Nitric oxide modulates metalloproteinase-2, collagen deposition and adhesion rate after polypropylene mesh implantation in the intra-abdominal wall

Microenvironment-triggered cascade metal-polyphenolic nanozyme for ROS/NO synergistic hyperglycemic wound healing

Wound infection of hyperglycemic patient often has extended healing period and increased probability due to the high glucose level. However, achieving precise and safe therapy of the hyperglycemic wound with specific wound microenvironment (WME) remains a major challenge. Herein, a WME-activated smart L-Arg/GOx@TA-Fe (LGTF) nanozymatic system composed of generally recognized as safe (GRAS) compound is engineered. The nanozymatic system combining metal-polyphenol nanozyme (tannic acid-Fe3+, TA-Fe) and natural enzyme (glucose oxidase, GOx) can consume the high-concentration glucose, generating reactive oxygen species (ROS) and nitric oxide (NO) in situ to synergistically disinfect hyperglycemia wound. In addition, glucose consumption and gluconic acid generation can lower glucose level to promote wound healing and reduce the pH of WME to enhance the catalytic activities of the LGTF nanozymatic system. Thereby, low-dose LGTF can perform remarkable synergistic disinfection and healing effect towards hyperglycemic wound. The superior biosafety, high catalytic antibacterial and beneficial WME regulating capacity demonstrate this benign GRAS nanozymatic system is a promising therapeutic agent for hyperglycemic wound.

Macrophages and fibroblasts in foreign body reactions: How mechanical cues drive cell functions?

Biomaterials, when implanted in the human body, can induce a series of cell- and cytokine-related reactions termed foreign body reactions (FBRs). In the progression of FBRs, macrophages regulate inflammation and healing by polarizing to either a pro-inflammatory or pro-healing phenotype and recruit fibroblasts by secreting cytokines. Stimulated by the biomaterials, fibrotic capsule is formed eventually. The implant, along with its newly formed capsule, introduces various mechanical cues that influence cellular functions. Mechanosensing proteins, such as integrins or ion channels, transduce extracellular mechanical signals into cytoplasm biochemical signals in response to mechanical stimuli. Consequently, the morphology, migration mode, function, and polarization state of the cells are affected. Modulated by different intracellular signaling pathways and their crosstalk, the expression of fibrotic genes increases with fibroblast activation and fibroblast to myofibroblast transition under stiff or force stimuli. However, summarized in most current studies, the outcomes of macrophage polarization in the effect of different mechanical cues are inconsistent. The underlying mechanisms should be investigated with more advanced technology and considering more interfering aspects. Further research is needed to determine how to modulate the progression of fibrotic capsule formation in FBR artificially.

Nanomaterial Nitric Oxide Delivery in Traumatic Orthopedic Regenerative Medicine

Achieving bone fracture union after trauma represents a major challenge for the orthopedic surgeon. Fracture non-healing has a multifactorial etiology and there are many risk factors for non-fusion. Environmental factors such as wound contamination, infection, and open fractures can contribute to non-healing, as can patient specific factors such as poor vascular status and improper immunologic response to fracture. Nitric oxide (NO) is a small, neutral, hydrophobic, highly reactive free radical that can diffuse across local cell membranes and exert paracrine functions in the vascular wall. This molecule plays a role in many biologic pathways, and participates in wound healing through decontamination, mediating inflammation, angiogenesis, and tissue remodeling. Additionally, NO is thought to play a role in fighting wound infection by mitigating growth of both Gram negative and Gram positive pathogens. Herein, we discuss recent developments in NO delivery mechanisms and potential implications for patients with bone fractures. NO donors are functional groups that store and release NO, independent of the enzymatic actions of NOS. Donor molecules include organic nitrates/nitrites, metal-NO complexes, and low molecular weight NO donors such as NONOates. Numerous advancements have also been made in developing mechanisms for localized nanomaterial delivery of nitric oxide to bone. NO-releasing aerogels, sol- gel derived nanomaterials, dendrimers, NO-releasing micelles, and core cross linked star (CCS) polymers are all discussed as potential avenues of NO delivery to bone. As a further target for improved fracture healing, 3d bone scaffolds have been developed to include potential for nanoparticulated NO release. These advancements are discussed in detail, and their potential therapeutic advantages are explored. This review aims to provide valuable insight for translational researchers who wish to improve the armamentarium of the feature trauma surgeon through use of NO mediated augmentation of bone healing.

