Biology subjects

Seifert, A. W.

Publications and source records attributed to Seifert, A. W..

17 recordsLinked to original sources

bioRxiv2026

Actively cycling cells in uninjured connective tissue are not a prerequisite for appendage regeneration

Multiple hypotheses have been formulated to explain differences in tissue repair ability across vertebrates. One hypothesis posits that the accessibility of actively cycling stromal cells within uninjured tissue confers access to a proliferative population in response to tissue damage. This hypothesis further suggests that animals with an indeterminate growth mode possess an actively cycling cell population necessary for growth that can be readily accessed for tissue regeneration. Moreover, the absence of an actively cycling population in connective tissue provides a mechanism that restricts regeneration in animals with determinate growth whose cells are refractory to cell cycle progression and proliferation to produce new tissue for morphogenesis. Here, we explore this paradigm using an EdU-BrdU pulse chase strategy in four different vertebrate species: two with determinate (Acomys dimidiatus and Mus musculus) and two with indeterminate modes of growth (Danio rerio and Ambystoma mexicanum). We find that although indeterminate growers do possess a small population of actively cycling cells, this population does not contribute to regeneration. Moreover, we found that while Acomys does not possess a population of actively cycling stromal cells, cells re-enter the cell cycle de novo in these animals to contribute to regeneration. Furthermore, testing this hypothesis allowed us to ask whether tissue injury could stimulate cell cycle re-entry - a so-called primed state - in cells at distance from the injury site in these four species and we did not find evidence of such priming in stromal or epidermal tissue. HighlightsO_LICell cycle re-entry is a common response to injury in regenerative and non-regenerative vertebrates that is independent of actively cycling stromal cells in uninjured connective tissue C_LIO_LIActively cycling cells do not contribute to regenerative healing in spiny mice, axolotls or zebrafish. C_LIO_LIOur data do not support systemic cell cycle activation in response to injury. C_LI

developmental biology↗

bioRxiv2026

Deep tissue removal in wounds facilitates algal colonization and inhibits healing and regeneration in tropical corals

Although corals are highly regenerative, some colonies in reef ecosystems completely recover from sublethal damage while other colonies exhibit partial mortality to similar injuries. To understand factors that might naturally curtail regenerative ability, we experimentally wounded small colonies in three coral genera (Acropora, Pocillopora, Porites) by mimicking natural corallivory using scraping (tissue and skeletal damage) or airbrushing (deep tissue removal with no skeletal injury). We found all scraped wounds regenerated rapidly in Acropora and Porites, while Pocillopora fragments frequently retained open lesions. In stark contrast, airbrushing resulted in algal colonization and delayed tissue healing and regeneration across all corals. Detailed cellular analysis of Porites wounds revealed two general phases comprising tissue regeneration: a healing phase defined by rapid coverage of bare skeleton with coenosarc, pigment cells and gastrodermal reformation, and then a second phase lasting one week ending in polyp regeneration. Red fluorescence appeared transiently in scrape wounds but persisted in tissue at the wound margin surrounding algae in airbrush wounds, suggesting that algal occupation of the wound bed inhibits coenosarc healing. Lastly, histological cross-sections of healing airbrush wounds in Porites revealed progressive loss of deep tissue leading to skeletal breakdown beneath the wound. Together, our results demonstrate the biphasic nature of tissue regeneration in colonial corals and provide a framework for understanding how biotic factors impact tissue repair and regeneration in nature.

zoology↗

bioRxiv2026

AAV tools enable functional modulation and readout of central and peripheral nervous systems in spiny mice

