Arterial erectile dysfunction: reliability of new markers of endothelial dysfunction

Revisiting experimental models of erectile dysfunction and their value in drug discovery and development

INTRODUCTION

Erectile dysfunction (ED) is a common condition that often signals underlying endothelial dysfunction, although the underlying causative factor(s) are likely complex and multifactorial. Various animal models have been developed to provide a research platform to study ED and served as an important basis for the discovery and subsequent development of novel therapeutic drugs for ED.

AREAS COVERED

The review article provides an overview of various animal models in ED research with an emphasis on important drug target discovery relating to each specific experimental model. The authors highlight translation from basic science research to major preclinical and clinical studies in this evolving field of ED research.

EXPERT OPINION

Animal models simulate the pathological features of various types of ED and clarify their molecular mechanisms. These mechanisms aid in discovering drug targets, while established ED models also provide a basis for validating drug efficacy, safety, and specific action mechanisms. The development of techniques in detection methods, cellular experimental, and omics has a profound impact on disease prediction, model evaluation, and optimization of therapeutic modalities. On this basis, many drug therapies targeting these ED-related mechanisms, especially in the nitric oxide/cyclic guanosine monophosphate pathways have been applied in preclinical studies. However, focusing on drug development for those types of ED where phosphodiesterase 5 inhibitor therapy is limited may be more valuable.

The penile duplex ultrasound: How and when to perform it?

BACKGROUND

Because it is a superficial structure, the penis is ideally suited to ultrasound imaging. A number of disease processes, including Peyronie's disease, penile fractures and tumors, are clearly visualized with ultrasound. Baseline and dynamic assessment of cavernosal arterial changes after pharmaco-stimulation with alprostadil allows standardized diagnosis of arterial and venogenic causes of erectile dysfunction (ED).

OBJECTIVE

To illustrate how to correctly perform flaccid and dynamic penile duplex ultrasound (D-PDU) and in which patients to recommend it.

MATERIALS/METHODS

An extensive search of the literature was carried out on Pubmed with the insertion of the following Medical Subjects Headings (MeSH) terms and keywords "penile color Doppler ultrasound" "peak systolic velocity" "end-diastolic velocity", "acceleration time", "resistance index".

EVIDENCE

In our experience, arterial erectile dysfunction is identified after standardized intracavernous injection (ICI) of alprostadil (10 mcg) when values of peak systolic velocity (PSV) are <35 cm/s and, in the most severe forms, for values <25 cm/s. Arterial insufficiency can also be identified by increased acceleration time (AT) values (>110 ms) and/or by a lack of visualization of helicine arteries at power Doppler mode along with incomplete achievement of penile rigidity. The veno-occlusive incompetence is determined when end-diastolic velocity (EDV) values are >4.5-5 cm/s or in the case of resistance index (RI) values <0.75. The assessment of additional surrogate markers of endothelial dysfunction, that is, intima-media thickness, mean platelet volume (MPV), endothelial progenitor cells (EPC), endothelial cell specific molecule-1(endocan) are also useful in assessing the patient's cardiovascular risk but are still considered investigational in the interpretation of D-PDU results.

CONCLUSION

D-PDU scan after ICI with vasoactive drugs is a safe procedure and represents the gold standard for the diagnostics of penile pathologies and should be performed in men with ED not responding to oral conventional therapies and/or in those requiring accurate stratification of cardiovascular risk.

