ECM hydrogel coating mitigates the chronic inflammatory response to polypropylene mesh

Advances, challenges, and future directions in the clinical translation of ECM biomaterials for regenerative medicine applications

Extracellular Matrix (ECM) scaffolds and biomaterials have been widely used for decades across a variety of diverse clinical applications and have been implanted in millions of patients worldwide. ECM-based biomaterials have been especially successful in soft tissue repair applications but their utility in other clinical applications such as for regeneration of bone or neural tissue is less well understood. The beneficial healing outcome with the use of ECM biomaterials is the result of their biocompatibility, their biophysical properties and their ability to modify cell behavior after injury. As a consequence of successful clinical outcomes, there has been motivation for the development of next-generation formulations of ECM materials ranging from hydrogels, bioinks, powders, to whole organ or tissue scaffolds. The continued development of novel ECM formulations as well as active research interest in these materials ensures a wealth of possibilities for future clinical translation and innovation in regenerative medicine. The clinical translation of next generation formulations ECM scaffolds faces predictable challenges such as manufacturing, manageable regulatory pathways, surgical implantation, and the cost required to address these challenges. The current status of ECM-based biomaterials, including clinical translation, novel formulations and therapies currently under development, and the challenges that limit clinical translation of ECM biomaterials are reviewed herein.

Bioactive microgel-coated electrospun membrane with cell-instructive interfaces and topology for abdominal wall defect repair

Current mesh materials used for the clinical treatment of abdominal defects struggle to balance mechanical properties and bioactivity to support tissue remodeling. Therefore, a bioactive microgel-coated electrospinning membrane was designed with the superiority of cell-instructive topology in guiding cell behavior and function for abdominal wall defect reconstruction. The electrostatic spinning technique was employed to prepare a bioabsorbable PLCL fiber membrane with an effective mechanical support. Additionally, decellularized matrix (dECM)-derived bioactive microgels were further coated on the fiber membrane through co-precipitation with dopamine, which was expected to endow cell-instructive hydrophilic interfaces and topological morphologies for cell adhesion. Moreover, the introduction of the dECM into the microgel promoted the myogenic proliferation and differentiation of C2C12 cells. Subsequently, in vivo experiments using a rat abdominal wall defect model demonstrated that the bioactive microgel coating significantly contributed to the reconstruction of intact abdominal wall structures, highlighting its potential for clinical application in promoting the repair of soft tissue defects associated with abdominal wall damage. This study presented an effective mesh material for facilitating the reconstruction of abdominal wall defects and contributed novel design concepts for the surface modification of scaffolds with cell-instructive interfaces and topology.

Coatings for Permanent Meshes Used to Enhance Healing in Abdominal Hernia Repair: A Scoping Review

INTRODUCTION

Hernia meshes are used to reduce recurrence and pain rates, but the rates are still high. This could be improved with coatings of the mesh. This scoping review aimed to provide an overview of mesh coatings used to promote healing in abdominal hernia repair and to report beneficial and unbeneficial effects.

METHODS

We included human and animal studies with abdominal hernias that were repaired with non-commercially coated meshes. We searched Pubmed, Embase, Cochrane Central, LILACS, and CNKI without language constraints.

RESULTS

Of 2933 identified studies, 58 were included: six studies had a total of 408 humans and 52 studies had 2679 animals. The median follow-up was 12 months (range 1-156), and 95% of the hernias were incisional. There were 44 different coatings which included platelet-rich plasma, mesenchymal stem cells, growth factors, vitamin E, collagen-derived products, various polysaccharides, silk proteins, chitosan, gentamycin, doxycycline, nitrofurantoin, titanium, and diamond-like carbon. Mesenchymal stem cells and platelet-rich plasma were the most researched. Mesenchymal stem cells notably reduced inflammation and foreign body reactions but did not impact other healing metrics. In contrast, platelet-rich plasma positively influenced tissue ingrowth, collagen deposition, and neovascularization and had varying effects on inflammation and foreign body reactions.

CONCLUSION

We identified 44 different mesh coatings and they showed varying results. Mesenchymal stem cells and platelet-rich plasma were the most studied, with the latter showing considerable promise in improving biomechanical properties in hernia repair. Further investigations are needed to ascertain their definitive use in humans.

Gluteus Maximus Transfer for Irreparable Hip Abductor Deficiency: A Systematic Review and Meta-Analysis

BACKGROUND

Gluteus maximus tendon transfer has recently been described as a treatment option for irreparable abductor tendon tears. The purpose of this study was to systematically review outcomes following gluteus maximus tendon transfer for hip abductor deficiency.

METHODS

The published literature was queried for outcomes following gluteus maximus transfer in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Outcomes of interest included preoperative and postoperative functional scores, resolution of pain and gait abnormalities, postoperative rehabilitation protocols, surgical complications, reoperation rates, and postoperative magnetic resonance imaging. In total, 10 studies with a total of 125 patients (76% women) with a mean age of 67 years (range, 30 to 87) were identified for inclusion.

RESULTS

Modified Harris Hip Score (+30.1 ± 6.6 [95% confidence interval: +15.5 to +46.5]) and Visual Analog Scale for pain (-4.1 ± 1.1 [95% confidence interval: -7.1 to -1.0]) were improved following gluteus maximus transfer, compared to preoperative levels. No significant improvement was noted in abduction strength and 33% of patients demonstrated a residual Trendelenburg gait postoperatively. The overall complication rate was 5.6% (7 of 125), with a reoperation rate of 1.6% (2 of 125).

CONCLUSIONS

Gluteus maximus tendon transfer for abductor insufficiency has demonstrated reliable outcomes at 3 years, with improvement in hip function and pain. However, patients demonstrate modest improvements in abduction strength, and a significant subset will continue to demonstrate a Trendelenburg gait postoperatively.

Antibacterial and antioxidant bifunctional hydrogel based on hyaluronic acid complex MoS2-dithiothreitol nanozyme for treatment of infected wounds

Wound repair is a complex physiological process that often leads to bacterial infections, which significantly threaten human health. Therefore, developing wound-healing materials that promote healing and prevent bacterial infections is crucial. In this study, the coordination interaction between sulfhydryl groups on dithiothreitol (DTT) and MoS2 nanosheets is investigated to synthesize a MoS2-DTT nanozyme with photothermal properties and an improved free-radical scavenging ability. Double-bond-modified hyaluronic acid is used as a monomer and is cross-linked with a PF127-DA agent. PHMoD is prepared in coordination with MoS2-DTT as the functional component. This hydrogel exhibits antioxidant and antibacterial properties, attributed to the catalytic activity of catalase-like enzymes and photothermal effects. Under the near-infrared (NIR), it exhibits potent antibacterial effects against gram-positive (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli), achieving bactericidal rates of 99.76% and 99.42%, respectively. Furthermore, the hydrogel exhibits remarkable reactive oxygen species scavenging and antioxidant capabilities, effectively countering oxidative stress in L929 cells. Remarkably, in an animal model, wounds treated with the PHMoD(2.0) and NIR laser heal the fastest, sealing completely within 10 days. These results indicate the unique biocompatibility and bifunctionality of the PHMoD, which make it a promising material for wound-healing applications.

Releasable, Immune-Instructive, Bioinspired Multilayer Coating Resists Implant-Induced Fibrosis while Accelerating Tissue Repair

Implantable biomaterials trigger foreign body reactions (FBRs), which reduces the functional life of medical devices and prevents effective tissue regeneration. Although existing therapeutic approaches can circumvent collagen-rich fibrotic encapsulation secondary to FBRs, they disrupt native tissue repair. Herein, a new surface engineering strategy in which an apoptotic-mimetic, immunomodulatory, phosphatidylserine liposome (PSL) is released from an implant coating to induce the formation of a macrophage phenotype that mitigates FBRs and improves tissue healing is described. PSL-multilayers constructed on implant surfaces via the layer-by-layer method release PSLs over a 1-month period. In rat muscles, poly(etheretherketone) (PEEK), a nondegradable polymer implant model, induces FBRs with dense fibrotic scarring under an aberrant cellular profile that recruits high levels of inflammatory infiltrates, foreign body giant cells (FBGCs), scar-forming myofibroblasts, and inflammatory M1-like macrophages but negligible amounts of anti-inflammatory M2-like phenotypes. However, the PSL-multilayer coating markedly diminishes these detrimental signatures by shifting the macrophage phenotype. Unlike other therapeutics, PSL-multilayered coatings also stimulate muscle regeneration. This study demonstrates that PSL-multilayered coatings are effective in eliminating FBRs and promoting regeneration, hence offering potent and broad applications for implantable biomaterials.

