BACKGROUND:Adhesion formation following flexor tendon repair remains a significant clinical challenge, often necessitating reoperation and leading to suboptimal outcomes. Current adhesion barrier technologies have limited efficacy and usability. METHODS:A flowable extracellular matrix (ECM) hydrogel and ECM mesh were evaluated in a preclinical rabbit model of flexor tendon repair. Range of motion (ROM), adhesion scoring, and rupture strength were measured. Safety and overapplication effects were assessed in cadaveric tendon models. Histologic analysis evaluated inflammation. RESULTS:The ECM hydrogel and mesh reduced adhesions and improved ROM compared to saline controls. ROM in treated tendons ranged from 70.4°±17.7° (3:1 Gel) to 69.8°±8.3° (1:1 Gel), significantly higher than controls (50.7°±17.7°; p<0.05). Adhesion scores improved across treated groups, with 1:1 Gel achieving the best results (5.2±1.8 vs. control 8.0±1.5; p<0.05). Histology suggested reduced sustained inflammation in treated groups. No impact on rupture strength was observed, confirming mechanical safety. CONCLUSIONS:Flowable ECM hydrogel and ECM mesh significantly reduce adhesions and preserve tendon mechanics after flexor tendon repair. The hydrogel's flowable form offers superior ease of application, addressing unmet clinical needs.

Current clinical treatment options for traumatic brain injury (TBI) to limit permanent tissue damage and secondary injury remain inadequate. Intraparenchymal transplantation of neural stem cells is a potentially powerful therapy for TBI, acting through replacement and/or protection of damaged cells. This approach could be augmented by entrapping the stem cells within a pro-regenerative hydrogel, designed to both retain the therapeutic cells at the transplant site and modulate the inflammatory response. This study reports a decellularized extracellular matrix hydrogel derived from porcine dura for this purpose and the assessment of its efficacy in vitro and in vivo. In vitro, the dural ECM hydrogel ameliorated oxidative stress in hypoxic astrocytes and influenced collagen remodeling in fibroblast-derived matrices. Proteomic characterization revealed a composition of 559 proteins within the dural ECM, alongside matrix-bound vesicles that were demonstrated to be distinct from traditional cell-derived exosomes. In vivo, mice subjected to a controlled cortical impact traumatic brain injury displayed improved motor recovery when treated with the hydrogel alone, neural stem cells in suspension, or their combination. This novel biomaterial shows promise as a new therapy for TBI treatment, both independently and as a vehicle for cell delivery.

Tissue trauma initiates inflammation that can lead to fibrotic complications such as postoperative peritoneal adhesions, which contribute to chronic pain, infertility, and bowel obstruction. Despite their prevalence and impact, effective interventions to prevent adhesion formation remain limited. In this study, we evaluated a sprayable extracellular matrix (ECM) hydrogel as a barrier to protect healing tissues and reduce adhesion formation after abdominal surgery. In both mouse and rabbit models of colorectal and gynecologic procedures, ECM hydrogel application resulted in a substantial reduction in adhesion severity. Mechanistic studies demonstrated that the hydrogel promotes preservation or restoration of the mesothelial lining while modulating early local inflammation. Treated tissues exhibited reduced expression of inflammatory cytokines, including IL-1β, and maintained an intact mesothelial surface with fewer activated myofibroblasts compared with synthetic hydrogel and controls. Immunohistochemical analysis, transcriptomic profiling of mesothelial cells, and in vitro mechanical stretch experiments revealed that the ECM hydrogel mitigates mesothelial-to-mesenchymal transition. These findings suggest that the hydrogel not only provides a physical barrier but also serves as a biological modulator, shielding tissue from mechanical and inflammatory cues that drive adhesion formation. Overall, this study identifies a dual-function, biologically active ECM hydrogel capable of protecting healing tissues and reducing adhesion development in preclinical surgical models. These results support the potential of ECM hydrogel as a clinically translatable, biocompatible strategy for improving postsurgical healing outcomes and reducing adhesion-related complications.

