Regenerative Biology Research Articles

Tail Tales: What We Have Learned About Regeneration from Xenopus Laevis Tadpoles

This review explores the regenerative capacity of Xenopus laevis, focusing on tail regeneration, as a model to uncover cellular, molecular, and developmental mechanisms underlying tissue repair. X. laevis tadpoles provide unique insights into regenerative biology due to their regeneration-competent and -incompetent stages and ability to regrow complex structures in the tail, including the spinal cord, muscle, and skin, after amputation. The review delves into the roles of key signaling pathways, such as those involving reactive oxygen species (ROS) and signaling molecules like BMPs and FGFs, in orchestrating cellular responses during regeneration. It also examines how mechanotransduction, epigenetic regulation, and metabolic shifts influence tissue restoration. Comparisons of regenerative capacity with other species shed light on the evolutionary loss of regenerative abilities and underscore X. laevis as an invaluable model for understanding the constraints of tissue repair in higher organisms. This comprehensive review synthesizes recent findings, suggesting future directions for exploring regeneration mechanisms, with potential implications for advancing regenerative medicine.

Temporal microbiome changes in axolotl limb regeneration: Stage-specific restructuring of bacterial and fungal communities with a Flavobacterium bloom during blastema proliferation.

The intricate relationship between regeneration and microbiota has recently gained attention, spanning diverse model organisms. Axolotl (Ambystoma mexicanum) is a critically endangered salamander species and a model organism for regenerative and developmental biology. Despite its significance, a noticeable gap exists in understanding the interplay between axolotl regeneration and its microbiome. Here, we analyse in depth bacterial 16S rRNA amplicon dataset that we reported before as data resource and profile fungal community by sequencing ITS amplicons at the critical stages of limb regeneration (0-1-4-7-30-60 days post amputation, 'dpa'). Results reveal a decline in richness and evenness in the course of limb regeneration, with bacterial community richness recovering beyond 30 dpa unlike fungi community. Beta diversity analysis reveals precise restructuring of the bacterial community along the three phases of limb regeneration, contrasting with less congruent changes in the fungal community. Temporal dynamics of the bacterial community highlight prevalent anaerobic bacteria in initiation phase and Flavobacterium bloom in the early phase correlating with limb blastema proliferation. Predicted functional analysis mirrors these shifts, emphasising a transition from amino acid metabolism to lipid metabolism control. Fungal communities shift from Blastomycota to Ascomycota dominance in the late regeneration stage. Our findings provide ecologically relevant insights into stage specific role of microbiome contributions to axolotl limb regeneration.

Extraordinary model systems for regeneration.

Regeneration is the remarkable phenomenon through which an organism can regrow lost or damaged parts with fully functional replacements, including complex anatomical structures, such as limbs. In 2019, Development launched its 'Model systems for regeneration' collection, a series of articles introducing some of the most popular model organisms for studying regeneration in vivo. To expand this topic further, this Perspective conveys the voices of five expert biologists from the field of regenerative biology, each of whom showcases some less well-known, but equally extraordinary, species for studying regeneration.

Exploring the Potential of Skin Cell Culture and the Vital Role of Skin Grafts in Regenerative Medicine and Biology

The skin is acknowledged as the biggest organ, covering the exterior of the body and serving as a physical barrier. The integumentary system is made up of three layers of tissue: the epidermis, dermis, and hypodermis. For transplantation, epidermal cell cultures have been around for a while. The epidermal stem cells can proliferate and self-renew in a manner that allows for rapid healing since they are unipotent, meaning they can only produce one type of cell. In therapeutic terms, cultured keratinocytes have been described as an autologous cell-based therapy that provides a source of autologous tissue, reducing the need for large donor sites and minimizing the risk of immune rejection. This review explores the composition and functioning of the skin’s extracellular matrix, along with strategies to incorporate ECM components into the cell culture techniques. Rebuilding skin flaws without consideration for side effects is skin grafting. The tissue lacks its circulatory supply and must receive it from the bed in which it is inserted. The skin cells have contributed to developing skin graft and tissue engineering approaches for repairing damaged skin. Similar to grafting, the skin graft is divided into sections based on the quantity of dermis involved: split-thickness skin and full-thickness skin. Transplanting autologous keratinocytes is an alternative to autologous skin grafting. In the wound bed, epidermal stem cells encourage angiogenesis. After invading the fibrin wound clot, angiogenic capillary sprouts form a microvascular network throughout the granulation tissue in a few days. In this article, authors will review the current methods and application of skin cell culture for transplantation including different cell sources, culture conditions, and transplantation techniques. The future direction of this approach is in the context of regenerative medicine and tissue engineering.

