Induction of immune gene expression and inflammatory mediator release by commonly used surgical suture materials: an experimental in vitro study

Abstract

Background: Surgeons have a range of materials to choose from to complete wound closure, yet surprisingly very little is still known about the body's immune response to the suture materials in current use. The growing literature of adverse suture material reactions provided the objective of this study, to use in vitro assays to quantify levels of inflammation produced by seven commonly used suture materials in surgical procedures.

Methods: Human monocyte/macrophage THP-1 cells were exposed to suture materials for 1, 3 and 5 days. Gene expression and protein secretion of six inflammatory cytokines and two cell surface markers were assessed using qPCR and ELISA respectively, with LPS exposure providing a positive control. Furthermore, a IL-1β/IL-1RA marker ratio was assessed to determine the balance between pro-/anti-inflammatory expression.

Results: The findings from our in vitro study suggest that four commonly used suture materials cause upregulation of pro-inflammatory markers indicative of an early foreign body reaction, with no balance from anti-inflammatory markers.

Conclusions: As prolonged early pro-inflammation is known to produce delayed wound healing responses, the knowledge produced from this study has potential to improve informed surgical decision making and patient safety. This work has the capability to reduce suture-related adverse immune reactions, and therefore positively affect patient outcomes.

Keywords: Immune response; In vitro; Suture materials; Wound closure.

Fig. 1

a Gene Expression Results. Relative gene expression of five pro-inflammatory markers (four cytokines (IL-1β, IL-1α, TNFα and IL-8) and one cell surface marker (CCR7)) from THP-1 cells in contact with a variety of suture materials were measured by RT-PCR on days 1, 3 and 5. The most representative independent biological repeat is reported ± SEM. Statistical analysis was performed using two-way ANOVA and post-hoc Dunnett’s test (*p < 0.05, **p < 0.01, ***p < 0.001), ****p < 0.0001). b Gene Expression Results. Relative gene expression of three anti-inflammatory markers (two cytokines (TGFβ1 and IL-1RA) and one cell surface marker (CD163)) from THP-1 cells in contact with a variety of suture materials were measured by RT-PCR on days 1, 3 and 5. The most representative independent biological repeat is reported ± SEM. Statistical analysis was performed using two-way ANOVA and post-hoc Dunnett’s test (*p < 0.05, **p < 0.01, ***p < 0.001), ****p < 0.0001)

Fig. 2

Pro-/Anti-Inflammatory Marker Ratio. A pro-/anti-inflammatory marker ratio was produced for all sutures, by dividing the value for fold-increase in IL-1β gene expression, by the value for fold-increase in IL-1RA gene expression, over all time points

Fig. 3

Protein Secretion Results. The concentration of IL-1β protein released by THP-1 cells into media, in response to culture with the suture materials, was measured using ELISA on days 1, 3 and 5. Means from three independent biological repeats is reported ± SEM. Statistical analysis was performed using two-way ANOVA and post-hoc Dunnett’s test (*p < 0.05)