The Warburg effect is necessary to promote glycosylation in the blastema during zebrafish tail regeneration

Epithelial-mesenchymal transition in tissue repair and degeneration

Epithelial-mesenchymal transitions (EMTs) are the epitome of cell plasticity in embryonic development and cancer; during EMT, epithelial cells undergo dramatic phenotypic changes and become able to migrate to form different tissues or give rise to metastases, respectively. The importance of EMTs in other contexts, such as tissue repair and fibrosis in the adult, has become increasingly recognized and studied. In this Review, we discuss the function of EMT in the adult after tissue damage and compare features of embryonic and adult EMT. Whereas sustained EMT leads to adult tissue degeneration, fibrosis and organ failure, its transient activation, which confers phenotypic and functional plasticity on somatic cells, promotes tissue repair after damage. Understanding the mechanisms and temporal regulation of different EMTs provides insight into how some tissues heal and has the potential to open new therapeutic avenues to promote repair or regeneration of tissue damage that is currently irreversible. We also discuss therapeutic strategies that modulate EMT that hold clinical promise in ameliorating fibrosis, and how precise EMT activation could be harnessed to enhance tissue repair.

SLAM-ITseq identifies that Nrf2 induces liver regeneration through the pentose phosphate pathway

The liver exhibits a remarkable capacity to regenerate following injury. Despite this unique attribute, toxic injury is a leading cause of liver failure. The temporal processes by which the liver senses injury and initiates regeneration remain unclear. Here, we developed a transgenic zebrafish model wherein hepatocyte-specific expression of uracil phosphoribosyltransferase (UPRT) enabled the implementation of SLAM-ITseq to investigate the nascent transcriptome during initiation of liver injury and regeneration. Using this approach, we identified a rapid metabolic transition from the fed to the fasted state that was followed by induction of the nuclear erythroid 2-related factor (Nrf2) antioxidant program. We find that activation of Nrf2 in hepatocytes is required to induce the pentose phosphate pathway (PPP) and improve survival following liver injury. Mechanistically, we demonstrate that inhibition of the PPP disrupts nucleotide biosynthesis to prevent liver regeneration. Together, these studies provide fundamental insights into the mechanism by which early metabolic adaptation to injury facilitates tissue regeneration.

Developmental regulation of cellular metabolism is required for intestinal elongation and rotation

Malrotation of the intestine is a prevalent birth anomaly, the etiology of which remains poorly understood. Here, we show that late-stage exposure of Xenopus embryos to atrazine, a widely used herbicide that targets electron transport chain (ETC) reactions, elicits intestinal malrotation at high frequency. Interestingly, atrazine specifically inhibits the cellular morphogenetic events required for gut tube elongation, including cell rearrangement, differentiation and proliferation; insufficient gut lengthening consequently reorients the direction of intestine rotation. Transcriptome analyses of atrazine-exposed intestines reveal misexpression of genes associated with glycolysis and oxidative stress, and metabolomics shows that atrazine depletes key glycolytic and tricarboxylic acid cycle metabolites. Moreover, cellular bioenergetics assays indicate that atrazine blocks a crucial developmental transition from glycolytic ATP production toward oxidative phosphorylation. Atrazine-induced defects are phenocopied by rotenone, a known ETC Complex I inhibitor, accompanied by elevated reactive oxygen species, and rescued by antioxidant supplementation, suggesting that malrotation may be at least partly attributable to redox imbalance. These studies reveal roles for metabolism in gut morphogenesis and implicate defective gut tube elongation and/or metabolic perturbations in the etiology of intestinal malrotation.

Adaptation of Glucose Metabolism to Limb Autotomy and Regeneration in the Chinese Mitten Crab

