Injured Tissue Research Articles

Abstract C018: Awakened dormant cancer cells undergo highly mesenchymal to quasi- mesenchymal transition and acquire stemness

Abstract The awakening of dormant disseminated cancer cells is likely responsible for the clinical relapses of patients whose primary tumors have been cured months and even years earlier. In the present study, we demonstrate that dormant breast cancer cells lodged in the lungs reside in a highly mesenchymal, non-proliferative phenotypic state. The awakening of these cells does not occur by a cancer cell-autonomous process. Instead, inflammation and wound healing of the surrounding tissue microenvironment causes them to shift from a highly mesenchymal to a quasi-mesenchymal phenotypic state in which they acquire stemness and proliferative ability. Once awakened, these cells can stably reside in this quasi-mesenchymal state and maintain their stemness, doing so without ongoing heterotypic signaling from the lung microenvironment. EGFR ligands released by the cells of the injured tissue microenvironment, including notably M2 type macrophages, promote dormant cancer cells to move toward this quasi-mesenchymal state, a transition that is essential for the awakening process. An understanding of the mechanisms of metastatic awakening may lead in the future to treatment strategies designed to prevent such awakening and resulting metastatic relapse. Citation Format: Jingwei Zhang, Robert Weinberg. Awakened dormant cancer cells undergo highly mesenchymal to quasi- mesenchymal transition and acquire stemness [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C018.

OS EFEITOS DA LASERTERAPIA EM CICATRIZAÇÃO MAMILAR PARA MULHERES NO PROCESSO DE AMAMENTAÇÃO

INTRODUCTION: Breast milk is a great source of nutrients for the baby's immunological and psychological development, and has a strong impact on infant mortality. It all starts in the thirty-second week of gestation, as this is the time when the fetus begins to show sucking reflexes. The breastfeeding process can be very difficult, since if there is no monitoring, there may be cracks in the breasts, making the process very painful. METHODS: This is a descriptive and qualitative study, which took place in person and virtually in the city of Porto Velho/RO at the Physiotherapy School Clinic of the São Lucas University Center, with the objective of hearing reports from women/mothers who are or have been exclusively breastfeeding. Thirty-eight female women, aged 20 years and older, were selected to report their breastfeeding process as lactating women. RESULTS AND DISCUSSION: One of the reasons for this development is the incorrect breastfeeding process. The main risk factors identified were: the baby's latch on to the mother's breast, where there is incompatibility between mother and child, primary and race/color of the mother defined as white or yellow. Many lactating women end up thinking that all they have to do is let the baby latch on to the breast and perform the suction, since even the positioning of the child interferes in the process. It was also evident in the interviews that most of the women did not perform the procedure due to lack of knowledge, often not being instructed by the health professional, or for fear of the effects of the procedure, since most of the women interviewed are very young and from lower social classes, they end up having this transgression of low performance of the procedure. CONCLUSION: Laser therapy has been shown to be an effective and safe intervention in the treatment of breast fissures, a common complication during breastfeeding that can cause intense pain and difficulties in breastfeeding. By using low-level laser therapy, it is possible to promote healing of injured tissues, relieve pain and reduce inflammation, providing greater comfort to mothers and encouraging continued breastfeeding. The importance of this treatment lies in its rapid and non-invasive effect, offering an alternative to traditional therapies, such as ointments and dressings, which often do not provide immediate or complete relief. In addition, laser therapy helps to prevent early weaning, contributing to the well-being of the baby and the mother, since exclusive breastfeeding is essential in the first months of life.

Microenvironment-Responsive Hydrogel Enclosed with Bioactive Nanoparticle for Synergistic Postoperative Adhesion Prevention.

