Stages Of Regeneration Research Articles

Macrophages in the Context of Muscle Regeneration and Duchenne Muscular Dystrophy.

Macrophages are essential to muscle regeneration, as they regulate inflammation, carry out phagocytosis, and facilitate tissue repair. These cells exhibit phenotypic switching from pro-inflammatory (M1) to anti-inflammatory (M2) states during muscle repair, influencing myoblast proliferation, differentiation, and myofiber formation. In Duchenne Muscular Dystrophy (DMD), asynchronous muscle injuries disrupt the normal temporal stages of regeneration, leading to fibrosis and failed regeneration. Altered macrophage activity is associated with DMD progression and physiopathology. Gaining insight into the intricate relationship between macrophages and muscle cells is crucial for creating effective therapies aimed at treating this muscle disorder. This review explores the dynamic functions of macrophages in muscle regeneration and their implications in DMD.

Effects of different loads of Pinus pinaster Ait. litter and ash on the germination and growth of Cistus ladanifer L

Key messageCistus ladanifer L. shows an extraordinary plasticity of germination and growth. Fire promotes the regeneration of C. ladanifer by triggering its germination through thermal shock as well as by enhancing its seedling growth through the addition of ashes. On the contrary, stacking of Pinus pinaster Ait. leaf litter may hinder seedling establishment, at least in the first months after germination.ContextPinus pinaster Ait. is affected by forest fires in the Mediterranean basin. Its extreme flammability is due to the high spatial continuity together with the massive accumulation of leaf litter. Cistus ladanifer L. is a species which is widely distributed in the west Mediterranean region where it can form vast shrublands and flourish under these pinewoods. Although high temperatures associated with the occurrence of fire trigger germination of C. ladanifer, knowledge on how other factors, such as the presence of litter on the forest floor or the ash left after the fire, influence germination and seedling growth is essential to improve land management plans.AimsThe main objective of this study was to determine the effects of different loads of litter from P. pinaster and ash from their combustion on the germination and growth of seedlings of C. ladanifer.MethodsTwo experiments were carried out to assess the effect of heat shock (100 °C for 10 min) and two loads of litter and ash from P. pinaster (control, high and low loads of litter, high and low loads of ash) on the germination and growth after 2 and 4 months of C. ladanifer.ResultsHeat shock significantly increased the germination of C. ladanifer. In contrast, the addition of litter and ash had no effect on total germination but affected the growth of the seedlings coming from seeds exposed to heat shock. Litter treatments reduced biomass of 2 months seedlings and ash increased biomass of 4 months seedlings.ConclusionC. ladanifer is a species favoured by fire in different ways depending on the stage of regeneration. Germination is promoted by heat shock while seedling growth is favoured by ash nutrients. In contrast, pine leaf litter hinders seedling growth, although this effect disappears 4 months after germination. Alternative forest management practices to prescribed fires are recommended if preventing the spread of Cistus is a priority.

Assessment and Monitoring of the Wound Micro-Environment in Chronic Wounds Using Standardized Wound Swabbing for Individualized Diagnostics and Targeted Interventions.

Background/Objectives: Patient-specific diagnostic and therapeutic approaches are important in the care of people with chronic wounds. The heterogeneity of underlying disease profiles and the diversity of the wound micro-environment make generalized approaches difficult. While high-throughput molecular diagnostic methods are increasingly widespread and available, the analysis of objective biomolecular disease patterns has not found its way into everyday wound management. The aim of this study is to evaluate the use of wound swab samples for the analysis of biomarkers and disease patterns in people with chronic wounds. Methods: A sample cohort from the multicenter "Wound-BIOME" project was analyzed. The project aims to comprehensively investigate the local micro-environment of chronic wounds of various entities, healing tendencies and regeneration stages at the biomolecular level. A sample collection and handling protocol suitable for everyday use was tested and evaluated regarding feasibility for multiplex immunoassay, proteomics, small RNA sequencing (miRNA) and metagenome analyses (microbiomics). Results: It could be shown that standard wound swabs are well-suited for the analysis of the complex wound micro-environment using various high-throughput methods. Despite the sample heterogeneity, the quality was adequate to analyze biomolecular patterns. Conclusions: Initial analyses of protein signatures, microbial wound communities and miRNA patterns show promising results for future individualized diagnostics and targeted interventions.

