Impact of Proinflammatory Cytokine Knockout on Mesh Integration

Methacrylic Acid Copolymer Coating Enhances Constructive Remodeling of Polypropylene Mesh by Increasing the Vascular Response

This study reports that a methacrylic acid (MAA)-based copolymer coating generates constructive remodeling of polypropylene (PP) surgical mesh in a subcutaneous model. This coating is non-bioresorbable and follows the architecture of the mesh without impeding connective tissue integration. Following implantation, the tissue response is biased toward vascularization instead of fibrosis. The vessel density around the MAA mesh is double that of the uncoated mesh two weeks after implantation. This initial vasculature regresses after two weeks while mature vessels remain, suggesting an enhanced healing response. Concurrently, the MAA coating alters the foreign body response to the mesh. Fewer infiltrating cells, macrophages, and foreign body giant cells are found at the tissue-material interface three weeks after implantation. The coating also dampens inflammation, with lower expression levels of pro-inflammatory and fibrogenic signals (e.g., Tgf-β1, Tnf-α, and Il1-β) and similar expression levels of anti-inflammatory cytokines (e.g., Il10 and Il6) compared to the uncoated mesh. Contrary to other coatings that aim to mitigate the foreign body response to PP mesh, a MAA coating does not require the addition of any biological agents to have an effect, making the coated mesh an attractive candidate for soft tissue repair.

Host inflammatory response to polypropylene implants: insights from a quantitative immunohistochemical and birefringence analysis in a rat subcutaneous model

Objectives

To describe acute and sub acute aspects of histological and immunohistochemical response to PP implant in a rat subcutaneous model based on objective methods.

Materials and Methods

Thirty rats had a PP mesh subcutaneously implanted and the same dissection on the other side of abdomen but without mesh (sham). The animals were euthanized after 4 and 30 days. Six slides were prepared using the tissue removed: one stained with hematoxylin-eosin (inflammation assessment); one unstained (birefringence evaluation) and four slides for immunohistochemical processing: IL-1 and TNF-α (pro-inflammatory cytokines), MMP-2 (collagen metabolism) and CD-31 (angiogenesis). The area of inflammation, the birefringence index, the area of immunoreactivity and the number of vessels were objectively measured.

Results

A larger area of inflammatory reaction was observed in PP compared to sham on the 4th and on the 30^th day (p=0.0002). After 4 days, PP presented higher TNF (p=0.0001) immunoreactivity than sham and no differences were observed in MMP-2 (p=0.06) and IL-1 (p=0.08). After 30 days, a reduction of IL-1 (p=0.010) and TNF (p=0.016) for PP and of IL-1 (p=0.010) for sham were observed. Moreover, area of MMP-2 immunoreactivity decreased over time for PP group (p=0.018). Birefringence index and vessel counting showed no differences between PP and sham (p=0.27 and p=0.58, respectively).

Conclusions

The implantation of monofilament and macroporous polypropylene in the subcutaneous of rats resulted in increased inflammatory activity and higher TNF production in the early post implant phase. After 30 days, PP has similar cytokines immunoreactivity, vessel density and extracellular matrix organization.

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.

Sleep fragmentation in mice induces nicotinamide adenine dinucleotide phosphate oxidase 2-dependent mobilization, proliferation, and differentiation of adipocyte progenitors in visceral white adipose tissue

BACKGROUND

Chronic sleep fragmentation (SF) without sleep curtailment induces increased adiposity. However, it remains unclear whether mobilization, proliferation, and differentiation of adipocyte progenitors (APs) occurs in visceral white adipose tissue (VWAT), and whether nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (Nox2) activity plays a role.

METHODS

Changes in VWAT depot cell size and AP proliferation were assessed in wild-type and Nox2 null male mice exposed to SF and control sleep (SC). To assess mobilization, proliferation, and differentiation of bone marrow mesenchymal stem cells (BM-MSC), Sca-1+ bone marrow progenitors were isolated from GFP+ or RFP+ mice, and injected intravenously to adult male mice (C57BL/6) previously exposed to SF or SC.

RESULTS

In comparison with SC, SF was associated with increased weight accrual at 3 w and thereafter, larger subcutaneous and visceral fat depots, and overall adipocyte size at 8 w. Increased global AP numbers in VWAT along with enhanced AP BrDU labeling in vitro and in vivo emerged in SF. Systemic injections of GFP+ BM-MSC resulted in increased AP in VWAT, as well as in enhanced differentiation into adipocytes in SF-exposed mice. No differences occurred between SF and SC in Nox2 null mice for any of these measurements.

CONCLUSIONS

Chronic sleep fragmentation (SF) induces obesity in mice and increased proliferation and differentiation of adipocyte progenitors (AP) in visceral white adipose tissue (VWAT) that are mediated by increased Nox2 activity. In addition, enhanced migration of bone marrow mesenchymal stem cells from the systemic circulation into VWAT, along with AP differentiation, proliferation, and adipocyte formation occur in SF-exposed wild-type but not in oxidase 2 (Nox2) null mice. Thus, Nox2 may provide a therapeutic target to prevent obesity in the context of sleep disorders.