Among mammals, spiny mice (Acomys spp.) exhibit the unique capacity to regenerate parts of their nervous system. Studying this phenomenon has the potential to reveal new targets that can slow or halt human neurodegenerative disorders. Unfortunately, research tools (e.g., transgenic lines, gene delivery vehicles) are lacking compared to those available for other rodent models. Here, we tested systemic adeno-associated viral vectors (AAVs) in Acomys dimidiatus and identified three promising candidates: X1.1, CAP-Mac, and MaCPNS1. Characterizing their tropism following intravenous delivery, we found that in the brain, MaCPNS1 and X1.1 primarily transduced astrocytes. In the peripheral nervous system, MaCPNS1 efficiently transduced dorsal root ganglia, axon bundles of the ear pinnae, and enteric neurons throughout the gastrointestinal tract. As a proof-of-concept, we used MaCPNS1 to chemogenetically modulate the activity of enteric neurons, successfully decreasing gastric motility in vivo and increasing colonic motility ex vivo. We expect these findings to enable functional studies of the uniquely regenerative nervous system of Acomys, which may in turn help advance neuroregenerative therapeutics for humans. Summary StatementIdentification of an AAV tool to efficiently deliver transgenes to the central and peripheral nervous systems of spiny mice enables functional studies of the nervous system in a mammalian model of regeneration.

neuroscience↗

bioRxiv2026

A novel fracture lattice in spiny mouse skin facilitates tissue autotomy and regeneration

Autotomy is a unique phenotype whereby an animal sheds a body part to escape predation1-3. The timing and location of autotomy are tightly regulated by preformed planes of weakness (aka fracture planes) which facilitate tissue loss. While autotomy is often followed by regeneration, these phenotypes are rarely reported in mammals4-9. A notable exception are spiny mice (Acomys) which exhibit skin autotomy and more remarkably, complete tissue regeneration10-14. Presently, mechanisms underlying autotomy and complete regeneration in Acomys skin remain elusive. Here, we report the discovery of a honeycomb-like fracture lattice in Acomys skin whose design directs tissue destruction but also facilitates regenerative healing. Unlike the single continuous surface of a fracture plane, this fracture lattice consists of a three-dimensional array of hexagonal units whose boundaries guide tissue breakage. Moreover, we identify collagen VI as the main constituent of the fracture lattice and find that it is distinctly arranged to initiate fracturing and propagation of skin tearing. By preconditioning the tissue for autotomy, the fracture lattice dampens the damage-induced inflammatory response but also upregulates a pro-regenerative gene signature, accelerating skin appendage regeneration. Lastly, we discovered the key role of spiny hairs in fracture lattice formation, as inhibiting their development leads to abnormal pattern formation and changes in skin fracture mechanics. Our results present a novel example of a uniquely evolved structural adaptation in mammalian skin that links tissue patterning, autotomy and regeneration. We expect that the application of a modular compartment structure to artificial skin and other organ engineering may enhance resilience to injury and facilitate efficient regeneration.

developmental biology↗

bioRxiv2025

Parkinsons disease modeling in regenerative spiny mice (Acomys dimidiatus) captures key disease-relevant behavioral, histological, and molecular signatures

Parkinsons disease (PD) is a multifactorial neurodegenerative disorder that has been modeled extensively in animals, primarily rodents, but also in non-human primates and non-mammalian organisms. However, no single animal model fully recapitulates the hallmarks of PD pathology. Here, we extend this work by modeling PD for the first time in the spiny mouse (Acomys dimidiatus), a mammal notable for its robust regeneration of multiple tissues. We show that the nigrostriatal pathway of A. dimidiatus is vulnerable to both acute 6-hydroxydopamine (6-OHDA) toxicity and chronic -synuclein (Syn) preformed fibril-induced aggregation. Mouse Syn PFFs produced widespread pS129-positive Syn inclusions across multiple brain regions, mirroring a key pathological hallmark of PD. Compared to C57BL/6J mice, A. dimidiatus exhibited more pronounced behavioral impairments, greater nigrostriatal degeneration, and higher pS129-Syn inclusion burden within substantia nigra pars compacta (SNpc) neurons. To probe the molecular underpinnings behind the vulnerability, we performed single-cell spatial proteomics, which revealed extensive proteomic alterations in dopaminergic neurons associated with Syn aggregation. Multiple proteins were dysregulated in A. dimidiatus, including those involved in proteasomal function, mitochondrial pathways, and oxidative stress regulation, which are processes commonly implicated in PD. Notably, proteomic analysis identified heightened astrocytic activation in the SNpc, which we validated histologically, suggesting a distinct glial response compared to mice. Together, these findings expand our understanding of PD-relevant pathophysiology across species and establish A. dimidiatus as a model for studying mechanisms of neurodegeneration.

