Finding Solutions for Fibrosis: Understanding the Innate Mechanisms Used by Super-Regenerator Vertebrates to Combat Scarring

Unveiling the therapeutic journey of snail mucus in diabetic wound care

A diabetic wound (DW) is an alteration in the highly orchestrated physiological sequence of wound healing especially, the inflammatory phase. These alterations result in the generation of oxidative stress and inflammation at the injury site. This further leads to the impairment in the angiogenesis, extracellular matrix, collagen deposition, and re-epithelialization. Additionally, in DW there is the presence of microbial load which makes the wound worse and impedes the wound healing cycle. There are several treatment strategies which have been employed by the researchers to mitigate the aforementioned challenges. However, they failed to address the multifactorial pathogenic nature of the disease. Looking at the severity of the disease researchers have explored snail mucus and its components such as achacin, allantoin, elastin, collagen, and glycosaminoglycan due to its multiple therapeutic potentials; however, glycosaminoglycan (GAGs) is very important among all because they accelerate the wound-healing process by promoting reepithelialization, vascularization, granulation, and angiogenesis at the site of injury. Despite its varied applications, the field of snail mucus in wound healing is still underexplored. The present review aims to highlight the role of snail mucus in diabetic wound healing, the advantages of snail mucus over conventional treatments, the therapeutic potential of snail mucus, and the application of snail mucus in DW. Additionally, clinical trials, patents, structural variations, and advancements in snail mucus characterization have been covered in the article.

Biodegradable Double-Layer Hydrogels with Sequential Drug Release for Multi-Phase Collaborative Regulation in Scar-Free Wound Healing

Scarring is a prevalent and often undesirable outcome of the wound healing process, impacting millions worldwide. The complex and dynamic nature of wound healing, including hemostasis, inflammation, proliferation, and remodeling, necessitates precise, making it hard for stage-specific interventions to prevent pathological scarring. This study introduces a double-layer hydrogel system designed for sequential drug release, aligning with the stage-specific need for wound healing. The lower layer, containing curcumin-loaded chitosan nanoparticles, shows early anti-inflammatory and antioxidant effects, while the upper layer, with pirfenidone-encapsulated gelatin microspheres, presents late-stage anti-fibrotic activity. The hydrogel's unique design, with varying degradation rates and mechanical properties in each layer, facilitates cascade drug release in synchrony with wound healing stages. Rapid release of curcumin from the lower layer promotes proliferation by mitigating inflammation and oxidative stress, while the sustained release of pirfenidone from the upper layer inhibits excessive fibrillation during late proliferation and remodeling. In a rat model of full-thickness skin defect, treatment with a double-layer hydrogel drug delivery system accelerated the wound closure, improved scar quality, and promoted the formation of hair follicles. Therefore, this innovative approach lays a promising foundation for future clinical applications in anti-scar therapies, offering a significant advancement in wound care and regenerative medicine.

Molecular Imaging of Fibroblast Activation Protein in Response to Cardiac Injury Using [68Ga]Ga-DATA5m.SA.FAPi

