IMR Press / JOMH / Volume 17 / Issue 4 / DOI: 10.31083/jomh.2021.090
Open Access Original Research
Intracavernous injection of stem cell-derived bioactive molecules for erectile dysfunction—a pilot phase non-randomized controlled trial
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1 Heartstem, Inc., Beverly Hills, CA 90212, USA
2 Southern California Hospital Heart Institute, Culver City, CA 90232, USA
3 Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
4 Nustem, Inc., Beverly Hills, CA 90212, USA
J. Mens. Health 2021, 17(4), 99–108; https://doi.org/10.31083/jomh.2021.090
Submitted: 4 May 2021 | Accepted: 23 May 2021 | Published: 30 September 2021
Abstract

Background and objective: Experimental and few clinical studies have indicated great potential of stem cell treatments as both a causal and symptomatic approach for the treatment of male erectile dysfunction (ED). We investigated the effect of a one-time injection of stem-cell derived bioactive molecules in patients with self-reported ED.

Materials and methods: Twenty self-referred male patients with at least one-year history of ED received a one-time intra-penile injection of acellular stem cell-derived bioactive molecules. ED was evaluated by the International Index of Erectile Function questionnaire (IIEF-5), and quality of life was assessed by the Short-Form-36 questionnaire, (SF-36) at baseline and at 6 months. Six male patients with ED, who received a similar injection using saline served as a historic control. Primary outcome was erectile function as measured by IIEF-5 scores. Secondary outcomes were quality of life, assessed by SF-36 questionnaire.

Results: IIEF-5 scores improved from 12.9 ± 4.47 at baseline to 18 ± 3.37 at follow-up (p < 0.05). No significant difference of IIEF-5 scores were observed in the historic controls during the observation period (11 ± 2.53 at baseline vs 10.67 ± 3.5 at follow-up; p > 0.05). Patients, who received stem cell injections, demonstrated significantly enhanced IIEF-5 scores compared to the historic control (p < 0.05). Quality of life scores were significantly improved (role limitations due to physical health issues 56.25 ± 42.82 at baseline vs 68.75 ± 40.45 at follow-up, p < 0.05, energy 51.57 ± 19.33 at baseline vs 57.75 ± 12.3 at follow-up, p < 0.05, emotional wellbeing 56.32 ± 16.28 at baseline vs 68.1 ± 11.73 at follow-up, p < 0.05, and social functioning 67.5 ± 23.79 at baseline vs 76.25 ± 18.98 at follow-up, p < 0.05).

Conclusions: A one-time intracavernous acellular stem cell-derived bioactive molecule injection improves IIEF-5 scores and quality of life in men with ED in this small pilot phase study (ClinicalTrials.gov Identifier: NCT04684602).

Keywords
Erectile dysfunction
Stem cell therapy
Umbilical cord blood
Exosome
Secretome
1. Introduction

Erectile dysfunction (ED) is defined as the inability to attain and maintain an erection with sufficient rigidity to permit satisfactory sexual intercourse [1]. While oral pharmacotherapies such as phosphodiesterase-5 inhibitors (PDE5i) exhibit clear benefits, their effects are transient as opposed to an etiological therapy approach and treatment is relatively costly [2].

Impaired erectile function represents a complex, yet common medical condition, which profoundly impacts the quality of life of those affected [3]. According to cross-sectional studies, 50% of men above the age of 50 years suffer from some degree of ED. There appears to be a substantial association between vascular disorders and ED with significant implications exceeding the treatment of the primary condition by an adequate cardiovascular risk assessment [4]. In the longitudinal, population-based “Massachusetts Male Aging Study”, heart disease, diabetes mellitus, and hypertension were identified as major risk factors for ED in males aged 40–69 years [5]. Moreover, the prevalence of ED is predominant in men suffering from chronic diseases including renal insufficiency, liver dysfunction and heart failure [6-11]. Other causes include a reduction of sexual hormones due to acquired hypogonadism, chronic diseases as well as urologic and traumatic issues. Of interest, among younger men an overexposure to pornographic videos on social media and widely accessible websites has been related to psychologically based sexual dysfunction [6-9].

Stem cells have the ability to either multiply through division of daughter cells or transform into specialized cell types, thus holding the potential for enhanced tissue repair and maintenance of numerical capacity [12]. The classification underlies the cells’ multi-lineage differentiation properties and distinguishes totipotency, pluripotency, multipotency, and unipotency, in descending order based on differentiation capacities [13]. In that context, embryonic stem cells are pluripotent and can serve as progenitors for all tissue types. Adult stem cells, however, are further advanced in differentiation and develop into specialized structures in a more tissue-restricted manner [14]. Cells can be extracted from human tissues including bone marrow, adipose tissue, neonatal teeth, umbilical cord blood, placenta, and Wharton’s Jelly, with the two latter preparations being reflected upon in the consecutive analysis [15-17]. More recently, exosomes - extracellular vesicles containing components of the mesenchymal stem cell (MSC) secretome (i.e., DNA, RNAs, miRNA, lipids, and functional proteins) [18]—have emerged as a potential addition to the clinical deployment of stem cell therapeutics [19]. Beneficial results have been reported in the frame of preclinical studies exploring effects on central nervous [20], cardiovascular [21,22], hepatorenal [23,24], and metabolic [25,26] conditions.

Stem cell therapy has been proposed in the management of ED with respect to complete replacement of lost or damaged cells or protection of threatened host cells via immunomodulatory effects, provision of trophic factors or gene delivery [27]. A number of case reports and small clinical studies using stem cell preparations in men with ED have been published—with promising results. A recent report by our group suggested beneficial effects of stem cell injections as a curative approach for ED, however, limited present data due to small sample sizes accounts for reduced external validity [28].

We report the first study evaluating a larger group of 20 patients with ED undergoing an intracavernous injection of acellular stem cell-derived bioactive molecules.