Thermal Efficiency Analysis of a 1 kW ORC System with a Solar Collection Stage and R-245fa Working Fluid: A Case Study

A thermal efficiency analysis of an organic Rankine cycle (ORC) system enables its performance to be evaluated; for this purpose, critical system components, including the turbine and the boiler, must be scrutinized. ORC plants can operate under various regimes, such as simple, regeneration, and reheat work modes. Organic fluids such as R-245fa integrate low-temperature sources such as solar radiation. However, a literature review revealed limited research on the impact of a solar collection system on the overall thermal efficiency of an ORC system during the regeneration stage. In this study, we examined the thermal efficiency behavior of an ORC plant with a 1 kW generator operating in simple and regeneration modes with a solar collection stage. The results show that the thermal efficiency in simple mode was 35.27%, while in regeneration mode with solar collection it reached 51.30%. Improving the thermal efficiency of a thermodynamic cycle system can reduce CO2 emissions. The operating temperature ranges facilitate the development of a methodology for industries to implement ORC systems in their manufacturing processes, thereby utilizing waste heat from industrial operations.

The catalytic decomposition of CH4 using Ce-doped Fe/CaO-Ca12Al14O33 catalyst and its regeneration performance for H2 production

The catalytic decomposition of CH4 using low cost and non-toxicity Fe-based catalysts is a prospective method for H2 production. The regeneration process of iron-based catalysts involves CO2 emission and incomplete conversion of carbon deposition. In this work, a novel catalytic decomposition of CH4/regeneration process was proposed using the Ce-doped Fe/CaO-Ca12Al14O33 catalyst for H2 production. To remove the carbon deposition in the catalyst, the regeneration stage includes four steps: solid carbon production by vibratory separation, steam gasification of residual carbon deposition to produce H2 where CO2 is captured by CaO to form CaCO3, calcination of CaCO3 to produce CaO and pure CO2, methanol production by CO2 and H2 from carbon deposition gasification. The effects of Ce doping on the catalysis/regeneration performance of Fe/CaO-Ca12Al14O33 catalysts were studied, and the Ce-doped Fe/CaO-Ca12Al14O33 catalyst was compared with Cu-, Zn-, and Mn- doped Fe/CaO-Ca12Al14O33 catalysts. The solid carbon obtained from the catalytic decomposition of CH4/regeneration cycles was characterized. The Ce-doped Fe/CaO-Ca12Al14O33 catalyst shows excellent catalysis, CO2 capture, and stability performance in the catalytic decomposition of CH4/regeneration cycles. The average CH4 conversion is 90.02% in the first cycle, which decreases to 80.01% after 8 cycles. Carbon nanotubes are the main forms of obtained solid carbon with the favorable pore structure. The doping of Ce improves the effective adsorption sites for CH4 and CO2. Carbon deposition in the catalyst is efficiently removed by steam gasification. In addition, CeO2 promotes the electron transfer, oxygen vacancy generation, and Fe3C decomposition, which leads to superior catalytic performance and resistance to deactivation of the catalyst. The CeO2-doped Fe/CaO-Ca12Al14O33 catalyst is promising for H2 production via catalysis/regeneration cycles.

Putative epithelial-mesenchymal transitions during salamander limb regeneration: Current perspectives and future investigations.

Previous studies have implicated epithelial-mesenchymal transition (EMT) in salamander limb regeneration. In this review, we describe putative roles for EMT during each stage of limb regeneration in axolotls and other salamanders. We hypothesize that EMT and EMT-like gene expression programs may regulate three main cellular processes during limb regeneration: (1) keratinocyte migration during wound closure; (2) transient invasion of the stump by epithelial cells undergoing EMT; and (3) use of EMT-like programs by non-epithelial blastemal progenitor cells to escape the confines of their niches. Finally, we propose nontraditional roles for EMT during limb regeneration that warrant further investigation, including alternative EMT regulators, stem cell activation, and fibrosis induced by aberrant EMT.