Limb autotomy and regeneration represent distinctive responses of crustaceans to environmental stress. Glucose metabolism plays a pivotal role in energy generation for tissue development and regeneration across various species. However, the relationship between glucose metabolism and tissue regeneration in crustaceans remains elusive. Therefore, this study is aimed at analyzing the alterations of glucose metabolic profile during limb autotomy and regeneration in Eriocheir sinensis, while also evaluating the effects of carbohydrate supplementation on limb regeneration. The results demonstrated that limb autotomy triggered a metabolic profile adaption at the early stage of regeneration. Hemolymph glucose levels were elevated, and multiple glucose catabolic pathways were enhanced in the hepatopancreas. Additionally, glucose and ATP levels in the regenerative limb were upregulated, along with increased expression of glucose transporters. Furthermore, the gene expression and activity of enzymes involved in gluconeogenesis were repressed in the hepatopancreas. These findings indicate that limb regeneration triggers metabolic profile adaptations to meet the elevated energy requirements. Moreover, the study observed that supplementation with corn starch enhanced limb regeneration capacity by promoting wound healing and blastema growth. Interestingly, dietary carbohydrate addition influenced limb regeneration by stimulating gluconeogenesis rather than glycolysis in the regenerative limb. Thus, these results underscore the adaptation of glucose metabolism during limb autotomy and regeneration, highlighting its essential role in the limb regeneration process of E. sinensis.

Molecular basis of retinal remodeling in a zebrafish model of retinitis pigmentosa

A hallmark of inherited retinal degenerative diseases such as retinitis pigmentosa (RP) is progressive structural and functional remodeling of the remaining retinal cells as photoreceptors degenerate. Extensive remodeling of the retina stands as a barrier for the successful implementation of strategies to restore vision. To understand the molecular basis of remodeling, we performed analyses of single-cell transcriptome data from adult zebrafish retina of wild type AB strain (WT) and a P23H mutant rhodopsin transgenic model of RP with continuous degeneration and regeneration. Retinas from both female and male fish were pooled to generate each library, combining data from both sexes. We provide a benchmark atlas of retinal cell type transcriptomes in zebrafish and insight into how each retinal cell type is affected in the P23H model. Oxidative stress is found throughout the retina, with increases in reliance on oxidative metabolism and glycolysis in the affected rods as well as cones, bipolar cells, and retinal ganglion cells. There is also transcriptional evidence for widespread synaptic remodeling and enhancement of glutamatergic transmission in the inner retina. Notably, changes in circadian rhythm regulation are detected in cones, bipolar cells, and retinal pigmented epithelium. We also identify the transcriptomic signatures of retinal progenitor cells and newly formed rods essential for the regenerative process. This comprehensive transcriptomic analysis provides a molecular road map to understand how the retina remodels in the context of chronic retinal degeneration with ongoing regeneration.

Enduring questions in regenerative biology and the search for answers

The potential for basic research to uncover the inner workings of regenerative processes and produce meaningful medical therapies has inspired scientists, clinicians, and patients for hundreds of years. Decades of studies using a handful of highly regenerative model organisms have significantly advanced our knowledge of key cell types and molecular pathways involved in regeneration. However, many questions remain about how regenerative processes unfold in regeneration-competent species, how they are curtailed in non-regenerative organisms, and how they might be induced (or restored) in humans. Recent technological advances in genomics, molecular biology, computer science, bioengineering, and stem cell research hold promise to collectively provide new experimental evidence for how different organisms accomplish the process of regeneration. In theory, this new evidence should inform the design of new clinical approaches for regenerative medicine. A deeper understanding of how tissues and organs regenerate will also undoubtedly impact many adjacent scientific fields. To best apply and adapt these new technologies in ways that break long-standing barriers and answer critical questions about regeneration, we must combine the deep knowledge of developmental and evolutionary biologists with the hard-earned expertise of scientists in mechanistic and technical fields. To this end, this perspective is based on conversations from a workshop we organized at the Banbury Center, during which a diverse cross-section of the regeneration research community and experts in various technologies discussed enduring questions in regenerative biology. Here, we share the questions this group identified as significant and unanswered, i.e., known unknowns. We also describe the obstacles limiting our progress in answering these questions and how expanding the number and diversity of organisms used in regeneration research is essential for deepening our understanding of regenerative capacity. Finally, we propose that investigating these problems collaboratively across a diverse network of researchers has the potential to advance our field and produce unexpected insights into important questions in related areas of biology and medicine.