neuroscience↗

bioRxiv2025

Active mitochondria in healthy spiny mouse fibroblasts resemble megamitochondria and remain resilient across lifespan

Although they exhibit limited regenerative ability of some tissues and organs shortly after birth or towards the end of fetal development, humans and laboratory mammals quickly transition to producing scar tissue for tissue repair. In contrast, spiny mice exhibit complex tissue regeneration as adults and provide a blueprint for how regeneration can occur throughout adulthood in mammals. Fibroblasts are key mediators of wound healing outcomes and prior work uncovered that cells from highly regenerative mammals (spiny mice and rabbits) exhibit extreme resistance to oxidative stress compared to those from non-regenerating laboratory mice and rats. Using a battery of cellular tests in primary ear pinna fibroblasts from highly regenerative and non-regenerative mammals, we find that cells from spiny mice and rabbits exhibit a baseline preference for glycolysis supporting a lower ROS-producing basal state. Uniquely, spiny mouse fibroblasts exhibit large, spherical, depolarized mitochondria similar to megamitochondria identified in pathological tissues. The megamitochondria phenotype was present across lifespan in ear pinna fibroblasts from fetal, young and old spiny mice. While rabbit, mouse and rat fibroblasts had polarized tubular mitochondrial networks typical of adult mammalian fibroblasts, isolated rabbit and spiny mice fibroblasts shared lower oxygen consumption efficiency even in the absence of a potential gradient. Taken together, our results support that a shared metabolic signature exists in stromal cells from highly regenerative mammals, although possibly driven by different mechanisms, to converge on a ROS-resistant phenotype which ultimately helps supports tissue regeneration.

cell biology↗

bioRxiv2025

Specific cell states underlie complex tissue regeneration in spiny mice

SUMMARY STATEMENTComparing regenerative vs. fibrotic healing, we identify injury-induced cell states associated with persistent cell cycle progression and complex tissue regeneration in mammals. Cell proliferation is an elemental feature of epimorphic regeneration in vertebrate taxa. We previously reported that in contrast to fibrotic repair observed in laboratory mouse (Mus) strains, highly regenerative spiny mice (Acomys spp.) exhibit cell cycle progression and cell proliferation to faithfully replace missing tissue. However, little is known about proliferation dynamics, and specific cell types and states that may contribute to complex tissue regeneration in mammals. Using temporal pulse-chase experiments, we show that stromal cells in Acomys dimidiatus rapidly re-enter the cell cycle in response to injury and maintain tight spatiotemporal control of cell cycle progression to restrict the proliferative population to a distal area relative to the injury. Conversely, Mus stromal cells incorporate thymidine analogs without cell division supporting an S-phase arrest after D10. Deploying immunostaining and scRNA-seq, we identify several key cell types (CRABP1+, SMA+) differentially associated with regenerating versus scar tissue. Importantly, our single cell data revealed distinct gene expression profiles for cross-species stromal cell types, identifying cell states specific for regenerative or fibrotic healing. While CRABP1+ fibroblasts are enriched in Acomys ears before and after injury, similar fibroblasts enriched in young, postnatal Mus ears remain unable to promote regeneration. Our data underscore the finely regulated dynamics of proliferating cells during regeneration and emphasize that regeneration depends on multiple factors including the presence of specific cell types and the ability of cells to acquire specific states. Key Conclusions-Differentiated cells in Acomys, Mus and Danio re-enter the cell cycle in response to injury, while homeostatic cycling cells contribute to blastema formation in Ambystoma -Pulse-chase thymidine analog labeling shows tight spatiotemporal control of proliferating stromal cells during regeneration in Acomys. -Following injury, CRABP1 and SMA are expressed in distinct stromal cell populations in Acomys but are co-expressed in Mus stromal cell populations. -Species-specific cell states underlie regenerative and fibrotic repair -CRABP1+ cells are lost during embryonic development in Mus ear pinna but are retained in Acomys to adulthood. -Young neonatal Mus with abundant CRABP1+ cells still fail to execute regenerative healing

