Early Regeneration Research Articles

CUREs for high-level Galectin-3 expression

Galectins are a large and diverse protein family defined by the presence of a carbohydrate recognition domain (CRD) that binds β-galactosides. They play important roles in early development, tissue regeneration, immune homeostasis, pathogen recognition, and cancer. In many cases, studies that examine galectin biology and the effect of manipulating galectins are aided by, or require the ability to express and purify, specific members of the galectin family. In many cases, E. coli is employed as a heterologous expression system, and galectin expression is induced with isopropyl β-galactoside (IPTG). Here, we show that galectin-3 recognizes IPTG with micromolar affinity and that as IPTG induces expression, newly synthesized galectin can bind and sequester cytosolic IPTG, potentially repressing further expression. To circumvent this putative inhibitory feedback loop, we utilized an autoinduction protocol that lacks IPTG, leading to significantly increased yields of galectin-3. Much of this work was done within the context of a course-based undergraduate research experience, indicating the ease and reproducibility of the resulting expression and purification protocols.

Sox9-coordinated cellular neighborhoods generate fibrosis

Poorly regenerative organs deposit scar tissue to mend damage. Aggarwal etal. establish that transient Sox9 activity is necessary for early proximal tubule epithelial regeneration, while Trogisch etal. and Aggarwal etal. show that persistent Sox9 activity in epithelial and endothelial cells activates fibroblasts creating fibrotic microdomains in multiple organs.

Muscle regeneration is not impaired by ablation of UCP-1-expressing cells

INTRODUCTION: Recently, cells expressing uncoupling protein 1 (UCP-1) have been proposed to impact muscle physiology. First, transplant of brown adipose tissue (which has high expression of UCP-1) enhanced regeneration in the injured mouse rotator cuff. Second, isolated UCP-1+ muscle fibroadipogenic progenitors (FAPs) treated to enhance UCP-1 expression improved injured mouse rotator cuff muscle pathology. However, it remains unknown whether endogenous UCP-1-expressing cells contribute to muscle regeneration. Therefore, the objective of this study was to assess whether mice that lack UCP-1-expressing cells demonstrate impaired muscle regeneration following toxin administration. METHODS: Experiments were performed using tibialis anterior (TA) and 5th toe extensor digitorum longus (EDL) muscle of wild type C57BL/6J (WT; n=22), and uncoupling protein 1 diphtheria Toxin A (UCP1-DTA; n=18) mice, which lack all UCP-1 expressing cells. All procedures were performed in accordance with the National Institute of Health’s Guide for the Use and Care of Laboratory Animals and were approved by Washington University School of Medicine IACUC. Muscle injury was induced using intramuscular injection of 50%v/v solution of glycerol. Regeneration was assessed at “early” (7 days post-injury (dpi)), “intermediate” (14 dpi) and “late” (21 dpi) stages. Outcome measures were cell population dynamics by flow cytometry, ex-vivo physiology testing and histological scoring as appropriate for each timepoint. RESULTS: Our preliminary data in early regeneration show that UCP1-DTA mice have significantly greater percentage of FAPs compared to WT mice (29.84 ± 1.24% higher cell population, p<0.0134), however no differences in muscle satellite (stem) cells between genotypes. Physiological and histological outcomes at intermediate and late-stage regeneration find a baseline deficit in muscle mass (23.69 ± 2.3% smaller, p<0.0001), type 2B fiber cross-sectional area (32.56 ± 4.8% smaller, p<0.0001) and normalized muscle active force generation (16.2 ± 3.3% lower force, p<0.0154) in UCP1-DTA compared with WT. However, mass and contractile forces recover to a similar extent between the genotypes following glycerol injection suggesting the phenotypic drivers of the reduced mass and contractile function do not affect muscle regeneration. CONCLUSIONS: Taken together, the data from this study point to a baseline growth deficit in mice lacking UCP-1-expressing cells. However, in two separate timepoints of regeneration (14 and 21dpi), we see that UCP1-DTA mice have similar recovery of mass and normalized contractile force to baseline values suggesting regeneration can proceed normally without UCP-1 expressing cells. However, further data collection will be needed at early-stage regeneration to help discern whether mice lacking UCP-1-expressing cells have initial changes in cell population dynamics given the increased FAP population at 7dpi. ACKNOWLEDGMENTS: This work was supported by R01AR075773 and R21AR071582 to GAM. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Rainfall and soil properties driver the temporal dynamics of arbuscular mycorrhizal fungal assemblages in a seasonally dry tropical forest