Endogenous phytohormone analysis during sequential stages of somatic embryogenesis in Musa AAA cv. Grand Naine (subgroup Cavendish)

Abstract This is the first initiative study to provide quantified levels of four endogenous phytohormones during the induction, regeneration, maturation and germination stages of somatic embryogenesis (SE) in banana, using immature male bud explants, in the popular commercial triploid cultivar Grand Naine (AAA). Phytohormones are known to play a major role in the regulation of SE and most protocols have been developed for various cultivars of banana following empirical approaches. Although, several reports are available with regard to the impact of growth regulators exogenously supplemented to the media, the vital role of endogenous growth hormones in various developmental stages of SE remain unclear in banana. Reverse Phase High Performance Liquid Chromatography (RP-HPLC) was used to analyze endogenous status of indole acetic acid (IAA), zeatin, gibberellic acid (GA) and abscisic acid (ABA). Results from this study revealed that endogenous IAA and GA along with exogenous auxin play a major role in the induction of embryogenic competence of male bud explants. The levels of endogenous IAA and zeatin were found to be higher in embryogenic calli than non-embryogenic calli, although three different types of exogenous auxins were supplemented in callogenesis medium, but not cytokinin. Higher level of ABA and GA was observed in early and late developmental stages of somatic embryo, respectively. GA also played a predominant role in germination of somatic embryos. These findings will be applied for improvement of SE protocol in recalcitrant banana cultivars by suitably altering or supplementing exogenous growth hormones.

Evidence for platelet-derived transforming growth factor β1 as an early inducer of liver regeneration after hepatectomy in mice.

Platelets play a crucial role in tissue regeneration, and their involvement in liver regeneration is well-established. However, the specific contribution of platelet-derived Transforming Growth Factor Beta 1 (TGFβ1) to liver regeneration remains unexplored. This study investigated the role of platelet-derived TGFβ1 in initiating liver regeneration following 2/3 liver resection. Using platelet-specific TGFβ1 knockout (Plt.TGFβ1 KO) mice and wild-type littermates (Plt.TGFβ1 WT) as controls, the study assessed circulating levels and hepatic gene expression of TGFβ1, Platelet Factor 4 (PF4), and Thrombopoietin (TPO) at early time points post-hepatectomy (post-PHx). Hepatocyte proliferation was quantified through Ki67 staining and PCNA expression in total liver lysates at various intervals, and phosphohistone-H3 (PHH3) staining was employed to mark mitotic cells. Circulating levels of hepatic mitogens, Hepatocyte Growth Factor (HGF), and Interleukin-6 (IL6) were also assessed. Results revealed that platelet-TGFβ1 deficiency significantly reduced total plasma TGFβ1 levels at 5 h post-PHx in Plt.TGFβ1 KO mice compared to controls. While circulating PF4 levels, liver platelet recruitment and activation appeared normal at early time points, Plt.TGFβ1 KO mice showed more stable circulating platelet numbers with higher numbers at 48 h post-PHx. Notably, hepatocyte proliferation was significantly reduced in Plt.TGFβ1 KO mice. The results show that a lack of TGFβ1 in platelets leads to an unbalanced expression of IL6 in the liver and to strongly increased HGF levels 48 h after liver resection, and yet liver regeneration remains reduced. The study identifies platelet-TGFβ1 as a regulator of hepatocyte proliferation and platelet homeostasis in the early stages of liver regeneration.

The balance between helper T 17 and regulatory T cells in osteoimmunology and relevant research progress on bone tissue engineering.