developmental biology↗

bioRxiv2024

Metabolic Adaptations in Adult Spiny Mouse (Acomys) Cardiomyocytes Facilitate Enhanced Cardiac Recovery Following Myocardial Infarction

The adult mammalian heart has limited regenerative capacity following injury, leading to progressive heart failure and mortality. Recent studies have identified the spiny mouse (Acomys) as a unique model for mammalian cardiac regeneration, exhibiting enhanced recovery after myocardial infarction compared to commonly used laboratory mouse strains. However, the cellular and molecular mechanisms underlying this regenerative response remain poorly understood. In this study, we performed a comprehensive characterization of the metabolic adaptations to ischemic injury in cardiomyocytes of Acomys in comparison to the non-regenerative Mus Musculus. To investigate the transcriptomic and metabolomic profiles of cardiomyocytes in response to myocardial infarction, we utilized single-nucleus RNA sequencing (snRNA-seq) in sham-operated animals and 1, 3, and 7 days post-myocardial infarction. Complementary targeted metabolomics, stable isotope-resolved metabolomics, and functional mitochondrial assays were performed on heart tissues from both species to validate the transcriptomic findings and elucidate the metabolic adaptations in cardiomyocytes following ischemic injury. Transcriptomic analysis revealed that Acomys cardiomyocytes upregulate genes associated with glycolysis, the pentose phosphate pathway, and glutathione metabolism while downregulating genes involved in oxidative phosphorylation following injury. These metabolic changes were linked to decreased production of reactive oxygen species and increased antioxidant capacity, evidenced by the upregulation of genes such as Prdx1, Sod1, Sod2, and G6pd. Our targeted metabolomic studies supported these findings, showing a shift from fatty acid oxidation to glycolysis and ancillary biosynthetic pathways in Acomys cardiomyocytes post-injury. Functional mitochondrial studies indicated a higher reliance on glycolysis in Acomys compared to Mus, underscoring the unique metabolic adaptations of Acomys cardiomyocytes. Stable isotope tracing experiments confirmed a shift in glucose utilization from oxidative phosphorylation in Acomys. In conclusion, our study identifies unique metabolic adaptations in Acomys cardiomyocytes that contribute to their enhanced regenerative capacity following myocardial infarction. These findings provide novel insights into the role of metabolism in regulating cardiomyocyte proliferation and cardiac repair in adult mammals. By targeting the specific metabolic pathways and regulators identified in Acomys, such as glycolytic enzymes and PCK2, we may be able to develop innovative therapies to promote cardiac regeneration in patients with ischemic heart disease. Our work highlights the importance of metabolic flexibility in determining cardiomyocyte regenerative responses and establishes Acomys as a valuable model for studying cardiac regeneration in adult mammals. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=119 SRC="FIGDIR/small/595229v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@dba53aorg.highwire.dtl.DTLVardef@3c8a74org.highwire.dtl.DTLVardef@a60251org.highwire.dtl.DTLVardef@e2142c_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

Retinal neuroanatomy of two emerging model organisms, the spiny mouse (Acomys dimidiatus) and the Mongolian gerbil (Meriones unguiculatus)