Metabolic switches during development and regeneration

Metabolic switches are a crucial hallmark of cellular development and regeneration. In response to changes in their environment or physiological state, cells undergo coordinated metabolic switching that is necessary to execute biosynthetic demands of growth and repair. In this Review, we discuss how metabolic switches represent an evolutionarily conserved mechanism that orchestrates tissue development and regeneration, allowing cells to adapt rapidly to changing conditions during development and postnatally. We further explore the dynamic interplay between metabolism and how it is not only an output, but also a driver of cellular functions, such as cell proliferation and maturation. Finally, we underscore the epigenetic and cellular mechanisms by which metabolic switches mediate biosynthetic needs during development and regeneration, and how understanding these mechanisms is important for advancing our knowledge of tissue development and devising new strategies to promote tissue regeneration.

Fetal Reprogramming of Nutrient Surplus Signaling, O-GlcNAcylation, and the Evolution of CKD

ABSTRACT

Fetal kidney development is characterized by increased uptake of glucose, ATP production by glycolysis, and upregulation of mammalian target of rapamycin (mTOR) and hypoxia-inducible factor-1 alpha (HIF-1 α ), which (acting in concert) promote nephrogenesis in a hypoxic low-tubular-workload environment. By contrast, the healthy adult kidney is characterized by upregulation of sirtuin-1 and adenosine monophosphate-activated protein kinase, which enhances ATP production through fatty acid oxidation to fulfill the needs of a normoxic high-tubular-workload environment. During stress or injury, the kidney reverts to a fetal signaling program, which is adaptive in the short term, but is deleterious if sustained for prolonged periods when both oxygen tension and tubular workload are heightened. Prolonged increases in glucose uptake in glomerular and proximal tubular cells lead to enhanced flux through the hexosamine biosynthesis pathway; its end product-uridine diphosphate N -acetylglucosamine-drives the rapid and reversible O-GlcNAcylation of thousands of intracellular proteins, typically those that are not membrane-bound or secreted. Both O-GlcNAcylation and phosphorylation act at serine/threonine residues, but whereas phosphorylation is regulated by hundreds of specific kinases and phosphatases, O-GlcNAcylation is regulated only by O-GlcNAc transferase and O-GlcNAcase, which adds or removes N-acetylglucosamine, respectively, from target proteins. Diabetic and nondiabetic CKD is characterized by fetal reprogramming (with upregulation of mTOR and HIF-1 α ) and increased O-GlcNAcylation, both experimentally and clinically. Augmentation of O-GlcNAcylation in the adult kidney enhances oxidative stress, cell cycle entry, apoptosis, and activation of proinflammatory and profibrotic pathways, and it inhibits megalin-mediated albumin endocytosis in glomerular mesangial and proximal tubular cells-effects that can be aggravated and attenuated by augmentation and muting of O-GlcNAcylation, respectively. In addition, drugs with known nephroprotective effects-angiotensin receptor blockers, mineralocorticoid receptor antagonists, and sodium-glucose cotransporter 2 inhibitors-are accompanied by diminished O-GlcNAcylation in the kidney, although the role of such suppression in mediating their benefits has not been explored. The available evidence supports further work on the role of uridine diphosphate N -acetylglucosamine as a critical nutrient surplus sensor (acting in concert with upregulated mTOR and HIF-1 α signaling) in the development of diabetic and nondiabetic CKD.

An insight on the N-glycome of notochordal cell-rich porcine nucleus pulposus during maturation

Degeneration of the intervertebral disc is an age-related condition. It also accompanies the disappearance of the notochordal cells, which are remnants of the developmental stages of the nucleus pulposus (NP). Molecular changes such as extracellular matrix catabolism, cellular phenotype, and glycosaminoglycan loss in the NP have been extensively studied. However, as one of the most significant co- and posttranslational modifications, glycosylation has been overlooked in cells in degeneration. Here, we aim to characterize the N-glycome of young and mature NP and identify patterns related to aging. Accordingly, we isolated N-glycans from notochordal cell-rich NP from porcine discs, characterized them using a combined approach of exoglycosidase digestions and analysis with hydrophilic interaction ultra-performance liquid chromatography and mass spectrometry. We have assigned over 300 individual N-glycans for each age group. Moreover, we observed a notable abundance of antennary structures, galactosylation, fucosylation, and sialylation in both age groups. In addition, as indicated from our results, increasing outer arm fucosylation and decreasing α(2,3)-linked sialylation with aging suggest that these traits are age-dependent. Lastly, we have focused on an extensive characterization of the N-glycome of the notochordal cell-rich NP in aging without inferred degeneration, describing glycosylation changes specific for aging only. Our findings in combination with those of other studies, suggest that the degeneration of the NP does not involve identical processes as aging.

