The significance of hyperplastic alveolar type II cells in the pathogenesis of early stage of experimental silicosis

Objective To elucidate the role which alveolar type II cells played in rat silicotic fibrosis. Methods T5BZ]Experimental silicosis model was established.The pathologic morphology of early silicosis was observed with light microscopy and electron microscopy.The gene expression of transforming growth factor β 1(TGF β 1 )and platelet-derived growth factor-B(PDGF-B) in alveolar type Ⅱ cells was examined by using immunohistochemical staining,immunoelectron-microscopy,and in situ hybridization.Experimental silicosis model was established.The pathologic morphology of early silicosis was observed with light microscopy and electron microscopy.The gene expression of transforming growth factor β 1(TGF β 1 )and platelet-derived growth factor-B(PDGF-B) in alveolar type Ⅱ cells was examined by using immunohistochemical staining,immunoelectron-microscopy,and in situ hybridization.[W Results (1)The pathologic changes in early stage silicosis consisted of focal interstitial inflammation,cellular nodes,mild interstitial fibroproliferation,and active proliferation of alveolar type Ⅱ cells.(2)Expression of TGF β 1,PDGF-B mRNAs and their relevant proteins were increased in the hyperplastic alveolar type Ⅱ cells of experimental group,only weak positive signals for TGF β 1 mRNA were seen in a part of normal alveolar type Ⅱ cells of control group. Conclusions The hyperplasia of alveolar type Ⅱ cells,is one of the pathologic changes in early silicosis.The upregulation of TGF β 1 and PDGF-B gene expression may play important role in early stage of silicotic fibrosis.[HJ]