The Seasonally Dry Tropical Forests (SDTF), distributed from Mexico to northern Argentina, are habitat to a unique biodiversity. Among these forests, the Caatinga stands out, occupying a large part of the Brazilian Northeast and is subject to cycles of anthropic disturbance and abandonment of exploited areas. Understanding how microbial communities respond to environmental changes is crucial, especially considering the various ecosystem services provided by microorganisms. Among soil microorganisms, arbuscular mycorrhizal fungi (AMF) play a significant role in the maintenance of terrestrial ecosystems. In this study, we aimed to evaluate the structure, composition, and distribution of AMF assemblages, as well as their main drivers, in regeneration areas of the Caatinga. Soil samples were collected in the Catimbau National Park (Pernambuco State), including an old-growth forest representing undisturbed areas, and in early, intermediate, and late regeneration areas. The composition of AMF assemblages differed among regenerating areas and old-growth forest, but their distribution is not related and conditioned to plant assemblages. Instead, soil properties and rainfall are the main factors structuring these assemblages in SDTF. A total of 83 taxa of AMF were identified. Glomus and Acaulospora, which exhibit respectively ruderal and stress-tolerant life strategies were the most abundant genera. The highest number of unique AMF species was recorded in the old-growth forest, contrasting with the late regeneration areas which had the lowest number. The results showed that deterministic processes (soil and rainfall) are structuring the AMF assemblages in areas under regeneration process in SDTF. Plants and AMF do not recover simultaneously over the evaluated regeneration times.

Myeloid Cell-Derived IL-1 Signaling Damps Neuregulin-1 from Fibroblasts to Suppress Colitis-Induced Early Repair of the Intestinal Epithelium.

Neuregulin-1 (Nrg1, gene symbol: Nrg1), a ligand of the ErbB receptor family, promotes intestinal epithelial cell proliferation and repair. However, the dynamics and accurate derivation of Nrg1 expression during colitis remain unclear. By analyzing the public single-cell RNA-sequencing datasets and employing a dextran sulfate sodium (DSS)-induced colitis model, we investigated the cell source of Nrg1 expression and its potential regulator in the process of epithelial healing. Nrg1 was majorly expressed in stem-like fibroblasts arising early in mouse colon after DSS administration, and Nrg1-Erbb3 signaling was identified as a potential mediator of interaction between stem-like fibroblasts and colonic epithelial cells. During the ongoing colitis phase, a significant infiltration of macrophages and neutrophils secreting IL-1β emerged, accompanied by the rise in stem-like fibroblasts that co-expressed Nrg1 and IL-1 receptor 1. By stimulating intestinal or lung fibroblasts with IL-1β in the context of inflammation, we observed a downregulation of Nrg1 expression. Patients with inflammatory bowel disease also exhibited an increase in NRG1+IL1R1+ fibroblasts and an interaction of NRG1-ERBB between IL1R1+ fibroblasts and colonic epithelial cells. This study reveals a novel potential mechanism for mucosal healing after inflammation-induced epithelial injury, in which inflammatory myeloid cell-derived IL-1β suppresses the early regeneration of intestinal tissue by interfering with the secretion of reparative neuregulin-1 by stem-like fibroblasts.

Temporal regulation of the Mediator complex during muscle proliferation, differentiation, regeneration, aging, and disease.