Background/Objectives: Fibroblast activation protein (FAP) has gained tremendous traction as a target for tumor imaging and cancer treatment, while also playing a key role in fibrosis. Our study aimed to evaluate [68Ga]Ga-DATA5m.SA.FAPi for PET imaging of replacement fibrosis following myocardial infarction (MI) or interstitial fibrosis associated with hypertrophy. Methods: MI or transverse aortic constriction (TAC)-induced hypertrophy was induced in C57BL/6 mice, with sham-operated animals serving as controls. At multiple time points during disease progression (1, 2, and 6 weeks post-surgery), [68Ga]Ga-DATA5m.SA.FAPi PET/CT scans were performed, followed by ex vivo investigations. Additionally, in vitro cell uptake experiments simulating hypertrophy were conducted. Results: Cardiac uptake of [68Ga]Ga-DATA5m.SA.FAPi significantly increased two weeks after MI induction (MI: 2.1 ± 0.2%ID/g, n = 7 vs. SHAM: 1.1 ± 0.2%ID/g, n = 5; p = 0.002), confirmed by ex vivo autoradiography. No significant difference was observed at six weeks post-MI (MI: 1.1 ± 0.1%ID/g, n = 4 vs. SHAM: 0.8 ± 0.0%ID/g, n = 3), indicating infarct healing completion. In contrast, TAC mice showed increased uptake after six weeks (TAC: 1.8 ± 0.2%ID/g, n = 6; p = 0.007), related to interstitial fibrosis progression. Consistently, high-stretched cardiac fibroblasts demonstrated a higher uptake compared to low-stretched conditioned ones, suggesting the stretch mediates regulation of FAP. Conclusions: This study demonstrated the efficacy of [68Ga]Ga-DATA5m.SA.FAPi for longitudinal imaging of cardiac fibrosis in response to different cardiac injuries. In vivo FAP imaging during cardiac remodeling may serve as a valuable tool for diagnosing and predicting disease progression, ultimately aiding in the clinical management of patients.

Nanomanaging Chronic Wounds with Targeted Exosome Therapeutics

Chronic wounds pose a significant healthcare challenge, impacting millions of patients worldwide and burdening healthcare systems substantially. These wounds often occur as comorbidities and are prone to infections. Such infections hinder the healing process, complicating clinical management and proving recalcitrant to therapy. The environment within the wound itself poses challenges such as lack of oxygen, restricted blood flow, oxidative stress, ongoing inflammation, and bacterial presence. Traditional systemic treatment for such chronic peripheral wounds may not be effective due to inadequate blood supply, resulting in unintended side effects. Furthermore, topical applications are often impervious to persistent biofilm infections. A growing clinical concern is the lack of effective therapeutic modalities for treating chronic wounds. Additionally, the chemically harsh wound microenvironment can reduce the effectiveness of treatments, highlighting the need for drug delivery systems that can deliver therapies precisely where needed with optimal dosages. Compared to cell-based therapies, exosome-based therapies offer distinct advantages as a cell-free approach for chronic wound treatment. Exosomes are of endosomal origin and enable cell-to-cell communications, and they possess benefits, including biocompatibility and decreased immunogenicity, making them ideal vehicles for efficient targeting and minimizing off-target damage. However, exosomes are rapidly cleared from the body, making it difficult to maintain optimal therapeutic concentrations at wound sites. The hydrogel-based approach and development of biocompatible scaffolds for exosome-based therapies can be beneficial for sustained release and prolong the presence of these therapeutic exosomes at chronic wound sites. Engineered exosomes have been shown to possess stability and effectiveness in promoting wound healing compared to their unmodified counterparts. Significant progress has been made in this field, but further research is essential to unlock their clinical potential. This review seeks to explore the benefits and opportunities of exosome-based therapies in chronic wounds, ensuring sustained efficacy and precise delivery despite the obstacles posed by the wound environment.

The paradigm of stem cell secretome in tissue repair and regeneration: Present and future perspectives

As the number of patients requiring organ transplants continues to rise exponentially, there is a dire need for therapeutics, with repair and regenerative properties, to assist in alleviating this medical crisis. Over the past decade, there has been a shift from conventional stem cell treatments towards the use of the secretome, the protein and factor secretions from cells. These components may possess novel druggable targets and hold the key to profoundly altering the field of regenerative medicine. Despite the progress in this field, clinical translation of secretome-containing products is limited by several challenges including but not limited to ensuring batch-to-batch consistency, the prevention of further heterogeneity, production of sufficient secretome quantities, product registration, good manufacturing practice protocols and the pharmacokinetic/pharmacodynamic profiles of all the components. Despite this, the secretome may hold the key to unlocking the regenerative blockage scientists have encountered for years. This review critically analyses the secretome derived from different cell sources and used in several tissues for tissue regeneration. Furthermore, it provides an overview of the current delivery strategies and the future perspectives for the secretome as a potential therapeutic. The success and possible shortcomings of the secretome are evaluated.