Postoperative adhesion (PA) is a severe complication of abdominal surgery caused by the inability of clinical physical barriers to cope with diverse pathological factors in the process of PA formation. Herein, we described a multifunctional hydrogel composed of bioactive nanoparticles (BNs) and dual-responsive hydrogel to serve as a combination of physical and pharmacological therapy for preventing PA. Specifically, BNs with pro-inflammatory cell-targeted aggregation were designed by integrating hyaluronic acid onto the polydopamine (PDA)-coated hollow ZrO2 nanoparticles loaded with antimicrobial peptides and platelet lysates that can eliminate bacterial infection and promote tissue repair. PDA can remove the excessive reactive oxygen species (ROS) and thus suppress the oxidative stress damage and accompanying inflammation in the presence of high ROS. The dynamically cross-linked host hydrogel presents injectable yet microenvironment-responsive properties, which enables complete coverage of the uneven tissue and instantly forms a physical barrier to effectively isolate injured tissues and neighboring organs, and synchronously acts as a niche to deliver the BNs in a controlled way. The hydrogel demonstrates a remarkable antiadhesion effect in a rat cecum-abdominal wall adhesion model. Together, this "all-in-one" composite hydrogel strategy capable of a physical barrier capability and pharmacological effects represents a promising clinical solution to prevent PA.

Widespread hyperexcitability of nociceptor somata outlasts enhanced avoidance behavior after incision injury.

Nociceptors with somata in dorsal root ganglia (DRGs) readily switch from an electrically silent state to a hyperactive state of tonic, nonaccommodating, low-frequency, irregular discharge of action potentials (APs). Spontaneous activity (SA) during this state is present in vivo in rats months after spinal cord injury (SCI) and has been causally linked to SCI pain. Intrinsically generated SA and, more generally, ongoing activity (OA) are induced by various neuropathic conditions in rats, mice, and humans and are retained in nociceptor somata after dissociation and culturing, providing a powerful tool for investigating its mechanisms and functions. The present study shows that long-lasting hyperexcitability that can generate OA during modest depolarization in probable nociceptors dissociated from DRGs of male and female rats is induced by plantar incision injury. OA occurred when the soma was artificially depolarized to a level within the normal range of membrane potentials where large, transient depolarizing spontaneous fluctuations (DSFs) can approach AP threshold. This hyperexcitability persisted for at least 3 weeks, whereas behavioral indicators of affective pain-hind paw guarding and increased avoidance of a noxious substrate in an operant conflict test-persisted for 1 week or less. The most consistent electrophysiological alteration associated with OA was enhancement of DSFs. An unexpected discovery after plantar incisions was hyperexcitability in neurons from thoracic DRGs that innervate dermatomes distant from the injured tissue. Potential in vivo functions of widespread, low-frequency nociceptor OA consistent with these and other findings are to contribute to hyperalgesic priming and to drive anxiety-related hypervigilance.

Association between feel-like temperatures and injury risk during international outdoor athletic championships: a prospective cohort study on 29 579 athlete starts during 10 championships

ObjectiveTo analyse associations between feel-like temperatures measured with the universal thermal climate index (UTCI) and injury rates during international athletic championships.MethodsDuring 10 international outdoor athletic championships from 2007 to 2022,...

Clickable immune-microenvironment modulated hydrogels for spinal cord injury repair

Spinal cord injury (SCI) is a devastating condition without effective therapy currently available. The inflammatory cascade following SCI leads to neuronal apoptosis and glial cell activation. The utilization of local injectable hydrogels with immunotherapy drugs directly into injured nerve tissues represents a promising therapeutic strategy. Herein, injectable hydrogels grafted with clickable methylprednisolone (MP) and cellular adhesion peptide were developed using free radical polymerization for promoting nerve regeneration following SCI. MP conjugated hydrogels could modulate the immunoinflammatory microenvironment of SCI and sustain neuron survival. The multi-stiffness hydrogels were fabricated by adjusting concentration ratios to evaluate appropriate mechanical stimuli. In a model of dorsal root ganglion, MP grafted hydrogels with mechanical signals similar to those of adult rat spinal cords demonstrated superior efficacy in promoting dorsal root ganglion growth. MP grafted hydrogels could regulate the immune-inflammatory microenvironment, promote recovery of both motor function and sensory functions. The positive findings suggested that the interplay between immunomodulation and mechanical signals plays a crucial role in promoting nerve regeneration, indicating significant potential for hydrogels as a therapeutic approach for repairing SCI.