Cytotoxicity studies and antibacterial modification of poly(ethylene 2,5-furandicarboxylate) nonwoven

Novel poly(ethylene 2,5-furandicarboxylate) PEF nonwovens were produced by solution electrospinning and further modification. To improve the wettability of the hydrophobic nonwovens with water, they were treated with sodium hydroxide. Cytotoxicity tests carried out with human keratinocytes confirmed that the nonwovens did not have a toxic effect on healthy cells. The hydrophilicity of the sodium hydroxide treated nonwoven favored the adherence of the cells and their growth. In turn, the two-step modification of the nonwovens by reactions with (3-mercaptopropyl)methyldimethoxysilane and silver nitrate permitted to deposit silver particles on the fiber surfaces. The bacteria growth inhibition zones around the tested specimens were observed evidencing their antibacterial activity against Escherichia coli and Staphylococcus aureus.

Hierarchically patterned triple-layered gelatin-based electrospun membrane functionalized by cell-specific extracellular matrix for periodontal regeneration

OBJECTIVES

Regenerating the periodontium poses a critical challenge in oral medicine. To repair various periodontal defects, it is necessary to adopt a bio-scaffold that provides both the architecture and bioactive cues for local stem cells to migrate, reside, proliferate, and differentiate. The objective of this study is to combine a cell-specific decellularized extracellular matrix (ECM) and a biomimetic electrospinning scaffold to regenerate severely destructed periodontium.

METHODS

SEM, water contact angle (WCA), live/dead staining, swelling ratio, tensile test and immune-fluorescent staining were used to define the suitable topography for certain dental stem cells seeding and culturing. Transwell assay, CCK-8, Alizarin Red staining and PCR immune-fluorescent staining were used to determine ideal cell-specific ECM for PDLSCs/BMSCs migration, viability, and oriented differentiation. A biodegradable triple-layered electrospun scaffold (TLS) was fabricated by electrospinning with aligned fibers on both surfaces and a polyporous structure in the middle. The morphology and inter-porous structure of the TLS were characterized by SEM and mercury intrusion porosimetry (MIP). The surface of the TLS was functionalized with cell-specific ECM (Bi-ECM-TLS) through decellularization of the cell sheets cultured on the scaffold. The regenerative outcome of Bi-ECM-TLS was assessed by an in-situ rat periodontal defect model. Micro-CT, HE-staining, Masson's trichome staining, Sirius Red staining and Immunofluorescent staining were used for histological analysis.

RESULTS

Aligned Gelatin/PCL fibrous membrane (GPA) was most effective for both PDLSCs and BMSCs in culture with WCA around 50 degrees and better mechanical strength than the rest. MSCs favored the same type of ECM (cell-specific ECM), and their regenerative properties were effectively induced with better chemotaxis, proliferative and differentiating behaviors. TLS characterization showed that TLS possessed aligned-random-aligned structure and inter-porous structure. In a rat model of periodontal defects, the TLS functionalized by BMSC-specific ECM for bone regeneration and PDLSC-specific ECM demonstrated highest BV/TV ratio, best bone structure and ligament fiber orientation and blood vessel formation, suggesting optimal performance in regenerating both alveolar bone and periodontal ligaments over TLS, single-ECM loaded TLS and r-Bi-ECM-TLS.

SIGNIFICANCE

This study highlights the importance of combining a cell-specific decellularized ECM and a biomimetic electrospinning scaffold for targeted periodontal tissue regeneration, with potential implications for periodontal tissue engineering and improved patient outcomes.

Injectable polyisocyanide hydrogel as healing supplement for connective tissue regeneration in an abdominal wound model

In pelvic organ prolapse (POP) patients, the uterus, bladder and/or rectum descends into vagina due to weakened support tissues. High recurrence rates after POP surgery suggest an urgent need for improved surgical outcomes. Our aim is to promote connective tissue healing that results in stimulated tissue support functions by surgically applying a hydrogel functionalized with biological cues. We used known vaginal wound healing promoting factors (basic fibroblast growth factor, β-estradiol, adipose-derived stem cells) in the biomimetic and injectable polyisocyanide (PIC) hydrogel, which in itself induces regenerative vaginal fibroblast behavior. The regenerative capacity of injected PIC hydrogel, and the additional pro-regenerative effects of these bioactive factors was evaluated in abdominal wounds in rabbits. Assessment of connective tissue healing (tensile testing, histology, immunohistochemistry) revealed that injection with all PIC formulations resulted in a statistically significant stiffness and collagen increase over time, in contrast to sham. Histological evaluation indicated new tissue growth with moderate to mild immune activity at the hydrogel - tissue interface. The results suggest that PIC injection in an abdominal wound improves healing towards regaining load-bearing capacity, which encourages us to investigate application of the hydrogel in a more translational vaginal model for POP surgery in sheep.

In situ forming biomaterials as muscle void fillers for the provisional treatment of volumetric muscle loss injuries

Volumetric muscle loss (VML) represents a devastating extremity injury which leads to chronic functional deficits and disability and is unrecoverable through normal healing pathways. When left untreated, the VML pathophysiology creates many challenges towards successful treatment, such as altered residual muscle architecture, excessive fibrosis, and contracture(s). As such, innovative approaches and technologies are needed to prevent or reverse these adverse sequelae. Development of a rationally designed biomaterial technology which is intended to be acutely placed within a VML defect - i.e., to serve as a muscle void filler (MVF) by maintaining the VML defect - could address this clinical unmet need by preventing these adverse sequelae as well as enabling multi-staged treatment approaches. To that end, three biomaterials were evaluated for their ability to serve as a provisional MVF treatment intended to stabilize a VML defect in a rat model for an extended period (28 days): polyvinyl alcohol (PVA), hyaluronic acid and polyethylene glycol combination (HA + PEG), and silicone, a clinically used soft tissue void filler. HA + PEG biomaterial showed signs of deformation, while both PVA and silicone did not. There were no differences between treatment groups for their effects on adjacent muscle fiber count and size distribution. Not surprisingly, silicone elicited robust fibrotic response resulting in a fibrotic barrier with a large infiltration of macrophages, a response not seen with either the PVA or HA + PEG. Taken together, PVA was found to be the best material to be used as a provisional MVF for maintaining VML defect volume while minimizing adverse effects on the surrounding muscle.

Polypropylene composite mesh modified by polyurethane gel with ROS scavenging and anti-inflammatory effects for pelvic floor repair

Development of an inflammation modulating polypropylene (PP) mesh in pelvic floor repair is an urgent clinical need. This is because PP mesh for pelvic floor repair can cause a series of complications related to foreign body reactions (FBR) in postoperative period. Therefore, we successfully prepared PP composite mesh that can scavenge reactive oxygen species (ROS) and inhibit inflammation to moderate FBR by a simple method. First, a pregel layer was formed on PP mesh by dip coating. Among them, polyurethane with polythioketal (PTK) is an excellent ROS scavenger, and dopamine methacrylamide (DMA) improves the stability of the coating and synergistically scavenges ROS. Then, a composite mesh (optimal PU50-PP) was obtained by photopolymerization. The results showed that the polyurethane gel layer was able to scavenge more than 90% of free radicals and about 75% of intracellular ROS. In vitro, PU50-PP mesh significantly scavenged ROS and resisted macrophage adhesion. After implantation in the posterior vaginal wall of rats, PU50-PP eliminated 53% of ROS, inhibited inflammation (decreased IL-6, increased IL-10), and dramatically reduced collagen deposition by about 64%, compared to PP mesh. Thus, the composite PP mesh with ROS scavenging and anti-inflammatory properties provides a promising approach for mitigating FBR.

