Relaxin-2 improves type I diabetes mellitus-induced erectile dysfunction in rats by protecting cavernous endothelial and smooth muscle function, and inhibiting penile fibrosis and apoptosis

Background: Diabetes mellitus-induced erectile dysfunction (DMED) responds poorly to first-line treatments, necessitating the development of new therapeutic strategies. Relaxin-2 (RLX-2) plays a crucial role in protecting vascular endothelium, vasodilatation, and antifibrosis in various diseases. However, its effects and mechanisms on DMED remain unclear.

Objectives: To investigate the effects and mechanisms of RLX-2 on DMED rats in vivo and vitro.

Methods: For in vivo research, 30 Sprague-Dawley rats were allocated into three groups: control, DMED, and DMED + RLX-2. The induction of DMED in the rats was achieved through intraperitoneal administration of streptozotocin, with confirmation of ED status being conducted via the apomorphine test. Rats in the DMED + RLX-2 group received continuous RLX-2 treatment by osmotic pump. Following a 4-week treatment period, assessment of erectile function was carried out using cavernous manometry, and samples of corpus cavernosum tissues were procured for subsequent analysis. For in vitro research, human cardiac microvascular endothelial cells (HCMECs) were allocated into three groups: control, high glucose (HG, 40 mM), and HG + RLX-2. HCMECs were cultured for 6 days and treated with RLX-2 for 48 h before collection for subsequent experiments.

Results: In DMED rats, RLX-2 treatment partially improved erectile function. We observed relatively normalized functions of endothelial and smooth muscle cells with decreased levels of apoptosis and fibrosis in the penis. In vitro experiments also demonstrated the antihyperglycemic effects of RLX-2.

Conclusions: RLX-2 can protect endothelial and smooth muscle function, and inhibit aberrant apoptosis and fibrosis in the corpus cavernosum, thereby improving erectile function in DMED rats. This may provide a novel treatment for DMED.