Article: Vascular regenerative therapies for the treatment of erectile dysfunction: current approaches.
From Journal, Andrology, Volume 1, Issue 4, pages 533–540, July 2013
R. A. Condorelli1, A. E. Calogero1, E. Vicari1, V. Favilla2, G. Morgia2, S. Cimino2, S. La Vignera1,*
(excerpt conclusion… use in other applications such as the reconstruction of penile tissue, enlargement of the penis…)
Partial Article…
Section, Adipose tissue stem cell therapy for erectile dysfunction;
Adipose tissue stem cell (ADSCs) isolated from the stromal vascular fraction of adipose tissue have been investigated concerning their multiple differentiation characteristics. They share properties of other stem cells, such as the ability to divide and renew themselves over long periods of time and to differentiate into specialized cells. They are easily obtained in large quantities; therefore, they appear to be a promising option as a clinical application for ED regeneration medicine.
In 2009, an interesting study was conducted in ADSCs to evaluate whether they could differentiate into endothelial cells in the penis, with the aim of identifying the underlying mechanisms of endothelial differentiation of ADSCs (Ning et al., 2009). To evaluate their endothelial differentiation in vivo, ADSCs were marked with bromodeoxyuridine (BrdU), injected into mouse corpora cavernosa and localized by immunofluorescence microscopy in various phases. For endothelial differentiation in vitro, ADSCs were cultured in the appropriate endothelial growth media (EGM2), stained for the endothelial markers CD31, vWF, and eNOS, and then evaluated for the ability to form tubular structures in matrigel and phagocytose acetylated LDL (LDL-Ac). To identify factors that promote endothelial differentiation, ADSCs were cultured in various media, each one containing a specific combination of additional factors in EGM2, and the uptake of LDL was evaluated. PD173074, a selective inhibitor of the fibroblast growth factor 2 (FGF2) receptor, was used to confirm the importance of FGF2 in the signalling pathway for endothelial differentiation for ADSCs. In vivo, 4 weeks after injection at the penile level, ADSCs were positive for BrdU and for the antigen endothelial cell of rats 1 (RECA-1). In contrast, it was observed in vitro that ADSCs that express endothelial markers multiplied more rapidly in the middle EGM2, rather than in the traditional culture medium, DMEM (Dulbecco’s Modified Eagle’s Medium). These properties are reduced in populations of ADSCs grown in the absence of FGF2, and endothelial differentiation is not observed with PD173074 treatment. This finding underscores the importance of the FGF2 growth factor in the repair of penile endothelial damage, and it opens new horizons in the field of ED treatment. Lin and collaborators have shown that ADSCs in culture medium supplemented with FGF2 can differentiate into endothelial cells, which can be injected into the corpora cavernosa of rats with ED, thereby enabling the recovery of poor erectile function (Lin et al., 2009).
In 2010, Garcia and his team once again studied the therapeutic use of ADSCs in subjects with diabetes mellitus type 2, in which ED is a frequent and important complication (Garcia et al., 2010). The study was conducted on 22 diabetic, fat, impotent rats. At 22 weeks of age, all animals were subjected to unilateral stimulation of the cavernous nerve, and the intracavernous pressures (ICP) and blood glucose levels were measured. Subsequently, the adipose perigonadal tissue was collected to obtain the ADSCs, and at 23 weeks of age, one million ADSCs were injected into the penis of the treatment group rodents, whereas the control group received only the vehicle. Erectile function was re-evaluated after 26 weeks, and a sample of tissue was taken for histological analysis. The results showed that after treatment, the stimulation of the cavernous nerve induced a greater increase in ICP compared with the controls, and an increase in the ICP/mean arterial pressure (MAP) ratio was also observed. Moreover, in the removed tissue, greater production of nNOS and a greater number of endothelial cells in the corpora cavernosa was observed. However, given that only a small contingent of ADSCs was found in the corpora cavernosa, it seems that the improvement in erectile function and the microarchitecture of the corpus cavernosum itself can be attributed to the paracrine action of NO rather than ADSC endothelial differentiation.