Abdominal wall hernia repair: from prosthetic meshes to smart materials

Hernia reconstruction is one of the most frequently practiced surgical procedures worldwide. Plastic surgery plays a pivotal role in reestablishing desired abdominal wall structure and function without the drawbacks traditionally associated with general surgery as excessive tension, postoperative pain, poor repair outcomes, and frequent recurrence. Surgical meshes have been the preferential choice for abdominal wall hernia repair to achieve the physical integrity and equivalent components of musculofascial layers. Despite the relevant progress in recent years, there are still unsolved challenges in surgical mesh design and complication settlement. This review provides a systemic summary of the hernia surgical mesh development deeply related to abdominal wall hernia pathology and classification. Commercial meshes, the first-generation prosthetic materials, and the most commonly used repair materials in the clinic are described in detail, addressing constrain side effects and rational strategies to establish characteristics of ideal hernia repair meshes. The engineered prosthetics are defined as a transit to the biomimetic smart hernia repair scaffolds with specific advantages and disadvantages, including hydrogel scaffolds, electrospinning membranes, and three-dimensional patches. Lastly, this review critically outlines the future research direction for successful hernia repair solutions by combing state-of-the-art techniques and materials.

Multifunctional and biodegradable methacrylated gelatin/Aloe vera nanofibers for endodontic disinfection and immunomodulation

Currently employed approaches and materials used for vital pulp therapies (VPTs) and regenerative endodontic procedures (REPs) lack the efficacy to predictably achieve successful outcomes due to their inability to achieve adequate disinfection and/or lack of desired immune modulatory effects. Natural polymers and medicinal herbs are biocompatible, biodegradable, and present several therapeutic benefits and immune-modulatory properties; thus, standing out as a clinically viable approach capable of establishing a conducive environment devoid of bacteria and inflammation to support continued root development, dentinal bridge formation, and dental pulp tissue regeneration. However, the low stability and poor mechanical properties of the natural compounds have limited their application as potential biomaterials for endodontic procedures. In this study, Aloe vera (AV), as a natural antimicrobial and anti-inflammatory agent, was incorporated into photocrosslinkable Gelatin methacrylate (GelMA) nanofibers with the purpose of developing a highly biocompatible biomaterial capable of eradicating endodontic infection and modulating inflammation. Stable GelMA/AV nanofibers with optimal properties were obtained at the ratio of (70:30) by electrospinning. In addition to the pronounced antibacterial effect against Enterococcus faecalis, the GelMA/AV (70:30) nanofibers also exhibited a sustained antibacterial activity over 14 days and significant biofilm reduction with minimal cytotoxicity, as well as anti-inflammatory properties and immunomodulatory effects favoring healing. Our results indicate that the novel GelMA/AV (70:30) nanofibers hold great potential as a biomaterial strategy for endodontic infection eradication and enhanced healing.

A Novel Bio-Adhesive Mesh System for Medical Implant Applications: In Vivo Assessment in a Rabbit Model

Injectable surgical sealants and adhesives, such as biologically derived fibrin gels and synthetic hydrogels, are widely used in medical products. While such products adequately adhere to blood proteins and tissue amines, they have poor adhesion with polymer biomaterials used in medical implants. To address these shortcomings, we developed a novel bio-adhesive mesh system utilizing the combined application of two patented technologies: a bifunctional poloxamine hydrogel adhesive and a surface modification technique that provides a poly-glycidyl methacrylate (PGMA) layer grafted with human serum albumin (HSA) to form a highly adhesive protein surface on polymer biomaterials. Our initial in vitro tests confirmed significantly improved adhesive strength for PGMA/HSA grafted polypropylene mesh fixed with the hydrogel adhesive compared to unmodified mesh. Toward the development of our bio-adhesive mesh system for abdominal hernia repair, we evaluated its surgical utility and in vivo performance in a rabbit model with retromuscular repair mimicking the totally extra-peritoneal surgical technique used in humans. We assessed mesh slippage/contraction using gross assessment and imaging, mesh fixation using tensile mechanical testing, and biocompatibility using histology. Compared to polypropylene mesh fixed with fibrin sealant, our bio-adhesive mesh system exhibited superior fixation without the gross bunching or distortion that was observed in the majority (80%) of the fibrin-fixed polypropylene mesh. This was evidenced by tissue integration within the bio-adhesive mesh pores after 42 days of implantation and adhesive strength sufficient to withstand the physiological forces expected in hernia repair applications. These results support the combined use of PGMA/HSA grafted polypropylene and bifunctional poloxamine hydrogel adhesive for medical implant applications.

Advances Focusing on the Application of Decellularized Extracellular Matrix in Periodontal Regeneration

The decellularized extracellular matrix (dECM) is capable of promoting stem cell proliferation, migration, adhesion, and differentiation. It is a promising biomaterial for application and clinical translation in the field of periodontal tissue engineering as it most effectively preserves the complex array of ECM components as they are in native tissue, providing ideal cues for regeneration and repair of damaged periodontal tissue. dECMs of different origins have different advantages and characteristics in promoting the regeneration of periodontal tissue. dECM can be used directly or dissolved in liquid for better flowability. Multiple ways were developed to improve the mechanical strength of dECM, such as functionalized scaffolds with cells that harvest scaffold-supported dECM through decellularization or crosslinked soluble dECM that can form injectable hydrogels for periodontal tissue repair. dECM has found recent success in many periodontal regeneration and repair therapies. This review focuses on the repairing effect of dECM in periodontal tissue engineering, with variations in cell/tissue sources, and specifically discusses the future trend of periodontal regeneration and the future role of soluble dECM in entire periodontal tissue regeneration.

Harnessing the synergy of perfusable muscle flap matrix and adipose-derived stem cells for prevascularization and macrophage polarization to reconstruct volumetric muscle loss

Muscle flaps must have a strong vascular network to support a large tissue volume and ensure successful engraftment. We developed porcine stomach musculofascial flap matrix (PDSF) comprising extracellular matrix (ECM) and intact vasculature. PDSF had a dominant vascular pedicle, microcirculatory vessels, a nerve network, well-retained 3-dimensional (3D) nanofibrous ECM structures, and no allo- or xenoantigenicity. In-depth proteomic analysis demonstrated that PDSF was composed of core matrisome proteins (e.g., collagens, glycoproteins, proteoglycans, and ECM regulators) that, as shown by Gene Ontology term enrichment analysis, are functionally related to musculofascial biological processes. Moreover, PDSF-human adipose-derived stem cell (hASC) synergy not only induced monocytes towards IL-10-producing M2 macrophage polarization through the enhancement of hASCs' paracrine effect but also promoted the proliferation and interconnection of both human skeletal muscle myoblasts (HSMMs) and human umbilical vein endothelial cells (HUVECs) in static triculture conditions. Furthermore, PDSF was successfully prevascularized through a dynamic perfusion coculture of hASCs and HUVECs, which integrated with PDSF and induced the maturation of vascular networks in vitro. In a xenotransplantation model, PDSF demonstrated myoconductive and immunomodulatory properties associated with the predominance of M2 macrophages and regulatory T cells. In a volumetric muscle loss (VML) model, prevascularized PDSF augmented neovascularization and constructive remodeling, which was characterized by the predominant infiltration of M2 macrophages and significant musculofascial tissue formation. These results indicate that hASCs' integration with PDSF enhances the cells' dual function in immunomodulation and angiogenesis. Owing in part to this PDSF-hASC synergy, our platform shows promise for vascularized muscle flap engineering for VML reconstruction.

Promotion of Wound Healing Using Nanoporous Silk Fibroin Sponges

Wound dressings are important for wound repair. The morphology of the biomaterials used in these dressings, and in particular, the pore structure affects tissue regeneration by facilitating attachment and proliferation of cells due to the hierarchical multiscale, water absorbance, and nutrient transport. In the present study, silk fibroin (SF) sponges with walls containing nanopores (SFNS) were prepared from SF nanoparticles generated during the autoclaving of SF solutions, followed by leaching the SF nanoparticles from the freeze-dried sponges of SF. The nano/microporous structure, biofluid absorbance, and porosity of the SF sponges with and without nanopores were characterized. In vitro cell proliferation, in vivo biocompatibility, and wound healing were evaluated with the sponges. The results demonstrated that SFNS had significantly increased porosity and water permeability, as well as cell attachment and proliferation when compared with SF sponges without the nanopores (SFS). Wound dressings were assessed in a rat skin wound model, and SFNS was superior to SFS in accelerating wound healing, supported by vascularization, deposition of collagen, and increased epidermal thickness over 21 days. Hence, such a dressing material with a hierarchical multiscale pore structure could promote cell migration, vascularization, and tissue regeneration independently without adding any growth factor, which would offer a new strategy to design and engineer better-performed wound dressing.

