During combat, burn injuries to our military personnel often leave our Veterans with severely scarred skin, painful contractures, with impaired barrier or temperature function. Novel therapies that can prevent or reverse fibrosis are desperately needed. Outside of fetal wounds, regeneration of native hair follicles, sweat glands, and adipose tissue, was previously thought impossible. Recent work has shown that, in principle, very large skin wounds in adult mice can spontaneously regenerate new hair follicles and adipose tissue, while small wounds or large burn wounds in mice end with the same fate as clinical wounds in humans: fibrotic scarring. We recently discovered that when our innovative biomaterial, Microporous Annealed Particle (MAP) hydrogel, activates an immune response, it can induce hair follicle regeneration in small murine wounds that would otherwise heal by scarring. This proposal combines state-of-the-art molecular, bioinformatic, and bioengineering techniques to: 1) improve our understanding of why burn wounds in mice result in fibrosis while large excisional wounds result in regeneration; and 2) use immunomodulatory MAP hydrogel formulations to transform the fibrotic burn wound microenvironment into one conducive of skin regeneration. This application will test our hypothesis that by engineering immunomodulatory MAP hydrogel to specifically target pro-regenerative immune responses and limit pathways contributing to burn wound fibrosis, we can induce a highly desirable regenerative response in burn wounds. The first aim will leverage single cell transcriptomics, a novel bioinformatics methodology to assess cell to cell communication, and loss of function mutants to define molecular programs responsible for fibrotic wound healing in burn wounds versus regenerative healing in large excisional wounds at single cell resolution. The second aim will test whether two immunomodulatory MAP formulations that regenerate hair follicles in small excisional wounds can reprogram immune cell to fibroblast communication networks in the burn wound microenvironment to activate regeneration. In the third aim, we will confirm that immune and fibroblast signaling networks in murine fibrosis are active in human burn wounds to identify novel anti-fibrotic strategies activated in regenerating wounds. The proposed studies are significant because they will establish new immune cell-driven mechanism for diminishing fibrosis and provide opportunities to develop anti-fibrotic and/or proregenerative targets for therapies for reducing scarring in burn wounds. The proposed studies are innovative because they will establish new types of immune-modulating biomaterials, and enable a new paradigm of biomaterial-triggered regenerative response for burn wounds tissues. In the future, the results of this study will drive the development of next- generation immune-modulating wound biomaterials for potential clinical use.