Insulin treatment directly restores neutrophil phagocytosis and bactericidal activity in diabetic mice and thereby improves surgical site Staphylococcus aureus infection.

Bacterial infections, including surgical site infections (SSI), are a common and serious complication of diabetes. Staphylococcus aureus, which is eliminated mainly by neutrophils, is a major cause of SSI in diabetic patients. However, the precise mechanisms by which diabetes predisposes to staphylococcal infection are not fully elucidated. The effect of insulin on this infection is also not well understood. We therefore investigated the effect of insulin treatment on SSI and neutrophil function in diabetic mice. S. aureus was inoculated into the abdominal muscle in diabetic db/db and high-fat-diet (HFD)-fed mice with or without insulin treatment. Although the diabetic db/db mice developed SSI, insulin treatment ameliorated the infection. db/db mice had neutrophil dysfunction, such as decreased phagocytosis, superoxide production, and killing activity of S. aureus; however, insulin treatment restored these functions. Ex vivo treatment (coincubation) of neutrophils with insulin and euglycemic control by phlorizin suggest that insulin may directly activate neutrophil phagocytic and bactericidal activity independently of its euglycemic effect. However, insulin may indirectly restore superoxide production by neutrophils through its euglycemic effect. HFD-fed mice with mild hyperglycemia also developed more severe SSI by S. aureus than control mice and had impaired neutrophil phagocytic and bactericidal activity, which was improved by insulin treatment. Unlike db/db mice, in HFD mice, superoxide production was increased in neutrophils and subsequently suppressed by insulin treatment. Glycemic control by insulin also normalized the neutrophil superoxide-producing capability in HFD mice. Thus, insulin may restore neutrophil phagocytosis and bactericidal activity, thereby ameliorating SSI.

Novel technique of overlaying a poly-L: -lactic acid nanosheet for adhesion prophylaxis and fixation of intraperitoneal onlay polypropylene mesh in a rabbit model.

BACKGROUND: One problem with polypropylene mesh (PPM) used to repair abdominal wall hernias is dense adhesions to the visceral surface. The authors developed the biocompatible poly-L: -lactic acid (PLLA) nanosheet (thickness < 100 nm), which has the unique ability to adhere tightly to tissues but not to opposing tissues. This study investigated the antiadhesive and fixative characteristics of the PLLA nanosheet after placement of intraperitoneal onlay PPM (IPOM) overlaid with a PLLA nanosheet on intact peritoneum. METHODS: The PLLA nanosheet was fabricated by the spin-coating method and peeling technique with polyvinyl alcohol (PVA) as a supporting film. Two 1.5-cm-square pieces of mesh were implanted on each peritoneal side of the midline incision. The mesh was fixed to the peritoneum with a suture and then overlaid with a 4-cm-square piece of Seprafilm or nanosheet. To examine the fixative property, mesh was overlaid with Seprafilm or nanosheet without a fixed suture. After 4 weeks, mesh adhesion, inflammatory reaction, fixation, and dislocation of mesh were evaluated. RESULTS: Nanosheet-overlaid meshes were flexible and fit over the peritoneum. Adhesion was observed in 10% of the nanosheet-overlaid meshes and in 50% of the Seprafilm-overlaid meshes. The adhesion tenacity grade was significantly lower with the nanosheet-overlaid meshes (0.1 ± 0.1) than with the Seprafilm-overlaid meshes (1.0 ± 0.4) (p = 0.029), and the percentage of the adhesion area also was lower with the nanosheet-overlaid meshes (1.0 ± 1.0% vs 8.5 ± 3.2%; p = 0.037). The mean inflammatory cell counts were lower with the nanosheet-overlaid meshes (p = 0.0023). Regarding the fixative property, 37.5% of the nanosheet-overlaid meshes were fixated on the peritoneum, but no Seprafilm-overlaid mesh was fixated. CONCLUSION: Overlaying of a PLLA nanosheet was effective for adhesion prophylaxis of intraperitoneal mesh. It also may have a possible beneficial effect on fixation of mesh.