Genesis of skeletal muscle relies on the differentiation and fusion of mono-nucleated muscle progenitor cells into the multi-nucleated muscle fiber syncytium. The temporally-controlled cellular and morphogenetic changes underlying this process are initiated by a series of highly coordinated transcription programs. At the core, the myogenic differentiation cascade is driven by muscle-specific transcription factors, i.e., the Myogenic Regulatory Factors (MRFs). Despite extensive knowledge on the function of individual MRFs, very little is known about how they are coordinated. Ultimately, highly specific coordination of these transcription programs is critical for their masterfully timed transitions, which in turn facilitates the intricate generation of skeletal muscle fibers from a naïve pool of progenitor cells. The Mediator complex links basal transcriptional machinery and transcription factors to regulate transcription and could be the integral component that coordinates transcription factor function during muscle differentiation, growth, and maturation. In this study, we systematically deciphered the changes in Mediator complex subunit expression in skeletal muscle development, regeneration, aging, and disease. We incorporated our in vitro and in vivo experimental results with analysis of publicly available RNA-seq and single nuclei RNA-seq datasets and uncovered the regulation of Mediator subunits in different physiological and temporal contexts. Our experimental results revealed that Mediator subunit expression during myogenesis is highly dynamic. We also discovered unique temporal patterns of Mediator expression in muscle stem cells after injury and during the early regeneration period, suggesting that Mediator subunits may have unique contributions to directing muscle stem cell fate. Although we observed few changes in Mediator subunit expression in aging muscles compared to younger muscles, we uncovered extensive heterogeneity of Mediator subunit expression in dystrophic muscle nuclei, characteristic of chronic muscle degeneration and regeneration cycles. Taken together, our study provides a glimpse of the complex regulation of Mediator subunit expression in the skeletal muscle cell lineage and serves as a springboard for mechanistic studies into the function of individual Mediator subunits in skeletal muscle.

The adjunctive effect of polydeoxyribonucleotide on bone formation in alveolar ridge preservation: A pre-clinical in vivo study.

This study investigated the adjunctive effect of polydeoxyribonucleotide (PDRN) on bone formation in alveolar ridge preservation (ARP) sockets. Both mandibular second, third and fourth premolars of eight beagle dogs were randomly divided into ARP and ARP/PDRN groups. Following tooth extraction, ARP procedures were conducted using collagenized alloplastic graft material and bilayer collagen membrane soaked with normal saline (ARP group) or PDRN (ARP/PDRN group) for 10 min before application. Both groups were also randomly allocated to 2-, 4- or 12-week healing subgroups. The primary endpoint of this study was to compare histomorphometric differences between ARP and ARP/PDRN. The secondary endpoints of this study were to compare micro-CT analysis and three-dimensional volumetric measurement between the two groups. In the histomorphometric analysis, the ARP/PDRN group exhibited greater new bone formation at coronal, middle and total position compared with the ARP group at 2-week healing. The number of newly formed blood vessels was higher in the ARP/PDRN group than in the ARP group at 2- and 4-week healing. In micro-CT analysis, the mean new bone volume/total bone volume between ARP and ARP/PDRN was statistically significant at 2-week healing. Ridge volume alterations were significantly decreased in the ARP/PDRN group during entire healing time compared with the ARP group, especially on the buccal side. The application of PDRN in ARP might provide additional benefits for early bone regeneration and maintenance of buccal ridge volume.

Silk fibroin-gelatin films crosslinked by genipin for regenerating tympanic membrane perforations

The tympanic membrane (TM) integrity is necessary for our normal hearing function. TM perforations pose significant morbidities such as middle ear infection, recurrent otorrhea, hearing loss, and acquired cholesteatoma. Myringoplasty is commonly performed to repair chronic perforations; although various grafts and materials have been utilized to promote TM regeneration, all have associated restrictions. This study aimed to prepare and evaluate the efficacy and feasibility of a tissue-engineered patch based on silk fibroin and gelatin (SF-GT) to improve regeneration. A casting technique was used to make the SF-GT films, using 0–30 v/v% GT, as it is shown that films are remarkably efficient for TM regeneration, easy to mass produce and cheap to make. The surface morphology (SEM), chemical structure (FTIR), crystallinity (XRD), mechanical strength (tensile test), water uptake and in vitro degradation, and cellular biocompatibility (MTT and scratch) were investigated for SF-GT films, and the optimal patch was chosen based on the results (SF-30GT). SF-30GT was used for in vivo studies in a rat model with TM perforations to induce TM regeneration. The morphology of the TM was assessed at days 0, 3, 5, 7, 9 and 11 post-implantation using otoscopy and functional outcomes by auditory brainstem responses (ABRs). This study indicates that compared with the control group (spontaneous healing), the SF-30GT scaffold was more effective in promoting early TM regeneration (complete healing at day 7) and normal hearing (back to 20 dB after healing), suggesting that this scaffold can be a potential substitute for clinical use.

Biodegradable poly(caprolactone fumarate) 3D printed scaffolds for segmental bone defects within the Masquelet technique.