Adaptive immunity of materials: Implications for tissue healing and regeneration

Recent cumulative findings signify the adaptive immunity of materials as a key agenda in tissue healing that can improve regenerative events and outcomes. Modulating immune responses, mainly the recruitment and functions of T and B cells and their further interplay with innate immune cells (e.g., dendritic cells, macrophages) can be orchestrated by materials. For instance, decellularized matrices have been shown to promote muscle healing by inducing T helper 2 (Th2) cell immunity, while synthetic biopolymers exhibit differential effects on B cell responses and fibrosis compared decellularized matrices. We discuss the recent findings on how implantable materials instruct the adaptive immune events and the subsequent tissue healing process. In particular, we dissect the materials' physicochemical properties (shape, size, topology, degradation, rigidity, and matrix dynamic mechanics) to demonstrate the relations of these parameters with the adaptive immune responses in vitro and the underlying biological mechanisms. Furthermore, we present evidence of recent in vivo phenomena, including tissue healing, cancer progression, and fibrosis, wherein biomaterials potentially shape adaptive immune cell functions and in vivo outcomes. Our discussion will help understand the materials-regulated immunology events more deeply, and offer the design rationale of materials with tunable matrix properties for accelerated tissue repair and regeneration.

A Skin Stress Shielding Platform Based on Body Temperature-Induced Shrinking of Hydrogel for Promoting Scar-Less Wound Healing

Stress concentration surrounding wounds drives fibroblasts into a state of high mechanical tension, leading to the delay of wound healing, exacerbating pathological fibrosis, and even causing tissue dysfunction. Here, an innovative skin stress-shielding hydrogel wound dressing is reported that makes the wound sites shrink as a response to body temperature and then remolds the stress micro-environment of wound sites to reduce the formation of skin scars. Composed of a modified natural temperature-sensitive polymer cross-linked with polyacrylic acid networks, this hydrogel wound dressing has demonstrated a substantial decrease in scar area for full-thickness wounds in rat models. The physical forces exerted by the wound dressing are instrumental in attenuating the activation and transduction of fibroblasts within the wound sites, thereby mitigating the excessive deposition of the extracellular matrix (ECM). Notably, the wound dressing significantly down-regulates the expression of transforming growth factor-β1(TGF-β1) and collagen I, while concurrently exerting a dramatic inhibitory effect on the integrin-focal adhesion kinase (FAK)/phosphorylated-FAK (p-FAK) signaling pathway. Collectively, the fabrication of functional hydrogels with a stress-shielding profile is a new route for achieving scar-less wound healing, thus offering immense potential for improving clinical outcomes and restoring tissue integrity.

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.

Exploring the underlying pharmacological, immunomodulatory, and anti-inflammatory mechanisms of phytochemicals against wounds: a molecular insight

BACKGROUND

Numerous cellular, humoral, and molecular processes are involved in the intricate process of wound healing.

PHARMACOLOGICAL RELEVANCE

Numerous bioactive substances, such as ß-sitosterol, tannic acid, gallic acid, protocatechuic acid, quercetin, ellagic acid, and pyrogallol, along with their pharmacokinetics and bioavailability, have been reviewed. These phytochemicals work together to promote angiogenesis, granulation, collagen synthesis, oxidative balance, extracellular matrix (ECM) formation, cell migration, proliferation, differentiation, and re-epithelialization during wound healing.

FINDINGS AND NOVELTY

To improve wound contraction, this review delves into how the application of each bioactive molecule mediates with the inflammatory, proliferative, and remodeling phases of wound healing to speed up the process. This review also reveals the underlying mechanisms of the phytochemicals against different stages of wound healing along with the differentiation of the in vitro evidence from the in vivo evidence There is growing interest in phytochemicals, or plant-derived compounds, due their potential health benefits. This calls for more scientific analysis and mechanistic research. The various pathways that these phytochemicals control/modulate to improve skin regeneration and wound healing are also briefly reviewed. The current review also elaborates the immunomodulatory modes of action of different phytochemicals during wound repair.