Exploring the biogeography, morphology, and phylogeny of the condylostomatid ciliates (Alveolata, Ciliophora, Heterotrichea), with establishment of four new Condylostoma species and a revision including redescriptions of five species found in China

Species of the ciliate class Heterotrichea Stein, 1859 are a cosmopolitan group of unicellular eukaryotic microorganisms, many of which have been widely used as models in various fields of research such as regenerative biology, functional ecology, environmental toxicology, and symbiotic behavior. However, species identification in the heterotrich family Condylostomatidae, especially the most species-rich and type genus Condylostoma Bory de Saint-Vincent, 1824, remains challenging due to incomplete original descriptions, few reliable distinguishing characters, and overlapping features between different species. This study presents an updated revision of Condylostoma and its related genus Condylostomides da Silva Neto, 1994 based on descriptions of five species, including nine populations collected from China, using both morphological and molecular methods. The main findings are as follows: (1) 43 nominal species and about 130 populations are reviewed, resulting in the recognition of 30 valid species of Condylostoma and eight valid species of Condylostomides; (2) keys, synonyms, biogeographic distributions and amended/improved diagnoses of all valid species are provided; (3) based on the available data, four new Condylostoma species (C. marinum sp. nov., C. petzi sp. nov., C. villeneuvei sp. nov., and C. microstomum sp. nov.), one new combination (Condylostomides minimus (Dragesco, 1954) comb. nov. & nom. corr.), and two corrected names (Condylostoma ancestrale Villeneuve-Brachon, 1940 nom. corr. and Condylostomides nigrus (Dragesco, 1960) nom. corr.) are suggested; (4) cryptic species are detected and proposed for the first time to form the Condylostoma curvum species complex; (5) three highly confusing Condylostoma species, C. kris, C. spatiosum, and C. minutum, are redefined for the first time based on modern taxonomic methods; (6) a ‘flagship’ species, Condylostomides coeruleus, is recorded for the first time from the continent of Asia, substantially expanding its biogeography; (7) ciliature adjacent to the distal end of the paroral membrane within the family Condylostomatidae is uniformly defined as frontal membranelles and is classified into three patterns according to the arrangement of kinetosomes, which serve as important key features.

Перспективи використання нанотехнологій у біологічних дослідженнях нового покоління

Nanotechnologies hold significant potential to revolutionize biological research for future generations. This article explores the current state, potential applications, and future prospects of nanotechnologies in biological research. The relevance of this issue is driven by the need for advanced tools to study complex biological phenomena at the nanoscale. The aim of the article is to assess how nanotechnologies can enhance our understanding of biological systems and enable innovative research approaches. The article presents the results of recent scientific studies demonstrating the impact of nanotechnologies on biological research, including advancements in visualization, drug delivery, and biosensing. Nanomaterials such as quantum dots and nanoscale biosensors enable new insights into cellular processes and disease mechanisms. Nano-engineered drug delivery systems have shown promising results for targeted therapy, reducing side effects, and improving treatment efficacy. The conclusions underscore the transformative potential of nanotechnologies in biological research, contributing to advancements in fields such as personalized medicine, regenerative biology, and biomaterials engineering. Nanotechnologies enable precise control and investigation of biological systems, offering new pathways for scientific discoveries and technological innovations. This article outlines future research directions in this field, addressing challenges such as biosafety, scalability, and integration of nanopdevices into complex biological systems. Resolving these issues will unlock further opportunities for applying nanotechnologies in biological research. Future investigations involve developing multifunctional nanosystems capable of real-time monitoring, precise cellular-level interventions, and integration with advanced data analytics to gain comprehensive biological insights. Thus, nanotechnologies form the foundation for transforming next-generation biological research, promising innovative tools and methodologies to study complex processes occurring in the nanoscale realm.

