Activating an adaptive immune response from a hydrogel scaffold imparts regenerative wound healing.

Biomaterial scaffolds represent a promising approach for material-based tissue regeneration. We previously developed microporous annealed particle (MAP) hydrogels - a flowable, microparticle-based hydrogel in which neighboring hydrogel particles are linked in situ to form a porous scaffold that accelerates wound healing. To promote more extensive tissue ingrowth before scaffold degradation, we aimed to slow scaffold degradation by switching the chirality of the crosslinking peptides from L-peptides to D-peptides. Unexpectedly, despite showing the predicted slower enzymatic degradation in vitro, D-peptide crosslinked MAP hydrogel (D-MAP) hastened material degradation in vivo and imparted significant tissue regeneration to healed cutaneous wounds, including increased tensile strength and hair neogenesis. By themselves, D-chiral peptides were poor activators of macrophage innate immune signaling in vivo, but MAP particles elicit IL-33 type 2 myeloid cell recruitment which is amplified in vivo in the presence of D-peptides. Remarkably, D-MAP elicited significant antigen-specific immunity against the D-chiral peptides, and an intact adaptive immune system was required for the hydrogel-induced skin regeneration. These findings demonstrate that the generation of an adaptive immune response from a biomaterial is sufficient to induce cutaneous regenerative healing despite faster scaffold degradation.