2025 Theses Doctoral

Transcriptional Regulation of Progenitor Cell Fate in Craniofacial Ligament Regeneration

Anderson, Troy

Mammalian healing is commonly limited by the formation of a fibrotic scar rather than regeneration via differentiation of native tissue. This is especially true for traumatic ligament injuries, which have lifelong clinical consequences even after surgical reconstruction. Here, we establish the adult zebrafish interopercular-mandibular (IOM) ligament as a novel model capable of scar-free regeneration within a month following transection injury.

Lineage tracing shows that ligament regeneration occurs through de-differentiation and cell cycle re-entry of the ligamentocyte lineage to a regenerative mesenchyme progenitor state. Single-cell RNA sequencing highlights that these cells undergo dynamic transcriptional changes in both fibroblast and immune populations within the first 3 days following injury, and that the regenerative mesenchyme is transcriptionally distinct from the developing ligament.

These transcriptional changes are accompanied by dynamic shifts in chromatin accessibility in regenerating fibroblasts, which show a global increase in AP-1 motif accessibility. Finally, comparison of these sequencing data to other regenerating fibroblasts in tail fin, heart, spinal cord, and whole joint identifies a shared injury-activated fibroblast state. Together, these findings establish the adult zebrafish as a model for scar-free ligament regeneration and suggest that the regenerative capacity of zebrafish relies on fibroblast de-differentiation using a regeneration-specific program.