Tailoring hyaluronic acid hydrogels: Impact of cross-linker length and density on skin rejuvenation as injectable dermal fillers and their potential effects on the MAPK signaling pathway suppression
Mohanapriya Murugesan, Ramya Mathiyalagan, Zelika Mega Ramadhania, Jinnatun Nahar, Cuong Hung Luu, V.H. Giang Phan, Deok Chun Yang, Qihui Zhou, Se Chan Kang, Thavasyappan Thambi
Abstract
Hyaluronic acid (HA) hydrogels, obtained through cross-linking, provide a stable 3D environment that is important for controlled delivery and tissue engineering applications. Cross-linking density has a significant impact on the physicochemical properties of hydrogels, including their shape stability, mechanical stiffness and macromolecular diffusivity. However, often cross-linking chemistries require photoinitiator and catalyst that may be toxic and cause unwanted tissue response. Here, we prepared a series of HA hydrogel with varying cross-linker length and cross-linking density, which can be obtained by altering the feed ratio of three different cross-linkers from small molecules to macromolecules (e.g., 1,4-butanediol diglycidyl ether (BDDE), ferulic acid (FA), pluronic (PLU)), to ameliorate skin wrinkles in mice models. HA cross-linked with FA and PLU exhibited enzyme and temperature-dependent sol-to-gel phase transition, respectively, and the gels possess good injectability. In vitro test confirmed that HA hydrogels co-cultured with RAW 264.7 and HDF cells showed good biocompatibility. In particular, HA cross-linked with PLU stimulated the growth of HDF cells and HaCaT cells. HA cross-linked with PLU suppressed the expression levels of proteins involved in collagen degradation including mitogen-activated protein kinases (ERK, JNK, p38) and matrix metalloproteases (MMP-1, MMP-3, and MMP-9) resulting in increased deposition of Collagen I. The free-flowing sols of HA hydrogel precursors are subcutaneously injected into the back of BALB/c mice and form stable gels at the dermis layer and found to be non-toxic. More importantly, HA hydrogel cross-linked with PLU showed an enhanced anti-wrinkling effect in the wrinkled mice model. Thus, properties of HA hydrogels such as injectability, biocompatibility, and good anti-wrinkling effect altered through varying cross-linking density must be considered in the context of soft tissue engineering applications.