EDITORIAL article Front. Pharmacol., 06 September 2022Sec. Inflammation Pharmacology Volume 13 - 2022 | https://doi.org/10.3389/fphar.2022.1008955

Postoperative adhesions are scar tissue that form between internal organs after surgery, leading to devastating life-long complications. Current adhesion barriers used clinically are solid sheets which can only be applied in open surgeries through large incisions. We have developed a material which can be applied as a liquid in minimally invasive surgeries which transitions into a solid thin film barrier upon contact with warm tissue. However, to be effective, it must be sprayed, and spraying a viscous liquid consistently is challenging. We proposed using a gas dispersant to facilitate aerosolization. In this study, we compared a commercially available nozzle without gas dispersant to a custom 3D printed nozzle with gas dispersant. For comparison, we measured both spray pattern and stiffness of the resulting gel. We found that when sprayed with gas dispersant, the spray pattern covered a larger area, and the resulting gel was stiffer than when sprayed without gas dispersant.

Zebrafish embryos provide a unique opportunity to visualize complex biological processes, yet conventional imaging modalities are unable to access intricate biomolecular information without compromising the integrity of the embryos. Here, we report the use of confocal Raman spectroscopic imaging for the visualization and multivariate analysis of biomolecular information extracted from unlabeled zebrafish embryos. We outline broad applications of this method in: (i) visualizing the biomolecular distribution of whole embryos in three dimensions, (ii) resolving anatomical features at subcellular spatial resolution, (iii) biomolecular profiling and discrimination of wild type and ΔRD1 mutant Mycobacterium marinum strains in a zebrafish embryo model of tuberculosis and (iv) in vivo temporal monitoring of the wound response in living zebrafish embryos. Overall, this study demonstrates the application of confocal Raman spectroscopic imaging for the comparative bimolecular analysis of fully intact and living zebrafish embryos.

The past few decades have produced a large number of proof-of-concept studies in regenerative medicine. However, the route to clinical adoption is fraught with technical and translational obstacles that frequently consign promising academic solutions to the so-called "valley of death." Here, we present a proposed blueprint for translational regenerative medicine. We offer principles to help guide the selection of cells and materials, present key in vivo imaging modalities, and argue that the host immune response should be considered throughout design and development. Last, we suggest a pathway to navigate the often complex regulatory and manufacturing landscape of translational regenerative medicine.

Research raw data supporting Hogset et al., "In vivo biomolecular imaging of zebrafish embryos using confocal Raman spectroscopy", 2020, Nature Communications.

Uncontrolled inflammation is a major pathological factor underlying a range of diseases including autoimmune conditions, cardiovascular disease, and cancer. Improving localized delivery of immunosuppressive drugs to inflamed tissue in a non-invasive manner offers significant promise to reduce severe side effects caused by systemic administration. Here, a neutrophil-mediated delivery system able to transport drug-loaded nanocarriers to inflamed tissue by exploiting the inherent ability of neutrophils to migrate to inflammatory tissue is reported. This hybrid system (neutrophils loaded with liposomes ex vivo) efficiently migrates in vitro following an inflammatory chemokine gradient. Furthermore, the triggered release of loaded liposomes and reuptake by target macrophages is studied. The migratory behavior of liposome-loaded neutrophils is confirmed in vivo by demonstrating the delivery of drug-loaded liposomes to an inflamed skeletal muscle in mice. A single low-dose injection of the hybrid system locally reduces inflammatory cytokine levels. Biodistribution of liposome-loaded neutrophils in a human-disease-relevant myocardial ischemia reperfusion injury mouse model after i.v. injection confirms the ability of injected neutrophils to carry loaded liposomes to inflammation sites. This strategy shows the potential of nanocarrier-loaded neutrophils as a universal platform to deliver anti-inflammatory drugs to promote tissue regeneration in inflammatory diseases.