David L. Stocum (1939–2023): Authority in regenerative biology, passionate educator, visionary administrative leader, and cherished colleague and friend

David L. Stocum (1939–2023): Authority in regenerative biology, passionate educator, visionary administrative leader, and cherished colleague and friend

The people behind the papers - Bridget Ostrem, Nuria Domínguez-Iturza and Paola Arlotta.

Maternal immune activation can affect the development of embryos, but the underlying mechanisms have been unclear. In a new study, Bridget Ostrem and colleagues show that embryonic microglia detect maternal inflammation, resulting in transcriptional changes in neighbouring brain-cell types. To find out more about the behind the paper story, we caught up with the first authors, Bridget Ostrem and Nuria Domínguez-Iturza, and corresponding author Paola Arlotta, Chair of the Department of Stem Cell and Regenerative Biology at Harvard University, USA.

Tail and Spinal Cord Regeneration in Urodelean Amphibians.

Urodelean amphibians can regenerate the tail and the spinal cord (SC) and maintain this ability throughout their life. This clearly distinguishes these animals from mammals. The phenomenon of tail and SC regeneration is based on the capability of cells involved in regeneration to dedifferentiate, enter the cell cycle, and change their (or return to the pre-existing) phenotype during de novo organ formation. The second critical aspect of the successful tail and SC regeneration is the mutual molecular regulation by tissues, of which the SC and the apical wound epidermis are the leaders. Molecular regulatory systems include signaling pathways components, inflammatory factors, ECM molecules, ROS, hormones, neurotransmitters, HSPs, transcriptional and epigenetic factors, etc. The control, carried out by regulatory networks on the feedback principle, recruits the mechanisms used in embryogenesis and accompanies all stages of organ regeneration, from the moment of damage to the completion of morphogenesis and patterning of all its structures. The late regeneration stages and the effects of external factors on them have been poorly studied. A new model for addressing this issue is herein proposed. The data summarized in the review contribute to understanding a wide range of fundamentally important issues in the regenerative biology of tissues and organs in vertebrates including humans.

Establishment of Transgene-Free Porcine Induced Pluripotent Stem Cells.

Although protocols to generate authentic transgene-free mouse and human induced pluripotent stem cells (iPSCs) are now well established, standard methods for reprogramming porcine somatic cells still suffer from low efficiency and transgene retention. The Basic Protocol describes reprogramming procedures to establish transgene-free porcine iPSCs (PiPSCs) from porcine fibroblasts. This method uses episomal plasmids encoding POU5F1, SOX2, NANOG, KLF4, SV40LT, c-MYC, LIN28A, and microRNA-302/367, combined with an optimized medium, to establish PiPSC lines. Support protocols describe the establishment and characterization of clonal PiPSC lines, as well as the preparation of feeder cells and EBNA1 mRNA. This optimized, step-by-step approach tailored to this species enables the efficient derivation of PiPSCs in ∼4 weeks. The establishment of transgene-free PiPSCs provides a new and valuable model for studies of larger mammalian species' development, disease, and regenerative biology. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Reprogramming of porcine fibroblasts with episomal plasmids Support Protocol 1: Preparation of mouse embryonic fibroblasts for feeder layer Support Protocol 2: Preparation of in vitro-transcribed EBNA1 mRNA Support Protocol 3: Establishment of clonal porcine induced pluripotent stem cell (PiPSC) lines Support Protocol 4: PiPSC characterization: Genomic DNA PCR and RT-PCR Support Protocol 5: PiPSC characterization: Immunostaining.

