Abstract While antifibrotic therapies continue to advance, they fall short when treating large or chronic wounds. Essential to developing new regenerative strategies is a comprehensive understanding of how cell proliferation is activated, maintained, and eventually terminated to accurately restore missing tissue. The objective of this proposal is to determine the cell autonomous mechanisms that permit and control proliferation during complex tissue regeneration in highly regenerative mammals (spiny mice and rabbits). Spiny mice are unique among rodents in their ability to regenerate complex skin and musculoskeletal tissues and as such, they represent a promising model for pinpointing molecular and cellular mechanisms that prevent regeneration in humans. Fascinatingly, primary dermal fibroblasts from spiny mice and rabbits maintain proliferation in the face of reactive oxygen species, gamma irradiation, and contact inhibition. These same conditions induce senescence or quiescence in primary dermal fibroblasts from poorly regenerative mammals (lab mice and rats). This proposal uses cells from these species to identify how identical signals trigger regeneration in some species and scarring in others. Further, this proposal utilizes spiny mouse ear pinna regeneration, a highly reproducible and tractable model of mammalian skin and musculoskeletal regeneration, to further explore pro-regenerative signals in vivo. In Aim 1, I will examine how stress signals are differentially transduced by cells to determine how fibroblasts from highly regenerative mammals maintain proliferation in senescence inducing conditions in vitro. I will then use spiny mouse ear pinna regeneration to determine how this differential stress transduction leads to activation and maintenance of regenerative response following injury in vivo. In Aim 2, I will identify the mechanisms that permit primary fibroblasts from spiny mice and rabbits to proliferate at very high cell densities in vitro. I will then use spiny mouse ear pinna regeneration to determine how these mechanisms regulate proliferation and tissue size in vivo. I hypothesize that cells from highly regenerative mammals differentially activate signaling pathways that facilitate cell cycle progression in response to stress and maintain this activity in excess of inhibitory signals that terminate proliferation in non-regenerative mammals. These studies will generate RNA-seq datasets and identify candidate genes that will drive discovery in the field and form a basis for my own independent research. By studying proliferative control during regeneration, we can build a blueprint for the recapitulation of regeneration in human medicine.

Project Narrative Skin and musculoskeletal regenerative therapies for large and chronic wounds are limited by an incomplete understanding of proliferative regulation. This proposal investigates how highly regenerative mammals activate and maintain cell proliferation in the face of inhibitory conditions to drive regeneration. This work will generate novel targets for regenerative therapies and high throughput screening tools for evaluating phenotypes associated with regenerative ability.