Bone regeneration is a well-regulated dynamic process, of which the prominent role of the immune system on bone homeostasis is more and more revealed by recent research. Before fully activation of the bone remodeling cells, the immune system needs to clean up the microenvironment in facilitating the bone repair initiation. Furthermore, this microenvironment must be maintained properly by various mechanisms over the entire bone regeneration process. This review aims to summarize the role of the T-helper 17/Regulatory T cell (Th17/Treg) balance in bone cell remodeling and discuss the relevant progress in bone tissue engineering. The role of the immune response in the early stages of bone regeneration is crucial, especially the impact of the Th17/Treg balance on osteoclasts, mesenchymal stem cells (MSCs), and osteoblasts activity. By virtue of these knowledge advancements, innovative approaches in bone tissue engineering, such as nano-structures, hydrogel, and exosomes, are designed to influence the Th17/Treg balance and thereby augment bone repair and regeneration. Targeting the Th17/Treg balance is a promising innovative strategy for developing new treatments to enhance bone regeneration, thus offering potential breakthroughs in bone injury clinics.

Tree density by development stage in the “El Carrizal” wathershed of Tapalpa, Jalisco

The Tapalpa forest presents an abundance of pine trees in the juvenile stage ofregeneration and sapling, but this amount progressively decreases in thesuccessive stages, when the trees show larger dimensions and take up more spaceto grow. However, it was unknown how much the loss was and how much itreached the maximum size. The objective was to quantify the grove, the individualspace, the separation between trees and their decrease. The stages were classifiedaccording to the normal diameter and the sites were classified as excessive,recommendable, sufficient and poor density. Frequency distribution, loss, spacing,and distance between trees were calculated using the Hart-Becking formula.During the development cycle, the loss was close to 90 % with a rate of 0.2 to 3%, presenting a cumulative of 60 % in the monte bravo and vardazcal stages. Therecommended class began with 1 300 to 2 700 trees ha⁻¹ in the juvenile phase,with their respective spacing of 2.07 to 2.98 m, while the mature stage culminatedwith 150 trees ha⁻¹ separated at 8.77 m. The distance between trees is consideredan auxiliary tool in thinning operations.

Xenogenous implanted dental follicle stem cells promote periodontal regeneration through inducing the N2 phenotype of neutrophils

BackgroundPeriodontal tissue loss is the main reason for tooth mobility and loss caused by periodontal disease. Dental follicle stem cells (DFSCs) have significant therapeutic potential in periodontal regeneration, which maybe mainly depends on their potent immunomodulatory capacity. Consequently, this study aims to elucidate the impact of implanted xenogenous DFSCs on innate immune responses during early and late stages in the periodontal defect repair period.MethodsTo trace and investigate the immunomodulation mechanisms of DFSCs in vivo, DFSCs were engineered (E-DFSCs) using lentiviral vectors expressing CD63-enhanced green fluorescent protein (CD63-EGFP) and β-Actin-mCherry protein (ACTB-mCherry) to exhibit green and red fluorescence. The biological characteristics and functions of E-DFSCs were verified by proliferation, differentiation, and co-culture experiments in vitro. In vivo, the periodontal regeneration capacity of E-DFSCs was detected by implantation of murine periodontal defect model, and the response of innate immune cells was detected at the 1st, 3rd, and 5th days (early stage) and 4th week (late stage) after implantation.ResultsIn vitro assessments showed that E-DFSCs retain similar properties to their non-engineered counterparts but exhibit enhanced macrophage immunomodulation capability. In mice models, four-week micro-CT and histological evaluations indicated that E-DFSCs have equivalent efficiency to DFSCs in periodontal defect regeneration. At the early stage of repair in mice periodontal defect, fluorescence tracking showed that implanted E-DFSCs might primarily activate endogenous cells through direct contact and indirect actions, and most of these cells are myeloperoxidase-positive neutrophils. Additionally, compared with the control group, the neutrophilic infiltration and conversion of N2-type were significantly increased in the E-DFSC group. At the late stage of defect regeneration, more M2-type macrophages, fewer TRAP + osteoclasts, and an upregulated OPG/RANKL ratio were detected in the E-DFSC group compared to the control group, which indicated that immune balance tilts towards healing and bone formation.ConclusionThe xenogenous implanted DFSCs can induce the N2 phenotype of neutrophils in the early stage, which can activate the innate immune mechanism of the host to promote periodontal tissue regeneration.