Molecular Mechanisms Underpinning Microparticle-Mediated Cellular Injury in Cardiovascular Complications Associated with Diabetes

Microparticles (MPs) are small vesicles shed from the cytoplasmic membrane of healthy, activated, or apoptotic cells. MPs are very heterogeneous in size (100–1,000 nm), and they harbor proteins and surface antigens specific to cells they originate from. Virtually, all cells can shed MPs, and therefore, they can be found in all body fluids, but also entrapped in tissues. Of interest and because of their easy detection using a variety of techniques, circulating MPs were recognized as biomarkers for cell activation. MPs were also found to mediate critical actions in intercellular communication and transmitting biological messages by acting as paracrine vehicles. High plasma numbers of MPs were reported in many cardiovascular and metabolic disturbances that are closely associated with insulin resistance and low-grade inflammation and have been linked to adverse actions on cardiovascular function. This review highlights the involvement of MPs in cardiovascular complications associated with diabetes and discusses the molecular mechanisms that underpin the pathophysiological role of MPs in the onset and progression of cellular injury in diabetes.

Extracellular Vesicles in Human Reproduction in Health and Disease

Extensive evidence suggests that the release of membrane-enclosed compartments, more commonly known as extracellular vesicles (EVs), is a potent newly identified mechanism of cell-to-cell communication both in normal physiology and in pathological conditions. This review presents evidence about the formation and release of different EVs, their definitive markers and cargo content in reproductive physiological processes, and their capacity to convey information between cells through the transfer of functional protein and genetic information to alter phenotype and function of recipient cells associated with reproductive biology. In the male reproductive tract, epididymosomes and prostasomes participate in regulating sperm motility activation, capacitation, and acrosome reaction. In the female reproductive tract, follicular fluid, oviduct/tube, and uterine cavity EVs are considered as vehicles to carry information during oocyte maturation, fertilization, and embryo-maternal crosstalk. EVs via their cargo might be also involved in the triggering, maintenance, and progression of reproductive- and obstetric-related pathologies such as endometriosis, polycystic ovarian syndrome, preeclampsia, gestational diabetes, and erectile dysfunction. In this review, we provide current knowledge on the present and future use of EVs not only as biomarkers, but also as therapeutic targeting agents, mainly as vectors for drug or compound delivery into target cells and tissues.

Microparticles of healthy origins improve endothelial progenitor cell dysfunction via microRNA transfer in an atherosclerotic hamster model

AIM

In this study, we aimed: (i) to obtain and functionally characterize the cultures of late endothelial progenitor cells (EPCs) from the animal blood; (ii) to investigate the potential beneficial effects of circulating microparticles (MPs) of healthy origins on EPC dysfunctionality in atherosclerosis as well as involved mechanisms.

METHODS

Late EPCs were obtained and expanded in culture from peripheral blood isolated from two animal groups: hypertensive-hyperlipidaemic (HH) and control (C) hamsters. In parallel experiments, late EPC cultures from HH were incubated with MPs from C group.

RESULTS

The results showed that late EPCs display endothelial cell phenotype: (i) have ability to uptake 1,1-dioctadecyl-3,3,3,3 tetramethylindocarbocyanine-labelled acetylated low-density lipoprotein and Ulex europaeus agglutinin lectin-1; (ii) express CD34, CD133, KDR, CD144, vWF, Tie-2. Late EPCs from HH exhibited different morphological and functional characteristics compared to control: (i) are smaller and irregular in shape; (ii) present decreased endothelial surface marker expression; (iii) display reduced proliferation, migration and adhesion; (iv) lose ability to organize themselves into tubular structures and integrate into vascular network; (v) have diminished function of inward rectifier potassium channels. The incubation of late EPCs with MPs improved EPC functionality by miR-10a, miR-21, miR-126, miR-146a, miR-223 transfer and IGF-1 expression activation; the kinetic study of MP incorporation into EPCs demonstrated MP uptake by EPCs followed by the miRNA transfer.

CONCLUSION

The data reveal that late EPCs from atherosclerotic model exhibit distinctive features and are dysfunctional, and their function recovery can be supported by MP ability to transfer miRNAs. These findings bring a new light on the vascular repair in atherosclerosis.