Hyperlipidaemia is also widely associated with ED; thus, ADSCs may be of therapeutic utility in this condition. A study was conducted on male rats that were induced to develop hyperlipidaemia through a high-fat diet (hyperlipidemic rats, HR), while a group that was fed with a normal diet served as the control (normal rats, NR) (Huang et al., 2010). Five months later, ADSCs were isolated from the perigonadal fat of all rats. The cells were cultured for 1 week, marked with 5-ethynyl-2′-deoxyuridine (EDU) and then injected in the corpora cavernosa of 18 HR, whereas 10 HR were injected phosphate buffer saline (PBS). At two and 14 days post-transplantation, four ADSC-injected HR were sacrificed to monitor the transplanted cells. Twenty-eight days after transplantation, the remaining HR underwent blood testing, evaluation of erectile function, and penile histological examination. Erectile function was estimated by measuring the ICP during electro-stimulation of the cavernous nerve, whereas the cavernous nerves and endothelial and smooth muscle cells were assessed by immunohistochemistry. Total serum cholesterol and LDL were significantly higher in both NR and HR rats, whereas HDL was significantly lower in HR than in NR. The ICP/MAP ratio was reduced in PBS-injected HR or NR, in contrast to ADSC-injected HR. The levels of nNOS-positive nerve fibres and the number of endothelial cells were lower in PBS-injected HR, compared with ADSC-injected HR. Smooth muscle cells were significantly more represented in both HR and NR rats. This suggests that treatment with ADSCs improves the adverse effects of hyperlipidaemia; therefore, this study confirms their potential therapeutic role in ED.
Very recently, another study was carried out on ADSCs to assess their ability to differentiate into smooth muscle and endothelial cells (Orabi et al., 2012). ADSCs were isolated from rats and differentiated into smooth muscle cells and endothelial cells, appropriately labelled, and then used to construct the cavernous tissue. This tissue was subsequently implanted into the penis of normal rats. After 1 and 2 months, the rats were sacrificed, and penile tissue and bone marrow samples were taken to assess cell survival. Using immunohistochemistry, the tissue was stained with haematoxylin-eosin and Masson’s trichrome, The cells had retained the ability for differentiation into smooth muscle cells and endothelial cells, and 2 months later, a significant number survived and were well integrated into penile tissues, supporting the potential for use of ADSCs in the therapeutic treatment of ED.
Another potential use of ADSCs may pertain to the treatment of ED resulting from radiotherapy for prostate cancer (Qiu et al., 2012a). Thirty male rats were divided into the following three groups: a control group that received only an injection of PBS, a group subjected to pelvic irradiation + injection of PBS and the treatment group, which received prostatic irradiation and a subsequent injection of ADSCs marked with EDU. After 17 weeks, erectile function was evaluated by measuring ICP during electrical stimulation of the cavernous nerves, and the penile tissue and major pelvic ganglia were examined by immunofluorescence staining for EDU. The study showed that irradiation significantly alters the mechanisms of erection, most likely as a result of damage to the cavernous nerve. Irradiation also reduced the expression of nNOS and the content of smooth muscle cells at the penile level, however, it did not influence the number of endothelial cells. The injection of ADSCs would regenerate the nerve, allowing for the recovery of erectile function, the expression of nNOS and restoring the content of smooth muscle cells.
ED is often a consequence of prostatectomy, and in such cases, the aetiopathogenetic mechanism is caused by an iatrogenic lesion of the cavernous nerves. Therefore, neuroprotective therapy and the use of stem cells could be promising forms of treatment. In particular, in an experimental model, Piao et al. (2012) evaluated the therapeutic efficacy of ADSCs and brain-derived neurotrophic factor (BDNF). Rats were divided into the following five groups: control group, group with a bilateral lesion of the cavernous nerves, the group receiving ADSCs, the group receiving the BDNF membrane and the group receiving both ADSCs and BDNF. After 4 weeks, the ICP/MAP ratio and the contents of smooth muscle cells and collagen at the penile level were evaluated by Masson’s trichrome staining, whereas the expression of eNOS and cGMP was assessed by immunohistochemistry. In the group of rats treated with ADSCs and BDNF, erectile function and the muscle cells/collagen ratio improved significantly. Furthermore, the quantities of nNOS, eNOS and cGMP significantly increased compared with those in the other four groups. These results suggest new possibilities for the treatment of post-prostatectomy ED.
In conclusion, in our opinion, adipose-derived stem cells are potential candidates for the treatment of ED for many reasons. In fact, these cells can be easily obtained in large quantities and possess the potential to undergo long-term proliferation, self-renewal and multipotent differentiation. In addition, they may find use in other applications such as the reconstruction of penile tissue, enlargement of the penis and in strengthening of the vaginal muscle.