DNA origami scaffold promoting nerve guidance and regeneration.

Self-assembly of biological elements into biomimetic cargo carriers for targeting and delivery is a promising approach. However, it still holds practical challenges. We developed a functionalization approach of DNA origami (DO) nanostructures with neuronal growth factor (NGF) for manipulating neuronal systems. NGF bioactivity and its interactions with the neuronal system were demonstrated in vitro and in vivo models. The DO elements fabricated by molecular self-assembly have manipulated the surrounding environment through static spatially and temporally controlled presentation of ligands to the cell surface receptors. Our data showed effective bioactivity in differentiating PC12 cells in vitro. Furthermore, the DNA origami NGF (DON) affected the growth directionality and spatial capabilities of dorsal root ganglion neurons in culture by introducing a chemotaxis effect along a gradient of functionalized DO structures. Finally, we showed that these elements provide enhanced axonal regeneration in a rat sciatic nerve injury model in vivo. This study is a proof of principle for the functionality of DO in neuronal manipulation and regeneration. The approach proposed here, of an engineered platform formed out of programmable nanoscale elements constructed of DO, could be extended beyond the nervous system and revolutionize the fields of regenerative medicine, tissue engineering, and cell biology.

Low expectations within conservative wing of discourse coalition for innovation and technoscience: integrating vanguard visions to therapeutic consent

Drawing on the sociology of expectations, this paper inquires what objects, promises, and audiences are invoked in two examples of biotechnology discourse on organoids, MCELS (Multicellular Engineered Living Systems) in the USA and REBIRTH (From REgenerative BIology to Reconstructive THerapy) in Germany, and how that affects therapeutic consent. Therapeutic consent discussion in the literature has been focusing on singular discourse on the objects of biotechnology. This paper focuses on making of organoids embedded in two very large research projects of biotechnology in two comparative cases to fill the gap between cultures of imaginations and discourses. The paper claims that (a) both projects are connected through shared objects within vanguard visions joined through a discourse coalition. The discourse coalitions that are making them further can be connected at the object level both by the low expectations and the techno-scientific imaginaries that are more relevant to public imagination by nested frameworks of vanguard visions and sociotechnical imaginaries. This connection is necessary for the object to be considered within the research and development of the object, whereas when the research programme is finished and the object itself is delivered, the low expectation and the calibration thereafter is dependent on this network (b) When the object [organoid] itself is a research object and a part of a discourse coalition is and an applied healthcare object at the same time, lowering of expectations and recalibration of the higher expectations are necessary for debates around consent as enabling conditions of consent in the very first place.

Exploring stem cell frontiers: definitions, challenges, and perspectives for regenerative medicine.

Each year, the European Summer School on Stem Cell Biology and Regenerative Medicine (SCSS) attracts early-career researchers and actively practicing clinicians who specialise in stem cell and regenerative biology. The 16th edition of this influential course took place from 12th to 19th September 2023 on the charming Greek island of Spetses. Focusing on important concepts and recent advances in stem cells, the distinguished faculty included experts spanning the spectrum from fundamental research to clinical trials to market-approved therapies. Alongside an academically intensive programme that bridges the various contexts of stem cell research, delegates were encouraged to critically address relevant questions in stem cell biology and medicine, including broader societal implications. Here, we present a comprehensive overview and key highlights from the SCSS 2023.

