Histological Evidence of the Antifibrotic Effect of Polyphenolic Extracts from the Berries Vaccinium uliginosum, Vaccinium oxycoccos, and Vaccinium vitis-idaea in a Model of Pulmonary Fibrosis

Background: Pulmonary fibrosis is a chronic and progressive disease characterized by excessive deposition of extracellular matrix and scarring of lung tissue, resulting in a gradual decline in respiratory function. Despite advances in understanding its pathogenesis, effective therapeutic options remain limited. This study aimed to evaluate the antifibrotic effects of concentrated polyphenolic extracts obtained from bilberry (Vaccinium uliginosum), cranberry (Vaccinium oxycoccos), and lingonberry (Vaccinium vitis-idaea) in a bleomycin-induced rat model of pulmonary fibrosis. Methods: Pulmonary fibrosis was induced in rats through the intratracheal administration of bleomycin. Beginning seven days after fibrosis induction, concentrated polyphenolic extracts from the three Vaccinium species were administered orally for 14 consecutive days. Lung histomorphology, inflammatory cell infiltration, collagen composition, and hemorheological parameters were subsequently evaluated. Results: Treatment with the berry polyphenolic extracts reduced the severity of bleomycin-induced pulmonary fibrosis and decreased inflammatory cell infiltration in lung tissue. The extracts also influenced collagen remodeling, promoting a relative predominance of immature type III collagen over mature type I collagen. Furthermore, bleomycin-induced pulmonary fibrosis was accompanied by increased blood viscosity, whereas treatment with the polyphenolic extracts partially normalized the altered hemorheological parameters. Conclusions: Concentrated polyphenolic extracts derived from Vaccinium species demonstrated antifibrotic, anti-inflammatory, and hemorheological effects in experimental pulmonary fibrosis. These findings support further investigation of their underlying molecular mechanisms and potential translational applications studies.