Silk fibroin bioscaffold from Bombyx mori and Antheraea assamensis elicits a distinct host response and macrophage activation paradigm in vivo and in vitro

Biomaterials composed of silk fibroin from both mulberry and non-mulberry silkworm varieties have been investigated for their utility in tissue engineering and drug delivery, but these studies have largely excluded any evaluation of host immune response. The present study compares the macrophage activation response towards mulberry (Bombyx mori, BM) and non-mulberry (Antheraea assamensis, AA) silk types, individually and as a blend (BA) in a partial thickness rat abdominal wall defect model and in vitro primary murine bone marrow-derived macrophage (BMDM) assay. Biologic materials composed of liver extracellular matrix (LECM) and small intestinal submucosa (SIS) ECM that are recognized for constructive tissue remodeling, and polypropylene mesh that is associated with pro-inflammatory macrophage phenotype activation are used as controls in the animal model. The AA silk graft shows a host response similar to SIS with few foreign body multinucleate giant cells, vascularization, high CD206 expression, and high M2-like: M1-like macrophage phenotype ratio. Exposure to AA silk degradation products in vitro induces a higher arginase: iNOS ratio in both naive BMDM and pro-inflammatory activated BMDM; and higher Fizz1: iNOS ratio in pro-inflammatory activated BMDM. These data suggest that the AA silk supports a pro-remodeling macrophage response with potential therapeutic applications.

Hernia mesh infection treatment following the repair of abdominal wall hernias: A single-center experience

INTRODUCTION

The mesh-based repair of abdominal wall hernias is a commonly employed approach as it is easy to implement and associated with low rates of hernia recurrence. However, the occurrence of hernia mesh infections following such repair can be extremely serious, and no clinical consensus regarding the optimal treatment of such infections has been established. This study was thus developed to review the management of hernia mesh infection cases treated at our center, summarizing the demographic and clinical characteristics of affected patients and summarizing our associated therapeutic experiences.

METHODS

Data pertaining to 64 cases of hernia mesh infections treated at our center were retrospectively reviewed. Data were obtained from patient medical records, including general situation, hernia type, prior hernia repair approaches, type of mesh, and postoperative condition. Other reviewed outcomes include bacteriological and imaging findings, as well as treatment outcomes. In cases where conservative management was not successful, the approach to mesh removal (laparoscopic vs. open) was made based on the primary surgical approach and the type of material used for the repair.

RESULTS

In total, 42 patients underwent primary open inguinal hernioplasty (including plug repair, preperitoneal mesh repair, and Lichtenstein repair), while 11 patients underwent laparoscopic repair (9 transabdominal preperitoneal, TAPP and 2 totally extraperitoneal,TEP), and 11 patients with incisional hernias underwent the intraperitoneal onlay mesh (IPOM) procedure. Six patients exhibited mesh erosion of the internal organs. Of these patients, 38 underwent mesh removal via open debridement, while 9 underwent laparoscopic exploration and open debridement, and 1 underwent laparoscopic mesh removal. No patients exhibited serious postoperative sequelae, serious complications, or mortality after the treatment of mesh infections.One patient experienced postoperative infection recurrence following partial mesh removal, with the appearance of a small fistula. Hernias recurred in 2 patients following mesh removal, and 1 patient underwent repair via laparoscopic IPOM.

CONCLUSIONS

While conservative treatment can cure early mesh infections, there is nonetheless a risk that these infections will recur. In view of the variety of surgical intervention of abdominal wall hernias at present,treatment of mesh infection should be individualized. Our findings suggest that hernias repaired via the placement of mesh in the preperitoneal space can more readily contribute to internal organ erosion and late-onset infections, with open debridement often being unable to completely remove the mesh without causing collateral damage. Laparoscopic exploration is an effective and minimally invasive approach to detecting internal organ involvement and removing the infected hernia mesh from affected patients.

Proteomic Analysis of Decellularized Extracellular Matrix: Achieving a Competent Biomaterial for Osteogenesis

Decellularized ECMs have been used as biological scaffolds for tissue repair due to their tissue-specific biochemical and mechanical composition, poorly simulated by other materials. It is used as patches and powders, and it could be further processed via enzymatic digestion under acidic conditions using pepsin. However, part of the bioactivity is lost during the digestion process due to protein denaturation. Here, stepwise digestion was developed to prepare a competent biomaterial for osteogenesis from three different ECM sources. In addition, three different proteases were compared to evaluate the most effective digestion protocol for specific cellular processes. GAGs and peptide quantification showed that the stepwise method yielded a higher concentration of bioactive residues. Circular dichroism analysis also showed that the stepwise approach preserved the secondary structures better. The protein profiles of the digested ECMs were analyzed, and it was found to be highly diverse and tissue-specific. The digestion of ECM from pericardium produced peptides originated from 94 different proteins, followed by 48 proteins in ECM from tendon and 35 proteins in ECM from bone. In addition, digested products from pericardium ECM yielded increased proliferation and differentiation of bone marrow mesenchymal stem cells to mature osteoblasts.

Development of Bio-artificial Esophageal Tissue Engineering Utilization for Circumferential Lesion Transplantation: A Narrative Review

The esophagus is the gastrointestinal tract's primary organ that transfers bolus into the stomach with peristaltic motion. Therefore, its lesions cause a significant disturbance in the nutrition and digestive system. Esophageal disease treatment sometimes requires surgical procedures that involve removal and circumferential full-thickness replacement. Unlike other organs, the esophagus has a limited regeneration ability and cannot be transplanted from donors. There are various methods of restoring the esophageal continuity; however, they are associated with certain flaws that lead to a non-functional recovery. As an exponentially growing science, tissue engineering has become a leading technique for the development of tissue replacement to repair damaged esophageal segments. Scaffold plays a significant role in the process of tissue engineering, as it acts as a template for the regeneration of growing tissue. A variety of scaffolds have been studied to replace the esophagus. Due to the many tissue quality challenges, the results are still inadequate and need to be improved. The success of esophageal tissue regeneration will finally depend on the scaffold's capability to mimic natural tissue properties and provide a qualified environment for regeneration. Thereby, scaffold fabrication techniques are fundamental. This article reviews the recent developments in esophageal tissue engineering for the treatment of circumferential lesions based on scaffold biomaterial engineering approaches.

CWHM-12, an Antagonist of Integrin-Mediated Transforming Growth Factor-Beta Activation Confers Protection During Early Mycobacterium tuberculosis Infection in Mice

Tuberculosis (TB) caused by the pathogenic bacterium Mycobacterium tuberculosis (Mtb) is one of the most lethal infectious diseases in the world. Presently, Bacillus Calmette-Guerin, the vaccine approved for use against TB, does not offer complete protection against the disease, which necessitates the development of new therapeutics to treat this infection. Overexpression of transforming growth factor beta (TGF-β) is associated with pulmonary profibrotic changes. The inactive TGF-β secreted is activated through its cleavage and release by αv integrins. Integrin-mediated regulation of TGF-β is considered as a master switch in the profibrotic process and a potential therapeutic target. Thus, in this study, we sought to determine if treatment with a broad range antagonist of integrins, CWHM-12, has the potency to inhibit pulmonary fibrosis and enhance Mtb control in a highly susceptible mouse model of Mtb infection, namely the C3Heb/FeJ (FeJ). CWHM-12 treatment at the early stages of Mtb infection was efficacious in reducing disease severity and inflammation associated with decreased iNOS, MIP-2, and IL-10 production without degradation of collagen. This suggests a potential for CWHM-12 targeting of TGF-β to be explored as an adjunct therapeutic for early Mtb infection.

Impaired ketogenesis ties metabolism to T cell dysfunction in COVID-19

Anorexia and fasting are host adaptations to acute infection, inducing a metabolic switch towards ketogenesis and the production of ketone bodies, including β-hydroxybutyrate (BHB) ^1-6. However, whether ketogenesis metabolically influences the immune response in pulmonary infections remains unclear. Here we report impaired production of BHB in humans with SARS-CoV-2-induced but not influenza-induced acute respiratory distress syndrome (ARDS). CD4+ T cell function is impaired in COVID-19 and BHB promotes both survival and production of Interferon-γ from CD4⁺ T cells. Using metabolic tracing analysis, we uncovered that BHB provides an alternative carbon source to fuel oxidative phosphorylation (OXPHOS) and the production of bioenergetic amino acids and glutathione, which is important for maintaining the redox balance. T cells from patients with SARS-CoV-2-induced ARDS were exhausted and skewed towards glycolysis, but can be metabolically reprogrammed by BHB to perform OXPHOS, thereby increasing their functionality. Finally, we demonstrate that ketogenic diet (KD) and delivery of BHB as ketone ester drink restores CD4+ T cell metabolism and function in respiratory infections, ultimately reducing the mortality of SARS-CoV-2 infected mice. Altogether, our data reveal BHB as alternative carbon source promoting T cell responses in pulmonary viral infections, highlighting impaired ketogenesis as a potential confounder of severe COVID-19.