Effects of the Biomimetic Microstructure in Electrospun Fiber Sutures and Mechanical Tension on Tissue Repair

Electrospun microfibers, designed to emulate the extracellular matrix (ECM), play a crucial role in regulating the cellular microenvironment for tissue repair. Understanding their mechanical influence and inherent biological interactions at the ECM interface, however, remains a complex challenge. This study delves into the role of mechanical cues in tissue repair by fabricating Col/PLCL microfibers with varying chemical compositions and alignments that mimic the structure of the ECM. Furthermore, we optimized these microfibers to create the Col/PLCL@PDO aligned suture, with a specific emphasis on mechanical tension in tissue repair. The result reveals that within fibers of identical chemical composition, fibroblast proliferation is more pronounced in aligned fibers than in unaligned ones. Moreover, cells on aligned fibers exhibit an increased aspect ratio. In vivo experiments demonstrated that as the tension increased to a certain level, cell proliferation augmented, cells assumed more elongated morphologies with distinct protrusions, and there was an elevated secretion of collagen III and tension suture, facilitating soft tissue repair. This research illuminates the structural and mechanical dynamics of electrospun fiber scaffolds; it will provide crucial insights for the advancement of precise and controllable tissue engineering materials.

Transdermal Transfersome Nanogels Control Hypertrophic Scar Formation via Synergy of Macrophage Phenotype-Switching and Anti-Fibrosis Effect

Hypertrophic scar (HS), which results from prolonged inflammation and excessive fibrosis in re-epithelialized wounds, is one of the most common clinical challenges. Consequently, sophisticated transdermal transfersome nanogels (TA/Fu-TS) are prepared to control HS formation by synergistically inhibiting inflammation and suppressing fibrosis. TA/Fu-TSs have unique structures comprising hydrophobic triamcinolone acetonide (TA) in lipid multilayers and hydrophilic 5-fluorouracil in aqueous cores, and perform satisfactorily with regard to transdermal co-delivery to macrophages and HS fibroblasts in emerging HS tissues. According to the in vitro/vivo results, TA/Fu-TSs not only promote macrophage phenotype-switching to inhibit inflammation by interleukin-related pathways, but also suppress fibrosis to remodel extracellular matrix by collagen-related pathways. Therefore, TA/Fu-TSs overcome prolonged inflammation and excessive fibrosis in emerging HS tissues, and provide an effective therapeutic strategy for controlling HS formation via their synergy of macrophage phenotype-switching and anti-fibrosis effect.

Macrophages modulate fibrosis during newt lens regeneration

Background

Previous studies indicated that macrophages play a role during lens regeneration in newts, but their function has not been tested experimentally.

Methods

Here we generated a transgenic newt reporter line in which macrophages can be visualized in vivo. Using this new tool, we analyzed the location of macrophages during lens regeneration. We uncovered early gene expression changes using bulk RNAseq in two newt species, Notophthalmus viridescens and Pleurodeles waltl. Next, we used clodronate liposomes to deplete macrophages, which inhibited lens regeneration in both newt species.

Results

Macrophage depletion induced the formation of scar-like tissue, an increased and sustained inflammatory response, an early decrease in iris pigment epithelial cell (iPEC) proliferation and a late increase in apoptosis. Some of these phenotypes persisted for at least 100 days and could be rescued by exogenous FGF2. Re-injury alleviated the effects of macrophage depletion and re-started the regeneration process.

Conclusions

Together, our findings highlight the importance of macrophages in facilitating a pro-regenerative environment in the newt eye, helping to resolve fibrosis, modulating the overall inflammatory landscape and maintaining the proper balance of early proliferation and late apoptosis.

