The body's response to inadvertent implants: Respirable particles in lung tissues

Instillation of respirable glass fibers to rat lungs served as an in vivo m odel for the detection and evaluation of differential local biological resp onses to particulate matter in the deep lung. Three compositions of vitreou s glass, stonewool. and refractory fiber materials (MMVF 10, HT. and RCF1a) were harvested viith surrounding lung tissues and examined both histologic ally and by physical/chemical assays to correlate the observed differential dissolution events with specific biological responses associated with each material. Specimens at 2-days. 7-days, 30-days and 90-days post-instillati on were compared from at least three rats for each condition and for phosph ate-buffered-saline: controls. HT fiber surface and bulk chemistry uniquely allowed direct histochemical visualization of fiber degradation steps by P russian Blue staining, while multiple attenuated internal reflection infrar ed spectroscopy and energy-dispersive X-ray analysis of unfixed, fresh lung robe slice surfaces revealed the concurrent biochemical changes, Insulatio n glass (MMVF 10) dissolved most quickly in extracellular compartments, as well as after phagocytosis of small fragments, stonewool (HT) was externall y thinned by surrounding phagocytes and fragmented into shorter lengths eng ulfable by macrophages; refractory ceramic (RCF1a) resisted both external d issolution and macrophage uptake, becoming embedded in granulomatous nodule s. it is clear from these results that the lung can process inadvertently r espired particulates in different ways dependent on the specific compositio ns of the particles. The animal model and analytical scheme reported here also show substantial promise for evaluating the effects of bioaerosols, and synergistic effects of respirable toxins with particulates, and consequences of dental aspirate s into the lung.