Identification of overlapping and distinct mural cell populations during early embryonic development

Mural cells are an essential perivascular cell population that associate with blood vessels and contribute to vascular stabilization and tone. In the embryonic zebrafish vasculature, pdgfrb and tagln are commonly used as markers for identifying pericytes and vascular smooth muscle cells (vSMCs). However, the expression patterns of these markers used in tandem have not been fully described. Here, we used the Tg(pdgfrb:Gal4FF; UAS:RFP) and Tg(tagln:NLS-EGFP) transgenic lines to identify single- and double-positive perivascular populations in the cranial, axial, and intersegmental vessels between 1 and 5 days post-fertilization. From this comparative analysis, we discovered two novel regions of tagln-positive cell populations that have the potential to function as mural cell precursors. Specifically, we found that the hypochord- a reportedly transient structure-contributes to tagln-positive cells along the dorsal aorta. We also identified a unique sclerotome-derived mural cell progenitor population that resides along the midline between the neural tube and notochord and contributes to intersegmental vessel mural cell coverage. Together, our findings highlight the variability and versatility of tracking pdgfrb and tagln expression in mural cells of the developing zebrafish embryo.

Duox is the primary NADPH oxidase responsible for ROS production during adult caudal fin regeneration in zebrafish

Sustained elevated levels of reactive oxygen species (ROS) have been shown to be essential for regeneration in many organisms. This has been shown primarily via the use of pharmacological inhibitors targeting the family of NADPH oxidases (NOXes). To identify the specific NOXes involved in ROS production during adult caudal fin regeneration in zebrafish, we generated nox mutants for duox, nox5 and cyba (a key subunit of NOXes 1-4) and crossed these lines with a transgenic line ubiquitously expressing HyPer, which permits the measurement of ROS levels. Homozygous duox mutants had the greatest effect on ROS levels and rate of fin regeneration among the single mutants. However, duox:cyba double mutants showed a greater effect on fin regeneration than the single duox mutants, suggesting that Nox1-4 also play a role during regeneration. This work also serendipitously found that ROS levels in amputated adult zebrafish fins oscillate with a circadian rhythm.

Highly efficient and rapid generation of human pluripotent stem cells by chemical reprogramming

We recently demonstrated the chemical reprogramming of human somatic cells to pluripotent stem cells (hCiPSCs), which provides a robust approach for cell fate manipulation. However, the utility of this chemical approach is currently hampered by slow kinetics. Here, by screening for small molecule boosters and systematically optimizing the original condition, we have established a robust, chemically defined reprogramming protocol, which greatly shortens the induction time from ∼50 days to a minimum of 16 days and enables highly reproducible and efficient generation of hCiPSCs from all 17 tested donors. We found that this optimized protocol enabled a more direct reprogramming process by promoting cell proliferation and oxidative phosphorylation metabolic activities at the early stage. Our results highlight a distinct chemical reprogramming pathway that leads to a shortcut for the generation of human pluripotent stem cells, which represents a powerful strategy for human cell fate manipulation.

Parallel repair mechanisms in plants and animals

All organisms have acquired mechanisms for repairing themselves after accidents or lucky escape from predators, but how analogous are these mechanisms across phyla? Plants and animals are distant relatives in the tree of life, but both need to be able to efficiently repair themselves, or they will perish. Both have an outer epidermal barrier layer and a circulatory system that they must protect from infection. However, plant cells are immotile with rigid cell walls, so they cannot raise an animal-like immune response or move away from the insult, as animals can. Here, we discuss the parallel strategies and signalling pathways used by plants and animals to heal their tissues, as well as key differences. A more comprehensive understanding of these parallels and differences could highlight potential avenues to enhance healing of patients' wounds in the clinic and, in a reciprocal way, for developing novel alternatives to agricultural pesticides.