2. Materials and methods

The present study was approved by the institutional review board of the International Cell Surgical Society (Palm Desert, CA, USA).

Twenty self-referred men with ED were recruited for stem cell injections as part of an ongoing larger study investigating the effects of acellular stem cell preparations on vascular disease presentations. Furthermore, six male ED patients with a similar medical history, who received similar intracavernosal injections using saline, served as a historic control. All patients signed an informed consent form, agreed to follow up, and were informed about the experimental nature of the treatment. Data regarding the participants’ medical history, past surgical history, and relevant current medication was extracted from medical records.

Inclusion criteria were as follows:

(1) Self-reported ED for at least one year;

(2) Age 18-80 years;

(3) Availability for follow up visits.

Exclusion criteria were:

(1) History of any known malignancy within the last two years;

(2) Inability to provide consent;

(3) Current use of anticoagulants (except low dose aspirin);

(4) Uncontrolled diabetes mellitus;

(5) Uncontrolled hypertension;

(6) Any life-threatening condition with a life expectancy of less than one year.

During the procedure, study participants were comfortably placed in supine position. The penis was prepared with topical 2% lidocaine cream for local anesthesia. Subsequently, the aspirate containing the allograft suspension was injected intra-cavernosal into the penis at three injection sites bilaterally along the penile shaft (total of 6 injections of 0.33 cc per patient, 2 cc total) using a new 22 G sterile needle. The patients were watched for 20 minutes before being discharged. All patients received a follow-up phone call the following day and were advised to contact the clinic in case of occurrence of local and/or systemic changes, symptoms potentially related to the procedure or any events. Recipient records were maintained for the purpose of post-injection tissue tracing according to the Joint Commission standard QC.5.310.7 and FDA 21 CFR 1271.290 regulation requirements.

At the initial office visit and at follow-up at six months, study participants underwent an assessment of their general health. ED was assessed within the context of a personal interview and the International Index of Erectile Function Questionnaire (IIEF-5; [29]) was provided. The following parameters were obtained at baseline and at six months follow-up:

-Blood pressure (mmHg) at rest,

-Heart rate (beats per minute, bpm) at rest,

-IIEF-5 questionnaire,

-Six Minute Walk Test (6MWT, measured in meters (m) [30]), and

-Short-Form-36 Quality of Life Questionnaire (SF-36; [31]).

The 36-Item Short Form Health Survey (SF-36) is a self-reported quality of life measure that was developed as a component of the Medical Outcomes Study to explain variation in patient outcomes. Thirty-six questions that span 8 domains of health are used to measure clinical parameters with regards to the health status of specific patient groups in order to extrapolate to the efficacy of clinical interventions [31]. Erectability and intercourse success were assessed and evaluated based upon personal interviews on patient satisfaction in the frame of a clinical follow-up.

The stem cell-derived product is a highly concentrated acellular solution derived from umbilical cord tissue containing no blood cells or blood products. This tissue allograft was processed in an FDA approved “Human Cell and Tissue Establishment” (HCTERS) for the recovery, screening, donor testing, packaging, processing, storage, labeling, and distribution of human umbilical cord and related tissue allografts. Each intervention consisted of a 2 milliliter (cc) aliquot of PrimeProTM (Thomas Advanced Medical, Los Angeles, CA, USA) sourced from donated human umbilical cord tissue, which was obtained by an FDA approved “Tissue Procurement” facility. The cord tissue allograft was deemed qualified for transplantation by an authorized recovery agency after confirmation of results from donor pre-screening lab tests, specifying the latter to be free from risk factors and active infections of applicable communicable disease agents and diseases as required by the FDA, including (but not limited to) HIV I/II Ab: Human Immunodeficiency Virus Types 1⁄2 and O Antibody, HIV/HCV/HBV nucleic acid testing (NAT): Human Immunodeficiency/Hepatitis C/B, HBc Ab: Hepatitis B Core Antibody, HBx Ag: Hepatitis B viral Protein, rapid plasma reagin (RPR)/serologic test for syphilis (STS) or Equivalent: Syphilis, HCV Ab: Hepatitis C Virus, and HTLV I/II: Human T-Cell Lymphotropic Virus. The aforementioned investigational drug contains little to no human leucocyte antigens (HL-A), hereby accounting for a significantly reduced risk of HL-A antibody production and thus increased immunologic safety [32].

In accordance with FDA Article 21 CFR Part 1271, the product was stored in a cryopreserved vial and maintained at –80 C or colder using an ultra-low temperature freezer or liquid nitrogen until preparation for treatment. Each vial was intended for use in one patient, on a single occasion only and administered by the principal investigator.

Suspension material was transported frozen in liquid nitrogen just prior to the application. The frozen vials containing the acellular suspensions were opened in a sterile working area. The material was allowed to thaw at room temperature for 15–20 minutes. The therapeutic suspension was then aspirated through a 22 G needle under sterile conditions into a sterile 2 cc syringe and then injected.

Similarly, six patients received a single-time intracavernosal injection using 2 cc of saline. The procedure was performed as described above. IIEF-5 scores as well as blood pressure and resting heartrate were obtained at baseline and follow-up. In addition, sexual intercourse success and erectability were investigated in the frame of interviews during both visits.

Statistical analysis was performed in SPSS Version 26 (IBM, Armonk, NY, USA). Data are presented as mean ± standard deviation (SD). A paired student’s t-test was used to test for significant variations before and after the investigated treatment. Furthermore, the two groups (stem cell injections vs historic control) were compared using an independent samples Welch t test. Differences with p values < 0.05 were considered statistically significant.