Endothelial progenitor cells and erectile dysfunction: a brief review on diagnostic significance and summary of our experience

The article provides a brief review of the literature concerning the diagnostic use of endothelial progenitor cells in patients with erectile dysfunction. In particular, patients with arterial erectile dysfunction could benefit from the use of this diagnostic marker, which in clinical practice can be used together with more conventional methods such as the penile Doppler. It is very important to acquire diagnostic tools for the diagnosis of sub clinical form of endothelial dysfunction in these patients, in particular when the erectile dysfunction is associated with cardiovascular risk factors.

Arterial erectile dysfunction: different severities of endothelial apoptosis between diabetic patients "responders" and "non responders" to sildenafil

BACKGROUND

The low pharmacological response to phosphodiesterase type 5 inhibitors represents an expression of higher endothelial damage in certain categories of patients with erectile dysfunction and high cardiovascular risk. The present study evaluated this objective in type 2 diabetic patients with erectile dysfunction, classified as "non responders" to Sildenafil.

METHODS

Eighteen "responder" and twelve "non responder" type 2 diabetic patients were evaluated, relatively to different levels of endothelial damage, through the diagnostic use of a new immunophenotype of circulating endothelial progenitor cells (CD45neg/CD34pos/CD144pos) and endothelial microparticles (CD45neg/CD144pos/Annexin Vpos), recently developed and published by our group.

RESULTS

"Non responder" patients showed a significant higher severity [8.0±3.0 (International Index of Erectile Function-abbreviated version with 5 questions) vs 14.0±3.0] and duration (10.0±2.0 vs 7.0±2.0 years) of erectile dysfunction, higher level of penile arterial insufficiency (peak systolic velocity=13.0±16.0 vs 28.0±26.0cm/s; acceleration time=153±148 vs 125±128 mm/s) and finally a significant higher level of endothelial apoptosis [0.15±0.13 vs 0.05±.0.03% (serum concentrations of endothelial microparticles)] associated with higher serum concentrations of circulating late immunophenotype of endothelial progenitor cells (0.40±0.35 vs 0.12±.0.10%).

CONCLUSIONS

The results of this study corroborate the clinical value of the low clinical response to phosphodiesterase type 5 inhibitors in the treatment of erectile dysfunction in the patients with high cardiovascular risk profile, such as diabetics. In addition, the markers used in this study confirm their potential application in clinical practice as useful indicators of endothelial alteration. However, in the future we will have to assess a larger number of patients and for a longer period of observation in order to better understand the causal and temporal relations.

Original evaluation of endothelial dysfunction in men with erectile dysfunction and metabolic syndrome

We have recently demonstrated the diagnostic value of a new immunophenotype of blood endothelial progenitor cells (EPCs=CD45neg/CD34pos/CD144pos) and endothelial microparticles (EMPs=CD45neg/CD144pos/AnnexinVpos) in patients with arterial erectile dysfunction (ED) according to severity of cavernous arterial insufficiency evaluated through penile Doppler. The aim of this study was to evaluate both EPCs and EMPs in patients with arterial ED and metabolic syndrome (MetS), comparing these patients with another group of patients without MetS and ED and a third group with MetS but without ED. For this study 50 patients with arterial ED and MetS were selected (age: 55.0±3.0 years; range: 47-60). A group of age-matched (age: 54.0±2.0 years; range: 44-60) patients without arterial ED and MetS (n=30), and another group of age-matched (age: 57.0±4.0 years; range: 40-62) patients with MetS but without ED (n=20) represented the control groups. EPCs and EMPs were significantly higher in patients compared with other groups (P<0.01). Both EPCs and EMPs correlated positively with the age, body mass index, and score of international index of ED (version five items) and with the following cavernous artery indices: peak systolic velocity, acceleration time and intima-media thickness. Among control groups patients with MetS but without ED showed serum concentrations of EPCs and EMPs significantly higher (P<0.05) compared with patients without MetS and ED. Patients with arterial ED and MetS have higher EPCs and EMPs compared with patients with MetS but without ED and patients without MetS and ED.