Recent development of analytical methods for disease-specific protein O-GlcNAcylation

The enzymatic modification of protein serine or threonine residues by N-acetylglucosamine, namely O-GlcNAcylation, is a ubiquitous post-translational modification that frequently occurs in the nucleus and cytoplasm. O-GlcNAcylation is dynamically regulated by two enzymes, O-GlcNAc transferase and O-GlcNAcase, and regulates nearly all cellular processes in epigenetics, transcription, translation, cell division, metabolism, signal transduction and stress. Aberrant O-GlcNAcylation has been shown in a variety of diseases, including diabetes, neurodegenerative diseases and cancers. Deciphering O-GlcNAcylation remains a challenge due to its low abundance, low stoichiometry and extreme lability in most tandem mass spectrometry. Separation or enrichment of O-GlcNAc proteins or peptides from complex mixtures has been of great interest because quantitative analysis of protein O-GlcNAcylation can elucidate their functions and regulatory mechanisms in disease. However, valid and specific analytical methods are still lacking, and efforts are needed to further advance this direction. Here, we provide an overview of recent advances in various analytical methods, focusing on chemical oxidation, affinity of antibodies and lectins, hydrophilic interaction, and enzymatic addition of monosaccharides in conjugation with these methods. O-GlcNAcylation quantification has been described in detail using mass-spectrometric or non-mass-spectrometric techniques. We briefly summarized dysregulated changes in O-GlcNAcylation in disease.

Elevated pentose phosphate pathway flux supports appendage regeneration

A fundamental step in regeneration is rapid growth to replace lost tissue. Cells must generate sufficient lipids, nucleotides, and proteins to fuel rapid cell division. To define metabolic pathways underlying regenerative growth, we undertake a multimodal investigation of metabolic reprogramming in Xenopus tropicalis appendage regeneration. Regenerating tissues have increased glucose uptake; however, inhibition of glycolysis does not decrease regeneration. Instead, glucose is funneled to the pentose phosphate pathway (PPP), which is essential for full tail regeneration. Liquid chromatography-mass spectrometry (LC-MS) metabolite profiling reveals increased nucleotide and nicotinamide intermediates required for cell division. Using single-cell RNA sequencing (scRNA-seq), we find that highly proliferative cells have increased transcription of PPP enzymes and not glycolytic enzymes. Further, PPP inhibition results in decreased cell division specifically in regenerating tissue. Our results inform a model wherein regenerating tissues direct glucose toward the PPP, yielding nucleotide precursors to drive regenerative cell proliferation.

A regeneration-triggered metabolic adaptation is necessary for cell identity transitions and cell cycle re-entry to support blastema formation and bone regeneration

Regeneration depends on the ability of mature cells at the injury site to respond to injury, generating tissue-specific progenitors that incorporate the blastema and proliferate to reconstitute the original organ architecture. The metabolic microenvironment has been tightly connected to cell function and identity during development and tumorigenesis. Yet, the link between metabolism and cell identity at the mechanistic level in a regenerative context remains unclear. The adult zebrafish caudal fin, and bone cells specifically, have been crucial for the understanding of mature cell contribution to tissue regeneration. Here, we use this model to explore the relevance of glucose metabolism for the cell fate transitions preceding new osteoblast formation and blastema assembly. We show that injury triggers a modulation in the metabolic profile at early stages of regeneration to enhance glycolysis at the expense of mitochondrial oxidation. This metabolic adaptation mediates transcriptional changes that make mature osteoblast amenable to be reprogramed into pre-osteoblasts and induces cell cycle re-entry and progression. Manipulation of the metabolic profile led to severe reduction of the pre-osteoblast pool, diminishing their capacity to generate new osteoblasts, and to a complete abrogation of blastema formation. Overall, our data indicate that metabolic alterations have a powerful instructive role in regulating genetic programs that dictate fate decisions and stimulate proliferation, thereby providing a deeper understanding on the mechanisms regulating blastema formation and bone regeneration.

Intestine-enriched apolipoprotein b orthologs are required for stem cell progeny differentiation and regeneration in planarians

Lipid metabolism plays an instructive role in regulating stem cell state and differentiation. However, the roles of lipid mobilization and utilization in stem cell-driven regeneration are unclear. Planarian flatworms readily restore missing tissue due to injury-induced activation of pluripotent somatic stem cells called neoblasts. Here, we identify two intestine-enriched orthologs of apolipoprotein b, apob-1 and apob-2, which mediate transport of neutral lipid stores from the intestine to target tissues including neoblasts, and are required for tissue homeostasis and regeneration. Inhibition of apob function by RNAi causes head regression and lysis in uninjured animals, and delays body axis re-establishment and regeneration of multiple organs in amputated fragments. Furthermore, apob RNAi causes expansion of the population of differentiating neoblast progeny and dysregulates expression of genes enriched in differentiating and mature cells in eight major cell type lineages. We conclude that intestine-derived lipids serve as a source of metabolites required for neoblast progeny differentiation.