3. Results

Twenty male patients ages 31 to 77 (53.05 ± 12.71 years) years were included in the analysis, six additional patients served as a historic control (57.67 ± 14.19 years; p = 0.5 vs intervention group). All participants self-reported ED with a significant impact on their quality of life since at least one year prior to the clinic visit. ED was considered vasculogenic in origin for all patients. All patients reported to have a sexual partner. None of the patients were diagnosed with Peyronie’s disease or a history of prostate cancer, prostatectomy or hormone therapy. In the intervention group, one patient had diabetes and was controlled with medication and diet. Three patients had a history of controlled hypertension and were on oral antihypertensives. One patient had a history of coronary artery disease in the past and was in a stable condition. Moreover, the medical history of patients in the historic control group complied with both inclusion and exclusion criteria for the active trial arm. All controls had a history of controlled hypertension, three presented with hyperlipidemia, two had prediabetes, and one patient had a history of a minor stroke. No other significant internal diseases or surgical histories were reported in either subcohort. All twenty patients in the intervention group reported a prior history of PDE5i use, however, no further treatment methods were undertaken by any of the participants. Equally, all six individuals in the control reported a history of unsuccessful PDE5i use, which was discontinued before the intervention. At the time of study enrollment all patients were advised not to use any therapeutic agents or mechanic treatment methods (i.a. PDE5i, hormone therapy, local injections, intraurethral suppositories, vacuum erection devices) until the end of the observation period. At follow-up, none of the patients reported any change in their home medication regimen and confirmed that they did not use PDE5i, hormone substitution such as testosterone injections, and there was no other significant change regarding the use of supplement or changes in dietary habits. Demographics are presented in Table 1.

Table 1.Patient data.
Characteristics (n = 26) Baseline 6-month- Follow-up
Age (years) p = 0.5
Intervention group (n = 20) 53.05 ± 12.71
Historic control (n = 6) 57.67 ± 14.19
IIEF-5 p = 0.21 p 0.05
Intervention group 12.9 ± 4.47 18 ± 3.37 p 0.05
Historic control 11.00 ± 2.53 10.67 ± 3.5 p = 0.064
6MWT (m) 324.41 ± 188.33 353.11 ± 192.59 p 0.05
RR Sys (mmHg) p = 0.38 p = 0.21
Intervention group 133.5 ± 16.01 130.25 ± 13.03 p = 0.12
Historic control 140.5 ± 16.06 138.67 ± 13.17 p = 0.55
RR Dia (mmHg) p = 0.8 p = 0.5
Intervention group 79.9 ± 8.72 77.85 ± 7.1 p 0.05
Historic control 81.33 ± 12.09 81.5 ± 11.74 p = 0.94
HR (bpm) p = 0.25 p 0.05
Intervention group 70.15 ± 12.13 66.95 ± 7.28 p 0.05
Historic control 74 ± 4.52 74.67 ± 5.32 p = 0.6
SF-36 Scores
Physical function 87.75 ± 25.21 89 ± 22.80 p = 0.17
RL physical health 56.25 ± 42.82 68.75 ± 40.45 p 0.05
RL emotional problems 51.67 ± 39.71 61.67 ± 43.63 p = 0.32
Energy/Fatigue 51.57 ± 19.33 57.75 ± 12.3 p 0.05
Emotional wellbeing 56.32 ± 16.28 68.1 ± 11.73 p 0.05
Social functioning 67.5 ± 23.79 76.25 ± 18.98 p 0.05
Bodily pain 82 ± 22.98 82.63 ± 19.01 p = 0.89
General health 58.75 ± 19.86 60.5 ± 18.77 p = 0.46
Health change 51.25 ± 24.97 58.75 ± 20.32 p = 0.14
Data are mean ± SD (SD, Standard Deviation); RL, Role Limitations; IIEF-5, International Index of Erectile Function 5 Questionnaire; 6MWT, Six Minute Walk Test (m, meters); SF-36, Short Form Health Survey; HR, Heart rate (bpm, beats per minute); RR, Blood Pressure (sys, systolic; dia, diastolic) (mmHg, millimeters of mercury). 6MWT and SF-36 results are only available for group 1. p values are presented for differences between treatment group and historic control as well as before and after the respective intervention in each group.
3.1 Erectile Function

At follow-up, every patient in the treatment group self-reported improved erectability including prolonged erectile capabilities and improved intercourse success. At baseline, IIEF-5 scores ranged from 5 (severe ED) to 21 (mild ED) and averages at 12.9 ± 4.47 (mild to moderate ED) at baseline. At follow up, IIEF-5 scores were 18 ± 3.37 (p < 0.05 vs baseline) with a range of 13 (= mild to moderate ED) to 22 (= no ED; Fig. 1). Among the historic controls, no significant changes regarding erectability and intercourse success were reported at the end of the follow-up period. IIEF-5 at baseline ranged from 7 to 13 (mean score = 11 ± 2.53; p = 0.21 vs intervention group). At follow-up, mean scores were 10.67 ± 3.5 and ranged from 5 to 15 (p = 0.64 vs baseline; p = 0.002 vs intervention group, Fig. 2). No data were obtained with regard to the frequency of sexual activity before recruitment and during follow-up in both groups.

Fig. 1.

IIEF-5 Results at Baseline vs Follow-up after acellular stem cell-derived bioactive molecule injections.

Fig. 2.

Comparison of IIEF-5 results between control and intervention group.

3.2 Physical examination and functional capacity

At baseline, the six minute walking distance was 324.41 ± 188.33 m (range 76 m–700 m). At follow-up, the walking distance was 353.11 ± 192.59 m (range 100 m–780 m, p < 0.05 vs baseline; Fig. 3).

A physical examination was performed by a physician prior to the procedure and at follow-up. All participants were hemodynamically stable on both dates. No major changes regarding the over-all health of subjects were reported.