Three-Dimensional Bioprinting of Decellularized Extracellular Matrix-Based Bioinks for Tissue Engineering

Three-dimensional (3D) bioprinting is one of the most promising additive manufacturing technologies for fabricating various biomimetic architectures of tissues and organs. In this context, the bioink, a critical element for biofabrication, is a mixture of biomaterials and living cells used in 3D printing to create cell-laden structures. Recently, decellularized extracellular matrix (dECM)-based bioinks derived from natural tissues have garnered enormous attention from researchers due to their unique and complex biochemical properties. This review initially presents the details of the natural ECM and its role in cell growth and metabolism. Further, we briefly emphasize the commonly used decellularization treatment procedures and subsequent evaluations for the quality control of the dECM. In addition, we summarize some of the common bioink preparation strategies, the 3D bioprinting approaches, and the applicability of 3D-printed dECM bioinks to tissue engineering. Finally, we present some of the challenges in this field and the prospects for future development.

Development and in vitro investigation of a biodegradable mesh for the treatment of stress urinary incontinence

Introduction and hypothesis

The use of polypropylene (PP) mesh for stress urinary incontinence (SUI) surgery has declined because of safety concerns. The aim of this study is to evaluate a biodegradable polycaprolactone (PCL) mesh and a PCL composite mesh tissue engineered with human uterine fibroblasts (HUFs) for SUI surgery by comparing mechanical properties and in vitro biocompatibility to commercially available PP and porcine dermis (PD).

Methods

The mechanical properties of four scaffold materials were evaluated: PCL, PCL-collagen-hyaluronic acid composite, acellular porcine dermal collagen (PD) (Pelvicol™) and polypropylene (Gynecare TVT™ Exact®). HUFs were seeded on separate scaffolds. After 7 and 14 days scaffolds were assessed for metabolic activity and cell proliferation using Alamar Blue, Live/Dead and PicoGreen assays. Soluble collagen production was evaluated using a Sircol assay.

Results

PCL and the composite scaffold reached ultimate tensile strength (UTS) values closest to healthy pelvic floor tissue (PCL = 1.19 MPa; composite = 1.13 MPa; pelvic floor = 0.79 MPa; Lei et al. Int Urogynecol J Pelvic Floor Dysfunct. 18(6):603-7, 2007). Cells on PCL showed significantly greater cell viability than PP at day 7 (p < 0.0001). At D14 the composite scaffold showed significantly greater cell viability than PP (p = 0.0006). PCL was the best performing scaffold for soluble collagen production at day 14 (106.1 μg versus 13.04 μg for PP, p = 0.0173).

Conclusions

We have designed a biodegradable PCL mesh and a composite mesh which demonstrate better biocompatibility than PP and mechanical properties closer to that of healthy pelvic floor tissue. This in vitro study provides promising evidence that these two implants should be evaluated in animal and human trials.

Latest Trends on the Attenuation of Systemic Foreign Body Response and Infectious Complications of Synthetic Hernia Meshes

Throughout the past few years, hernia incidence has remained at a high level worldwide, with more than 20 million people requiring hernia surgery each year. Synthetic hernia meshes play an important role, providing a microenvironment that attracts and harbors host cells and acting as a permanent roadmap for intact abdominal wall reconstruction. Nevertheless, it is still inevitable to cause not-so-trivial complications, especially chronic pain and adhesion. In long-term studies, it was found that the complications are mainly caused by excessive fibrosis from the foreign body reaction (FBR) and infection resulting from bacterial colonization. For a thorough understanding of their complex mechanism and providing a richer background for mesh development, herein, we discuss different clinical mesh products and explore the interactions between their structure and complications. We further explored progress in reducing mesh complications to provide varied strategies that are informative and instructive for mesh modification in different research directions. We hope that this work will spur hernia mesh designers to step up their efforts to develop more practical and accessible meshes by improving the physical structure and chemical properties of meshes to combat the increasing risk of adhesions, infections, and inflammatory reactions. We conclude that further work is needed to solve this pressing problem, especially in the analysis and functionalization of mesh materials, provided of course that the initial performance of the mesh is guaranteed.

Host-biomaterial interactions in mesh complications after pelvic floor reconstructive surgery

Polypropylene (PPL) mesh is widely used in pelvic floor reconstructive surgery for prolapse and stress urinary incontinence. However, some women, particularly those treated using transvaginal PPL mesh placement for prolapse, experience intractable pain and mesh exposure or extrusion. Explanted tissue from patients with complications following transvaginal implantation of mesh is typified by a dense fibrous capsule with an immune cell-rich infiltrate, suggesting that the host immune response has a role in transvaginal PPL mesh complications through the separate contributions of the host (patient), the biological niche within which the material is implanted and biomaterial properties of the mesh. This immune response might be strongly influenced by both the baseline inflammatory status of the patient, surgical technique and experience, and the unique hormonal, immune and microbial tissue niche of the vagina. Mesh porosity, surface area and stiffness also might have an effect on the immune and tissue response to transvaginal mesh placement. Thus, a regulatory pathway is needed for mesh development that recognizes the roles of host and biological factors in driving the immune response to mesh, as well as mandatory mesh registries and the longitudinal surveillance of patients.

Decellularized tendon matrix membranes prevent post-surgical tendon adhesion and promote functional repair

Adhesion often occurs after tendon injury, and results in sliding disorder and movement limitation with no ideal solution for it in clinic. In this study, an anti-adhesion membrane, i.e., decellularized tendon matrix (DTM) for tendon is successfully prepared by an optimized tendon decellularization method from homologous extracellular matrix. Microsection technology has been used to optimize the method of decellularization in order to better preserve the bioactive components in tissues and reduce the chemical reagent residues on the premise of effective decellularization with relatively shorter time and less reagents for decellularization. The physic-chemical properties and biological functions of DTM are evaluated, and high-throughput and high-precision tandem mass tags (TMT) labeling proteomics technology is used to analyze protein components of DTM, which may provide the scientific support for application of the innovative product. In vitro biosafety tests show that DTM not only is non-toxic but also promote cell proliferation. Subcutaneous implantation test confirms that DTM is completely degraded after 12 weeks and there is no obvious inflammatory reaction. The results of Achilles tendon repair in rabbits show that DTM can not only prevent tendon adhesion but also improve the quality of tendon repair, which demonstrates its tremendous application potential. STATEMENT OF SIGNIFICANCE: There is no ideal solution for adhesion after tendon injury. In this study, a dense tendon anti-adhesion membrane (DTM) was successfully prepared from homologous extracellular matrix (ECM). This DTM could effectively retain bioactive ingredients, and prevent adhesion as well as improve the quality of tendon repair in vivo. An optimized decellularization method was used which could effectively decellularize tendon in a short time, better preserve bioactive components, and reduce reagent residues. For the first time, high-throughput and high-precision tandem mass tags (TMT) labeling proteomics technology was used to qualitatively and quantitatively analyze the protein composition of fresh tendon, acellular tendon and DTM, which provided not only scientific support for the application of DTM, but also comprehensive and accurate data support for related research of bovine tendons and decellularization.

Translational Applications of Hydrogels

Advances in hydrogel technology have unlocked unique and valuable capabilities that are being applied to a diverse set of translational applications. Hydrogels perform functions relevant to a range of biomedical purposes-they can deliver drugs or cells, regenerate hard and soft tissues, adhere to wet tissues, prevent bleeding, provide contrast during imaging, protect tissues or organs during radiotherapy, and improve the biocompatibility of medical implants. These capabilities make hydrogels useful for many distinct and pressing diseases and medical conditions and even for less conventional areas such as environmental engineering. In this review, we cover the major capabilities of hydrogels, with a focus on the novel benefits of injectable hydrogels, and how they relate to translational applications in medicine and the environment. We pay close attention to how the development of contemporary hydrogels requires extensive interdisciplinary collaboration to accomplish highly specific and complex biological tasks that range from cancer immunotherapy to tissue engineering to vaccination. We complement our discussion of preclinical and clinical development of hydrogels with mechanical design considerations needed for scaling injectable hydrogel technologies for clinical application. We anticipate that readers will gain a more complete picture of the expansive possibilities for hydrogels to make practical and impactful differences across numerous fields and biomedical applications.