The mRNA and microRNA Landscape of the Blastema Niche in Regenerating Newt Limbs.

Newts are excellent vertebrate models for investigating tissue regeneration due to their remarkable regenerative capabilities. To investigate the mRNA and microRNAs (miRNAs) profiles within the blastema niche of regenerating newt limbs, we amputated the limbs of Chinese fire belly newts (Cynops orientalis) and conducted comprehensive analyses of the transcriptome and microRNA profiles at five distinct time points post-amputation (0 hours, 1 day, 5 days 10 days and 20 days). We identified 24 significantly differentially expressed (DE) genes and 20 significantly DE miRNAs. Utilizing weighted gene co-expression network analysis (WGCNA) and gene ontology (GO) enrichment analysis, we identified four genes likely to playing crucial roles in the early stages of limb regeneration: Cemip, Rhou, Gpd2 and Pcna. Moreover, mRNA-miRNA integration analysis uncovered seven human miRNAs (miR-19b-1, miR-19b-2, miR-21-5p, miR-127-5p, miR-150-5p, miR-194-5p, and miR-210-5p) may regulate the expression of these four key genes. The temporal expression patterns of these key genes and miRNAs further validated the robustness of the identified mRNA-miRNA landscape. Our study successfully identified candidate key genes and elucidated a portion of the genetic regulatory mechanisms involved in newt limb regeneration. These findings offer valuable insights for further exploration of the intricate processes of tissue regeneration.

Cyclic biomachining of copper: Maximum metal removal rate with minimum depleted solution

Bacterially assisted leaching has been proposed for many innovative applications, such as urban mining or micromachining, but many technical challenges including substrate toxicity and downstream processing of the leach liquor must be solved before its industrial implementation. This study was conducted with the final goal of improving the average specific metal removal rate (SMRR) and reducing the amount of depleted solution generated in the leaching process of copper workpieces, with special attention paid to the detection of microbial activity inhibition.The copper leaching rate is almost entirely dependent upon the Fe3+ concentration with Fe3+/Fe2+ ratios higher than 0.3, after which A. ferrooxidans oxidation action becomes relevant. In both biotic and abiotic experiments, the SMRR peaked after the first hour of treatment, and it decreased sharply after three hours. A consecutive process alternating bioleaching and oxidant regeneration stages was proposed to improve performance, which considerably reduced both the time needed to dissolve a certain amount of metal and waste generation. The decrease in copper removal (25 %) and the increase in the time required for oxidant regeneration after five leaching cycles (longer than 90 h) were attributed to bacterial inhibition in the presence of 10.7 g Cu2+ L−1, which was established as the limiting metal concentration for reusing the biologically active solution.

Identification of astrocyte-like cells in an adult ascidian during regeneration of the central nervous system.

The mechanisms underlying regeneration of the central nervous system (CNS) following lesions have been studied extensively in both vertebrate and invertebrate models. To shed light on regeneration, ascidians, a sister group of vertebrates and with remarkable ability to regenerate their brains, constitute an appropriate model system. Glial cells have been implicated in regeneration in vertebrates; however, their role in the adult ascidian CNS regeneration is unknown. A model of degeneration and regeneration using the neurotoxin 3-acetylpyridine (3AP) in the brain of the ascidian Styela plicata was used to identify astrocyte-like cells and investigate their role. We studied the CNS of control ascidians (injected with artificial sea water) and of ascidians whose CNS was regenerating (1 and 10 days after the injection with 3AP). Our results show that the mRNA of the ortholog of glutamine synthetase (GS), a glial-cell marker in vertebrates, is increased during the early stages of regeneration. Confirming the identity of GS, the protein was identified via immunostaining in a cell population during the same regeneration stage. Last, a single ortholog of GS (GSII) is present in ascidian and amphioxus genomes, while two types exist in fungi, some invertebrates, and vertebrates, suggesting that ascidians have lost the GSI type. Taken together, our findings revealed that a cell population expressing glial-cell markers may play a role in regeneration in adult ascidians. This is the first report of astrocyte-like cells in the adult ascidian CNS, and contributes to understanding of the evolution of glial cells among metazoans.