Hydrogel Containing Propolis: Physical Characterization and Evaluation of Biological Activities for Potential Use in the Treatment of Skin Lesions.

Skin injury affects the integrity of the skin structure and induces the wound healing process, which is defined by a well-coordinated series of cellular and molecular reactions that aim to recover or replace the injured tissue. Hydrogels are a group of promising biomaterials that are able to incorporate active ingredients for use as dressings. This study aimed to synthesize hydrogels with and without propolis extract and evaluate their physical characteristics and biological activities in vitro for potential use as active dressings in the treatment of skin lesions. The antifungal [Candida albicans (C. albicans) and Candida tropicalis (C. tropicalis)] and antibacterial [Staphylococcus aureus (S. aureus), Pseudomonas aeruginosas (P. aeruginosas) and Escherichia coli (E. coli)] activity was assessed by the microdilution method in plates and antioxidant potential by the reduction of the phosphomolybdate complex. The hydrogels showed good water absorption capacity, high solubility, and high gel fraction, as well as good porosity, water retention, and vapor transmission rates. They revealed a totally amorphous structure. The extract and the hydrogels containing the propolis extract (1.0% and 2.5%) did not inhibit fungal growth. However, they showed antibacterial activity against strains of S. aureus and P. aeruginosas. Regarding the E. coli strain, only the extract inhibited its growth. It showed good antioxidant activity by the evaluation method used. Therefore, the hydrogels containing propolis extract can be a promising alternative with antibacterial and antioxidant action for use as dressings for the treatment of skin lesions.

Cold atmospheric plasma-activated saline alleviates secondary injury post-SCI by inhibiting extracellular matrix remodeling and infiltration of proinflammatory macrophages

BackgroundCold atmospheric plasma (CAP) has been shown to improve the recovery of transected peripheral nerves. We determined the protective role of CAP-activated saline (CAP-AS) treatment in the acute and subacute stages of spinal cord injury (SCI) in mice. MethodsC57BL/6 SCI mice were treated with CAP-AS for 14 days. Injury recovery was assessed weekly for four weeks by conducting motor function tests, including the Basso Mouse Scale (BMS) and footprint test. Transcriptome analysis was conducted on day 14 to elucidate potential mechanisms, which were further validated through immunofluorescence examinations of the injured spinal cord tissues on day 28 and the levels of proinflammatory cytokines produced by macrophages in vitro. ResultsCompared to the SCI group, the CAP-AS-treated groups presented significantly better hindlimb motor function after four weeks. The downregulated (SCI vs. SCI + CAP-AS, with CAP-AS activated for 20 min) differentially expressed genes (DEGs) were enriched in the extracellular region, extracellular matrix (ECM), and ECM-receptor interaction. In contrast, the upregulated DEGs were enriched in immune response-associated pathways. Histological changes in the CAP-AS-treated groups were observed to further validate the predicted mechanisms 28 days post-injury. The alleviation of secondary injury was confirmed by an increase in GFAP-positive and NFH-positive areas, and enhanced outgrowth of 5-HT-positive fibers. Inhibited ECM remodeling was confirmed by a decrease in the areas positive for PDGFRβ, fibronectin, and laminin. A decrease in the infiltration of macrophages and activation of microglia was determined by a decrease in CD68-positive and F4/80-positive areas. The inhibitory effect of CAP-AS on inflammation was further supported by a decrease in the levels of the proinflammatory cytokines IL-1β, IL-6, and TNF-α in CAP-AS-treated M1 macrophages. ConclusionCAP-AS can alleviate secondary injury in SCI model mice by inhibiting ECM remodeling in injured tissues and reducing the infiltration or activation of proinflammatory macrophages/microglia.

