OBJECTIVETo investigate the use value of picrosirius red staining plus polarized microscopy to observe the dynamic changes of collagen fiber in lung fibrosis in silicotic mice model.

METHODSThe experimental mice were divided into control and quartz groups. 0.2 g/kg weight of quartz was injected intratracheally in quartz group. Lung tissues were collected at the 1st, 3rd, 5th, 7th, 14th and 28th day after injection respectively. Lung tissue slides were stained with picrosirius red. With the aid of polarized microscope, image analysis software, the distribution and change of type I and type III collagen could be qualitatively and quantitatively analyzed. Lung tissue hydroxyproline was determined by chloramines T method.

RESULTSIn early stage the predominant increment was type III collagen, but in late stage type I was predominant. The contents of both type collagen tended to increase as postexposure time prolonged. The time course of the ratio of type I to type III showed increasing trend, and there was a statistical significance on day 28 (1.49 +/- 0.39 vs 0.59 +/- 0.24, P < 0.05). The total area of collagen was positively correlated with hydroxyproline concentration of lung tissue (r(2) = 0.928 5, P < 0.01).

CONCLUSIONPicrosirius red staining combined with polarized microscopy and digital image processing is a useful method to elucidate collagen accumulation, distribution and subtype ratio in silicosis.