Engineering Vascularized Composite Allografts Using Natural Scaffolds: A Systematic Review

INTRODUCTION

Vascularized Composite Allotransplantation refers to the transplantation of multiple tissues as a functional unit from a deceased donor to a recipient with a severe injury. These grafts serve as potential replacements for traumatic tissue losses. The main problems are the consequences of the long immunosuppressive drugs medications and the lake of compatible donor. To avoid these limitations, decellularization/recellularization constitute an attractive approach. The aim of decellularization/recellularization technology is to develop immunogenic free biological substitutes that will restore, maintain, or improve tissue and organ's function.

METHODS

A PubMed search was performed for articles on decellularization and recellularization of composite tissue allografts between March and February 2021, with no restrictions in publication year. The selected reports were evaluated in terms of decellularization protocols, assessment of decellularized grafts, and evaluation of their biocompatibility and repopulation with cells both in vitro and in vivo.

RESULTS

The search resulted in a total of 88 articles. Each article was reviewed, 77 were excluded and the remaining 11 articles reported decellularization of 12 different vascular composite allografts in humans (four), large animals (three), and small animals (rodents) (five). The decellularization protocol for vascularized composite allotransplantation varies slightly between studies, but majority of the reports employ 1% sodium dodecyl sulfate as the main reagent for decellularization. The immunological response of the decellularized scaffolds remains poorly evaluated. Few authors have been able to attempt the recellularization and transplantation of these scaffolds. Successful transplantation seems to require prior recellularization.

CONCLUSION

Decellularization/recellularization is a promising, growing, emerging developing research field in vascular composite allotransplantation.

Tailoring electrospun mesh for a compliant remodeling in the repair of full-thickness abdominal wall defect - The role of decellularized human amniotic membrane and silk fibroin

Tailored electrospun meshes have been increasingly explored for abdominal wall defect repair in preclinical and clinical studies. However, the fabrication of a bioengineered mesh adapts to the intraperitoneal repair for a compliant remodeling remains a great challenge. In this study, we fabricated a functional mesh by combining polycaprolactone (PCL) with silk fibroin (SF) and decellularized human amniotic membrane (HAM) proportionally via electrospinning. SF was integrated with PCL (40:60 w/w) to regulate the structural flexibility. Micronized HAM was incorporated to PCL/SF (10:90 w/w) to provide a biocompatible milieu with functions being conferred to facilitate intraperitoneal repair. After the blend electrospinning, the PCL/SF/HAM mesh was characterized in vitro and implanted into the rat model with a full-thickness defect for a comprehensive evaluation in comparison to the PCL and PCL/SF meshes. The results demonstrated that electrospinning fabricated PCL stabilized the mechanical elongation toward approximating the native counterparts after integrating with SF. After integrating with HAM, which is coupled with diverse biomolecular compositions, the developed PCL/SF/HAM mesh provided a better microenvironment for cell proliferation and vasculogenic network over other meshes without HAM addition and possessed the functions capable of inhibiting transforming growth factor β1 (TGF-β1) expression and collagen secretion under inflammatory conditions. Moreover, the functional mesh developed less-intensive adhesion along with histologically weaker inflammatory response and foreign body reaction than the PCL and PCL/SF meshes after 90 days in vivo. During the remodeling process, the bioactive structure induced more pronounced neovascularization and remarkable incorporation of collagen and elastin fibers and contractile filaments for a mechanically sufficient and physiologically stiffness-matched healing. This tailor-made mesh expands the intraperitoneal applicability of conventional electrospun meshes for a compliant remodeling in the repair of abdominal wall defects.

Engineering skeletal muscle: Building complexity to achieve functionality

Volumetric muscle loss (VML) VML is defined as the loss of a critical mass of skeletal muscle that overwhelms the muscle's natural healing mechanisms, leaving patients with permanent functional deficits and deformity. The treatment of these defects is complex, as skeletal muscle is a composite structure that relies closely on the action of supporting tissues such as tendons, vasculature, nerves, and bone. The gold standard of treatment for VML injuries, an autologous muscle flap transfer, suffers from many shortcomings but nevertheless remains the best clinically available avenue to restore function. This review will consider the use of composite tissue engineered constructs, with multiple components that act together to replicate the function of an intact muscle, as an alternative to autologous muscle flaps. We will discuss recent advances in the field of tissue engineering that enable skeletal muscle constructs to more closely reproduce the functionality of an autologous muscle flap by incorporating vasculature, promoting innervation, and reconstructing the muscle-tendon boundary. Additionally, our understanding of the cellular composition of skeletal muscle has evolved to recognize the importance of a diverse variety of cell types in muscle regeneration, including fibro/adipogenic progenitors and immune cells like macrophages and regulatory T cells. We will address recent advances in our understanding of how these cell types interact with, and can be incorporated into, implanted tissue engineered constructs.

Development of plasma functionalized polypropylene wound dressing for betaine hydrochloride controlled drug delivery on diabetic wounds

Diabetes Mellitus is one of the most worrying issues among illnesses, and its chronic subsequences almost refer to inflammations and infections. The loading and local release of antioxidants to wounds may decrease inflammations. However, the low wettability of PolyPropylene (PP) restricts the drug from loading. So, to increase the adhesion of PP for loading an optimum amount of Betaine Hydrochloride (BET), plasma has been applied in two steps of functionalization and polymerization, which has been confirmed with FE-SEM, ATR-FTIR, and EDX. The new chemistry of the surface led to almost 80% of BET loaded. The drug-releasing ratio studied by HPLC approved the presence of a PEG-like layer, which was coated by polymerization of tetraglyme. To evaluate the wound healing potential of the application of PP meshes treated by plasma, 72 Wistar rats were subdivided into four groups. The skin injury site was removed and underwent biomechanical tests, stereological analysis, and RNA extraction. The results showed a significant improvement in the polymerized scaffold containing BET for skin injury. The present study suggests that the use of a modified PP mesh can induce tissue regeneration and accelerate wound healing at the skin injury site.

Functionalized Strategies and Mechanisms of the Emerging Mesh for Abdominal Wall Repair and Regeneration

Meshes have been the overwhelmingly popular choice for the repair of abdominal wall defects to retrieve the bodily integrity of musculofascial layer. Broadly, they are classified into synthetic, biological and composite mesh based on their mechanical and biocompatible features. With the development of anatomical repair techniques and the increasing requirements of constructive remodeling, however, none of these options satisfactorily manages the conditional repair. In both preclinical and clinical studies, materials/agents equipped with distinct functions have been characterized and applied to improve mesh-aided repair, with the importance of mesh functionalization being highlighted. However, limited information exists on systemic comparisons of the underlying mechanisms with respect to functionalized strategies, which are fundamental throughout repair and regeneration. Herein, we address this topic and summarize the current literature by subdividing common functions of the mesh into biomechanics-matched, macrophage-mediated, integration-enhanced, anti-infective and antiadhesive characteristics for a comprehensive overview. In particular, we elaborate their effects separately with respect to host response and integration and discuss their respective advances, challenges and future directions toward a clinical alternative. From the vastly different approaches, we provide insight into the mechanisms involved and offer suggestions for personalized modifications of these emerging meshes.

Tissue-Specific Hydrogels Ameliorate Hepatic Ischemia/Reperfusion Injury in Rats by Regulating Macrophage Polarization via TLR4/NF-κB Signaling

Injectable acellular matrix hydrogels are proven to be potential translational materials to facilitate the repairment in various tissues. However, their potential to repair hepatic ischemia/reperfusion injury (IRI) has not been explored. In this work, we made hepatic acellular matrix (HAM) hydrogels based on the decellularized process and evaluated the biocompatibility and hepatoprotective effects in a rat IRI model. HAM hydrogels supported viability, proliferation, and attachment of hepatocytes in vitro. Treatment with HAM hydrogels significantly attenuated hepatic damage caused by IRI, as evidenced by hepatic biochemistry, histology, and inflammatory responses. Importantly, HAM hydrogels inhibited macrophage M1 (CD68/CCR7) differentiation but promoted M2 (CD68/CD206) differentiation. Additionally, TLR4/NF-κB signaling was found to be involved in the hepatoprotective effect of HAM hydrogels. Collectively, our study reveals that HAM hydrogels ameliorate hepatic IRI by facilitating M2 polarization via TLR4/NF-κB signaling.