Segmental bone defects, often clinically treated with nondegradable poly(methylmethacrylate) (PMMA) in multistage surgeries, present a significant clinical challenge. Our study investigated the efficacy of 3D printed biodegradable polycaprolactone fumarate (PCLF)/PCL spacers in a one-stage surgical intervention for these defects, focusing on early bone regeneration influenced by spacer porosities. We compared nonporous PCLF/PCL and PMMA spacers, conventionally molded into cylinders, with porous PCLF/PCL spacers, 3D printed to structurally mimic segmental defects in rat femurs for a 4-week implantation study. Histological analysis, including tissue staining and immunohistochemistry with bone-specific antibodies, was conducted for histomorphometry evaluation. The PCLF/PCL spacers demonstrated compressive properties within 6 ± 0.5 MPa (strength) and 140 ± 15 MPa (modulus). Both porous PCLF/PCL and Nonporous PMMA formed collagen-rich membranes (PCLF/PCL: 92% ± 1.3%, PMMA: 86% ± 1.5%) similar to those induced in the Masquelet technique, indicating PCLF/PCL's potential for one-stage healing. Immunohistochemistry confirmed biomarkers for tissue regeneration, underscoring PCLF/PCL's regenerative capabilities. This research highlights PCLF/PCL scaffolds' ability to induce membrane formation in critical-sized segmental bone defects, supporting their use in one-stage surgery. Both solid and porous PCLF/PCL spacers showed adequate compressive properties, with the porous variants exhibiting BMP-2 expression and woven bone formation, akin to clinical standard PMMA. Notably, the early ossification of the membrane into the pores of porous scaffolds suggests potential for bone interlocking and regeneration, potentially eliminating the need for a second surgery required for PMMA spacers. The biocompatibility and biodegradability of PCLF/PCL make them promising alternatives for treating critical bone defects, especially in vulnerable patient groups.

Genetic diversity and structure of Hopea bilitonensis, an endemic Dipterocarp from Belitung Island, Indonesia

Hopea bilitonensis Ashton (Dipterocarpaceae) is a small tree endemic to some islands on the east coast of Sumatra, particularly Belitung Island, Indonesia, and the northwest of Malaysia. Forest fragmentation and degradation in Belitung Island could affect population and genetic diversity of this species. The main objectives of this study are to examine genetic diversity and structure of H. bilitonensis on Belitung Island, Sumatra. Multiplexed ISSR genotyping by sequencing (MIG-seq) is used for genotyping and SNP detection. Genetic diversity and structure were determined using STRUCTURE analysis. We found that genetic diversity of H. bilitonensis is lower in seedlings than in juvenile and mature individuals. In contrast, inbreeding coefficient is lower in mature individuals than in the seedlings and juveniles. Genetic clusters (K=3) are detected in the early regeneration stages. These genetic structure separates the population of seedling and juvenile stages more clearly than in the mature individuals. Representation of these genetic clusters is essential when collecting propagation material for ex-situ conservation and establishing new populations of this threatened species to ensure its sustainability.

Genome-wide analysis of early vascular tunic repair and regeneration for Botrylloides digenesis reveals striking similarities to human wound healing.

The early stages of regeneration after injury are similar to those of wound healing. The ascidian Botrylloides diegensis can regenerate an entire adult from a small fragment of vascular tunic following the removal of all zooids in an injury-induced regeneration model. We investigated the molecular and cellular changes following injury to determine the differences between the healing process and the initiation of whole-body regeneration (WBR). We conducted transcriptome analysis at specific time points during regeneration and wound healing to identify differentially expressed genes (DEGs) and the unique biological processes associated with each state. Our findings revealed 296 DEGs at 10 h post-injury (hpi), with 71 highly expressed in healed tissue and 225 expressed during the WBR process. These DEGs were predicted to play roles in tissue reorganization, integrin signaling, extracellular matrix organization, and the innate immune system. Pathway analysis of the upregulated genes in the healed tunic indicated functional enrichment related to tissue repair, as has been observed in other species.Additionally, we examined the cell types in the tunic and ampullae in both tissue states using histology and in situ hybridization for six genes identified by transcriptome analysis. We observed strong mRNA expression in cells within the WBR tunic, and in small RNA-positive granules near the tunic edge. We hypothesized that many of these genes function in the compaction of the ampullae tunic, which is a pivotal process for WBR and dormancy in B. diegensis, and in an immune response. These findings establish surprising similarities between ascidian regeneration and human wound healing, emphasizing the potential for future investigations into human regenerative and repair mechanisms. This study provides valuable insights into the gene sets specifically activated during regeneration compared to wound healing, shedding light on the divergent activities of these processes.