All vertebrates possess mechanisms to restore damaged tissues with outcomes ranging from regeneration to scarring. Unfortunately, the mammalian response to tissue injury most often culminates in scar formation. Accounting for nearly 45% of deaths in the developed world, fibrosis is a process that stands diametrically opposed to functional tissue regeneration. Strategies to improve wound healing outcomes therefore require methods to limit fibrosis. Wound healing is guided by precise spatiotemporal deposition and remodelling of the extracellular matrix (ECM). The ECM, comprising the non-cellular component of tissues, is a signalling depot that is differentially regulated in scarring and regenerative healing. This Review focuses on the importance of the native matrix components during mammalian wound healing alongside a comparison to scar-free healing and then presents an overview of matrix-based strategies that attempt to exploit the role of the ECM to improve wound healing outcomes.

Extracellular vesicles (EVs) have recently gained significant attention as important mediators of intercellular communication, potential drug carriers, and disease biomarkers. These natural cell-derived nanoparticles are postulated to be biocompatible, stable under physiological conditions, and to show reduced immunogenicity as compared to other synthetic nanoparticles. Although initial clinical trials are ongoing, the use of EVs for therapeutic applications may be limited due to undesired off-target activity and potential dilution effects upon systemic administration which may affect their ability to reach their target tissues. To fully exploit their therapeutic potential, EVs are embedded into implantable biomaterials designed to achieve local delivery of therapeutics taking advantage of enzyme prodrug therapy (EPT). In this first application of EVs for an EPT approach, EVs are used as smart carriers for stabilizing enzymes in a hydrogel for local controlled conversion of benign prodrugs to active antiinflammatory compounds. It is shown that the natural EVs' antiinflammatory potential is comparable or superior to synthetic carriers, in particular upon repeated long-term incubations and in different macrophage models of inflammation. Moreover, density-dependent color scanning electron microscopy imaging of EVs in a hydrogel is presented herein, an impactful tool for further understanding EVs in biological settings.

Extracellular matrix (ECM) hydrogels represent a growing subset of injectable biomaterials for tissue engineering and regenerative medicine applications. Whilst two-dimensional scaffolds composed of ECM have been in routine clinical use for decades, the clinical translation of ECM hydrogels has been limited to date. Evaluation of the stability and function of ECM hydrogels after sterilization and storage is necessary to advance therapeutic use of these materials. In the present study, a new form of ECM material, specifically, ‘lyophilized digest’ was introduced to mitigate potential storage issues and investigate the effects of sterilization. Both ECM powders and lyophilized digests were subjected to sterilization by gamma irradiation, electron beam irradiation, ethylene oxide and supercritical carbon dioxide prior to hydrogel formation. The efficacy and effect of sterilization upon mechanical properties, macrophage response and stem cell chemotaxis was determined. Independent of the form of ECM exposed to sterilization, irradiation at 30 kGy altered ECM properties and inhibited subsequent gelation. Interestingly, the form of the ECM exposed to sterilization had a dramatic impact upon hydrogel rheological properties. Hydrogels formed from sterilized powders had reduced mechanical properties whereas hydrogels formed from sterilized lyophilized digest had mechanical properties equivalent to the non-sterilized control. Sterilization did not affect the bioactivity of ECM hydrogels as measured by stem cell chemotaxis and macrophage response. Together these data provide practical insight required for the translation of ECM based hydrogels.

In article number 1706616, Molly M. Stevens and co-workers present the incorporation of extracellular vesicles into biocompatible poly(vinyl alcohol)-based hydrogels to advance the concept of enzyme-prodrug therapy. Hydrogels are imaged by density-dependent color scanning electron microscopy taking advantage of the backscattered signal of the labeled vesicles. The vesicles appear as bright red dots within the hydrogel matrix, indicating densitydependent microscopy as a powerful tool for the spatial analysis of vesicle distribution and localization in 3D.