Microneedle-mediated drug delivery for scar prevention and treatment

Scars are an inevitable natural outcome of most wound healing processes and affect skin functions, leading to cosmetic, psychological and social problems. Several strategies, including surgery, radiation, cryotherapy, laser therapy, pressure therapy and corticosteroids, can be used to either prevent or treat scars. However, these strategies are ineffective, have side effects and are typically expensive. Microneedle (MN) technology is a powerful, minimally invasive platform for transdermal drug delivery. This review discusses the most recent progress in MN-mediated drug delivery to prevent and treat pathological scars (hypertrophic and keloids). A comprehensive overview of existing challenges and future perspectives is also provided.

Unraveling the potential of 3D bioprinted immunomodulatory materials for regulating macrophage polarization: State-of-the-art in bone and associated tissue regeneration

Macrophage-assisted immunomodulation is an alternative strategy in tissue engineering, wherein the interplay between pro-inflammatory and anti-inflammatory macrophage cells and body cells determines the fate of healing or inflammation. Although several reports have demonstrated that tissue regeneration depends on spatial and temporal regulation of the biophysical or biochemical microenvironment of the biomaterial, the underlying molecular mechanism behind immunomodulation is still under consideration for developing immunomodulatory scaffolds. Currently, most fabricated immunomodulatory platforms reported in the literature show regenerative capabilities of a particular tissue, for example, endogenous tissue (e.g., bone, muscle, heart, kidney, and lungs) or exogenous tissue (e.g., skin and eye). In this review, we briefly introduced the necessity of the 3D immunomodulatory scaffolds and nanomaterials, focusing on material properties and their interaction with macrophages for general readers. This review also provides a comprehensive summary of macrophage origin and taxonomy, their diverse functions, and various signal transduction pathways during biomaterial-macrophage interaction, which is particularly helpful for material scientists and clinicians for developing next-generation immunomodulatory scaffolds. From a clinical standpoint, we briefly discussed the role of 3D biomaterial scaffolds and/or nanomaterial composites for macrophage-assisted tissue engineering with a special focus on bone and associated tissues. Finally, a summary with expert opinion is presented to address the challenges and future necessity of 3D bioprinted immunomodulatory materials for tissue engineering.

The salamander blastema within the broader context of metazoan regeneration

Throughout the animal kingdom regenerative ability varies greatly from species to species, and even tissue to tissue within the same organism. The sheer diversity of structures and mechanisms renders a thorough comparison of molecular processes truly daunting. Are "blastemas" found in organisms as distantly related as planarians and axolotls derived from the same ancestral process, or did they arise convergently and independently? Is a mouse digit tip blastema orthologous to a salamander limb blastema? In other fields, the thorough characterization of a reference model has greatly facilitated these comparisons. For example, the amphibian Spemann-Mangold organizer has served as an amazingly useful comparative template within the field of developmental biology, allowing researchers to draw analogies between distantly related species, and developmental processes which are superficially quite different. The salamander limb blastema may serve as the best starting point for a comparative analysis of regeneration, as it has been characterized by over 200 years of research and is supported by a growing arsenal of molecular tools. The anatomical and evolutionary closeness of the salamander and human limb also add value from a translational and therapeutic standpoint. Tracing the evolutionary origins of the salamander blastema, and its relatedness to other regenerative processes throughout the animal kingdom, will both enhance our basic biological understanding of regeneration and inform our selection of regenerative model systems.

Unresolved Excess Accumulation of Myelin-Derived Cholesterol Contributes to Scar Formation after Spinal Cord Injury

Spinal cord injury triggers complex pathological cascades, resulting in destructive tissue damage and incomplete tissue repair. Scar formation is generally considered a barrier for regeneration in the central nervous system. However, the intrinsic mechanism of scar formation after spinal cord injury has not been fully elucidated. Here, we report that excess cholesterol accumulates in phagocytes and is inefficiently removed from spinal cord lesions in young adult mice. Interestingly, we observed that excessive cholesterol also accumulates in injured peripheral nerves but is subsequently removed by reverse cholesterol transport. Meanwhile, preventing reverse cholesterol transport leads to macrophage accumulation and fibrosis in injured peripheral nerves. Furthermore, the neonatal mouse spinal cord lesions are devoid of myelin-derived lipids and can heal without excess cholesterol accumulation. We found that transplantation of myelin into neonatal lesions disrupts healing with excessive cholesterol accumulation, persistent macrophage activation, and fibrosis. Myelin internalization suppresses macrophage apoptosis mediated by CD5L expression, indicating that myelin-derived cholesterol plays a critical role in impaired wound healing. Taken together, our data suggest that the central nervous system lacks an efficient approach for cholesterol clearance, resulting in excessive accumulation of myelin-derived cholesterol, thereby inducing scar formation after injury.