Among patients in the intervention group, heart rate at baseline was 70.15 ± 12.13 bpm and 66.95 ± 7.28 bpm (p < 0.05) at follow-up, respectively. Historic controls measured heart rates of 74 ± 4.52 bpm (p = 0.25 vs intervention group) at baseline and 74.67 ± 5.32 bpm (p = 0.6 vs baseline) at follow-up. At the end of the observation period, patients, who received stem cell injections, exhibited significantly lower heart rates than individuals in the historic control (p < 0.05). In the intervention group, blood pressure at baseline was 133.5 ± 16.01 over 79.9 ± 8.72 mmHg. Blood pressure at follow-up was 130.25 ± 13.03 (p = 0.12 vs baseline) over 77.85 ± 7.1 mmHg (p < 0.05 vs baseline). In the historic control, blood pressure at baseline was 140.5 ± 16.06 (p = 0.38 vs intervention group) over 81.33 ± 12.09 mmHg (p = 0.8 vs intervention group). At follow-up, no significant changes were observed (138.67 ± 13.17 over 81.5 ± 11.74 mmHg, p > 0.05 vs baseline). Moreover, differences between the follow-up blood pressure values of patients in the active trial group and the historic control, respectively, were non-significant (p > 0.05).

Fig. 3.

Six Minute Walk Test Results at Baseline vs Follow-up after acellular stem cell-derived bioactive molecule injections (intervention group).

3.3 Quality of life

SF-36 questionnaire scores for role limitations due to physical health issues increased from 53.62 ± 41.74 at baseline to 64.33 ± 40.39 at follow-up (p < 0.05), energy scores increased from 49.16 ± 18.85 to 55.05 ± 12 (p < 0.05), emotional wellbeing scores were 53.69 ± 15.88 at baseline and 64.90 ± 11.45 at follow-up (p < 0.05), and social functioning scores were 64.33 ± 23.19 at baseline and 72.67 ± 18.51 at follow-up (p < 0.05). Scores regarding physical function, role limitations due to emotional problems, general health, and bodily pain increased slightly but not significantly. Similarly, health changes were 48.86 ± 24.34 at baseline and 56 ± 19.81 at follow-up but did not reach statistical significance (p > 0.05).

3.4 Tolerability and adverse events

Injections were well tolerated by all patients. Seven patients reported mild-to-moderate pain during stem cell injections, which subsided in all shortly after completion. Similarly, two patients of the historic control group proclaimed injection-associated pain, which also receded within minutes after the procedure. No adverse events such as bleeding from the injection sites, hematoma, swelling, discomfort or prolonged pain were reported. No other adverse events were observed or reported during the follow-up period.

4. Discussion

We report the results of the largest ever reported study investigating the effects of intracavernous injections of acellular stem cell-derived bioactive molecules for ED. Stem cell injections resulted in a significant improvement of erectile function as assessed by a standardized IIEF-5 questionnaire. Furthermore, the one-time penile injection was associated with an increased walking distance in a 6-minute walk test implying possible systemic effects despite a strictly local injection. The Quality of Life questionnaire (SF-36) demonstrated improvements in role limitations due to physical health, energy, emotional wellbeing, and social functioning.

Our data are in concordance with preclinical studies that showed stem cells targeting ED-related vasculogenic insufficiencies such as impaired local vasodilation [33], hypoperfusion of sinusoidal spaces [34], and corporeal venous leakage due to veno-occlusive failure [35] through the induction of endothelial cell proliferation secondary to proangiogenic characteristics [33,36,37]. In that context, stem cell therapy generated an increase in the concentration of VEGF [38-44]. Consequently, endothelial cell proliferation was facilitated, thereupon enhancing endothelium content in cavernous tissue as a functional indicator of regenerative processes in the local vasculature [43,45,46]. In general, stem cell therapy was associated with the secretion of a multitude of growth factors, suggesting subsequent facilitation of tissue repair [42,47]. Concomitant with structural modifications, a reversal of intracavernous endothelial malfunction as a result of improved endothelium-derived NO/cGMP signaling [48] has been demonstrated, based on increased cavernous tissue cyclic guanosine monophosphate (cGMP) levels [39] and enhanced concentration of endothelial nitric oxide synthase (eNOS) [38,42] promoting vasodilation in sinusoidal vascular spaces [49].

Furthermore, in vitro analyses of acellular stem cell preparations revealed the presence of proangiogenic and antifibrotic microRNAs (miRNAs) [38,41]. These findings indicate that the therapy could ameliorate anatomic impairments of ED [50-53], thus promoting endogenous regeneration processes. Of interest, the expression of miRNAs was found to be higher in acellular preparations compared to regular stem cell solutions [41].

In addition to expediting tissue regeneration, stem cell contents promote the modulation of the recipients’ immune response. In that context, the production of inflammatory factors (e.g., Interleukin-6, Interleukin-1b, and Tumor-Necrosis Factor α) was shown to be reduced [39]. Further, stem cells effectuated higher activity of superoxide dismutase and reduced malondialdehyde concentration in animal models. Consequently, oxidative stress in form of superoxide radicals, which prevail in aging or diseased organisms, were diminished [42,47].

Moreover, the effect of transplanted stem cells exceeded mere engraftment in damaged tissues but included paracrine activity [54]. In that regard, stem cells were able to both alter their secretome according to the demands of the impaired anatomic structure and modify the paracrine function of host cells in a tissue-specific manner [44].

Administration of mesenchymal stem cells in animal models resulted in a partial improvement of erectile function [45] as demonstrated by a significant increase of the maximal intracavernosal pressure to mean arterial pressure ratio (ICP/MAP ratio) [36-41,45-47,55] with an accumulative tendency upon protracted follow-up periods [49] and higher bioactive factor concentration [41]. While the exact modes of action underlying the treatment responses are still largely elusive, an accretive body of scientific evidence suggests tissue regeneration, anti-inflammatory properties and immunomodulation as pivotal mechanisms [56].

