Pigment Epithelium-Derived Factor, a Human Testis Epididymis Secretory Product, Promotes Human Prostate Stromal Cell Growth in Culture

Abstract

We identified and characterized unrecognized testicular secretory proteins that impact human prostate growth. Human spermatocele fluid served as a source of testicular epididymal secretions and prostatectomy specimen benign prostatic hyperplasia stromal cells as the in vitro prostate growth promoting effects indicator. RMPI plus medium supplemented with 10% fetal bovine serum MALDI-TOF, MS FBS and ITS+ (Collaborative Research-Becton Dickinson, Bedford, Massachusetts) served as positive and negative controls, respectively. Whole and fractionated spermatocele fluid or specific proteins without and with select polyclonal or monoclonal antibodies were added to routine 6-day cultures. The observation of significantly increased 6-day cell counts compared with appropriate controls (p <0.05) was judged to reflect cell growth. Amino acid microsequencing and MALDI-TOF MS sequence analysis were done on persistent protein bands from active spermatocele fluid fractions. Whole and fractionated human spermatocele fluid increased stromal cell culture numbers significantly. Sequence analysis of 47 and 17 kDa 1-dimensional gel bands in the final active fraction identified a major peptide with sequence homology to human pigment epithelium-derived factor (PEDF). The presence of PEDF was confirmed by Western blot analysis. Addition of recombinant PEDF to incomplete medium significantly increased stromal cell culture number. PEDF antibodies neutralized or markedly decreased the stromal stimulating effect of spermatocele fluid and PEDF. The observations presented provide evidence for human testis/epididymis secretion of PEDF and for a PEDF in vitro growth promoting effect on benign prostatic hyperplasia stroma. The concept that testicular epididymal secretory proteins may influence normal and abnormal prostate growth warrants continued consideration.