Combinational System of Lipid-Based Nanocarriers and Biodegradable Polymers for Wound Healing: An Updated Review

Skin wounds have imposed serious socioeconomic burdens on healthcare providers and patients. There are just more than 25,000 burn injury-related deaths reported each year. Conventional treatments do not often allow the re-establishment of the function of affected regions and structures, resulting in dehydration and wound infections. Many nanocarriers, such as lipid-based systems or biobased and biodegradable polymers and their associated platforms, are favorable in wound healing due to their ability to promote cell adhesion and migration, thus improving wound healing and reducing scarring. Hence, many researchers have focused on developing new wound dressings based on such compounds with desirable effects. However, when applied in wound healing, some problems occur, such as the high cost of public health, novel treatments emphasizing reduced healthcare costs, and increasing quality of treatment outcomes. The integrated hybrid systems of lipid-based nanocarriers (LNCs) and polymer-based systems can be promising as the solution for the above problems in the wound healing process. Furthermore, novel drug delivery systems showed more effective release of therapeutic agents, suitable mimicking of the physiological environment, and improvement in the function of the single system. This review highlights recent advances in lipid-based systems and the role of lipid-based carriers and biodegradable polymers in wound healing.

New insights into balancing wound healing and scarless skin repair

Scars caused by skin injuries after burns, wounds, abrasions and operations have serious physical and psychological effects on patients. In recent years, the research of scar free wound repair has been greatly expanded. However, understanding the complex mechanisms of wound healing, in which various cells, cytokines and mechanical force interact, is critical to developing a treatment that can achieve scarless wound healing. Therefore, this paper reviews the types of wounds, the mechanism of scar formation in the healing process, and the current research progress on the dual consideration of wound healing and scar prevention, and some strategies for the treatment of scar free wound repair.

Newtic1 Is a Component of Globular Structures That Accumulate along the Marginal Band of Erythrocytes in the Limb Blastema of Adult Newt, Cynops pyrrhogaster

In adult newts, when a limb is amputated, a mesenchymal cell mass called the blastema is formed on the stump, where blood vessels filled with premature erythrocytes, named polychromatic normoblasts (PcNobs), elongate. We previously demonstrated that PcNobs in the blastema express an orphan gene, Newtic1, and that they secrete growth factors such as BMP2 and TGFβ1 into the surrounding tissues. However, the relationship between Newtic1 expression and growth factor secretion was not clear since Newtic1 was thought to encode a membrane protein. In this study, we addressed this issue using morphological techniques and found that the Newtic1 protein is a component of globular structures that accumulate at the marginal band in the cytoplasm along the equator of PcNobs. Newtic1-positive (Newtic1(+)) globular structures along the equator were found only in PcNobs with a well-developed marginal band in the blastema. Newtic1(+) globular structures were associated with microtubules and potentially incorporated TGFβ1. Based on these observations, we propose a hypothesis that the Newtic1 protein localizes to the membrane of secretory vesicles that primarily carry TGFβ1 and binds to microtubules, thereby tethering secretory vesicles to microtubules and transporting them to the cell periphery as the marginal band develops.