Biologic scaffolds are derived from mammalian tissues, which must be decellularized to remove cellular antigens that would otherwise incite an adverse immune response. Although widely used clinically, the optimum balance between cell removal and the disruption of matrix architecture and surface ligand landscape remains a considerable challenge. Here we describe the use of time of flight secondary ion mass spectroscopy (ToF-SIMS) to provide sensitive, molecular specific, localized analysis of detergent decellularized biologic scaffolds. We detected residual detergent fragments, specifically from Triton X-100, sodium deoxycholate and sodium dodecyl sulphate (SDS) in decellularized scaffolds; increased SDS concentrations from 0.1% to 1.0% increased both the intensity of SDS fragments and adverse cell outcomes. We also identified cellular remnants, by detecting phosphate and phosphocholine ions in PAA and CHAPS decellularized scaffolds. The present study demonstrates ToF-SIMS is not only a powerful tool for characterization of biologic scaffold surface molecular functionality, but also enables sensitive assessment of decellularization efficacy.Statement of SignificanceWe report here on the use of a highly sensitive analytical technique, time of flight secondary ion mass spectroscopy (ToF-SIMS) to characterize detergent decellularized scaffolds. ToF-SIMS detected cellular remnants and residual detergent fragments; increased intensity of the detergent fragments correlated with adverse cell matrix interactions. This study demonstrates the importance of maintaining a balance between cell removal and detergent disruption of matrix architecture and matrix surface ligand landscape. This study also demonstrates the power of ToF-SIMS for the characterization of decellularized scaffolds and capability for assessment of decellularization efficacy. Future use of biologic scaffolds in clinical tissue reconstruction will benefit from the fundamental results described in this work. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The synthesis and secretion of components that constitute the extracellular matrix (ECM) by resident cell types occur at the earliest stages of embryonic development, and continue throughout life in both healthy and diseased physiological states. The ECM consists of a complex mixture of insoluble and soluble functional components that are arranged in a tissue-specific 3D ultrastructure, and it regulates numerous biological processes, including angiogenesis, innervation and stem cell differentiation. Owing to its composition and influence on embryonic development, as well as cellular and organ homeostasis, the ECM is an ideal therapeutic substrate for the repair of damaged or diseased tissues. Biologic scaffold materials that are composed of ECM have been used in various surgical and tissue-engineering applications. The gastrointestinal (GI) tract presents distinct challenges, such as diverse pH conditions and the requirement for motility and nutrient absorption. Despite these challenges, the use of homologous and heterologous ECM bioscaffolds for the focal or segmental reconstruction and regeneration of GI tissue has shown promise in early preclinical and clinical studies. This Review discusses the importance of tissue-specific ECM bioscaffolds and highlights the major advances that have been made in regenerative medicine strategies for the reconstruction of functional GI tissues.

BACKGROUND AND AIMS:Despite advances in therapeutic options, more than half of all patients with ulcerative colitis [UC] do not achieve long-term remission, many require colectomy, and the disease still has a marked negative impact on quality of life. Extracellular matrix [ECM] bioscaffolds facilitate the functional repair of many soft tissues by mechanisms that include mitigation of pro-inflammatory macrophage phenotype and mobilization of endogenous stem/progenitor cells. The aim of the present study was to determine if an ECM hydrogel therapy could influence outcomes in an inducible rodent model of UC.METHODS:The dextran sodium sulphate [DSS]-colitis model was used in male Sprague Dawley rats. Animals were treated via enema with an ECM hydrogel and the severity of colitis was determined by clinical and histological criteria. Lamina propria cells were isolated and the production of inflammatory mediators was quantified. Mucosal permeability was assessed in vivo by administering TRITC-dextran and in vitro using transepithelial electrical resistance [TEER].RESULTS:ECM hydrogel therapy accelerated healing and improved outcome. The hydrogel was adhesive to colonic tissue, which allowed for targeted delivery of the therapy, and resulted in a reduction in clinical and histological signs of disease. ECM hydrogel facilitated functional improvement of colonic epithelial barrier function and the resolution of the pro-inflammatory state of tissue macrophages.CONCLUSIONS:The present study shows that a non-surgical and non-pharmacological ECM-based therapy can abate DSS-colitis not by immunosuppression but by promoting phenotypic change in local macrophage phenotype and rapid replacement of the colonic mucosal barrier.

