Systemic and local lipid adaptations underlie regeneration in Drosophila melanogaster and Ambystoma mexicanum.

In regenerating tissues, synthesis and remodeling of membranes rely on lipid turnover and transport. Our study addresses lipid adaptations in intestinal regeneration of Drosophila melanogaster and limb regeneration of Ambystoma mexicanum. We found changes in lipid profiles at different locations: transport, storage organs and regenerating tissues.

Atomic Force Microscopy Measurements of Cartilage in Intact and Regenerating Axolotl Limbs.

Mechanical forces provide important signals for normal cell function and pattern formation in developing tissues, and their role has been widely studied during embryogenesis and pathogenesis. Comparatively, little is known of these signals during animal regeneration. The axolotl is an important model organism for the study of regeneration, given its ability to fully restore many organs and tissues after injury, including missing cartilage and bone.

Axolotl mandible regeneration occurs through mechanical gap closure and a shared regenerative program with the limb.

The mandible plays an essential part in human life and, thus, defects in this structure can dramatically impair the quality of life in patients. Axolotls, unlike humans, are capable of regenerating their lower jaws; however, the underlying mechanisms and their similarities to those in limb regeneration are unknown. In this work, we used morphological, histological and transcriptomic approaches to analyze the regeneration of lateral resection defects in the axolotl mandible.

The salamander limb: a perfect model to understand imperfect integration during skeletal regeneration.

Limb regeneration in salamanders is achieved by a complex coordination of various biological processes and requires the proper integration of new tissue with old. Among the tissues found inside the limb, the skeleton is the most prominent component, which serves as a scaffold and provides support for locomotion in the animal. Throughout the years, researchers have studied the regeneration of the appendicular skeleton in salamanders both after limb amputation and as a result of fracture healing.

Multi-species atlas resolves an axolotl limb development and regeneration paradox.

Humans and other tetrapods are considered to require apical-ectodermal-ridge (AER) cells for limb development, and AER-like cells are suggested to be re-formed to initiate limb regeneration. Paradoxically, the presence of AER in the axolotl, a primary model organism for regeneration, remains controversial. Here, by leveraging a single-cell transcriptomics-based multi-species atlas, composed of axolotl, human, mouse, chicken, and frog cells, we first establish that axolotls contain cells with AER characteristics.

Axolotl Transgenesis via Injection of I-SceI Meganuclease or Tol2 Transposon System.

The axolotl (Ambystoma mexicanum ) has been widely used as an animal model for studying development and regeneration. In recent decades, the use of genetic engineering to alter gene expression has advanced our knowledge on the fundamental molecular and cellular mechanisms, pointing us to potential therapeutic targets. We present a detailed, step-by-step protocol for axolotl transgenesis using either I-SceI meganuclease or the mini Tol2 transposon system, by injection of purified DNA into one-cell stage eggs.

Embryonic Tissue and Blastema Transplantations.

Embryo grafts have been an experimental pillar in developmental biology, and particularly, in amphibian biology. Grafts have been essential in constructing fate maps of different cell populations and migratory patterns. Likewise, autografts and allografts in older larvae or adult salamanders have been widely used to disentangle mechanisms of regeneration.

Methods for Studying Appendicular Skeletal Biology in Axolotls.

The axolotl is a great model for studying cartilage, bone and joint regeneration, fracture healing, and evolution. Stainings such as Alcian Blue/Alizarin Red have become workhorses in skeletal analyses, but additional methods complement the detection of different skeletal matrices. Here we describe protocols for studying skeletal biology in axolotls, particularly Alcian Blue/Alizarin Red staining, microcomputed tomography (μCT) scan and live staining of calcified tissue.

Osteoclast-mediated resorption primes the skeleton for successful integration during axolotl limb regeneration.

Early events during axolotl limb regeneration include an immune response and the formation of a wound epithelium. These events are linked to a clearance of damaged tissue prior to blastema formation and regeneration of the missing structures. Here, we report the resorption of calcified skeletal tissue as an active, cell-driven, and highly regulated event.

assessment of mechanical properties during axolotl development and regeneration using confocal Brillouin microscopy.

In processes such as development and regeneration, where large cellular and tissue rearrangements occur, cell fate and behaviour are strongly influenced by tissue mechanics. While most well-established tools probing mechanical properties require an invasive sample preparation, confocal Brillouin microscopy captures mechanical parameters optically with high resolution in a contact-free and label-free fashion. In this work, we took advantage of this tool and the transparency of the highly regenerative axolotl to probe its mechanical properties for the first time.

Local problems need global solutions: The metabolic needs of regenerating organisms.

The vast majority of species that belong to the plant or animal kingdom evolved with two main strategies to counter tissue damage-scar formation and regeneration. Whereas scar formation provides a fast and cost-effective repair to exit life-threatening conditions, complete tissue regeneration is time-consuming and requires vast resources to reinstall functionality of affected organs or structures. Local environments in wound healing are widely studied and findings have provided important biomedical applications.

Meeting report: Salamander models in cross-disciplinary biological research meeting.