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. Less well understood are organismic physiological parameters and signaling circuits essential to maintain effective tissue repair. Here, we review accumulated evidence that positions the interplay of local and systemic changes in metabolism as essential variables modulating the injury response. We particularly emphasize the role of lipids and lipid-like molecules as significant components long overlooked. This article is protected by copyright. All rights reserved.

Beyond Genetics: The Role of Metabolism in Photoreceptor Survival, Development and Repair

Vision commences in the retina with rod and cone photoreceptors that detect and convert light to electrical signals. The irreversible loss of photoreceptors due to neurodegenerative disease leads to visual impairment and blindness. Interventions now in development include transplanting photoreceptors, committed photoreceptor precursors, or retinal pigment epithelial (RPE) cells, with the latter protecting photoreceptors from dying. However, introducing exogenous human cells in a clinical setting faces both regulatory and supply chain hurdles. Recent work has shown that abnormalities in central cell metabolism pathways are an underlying feature of most neurodegenerative disorders, including those in the retina. Reversal of key metabolic alterations to drive retinal repair thus represents a novel strategy to treat vision loss based on cell regeneration. Here, we review the connection between photoreceptor degeneration and alterations in cell metabolism, along with new insights into how metabolic reprogramming drives both retinal development and repair following damage. The potential impact of metabolic reprogramming on retinal regeneration is also discussed, specifically in the context of how metabolic switches drive both retinal development and the activation of retinal glial cells known as Müller glia. Müller glia display latent regenerative properties in teleost fish, however, their capacity to regenerate new photoreceptors has been lost in mammals. Thus, re-activating the regenerative properties of Müller glia in mammals represents an exciting new area that integrates research into developmental cues, central metabolism, disease mechanisms, and glial cell biology. In addition, we discuss this work in relation to the latest insights gleaned from other tissues (brain, muscle) and regenerative species (zebrafish).

Lactate metabolism coordinates macrophage response and regeneration in zebrafish

Rationale: Macrophages are multifunctional cells with a pivotal role on tissue development, homeostasis and regeneration. Indeed, in response to tissue injury and the ensuing regeneration process, macrophages are challenged and undergo massive metabolic adaptations and changes. However, the control of this metabolic reprogramming by macrophage microenvironment has never been deciphered in vivo. Methods: In this study, we used zebrafish model and caudal fin resection as a robust regeneration system. We explored specific changes in gene expression after tissue amputation via single-cell RNA sequencing analysis and whole-tissue transcriptomic analysis. Based on the identification of key modifications, we confirmed the role of the lactate pathway in macrophage response and fin regeneration, through the combination of chemical and genetic inhibitors of this pathway. Results: Single cell RNA sequencing revealed the upregulation of different genes associated with glycolysis and lactate metabolism in macrophages, upon fin regeneration. Hence, using chemical inhibitors of the LDH enzyme, we confirmed the role of lactate in macrophage recruitment and polarization, to promote a pro-inflammatory phenotype and enhance fin regeneration. The genetic modulation of monocarboxylate transporters illustrated a complex regulation of lactate levels, based on both intracellular and extracellular supplies. Commonly, the different sources of lactate resulted in macrophage activation with an increased expression level of inflammatory cytokines such as TNFa during the first 24 hours of regeneration. Transcriptomic analyses confirmed that lactate induced a global modification of gene expression in macrophages. Conclusion: Altogether, our findings highlight the crucial role of lactate at the onset of macrophage differentiation toward a pro-inflammatory phenotype. The deep modifications of macrophage phenotype mediated by lactate and downstream effectors play a key role to coordinate inflammatory response and tissue regeneration.