Small scale clinical trials demonstrated beneficial effects of bone-marrow derived [57] and umbilical cord derived [58] MSC injections on ED due to diabetes mellitus. Erectile function significantly improved as measured by IIEF-15 questionnaire and Erection Hardness Survey [57]. Furthermore, patients reported more frequent occurrence of morning erections and improved rigidity, and a decrease of blood glucose was observed, which resulted in a temporary diminution of diabetes medication dosages [58].

In a case series on eight patients with organic ED due to diabetes mellitus, hypertension, hypercholesterolaemia or Peyronie’s disease, Protogerou et al. [59] demonstrated the therapeutic effects of adipose tissue-derived compared to platelet lysate-derived MSCs. The intracavernous injection augmented erectile function as measured by IIEF5 scores, improved penile perfusion and resulted in improved morning erections. No adverse events or side effects were documented. The comparison of platelet-derived and adipose-derived stem cells showed no significant advantage of preparation.

Furthermore, our findings are in concordance with the investigations of Levy et al. on the effects of placental matrix derived stem cells in ED with in-depth investigation of Peyronie disease. Injections were placed intracavernosally, if applicable in and around plaques. Peak systolic velocity increased (p < 0.01 vs baseline) and a reduction of penile curvature and a decrease of plaque volume were observed. In addition, mild but not significant changes in stretched penile length, penile girth, and end-diastolic velocity were noted [60,61].

Moreover, the effect of MSC-derived products on ED following prostatectomy has been investigated [62-64]. A significant increment of erectility as displayed by IIEF-15 domains intercourse satisfaction and erectile function was noted, with alleviating tendencies after one year upon completion of therapy [62,63]. Equally, an increase of Erection Hardness Scale scores and augmentation of penile peak systolic velocity as well as nitric oxide release were observed [63]. Of interest, continent men profited to a greater extent from the intervention (n = 8 recovered patients, IIEF at 6 months follow-up = 17; p = 0.0069, vs baseline) compared to individuals presenting with incontinence (n = 0 recovered patients, IIEF at 1/3/6 month follow-up = 5; p = 0.9999, vs baseline) [64].

We propose that the improvement of erectile function in our study may be caused in part by the proangiogenic properties of stem cell-derived products [33,36,37]. Enhanced penile vascularization and augmented perfusion account for recovered erectability. Furthermore, we did not expect to find changes with regard to physical capacity or quality of life (which is part of our routine evaluation before and after any vascular treatment), however, walking distance and certain domains of quality of life according to the SF-36 questionnaire improved significantly. While direct measurements of vascular properties and reactions exceed the frame of the present study, there can be multiple reasons for the observed data:

(1) Stem cell-derived molecules might exert systemic effects despite the local penile application. Stem cells might provide systemic regenerative effects to restore endothelial function, consequently ameliorating cardiovascular impairments [65,66]. However, this study was not designed to investigate the aforementioned mechanisms.

(2) Increased sexual satisfaction does have a significant impact on emotional wellbeing and overall quality of life [67,68].

We report a small pilot phase study but it has the largest patient sample reported to date using stem cell-derived products for the treatment of ED. There are several limitations to our study as outlined here:

(1) Our findings are based on subjective reporting as well as established questionnaires for sexual function and quality of life.

(2) We did not perform any blood flow measurements or tissue analyses which was beyond the frame of the current pilot phase study.

(3) We did not perform a prospective placebo-controlled study. However, we used historic controls, who received saline injections and had the IIEF-5 questionnaire at baseline and 6 months follow-up (but no SF-36 questionnaire).

(4) There is a lack a long-term follow-up beyond 6 months.

In conjunction with these promising results, there is a rationale for adding diagnostic techniques (i.a. ultrasound, laboratory testing, and nocturnal penile tumescence) for further objectification and consolidation of these findings as well as the conduction of a randomized controlled study in a larger patient cohort.

5. Conclusions

The presented study is the first to demonstrate beneficial effects of intracavernosal injections containing stem cell-derived bioactive molecules on ED in the largest patient sample reported to date. Stem cell treatment of impaired erectile function is a promising therapeutic approach. Large scale clinical controlled trials are warranted to demonstrate further evidence for a generalized acceptance of stem cell treatment for ED outside of clinical studies.

Author contributions

ERS, NB and PB Designed the research study. ES, KMA, NB and AO performed the research. KMA, AO and AAS collected the data. PB provided help and advice on medical analytics. ES, NB and AAS analyzed the data. ES, NB and AAS drafted the article. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

All subjects gave their informed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Institutional Review Board (IRB) of the International Cell Surgical Society (approval number: ICSS-2020-032).

Acknowledgment

We would like to express our gratitude to all those who helped us during the conduction of the study as well as the writing of the present manuscript. In particular, we would like to give thanks to the staff of the Heart Institute of Southern California Hospital at Culver City. Furthermore, we would like to thank the peer reviewers for their valuable remarks and suggestions.

Funding

This study has been funded by Heartstem Inc., Beverly Hills, California.

Conflict of interest

The authors declare no conflict of interest. None of the study personnel were payed for their participation in the research project, funds were solely used to cover the cost of the investigational drug.