SARS-CoV-2 and tissue damage: current insights and biomaterial-based therapeutic strategies

The effect of SARS-CoV-2 infection on humanity has gained worldwide attention and importance due to the rapid transmission, lack of treatment options and high mortality rate of the virus. While scientists across the world are searching for vaccines/drugs that can control the spread of the virus and/or reduce the risks associated with infection, patients infected with SARS-CoV-2 have been reported to have tissue/organ damage. With most tissues/organs having limited regenerative potential, interventions that prevent further damage or facilitate healing would be helpful. In the past few decades, biomaterials have gained prominence in the field of tissue engineering, in view of their major role in the regenerative process. Here we describe the effect of SARS-CoV-2 on multiple tissues/organs, and provide evidence for the positive role of biomaterials in aiding tissue repair. These findings are further extrapolated to explore their prospects as a therapeutic platform to address the tissue/organ damage that is frequently observed during this viral outbreak. This study suggests that the biomaterial-based approach could be an effective strategy for regenerating tissues/organs damaged by SARS-CoV-2.

Biodegradable materials for surgical management of stress urinary incontinence: A narrative review

Stress urinary incontinence (SUI) was managed with techniques such as colposuspension, autologous fascia sling and urethral bulking agents. The introduction of the mid-urethral polypropylene (PP) sling in the 1990s led to a significant and rapid global change in SUI surgery. The synthetic non-degradable PP sling had superior results to traditional SUI procedures but its use has now declined due to significant complications such as pain and mesh erosion. These complications are attributed to its poor biocompatibility and integration into vaginal tissues. The efficacy of PP was extrapolated from studies on abdominal wall repair and it is now clear that integration of implanted materials in the pelvic floor differs from the abdominal wall. With PP prohibited in some jurisdictions, female patients with SUI have few management options. In the present review we summarise recent advances in SUI surgery and evaluate potential alternatives to PP slings with a particular focus on degradable materials. Allograft and xenograft materials demonstrate good biocompatibility but have yielded suboptimal cure rates. Tissue engineered synthetic degradable materials outperform unmodified synthetic degradable materials in terms of biomechanics and cell support. Synthetic tissue engineered degradable materials show promising results from in vitro studies and future research should focus on animal and human trials in this field.

In-vitro Characterization of a Hernia Mesh Featuring a Nanostructured Coating

Abdominal hernia repair is a frequently performed surgical procedure worldwide. Currently, the use of polypropylene (PP) surgical meshes for the repair of abdominal hernias constitutes the primary surgical approach, being widely accepted as superior to primary suture repair. Surgical meshes act as a reinforcement for the weakened or damaged tissues and support tissue restoration. However, implanted meshes could suffer from poor integration with the surrounding tissues. In this context, the present study describes the preliminary evaluation of a PCL-Gel-based nanofibrous coating as an element to develop a multicomponent hernia mesh device (meshPCL-Gel) that could overcome this limitation thanks to the presence of a nanostructured biomimetic substrate for enhanced cell attachment and new tissue formation. Through the electrospinning technique, a commercial PP hernia mesh was coated with a nanofibrous membrane from a polycaprolactone (PCL) and gelatin (Gel) blend (PCL-Gel). Resulting PCL-Gel nanofibers were homogeneous and defect-free, with an average diameter of 0.15 ± 0.04 μm. The presence of Gel decreased PCL hydrophobicity, so that membranes average water contact angle dropped from 138.9 ± 1.1° (PCL) to 99.9 ± 21.6°, while it slightly influenced mechanical properties, which remained comparable to those of PCL (E = 15.7 ± 2.7 MPa, σ R = 7.7 ± 0.6 ε R = 118.8 ± 13.2%). Hydrolytic and enzymatic degradation was conducted on PCL-Gel up to 28 days, with maximum weight losses around 20 and 40%, respectively. The meshPCL-Gel device was obtained with few simple steps, with no influences on the original mechanical properties of the bare mesh, and good stability under physiological conditions. The biocompatibility of meshPCL-Gel was assessed by culturing BJ human fibroblasts on the device, up to 7 days. After 24 h, cells adhered to the nanofibrous substrate, and after 72 h their metabolic activity was about 70% with respect to control cells. The absence of detectable lactate dehydrogenase in the culture medium indicated that no necrosis induction occurred. Hence, the developed nanostructured coating provided the meshPCL-Gel device with chemical and topographical cues similar to the native extracellular matrix ones, that could be exploited for enhancing the biological response and, consequently, mesh integration, in abdominal wall hernia repair.

Next-generation surgical meshes for drug delivery and tissue engineering applications: materials, design and emerging manufacturing technologies

Abstract

Surgical meshes have been employed in the management of a variety of pathological conditions including hernia, pelvic floor dysfunctions, periodontal guided bone regeneration, wound healing and more recently for breast plastic surgery after mastectomy. These common pathologies affect a wide portion of the worldwide population; therefore, an effective and enhanced treatment is crucial to ameliorate patients’ living conditions both from medical and aesthetic points of view. At present, non-absorbable synthetic polymers are the most widely used class of biomaterials for the manufacturing of mesh implants for hernia, pelvic floor dysfunctions and guided bone regeneration, with polypropylene and poly tetrafluoroethylene being the most common. Biological prostheses, such as surgical grafts, have been employed mainly for breast plastic surgery and wound healing applications. Despite the advantages of mesh implants to the treatment of these conditions, there are still many drawbacks, mainly related to the arising of a huge number of post-operative complications, among which infections are the most common. Developing a mesh that could appropriately integrate with the native tissue, promote its healing and constructive remodelling, is the key aim of ongoing research in the area of surgical mesh implants. To this end, the adoption of new biomaterials including absorbable and natural polymers, the use of drugs and advanced manufacturing technologies, such as 3D printing and electrospinning, are under investigation to address the previously mentioned challenges and improve the outcomes of future clinical practice. The aim of this work is to review the key advantages and disadvantages related to the use of surgical meshes, the main issues characterizing each clinical procedure and the future directions in terms of both novel manufacturing technologies and latest regulatory considerations.

Graphic abstract

Designing Decellularized Extracellular Matrix-Based Bioinks for 3D Bioprinting

3D bioprinting is an emerging technology to fabricate tissues and organs by precisely positioning cells into 3D structures using printable cell-laden formulations known as bioinks. Various bioinks are utilized in 3D bioprinting applications; however, developing the perfect bioink to fabricate constructs with biomimetic microenvironment and mechanical properties that are similar to native tissues is a challenging task. In recent years, decellularized extracellular matrix (dECM)-based bioinks have received an increasing attention in 3D bioprinting applications, since they are derived from native tissues and possess unique, complex tissue-specific biochemical properties. This review focuses on designing dECM-based bioinks for tissue and organ bioprinting, including commonly used decellularization and decellularized tissue characterization methods, bioink formulation and characterization, applications of dECM-based bioinks, and most recent advancements in dECM-based bioink design.

Role of 4-hydroxybutyrate in increased resistance to surgical site infections associated with surgical meshes

An increased resistance to surgical site infections has been associated with surgical meshes composed of naturally occurring materials, including poly-4-hydroxybutrate (4HB). 4HB is a naturally occurring short-chain fatty acid that has been shown to promote endogenous expression of the Cramp gene coding for the antimicrobial peptide (AMP) cathelicidin LL-37 in murine bone marrow-derived macrophages. The molecular pathways involved in the 4HB-induced cathelicidin LL-37 expression have not yet been identified. The present study showed that transcriptional activation of the Cramp gene by 4HB is independent of inhibition of histone deacetylase (HDAC) activity, and that upregulation of Cramp is modulated by the G-protein coupled receptor GPR109A. Furthermore, an intracellular signaling cascade that promotes the activation of the MAP kinases, p38 and JNK, and a subsequent NF-κB phosphorylation downstream from p38 is essential for the AMP transcriptional response in 4HB-stimulated macrophages. The findings provide a solid scientific basis and rationale for the decreased incidence of surgical site infections with the use of this type of surgical meshes. Further clinical significance is found in the fact that the 4HB activated molecular pathway includes common targets of frequently used nonsteroidal anti-inflammatory drugs (NSAIDs) and other FDA approved drugs recognizing G-protein coupled receptors.

