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Growth factors (GFs) act as important active molecules for the treatment of skin wounds. However, their clinical translation is seriously restrained due to single function and short half-life. Besides, the underlying GFs-mediated wound healing mechanism remains elusive. Therefore, we aimed to develop a thermo-sensitive chitosan hydrogel embedding with poly lactic-co-glycolic acid (PLGA) microspheres which can deliver platelet-derived growth factor receptor (PDGF) for wound healing. The generated PDGF-PLGA hydrogel was systematically evaluated for its wound healing efficiency by the in vivo experiments, including biocompatibility testing, cell proliferation and migration, wound closure rate, granulation tissue formation and collagen deposition. Further, the expression levels of autophagy-related proteins were detected. The results showed that the PDGF-PLGA hydrogel exhibited excellent cell compatibility, cell proliferation and migration. The PDGF-PLGA hydrogel was superior to PDGF alone and control groups in promoting wound closure, granulation tissue formation and collagen synthesis. In addition, the autophagy levels were significantly decreased by PDGF hydrogel in wound tissue of treated mice as compared with PDGF alone and control groups. We also found that the autophagy activator rapamycin delayed PDGF hydrogel-mediated wound healing. This study provides a novel mechanism for the beneficial effects of PDGF-PLGA hydrogel on the wound repair.

Flooding of soils often results in hypoxic conditions surrounding plant roots, which is a harmful abiotic stress to crops. Hydrogen sulfide (H2S) is a highly diffusible, gaseous molecule that modulates cell signaling and is involved in hypoxia signaling in animal cells. However, there have been no previous studies of H2S in plant cells in response to hypoxia. The effects of H2S on hypoxia-induced root tip death were studied in pea (Pisum sativum) via analysis of endogenous H2S and reactive oxygen species (ROS) levels. The activities of key enzymes involved in antioxidative and H2S metabolic pathways were determined using spectrophotometric assays. Ethylene was measured by gas chromatography. We found that exogenous H2S pretreatment dramatically alleviated hypoxia-induced root tip death by protecting root tip cell membranes from ROS damage induced by hypoxia and by stimulating a quiescence strategy through inhibiting ethylene production. Conversely, root tip death induced by hypoxia was strongly enhanced by inhibition of the key enzymes responsible for endogenous H2S biosynthesis. Our results demonstrated that exogenous H2S pretreatment significantly alleviates hypoxia-induced root tip death in pea seedlings and, therefore, enhances the tolerance of the plant to hypoxic stress.