Angiogenesis Therapy for the Treatment of Erectile Dysfunction

Intracavernous Injection of Autologous Platelet-Rich Plasma Ameliorates Hyperlipidemia-Associated Erectile Dysfunction in a Rat Model

Introduction

Hyperlipidemia is associated with an increased risk of erectile dysfunction (ED) mediated by endothelial damage. Platelet-rich plasma (PRP) contains numerous angiogenic growth factors. Currently, evidence supporting the use of PRP for ED treatment is limited.

Aim

We investigated PRP in a rat model of hyperlipidemia-associated ED.

Methods

Thirty 2-month-old male Sprague–Dawley rats were randomly divided into 3 groups. 20 rats were fed a high-fat diet for 5 months and were randomly divided into 2 groups: (i) rats in the H group received supernatant injection into the corpus cavernosum weekly for 4 weeks; (ii) rats in the H + PRP group received PRP injection into the corpus cavernosum weekly for 4 weeks. 10 rats were fed a standard diet for 5 months and received supernatant injection into the corpus cavernosum weekly for 4 weeks (N group). 7 days after the 4th injection, all rats underwent erectile function testing and then euthanasia.

Main outcome measures

Erectile function was evaluated by measuring intracavernous pressure (ICP) and mean arterial pressure (MAP). Serum and penile tissue were collected for metabolic variable assessment and histochemical examination, respectively.

Results

Intracavernous pressure/MAP and area under the curve/MAP ratios were significantly higher in the N and H + PRP groups than in the H group. Insulin-like growth factor-1, brain-derived neurotrophic factor, and vascular endothelial growth factor levels were significantly higher in the H + PRP group than in the N and H groups. Corporal neuronal nitric oxide synthase, endothelial nitric oxide synthase, and endothelial cells were weakly expressed in the H group compared with the N and H + PRP groups. Intracorporal oxidative stress and apoptotic index were significantly higher in the H group than in the N and H + PRP groups.

Conclusions

This preclinical evidence suggests that clinical trials of PRP in men with ED should be considered. PRP may play a role in ED management.

Huang YC, Wu CT, Chen MF, et al. Intracavernous Injection of Autologous Platelet-Rich Plasma Ameliorates Hyperlipidemia-Associated Erectile Dysfunction in a Rat Model. Sex Med 2021;9:100317.

Recommendations on managing lenvatinib and everolimus in patients with advanced or metastatic renal cell carcinoma

INTRODUCTION

There are several second-line treatment options for patients with renal cell carcinoma after first-line failure of a tyrosine kinase inhibitor, especially with the recent approvals of cabozantinib, nivolumab, and the lenvatinib plus everolimus combination. A lack of reliable biomarkers and an overall lack of prospective head-to-head comparisons make it a challenge to choose a second-line treatment in the clinic. Areas covered: In this review/meta-opinion, we describe the safety profile of the lenvatinib plus everolimus combination in renal cell carcinoma. The combination of lenvatinib plus everolimus has achieved the highest rates of objective responses and the longest progression free and overall survival in cross-comparison trials. At the same time, the safety profile of this combination, including the rate of total and severe adverse events, the percentage of dose reductions required, and the rate of treatment discontinuation, was less favorable compared with available monotherapy options, suggesting that better management could help to maximize the activity of this combination while protecting patients from undue harm. Expert opinion: Herein, we aim to postulate multidisciplinary recommendations on the advice to offer to patients and caregivers before starting treatment and how to manage the combination from the perspective of daily clinical practice.

Identification of endothelial progenitor cells in the corpus cavernosum in rats

The vascular wall resident progenitor cells seem to serve as a local reservoir of cells for vascular repair. It was hypothesized that the corpus cavernosum may contain vascular wall endothelial progenitor cells (EPCs). In this study, we investigated the identification and localization of EPCs in the corpus cavernosum in a rat model. Adult male Sprague-Dawley rats were used to isolate EPCs from corpora cavernosum. To verify the existence and localization of EPCs, EPC-specific markers (CD34, Flk-1, and VE-cadherin) were evaluated by flow cytometric analysis and confocal microscopy. The EPC markers were mainly expressed in the cavernosal sinusoidal endothelial space. EPC-marker-positive cells made up about 3.31% of the corpus cavernosum of normal rat by FACS analysis. As shown by confocal microscopy, CD34⁺/Flk-1⁺ and CD34⁺/VE-cadherin⁺ positive cells existed in the corpus cavernosum. Our findings imply that regulation of corpus cavernosal EPCs may be a new therapeutic strategy in the treatment of erectile dysfunction.

Expression of the apelin-APJ pathway and effects on erectile function in a mouse model of vasculogenic erectile dysfunction

INTRODUCTION

Much attention has recently been focused on therapeutic angiogenesis as a treatment for erectile dysfunction (ED). The apelin and apelin receptor (APJ) system is known to cause endothelium-dependent vasodilatation and to be involved in angiogenesis.

AIM

To examine the differential expression of apelin and APJ in animal models of vasculogenic ED and to determine whether and how enhancement of apelin-APJ signaling restores erectile function in hypercholesterolemic mice.

METHODS

Acute cavernous ischemia was induced in C57BL/6J mice by bilateral occlusion of internal iliac arteries, and chronic vasculogenic ED was induced by feeding a high-cholesterol diet or by intraperitoneal injection of streptozotocin.

MAIN OUTCOME MEASURES

Messenger RNA (mRNA) levels of apelin and APJ were determined in cavernous tissue of each vasculogenic ED model by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). We evaluated erectile function by electrical stimulation of the cavernous nerve in hypercholesterolemic mice 1, 3, 7, and 14 days after a single intracavernous injection of apelin protein (5 μg/20 μL). The penis was harvested for histologic examinations and Western blot analysis.

RESULTS

The cavernous mRNA expression of apelin and APJ was up-regulated in acute ischemia model and down-regulated in chronic vasculogenic ED models. A significant restoration of erectile function was noted 1 day after injection of apelin protein into the penis of hypercholesterolemic mice; however, erectile function returned to baseline values thereafter. The beneficial effects of apelin on erectile function resulted mainly from an activation of endothelial nitric oxide synthase and increase in nitric oxide bioavailability through reduction in reactive oxygen species-mediated endothelial apoptosis rather than through direct endothelial cell proliferation.

CONCLUSION

These findings suggest that apelin-APJ signaling is a potential therapeutic target in the treatment of vasculogenic ED. Further studies are needed to develop a potent agonist for APJ and to determine the role of repeated dosing of apelin on long-term recovery of erectile function.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.