Flexible strategies for carbon‐negative syngas and biochar poly‐generation via a novel chemical looping approach

AbstractThis work proposed a pyrolysis chemical looping reforming‐two stage regeneration (PCLR‐TR) process with carbon‐negative syngas and biochar poly‐generation，aimed at overcoming challenges in chemical looping gasification. The process effectively separates pyrolysis and reforming, circumventing slow solid–solid reactions and enabling the flexible adjustment of the H2/CO ratio. The two‐stage regeneration ensures improved synchronization of reaction rates across different reactors. The results indicate that manipulation of process parameters allows for flexible adjustment of the H2/CO ratio in syngas (ranging from 1.02 to 3.83). The introduction of CO2 feed in the first stage regeneration reactor reduces the oxygen carrier exothermic intensity in the second stage regeneration reactor by 58%. Optimization results suggest that the generated syngas is compatible with diverse downstream applications, exhibiting a maximum CO2 negative emission of 1.85 kg/kg syngas. The PCLR‐TR system offers a versatile and environmentally friendly solution for the energy and chemical industries.

The integrated analysis of gut microbiota and metabolome revealed steroid hormone biosynthesis is a critical pathway in liver regeneration after 2/3 partial hepatectomy.

Introduction: The liver is the only organ capable of full regeneration in mammals. However, the exact mechanism of gut microbiota and metabolites derived from them relating to liver regeneration has not been fully elucidated. Methods: To demonstrate how the gut-liver axis contributes to liver regeneration, using an LC-QTOF/MS-based metabolomics technique, we examine the gut microbiota-derived metabolites in the gut content of C57BL/6J mice at various points after 2/3 partial hepatectomy (PHx). Compound identification, multivariate/univariate data analysis and pathway analysis were performed subsequently. The diversity of the bacterial communities in the gastrointestinal content was measured using 16S rRNA gene sequencing. Then, the integration analysis of gut microbiota and metabolome was performed. Results: After 2/3 PHx, the residual liver proliferated quickly in the first 3days and had about 90% of its initial weight by the seventh day. The results of PLS-DA showed that a significant metabolic shift occurred at 6h and 36h after 2/3 PHx that was reversed at the late phase of liver regeneration. The α and β-diversity of the gut microbiota significantly changed at the early stage of liver regeneration. Specifically, Escherichia Shigella, Lactobacillus, Akkermansia, and Muribaculaceae were the bacteria that changed the most considerably during liver regeneration. Further pathway analysis found the most influenced co-metabolized pathways between the host and gut bacteria including glycolysis, the TCA cycle, arginine metabolism, glutathione metabolism, tryptophan metabolism, and purine and pyrimidine metabolism. Specifically, steroid hormone biosynthesis is the most significant pathway of the host during liver regeneration. Discussion: These findings revealed that during liver regeneration, there was a broad modification of gut microbiota and systemic metabolism and they were strongly correlated. Targeting specific gut bacterial strains, especially increasing the abundance of Akkermansia and decreasing the abundance of Enterobacteriaceae, may be a promising beneficial strategy to modulate systemic metabolism such as amino acid and nucleotide metabolism and promote liver regeneration.

Transcriptomic Analysis across Crayfish (Cherax quadricarinatus) Claw Regeneration Reveals Potential Stem Cell Sources for Cultivated Crustacean Meat.