PurposeDegenerative eye diseases such as macular degeneration and retinitis pigmentosa slowly deteriorate vision, ultimately leading to blindness. Current research with laboratory animal models largely utilizes small mammals that are nocturnal and lack the ability to restore lost vision. In contrast, the Mongolian gerbil is a diurnal rodent with good photopic vision, and the eastern spiny mouse is a small desert-dwelling rodent with remarkable regenerative capabilities. The goal of this study was to identify several antibodies that detect retinal cell classes in Meriones and Acomys, and to describe the retinal anatomy of these two species in comparison to outbred laboratory mice (Mus musculus). MethodsRetinal sections were obtained from adult eyes and subjected to histological or immuno-staining with antibodies for various retinal cell types. Sections were imaged by light, fluorescence, and confocal microscopy, assessing cell number and morphology. Cell density, morphology, and placement were compared between species qualitatively and quantitatively. ResultsImmunohistochemical visualization and analysis of all general classes of retinal neurons and Muller glia revealed a classic assembly of retinal cells with a few deviations compared to Mus. Meriones displayed the highest density of cone photoreceptors and Acomys the lowest. A higher density of bipolar cell bodies in the proximal portion of the inner nuclear layer was observed in both Acomys and Meriones compared to Mus, and both species exhibited an increase in amacrine cell density compared to Mus. ConclusionWe have characterized similarities and differences in the retinal anatomy and cellular density between Meriones, Acomys, and Mus. We identified several commercially available antibodies that reliably detect retinal cell types in the Acomys and Meriones retina. Our results provide a foundation for future research into the visual system adaptations of both of these interesting rodent species.

cell biology↗

bioRxiv2023

Neural crest cells give rise to non-myogenic mesenchymal tissue in the adult murid ear pinna

Despite being a major target of reconstructive surgery, development of the external ear pinna remains poorly studied. As a craniofacial organ highly accessible to manipulation and highly conserved among mammals, the ear pinna represents a valuable model for the study of appendage development and wound healing in the craniofacial complex. Here we provide a cellular characterization of late gestational and postnatal ear pinna development in Mus musculus and Acomys cahirinus and demonstrate that ear pinna development is largely conserved between these species. Using Wnt1-cre;ROSAmT/mG mice we find that connective tissue fibroblasts, elastic cartilage, dermal papilla cells, dermal sheath cells, vasculature, and adipocytes in the adult pinna are derived from cranial crest. In contrast, we find that skeletal muscle and hair follicles are not derived from neural crest cells. Cellular analysis using the naturally occurring short ear mouse mutant shows that elastic cartilage does not develop properly in distal pinna due to impaired chondroprogenitor proliferation. Interestingly, while chondroprogenitors develop in a mostly continuous sheet, the boundaries of cartilage loss in the short ear mutant strongly correlate with locations of vasculature-conveying foramen. Concomitant with loss of elastic cartilage we report increased numbers of adipocytes, but this seems to be a state acquired in adulthood rather than a developmental abnormality. In addition, chondrogenesis remains impaired in the adult mid-distal ear pinna of these mutants. Together these data establish a developmental basis for the study of the ear pinna with intriguing insights into the development of elastic cartilage.

developmental biology↗

bioRxiv2022

An ERK-dependent molecular switch antagonizes fibrosis and promotes regeneration in spiny mice (Acomys)

Although most mammals heal wounds with scar tissue, spiny mice (Acomys cahirinus) naturally regenerate skin and complex musculoskeletal tissues. The core signaling pathways driving mammalian tissue regeneration are poorly characterized. Here, we show that MAPK/ERK signaling acts as a major hub directing cellular injury responses towards regeneration. While immediate ERK activation was a shared feature of scarring (Mus musculus) and regenerating (Acomys) wounds, ERK activity was only sustained during regeneration. Upon ERK inhibition, the Acomys wound microenvironment exhibited key hallmarks of fibrosis, including a pro-scarring matrisome, epidermal differentiation and reduced proliferation. These findings indicate that ERK inhibition shifts tissue regeneration towards fibrosis. Conversely, the ectopic release of ERK activators (FGF/Neuregulin) in fibrotic scars, stimulated a pro-regenerative matrisome, cell proliferation and hair follicle neogenesis, thus promoting skin regeneration. Our data provide new insights into why some mammals regenerate better than others and open avenues to reverse fibrosis in favor of regeneration. TeaserFGF2 and NRG1 stimulate skin and hair follicle regeneration through ERK-mediated control of cell behavior in adult mammals.

