Role of hyaluronan tetrasaccharide in macrophage-mediated skin inflammation and collagen remodeling of fibroblasts

Summary: Abstract Body: Hyaluronan (HA) has moisturizing properties and bioactive functions. While the biological effects of HA are primarily influenced by its molecular weight, hyaluronan tetrasaccharide (HA4) remains relatively unexplored. This study investigates HA4’s potential to regulate macrophage-induced inflammation and fibroblast-mediated collagen remodeling, focusing on proinflammatory M1 macrophages (M1-Mφ) associated with photoaging. Adding HA4 during macrophage (M0) differentiation into M1-Mφ partially inhibited this process and significantly reduced the production of proinflammatory cytokines IL-6. Although IL-1ra, an M2 marker, was upregulated, no clear polarization toward antiinflammatory M2 macrophages was detected. The effects of M1-Mφ-conditioned medium (M1-CM) and HA4-supplemented M1-CM (M1+HA4-CM) on human fibroblasts were also examined. Fibroblasts treated with M1+HA4-CM showed a significant reduction in IL-6, IL-8, and the collagen-degrading enzyme MMP1 expression compared to those treated with M1-CM alone. Fibroblast collagen synthesis assays revealed that M1+HA4-CM enhanced collagen fiber formation. These results were supported by RNA-seq, which showed increased collagen synthesis-related genes and decreased collagen degradation-related genes in fibroblasts treated with M1+HA4-CM. Further, TLR4 neutralization assays indicated that the IL-6 suppression found in fibroblasts treated with M1+HA4-CM is independent of the TLR4 signaling pathway. Thus, HA4 mitigates M1-Mφ-induced inflammatory responses and collagen degradation while promoting collagen fiber formation. These findings highlight HA4’s potential for managing inflammatory skin conditions, including photoaging. Eiko Uno¹, Florence Kim¹, Mihoko Yoshino¹, Yasunari Sato¹, Masao Hashimoto¹, Kenji Watanabe², Yoichi Mizukami², Jun Muto³ 1. Fundamental Technology Research Division, Rohto Seiyaku Kabushiki Kaisha, Kyoto, Kyoto Prefecture, Japan. 2. Institute of Gene Research, Yamaguchi Daigaku, Yamaguchi, Yamaguchi Prefecture, Japan. 3. Department of Dermatology, Ehime Daigaku Daigakuin Igakukei Kenkyuka Igakubu, Toon, Ehime Prefecture, Japan. Cell Communication Networks and Stromal Biology