Application of Stem Cell in Human Erectile Dysfunction

Introduction

Erectile dysfunction (ED) is a condition that affects the sexual relations and quality of life of more than half of the male population over 40 years. This condition is believed to affect more than 300 million men in the next five years. Various studies have recommended the application of stem cells for the treatment of erectile dysfunction with promising results as it helps repair damaged tissues efficiently.

Since the 1990s, stem cells have been employed to treat various diseases and have shown potential. Their wide application reflects the importance of their anti-inflammatory, immunomodulatory (a substance that suppresses or stimulates the immune system), and therapeutic properties. Stem cells have helped treat cardiovascular, autoimmune, neurological, and hematologic diseases, strokes, Parkinson’s disease, and spinal cord injuries. It is possible that diseases or pathological conditions of the urinary system would also benefit from using stem cells.

What Is Erectile Dysfunction?

Erectile dysfunction is a common disorder that leads to the inability of a male to attain and maintain a penile erection for sexual intercourse. Usually, men above 40 years are affected by erectile dysfunction, which has a massive impact on their sexual life. The causes of erectile dysfunction include

• Damage of the nerves responsible for the erection.

• Side effects due to medications.

• Alterations in hormone levels such as testosterone.

The concern regarding erectile dysfunction has increased over the past few years, and currently, it is regarded as a public health problem. Various disorders are related to endothelial dysfunction (a type of coronary artery disease), which is linked to serious erectile dysfunction and is chiefly regulated by the vascular endothelium. The disorders that are associated with erectile dysfunction include the following.

• Diabetes mellitus (a condition characterized by high blood glucose).

• Cardiovascular diseases, such as stroke.

• Parkinson’s disease (central nervous system defect that affects movement).

• Pelvic nerve injury.

Earlier, the treatment of erectile dysfunction involved transient enhancement of penile erection. Currently, the most widely used treatment options include phosphodiesterase type-5 inhibitors such as Avanafil, Vardenafil, Sildenafil, and Tadalafil.

How Are Stem Cells Used for Human Erectile Dysfunction?

• Stem cells are partially differentiated or undifferentiated cells that can renew independently and differentiate into more specialized cell forms. Usually, stem cells are classified as follows according to the number of cell lines in which they could be differentiated:

  • Totipotent (zygote).

  • Pluripotent (embryonic stem cells).

  • Multipotent (hematopoietic and mesenchymal stem cells).

  • Unipotent.

• When the stem cell divides, the daughter cells can either remain stem cells or differentiate into specialized cells like muscle or nerve tissue cells. The ability of the stem cell to divide, differentiate, and cause tissue regeneration is influenced by its environment.

• The environment supports and interacts with the stem cells, transforming them to desired cell types and self-renewal. The following stem cells have been used in preclinical studies for erectile dysfunction:

  • Adipose (fat) tissue-derived stem cells.

  • Bone marrow-derived stem cells.

  • Muscle-derived stem cells.

• The regenerative effects of stem cells are obtained by the secretion of numerous growth factors and their migration to the repair site, along with cell contact and differentiation. The damaged tissues are regenerated in these sites according to the received signals or stimuli.

• Stem cell therapy has been employed to treat erectile dysfunction, as stem cells can differentiate into neuronal, endothelial, or smooth muscle cells. Hence, structural damage in the penile tissue can be restored.

• In vitro, stem cell differentiation has been proven in these cells. In various animal models, preclinical studies on stem cell therapy have been shown to improve erectile dysfunction.

• The exact mechanism has not been proven yet and includes the paracrine action of stem cells as the possible mechanism in erectile dysfunction demonstrated in animal models.

How Are the Stem Cells Delivered?

• Stem cells can be administered in different ways. Preclinical works have particularly examined the effect of intravenous (through the vein) and intraperitoneal injections (the area that contains the abdominal organs). Studies have suggested that intravenous injections are better at improving erectile function.

• Further studies have shown that periprostatic (the tissues around the prostate) implantation was equally effective with an intracavernosal (an injection into the base of the penis) injection. Generally, the injection is administered directly into the concerned organ.

• Many studies suggest that even less than one percent of the injected stem cells might remain in the target tissue and could dissipate only a few days after injection.

• Only a limited amount of stem cells remain in the target tissues after injection. However, they cause an essential effect by triggering endogenous repair and regeneration mechanisms.

• The stem cells further promote the differentiation and propagation of progenitor cells, thereby improving the repair of the target tissue.

• In all the clinical studies conducted on erectile dysfunction treatment, the stem cells have been delivered by direct injection in the target tissues of the penis or an intracavernosal injection.

What Are the Side Effects of Stem Cell Therapy?

Stem cell therapy might show certain side effects. Following mild side effects at the site of injection have been reported:

• Transient redness and swelling.

• Scrotal (external sac under the penis) and penile hematomas (blood collection outside blood vessels).

• Mild irritation at the injection site that resolved within 48 hours.

What Are the Future Prospects of Stem Cells in Erectile Dysfunction?

The application of stem cell therapy in human erectile dysfunction has good therapeutic potential. The currently available data from the previously conducted research can be used as a base for employing stem cells to treat erectile dysfunction. However, more research for broader applications is still required. A randomized, double-blind, controlled study is urgently required to study the clinical effect of stem cell treatment in human erectile dysfunction. However, it remains a difficult task due to its invasive nature.

Conclusion

Various preclinical and clinical research have documented primary data regarding the potential efficacy and safety of stem cell therapy in human erectile dysfunction. However, future randomized clinical trials must be performed to examine their use in a sufficient number of humans over a long duration. This will help to obtain proper knowledge regarding the best therapeutic strategy and highlight the potential adverse effects associated with this therapy.