Bioinspired Hydrogel Coating Based on Methacryloyl Gelatin Bioactivates Polypropylene Meshes for Abdominal Wall Repair

Considering the potential of hydrogels to mimic the cellular microenvironment, methacryloyl gelatin (GelMA) and methacryloyl mucin (MuMA) were selected and compared as bioinspired coatings for commercially available polypropylene (PP) meshes for ventral hernia repair. Thin, elastic hydrated hydrogel layers were obtained through network-forming photo-polymerization, after immobilization of derivatives on the surface of the PP fibers. Fourier transform infrared spectroscopy (FTIR) proved the successful coating while the surface morphology and homogeneity were investigated by scanning electron microscopy (SEM) and micro-computed tomography (micro-CT). The stability of the hydrogel layers was evaluated through biodynamic tests performed on the coated meshes for seven days, followed by inspection of surface morphology through SEM and micro-CT. Taking into account that platelet-rich plasma (PRP) may improve healing due to its high concentration of growth factors, this extract was used as pre-treatment for the hydrogel coating to additionally stimulate cell interactions. The performed advanced characterization proved that GelMA and MuMA coatings can modulate fibroblasts response on PP meshes, either as such or supplemented with PRP extract as a blood-derived bioactivator. GelMA supported the best cellular response. These findings may extend the applicative potential of functionalized gelatin opening a new path on the research and engineering of a new generation of bioactive meshes.

Host macrophage response to injectable hydrogels derived from ECM and α-helical peptides

Tissue engineering materials play a key role in how closely the complex architectural and functional characteristics of native healthy tissue can be replicated. Traditional natural and synthetic materials are superseded by bespoke materials that cross the boundary between these two categories. Here we present hydrogels that are derived from decellularised extracellular matrix and those that are synthesised from de novo α-helical peptides. We assess in vitro activation of murine macrophages to our hydrogels and whether these gels induce an M1-like or M2-like phenotype. This was followed by the in vivo immune macrophage response to hydrogels injected into rat partial-thickness abdominal wall defects. Over 28 days we observe an increase in mononuclear cell infiltration at the hydrogel-tissue interface without promoting a foreign body reaction and see no evidence of hydrogel encapsulation or formation of multinucleate giant cells. We also note an upregulation of myogenic differentiation markers and the expression of anti-inflammatory markers Arginase1, IL-10, and CD206, indicating pro-remodelling for all injected hydrogels. Furthermore, all hydrogels promote an anti-inflammatory environment after an initial spike in the pro-inflammatory phenotype. No difference between the injected site and the healthy tissue is observed after 28 days, indicating full integration. These materials offer great potential for future applications in regenerative medicine and towards unmet clinical needs. STATEMENT OF SIGNIFICANCE: Materials play a key role in how closely the complex architectural and functional characteristics of native healthy tissue can be replicated in tissue engineering. Here we present injectable hydrogels derived from decellularised extracellular matrix and de novo designed α-helical peptides. Over 28 days in the rat abdominal wall we observe an increase in mononuclear cell infiltration at the hydrogel-tissue interface with no foreign body reaction, no evidence of hydrogel encapsulation and no multinucleate giant cells. Our data indicate pro-remodelling and the promotion of an anti-inflammatory environment for all injected hydrogels with evidence of full integration with healthy tissue after 28 days. These unique materials offer great potential for future applications in regenerative medicine and towards designing materials for unmet clinical needs.

Stress Urinary Incontinence and Pelvic Organ Prolapse: Biologic Graft Materials Revisited

Symptomatic stress urinary incontinence (SUI) and pelvic organ prolapse (POP) refractory to conservative management with pelvic floor muscle training or vaginal pessaries may warrant surgical intervention with different forms of biologic or synthetic material. However, in recent years, several global regulatory agencies have issued health warnings and recalled several mesh products due to an increase in complications such as mesh erosion, infection, chronic pain, and perioperative bleeding. At present, current surgical treatment strategies for SUI and POP are aimed at developing biological graft materials with similar mechanical properties to established synthetic meshes, but with improved tissue integration and minimal host response. This narrative review aims to highlight recent studies related to the development of biomimetic and biologic graft materials as alternatives to traditional synthetic materials for SUI/POP repair in female patients. We also investigate complications and technical limitations associated with synthetic mesh and biological biomaterials in conventional SUI and POP surgery. Our findings demonstrate that newly developed biologic grafts have a lower incidence of adverse events compared to synthetic biomaterials. However there remains a significant disparity between success in preclinical trials and long-term clinical translation. Further characterization on the optimal structural, integrative, and mechanical properties of biological grafts is required before they can be reliably introduced into clinical practice for SUI and POP surgery. Impact statement Our review article aims to outline the clinical history of developments and controversies associated with the use of synthetic mesh materials in the surgical treatment of stress urinary incontinence and pelvic organ prolapse, as well as highlighting recent advancements in the area of biological graft materials and their potential importance in an area that remains an enduring issue for patients and clinicians alike. This article aims to provide a concise summary of previous controversies in the field of urinary incontinence, while evaluating the future of potential biomaterials in this field.

Combination of Polypropylene Mesh and in Situ Injectable Mussel-Inspired Hydrogel in Laparoscopic Hernia Repair for Preventing Post-Surgical Adhesions in the Piglet Model

Polypropylene (PP) mesh has been used successfully for a long time in clinical practice as an impressive prosthesis for ventral hernia repair. To utilize a physical barrier for separating mesh from viscera is a general approach for preventing adhesions in clinical practice. However, a serious abdominal adhesion between the mesh and viscera can possibly occur post-hernia, especially with the small intestine; this can lead to a series of complications, such as chronic pain, intestinal obstruction, and fistula. Thus, determining how to prevent abdominal adhesions between the mesh and viscera is still an urgent clinical problem. In this study, a dopamine-functionalized polysaccharide derivative (oxidized-carboxymethylcellulose-g-dopamine, OCMC-DA) was synthesized; this was blended with carboxymethylchitosan (CMCS) to form a hydrogel (OCMC-DA/CMCS) in situ at the appropriate time. The physical and chemical properties of the hydrogel were characterized successfully, and its excellent biocompatibility was presented by the in vitro cell test. The combination of this hydrogel and PP mesh was used in laparoscopic surgery for repairing the abdominal wall defect, where the hydrogel could become fixed in situ on the PP mesh to form an anti-adhesion gel-mesh. The results showed that the gel-mesh could prevent abdominal adhesions effectively in the piglet model. Moreover, the histology and immunohistochemical staining proved that the gel-mesh could effectively alleviate the inflammation reaction and deposition of collagen around the mesh, and it did not disturb the integration between mesh and abdominal wall. Thus, the gel-mesh has superior tissue compatibility.

Applications of decellularized materials in tissue engineering: advantages, drawbacks and current improvements, and future perspectives

Decellularized materials (DMs) are attracting more and more attention in tissue engineering because of their many unique advantages, and they could be further improved in some aspects through various means.

Landmarks in vaginal mesh development: polypropylene mesh for treatment of SUI and POP

Vaginal meshes used in the treatment of stress urinary incontinence (SUI) and pelvic organ prolapse (POP) have produced highly variable outcomes, causing life-changing complications in some patients while providing others with effective, minimally invasive treatments. The risk:benefit ratio when using vaginal meshes is a complex issue in which a combination of several factors, including the inherent incompatibility of the mesh material with some applications in pelvic reconstructive surgeries and the lack of appropriate regulatory approval processes at the time of the premarket clearance of these products, have contributed to the occurrence of complications caused by vaginal mesh. Surgical mesh used in hernia repair has evolved over many years, from metal implants to knitted polymer meshes that were adopted for use in the pelvic floor for treatment of POP and SUI. The evolution of the material and textile properties of the surgical mesh was guided by clinical feedback from hernia repair procedures, which were also being modified to obtain the best outcomes with use of the mesh. Current evidence shows how surgical mesh fails biomechanically when used in the pelvic floor and materials with improved performance can be developed using modern material processing and tissue engineering techniques.