The mechanisms and potential of stem cell therapy for penile fibrosis.

Fibrosis is often caused by chronic tissue injury leading to a persisting inflammatory response with excessive accumulation of extracellular connective tissue proteins. Peyronie's disease, urethral stricture and penile (corpora cavernosa) fibrosis are localized fibrotic disorders of the penile connective tissues that can substantially impair a patient's quality of life. Research over the past few decades has revealed the ability of stem cells to secrete a wide range of paracrine factors, a characteristic that could be exploited therapeutically to prevent and treat several inflammatory and fibrotic diseases. In preclinical studies, mesenchymal stem cells (MSCs) have proven to be the most effective and readily available type of stem cells for therapeutic use. An important advantage of MSCs is their ability to circumvent the immune system and function as immunomodulatory 'drug stores' to influence multiple cell types simultaneously. Many studies using stem cells have been applied exclusively to corpora cavernosa fibrosis owing to its well-established disease models. A plethora of preclinical data suggest the benefit of stem cells for use in penile fibrosis. However, their exact mechanism of action and optimal timing and mode of administration must be determined before clinical translation.