The degree of cross-linking of polyacrylic acid affects the fibrogenicity in rat lungs.

Polyacrylic acid (PAA) with different concentrations of cross-linker was instilled into the trachea of rats to examine the effect of PAA crosslink density on lung disorders.

Methods

F344 rats were intratracheally exposed to low and high doses of PAA with cross-linker concentrations of 0.1, 1.0, and 5.0% (CL0.1%, CL1.0%, and CL5.0%, respectively). Rats were sacrificed at 3 days, 1 week, 1 month, 3 months, and 6 months after exposure. PAA with different cross-linker concentrations caused an increase in neutrophil influx, cytokine-induced neutrophils, and chemotactic factor (CINC) in bronchoalveolar lavage fluid (BALF) from 3 days to 1 week after instillation. Lactate dehydrogenase (LDH) activity in BALF and heme oxygenase-1 (HO-1) release in lung tissue were higher in the CL0.1% exposure group during the acute phase. Lung histopathological findings also showed that severe fibrotic changes induced by CL0.1% were greater than those observed in CL1.0% and CL5.0% exposure during the observation period. CL0.1% was associated with more severe lung fibrosis, and a decrease in lung fibrosis was observed with increasing cross-linker concentrations, suggesting that the cross-link density of PAA is a physicochemical feature that affects lung disorders.