The third annual meeting on "Salamander Models in Cross-disciplinary Biological Research" took place online on August 2021, bringing together over 200 international researchers using salamanders as research models and encompassing diverse fields, ranging from Development and Regeneration through to Immunology, Pathogenesis, and Evolution. The event was organized by Maximina H. Yun (Center for Regenerative Therapies Dresden, Germany) and Tatiana Sandoval-Guzmán (TU Dresden, Germany) with the generous support of the Deutsche Forschungsgemeinschaft, the Center for Regenerative Therapies Dresden, Technische Universität Dresden, and the Company of Biologists.

Postembryonic development and aging of the appendicular skeleton in Ambystoma mexicanum.

Background: The axolotl is a key model to study appendicular regeneration. The limb complexity resembles that of humans in structure and tissue components; however, axolotl limbs develop postembryonically. In this work, we evaluated the postembryonic development of the appendicular skeleton and its changes with aging.

HOXA13 in etiology and oncogenic potential of Barrett's esophagus.

Barrett's esophagus in gastrointestinal reflux patients constitutes a columnar epithelium with distal characteristics, prone to progress to esophageal adenocarcinoma. HOX genes are known mediators of position-dependent morphology. Here we show HOX collinearity in the adult gut while Barrett's esophagus shows high HOXA13 expression in stem cells and their progeny.

The limb enhancer marks an adult subpopulation of injury-responsive dermal fibroblasts.

The heterogeneous properties of dermal cell populations have been posited to contribute toward fibrotic, imperfect wound healing in mammals. Here we characterize an adult population of dermal fibroblasts that maintain an active enhancer which originally marked mesenchymal limb progenitors. In contrast to their abundance in limb development, postnatal enhancer-positive cells (Prrx1) make up a small subset of adult dermal cells (∼0.

The journey of cells through regeneration.

The process of building an organ, appendage, or organism requires the precise coordination of cells in space and time. Regeneration of those same tissues adds an additional element of complexity, emerging from the chaos of disease or injury to build a mass of progenitors from mature tissue. Translating insights from natural examples of tissue regeneration into engineered regenerative therapies requires a deep understanding of the journey of a cell directly following injury to its contribution to functional, scaled replacement tissue.

Optimized axolotl (Ambystoma mexicanum) husbandry, breeding, metamorphosis, transgenesis and tamoxifen-mediated recombination.

The axolotl (Mexican salamander, Ambystoma mexicanum) has become a very useful model organism for studying limb and spinal cord regeneration because of its high regenerative capacity. Here we present a protocol for successfully mating and breeding axolotls in the laboratory throughout the year, for metamorphosing axolotls by a single i.p.

Fundamental differences in dedifferentiation and stem cell recruitment during skeletal muscle regeneration in two salamander species.

Salamanders regenerate appendages via a progenitor pool called the blastema. The cellular mechanisms underlying regeneration of muscle have been much debated but have remained unclear. Here we applied Cre-loxP genetic fate mapping to skeletal muscle during limb regeneration in two salamander species, Notophthalmus viridescens (newt) and Ambystoma mexicanum (axolotl).

Germline transgenic methods for tracking cells and testing gene function during regeneration in the axolotl.

The salamander is the only tetrapod that regenerates complex body structures throughout life. Deciphering the underlying molecular processes of regeneration is fundamental for regenerative medicine and developmental biology, but the model organism had limited tools for molecular analysis. We describe a comprehensive set of germline transgenic strains in the laboratory-bred salamander Ambystoma mexicanum (axolotl) that open up the cellular and molecular genetic dissection of regeneration.

Foamy virus for efficient gene transfer in regeneration studies.

Background: Molecular studies of appendage regeneration have been hindered by the lack of a stable and efficient means of transferring exogenous genes. We therefore sought an efficient integrating virus system that could be used to study limb and tail regeneration in salamanders.

Results: We show that replication-deficient foamy virus (FV) vectors efficiently transduce cells in two different regeneration models in cell culture and in vivo.

Neuroendocrine control of female reproductive function by the activin receptor ALK7.

Activins are critical components of the signaling network that controls female reproduction. However, their roles in hypothalamus, and the specific functions of their different receptors, have not been elucidated. Here, we investigated the expression and function of the activin receptor ALK7 in the female reproductive axis using Alk7-knockout mice.

GDNF and GFRalpha1 promote formation of neuronal synapses by ligand-induced cell adhesion.

The establishment of synaptic connections requires precise alignment of pre- and postsynaptic terminals. The glial cell line-derived neurotrophic factor (GDNF) receptor GFRalpha1 is enriched at pre- and postsynaptic compartments in hippocampal neurons, suggesting that it has a function in synapse formation. GDNF triggered trans-homophilic binding between GFRalpha1 molecules and cell adhesion between GFRalpha1-expressing cells.

Central injection of senktide, an NK3 receptor agonist, or neuropeptide Y inhibits LH secretion and induces different patterns of Fos expression in the rat hypothalamus.

Arcuate neurokinin B (NKB) neurons express estrogen receptor-alpha and are strongly modulated by gonadal steroids. Although numerous studies suggest that NKB neurons participate in the reproductive axis, there is no information on the regulation of luteinizing hormone (LH) secretion by NKB or its receptor, NK3. In the present study, we determined if central injection of senktide, a selective NK3 receptor agonist, would alter serum LH in ovariectomized, estrogen-primed rats.