Cellular Senescence in Aging, Tissue Repair, and Regeneration

SUMMARY

Society and our healthcare system are facing unprecedented challenges due to the expansion of the older population. As plastic surgeons, we can improve care of our older patients through understanding the mechanisms of aging that inevitably impact their outcomes and well-being. One of the major hallmarks of aging, cellular senescence, has recently become the focus of vigorous research in academia and industry. Senescent cells, which are metabolically active but in a state of stable cell cycle arrest, are implicated in causing aging and numerous age-related diseases. Further characterization of the biology of senescence revealed that it can be both detrimental and beneficial to organisms depending on tissue context and senescence chronicity. Here, we review the role of cellular senescence in aging, wound healing, tissue regeneration, and other domains relevant to plastic surgery. We also review the current state of research on therapeutics that modulate senescence to improve conditions of aging.

Screening Biophysical Sensors and Neurite Outgrowth Actuators in Human Induced-Pluripotent-Stem-Cell-Derived Neurons

All living cells maintain a charge distribution across their cell membrane (membrane potential) by carefully controlled ion fluxes. These bioelectric signals regulate cell behavior (such as migration, proliferation, differentiation) as well as higher-level tissue and organ patterning. Thus, voltage gradients represent an important parameter for diagnostics as well as a promising target for therapeutic interventions in birth defects, injury, and cancer. However, despite much progress in cell and molecular biology, little is known about bioelectric states in human stem cells. Here, we present simple methods to simultaneously track ion dynamics, membrane voltage, cell morphology, and cell activity (pH and ROS), using fluorescent reporter dyes in living human neurons derived from induced neural stem cells (hiNSC). We developed and tested functional protocols for manipulating ion fluxes, membrane potential, and cell activity, and tracking neural responses to injury and reinnervation in vitro. Finally, using morphology sensor, we tested and quantified the ability of physiological actuators (neurotransmitters and pH) to manipulate nerve repair and reinnervation. These methods are not specific to a particular cell type and should be broadly applicable to the study of bioelectrical controls across a wide range of combinations of models and endpoints.

Down-Regulating Scar Formation by Microneedles Directly via a Mechanical Communication Pathway

Excessive extracellular matrix deposition drives fibroblasts into a state of high mechanical stress, exacerbating pathological fibrosis and hypertrophic scar formation, leading to tissue dysfunction. This study reports a minimally invasive and convenient approach to obtaining scarless tissue using a silk fibroin microneedle patch (SF MNs). We found that by tuning the MN size and density only, the biocompatible MNs significantly decreased the scar elevation index in the rabbit ear hypertrophic scar model and increased ultimate tensile strength close to regular skin. To advance our understanding of this recent approach, we built a fibroblast-populated collagen lattice system and finite element model to study MN-mediated cellular behavior of fibroblasts. We found that the MNs reduced the fibroblasts generated contraction and mechanical stress, as indicated by decreased expression of the mechanical sensitive gene ANKRD1. Specifically, SF MNs attenuated the integrin-FAK signaling and consequently down-regulated the expression of TGF-β1, α-SMA, collagen I, and fibronectin. It resulted in a low-stress microenvironment that helps to reduce scar formation significantly. Microneedles' physical intervention via the mechanotherapeutic strategy is promising for scar-free wound healing.

The amazing and anomalous axolotls as scientific models

Ambystoma mexicanum (axolotl) embryos and juveniles have been used as model organisms for developmental and regenerative research for many years. This neotenic aquatic species maintains the unique capability to regenerate most, if not all, of its tissues well into adulthood. With large externally developing embryos, axolotls were one of the original model species for developmental biology. However, increased access to, and use of, organisms with sequenced and annotated genomes, such as Xenopus laevis and tropicalis and Danio rerio, reduced the prevalence of axolotls as models in embryogenesis studies. Recent sequencing of the large axolotl genome opens up new possibilities for defining the recipes that drive the formation and regeneration of tissues like the limbs and spinal cord. However, to decode the large Ambystoma mexicanum genome will take a herculean effort, community resources, and the development of novel techniques. Here, we provide an updated axolotl-staging chart ranging from 1-cell stage to immature adult paired with a perspective on both historical and current axolotl research that spans from their use in early studies of development to the recent cutting-edge research, employment of transgenesis, high resolution imaging, and study of mechanisms deployed in regeneration. This article is protected by copyright. All rights reserved.