References
[1]
NIH Consensus Development Panel on Impotence. NIH Consensus Conference: Impotence. Journal of the American Medical Association. 1993; 270: 83–90.
[2]
Yafi FA, Sharlip ID, Becher EF. Update on the Safety of Phosphodiesterase Type 5 Inhibitors for the Treatment of Erectile Dysfunction. Sexual Medicine Reviews. 2018; 6: 242–252.
[3]
Yafi FA, Jenkins L, Albersen M, Corona G, Isidoir AM, Goldfarb S, et al. Erectily Dysfunction. Nature Reviews Disease Primers. 2017; 2: 16003.
[4]
Vlachopoulos CV, Terentes-Printzios DG, Ioakeimidis NK, Aznaouridis KA, Stefanadis CI. Prediction of cardiovascular events and all-cause mortality with erectile dysfunction: a systematic review and meta-analysis of cohort studies. Circulation: Cardiovascular Quality and Outcomes. 2013; 6: 99–109.
[5]
Johannes CB, Araujo AB, Feldman HA, Derby CA, Kleinman KP, McKinlay JB. Incidence of erectile dysfunction in men 40 to 69 years old: longitudinal results from the Massachusetts male aging study. Journal of Urology. 2000; 163: 460–463.
[6]
Walczak MK, Lokhandwala N, Hodge MB, Guay AT. Prevalence of cardiovascular risk factors in erectile dysfunction. Journal of Gender-Specific Medicine. 2002; 5: 19–24.
[7]
Virag R, Bouilly P, Frydman D. Is impotence an arterial disorder? A study of arterial risk factors in 440 impotent men. Lancet. 1985; 325: 181–184.
[8]
Blumentals WA, Gomez-Caminero A, Joo S, Vannappagari V. Should erectile dysfunction be considered as a marker for acute myocardial infarction? Results from a retrospective cohort study. International Journal of Impotence Research. 2004; 16: 350–353.
[9]
Seftel AD, Sun P, Swindle R. The prevalence of hypertension, hyperlipidemia, diabetes mellitus and depression in men with erectile dysfunction. Journal of Urology. 2004; 171: 2341–2345.
[10]
Kaiser DR, Billups K, Mason C, Wetterling R, Lundberg JL, Bank AJ. Impaired brachial artery endothelium-dependent and –independent vasodilation in men with erectile dysfunction and no other clinical cardiovascular disease. Journal of the American College of Cardiology. 2004; 43: 179–184.
[11]
Solomon H, Man JW, Jackson G. Erectile dysfunction and the cardiovascular patient: endothelial dysfunction is the common denominator. Heart. 2003; 9: 251–253.
[12]
Morrison SJ, Shah NM, Anderson DJ. Regulatory mechanisms in stem cell biology. Cell. 1997; 88: 287–298.
[13]
Lin C, Xin Z, Deng C, Ning H, Lin G, Lue TF. Recent advances in andrology-related stem cell research. Asian Journal of Andrology. 2008; 10: 171–175.
[14]
Gurusamy N, Alsayari A, Rajasingh S, Rajasingh J. Adult Stem Cells for Regenerative Therapy. Progress in Molecular Biology and Translational Science. 2018; 160: 1–22.
[15]
Chatzistamatiou TK, Papassavas AC, Michalopoulos E, Gamaloutsos C, Mallis P, Gontika I, et al. Optimizing isolation culture and freezing methods to preserve Wharton’s jelly’s mesenchymal stem cell (MSC) properties: an MSC banking protocol validation for the Hellenic Cord Blood Bank. Transfusion. 2014; 54: 3108–3120.
[16]
Mallis P, Boulari D, Michalopoulos E, Dinou A, Spyropoulou-Vlachou M, Stavropoulos-Giokas C. Evaluation of HLA-G Expression in Multipotent Mesenchymal Stromal Cells Derived from Vitrified Wharton’s Jelly Tissue. Bioengineering. 2018; 5: 95.
[17]
Dominici M, Le Blanc K, Mueller I, Slaper-Cortenbach I, Marini FC, Krause DS, et al. Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy Position Statement. 2006; 8: 315–317.
[18]
Kourembanas S. Exosomes: vehicles of intercellular signaling, biomarkers, and vectors of cell therapy. Annual Review of Physiology. 2015; 77: 13–27.
[19]
Baglio SR, Pegtel DM, Baldini N. Mesenchymal stem cell secreted vesicles provide novel opportunities in (stem) cell-free therapy. Frontiers in Physiology. 2012; 3: 359.
[20]
Zhang Y, Chopp M, Liu XS, Katakowski M, Wang X, Tian X, et al. Exosomes Derived from Mesenchymal Stromal Cells Promote Axonal Growth of Cortical Neurons. Molecular Neurobiology. 2016; 54: 2659–2673.
[21]
Shao L, Zhang Y, Lan B, Wang J, Zhang Z, Zhang L, et al. MiRNA-Sequence Indicates that Mesenchymal Stem Cells and Exosomes have Similar Mechanism to Enhance Cardiac Repair. BioMed Research International. 2017; 2017: 4150705.
[22]
Bian S, Zhang L, Duan L, Wang X, Min Y, Yu H. Extracellular vesicles derived from human bone marrow mesenchymal stem cells promote angiogenesis in a rat myocardial infarction model. Journal of Molecular Medicine. 2014; 92: 387–397.
[23]
Li T, Yan Y, Wang B, Qian H, Zhang X, Shen L, et al. Exosomes derived from human umbilical cord mesenchymal stem cells alleviate liver fibrosis. Stem Cells and Development. 2013; 22: 845–854.
[24]
Collino F, Bruno S, Incarnato D, Dettori D, Neri F, Provero P, et al. AKI Recovery Induced by Mesenchymal Stromal Cell-Derived Extracellular Vesicles Carrying MicroRNAs. Journal of the American Society of Nephrology. 2015; 26: 2349–2360.
[25]
Geiger A, Walker A, Nissen E. Human fibrocyte-derived exosomes accelerate wound healing in genetically diabetic mice. Biochemical and Biophysical Research Communications. 2015; 467: 303–309.
