Mesenchymal stem cell secretome to control inflammation in allergic conjunctivitis.

Su and colleagues (1) propose the use of culture medium from TNF-α pre-conditioned bone marrow-derived mesenchymal stem cells (MSC) as a novel therapeutic strategy for treating allergic conjunctivitis. MSC were exposed to TNF-α and conditioned medium was topically applied in the conjunctiva of mice with short ragweed pollen-induced experimental allergic conjunctivitis. Interestingly, ocular administration of TNF-α-conditioned medium reduced clinical signs and symptoms of allergic conjunctivitis. The anti-allergic effect of TNF-α-conditioned medium appeared to be due to the reduction of inflammatory cells infiltration and accumulation in the conjunctiva, inhibition of B cells, mast cells and histamine functions, through a COX-2-dependent mechanism. In fact, pre-treating MSC with COX-2 siRNA, the anti-allergic effects were abrogated. It seems that factors produced by MSC treated with TNF-α exert anti-allergic properties targeting simultaneously several key mediators of allergic reaction like B cells, mast cells, histamine and T helper 2 (Th2) cells.