Copper Complexes with New Glycyl-l-histidyl-l-lysine-Hyaluronan Conjugates Show Antioxidant Properties and Osteogenic and Angiogenic Synergistic Effects.
This study investigated the synthesis and biological activity of novel conjugates combining hyaluronic acid (HA) with the copper-binding tripeptide glycyl-l-histidyl-l-lysine (GHK) at varying loading ratios, forming GHK-HA conjugates. The conjugates were designed to address the individual limitations of HA and GHK, including susceptibility to hydrolytic degradation and oxidative stress. In vitro assays demonstrated that GHK-HA bound copper(II) ions effectively and showed enhanced antioxidant properties compared to the individual components alone. When complexed with copper, the conjugates promoted the expression and release of several growth and trophic factors, including brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and bone morphogenetic protein-2 (BMP-2), suggesting synergistic osteogenic and angiogenic potential. The study also explored a proposed mechanistic pathway, finding that copper's intracellular chaperones — CCS and Atox1 — translocated to the nucleus and appeared to function as transcription factors. Limitations include the exclusively in vitro nature of the experiments, meaning results cannot yet be extrapolated to animal models or human clinical outcomes. No in vivo validation was performed.
Why this grade: All experimental findings were generated exclusively in cell-based in vitro assays with no animal or human data, providing no direct evidence of clinical efficacy.
In recent years, hyaluronic acid (HA) and the natural tripeptide glycyl-l-histidyl-l-lysine (GHK), especially its copper(II) complex (GHK-Cu), individually have been shown to exert helpful properties for bone protection and regeneration. However, they are not strong enough to handle oxidative stress, hydrolytic attack, or environmental conditions. Being aware that conjugation chemistry has recently emerged as an appealing approach for generating new molecular entities capable of preserving the molecular integrity of their moieties or delaying their degradation, herein we present the synthesis of conjugates of HA with GHK (GHK-HA), at different loadings of the tripeptide. GHK-HA binds copper(II) ions and potentiates the chemical and biological properties of the two components in in vitro assays. The results highlight copper's role in promoting the expression and release of certain trophic, angiogenic, and osteogenic factors, including brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), as well as bone morphogenetic protein-2 (BMP-2). The protective and regenerative activities of the metal ion are related to the translocation of its intracellular chaperones Copper Chaperone for Superoxide Dismutase (CCS) and Antioxidant-1 (Atox1) to the nucleus where they act as transcription factors.
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