[26]
Nakano M, Nagaishi K, Konari N, Saito Y, Chikenji T, Mizue Y, et al. Bone marrow-derived mesenchymal stem cells improve diabetes-induced cognitive impairment by exosome transfer into damaged neurons and astrocytes. Scientific Reports. 2016; 6: 24805.
[27]
Strong TD, Gebska MA, Burnett AL, Champion HC, Bivalacqua TJ. Endothelium-specific gene and stem cell-based therapy for erectile dysfunction. Asian Journal of Andrology. 2008; 10: 14–22.
[28]
He M, von Schwarz ER. Stem-cell therapy for erectile dysfunction: a review of clinical outcomes. International Journal of Impotence Research. 2021; 33: 271–277.
[29]
Van Kollenburg RAA, de Bruin DM, Wijkstra H. Validation of the Electronic Version of the International Index of Erectile Function (IIEF-5 and IIEF-15): A Crossover Study. Journal of Medical Internet Research. 2019; 22: e13490.
[30]
Enright PL. The six-minute walk test. Respiratory Care. 2003; 48: 783–785.
[31]
Brazier JE, Harper R, Jones NM, O’Cathain A, Thomas KJ, Usherwood T, et al. Validating the SF-36 health survey questionnaire: new outcome measure for primary care. British Medical Journal. 1992; 305: 160–164.
[32]
Slavcev A. Prediction of organ transplant rejection by HLA-specific and non-HLA antibodies - brief literature review. International Journal of Immunogenetics. 2012; 40: 83–87.
[33]
Ignarro LJ, Bush PA, Buga GM, Wood KS, Fukuto JM, Rajfer J. Nitric oxide and cyclic GMP formation upon electrical field stimulation cause relaxation of corpus cavernosum smooth muscle. Biochemical and Biophysical Research Communications. 1990; 170: 843–850.
[34]
Michal, V, Ruzbarsky V. Histological changes in the penile arterial bed with aging and diabetes. Vasculogenic impotance: Proceedings of the First International Conference on Korpus kavernozum Revascularization (pp. 113–119). Springfield. 1980.
[35]
Rajfer J, Rosciszewski A, Mehringer M. Prevalence of Corporeal Venous Leakage in Impotent Men. Journal of Urology. 1988; 140: 69–71.
[36]
Albayrak Ö, Sener TE, Ersahin M, Özbas-Turan S, Ekentok C, Tavukcu HH, et al. Mesenchymal stem cell therapy improves erectile dysfunction in experimental spinal cord injury. International Journal of Impotence Research. 2020; 32: 308–316.
[37]
Matz EL, Thakker PU, Gu X, Terlecki RP, Dou L, Walker SJ, et al. Administration of secretome from human placental stem cell‐conditioned media improves recovery of erectile function in the pelvic neurovascular injury model. Journal of Tissue Engineering and Regenerative Medicine. 2020; 14: 1394–1402.
[38]
Ouyang B, Xie Y, Zhang C, Deng C, Lv L, Yao J, et al. Extracellular Vesicles from Human Urine-Derived Stem Cells Ameliorate Erectile Dysfunction in a Diabetic Rat Model by Delivering Proangiogenic MicroRNA. Sexual Medicine. 2019; 7: 241–250.
[39]
Wang J, Mi Y, Wu S, You X, Huang Y, Zhu J, et al. Exosomes from adipose-derived stem cells protect against high glucose-induced erectile dysfunction by delivery of corin in a streptozotocin-induced diabetic rat model. Regenerative Therapy. 2020; 14: 227–233.
[40]
Li M, Lei H, Xu Y, Li H, Yang B, Yu C, et al. Exosomes derived from mesenchymal stem cells exert therapeutic effect in a rat model of cavernous nerves injury. Andrology. 2018; 6: 927–935.
[41]
Ouyang X, Han X, Chen Z, Fang J, Huang X, Wei H. MSC-derived exosomes ameliorate erectile dysfunction by alleviation of corpus cavernosum smooth muscle apoptosis in a rat model of cavernous nerve injury. Stem Cell Research & Therapy. 2018; 9: 246–257.
[42]
Liu Y, Zhao S, Luo L, Wang J, Zhu Z, Xiang Q, et al. Mesenchymal stem cell‐derived exosomes ameliorate erection by reducing oxidative stress damage of corpus cavernosum in a rat model of artery injury. Journal of Cellular and Molecular Medicine. 2019; 23: 7462–7473.
[43]
Sun X, Luo LH, Feng L, Li DS. Down-regulation of lncRNA MEG3 promotes endothelial differentiation of T bone marrow derived mesenchymal stem cells in repairing erectile dysfunction. Life Sciences. 2018; 208: 246–252.
[44]
Yiou R, Mahrouf-Yorgov M, Trébeau C, Zanaty M, Lecointe C, Souktani R, et al. Delivery of human mesenchymal adipose-derived stem cells restores multiple urological dysfunctions in a rat model mimicking radical prostatectomy damages through tissue-specific paracrine mechanisms. Stem Cells. 2016; 34: 392–404.
[45]
Zhou F, Xin H, Xu YD, Lei HE, Yang BC, Guan RL, et al. Therapeutic effects of adipose-derived stem cells-based micro-tissues on erectile dysfunction in streptozotocin-induced diabetic rats. Asian Journal of Andrology. 2017; 19: 91–97.
[46]
Huang Y, Ning H, Shindel AW, Fandel TM, Lin G, Harraz AM, et al. The effect of intracavernous injection of adipose tissue-derived stem cells on hyperlipidemia-associated erectile dysfunction in a rat model. Journal of Sexual Medicine. 2010; 4: 1391–1400.
[47]
Yang J, Zhang Y, Zang G, Wang T, Yu Z, Wang S, et al. Adipose-derived stem cells improve erectile function partially through the secretion of IGF-1, bFGF, and VEGF in aged rats. Andrology. 2018; 6: 498–509.
[48]