Association between the markers of FIRS and the morphologic alterations in the liver of neonates autopsied in the perinatal period

Markers of fetal inflammatory response syndrome (FIRS) can influence the morphologic alterations in liver of autopsied neonates. The IL-6, TNF-α, and C-reactive protein (CRP) expression in liver fragments were marked by immunohistochemistry and the intensity of steatosis, percentage of fibrosis, and the number of foci of extramedullary erythropoiesis were evaluated. The degree of steatosis correlated positively with IL-6 (p = 0.06), positively with CRP (p ≤ 0.001), and negatively with TNF-α (p = 0.06). The collagen percentage correlated positively with IL-6 (p = 0.055) and positively with TNF-α (p ≤ 0.001). Erythropoiesis correlated positively with IL-6 (p ≤ 0.001) and negatively with CRP (p = 0.00754). The analyzed markers of FIRS have an important role in triggering hepatic morphologic alterations.

Comparison of long-term biocompability of PVDF and PP meshes

BACKGROUND

Abdominal hernia repair is the most frequently performed operation in surgery. Mesh repair in hernia surgery has become an integral component. Although meshes made of PVDF are already in clinical use, so far no data of long-term biocompability are available.

METHODS

In this study a PVDF mesh was compared to a polypropylene mesh with regard to its long-term biocompatibility. A total of 28 rats were randomized to two groups. Mesh material was implanted subcutaneously; animals were euthanized seven days and six months postoperatively. The quantity of inflammatory tissue response was characterized by measuring the diameter of the foreign body granuloma. Furthermore quality of cellular immune response (T-lymphocytes, macrophages, and neutrophils), and inflammation (COX-2) was analyzed by immunohistochemistry. Furthermore the collagen type I/III ratio was determined.

RESULTS

Macrophages, T-lymphocytes, neutrophiles, and COX-2 declined significantly up to six months postoperatively in comparison to day 7 for both PVDF and PP meshes, and in both groups the collagen ratio increased significantly in the course of time. PVDF meshes showed a foreign body granuloma size significantly reduced compared to PP (7 days: 20 ± 2 μm vs. 27 ± 2 μm; 6 months 15 ± 2 μm vs. 22 ± 3 μm; p < .001). However no significant differences were found analyzing cellular response six months postoperatively.

CONCLUSIONS

Our current data suggest that even in the long-term course after six months and despite a higher effective surface of the PVDF samples it showed a smaller foreign body granuloma than with PP whereas the cellular response was similar.

Polypropylene mesh and the host response

The use of polypropylene (PP) mesh for pelvic floor repair has been increasing dramatically over the past decade; however, tissue response in humans has not been extensively studied. This review discusses PP mesh and postimplantation host tissue response. Emphasis is placed on studies investigating the relationship between individual mesh properties and specific responses. There is an immediate inflammatory response after PP mesh implantation that lays the framework for tissue ingrowth and subsequent mesh integration. This response varies based on physical properties of individual mesh, such as pore size, weight, coatings, bacterial colonization, and biofilm production.

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

Prosthetic meshes are commonly used to correct abdominal wall defects. However, the inflammatory reaction induced by these devices in the peritoneum is not completely understood. We hypothesized that nitric oxide (NO), produced by nitric oxide synthase 2 (NOS2) may modulate the response induced by mesh implants in the abdominal wall and, consequently, affect the outcome of the surgical procedure. Polypropylene meshes were implanted in the peritoneal side of the abdominal wall in wild-type and NOS2-deficient (NOS2(-/-)) mice. After 15 days tissues around the mesh implant were collected, and inflammatory markers (the cytokine interleukin 1β (IL-1β) and NO) and tissue remodeling (collagen and metalloproteinases (MMP) 2 and 9) were analyzed. The lack of NOS2-derived NO induced a higher incidence of visceral adhesions at the mesh implantation site compared with wild-type mice that underwent the same procedure (P<0.05). Additionally, higher levels of IL-1β were present in the mesh-implanted NOS2(-/-) animals compared with control and wild-type mice. Mesh implantation induced collagen I and III deposition, but in smaller amounts in NOS2(-/-) mice. MMP-9 activity after the surgical procedure was similarly increased in both groups. Conversely, MMP-2 activity was unchanged in mesh-implanted wild-type mice, but was significantly increased in NOS2(-/-) mice (P<0.01), due to decreased S-nitrosylation of the enzyme in these animals. We conclude that NOS2-derived NO is crucial for an adequate response to and integration of polypropylene mesh implants in the peritoneum. NO deficiency results in a prolonged inflammatory reaction to the mesh implant, and reduced collagen deposition may contribute to an increased incidence of visceral adhesions.