Alterations in the balance of sex hormones may affect rat prostatic inflammation and fibrosis, and osteopontin might be involved in this process.

Objective: This study aimed to investigate the effects of sex hormone imbalance on rat prostatic inflammation and fibrosis and identify the key molecules involved.

Methods: Castrated Sprague-Dawley (SD) rats were treated with a constant dose of oestradiol (E) and different doses of dihydrotestosterone (DHT) to achieve different oestrogen/androgen ratios. After 8 weeks, serum E and DHT concentrations, relative seminal vesicle weights, histopathological changes and inflammation were measured, collagen fiber content and oestrogen receptor (ER) and androgen receptor (AR) expression were detected, mRNA sequencing and bioinformatics analysis were performed to identify differentially expressed genes (DEGs).

Results: The severity of inflammation in the rat dorsolateral prostate (DLP) was higher, collagen fibre content and ER expression in the rat DLP and prostatic urethra were increased and AR expression in the rat DLP was decreased in the 1:1 E/DHT-treated group than that in the 1:10 E/DHT-treated group. RNA-seq analysis identified 487 DEGs, and striking increases in the expression of mRNAs encoding collagen, collagen synthesis and degradation enzymes, growth factors and binding proteins, cytokines and chemokines, and cell-surface molecules were confirmed in the 1:1 E/DHT-treated group compared to the 1:10 E/DHT-treated group. mRNA expression of secreted phosphoprotein 1 (Spp1) and protein expression of osteopontin (OPN, encoded by Spp1) were increased in the 1:1 E/DHT-treated group compared to the 1:10 E/DHT-treated group, and Spp1 expression correlated positively with Mmp7, Cxcl6 and Igfn1 expression.

Conclusions: The imbalance in the oestrogen/androgen ratio may affect rat prostatic inflammation and fibrosis, and OPN might be involved in this process.