NGF accelerates cutaneous wound healing by promoting the migration of dermal fibroblasts via the PI3K/Akt-Rac1-JNK and ERK pathways.

As a well-known neurotrophic factor, nerve growth factor (NGF) has also been extensively recognized for its acceleration of healing in cutaneous wounds in both animal models and randomized clinical trials. However, the underlying mechanisms accounting for the therapeutic effect of NGF on skin wounds are not fully understood. NGF treatment significantly accelerated the rate of wound healing by promoting wound reepithelialization, the formation of granulation tissue, and collagen production. To explore the possible mechanisms of this process, the expression levels of CD68, VEGF, PCNA, and TGF-ß1 in wounds were detected by immunohistochemical staining. The levels of these proteins were all significantly raised in NGF-treated wounds compared to untreated controls. NGF also significantly promoted the migration, but not the proliferation, of dermal fibroblasts. NGF induced a remarkable increase in the activity of PI3K/Akt, JNK, ERK, and Rac1, and blockade with their specific inhibitors significantly impaired the NGF-induced migration. In conclusion, NGF significantly accelerated the healing of skin excisional wounds in rats and the fibroblast migration induced by NGF may contribute to this healing process. The activation of PI3K/Akt, Rac1, JNK, and ERK were all involved in the regulation of NGF-induced fibroblast migration.

bFGF expression mediated by a hypoxia-regulated adenoviral vector protects PC12 cell death induced by serum deprivation.

Basic fibroblast growth factor (bFGF) is a known neuroprotectant against a number of brain injury conditions such as cerebral ischemia. However, bFGF also regulates a plethora of brain developmental processes and functions as a strong mitogen. Therefore, unregulated long-term expression of bFGF in brain may potentially be tumorigenic, limiting its utility in brain therapy. Here, we report the successful construction of an adenoviral vector (Ad-5HRE-bFGF) expressing bFGF under the regulation of five hypoxia-responsive elements (5HRE) and a minimal cytomegalovirus promoter (CMVmp). Following hypoxia treatment in a hypoxic chamber with less than 1% of oxygen, Ad-5HRE-bFGF induced a significant and time-dependent expression of bFGF protein and the fluorescent tag, humanized GFP (hrGFP) protein, in infected PC12 cells. In contrast, normoxia treatment evoked extremely low level of bFGF and hrGFP expression, demonstrating that the 5HRE-CMVmp cassette was effective in regulating the expression of bFGF gene in response to hypoxia. More importantly, bFGF expressed by the Ad-5HRE-bFGF viral vector under the regulation of hypoxia was significantly neuroprotective against PC12 cell death evoked by serum deprivation. Taken together, these studies demonstrated the feasibility to express bFGF in a hypoxia-regulated fashion to provide neuroprotection. The Ad-5HRE-bFGF can be further developed as an effective tool to provide neuroprotection against hypoxia-induced brain diseases, such as cerebral ischemia.