Human macrophage polarisation and regulation of angiogenesis and osteogenesis is dependent on culture extracellular matrix and dimensionality

The immune system plays a crucial role in tissue repair and regeneration. Macrophages have been identified as master regulators of the early immune response and healing outcome, by orchestrating the temporal nature of the initial inflammation phase and coordinating the fate of stem/progenitor cells involved in regeneration. However, traditional in-vitro models for the study of macrophages often fail to fully replicate the complexity of the in-vivo microenvironment, therefore generating models which do not fully capture the extensive spectrum of macrophage behaviour seen in native tissues. To this end, we used a hematoma-mimetic 3D fibrin matrix characteristic of early injured tissues to generate a 3D in-vitro model mirroring the local macrophage microenvironment. Leveraging this framework, we demonstrated significant effects of extracellular matrix and dimensionality on macrophage basal signalling and polarisation, achieving more pronounced regenerative phenotypes upon stimulation with the M2a polarisation factors compared to traditional 2D tissue culture conditions. Moreover, this enhanced physiological macrophage behaviour corresponded to increased coordination of angiogenesis and osteogenesis, better mirroring the healing processes seen in-vivo. Taken together, this study demonstrates the critical importance of integrating tissue composition and 3D architecture when investigating the macrophage behaviour in-vitro, establishing a powerful tool that overcomes known limitations associated with traditional 2D culture on plastic, and can be used to identify and validate novel immunomodulation strategies to enhance tissue regeneration.

Two distinct epithelial-to-mesenchymal transition programs control invasion and inflammation in segregated tumor cell populations.

Epithelial-to-mesenchymal transition (EMT) triggers cell plasticity in embryonic development, adult injured tissues and cancer. Combining the analysis of EMT in cell lines, embryonic neural crest and mouse models of renal fibrosis and breast cancer, we find that there is not a cancer-specific EMT program. Instead, cancer cells dedifferentiate and bifurcate into two distinct and segregated cellular trajectories after activating either embryonic-like or adult-like EMTs to drive dissemination or inflammation, respectively. We show that SNAIL1 acts as a pioneer factor in both EMT trajectories, and PRRX1 drives the progression of the embryonic-like invasive trajectory. We also find that the two trajectories are plastic and interdependent, as the abrogation of the EMT invasive trajectory by deleting Prrx1 not only prevents metastasis but also enhances inflammation, increasing the recruitment of antitumor macrophages. Our data unveil an additional role for EMT in orchestrating intratumor heterogeneity, driving the distribution of functions associated with either inflammation or metastatic dissemination.

Ferric Iron/Shikonin Nanoparticle-Embedded Hydrogels with Robust Adhesion and Healing Functions for Treating Oral Ulcers in Diabetes.

Oral ulcers can be addressed using various biomaterials designed to deliver medications or cytokines. Nevertheless, the effectiveness of these substances is frequently limited in many patients due to poor adherence, short retention time in the mouth, and less-than-optimal drug efficacy. In this study, a new hydrogel patch (FSH3) made of a silk fibroin/hyaluronic acid matrix with light-sensitive adhesive qualities infused with ferric iron/shikonin nanoparticles to enhance healing effects is presented. Initially, this hydrogel forms an adhesive barrier over mucosal lesions through a straightforward local injection, solidifying when exposed to UV light. Subsequently, FSH3 demonstrates superior reactive oxygen species elimination and near-infrared photothermal bactericidal activity. These characteristics support bacterial elimination and regulate oxidative levels, promoting a wound's progression from inflammation to tissue regeneration. In a diabetic rat model mimicking oral ulcers, FSH3 significantly speeds up healing by adjusting the inflammatory environment of the injured tissue, maintaining balance in oral microbiota, and promoting faster re-epithelialization. Overall, the light-sensitive FSH3 hydrogel shows potential for rapid wound recovery and may transform therapeutic methods for managing oral ulcers in diabetes.

Tailoring Physicochemical Properties of Photothermal Hydrogels Toward Intrinsically Regenerative Therapies

AbstractPhotothermal hydrogels (PTHs) are considered next‐generation biomaterials as they offer remotely defined biophysical information of the extracellular milieu. PTHs allow precise and non‐genetic control for the regeneration of native tissues, which is the ultimate goal of tissue engineering (TE). Molecular and physical properties of PTHs, such as components, structural configurations, and mechanical characteristics, collectively serve as determinants for understanding the dynamic tissue response and clinical translation. PTHs have entered a period of fruition due to the development of numerous manufacturing technologies and polymeric matrices. Herein, this review comprehensively and meticulously elucidates the mechanisms of regenerative therapeutics underlying the design and fabrication of PTHs. Recent advances in the photothermal principles and various categories of photothermal agents (PTAs) have been extensively discussed. Vital components and structures of PTHs are summarized to enable efficacious and precise therapeutic energy delivery. Emerging applications of PTHs in TE are also demonstrated, which expand the strategies for the intrinsic regeneration of injured tissues. Then deliberate the structural and chemical engineering of PTHs to enhance prognosis while highlighting the challenges associated with clinical translation. In this review, we aim to provide guidance and prospects for exploration and innovation of PTHs in the field of TE.

