Covalent Cell‐Loading Injectable Hydrogel Scaffold Significantly Promotes Tissue Regeneration In Vivo Compared with a Conventional Physical Cell‐Loading Hydrogel Scaffold

Abstract

Currently, one of the major tendencies to be adopted for the design of hydrogel scaffolds in tissue engineering include that cells are loaded physically into the pores of 3D hydrogel networks. In this study, a drastic deviation from this tendency is proposed and developed a new type of hydrogel scaffold in which cells are covalently connected to 3D hydrogel networks via bioorthogonal click cross‐linking reactions of azide‐modified cells with alkyne‐modified polymers. The purpose of this study is to directly compare the utility of the covalent cell‐loading approach and the conventional physical cell‐loading approach as hydrogel scaffolds for in vivo tissue engineering. It is found that the proposed covalent cell‐loading approach significantly promotes tissue regeneration and functional recovery in vivo in comparison with the conventional physical cell‐loading approach. This is the first report demonstrating the importance of the covalent cell‐loading approach in tissue engineering. This covalent cell‐loading approach is applicable to a broad spectrum of mammalian cells, including stem cells. The present findings provide a promising new route to generate innovative hydrogel scaffolds for in vivo tissue engineering.

Biological Tissue-Inspired Living Self-Healing Hydrogels Based on Cadherin-Mediated Specific Cell–Cell Adhesion

“…Based on this concept, we recently developed a new type of biohybrid hydrogel in which individual living cells are covalently connected through a three-dimensional polymeric gel network (Figure 1). 38,39 In the present study, as a proof-of-concept, we demonstrate the unique self-healing capability of CxGel, which originates from cadherin-mediated intercellular adhesion between cells incorporated into the CxGel. This study is the first example of a self-healing material in which biologically derived living cells are incorporated into a synthetic material as a focus to promote self-healing.…”

“…Based on this concept, we recently developed a new type of biohybrid hydrogel in which individual living cells are covalently connected through a three-dimensional polymeric gel network (Figure ). , This cell cross-linked hydrogel was designated CxGel. Because individual cells are covalently connected through the gel network in CxGel, we expect that the mechanically conductive gel network would permit the transmission of individual cell–cell adhesion force generated at the interface of CxGels to the whole CxGel via an extendable cascade, resulting in a macroscopic adhesion of the whole CxGel.…”

“…Mouse myoblast C2C12 cell-based CxGels were constructed via two-step reactions (Figure a). , First, reactive azide groups were incorporated into sialic acid residues on cell surface glycans via metabolic glycoengineering by providing cells with tetraacetylated monosaccharide N -azidoacetylmannosamine. − Azide-modification was identified by covalent labeling using the clickable fluorescent dye dibenzocyclooctyne (DBCO)-modified carboxyrhodamine (Figure a). Biocompatible alginate was reacted with amine-terminated 4-arm polyethylene glycol to synthesize branched alginate (bAlg; Scheme S1 and Figure S1).…”

Covalent Stem Cell-Combining Injectable Materials with Enhanced Stemness and Controlled Differentiation In Vivo

“…We previously proposed a universal technique to construct human cell-based biohybrid hydrogel materials in which azide-modified living cells are chemically (covalently) cross-linked with alkyne-modified polymers via the bio-orthogonal click reaction. − Currently, many researchers have reported various cell-surface modification methods, including chemical conjugation, lipid insertion, and metabolic glycoengineering. , The chemicals can be stably introduced to the cell membrane by chemical conjugation, though it is concerned that this method could affect cell viability by interfering with the function of membrane proteins. In the case of lipid insertion, the chemicals can be inserted physically within cell membranes via hydrophobic interactions without interference with membrane protein’s function.…”

“…Considering these advantages, we utilized metabolic glycoengineering to form cell cross-linked hydrogels in this study. Since we have demonstrated that this covalent cellcombining approach results in enhanced retention of the material's "livingness" in the body in comparison with the conventional physical cell-combining approach, 18 we hypothesized that the cell cross-linked hydrogel system can be adapted for constructing stem cell-combining biohybrid materials suitable for in vivo tissue engineering applications. In this study, we developed a novel ADSC-based cross-linked hydrogels (ADSCxGels) (Figure 1) and showed its utility as a living stem material for in vivo tissue engineering.…”