Gastrointestinal pathologies, injuries, and defects affect millions of individuals each year. While there are diverse treatment options for these individuals, no ideal solution exists. The repair or replacement of gastrointestinal tissue, therefore, represents a large unmet clinical need. Biomaterials derived from extracellular matrix (ECM) scaffolds have been effectively used to repair or replace numerous tissues throughout the body in both preclinical and clinical studies. Such scaffolds are prepared from decellularized tissues, and the biochemical, structural, and biologic properties vary depending upon the source tissue from which the ECM is derived. Given the potential benefit of a sitespecific ECM scaffold for some applications, the objective of this study was to prepare, characterize, and determine the in vitro and in vivo cell response to ECM derived from porcine colon. Results of this study show that porcine colon can be effectively decellularized while retaining biochemical and structural constituents of the source tissue. Two forms of colonic ECM, scaffold and hydrogel, were shown to be cell friendly and facilitate the polarization of macrophages toward an M2 phenotype both in vitro and in vivo. (C) 2015 Wiley Periodicals, Inc.

Precancerous or cancerous lesions of the gastrointestinal tract often require surgical resection via endomucosal resection. Although excision of the colonic mucosa is an effective cancer treatment, removal of large lesions is associated with high morbidity and complications including bleeding, perforation, fistula formation, and/or stricture, contributing to high clinical and economic costs and negatively impacting patient quality of life. The present study investigates the use of a biologic scaffold derived from extracellular matrix (ECM) to promote restoration of the colonic mucosa following short segment mucosal resection. Six healthy dogs were assigned to ECM-treated (tubular ECM scaffold) and mucosectomy only control groups following transanal full circumferential mucosal resection (4 cm in length). The temporal remodeling response was monitored using colonoscopy and biopsy collection. Animals were sacrificed at 6 and 10 wk, and explants were stained with hematoxylin and eosin (H&E), Alcian blue, and proliferating cell nuclear antigen (PCNA) to determine the temporal remodeling response. Both control animals developed stricture and bowel obstruction with no signs of neomucosal coverage after resection. ECM-treated animals showed an early mononuclear cell infiltrate (2 weeks post-surgery) which progressed to columnar epithelium and complex crypt structures nearly indistinguishable from normal colonic architecture by 6 weeks after surgery. ECM scaffold treatment restored colonic mucosa with appropriately located PCNA+ cells and goblet cells. The study shows that ECM scaffolds may represent a viable clinical option to prevent complications associated with endomucosal resection of cancerous lesions in the colon.

Biologic scaffolds composed of extracellular matrix are commonly used in a variety of surgical procedures. The Food and Drug Administration typically regulates biologic scaffolds as medical devices, thus requiring terminal sterilization prior to clinical use. However, to date, no consensus exists for the most effective yet minimally destructive sterilization protocol for biologic scaffold materials. The objective of the present study was to characterize the effect of ethylene oxide, gamma irradiation and electron beam (e-beam) irradiation on the material properties and the elicited in vivo remodeling response of a porcine dermal biologic scaffold. Outcome measures included biochemical, structural, and mechanical properties as well as cytocompatibility in vitro. In vivo evaluation utilized a rodent model to examine the host response to the materials following 7, 14, and 35 days. The host response to each experimental group was determined by quantitative histologic methods and by immunolabeling for macrophage polarization (M1/M2). In vitro results show that increasing irradiation dosage resulted in a dose dependent decrease in mechanical properties compared to untreated controls. Ethylene oxide-treated porcine dermal ECM resulted in decreased DNA content, extractable total protein, and bFGF content compared to untreated controls. All ETO treated, gamma irradiated, and e-beam irradiated samples had similar cytocompatibility scores in vitro. However, in vivo results showed that increasing dosages of e-beam and gamma irradiation elicited an increased rate of degradation of the biologic scaffold material following 35 days.Statement of SignificanceThe FDA typically regulates biologic scaffolds derived from mammalian tissues as medical devices, thus requiring terminal sterilization prior to clinical use. However, there is little data and no consensus for the most effective yet minimally destructive sterilization protocol for such materials. The present study characterized the effect of common sterilization methods: ethylene oxide, gamma irradiation and electron beam irradiation on the material properties and the elicited in vivo remodeling response of a porcine dermal biologic scaffold. The results of the study will aid in the meaningful selection of sterilization methods for biologic scaffold materials. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.