Freestanding Hydrogen-Bonded Organic Framework Membrane for Efficient Wound Healing.

Hydrogen-bonded organic frameworks (HOFs) are emerging as multifunctional materials with exceptional biocompatibility, abundant active sites, and tunable porosity, which are highly beneficial for advanced wound care. However, a significant challenge involves transforming pristine HOFs powders into lightweight, ultrathin, freestanding membranes compatible with soft biological systems. Herein, the study successfully develops shape-adaptive HOF-based matrix membranes (HMMs) using a polymer-assisted liquid-air interface technique. The HMMs conform seamlessly to tissues of different sizes and shapes, effectively stopping bleeding, and provide high water-vapor permeability. Notably, both in vitro and in vivo studies with mice wound models demonstrated that these tissue-conformable HMMs significantly accelerate wound healing by modulating the inflammatory environment of the injured tissue and promoting rapid re-epithelialization. Furthermore, RNA-seq analysis and mechanistic studies revealed that HMMs effectively reduce inflammation and facilitate the tissue transition from the proliferative stage to the remodeling stage of skin development. This work not only opens up new avenues for advanced wound care materials but also establishes a foundation for hybridizing HOFs with polymers for a wide range of potential applications.

Mesenchymal stem cells suppress inflammation by downregulating interleukin-6 expression in intestinal perforation animal model

Introduction: Intestinal perforation has significant fatality due to sepsis contamination and prolonged inflammation. Studies showed that mesenchymal stem cells (MSCs) secreted cytokines and growth factors to reduce inflammation. This study aims to reveal the role of MSCs in controlling inflammation in intestinal perforation wound healing by measuring interleukin-6 (IL-6) and leukocytes in injured tissue. Materials and methods: A total of 48 rat models with a 10-mm longitudinal incision at the small intestine were divided into four groups: sham, control, Treatment group 1 (T1) injected with MSC doses of 1.5×106 cells and Treatment group 2 (T2) with 3×106 cells. IL-6 expressions were determined using western blot analysis, whereas the leukocyte infiltrations were assessed using the histopathological examination. All variables were evaluated on day 3 and 7. Results: Leukocyte infiltration is significantly lower in T1 and T2 compared to control group in day 3 and 7 (P<0.05), while there were no differences between the two treatment groups. The expression of IL-6 was found to be significantly lower in the T1 and T2 groups compared to the control group on days 3 and 7 (P<0.05), with no significant differences observed between the two treatment groups. Conclusion: MSCs administration in rats with intestinal perforation reduced inflammation by controlling leukocyte infiltration and IL-6 expression.

Polysialic acid driving cardiovascular targeting co-delivery 1,8-cineole and miR-126 to synergistically alleviate lipopolysaccharide-induced acute cardiovascular injury

Infection-induced cardiovascular damage is the primary pathological mechanism underlying septic cardiac dysfunction. This condition affects the majority of patients in intensive care unit and has an unfavorable prognosis due to the lack of effective therapies available. Vascular cell adhesion molecule-1 (VCAM-1) plays a vital role in coordinating the inflammatory response and recruitment of leukocytes in cardiac tissue, making it a potential target for developing novel therapies. MicroRNA-126 (miR-126) has been shown to downregulate VCAM-1 expression in endothelial cells, reducing leukocyte adhesion and exerting anti-inflammatory effects. Therefore, this work described a polysialic acid (PSA) modified ROS-responsive nanosystem to targeted co-delivery 1,8-Cineole and miR-126 for mitigating septic cardiac dysfunction. The nanosystem consists of 1,8-Cineole nanoemulsion (CNE) conjugated with PEI/miR126 complex by a ROS-sensitive linker, with PSA on its surface to facilitate targeted delivery via specific interactions with selectins on endothelial cells. CNE has demonstrated protective effects against inflammation in the cardiovascular system and synergistic anti-inflammatory effects when combined with miR-126. The targeted nanosystem successfully delivered miR-126 and 1,8-Cineole to the injured heart tissues and vessels, reducing inflammatory responses and improving cardiac function. In summary, this work provides a promising therapy for alleviating the inflammatory response in sepsis while boosting cardiovascular protection.

