A multispecies system for elucidating proliferative control mechanisms during mammalian skin and musculoskeletal regeneration

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.

Grant Number: 5F32AR083259-02
NIH Institute/Center: NIH
Principal Investigator: Robyn Allen