Nitric oxide coating polypropylene mesh increases angiogenesis and reduces inflammatory response and apoptosis

OBJECTIVES

To evaluate the effect of implanted S-nitrosoglutathione (GSNO) coating polypropylene mesh in foreign-body response of rats.

METHODS

Thirty female rats underwent to subcutaneous implant of five polypropylene (PP) fragments: uncoated PP (control); PP polyvinylalcohol (PVA) coated and PP PVA + GSNO (1, 10 and 70 mMol) coated. After euthanasia (4 and 30 days), eight slides were prepared from each animal: hematoxylin-eosin (inflammatory response); unstained (birefringence collagen evaluation); TUNEL technique (apoptosis); and five for immunohistochemical processing: CD-31 (angiogenesis), IL-1 and TNF-α (proinflammatory cytokynes), iNOS (NO synthesis) and MMP-2 (collagen metabolism). The inflammation area, birefringence index, apoptotic index, immunoreactivity and vessel density were objectively measured.

RESULTS

Inflammatory reaction area at 4 days was 11.3, 15.2, 25.1, 17.1 and 19.3% of pure PP, PVA, GSNO 1, 10 and 70 mM, respectively, p = 0.0006 (PP × Others). At 30 days lower inflammatory area was observed in GSNO 10 and 70 mM compared to pure PP (5.3, 5.2 and 11.1%, respectively, p = 0.0001). Vessel density was higher for GSNO 1 mM (25.5%) compared to pure PP (19.6%) at 30 days only, p = 0.0081. Apoptotic index at 4 days was lower for GSNO 1 mM (49.3%) than pure PVA (60.6%), p = 0.0124. GSNO 10 and 70 mM reduced their apoptotic index at 30 days compared to 4 days (49.9 vs. 36.9 and 59.1 vs. 47.5%, respectively, p = 0.0397). Birefringence index, IL-1, TNF, MMP-2 and iNOS were not different.

CONCLUSIONS

Depending on concentrations, GSNO can increase angiogenesis, reduce inflammation and apoptosis compared to pure PP, without impact on cytokine, collagen organization/metabolism and endogenous NO synthesis.

Inducible nitric oxide synthase inhibition increases MMP-2 activity leading to imbalance between extracellular matrix deposition and degradation after polypropylene mesh implant

Prosthetic mesh implants are commonly used to correct abdominal wall defects. However, success of the procedure is conditioned by an adequate inflammatory response to the device. We hypothesized that nitric oxide produced by nitric oxide synthase 2 (NOS2) and MMP-2 and -9 participate in response induced by mesh implants in the abdominal wall and, consequently, affect the outcome of the surgical procedure. In the first step, temporal inflammatory markers profile was evaluated. Polypropylene meshes were implanted in the peritoneal side of the abdominal wall of C57Black mice. After 2, 4, 7, 15, and 30 days, tissues around the mesh implant were collected and inflammatory markers were analyzed. In the second step, NOS2 activity was inhibited with nitro-L-arginine methyl ester (L-NAME). Samples were collected after 15 days (when inflammation was reduced), and the inflammatory and tissue remodeling markers were investigated. Polypropylene mesh implant induced a pro-inflammatory environment mediated by intense MMP-2 and -9 activities, NO release, and interleukin-1β production peaking in 7 days and gradually decreasing after 15 days. NOS2 inhibition increased MMP-2 activity and resulted in a higher visceral adhesion incidence at the mesh implantation site when compared with non-treated animals that underwent the same procedure. We conclude that NOS2-derived NO is crucial for adequate response to polypropylene mesh implant integration in the peritoneum. NO deficiency results in an imbalance between extracellular matrix deposition/degradation contributing to visceral adhesions incidence.