Encapsulation of Mentha aquatica methanol extract in alginate hydrogel promotes wound healing in a murine model of Pseudomonas aeruginosa burn infection

Burn injuries are the fourth most prevalent devastating form of trauma worldwide. Among the most extensively explored materials, composite dressings with alginate loaded with herbal extract can be mentioned. This research aimed to develop a sodium alginate (SA)-based hydrogel encapsulated with Mentha aquatica (MA) methanol extract and investigate its therapeutic efficacy in the infected burn mouse model. SEM, FTIR, in vitro extract release, HPLC, mechanical test, contact angle, swelling, degradability, and temperature response properties were used to analyze the hydrogel scaffold's physicochemical structure. Additionally, the antibacterial activity and MIC level of the extract, cell cytotoxicity, and macroscopic and microscopic analysis of the wound healing process were done using Masson's trichrome and hematoxylin-eosin staining. The physicochemical properties of the SA hydrogel encapsulated with MA extract were verified. The lowest inhibitory dose of the extract was determined to be 12.5 mg/ml. Application of SA/MA hydrogel to localized wounds of deep third-degree burns demonstrated faster tissue regeneration, collagen recovery, and eradication of bacterial infection. This research focused on the design and the preparation of a novel and effective biomaterials-based medical product, which has the potential to rehabilitate infected and injured skin tissue; therefore, it can be a promising candidate for wound dressing applications.

Anti-aging based on stem cell therapy: A scoping review.

Stem cells are present in the tissues and organs and remain in a quiescent and undifferentiated state until it is physiologically necessary to produce new descendant cells. Due to their multipotency property, mesenchymal stem cells have attracted considerable attention worldwide due to their immunomodulation and therapeutic function in tissue regeneration. Stem cells secrete components such as paracrine factors, extracellular vesicles, and exosomes which have been shown to have anti-inflammatory, anti-aging, reconstruction and wound healing potentials in many in vitro and in vivo models. The pluripotency and immunomodulatory features of stem cells could potentially be an effective tool in cell therapy and tissue repair. Aging affects the capacity for self-renewal and differentiation of stem cells, decreasing the potential for regeneration and the loss of optimal functions in organisms over time. Current progress in the field of cellular therapy and regenerative medicine has facilitated the evolution of particular guidelines and quality control approaches, which eventually lead to clinical trials. Cell therapy could potentially be one of the most promising therapies to control aging due to the fact that single stem cell transplantation can regenerate or substitute the injured tissue. To understand the involvement of stem cells not only in tissue maintenance and disease but also in the control of aging it is important to know and identify their properties, functions, and regulation in vivo, which are addressed in this review.

Engineered Tools to Advance Cell Transplantation in the Nervous System Towards a Clinical Reality

Abstract Purpose of the Review The goal of this review is to highlight engineered tools for overcoming challenges in cell survival and engraftment for tissue regeneration and mitigation of neuropathic pain following cell transplantation for neural applications. Recent Findings There is a growing body of evidence supporting the safety of cell transplantation for the treatment of injuries to the brain, spinal cord, and peripheral nerves. However, the efficacy of these cell therapies is inconclusive, and the path forward remains unclear due to a lack of evidence of transplant survival and engraftment. Engineered biomaterials offer promising pre-clinical evidence of enhanced survival and engraftment of cells transplanted within the nervous system. Biomaterials have been used alone or in combination with drug and gene delivery to direct cell transplant outcomes and represent a future direction for clinical evaluation given pre-clinical survival rates that may eliminate reliance on systemic immunosuppression. Summary Biomaterial approaches under pre-clinical evaluation can support cell survival, localize cells in the injured tissue where they are needed, and enable tissue engraftment, yet have not advanced towards the clinic. Existing biomaterials provide passive support of survival during delivery and/or place a premium on supporting cell engraftment, but active remediation of tissue-local inflammation that inhibits transplant survival and leads to neuropathic pain has seen very little advancement in recent years. Combinatorial approaches capable of addressing challenges in both survival and engraftment of cell transplants in the nervous system represent an area for significant growth in the coming years.