Periodontal tissue regeneration: current therapeutic strategies and future directions in further research

Chronic and progressive destruction/damage of the periodontal tissues resulted from periodontitis is the leading cause of tooth loss in adults. Traditional periodontal therapies such as scaling and root planning or flap surgery have demonstrated effective in controlling local inflammation and in suppressing/arresting the disease progression of periodontitis. However, those infection control measures cannot help to regenerate lost periodontal tissues to a statistically or clinically significant degree. Although some successes regarding the reduction of the intrabony defect and maintenance of the periodontal homeostasis have been achieved in periodontal regenerative procedures, comprising but not limited to guided tissue regeneration (GTR) or bone grafting technique, the restorative effectiveness of the architecture and function of the lost or injured tissues is far from our clinical expectation. The use of the concept, technique, and method of tissue engineering for periodontal regeneration is a hotspot and animal studies have shown interesting outcomes in terms of functional regeneration of lost/damaged support tissues in the periodontium, including alveolar bone, periodontal ligament, and cementum. However, numerous issues need to be addressed before those regenerative approaches can be responsibly transformed to novel clinical therapies. Recently, paradigm that induces homing of host stem cells to site of the periodontium and encourage the body's innate capability to repair is a new research field termed endogenous regeneration. Given that endogenous regenerative technique avoids ex-vivo cell culture and transplantation, it should be relatively easier to be used in the treatment of clinical patients. Due to the limited oral microenvironment and harsh periodontal local condition for tissue regeneration, as well as poor understanding of periodontal regenerative biology, there is still a long way ahead to explore new effective, practical, and economical therapies to save and protect natural tooth and for combating highly prevalent periodontal disease.

Compensatory growth and recovery of cartilage cytoarchitecture after transient cell death in fetal mouse limbs

A major question in developmental and regenerative biology is how organ size and architecture are controlled by progenitor cells. While limb bones exhibit catch-up growth (recovery of a normal growth trajectory after transient developmental perturbation), it is unclear how this emerges from the behaviour of chondroprogenitors, the cells sustaining the cartilage anlagen that are progressively replaced by bone. Here we show that transient sparse cell death in the mouse fetal cartilage is repaired postnatally, via a two-step process. During injury, progression of chondroprogenitors towards more differentiated states is delayed, leading to altered cartilage cytoarchitecture and impaired bone growth. Then, once cell death is over, chondroprogenitor differentiation is accelerated and cartilage structure recovered, including partial rescue of bone growth. At the molecular level, ectopic activation of mTORC1 correlates with, and is necessary for, part of the recovery, revealing a specific candidate to be explored during normal growth and in future therapies.

The people behind the papers - Margaret Hung and Robert Krauss.

Adhesion of muscle stem cells to their niche provides stable anchorage, and biochemical and biomechanical signals required for quiescence. In their work, Robert Krauss and colleagues reveal the role of catenin/cadherin-based adhesion interactions in maintaining niche localization. To find out more about their work, we spoke to the first author, Margaret Hung, and the corresponding author, Robert Krauss, Professor in Cell, Developmental and Regenerative Biology at the Icahn School of Medicine, Mount Sinai.

The future of liver transplantation.

Over the last 50 years, liver transplantation has evolved into a procedure routinely performed in many countries worldwide. Those able to access this therapy frequently experience a miraculous risk-benefit ratio, particularly if they face the imminently life-threatening disease. Over the decades, the success of liver transplantation, with dramatic improvements in early posttransplant survival, has aggressively driven demand. However, despite the emergence of living donors to augment deceased donors as a source of organs, supply has lagged far behind demand. As a result, rationing has been an unfortunate focus in recent decades. Recent shifts in the epidemiology of liver disease combined with transformative innovations in liver preservation suggest that the underlying premise of organ shortage may erode in the foreseeable future. The focus will sharpen on improving equitable access while mitigating constraints related to workforce training, infrastructure for organ recovery and rehabilitation, and their associated costs. Research efforts in liver preservation will undoubtedly blossom with the aim of optimizing both the timing and conditions of transplantation. Coupled with advances in genetic engineering, regenerative biology, and cellular therapies, the portfolio of innovation, both broad and deep, offers the promise that, in the future, liver transplantation will not only be broadly available to those in need but also represent a highly durable life-saving therapy.

A reproducible method to study traumatic injury-induced zebrafish brain regeneration.

