Sildenafil-loaded Lipid-based Nanocarrier as a Potential Therapy for Alopecia Areata: A Randomized Clinical Study

Alopecia areata (AA) is a common cause of nonscarring alopecia that occurs in a patchy, confluent, or diffuse pattern. Many theories were implicated in pathogenesis of AA, such as an autoimmune lymphocytic attack of the hair, genetic basis, and environmental factors. Clinically, AA presents as a well-circumscribed patch of sudden hair loss. It affects any hair bearing area with the scalp being the most commonly affected site .

Dermoscopy is a noninvasive technique for the clinical diagnosis of many skin diseases. Dermoscopy is now considered as a valuable tool in diagnosis of variable skin lesions. Scalp dermoscopy (Trichoscopy) does not only facilitate diagnosis of hair disorders but also give clues about disease stage and progression.

The most common trichoscopic features of AA are yellow dots, micro-exclamation mark hairs, tapered hairs, black dots, broken hairs, and regrowing upright or regrowing coiled hairs. Trichoscopic characteristics have a clinical significance in AA for diagnosis and prognosis.

The treatment of alopecia areata involves promotion of hair growth (for instance with topical minoxidil application), immunosuppression (intralesional or systemic steroid therapy, phototherapy) or immunomodulation (anthralin, dinitrochlorobenzene, diphenylcyclopropenone, squaric acid dibutylester).Unfortunately, there is currently no cure for this chronic disease, and despite the presence of a wide variety of therapeutic options, none is universally proven to induce and/or sustain remission. Development of new drugs and formulations is urgently needed

Sildenafil, a phosphodiesterase 5 (PDE5) inhibitor, is known to increase the intracellular level of cyclic guanosine monophosphate (cGMP), which causes vasodilation. Sildenafil was first approved in 1998 for erectile dysfunction, but since then additional uses for the drug have been found. A previous study demonstrated the significant therapeutic potential of sildenafil on hair growth and proposed its potential use in treatment of alopecia. It has been shown that it enhances proliferation of human dermal papilla cells (hDPCs) and up-regulates the mRNA expression of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF), which are responsible for hair growth. Additionally, sildenafil up-regulates the levels of phosphorylated ERK and accelerates anagen induction by stimulating perifollicular vessel formation after topical application in mice.