Micro-CT imaging as a method for comparing perfusion in graduated-height and single-height surgical staple lines.

BACKGROUND: Wound healing is a goal for advanced technology in the surgical space to benefit clinical outcomes. Surgical staplers are commonly used in a variety of open and minimally invasive abdominal and thoracic procedures. Assessment of wound healing traits, such as perfusion, has been challenging due to technical limitations. A novel technique that utilizes micro-computed tomography methodology to measure perfusion was designed to compare the micro-perfusion of staple lines between commercial stapler reloads that employ different staple height strategies. MATERIALS AND METHODS: Following an Institutional Animal Care and Use Committee-approved protocol, rats were euthanized and immediately heparinized prior to a subtotal gastrectomy with either graduated-height or single-height staples. Rats were then perfused with barium, following which stomachs were removed and immediately fixed in formalin to prevent degradation. Stomachs were then imaged using micro-computed tomography and subsequent analysis was utilized to quantify fluid volume and patent vasculature proximity to staples within the staple line region for each group. RESULTS: Average perfusion volume was significantly higher with graduated-height staples (0.33% ± 0.18%) compared to single-height staples (0.16% ± 0.09%, P=0.011). Average vessel-to-staple line distance was not significant but trended lower with graduated-height staples (0.35±0.02 mm) compared to single-height staples (0.36±0.03 mm, P=0.18). DISCUSSION: Graduated-height staples had significantly higher perfusion volume than single-height staples, which likely has a downstream benefit on wound healing and clinical outcomes. CONCLUSION: This study shows a higher perfusion volume around the staple lines using graduated-height staples as compared to single-height staples and this may contribute to better wound healing in patients.

Ex vivo pneumostasis evaluation of a variable-height staple design.

OBJECTIVE: This study examined the effect of using a variable-height staple construct containing three rows of staples with heights of 3.0, 3.5, and 4.0 mm (staple leg length, medial to lateral) versus standard three-row single-height staplers (with staple heights of either 3.5 or 4.8 mm) for pneumostasis in healthy porcine and canine lung parenchyma to determine whether a single stapler that uses variable staple heights could perform as well as, or better than, existing single-height stapling devices. The work presented here used healthy animal tissues, in lieu of diseased tissue, which is extremely difficult to obtain and quantify. METHODS: Briefly, fresh explanted porcine and canine trachea-lung blocs were used for all testing. Tissue thicknesses were measured with a custom-design spring-loaded caliper before stapling with control and test articles to ensure that the tissue was of "appropriate" thickness for the stapler size (staple height) selected (per manufacturer's instructions for use). All tissue measurements were comparable across each area of lung tested, and both test and control devices were fired into the same tissue thicknesses. After stapling, the lungs were submerged in water, insufflated, checked for air leaks at four discrete (increasing) pressures, and scored using a predetermined scale. Statistical analysis was performed for n = 26 (3.5-mm staples), n = 29 (4.8-mm staples), and n = 26 or 29 (paired to the standard group) for the variable-height stapler (3.0-, 3.5-, and 4.0-mm staples). RESULTS: The results demonstrated that the test article comprising three rows of variable-height staples provided comparable pneumostasis with the standard three-row single-height staplers (with staple heights of either 3.5 or 4.8 mm) under the test conditions described. CONCLUSIONS: A novel test article containing three rows of staples with heights of 3.0, 3.5, and 4.0 mm (variable-height stapler) showed promising results when compared with standard commercially available single-height staplers, performing as well as or better than the standard single-height staplers. This work demonstrates important first steps to proving equivalent device performance, which might facilitate the use of a variable-height stapler in place of multiple single-height staplers.

Phenotypic non-equivalence of murine (monocyte-) macrophage cells in biomaterial and inflammatory models.