cell biology↗

bioRxiv2021

Sonic hedgehog is essential for proximal-distal outgrowth of the limb bud in salamanders

The developing forelimb has been a foundational model to understand how specified progenitor cells integrate genetic information to produce the tetrapod limb bauplan (1, 2). Although the reigning hypothesis is that all tetrapods develop limbs in a similar manner, recent work suggests that urodeles have evolved a derived mode of limb development (3-5). Here we demonstrate through pharmacological and genetic inactivation of Sonic hedgehog (Shh) signaling in axolotls that Shh directs expansion and survival of limb progenitor cells in addition to patterning the limb across the proximodistal and antero-posterior axis. In contrast to inactivation of Shh in mouse or chick embryos where a humerus, radius and single digit develop (6-9), Shh crispant axolotls completely lack forelimbs. In rescuing limb development by implanting SHH-N protein beads into the nascent limb field of Shh-crispants, we show that the limb field is specified in the absence of Shh and that hedgehog pathway activation is required to initiate proximodistal outgrowth. When the derived nature of salamander limb development is placed in a phylogenetic context, it generates a new hypothesis where the ability to regenerate an entire tetrapod limb may have evolved uniquely among urodeles. TeaserShh is essential for salamander limb development

developmental biology↗

bioRxiv2021

A constitutively expressed fluorescence ubiquitin cell cycle indicator (FUCCI) in axolotls for studying tissue regeneration

Regulation of cell cycle progression is essential for cell proliferation during regeneration following injury. After appendage amputation, the axolotl (Ambystoma mexicanum) regenerates missing structures through an accumulation of proliferating cells known as the blastema. To study cell division during blastema growth, we generated a transgenic line of axolotls that ubiquitously expresses a bicistronic version of the Fluorescent Ubiquitination-based Cell Cycle Indicator (FUCCI). We demonstrate near-ubiquitous expression of FUCCI expression in developing and adult tissues and validate these expression patterns with DNA synthesis and mitosis phase markers. We demonstrate the utility of FUCCI for live and whole-mount imaging, showing the predominantly local contribution of cells during limb and tail regeneration. We also show that spinal cord amputation results in increased proliferation at least 5 mm from the injury. Finally, we use multimodal staining to provide cell type information for cycling cells by combining fluorescence in-situ hybridization, EdU click-chemistry, and immunohistochemistry on a single FUCCI tissue section. This new line of animals will be useful for studying cell cycle dynamics using in-situ endpoint assays and in-vivo imaging in developing and regenerating animals. Summary statementWe generated a ubiquitous transgenic fluorescence ubiquitin cell cycle indicator (FUCCI) axolotl line for examination of cell cycle dynamics during tissue regeneration.

developmental biology↗

bioRxiv2020

Evaluating spiny mice (Acomys) as a model for cardiac research

Complex tissue regeneration is extremely rare among adult mammals. An exception, however, is the superior tissue healing of multiple organs in spiny mice (Acomys). While Acomys species exhibit the remarkable ability to heal complex tissue with minimal scarring, little is known about their cardiac structure and response to cardiac injury. In this study, we first examined baseline Acomys cardiac anatomy and function in comparison with the commonly used laboratory Mus strains (C57BL6 and SWR). Our results demonstrated comparable cardiac anatomy and function between Acomys and Mus, but Acomys exhibited a higher percentage of cardiomyocytes exhibiting immature characteristics. In response to myocardial infarction, all animals experienced a comparable level of initial cardiac damage. However, Acomys demonstrated superior ischemic tolerance and cytoprotection in response to injury as evidenced by cardiac functional stabilization, higher survival rate and smaller scar size 50 days after injury compared to the inbred and outbred mouse strains. Overall, these findings demonstrate augmented myocardial preservation in spiny mice post-MI and establish Acomys as a new adult mammalian model for cardiac research.

