Bone marrow-derived clonal mesenchymal stem cells inhibit ovalbumin-induced atopic dermatitis.

Mesenchymal stem cells (MSCs) possess immunomodulatory activities, including suppression of T- and B-cell activation. However, their effects on atopic dermatitis (AD) have not yet been studied. Using an ovalbumin-induced AD mouse model, we investigated whether MSCs can be used as therapeutics in AD. We isolated both allogeneic and syngeneic clonal MSCs (cMSCs) from mouse bone marrow according to the subfractionation culturing method. Our cMSCs suppressed both T- and B-cell activation. T-cell proliferation and cytokine production, including interferon (IFN)-γ and interleukin (IL)-4, were suppressed by inhibition of transcription factors, such as T-bet, GATA-3, and c-Maf. Those transcription factors were nitric oxide dependent. Immunoglobulin E (IgE) suppression occurred through downregulation of AID and BLIMP-1, important regulators for isotype class switch and B-cell differentiation. The cMSCs were injected intravenously into ovalbumin-induced AD mouse model, and the therapeutic effects were analyzed. Injection of both allogeneic and syngeneic cMSCs in an AD mouse model inhibited cell infiltration in skin lesions and decreased the serum level of IgE. IL-4 expression was also suppressed by cMSCs in both the lymph node and skin. The cMSCs migrated to skin lesions and draining lymph nodes. Taken together, these data demonstrated that cMSCs, which suppressed T- and B-cell functions, can be used for the treatment of AD in mice.

Mesenchymal stem cells infected with Mycoplasma arginini secrete complement C3 to regulate immunoglobulin production in B lymphocytes.

Mesenchymal stem cells (MSCs) have immunomodulatory functions such as the suppression of T and B cells. MSCs suppress immunoglobulin (Ig) production by B cells via cell-cell contact as well as via secretion of soluble factors. Our study showed that the conditioned medium (CM) of MSCs infected with a mycoplasma strain, Mycoplasma arginini, has marked inhibitory effects on Ig production by lipopolysaccharide/interleukin-4-induced B cells compared with mycoplasma-free MSC-CM. We analyzed mycoplasma-infected MSC-CM by fast protein liquid chromatography and liquid chromatography to screen the molecules responsible for Ig inhibition. Complement C3 (C3) was the most critical molecule among the candidates identified. C3 was shown to be involved in the suppression of the Ig production of B cells. C3 was secreted by mycoplasma-infected MSCs, but not by mycoplasma-free MSCs or B cells. It was able to directly inhibit Ig production by B cells. In the presence of a C3 inhibitor, Ig inhibition by MSC-CM was abrogated. This inhibitory effect was concomitant with the downregulation of B-cell-induced maturation protein-1, which is a regulator of the differentiation of antibody-secreting plasma cells. These results suggest that C3 secreted from mycoplasma-infected MSCs has an important role in the immunomodulatory functions of MSCs. However, its role in vivo needs to be explored.