Cells of the mononuclear phagocytic system including monocytes and macrophages (e.g., pooled human monocytes, bone marrow-derived macrophages, etc.) are often employed for in vitro assessment of novel biomaterials and to assay anti-inflammatory drug activity. In this context, numerous macrophage cells are treated interchangeably in the literature despite a lack of demonstrated equivalence among immortalized cell lines and further, between cell lines and primary-derived macrophages of different species. Three murine (monocyte-) macrophage cell lines (IC-21, J774A.1, and RAW 264.7), commonly utilizedin biomaterial and pharmaceutical screening research, have been compared with primary-derived murine bone marrow macrophages. Significant differences were discovered in the expression of cell surface proteins requisite for cell adhesion and activation among cell lines and primary-derived cells as well as between the different cell lines. Results demonstrate activation but with reduced cytokine expression to chemical stimulus (lipopolysaccharide) by cell lines compared with that of primary-derived macrophages. Limited correlation between cultured primary and immortalized cells in cytokine production, phenotype and intrinsic activation states has relevance to fidelity for in vitro testing. These differences warrant justification for selection of various cell lines for specific assay purposes, and merit caution if comparisons to primary cell types (i.e., for biocompatibility) are required.

Macrophage Serum-Based Adhesion to Plasma-Processed Surface Chemistry is Distinct from That Exhibited by Fibroblasts.

Plasma-polymerized films deposited from AlAm, HxAm, NVP, NVFA, AA and FC were compared to TCPS and PS surfaces in supporting cellular attachment, viability, and proliferation in serum-based culture in vitro for extended periods of time (>7 d). Surface patterns were created using multi-step depositions with physical masks. Cell adhesion in the presence of serum was compared for (monocyte-) macrophage and fibroblast cell lines. Cellular response was tracked over time, reporting adhesive behavior, proliferative rates, and morphological changes as a function of surface chemistry. Micropatterned surfaces containing different surface chemistries and functional groups (e.g. -NH(2), -COOH, -CF(3)) produced differential cell adhesive patterns for NIH 3T3 fibroblasts compared to J774A.1, RAW 264.7 or IC-21 (monocyte-) macrophage cell types. Significantly, macrophage adhesion is substantial on surfaces where fibroblasts do not adhere under identical culture conditions.

Enzyme function of the globin dehaloperoxidase from Amphitrite ornata is activated by substrate binding.

Amphitrite ornata dehaloperoxidase (DHP) is a heme enzyme with a globin structure, which is capable of oxidizing para-halogenated phenols to the corresponding quinones. Cloning, high-level expression, and purification of recombinant DHP are described. Recombinant DHP was assayed by stopped-flow experiments for its ability to oxidatively debrominate 2,4,6-tribromophenol (TBP). The enzymatic activity of the ferric form of recombinant DHP is intermediate between that of a typical peroxidase (horseradish peroxidase) and a typical globin (horse heart myoglobin). The present study shows that, unlike other known peroxidases, DHP activity requires the addition of substrate, TBP, prior to the cosubstrate, peroxide. The presence of a substrate-binding site in DHP is consistent with a two-electron oxidation mechanism and an obligatory order for activation of the enzyme by addition of the substrate prior to the cosubstrate.

Morphology and growth of murine cell lines on model biomaterials.

All biomaterial implants are assaulted by the host "foreign body" immune response. Understanding the complex, dynamic relationship between cells, biomaterials and milieu is an important first step towards controlling this reaction. Material surface chemistry dictates protein adsorption, and thus subsequent cell interactions. The cell-implant is a microenvironment involving 1) proteins that coat the surface and 2) cells that interact with these proteins. Macrophages and fibroblasts are two cell types that interact with proteins on biomaterials surfaces and play different related, but equally important, roles in biomaterials rejection and implant failure. Growth characteristics of four murine cell lines on model biomaterials surfaces were examined. Murine monocyte-macrophages (RAW 264.7 and J774A.1), murine macrophage (IC-21) and murine fibroblast (NIH 3T3) cell lines were tested to determine whether differences exist in adhesion, proliferation, differentiation, spreading, and fusion (macrophage lineages only) on these surfaces. Differences were observed in the ability of cells to adhere to and subsequently proliferate on polymer surfaces. (Monocyte-) macrophages grew well on all surfaces tested and growth rates were measured on three representative polymer biomaterials surfaces: tissue culture polystyrene (TCPS), polystyrene, and Teflon-AF. J774A.1 cultures grown on TCPS and treated with exogenous cytokines IL-4 and GM-CSF were observed to contain multinucleate cells with unusual morphologies. Thus, (monocyte-) macrophage cell lines were found to effectively attach to and interrogate each surface presented, with evidence of extensive spreading on Teflon-AF surfaces, particularly in the IC-21 cultures. The J774A.1 line was able to proliferate and/or differentiate to more specialized cell types (multinucleate/dendritic-like cells) in the presence of soluble chemokine cues.