Shortening fire return interval predisposes west-central Canadian boreal peatlands to more rapid vegetation growth and transition to forest cover.

Climate change in northern latitudes is increasing the vulnerability of peatlands and the riparian transition zones between peatlands and upland forests (referred to as ecotones) to greater frequency of wildland fires. We examined early post-fire vegetation regeneration following the 2011 Utikuma complex fire (central Alberta, Canada). This study examined 779 peatlands and adjacent ecotones, covering an area of ~182 km2 . Based on the known regional fire history, peatlands that burned in 2011 were stratified into either long return interval (LRI) fire regimes of >80 years (i.e., no recorded prior fire history) or short fire return interval (SRI) of 55 years (i.e., within the boundary of a documented severe fire in 1956). Data from six multitemporal airborne lidar surveys were used to quantify trajectories of vegetation change for 8 years prior to and 8 years following the 2011 fire. To date, no studies have quantified the impacts of post-fire regeneration following short versus long return interval fires across this broad range of peatlands with variable environmental and post-fire successional trajectories. We found that SRI peatlands demonstrated more rapid vascular and shrub growth rates, especially in peatland centers, than LRI peatlands. Bogs and fens burned in 1956, and with little vascular vegetation (classified as "open peatlands") prior to the 2011 fire, experienced the greatest changes. These peatlands tended to transition to vascular/shrub forms following the SRI fire, while open LRI peatlands were not significantly different from pre-fire conditions. The results of this study suggest the emergence of a positive feedback, where areas experiencing SRI fires in southern boreal peatlands are expected to transition to forested vegetation forms. Along fen edges and within bog centers, SRI fires are expected to reduce local peatland groundwater moisture-holding capacity and promote favorable conditions for increased fire frequency and severity in the future.

Bioceramic scaffolds with two-step internal/external modification of copper-containing polydopamine enhance antibacterial and alveolar bone regeneration capability.

Magnesium-doped calcium silicate (CS) bioceramic scaffolds have unique advantages in mandibular defect repair; however, they lack antibacterial properties to cope with the complex oral microbiome. Herein, for the first time, the CS scaffold was functionally modified with a novel copper-containing polydopamine (PDA(Cu2+‍)) rapid deposition method, to construct internally modified (*P), externally modified (@PDA), and dually modified (*P@PDA) scaffolds. The morphology, degradation behavior, and mechanical properties of the obtained scaffolds were evaluated in vitro. The results showed that the CS*P@PDA had a unique micro-/nano-structural surface and appreciable mechanical resistance. During the prolonged immersion stage, the release of copper ions from the CS*P@PDA scaffolds was rapid in the early stage and exhibited long-term sustained release. The in vitro evaluation revealed that the release behavior of copper ions ascribed an excellent antibacterial effect to the CS*P@PDA, while the scaffolds retained good cytocompatibility with improved osteogenesis and angiogenesis effects. Finally, the PDA(Cu2+)-modified scaffolds showed effective early bone regeneration in a critical-size rabbit mandibular defect model. Overall, it was indicated that considerable antibacterial property along with the enhancement of alveolar bone regeneration can be imparted to the scaffold by the two-step PDA(Cu2+) modification, and the convenience and wide applicability of this technique make it a promising strategy to avoid bacterial infections on implants.

Factors influencing early natural regeneration in areas under passive restoration in Araucaria Forest, southern Brazil

Factors influencing early natural regeneration in areas under passive restoration in Araucaria Forest, southern Brazil

Reduced corrosion of Zn alloy by HA nanorods for enhancing early bone regeneration.