In vivo fluorescence lifetime imaging of macrophage intracellular metabolism during wound responses in zebrafish

The function of macrophages in vitro is linked to their metabolic rewiring. However, macrophage metabolism remains poorly characterized in situ. Here, we used two-photon intensity and lifetime imaging of autofluorescent metabolic coenzymes, nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and flavin adenine dinucleotide (FAD), to assess the metabolism of macrophages in the wound microenvironment. Inhibiting glycolysis reduced NAD(P)H mean lifetime and made the intracellular redox state of macrophages more oxidized, as indicated by reduced optical redox ratio. We found that TNFα+ macrophages had lower NAD(P)H mean lifetime and were more oxidized compared to TNFα- macrophages. Both infection and thermal injury induced a macrophage population with a more oxidized redox state in wounded tissues. Kinetic analysis detected temporal changes in the optical redox ratio during tissue repair, revealing a shift toward a more reduced redox state over time. Metformin reduced TNFα+ wound macrophages, made intracellular redox state more reduced and improved tissue repair. By contrast, depletion of STAT6 increased TNFα+ wound macrophages, made redox state more oxidized and impaired regeneration. Our findings suggest that autofluorescence of NAD(P)H and FAD is sensitive to dynamic changes in intracellular metabolism in tissues and can be used to probe the temporal and spatial regulation of macrophage metabolism during tissue damage and repair.

Aerobic glycolysis is important for zebrafish larval wound closure and tail regeneration

The underlying mechanisms of appendage regeneration remain largely unknown and uncovering these mechanisms in capable organisms has far-reaching implications for potential treatments in humans. Recent studies implicate a requirement for metabolic reprogramming reminiscent of the Warburg effect during successful appendage and organ regeneration. As changes are thus predicted to be highly dynamic, methods permitting direct, real-time visualisation of metabolites at the tissue and organismal level would offer a significant advance in defining the influence of metabolism on regeneration and healing. We sought to examine whether glycolytic activity was altered during larval fin regeneration, utilising the genetically encoded biosensor, Laconic, enabling the spatiotemporal assessment of lactate levels in living zebrafish. We present evidence for a rapid increase in lactate levels within min following injury, with a role of aerobic glycolysis in actomyosin contraction and wound closure. We also find a second wave of lactate production, associated with overall larval tail regeneration. Chemical inhibition of glycolysis attenuates both the contraction of the wound and regrowth of tissue following tail amputation, suggesting aerobic glycolysis is necessary at two distinct stages of regeneration.

Enhanced Platelet-Rich Plasma (ePRP) Stimulates Wound Healing through Effects on Metabolic Reprogramming in Fibroblasts

As a source of growth factors for expediting wound healing and tissue regeneration, plasma-rich plasma (PRP) has been extensively applied in diverse fields including orthopaedics, ophthalmology, oral and maxillofacial surgery, dentistry, and gynaecology. However, the function of PRP in metabolic regulations remains enigmatic. A standardized method was devised herein to enrich growth factors and to lyophilize it as enhanced PRP (ePRP) powder, which could become ubiquitously available without mechanical centrifugation in clinical practice. To identify metabolic reprogramming in human dermal fibroblasts under ePRP treatment, putative metabolic targets were identified by transcriptome profiling and validated for their metabolic effects and mechanism. ePRP does not only promote wound healing but re-aligns energy metabolism by shifting to glycolysis through stimulation of glycolytic enzyme activity in fibroblasts. On the contrary, oxygen consumption rates and several mitochondrial respiration activities were attenuated in ePRP-treated fibroblasts. Furthermore, ePRP treatment drives the mitochondrial resetting by hindering the mitochondrial biogenesis-related genes and results in a dampened mitochondrial mass. Antioxidant production was further increased by ePRP treatment to prevent reactive oxygen species formation. Besides, ePRP also halts the senescence progression of fibroblasts by activating SIRT1 expression. Importantly, the glycolytic inhibitor 2-DG can completely reverse the ePRP-enhanced wound healing capacity, whereas the mitochondrial inhibitor oligomycin cannot. This is the first study to utilize PRP for comprehensively investigating its effects on the metabolic reprogramming of fibroblasts. These findings indicate that PRP’s primary metabolic regulation is to promote metabolic reprogramming toward glycolytic energy metabolism in fibroblasts, preserving redox equilibrium and allowing anabolic pathways necessary for the healing and anti-ageing process.