developmental biology↗

bioRxiv2020

Spiny mice (Acomys) exhibit attenuated hallmarks of aging and rapid cell turnover after UV exposure in the skin epidermis

The study of long-lived and regenerative animal models has revealed diverse protective responses to stressors such as aging and tissue injury. Spiny mice (Acomys) are a unique mammalian model of skin regeneration, but their response to other types of physiological skin damage have not been investigated. In this study, we examine how spiny mice skin responds to acute UVB damage or chronological aging compared to non-regenerative C57Bl/6 mice (M. musculus). We find that, compared to M. musculus, the skin epidermis in A. cahirinus experiences a similar UVB-induced increase in basal cell proliferation but exhibits increased epidermal turnover. Notably, A. cahirinus uniquely form a suprabasal layer co-expressing Keratin 14 and Keratin 10 after UVB exposure concomitant with reduced epidermal inflammatory signaling and reduced markers of DNA damage. In the context of aging, old M. musculus animals exhibit typical hallmarks including epidermal thinning, increased inflammatory signaling and senescence. However, these age-related changes are absent in old A. cahirinus skin. Overall, we find that A. cahirinus have evolved novel responses to skin damage that reveals new aspects of its regenerative phenotype.

cell biology↗

bioRxiv2019

Mammalian musculoskeletal regeneration is associated with reduced inflammatory cytokines and an influx of T cells.

Whether the immune response to injury contributes to tissue regeneration is not well understood. We quantified systemic and local cytokines during ear pinna repair to provide the first comprehensive comparison of the immune response to injury between mammalian regeneration (A. cahirinus and A. percivali) and fibrotic repair (M. musculus). Importantly, by comparing laboratory-reared and wild-caught animals we identified responses specifically associated with healing outcome. Fibrotic repair showed a greater local release of IL-6, CCL2 and CXCL1. Conversely, regeneration showed decreased circulating IL-5, IL-6, IL-17, CCL3 and CXCL1 and increased local IL-12 and IL-17. The differential IL-6 response was substantiated by increased pSTAT3 during the inflammatory phase of fibrotic repair and with blastema formation and tissue morphogenesis in Acomys. COX-2 inhibition was not sufficient to induce regeneration. Interestingly, a unique influx of lymphocytes was coupled with regeneration and RNA-expression analysis suggested they were regulatory T cells. Together, the data support regeneration-specific inflammation and T cell responses in Acomys.

immunology↗

bioRxiv2019

Inhibiting fibroblast aggregation in skin wounds unlocks developmental pathway to regeneration

Salamanders are capable of full-thickness skin regeneration where removal of epidermis, dermis and hypodermis results in scar-free repair. What remains unclear is whether regeneration of these tissues recapitulates the cellular events of skin development or occurs through a process unique to regenerative healing. Unfortunately, information on the post-embryonic development of salamander skin is severely lacking, having focused on compartments or cell types, but never on the skin as a complete organ. By examining coordinated development of the epidermis and dermis in axolotls we establish six distinct stages of skin development (I-VI): I-V for normally paedomorphic adults and a sixth stage following metamorphosis. Raising animals either in isolation (zero density pressure) or in groups (density pressure) we find that skin development progresses as a function of animal size and that density directly effects developmental rate. Using keratins, p63, and proliferative markers, we show that although the epidermis lacks visible stratification at early stages of skin development, when the dermis transforms into the stratum spongiosum and stratum compactum keratinocytes differentiate into at least three distinct phenotypes that reveal a cryptic stratification program uncoupled from metamorphosis. Lastly, comparing skin regeneration to skin development, we find that dermal regeneration occurs through a unique process, relying heavily on remodeling of the wound extracellular matrix, rather than proceeding through direct development of a dermal lamella produced by the epidermis. By preventing fibroblast influx into the wound bed using beryllium nitrate, we show that in the absence of fibroblast generated ECM production skin regeneration occurs through an alternate route that recapitulates development.

developmental biology↗