Secretome from bone marrow mesenchymal stem cells: A promising, cell-free therapy for allergic rhinitis.

Allergic rhinitis (AR), characterized by the symptoms of sneezing, rhinorrhea, itchiness and nasal blockage, is a type I allergic disease of nasal mucosa, which is mainly mediated by IgE after exposure to allergens. At present, general drug therapy is limited to alleviating allergic symptoms but fails to regulate the allergic reaction; the recurrence of symptoms and the side effects of the drugs make many patients with AR resist treatments and bring serious impacts on the quality of life. Bone marrow mesenchymal stem cells (BMSCs) are a population of adult stem cells with multipotential differentiation capability, low immunogenicity, and immunoregulatory effects. The unique immunoregulatory properties of BMSCs make them hold great promise in the treatment of chronic inflammation and immune disorders through a paracrine mechanism of anti-inflammatory and anti-allergic effects. The stem cell secretome is defined as the set of molecules secreted to the extracellular space. The secretome such as conditioned media (CM) obtained from BMSCs contains various bioactive molecules and vesicular elements, which may act as therapeutic mediators to support their immunoregulatory effects. Therefore, we hypothesize that the BMSCs secretome may represent a promising treatment for AR by anti-allergic effects via the paracrine mechanism.