Bulk- and nano-scale titanium dioxide (TiO2) has found use in human food products for controlling color, texture, and moisture. Once ingested, and because of their small size, nano-scale TiO2 can interact with a number of epithelia that line the human gastrointestinal tract. One such epithelium responsible for nutrient absorption is the small intestine, whose constituent cells contain microvilli to increase the total surface area of the gut. Using a combination of scanning and transmission electron microscopy it was found that food grade TiO2 (E171 food additive coded) included ∼25% of the TiO2 as nanoparticles (NPs; <100 nm), and disrupted the normal organization of the microvilli as a consequence of TiO2 sedimentation. It was found that TiO2 isolated from the candy coating of chewing gum and a commercially available TiO2 food grade additive samples were of the anatase crystal structure. Exposure to food grade TiO2 additives, containing nanoparticles, at the lowest concentration tested within this experimental paradigm to date at 350 ng/mL (i.e., 100 ng/cm(2) cell surface area) resulted in disruption of the brush border. Through the use of two independent techniques to remove the effects of gravity, and subsequent TiO2 sedimentation, it was found that disruption of the microvilli was independent of sedimentation. These data indicate that food grade TiO2 exposure resulted in the loss of microvilli from the Caco-2BBe1 cell system due to a biological response, and not simply a physical artifact of in vitro exposure.

Transporting epithelial cells optimize their morphology for solute uptake by building an apical specialization: a dense array of microvilli that serves to increase membrane surface area. In the intestinal tract, individual cells build thousands of microvilli, which pack tightly to form the brush border. Recent studies implicate adhesion molecule CDHR2 in the regulation of microvillar packing via the formation of adhesion complexes between the tips of adjacent protrusions. To gain insight on how CDHR2 contributes to brush border morphogenesis and enterocyte function under native in vivo conditions, we generated mice lacking CDHR2 expression in the intestinal tract. Although CDHR2 knockout (KO) mice are viable, body weight trends lower and careful examination of tissue, cell, and brush border morphology revealed several perturbations that likely contribute to reduced functional capacity of KO intestine. In the absence of CDHR2, microvilli are significantly shorter, and exhibit disordered packing and a 30% decrease in packing density. These structural perturbations are linked to decreased levels of key solute processing and transporting factors in the brush border. Thus, CDHR2 functions to elongate microvilli and maximize their numbers on the apical surface, which together serve to increase the functional capacity of enterocyte.

The subfamily of b2 integrins is implicated in macrophage fusion, a hallmark of chronic inflammation. Among b2 family members, integrin Mac-1 (a M b 2 , CD11b/CD18) is abundantly expressed on monocyte/ macrophages and mediates critical adhesive reactions of these cells. However, the role of Mac-1 in macrophage fusion leading to the formation of multinucleated giant cells remains unclear. Moreover, the role of integrin a D b 2 (CD11d/CD18), a receptor with recognition specificity overlapping that of Mac-1, is unknown. We found that multinucleated giant cells are formed in the inflamed mouse peritoneum during the resolution phase of inflammation, and their numbers were approximately twofold higher in wild-type mice than in Mac-1 À/À mice. Analyses of isolated inflammatory peritoneal macrophages showed that IL-4einduced fusion of Mac-1edeficient cells was strongly reduced compared with wild-type counterparts. The examination of adhesive reactions known to be required for fusion showed that spreading, but not adhesion and migration, was reduced in Mac-1edeficient macrophages. Fusion of a D b 2 -deficient macrophages was also significantly decreased, albeit to a smaller degree. Deficiency of intercellular adhesion molecule 1, a counter-receptor for Mac-1 and a D b 2 , did not alter the fusion rate. The results indicate that both Mac-1 and a D b 2 support macrophage fusion with Mac-1 playing a dominant role and suggest that Mac-1 may mediate cell-cell interactions with a previously unrecognized counter-receptor(s). (Am J Pathol 2016, 186: 2105e2116; http:// dx

Little information is available regarding the suitability of analytical methods to evaluate claims regarding the presence of engineered nanomaterials (NMs) in consumer products, their potential toxic effects to humans, or their life cycle after product use. This study was designed to assess the potential interactions across the life cycle of eight commercially available dietary supplement drinks from a single vendor, all purported to contain metal NMs. Analysis showed that all of the products contained metallic NMs with average diameters below 50 nm as determined by dynamic light scattering and transmission electron microscopy. The products' intended use is human ingestion; in order to examine potential human health effects after ingestion, we investigated the interaction of NMs in the drinks with an in vitro cell system that faithfully mimics human intestinal cells. After exposure to concentrations of NMs as low as 3.5 μg/mL, we found that the number of microvilli decreased relative to untreated controls for all drinks. From a life cycle perspective, consumption of drinks containing NMs will eventually result in sewer discharge of these NMs in feces. Screening tests for NM removal by biosolids in wastewater treatment plants (WWTPs) conducted using the NMs contained in supplement drinks showed variable removal of NMs, with the fractions removed ranging from (99 ± 27)% to (30 ± 0.05)%. The results showed that metal NM-based supplements may have an effect on the number of viable human intestinal microvilli and will likely enter the environment via either water or solids released from WWTPs.

Implantation of synthetic material, including vascular grafts, pacemakers, etc. results in the foreign body reaction and the formation of multinucleated giant cells (MGCs) at the exterior surface of the implant. Despite the long-standing premise that fusion of mononucleated macrophages results in the formation of MGCs, to date, no published study has shown fusion in context with living specimens. This is due to the fact that optical-quality glass, which is required for the majority of live imaging techniques, does not promote macrophage fusion. Consequently, the morphological changes that macrophages undergo during fusion as well as the mechanisms that govern this process remain ill-defined. In this study, we serendipitously identified a highly fusogenic glass surface and discovered that the capacity to promote fusion was due to oleamide contamination. When adsorbed on glass, oleamide and other molecules that contain long-chain hydrocarbons promoted high levels of macrophage fusion. Adhesion, an essential step for macrophage fusion, was apparently mediated by Mac-1 integrin (CD11b/CD18, αMβ2) as determined by single cell force spectroscopy and adhesion assays. Micropatterned glass further increased fusion and enabled a remarkable degree of spatiotemporal control over MGC formation. Using these surfaces, we reveal the kinetics that govern MGC formation in vitro. We anticipate that the spatiotemporal control afforded by these surfaces will expedite studies designed to identify the mechanism(s) of macrophage fusion and MGC formation with implication for the design of novel biomaterials.