Zinc alloys have emerged as promising materials for bone regeneration due to their moderate biodegradation rates. However, the blast release of Zn2+ from Zn alloy substrates affects cell behaviors and the subsequent osseointegration quality, retarding their early service performance. To address this issue, extracellular matrix-like hydroxyapatite (HA) nanorods were prepared on Zn-1Ca (ZN) by a combined hydrothermal treatment (HT). HA nanoclusters nucleate on the presetting ZnO layer and grow into nanorods with prolonged HT. HA nanorods protect the ZN substrate from serious corrosion and the corrosion rate is reduced by dozens of times compared with the bare ZN, resulting in a significantly decreased release of Zn2+ ions. The synergistic effect of HA nanorods and appropriate Zn2+ endow ZN implants with obviously improved behaviors of osteoblasts and endothelial cells (e.g. adhesion, proliferation and differentiation) in vitro and new bone formation in vivo. Our work opens up a promising avenue for Zn-based alloys to improve bone regeneration in clinics.

Monocytes as an early risk factor for acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation.

Acute graft-versus-host disease (aGVHD) is a major complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and contributes to high morbidity and mortality. However, our current understanding of the development and progression of aGVHD after allo-HSCT remains limited. To identify the potential biomarkers for the prevention and treatment of aGVHD during the early hematopoietic reconstruction after transplantation, we meticulously performed a comparative analysis of single-cell RNA sequencing data from post-transplant patients with or without aGVHD. Prior to the onset of aGVHD, monocytes in the peripheral blood of patients with aGVHD experienced a dramatic rise and activation on day 21 post-transplantation. This phenomenon is closely aligned with clinical cohort results obtained from blood routine examinations. Furthermore, in vitro co-culture experiments showed that peripheral blood monocytes extracted from patients with aGVHD approximately 21 days post-transplantation induced a significantly higher proliferation rate of allogeneic T cells compared to those from patients without aGVHD. Our study indicates that monocytes could be a crucial early clinical risk factor for the development of aGVHD, and this insight could potentially guide the timing of monitoring efforts, recommending assessments at the pivotal juncture of approximately day 21 post-transplantation, shedding fresh light on the significance of early hematopoietic regeneration in relation to the onset of aGVHD.

Epsti1 Regulates the Inflammatory Stage of Early Muscle Regeneration through STAT1-VCP Interaction.

During muscle regeneration, interferon-gamma (IFN-γ) coordinates inflammatory responses critical for activation of quiescent muscle stem cells upon injury via the Janus kinase (JAK) - signal transducer and activator of transcription 1 (STAT1) pathway. Dysregulation of JAK-STAT1 signaling results in impaired muscle regeneration, leading to muscle dysfunction or muscle atrophy. Until now, the underlying molecular mechanism of how JAK-STAT1 signaling resolves during muscle regeneration remains largely elusive. Here, we demonstrate that epithelial-stromal interaction 1 (Epsti1), an interferon response gene, has a crucial role in regulating the IFN-γ-JAK-STAT1 signaling at early stage of muscle regeneration. Epsti1-deficient mice exhibit impaired muscle regeneration with elevated inflammation response. In addition, Epsti1-deficient myoblasts display aberrant interferon responses. Epsti1 interacts with valosin-containing protein (VCP) and mediates the proteasomal degradation of IFN-γ-activated STAT1, likely contributing to dampening STAT1-mediated inflammation. In line with the notion, mice lacking Epsti1 exhibit exacerbated muscle atrophy accompanied by increased inflammatory response in cancer cachexia model. Our study suggests a crucial function of Epsti1 in the resolution of IFN-γ-JAK-STAT1 signaling through interaction with VCP which provides insights into the unexplored mechanism of crosstalk between inflammatory response and muscle regeneration.

Contribution of Signal Transducer and Activator of Transcription 3 (STAT3) to Bone Development and Repair.

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor activated canonically by numerous cytokines and other factors, with significant roles in immunity, immune diseases, and cancer. It has also been implicated in several human skeletal disorders, with loss-of-function (LOF) mutations associated with aberrant skeletal development. To gain further insights, two zebrafish STAT3 lines were investigated: a complete LOF knockout (KO) mutant and a partial LOF mutant with the transactivation domain truncated (ΔTAD). Consistent with other studies, the KO mutants were smaller, with reduced length in early embryos exacerbated by a decreased growth rate from 5 days postfertilization (dpf). They displayed skeletal deformities that approached 80% incidence by 30 dpf, with a significant reduction in early bone but not cartilage formation. Further analysis additionally identified considerable abrogation of caudal fin regeneration, concomitant with a paucity of infiltrating macrophages and neutrophils, which may be responsible for this. Most of these phenotypes were also observed in the ΔTAD mutants, indicating that loss of canonical STAT3 signaling was the likely cause. However, the impacts on early bone formation and regeneration were muted in the ΔTAD mutant, suggesting the potential involvement of noncanonical functions in these processes.

