PhD student in biology · Seifert Lab · University of Kentucky ORCID PubMed

Why can some mammals rebuild complex tissue while close relatives form scars?

I study why some mammals rebuild complex tissues while closely related species heal with scars. My work compares wound healing, tissue repair, and cellular features across rodent species. I integrate field sampling with our animal colony to perform histology, molecular biology, cell culture, and computational analysis in a comparative multi-species framework.

Understand how complex tissue regeneration evolved in mammals.

Rodents are the most speciose and ecologically diverse group of mammals, but most of what we know about mammalian biology comes from a few laboratory species. Notably, the molecular model species employed today (Mus, Rattus) exhibit poor or no regenerative ability. Comparing close relatives that heal differently lets us ask when regeneration arose and which underlying features distinguish it from scar formation.

Current focus

Following regeneration from species to tissue to mechanism.

01Find the Trait

Compare related rodent species and test whether the same injury regenerates or heals with scar tissue.

02Describe the Outcome

Measure wound closure and examine whether cartilage, skin, hair follicles, muscle, and other structures are rebuilt.

03Compare What Differs

Use regenerating and scar-forming species to identify candidate cells and molecular pathways for deeper study.

Publications

2025

Complex tissue regeneration in Lophuromys reveals a phylogenetic signal for enhanced regenerative ability in deomyine rodents

Brennan Riddell, Molly McDonough, Adam Ferguson, John M. Kimani, Thomas R. Gawriluk, Chi Peng, Stephen G. Kiama, Vanessa O. Ezenwa, and Ashley W. Seifert

Proceedings of the National Academy of Sciences · 122(1): e2420726122 · DOI 10.1073/pnas.2420726122

PubMed PMC full text Download PDF DOI

Comparative model system

Why compare related species?

Comparative regeneration phylogeny Eleven sampled rodents with four contextual taxa

Select a species or branching point to inspect the estimate.

Regeneration competent Scar-forming repair Unknown / untested 95% HPD Terminal date unresolved

Hominidae Leporidae Gliridae Nesomyidae Muridae: Gerbillinae Muridae: Murinae Muridae: Deomyinae

Calibration, evidence, and taxonomic notes

Node ages are posterior means from the completed node-dated maximum-clade-credibility mammal tree of Upham, Esselstyn, and Jetz (2019); the source data are archived in Dryad. Branch colors show family or subfamily membership, while tip symbols show healing outcome.

Rabbit and human provide broad mammalian context and were not part of the Riddell et al. experiment. Uranomys and Deomys are marked unknown because they were not tested there. G. vicinus uses the source G. robustus branch, and L. zena uses the L. flavopunctatus source lineage with no invented terminal date.

Comparative regeneration builds on a long history.

Regeneration was an experimental subject long before modern mammalian models. Eighteenth-century studies of hydra, salamanders, and other regenerating animals helped establish the field; rabbit ear-hole regeneration was reported in the 1950s and investigated over the following decades. In 2012, Ashley Seifert and colleagues showed that African spiny mice could regenerate skin, hair follicles, and ear tissues after injury, establishing a modern mammalian system for asking how this capacity works.

Our 2025 study extends that line of work by applying the same ear-punch assay across eleven rodent species. The sampled Acomys and Lophuromys rebuilt patterned tissue; the other sampled rodents formed scar tissue. Uranomys and Deomys remain untested, making them informative open branches within Deomyinae.

Rabbit and adult human skin appear on the tree as broader mammalian context, not as taxa from our experiment. The comparison uses shared ancestry to frame the next questions without treating phylogenetic position as the answer.

Read the paper

Field research

Kenya field sites, routes, and observations

Rodents are the most diverse group of mammals, yet most species remain far less studied than laboratory mice and rats. Fieldwork lets us compare natural variation where it evolved and document it while many habitats are changing faster than their biodiversity can be studied.

Scope and specimens. This is basic comparative biology rather than a conservation intervention. Field biology is not impact-free: animals collected for this work may be euthanized for tissue sampling and museum vouchers, or brought into research colonies and later sampled under approved protocols. Voucher specimens prepared for the National Museums of Kenya and the Field Museum preserve a permanent, verifiable record of the animals and places behind the research.

Field notebook

Animal sightings

A running checklist from a recent Kenya field trip. Provisional and unresolved identifications remain visible.

Explore the phylogeny and checklist Loading sightings…

Trip-wide phylogeny

This topology places the identified animals from the full checklist in their evolutionary context. Branch lengths do not represent time; branch colors identify families. Use the controls to narrow the tree, or switch to the checklist for observation details and identification notes.