Traumatic brain injury (TBI) can be caused by a sudden blow or jolt to the head, causing irreversible brain damage leading to cellular and functional loss. Mammals cannot repair such damage, which may increase the risk of progressive neurodegeneration. Unlike mammals, lower vertebrates such as zebrafish have the astounding capability to regenerate their brains. A model system would be of great value to study zebrafish brain regeneration. Here, we describe a physical method to induce traumatic injury in the zebrafish brain and outline a pipeline to utilize this model system to explore various aspects of brain regeneration. This will significantly advance the fields of regenerative biology and neuroscience. The method includes inducing TBI and validating this through histological assays, immunohistochemistry, and gene expression analysis. By using this model system, researchers will be able to gain valuable insights into the cellular and molecular mechanisms underlying brain regeneration. Understanding these mechanisms could lead to the identification of potential strategies to address neurodegenerative conditions in higher vertebrates.

Neuromodulation to guide circuit reorganization with regenerative therapies in upper extremity rehabilitation following cervical spinal cord injury.

Spinal cord injury (SCI) is a profoundly debilitating condition with no effective treatment to date. The complex response of the central nervous system (CNS) to injury and its limited regeneration capacity pose bold challenges for restoring function. Cervical SCIs are the most prevalent and regaining hand function is a top priority for individuals living with cervical SCI. A promising avenue for addressing this challenge arises from the emerging field of regenerative rehabilitation, which combines regenerative biology with physical medicine approaches. The hypothesis for optimizing gains in upper extremity function centers on the integration of targeted neurorehabilitation with novel cell- and stem cell-based therapies. However, the precise roles and synergistic effects of these components remain poorly understood, given the intricate nature of SCI and the diversity of regenerative approaches. This perspective article sheds light on the current state of regenerative rehabilitation for cervical SCI. Notably, preclinical research has yet to fully incorporate rehabilitation protocols that mimic current clinical practices, which often rely on neuromodulation strategies to activate spared circuits below the injury level. Therefore, it becomes imperative to comprehensively investigate the combined effects of neuromodulation and regenerative medicine strategies in animal models before translating these therapies to individuals with SCI. In cases of severe upper extremity paralysis, the advent of neuromodulation strategies, such as corticospinal tract (CST) and spinal cord stimulation, holds promise as the next frontier in enhancing the effectiveness of cell- and stem cell-based therapies. Future preclinical studies should explore this convergence of neuromodulation and regenerative approaches to unlock new possibilities for upper extremity treatment after SCI.

Regeneration in the dorids exemplified by Onchidoris muricata (Gastropoda, Nudibranchia)

Regenerative capabilities vary among different groups of invertebrates and despite being a highly abundant and diverse group of invertebrates with significant commercial and scientific value, gastropods remain relatively understudied in this respect. This work presents the first investigation of post–traumatic regeneration in the nudibranch mollusc Doridina, specifically focusing on Onchidoris muricata. Dorids have unique subepidermal calcite spicules that form a complex network inside the body. However, their capacity for complete or partial recovery, as well as the impact on regeneration of organs containing these spicules, has never been studied. We examined the regeneration of chemosensory organs (rhinophores) and dorsal body outgrowths (tubercle), both containing spicules and having different innervation. Our investigation explores three models of rhinophore regeneration: 1) after the removal of the apex and three lamellae of the rhinophore, 2) when the entire metameric lammelae part is removed, and 3) when the rhinophore is entirely excised. Additionally, two series of experiments were conducted to examine tubercle regeneration in the peribranchial region and in the rhinophore region. The study reveals varying regenerative abilities of these organs, likely linked to their different innervation patterns. Notably, we observed that the presence of the apex and spicules de novo synthesis influence the formation of the first rhinophore lamellae. The search for new patterns and mechanisms underlying the restoration of elements in the nervous system, muscular system, and solid skeleton can significantly contribute to our understanding of regenerative biology. This research expands our knowledge of nudibranch molluscs regeneration and the unique restoration of the subepidermal spicule complex. Furthermore, the regeneration of spicule-containing organs can be a model for studying the formation and structure of biomineralized structures, including their organic component.