In the face of rising global demand and unsustainable production methods, cultivated crustacean meat (CCM) is proposed as an alternative means to produce delicious lobster, shrimp, and crab products. Cultivated meat requires starting stem cells that may vary in terms of potency and the propensity to proliferate or differentiate into myogenic (muscle-related) tissues. Recognizing that regenerating limbs are a non-lethal source of tissue and may harbor relevant stem cells, we selected those of the crayfish Cherax quadricarinatus as our model. To investigate stem cell activity, we conducted RNA-Seq analysis across six stages of claw regeneration (four pre-molt and two post-molt stages), along with histology and real-time quantitative PCR (qPCR). Our results showed that while genes related to energy production, muscle hypertrophy, and exoskeletal cuticle synthesis dominated the post-molt stages, growth factor receptors (FGFR, EGFR, TGFR, and BMPR) and those related to stem cell proliferation and potency (Cyclins, CDKs, Wnts, C-Myc, Klf4, Sox2, PCNA, and p53) were upregulated before the molt. Pre-molt upregulation in several genes occurred in two growth peaks; Stages 2 and 4. We therefore propose that pre-molt limb regeneration tissues, particularly those in the larger Stage 4, present a prolific and non-lethal source of stem cells for CCM development.

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.

Changes in protein fluxes and gene expression in non-injured muscle tissue distant from an acute myotoxic injury in male mice.

The response to acute myotoxic injury requires stimulation of local repair mechanisms in the damaged tissue. However, satellite cells in muscle distant from acute injury have been reported to enter a functional state between quiescence and active proliferation. Here, we asked whether protein flux rates are altered in muscle distant from acute local myotoxic injury and how they compare to changes in gene expression from the same tissue. Broad and significant alterations in protein turnover were observed across the proteome in the limb contralateral to injury during the first 10days after. Interestingly, mRNA changes had almost no correlation with directly measured protein turnover rates. In summary, we show consistent and striking changes in protein flux rates in muscle tissue contralateral to myotoxic injury, with no correlation between changes in mRNA levels and protein synthesis rates. This work motivates further investigation of the mechanisms, including potential neurological factors, responsible for this distant effect. KEY POINTS: Previous literature demonstrates that stem cells of uninjured muscle respond to local necrotic muscle tissue damage and regeneration. We show that muscle tissue that was distant from a model of local necrotic damage had functional changes at both the gene expression and the protein turnover level. However, these changes in distant tissue were more pronounced during the earlier stages of tissue regeneration and did not correlate well with each other. The results suggest communication between directly injured tissue and non-affected tissues that are distant from injury, which warrants further investigation into the potential of this mechanism as a proactive measure for tissue regeneration from damage.

Role of mesenchymal stem cell conditioned medium on wound healing using a developed 3D skin model.

Alternative 3-dimensional (3D) skin models that replicate in vivo human skin are required to investigate important events during wound healing, such as collective cell migration, epidermal layer formation, dermal substrate formation, re-epithelialisation and collagen production. In this study, a matched human 3D skin equivalent model (3D-SEM) was developed from human skin cells (fibroblast and keratinocytes), characterised using haematoxylin and eosin, immunofluorescence staining and microRNA profiling. The 3D-SEM was then functionally tested for its use in wound healing studies. Mesenchymal stem cells (MSCs) were isolated and characterised according to the criteria stipulated by the International Society for Cell Therapy. Cytokine and growth factor secretions were analysed by enzyme-linked immunosorbent assay. MSC-conditioned medium (MSC-CM) was then tested for wound healing capacity using the developed 3D-SEM at different timepoints i.e., at one, two and four weeks. The constructed 3D-SEM showed consistent development of skin-like structures composed of dermal layers and epidermal layers, with the ability to express epidermal differentiation markers and full stratification. They also showed prolonged longevity in culture media, retaining full differentiation and stratification within the four weeks. MicroRNA profiling revealed a strong correlation in microRNA expression between the developed 3D-SEM and the original native skin (p<0.001; R=0.64). Additionally, MSC-CM significantly enhanced migration, proliferation and differentiation of epidermal cells in the wounded models compared to control models at the different timepoints. In conclusion, in this study, the developed 3D-SEM mimicked native skin at the cellular and molecular levels, and clearly showed the important stages of skin regeneration during the healing process. MSC secretome contains growth factors that play a pivotal role in the healing process and could be used as a therapeutic option to accelerate skin healing.