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Stem cells have the ability to differentiate into different cell types, and they secrete paracrine factors that are thought to promote the healing process in damaged tissue1,2,3,4. They are, therefore, attractive within the field of regenerative medicine, because they can represent a possible curative treatment.
Radical prostatectomy (RP) is the golden curative treatment for patients with low/intermediate risk localized prostate cancer and a life expectancy > 10 years. The aim of the surgery is eradication of the cancer, but it has several side effects. The prevalence of post-prostatectomy incontinence ranges from 2-60% and erectile dysfunction (ED) is experienced by 20-90% of the patients5. Nerve-sparing technique is an option in some patients (Gleason score < 7, low risk of extracapsular disease)5. This technique spares the nerves that are responsible for erection, but even though this is possible, many patients still report ED postoperatively.
Treatment options for penile rehabilitation after RP consist primarily of treatment with PDE-5 inhibitors, injection or instillation therapy and vacuum pumps. Medicaments used for penile rehabilitation differ pharmacologically, but their mechanism of action includes relaxation of the smooth muscle cells in the corpus cavernosum. However, many patients experience treatment failure and never achieve an effect of the medicine that enables intercourse6.
The ED that occurs after RP is thought to be due to structurally irreversible changes7. These changes occur in the cavernous tissue and include apoptosis of the smooth muscle- and endothelial cells and fibrosis. The veno-occlusive mechanism that is responsible for a central part of the erection, is impaired by the changes, resulting in poorer filling and hardness of the penis7.
Many of the patients report that the ED they experience has a negative impact on their quality of life8. They are not ready to give up their sexual activity after surgery and, therefore, a curative therapy for ED is attractive, when the other available treatments for penile rehabilitation fail.
In previous trials, including animal and small phase 1 trials on humans, stem cells have shown promising results as an alternative treatment for ED2,9,10,11,12. Results show that it is safe to use ADRCs, and that the erectile function is significantly improved after a single injection into the corpora cavernosum2,9,10,11,12. Adipose-derived regenerative cells (ADRCs) are thought to support the tissue regeneration by paracrine mechanisms through liberation of multiple hormones, neurotrophic- and other growth factors, cytokines and possibly, micro-RNAs13. In addition, ADRCs are able to differentiate into several mature cell-types including endothelial and vascular muscle cells, cartilage cells, osteocytes and neurons14,15. These properties make stem cells interesting for developing a permanent new treatment for ED.
Stem cells are divided into several groups, basically those derived from the early embryo (embryonic stem cells) and those from adult tissue (adult stem cells). Adult stem cells include mesenchymal stem cells (MSC) that are multipotent and can be found in the bone marrow, adipose tissue, umbilical cord blood, placenta and dental pulp17.
Stem cells from the adipose tissue are easy to get access to, unlike stem cells derived from bone marrow. Harvesting stem cells from bone marrow is a risky and painful procedure compared to liposuction. The number of cells possible to harvest from bone marrow will be limited, while only the patient’s depots of adipose tissue sets the limit for the number of cells that can be harvested. It is, therefore, possible to isolate a large amount of stem cells from the adipose tissue without a subsequent need to culture the cells to obtain a satisfactory amount. The adipose-derived regenerative cells, also often referred to as the stromal vascular fraction (SFV), is composed of many cell types including MSCs, endothelial cells, pericytes, immune cells and progenitors hereof18. These may all play a role in the regenerative process.
The aim of the present study is to investigate the effect of stem cells on ED after RP by using 4 mL of autologous ADRCs isolated from freshly harvested adipose tissue after injection into the corpora cavernosum.