Bivalacqua TJ, Deng W, Kendirci M, Usta MF, Robinson C, Taylor BK, et al. Mesenchymal stem cells alone or ex vivo gene modified with endothelial nitric oxide synthase reverse age-associated erectile dysfunction. American Journal of Physiology: Heart and Circulatory Physiology. 2006; 292: H1278–H1290.
[49]
Abdel Aziz MT, El-Haggar S, Mostafa T, Atta H, Fouad H, Mahfouz S, et al. Effect of mesenchymal stem cell penile transplantation on erectile signaling of aged rats. Andrologia. 2009; 42: 187–192.
[50]
Chen JJ, Zhou SH. Mesenchymal stem cells overexpressing MiR-126 enhance ischemic angiogenesis via the AKT/ERK-related pathway. Cardiology Journal. 2011; 18: 675–681.
[51]
Chen Y, Gorski DH. Regulation of angiogenesis through a microRNA (miR-130a) that down-regulates antiangiogenic homeobox genes GAX and HOXA5. Blood. 2008; 111: 1217–1226.
[52]
Bijkerk R, van Solingen C, de Boer HC, van der Pol P, Khairoun M, de Bruin RG, et al. Hematopoietic microRNA-126 protects against renal ischemia/reperfusion injury by promoting vascular integrity. Journal of the American Society of Nephrology. 2014; 25: 1710–1722.
[53]
Chistiakov DA, Orekhov AN, Bobryshev YV. The role of miR-126 in embryonic angiogenesis, adult vascular homeostasis, and vascular repair and its alterations in atherosclerotic disease. Journal of Molecular and Cellular Cardiology. 2016; 97: 47–55.
[54]
User HM, Hairston JH, Zelner DJ, McKenna KE, McVary KT. Penile weight and cell subtype specific changes in a post-radical prostatectomy model of erectile dysfunction. Journal of Urology. 2003; 169: 1175–1179.
[55]
Mangir N, Akbal C, Tarcan T, Simsek F, Turkeri L. Mesenchymal stem cell therapy in treatment of erectile dysfunction: autologous or allogeneic cell sources? International Journal of Urology. 2014; 21: 1280–1285.
[56]
Najar M, Bouhtit F, Melki R, Afif H, Hamal A, Fahmi H, et al. Mesenchymal Stromal Cell-Based Therapy: New Perspectives and Challenges. Journal of Clinical Medicine. 2019; 8: 626.
[57]
Al Demour S, Jafar H, Adwan S, AlSharif A, Alhawari H, Alrabadi A, et al. Safety and Potential Therapeutic Effect of Two Intracavernous Autologous Bone Marrow Derived Mesenchymal Stem Cells injections in Diabetic Patients with Erectile Dysfunction: an Open Label Phase I Clinical Trial. Urologia Internationalis. 2018; 101: 358–365.
[58]
Bahk JY, Jung JH, Han H, Min SK, Lee YS. Treatment of diabetic impotence with umbilical cord blood stem cell intracavernosal transplant: preliminary report of 7 cases. Experimental and Clinical Transplantation. 2010; 8: 150–160.
[59]
Protogerou V, Michalopoulos E, Mallis P, Gontika I, Dimou Z, Liakouras C, et al. Administration of Adipose Derived Mesenchymal Stem Cells and Platelet Lysate in Erectile Dysfunction: a Single Center Pilot Study. Bioengineering. 2019; 6: 21.
[60]
Levy JA, Marchand M, Iorio L, Cassini W, Zahalsky MP. Determining the Feasibility of Managing Erectile Dysfunction in Humans with Placental-Derived Stem Cells. Journal of the American Osteopathic Association. 2016; 116: e1–e5.
[61]
Levy JA, Marchand M, Iorio L, Zribi G, Zahalsky MP. Effects of Stem Cell Treatment in Human Patients with Peyronie Disease. Journal of the American Osteopathic Association. 2015; 115: e8–e13.
[62]
Yiou R, Hamidou L, Birebent B, Bitari D, Le Corvoisier P, Contremoulins I, et al. Intracavernous Injections of Bone Marrow Mononucleated Cells for Postradical Prostatectomy Erectile Dysfunction: Final Results of the INSTIN Clinical Trial. European Urology Focus. 2017; 3: 643–645.
[63]
Yiou R, Hamidou L, Birebent B, Bitari D, Lecorvoisier P, Contremoulins I, et al. Safety of Intracavernous Bone Marrow-Mononuclear Cells for Postradical Prostatectomy Erectile Dysfunction: an Open Dose-Escalation Pilot Study. European Urology. 2016; 69: 988–991.
[64]
Haahr MK, Jensen CH, Toyserkani NM, Andersen DC, Damkier P, Sørensen JA, et al. Safety and Potential Effect of a Single Intracavernous Injection of Autologous Adipose-Derived Regenerative Cells in Patients with Erectile Dysfunction Following Radical Prostatectomy: an Open-Label Phase i Clinical Trial. EBioMedicine. 2016; 19: 204–210.
[65]
Lin YL, Yet SF, Hsu YT, Wang GJ, Hung SC. Mesenchymal Stem Cells Ameliorate Atherosclerotic Lesions via Restoring Endothelial Function. Stem Cells Translational Medicine. 2015; 4: 44–55.
[66]
Chung E. Stem cell therapy in diabetic men with erectile dysfunction: a step closer to safe and effective regenerative technology. Annals of Translational Medicine. 2019; 7: S40.
[67]
Rosen RC, Seidman SN, Menza MA, Shabsigh R, Roose SP, Tseng LJ, et al. Quality of life, mood, and sexual function: a path analytic model of treatment effects in men with erectile dysfunction and depressive symptoms. International Journal of Impotence Research. 2004; 16: 334–340.
[68]
Flynn KE, Lin L, Watkins Bruner D, Cyranowski JM, Hahn EA, Jeffrey DD, et al. Sexual Satisfaction and the Importance of Sexual Health to Quality of Life Throughout the Life Course of US Adults. Journal of Sexual Medicine. 2016; 13: 1642–1650.
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