Synchrotron soft X-ray imaging and fluorescence microscopy reveal novel features of asbestos body morphology and composition in human lung tissues

Abstract

BackgroundOccupational or environmental exposure to asbestos fibres is associated with pleural and parenchymal lung diseases. A histopathologic hallmark of exposure to asbestos is the presence in lung parenchyma of the so-called asbestos bodies. They are the final product of biomineralization processes resulting in deposition of endogenous iron and organic matter (mainly proteins) around the inhaled asbestos fibres. For shedding light on the formation mechanisms of asbestos bodies it is of fundamental importance to characterize at the same length scales not only their structural morphology and chemical composition but also to correlate them to the possible alterations in the local composition of the surrounding tissues. Here we report the first correlative morphological and chemical characterization of untreated paraffinated histological lung tissue samples with asbestos bodies by means of soft X-ray imaging and X-Ray Fluorescence (XRF) microscopy, which reveals new features in the elemental lateral distribution.ResultsThe X-ray absorption and phase contrast images and the simultaneously monitored XRF maps of tissue samples have revealed the location, distribution and elemental composition of asbestos bodies and associated nanometric structures. The observed specific morphology and differences in the local Si, Fe, O and Mg content provide distinct fingerprints characteristic for the core asbestos fibre and the ferruginous body. The highest Si content is found in the asbestos fibre, while the shell and ferruginous bodies are characterized by strongly increased content of Mg, Fe and O compared to the adjacent tissue. The XRF and SEM-EDX analyses of the extracted asbestos bodies confirmed an enhanced Mg deposition in the organic asbestos coating.ConclusionsThe present report demonstrates the potential of the advanced synchrotron-based X-ray imaging and microspectroscopy techniques for studying the response of the lung tissue to the presence of asbestos fibres. The new results obtained by simultaneous structural and chemical analysis of tissue specimen have provided clear evidence that Mg, in addition to Fe, is also involved in the formation mechanisms of asbestos bodies. This is the first important step to further thorough investigations that will shed light on the physiopathological role of Mg in tissue response to the asbestos toxicity.

New insights on the biomineralisation process developing in human lungs around inhaled asbestos fibres

“…Secondary electron SEM images show that their overall diameter typically ranges between 1 and 4 μm, and their average length falls in the range between 20 and 120 μm. According to previous studies710, both optical microscopy (OM) and SEM images confirmed the typical features of the AB : their coating was often segmented along the fibre length into spaced spherical or ellipsoidal units, and often knobbed at the extremities716. SEM micrographs also show the inner crocidolite fibre in parts of the AB where the coating is interrupted (Figure S2 in the SI).…”

“…This would suggest that they were present as soluble species on the AB and then removed during the digestion with NaClO. While P and Ca have already been observed in the AB in previous works, claiming their active role in the biomineralization process1617, the presence of K associated with the fibres’ coating has never been directly observed before.…”

“…An interdisciplinary and multi-technique approach was followed: two synchrotron radiation based micro-probe techniques, namely micro X-Ray Fluorescence (μXRF) and micro X-ray Absorption Spectroscopy (μXAS), were combined with Scanning Electron Microscopy (SEM) and Elemental Dispersive Spectroscopy (EDS), and the results were interpreted taking in consideration altogether the mineralogical, geochemical, and biological aspects of the topic. With respect to the previous works exploiting similar synchrotron based techniques for this topic1617, this work focuses on elements heavier than Fe, and on the comparison between the composition of the AB isolated by the digestion of the biological tissue and those embedded in the original lung tissue.…”

Raw and thermally treated cement asbestos exerts different cytotoxicity effects on A549 cells in vitro

“…It is indeed already known that iron is largely responsible for the genotoxic and cytotoxic effects of asbestos fibers (Pascolo et al, 2011) by generating oxygen reactive species.…”

Towards a multi‐element silicon drift detector system for fluorescence spectroscopy in the soft X‐ray regime

“…Because those are the main constituents of organic matter, their detection may be of paramount importance when studying biological systems. [1][2][3][4][5][6][7][8][9] Although diffraction grating-based LEXRF possesses excellent energy resolution better than 0.2 eV at Al-L emission on Al metal, [10] its use is limited to narrow energy windows and to certain geometries. LEXRF systems relying on the intrinsic energy resolution of spectroscopic, solid-state X-ray detectors such as silicon drift detectors (SDDs) offer more flexibility and faster specimen mapping at the expenses of an inferior energy resolution.…”