expansion and cleft formation in the SMG were enhanced on the softer gel (4 kPa), but was attenuated on the stiffer gel (184 kPa)[16]
The stiffer gel was used as a negative control for this study to evaluate the effect of RGD on the growth and morphogenesis of SMG tissue
Summary
Recent advancement of material sciences in combination with cell and molecular biology has increased the possibilities for in vitro biological tissue fabrication. The SMG morphological change including the formation of a number of buds and ductal elongation is called branching morphogenesis[7]. A peptide-immobilized alginate scaffold with osteoblast and chondrocyte composites was transplanted onto the back of a mouse, resulting in ectopic formation of the growth plate[14] In this context, RGD-modified materials acted as a substrate that supported cell adhesion and survival under in vivo conditions[15]. We hypothesized here that an RGD-modified material would be effective for artificial modulation of SMG growth and morphogenesis To test this hypothesis, in this study, in vitro SMG explant culture was carried out by using RGD-modified alginate hydrogels with two different shapes, sheets and beads
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