Transcriptomic analysis reveals the early body wall regeneration mechanism of the sea cucumber Holothuria leucospilota after artificially induced transverse fission

BackgroundSea cucumbers exhibit a remarkable ability to regenerate damaged or lost tissues and organs, making them an outstanding model system for investigating processes and mechanisms of regeneration. They can also reproduce asexually by transverse fission, whereby the anterior and posterior bodies can regenerate independently. Despite the recent focus on intestinal regeneration, the molecular mechanisms underlying body wall regeneration in sea cucumbers still remain unclear.ResultsIn this study, transverse fission was induced in the tropical sea cucumber, Holothuria leucospilota, through constrainment using rubber bands. Histological examination revealed the degradation and loosening of collagen fibers on day-3, followed by increased density but disorganization of the connective tissue on day-7 of regeneration. An Illumina transcriptome analysis was performed on the H. leucospilota at 0-, 3- and 7-days after artificially induced fission. The differential expression genes were classified and enriched by GO terms and KEGG database, respectively. An upregulation of genes associated with extracellular matrix remodeling was observed, while a downregulation of pluripotency factors Myc, Klf2 and Oct1 was detected, although Sox2 showed an upregulation in expression. In addition, this study also identified progressively declining expression of transcription factors in the Wnt, Hippo, TGF-β, and MAPK signaling pathways. Moreover, changes in genes related to development, stress response, apoptosis, and cytoskeleton formation were observed. The localization of the related genes was further confirmed through in situ hybridization.ConclusionThe early regeneration of H. leucospilota body wall is associated with the degradation and subsequent reconstruction of the extracellular matrix. Pluripotency factors participate in the regenerative process. Multiple transcription factors involved in regulating cell proliferation were found to be gradually downregulated, indicating reduced cell proliferation. Moreover, genes related to development, stress response, apoptosis, and cell cytoskeleton formation were also involved in this process. Overall, this study provides new insights into the mechanisms of whole-body regeneration and uncover potential cross-species regenerative-related genes.

The synergistic effects of strontium/magnesium-doped calcium silicate cement accelerates early angiogenesis and bone regeneration through double bioactive ion stimulation

Periodontitis-induced alveolar bone defects necessitate the use of bone grafts for optimal therapeutic outcomes. Therefore, synthetic bone grafts exhibiting consistent properties, sufficient amounts, and multiple application forms have been extensively studied. Our previously designed Ca–Si–Mg cement has demonstrated benefits regarding cell proliferation, osteogenesis, and angiogenesis. Similarly, Sr exhibits osteogenic, anti-osteoclastogenic, and angiogenic properties by influencing several intracellular signaling pathways. In this study, we modified the previously established Ca–Si–Mg cement by incorporating Sr, which resulted in the formation of Mg–Sr-calcium silicate (CS) cement. Furthermore, we evaluated its biocompatibility and efficacy in promoting osteogenesis and angiogenesis. The results revealed that the setting time of the cement was extended with the individual incorporation of either Mg or Sr; notably, the setting time of M5S5 (integrating both Sr and Mg in equal proportions) was 2.7 min shorter than that of M5S0 (integrating only Mg). In addition, the presence of Sr enhanced the mechanical strength to an ultimate strength of 1.89 MPa and reduced the biodegradation rate of the Mg-doped CS cement from a weight loss of 13.9 %–11.5 %. Sr and Mg also demonstrated a synergistic effect on cell proliferation, with no observed cytotoxicity in human periodontal ligament cells (hPDLs). Osteogenic markers such as alkaline phosphate, bone sialoprotein, and osteocalcin were significantly expressed in hPDLs under the combined influence of Mg and Sr on osteogenic activity. Similarly, the angiogenesis-related proteins, vascular endothelial growth factor and angiopoietin-1 exhibited considerable enhancement, indicating the angiogenic capability of M5S5. In summary, our in vitro experiments confirmed that M5S5 is a potential candidate for osteogenic substitutes and alveolar bone regeneration, suggesting its potential applicability in clinical practice.