Human monocyte activation by biologic and biodegradable meshes in vitro.

BACKGROUND: Inflammation and wound healing play critical roles in the integration of biologic and biodegradable meshes (BMs) at hernia repair sites. Monocytes/macrophages (M/MØs) are key cells controlling inflammation and wound healing. These cells release inflammatory cytokines and growth factors such as interleukin (IL)-1beta, IL-6, IL-8, and vascular endothelial growth factor (VEGF) upon activation. Although BMs have been increasingly used in hernia repairs worldwide, to date, investigations of inflammatory responses to various BMs have been limited. METHODS: Mesh samples of three acellular human dermis-derived biologic meshes (AlloDerm, AlloMax, FlexHD) and one biodegradable synthetic mesh (Bio-A) were placed in 96-well plates. Human peripheral blood mononuclear cells (PBMCs) were isolated from six healthy subjects, added to each well, and incubated for 7 days. Culture supernatants were assayed for IL-1beta, IL-6, IL-8, and VEGF levels using a multiplex bead-base immunoassay system (Bio-Plex). RESULTS: All four meshes induced cytokine expression from activated M/MØs to varying degrees in vitro. FlexHD induced significantly more IL-1beta (2,591 pg/ml) than AlloMax (517 pg/ml), AlloDerm (48 pg/ml), or Bio-A (28 pg/ml) (p < 0.001). AlloMax stimulated a significantly greater quantity of IL-6 (38,343 pg/ml) than FlexHD (19,317 pg/ml), Bio-A (191 pg/ml), or AlloDerm (103 pg/ml) (p < 0.05). Interleukin-8 and VEGF displayed trends similar to that of IL-6. There were no significant differences in cytokine production between AlloDerm and Bio-A. CONCLUSION: This study demonstrated that human macrophages are activated by human dermis-derived biologic and biodegradable meshes in vitro. A wide range of cytokine and growth factor induction was seen among the different mesh products. These differences in M/MØ activation may be related to the proprietary processing technologies of the studied meshes. The study results raise the possibility that these differences in M/MØ activation could indicate varying intensities of inflammation that control integration of different biologic meshes at the sites of hernia repair.

Enhancement of implantable glucose sensor function in vivo using gene transfer-induced neovascularization.

The in vivo failure of implantable glucose sensors is thought to be largely the result of inflammation and fibrosis-induced vessel regression at sites of sensor implantation. To determine whether increased vessel density at sites of sensor implantation would enhance sensor function, cells genetically engineered to over-express the angiogenic factor (AF) vascular endothelial cell growth factor (VEGF) were incorporated into an ex ova chicken embryo chorioallantoic membrane (CAM)-glucose sensor model. The VEGF-producing cells were delivered to sites of glucose sensor implantation on the CAM using a tissue-interactive fibrin bio-hydrogel as a cell support and activation matrix. This VEGF-cell-fibrin system induced significant neovascularization surrounding the implanted sensor, and significantly enhanced the glucose sensor function in vivo. This model system, for the first time, provides the "proof of principle" that increasing vessel density at the sites of implantation can enhance glucose sensor function in vivo, and demonstrates the potential of gene transfer and tissue interactive fibrin bio-hydrogels in the development of successful implants.

Ex ova chick chorioallantoic membrane as a novel model for evaluation of tissue responses to biomaterials and implants.

One of the major obstacles in developing rationale strategies to control inflammation and fibrosis surrounding implants is the lack of a simple and inexpensive in vivo model to screen tissue reactions to various biomaterials and implants. To begin to fill this gap, we have developed an ex ova model of the chick embryo chorioallantoic membrane (CAM) for testing of tissue reaction to biomaterials and implants. For these studies, we evaluated tissue reactions (inflammation and fibrosis) to two commonly used biomaterials (nylon and silastic) grossly and histologically in the ex ova CAM. Nylon mesh was incorporated within the CAM tissue 4 days postplacement. After 8 days postplacement, the nylon mesh was totally incorporated into the CAM. Histologically, little or no inflammation was seen associated with the incorporated nylon mesh at any time point. In the case of silastic tubing, significant incorporation of the CAM was seen grossly by 1-2 days postplacement. Incorporation of the tubing continued at day 8 postplacement of the silastic tubing, with ingrowth of the CAM into the lumen of the tubing. Histological evaluation of CAMs indicated that no significant tissue reactions (inflammation or fibrosis) occurred in the CAM tissue surrounding the silastic tubing or in the CAM tissue and vasculature that had grown into the silastic tubing. To our knowledge, this report represents the first investigation of the usage of the ex ova CAM model, a shell-less chick embryo model (ex ova), as an in vivo model to test the tissue reactions to biomaterials and implants.

Localization of the chemokine interleukin-8 and interleukin-8 receptors in human gingiva and cultured gingival keratinocytes.

Interleukin-8 (IL-8) has been implicated in a wide variety of diseases. Previous studies have demonstrated the expression of IL-8 in periodontal tissues, yet little is known about the exact source(s), mechanisms and factors involved in gingival expression of IL-8. Additionally, nothing is known about the presence and distribution of IL-8 receptors (IL-8R) in gingival cells. Therefore it was hypothesized that, in vivo, periodontal pathogens induce IL-8 expression from gingival keratinocytes (GK) which enhances leukocyte, microvascular endothelial cell (MVEC) and GK migration via specific IL-8 receptors present on these cells. The objective of the present study was to determine the distribution of IL-8 and IL-8R in gingival tissues and cultured human GK in vitro. Standard immunohistochemical and immunocytochemical techniques were utilized in order to localize IL-8 and its receptors CXCR-1 and CXCR-2 in archival gingival specimens (eight periodontitis and four non-inflamed controls) and in cultured gingival keratinocytes. It was demonstrated that, in vivo, IL-8 and IL-8R were present in gingival epithelium, MVEC and leukocytes. In vitro studies verified the above results, by showing expression of IL-8 and IL-8R in cultured gingival keratinocytes. It is concluded that IL-8 and IL-8 receptors are expressed in gingival epithelium both in vivo and in vitro. This new evidence indicates that epithelium plays a critical role in the host defense against invading pathogens and that keratinocytes can actively respond to IL-8 and other host cytokines, via specific receptors.