Cyclic stretch enhances neutrophil extracellular trap formation

BackgroundNeutrophils, the most abundant leukocytes circulating in blood, contribute to host defense and play a significant role in chronic inflammatory disorders. They can release their DNA in the form of extracellular traps (NETs), which serve as scaffolds for capturing bacteria and various blood cells. However, uncontrolled formation of NETs (NETosis) can lead to excessive activation of coagulation pathways and thrombosis. Once neutrophils are migrated to infected or injured tissues, they become exposed to mechanical forces from their surrounding environment. However, the impact of transient changes in tissue mechanics due to the natural process of aging, infection, tissue injury, and cancer on neutrophils remains unknown. To address this gap, we explored the interactive effects of changes in substrate stiffness and cyclic stretch on NETosis. Primary neutrophils were cultured on a silicon-based substrate with stiffness levels of 30 and 300 kPa for at least 3 h under static conditions or cyclic stretch levels of 5% and 10%, mirroring the biomechanics of aged and young arteries.ResultsUsing this approach, we found that neutrophils are sensitive to cyclic stretch and that increases in stretch intensity and substrate stiffness enhance nuclei decondensation and histone H3 citrullination (CitH3). In addition, stretch intensity and substrate stiffness promote the response of neutrophils to the NET-inducing agents phorbol 12-myristate 13-acetate (PMA), adenosine triphosphate (ATP), and lipopolysaccharides (LPS). Stretch-induced activation of neutrophils was dependent on calpain activity, the phosphatidylinositol 3-kinase (PI3K)/focal adhesion kinase (FAK) signalling and actin polymerization.ConclusionsIn summary, these results demonstrate that the mechanical forces originating from the surrounding tissue influence NETosis, an important neutrophil function, and thus identify a potential novel therapeutic target.

Biosponge-Encased Placental Stem Cells for Volumetric Muscle Loss Repair.

Objective: Volumetric muscle loss (VML) leads to permanent muscle mass and functional impairments. While mesenchymal stromal cells (MSCs) and their secreted factors can aid muscle regeneration, MSCs exhibit limited persistence in injured tissue post-transplantation. Human placental-derived stem cells (hPDSCs), sharing surface markers with MSCs, demonstrate superior regenerative potential due to their fetal origin. Previously, a biosponge (BS) scaffold was shown to augment muscle regeneration post-VML. This study aims to coapply BS therapy and hPDSCs to further enhance muscle recovery following VML. Approach: A VML defect was created by removing ∼20% of the tibialis anterior muscle mass in male Lewis rats. Injured muscles were either left untreated or treated with BS or BS-encapsulated hPDSCs cultured under normoxic or hypoxic conditions. On day 28 postinjury, peak isometric torque was measured, and the muscle was harvested for analysis. Results: BS encapsulated hPDSCs subjected to hypoxic preconditioning persisted in larger quantities and enhanced muscle mass at day 28 postinjury. BS encapsulated hPDSCs cultured under normoxic or hypoxic conditions increased small myofibers (<500 µm2) percentage, MyoD protein expression, and both pro- and anti-inflammatory macrophage marker expression. BS encapsulated hPDSCs also reduced fibrosis and BS remodeling rate. Innovation: This study is the first to examine the therapeutic effects of hPDSCs in a rat VML model. A BS carrier and hypoxic preconditioning were investigated to mitigate low cell survival postimplantation. Conclusion: hPDSCs augment the regenerative effect of BS. Combining hPDSCs and BS emerges as a promising strategy worthy of further investigation.