The bioavailability of the non-hormonal male contraceptive adjudin is low in rats due to the blood-testis barrier (BTB). This study was designed to examine if F5-peptide, an endogenously produced reversible BTB modifier, could enhance the bioavailability of adjudin to affect spermatogenesis and provide a contraceptive effect in rats while reducing systemic toxicity.
We overexpressed F5-peptide in adult male rats (n=10 rats; with 3 or 4 rats for each of the three different experiments noted in the three regimens) by intratesticular injection of a mammalian expression vector pCI-neo (pCI-neo/F5-peptide) vs. empty vector alone (pCI-neo/Ctrl) to be followed by treatment with adjudin by oral gavage at a dose of 10 or 20 mg/kg. The status of spermatogenesis was assessed by histological analysis and dual-labeled immunofluorescence analysis on Day 16. To assess fertility, we allowed treated males (n=3–4 rats) to mate with mature female rats (n=3–4) individually, and assessed the number of pups on Days 23, 36 and 82 to assess fertility and reversibility.
All 4 treated rats overexpressed with F5-peptide and low-dose adjudin were infertile by Day 36, and half of these rats were fertile by Day 82, illustrating reversibility. However, overexpression of F5-peptide alone (or low-dose adjudin alone) had no effects on fertility in n=3 rats. These findings were consistent with the histology data that illustrated the BTB modifier F5-peptide promoted the action of adjudin to induce germ cell exfoliation, mediated by changes in cytoskeletal organization of F-actin and microtubules across the epithelium, thereby reducing the systemic toxicity of adjudin.
In this proof-of-concept study, it was shown that overexpression of the F5-peptide prior to administration of adjudin to rats at a low (and ineffective dose by itself) was found to induce reversible male infertility.
Overexpression of F5-peptide, an endogenously produced biomolecule in the testis known to induce BTB remodeling, enhanced the contraceptive effect of adjudin in rats, supporting proof of concept studies of BTB disrupters in men.