Melatonin-pretreated mesenchymal stem cell-derived exosomes alleviate cavernous fibrosis in a rat model of nerve injury-induced erectile dysfunction via miR-145-5p/TGF-β/Smad axis

Abstract

Background Cavernous nerve injury-induced erectile dysfunction (CNI-ED) is a common complication after radical prostatectomy. Conventional treatment approaches have had little success in treating the severe cavernous fibrosis which is a consequence of CNI-ED. Methods Pre-treatment of adipose-derived stem cells with melatonin allows for the extraction of active exosomes (MT-hASC-EVs) from the conditioned medium. The therapeutic effects of MT-hASC-EVs were assessed in a rat model of CNI-ED, and the anti-fibrotic properties were evaluated. MicroRNA sequencing was used to identify specific microRNAs highly expressed in MT-hASC-EVs, and differential microRNAs were screened for regulatory pathways through target gene enrichment analysis. Finally, the conclusions from bioinformatics analysis were validated through in vitro experiments. Results Intracavernous injection of MT-hASC-EVs significantly restored erectile function and reduced the extent of corpus cavernosum fibrosis in the CNI-ED rat model. MT-hASC-EVs promoted the proliferation and anti-apoptotic effects of corpus cavernosum smooth muscle cells (CCSMCs) in vitro. Mechanistically, MT-hASC-EVs inhibit fibrosis by delivering miR-145-5p, which targets TGF-β2/Smad3 axis. Conclusions MT-hASCs-EVs can inhibit cavernous fibrosis and improve erectile function in a rat model of CNI-ED by targeting the miR-145-5p/TGF-β/Smad axis.

1. Introduction

Erectile dysfunction (ED) refers to the persistent or recurrent inability to achieve and maintain sufficient penile erection for satisfactory sexual intercourse [1]. The etiology of ED is complex, and cavernous nerve injury (CNI) is a significant contributing factor, commonly associated with pelvic surgery, pelvic fractures, and post-urethral injury surgeries [2]. CNI-induced ED following radical prostatectomy has an incidence rate as high as 63-94%, despite the use of nerve-sparing techniques [3]. During radical prostatectomy, unavoidable traction, compression, and vascular damage to the cavernous nerves lead to impairment and neurotrophic loss which results in reduced penile blood flow perfusion, leading to sustained hypoxia in the corpus cavernosum [3]. Subsequent smooth muscle atrophy occurs along with activation of TGF-β/Smad and RhoA/Rock pathways which lead to cavernous fibrosis [2, 4]. Traditional phosphodiesterase 5 inhibitors (PDE5i, e.g., tadalafil and sildenafil) have limited efficacy in treating CNI-ED due to insensitivity of corpora cavernosa tissue to nitric oxide (NO) resulting from smooth muscle cell loss and cavernous fibrosis [5, 6]. It is worth noting that while regeneration of cavernous nerves could be observed 28 days after CNI in a rat model, subsequent loss of smooth muscle cells and cavernous fibrosis were irreversible [7]. Therefore, prevention, alleviation, or even reversal of cavernous fibrosis represents an important therapeutic direction for managing CNI-ED.

In recent years, stem cells and their derivatives have become new treatment options for ED [8–10], among which extracellular vesicles (EVs) have gained favor among researchers due to their simplicity, convenience, and suitability for industrial production [11]. EVs are sac-like structures that cells release into the extracellular space [12–14]. Based on diameter and source, they can be divided into exosomes (50–100 nm) and microvesicles (100–1000 nm). As a carrier, EVs transport signal proteins, lipids, and nucleic acids, which can be endocytosed by distant target cells, thereby changing the biological behavior of the target cells and serving as a key factor in cell-to-cell signal communication [15]. Many reports have suggested that mesenchymal stem cell-derived EVs have a certain therapeutic effect on CNI-ED [16–19].

Melatonin is a hormone secreted by the pineal gland, primarily responsible for regulating biological rhythms and sleep-wake cycles [20]. In addition, melatonin has been found to have therapeutic