A 3-dimensional in vitro model of epithelioid granulomas induced by high aspect ratio nanomaterials

Abstract

BackgroundThe most common causes of granulomatous inflammation are persistent pathogens and poorly-degradable irritating materials. A characteristic pathological reaction to intratracheal instillation, pharyngeal aspiration, or inhalation of carbon nanotubes is formation of epithelioid granulomas accompanied by interstitial fibrosis in the lungs. In the mesothelium, a similar response is induced by high aspect ratio nanomaterials, including asbestos fibers, following intraperitoneal injection. This asbestos-like behaviour of some engineered nanomaterials is a concern for their potential adverse health effects in the lungs and mesothelium. We hypothesize that high aspect ratio nanomaterials will induce epithelioid granulomas in nonadherent macrophages in 3D cultures.ResultsCarbon black particles (Printex 90) and crocidolite asbestos fibers were used as well-characterized reference materials and compared with three commercial samples of multiwalled carbon nanotubes (MWCNTs). Doses were identified in 2D and 3D cultures in order to minimize acute toxicity and to reflect realistic occupational exposures in humans and in previous inhalation studies in rodents. Under serum-free conditions, exposure of nonadherent primary murine bone marrow-derived macrophages to 0.5 μg/ml (0.38 μg/cm2) of crocidolite asbestos fibers or MWCNTs, but not carbon black, induced macrophage differentiation into epithelioid cells and formation of stable aggregates with the characteristic morphology of granulomas. Formation of multinucleated giant cells was also induced by asbestos fibers or MWCNTs in this 3D in vitro model. After 7-14 days, macrophages exposed to high aspect ratio nanomaterials co-expressed proinflammatory (M1) as well as profibrotic (M2) phenotypic markers.ConclusionsInduction of epithelioid granulomas appears to correlate with high aspect ratio and complex 3D structure of carbon nanotubes, not with their iron content or surface area. This model offers a time- and cost-effective platform to evaluate the potential of engineered high aspect ratio nanomaterials, including carbon nanotubes, nanofibers, nanorods and metallic nanowires, to induce granulomas following inhalation.

Three dimensionalde novomicro bone marrow and its versatile application in drug screening and regenerative medicine

“…This 3D system can serve as a tool to evaluate the potential risk of some engineered nanomaterials in inducing granulomas in lungs or mesothelium. 93 Osteoarthritis is a degenerative disease of bone and cartilage. 94 Over the years, scientists have used MSCs as the main material for the constructs used to study osteoarthritis because of their ability to differentiate into osteocytes and chondrocytes.…”

Biological interactions and safety of graphene materials

“…Feng and Liu 14 reported that nanoscale PEG-coated GO sheets initially accumulated in these organs and were then gradually excreted with no indication of toxicity after three months. 67 On the other hand, Wang et al 62 and Zhang et al 68 reported that intravenous injection of uncoated GO sheets induced granulomas in the lungs, 62,68 liver, spleen, and kidneys at a dose of 0.4 mg per mouse.…”

“…In general, graphene materials vary greatly in number of layers, lateral dimensions, and surface chemistry and are best regarded as a family of related materials, whose biological responses will vary much as they do across the carbon nanotube family. 12–14 The structure–property variations in these graphene-family nanomaterials (GFNs) present significant challenges for the field of nanotoxicology, but also open up the potential for influencing safety through material design. 12 At the same time, this material family offers potential opportunities for biological applications such as drug delivery.…”

In-vitro toxicology of respirable iron-rich particles relevant to mining industry: a high throughput framework for interpreting environmental particulate matter toxicity

“…Granuloma formation was determined to correlate better with MWCNT length and complexity than surface-area and iron content. The development of multinucleated giant cells was also observed 202 . Experiments with MWCNT in-vivo show increased connective tissue thickness in the alveolar septa of up to 75% in 56 days, in single aspiration doses as low as 80 µg in mice 203 , while nanotubes which are not rigid or are tangled may have diminished fibrotic potential (see Figure 8) 127 .…”

“…exposures 202,229,233,270,271 , although the w/v relationship holds proportionally so long as the well area and media volume are constant.…”