The ability to suppress macrophage-mediated inflammation in orbital fat stem cells is controlled by miR-671-5p

Lien, Gi-Shih; Liu, Jen-Fang; Chien, Ming-Hsien; Hsu, Wei-Tse; Chang, Tzu-Hao; Ku, Chia-Chi; Ji, Andrea Tung-Qian; Tan, Peng; Hsieh, Ting-Lieh; Lee, Liang-Ming; Ho, Jennifer H

Macrophages may initiate immune reaction through releasing proinflammatory cytokines including TNFα and IL-1 [34] . Macrophages resident in tissues can be polarized as proinflammatory macrophages (M1) or M2 by the microenvironment [35, 36] . M1 exhibit proinflammatory activity to activate T-helper type 1 lymphocytes, while M2 promote T-helper type 2 responses via increasing phagocytic activities [34] [35] [36] . Different from bone marrowderived MSCs and gingiva-derived MSCs, OFSCs did not promote M2 generation ( Figure 1C ) but did significantly reduce the proinflammatory function of M1 by inhibition of TNFα, IL-1α and IL-1β (Figure 3 ) in the first 6 hours, indicating that orbital fat-derived MSCs regulate macrophages by targeting M1 rather than M2. However, we cannot exclude the possibility of M2 polarization induction by OFSCs through direct cell-cell interaction or longterm paracrine stimulation. In addition, we did measure the miR-671-5p expression in MSCs derived from different tissue origins. The data showed that miR-671-5p is strongly expressed in OFSCs, is moderately expressed in MSCs derived from subcutaneous fat tissue, and is at a very low level in MSCs derived from bone marrow ( Table 2 ), indicating that regulation of M1 by miR-671-5p may predominantly exist in adipose tissue-derived MSCs. IDO secretion from MSCs participating in immune tolerance and anti-inflammation could be stimulated by proinflammatory cytokines such as IL-1, IFNγ and TNFα [11, 12, 15, 16, 31] . From our data, LPS-activated macrophages enhanced the expression of TNFα, IL-1α and IL-1β ( Figures 3B,C,D) , and IDO in OFSCs was responsible for LPS-activated macrophage ( Figure 4C ). In addition to IDO, IL-10, sTNFR type II, and IL-1RA in OFSCs were also induced by activated macrophages (Figure 4) . IL-10 is a strong inhibitor for proinflammatory cytokine and chemokine release from activated macrophages [37] . Németh and colleagues report that bone marrowderived MSCs reduce mortality and improve organ function in experimental cecal ligation-induced sepsis directly through increasing IL-10 production from LPS-activated macrophages [38] . According to our data, LPS-activated macrophages could also upregulate IL-10 expression in OFSCs ( Figure 4B ), and enhancement of IL-10 may justify the effect of OFSCs on suppression of macrophage proinflammatory cytokine release.