This proposal explores cell signaling pathways that occur between cutaneous sensory nerve fibers and endothelial cells during response to cutaneous injury. Wounds persist as a US health care crisis in spite of progress in understanding biological responses to cutaneous injury. With increased patient survival following large burn injuries, disability due to hypertrophic scar formation has become an important clinical problem that affects as many as 100,000 patients per year in the United States. The scars have hypervascularity and increased innervation. In contrast, non-healing ulcers of diabetes mellitus have microangiopathy and decreased innervation. We anticipate that in hypertrophic scars increased endothelial cell proliferation and neurotrophin synthesis leads to the hypervascularity and pruritis. Our long term hypothesis is that following cutaneous injury, 1) sensory nerve fibers secrete neuropeptides such as substance P that regulate endothelial cell response to injury and 2) microvascular endothelial cells secrete neurotrophins that regulate nerve fiber regeneration. We will test our hypothesis by addressing the following aims: 1) To determine effects of nervederived mediators on inflammatory responses by endothelial cells. Given our data on the beneficial effects of modulating neuroinflammatory responses to injury in diabetic wound healing with substance P, we will determine whether progenitor or adult neural cells enhance microvascular dermal endothelial cell responses in vitro. We will use RNA interference to deplete the neurokinin 1 receptor. Finally, we will modulate the system to determine whether glucose and fatty acids perturb neuro-endothelial interactions. 2) To determine whether the neuropeptide, alpha melanocyte stimulating hormone regulates endothelial cell inflammatory responses, proliferation or migration. Whereas our focus for the past 8 years has been on the proinflammatory effects of substance P, neurons also negatively regulate inflammation. The neuropeptide alpha melanocyte stimulating hormone regulates has been shown to inhibit inflammatory responses. We will use RNA interference to determine effect of melanocortin 1 receptor loss-of-function on endothelial cell inflammatory responses, proliferation and migration. 3) To determine how manipulation of neuropeptide activity in mutant diabetic mice with delayed wound healing alters response to injury. We will determine whether topical application of supernate from cultured neural cells alters wound repair processes in a validated model of impaired wound healing, the mutant db/db mouse model. The rationale for these experiments is to restore neuroinflammation in the wound bed to enhance endothelial cell responses to injury. We will apply supernatant from either dorsal root ganglion cells or progenitor neural cells and determine whether they enhance wound healing kinetics, epithelialization, inflammation, angiogenesis, contraction or temporal neuropeptide expression.
In this competing renewal of our project to establish that nerves regulate endothelial cell responses to cutaneous injury, we propose that the novel concept that neural progenitor cells could improve the deficient neuroinflammatory responses to injury that occur in neuropathic tissue such as chronic diabetic wounds. We will employ siRNA to deplete neuropeptide receptors on endothelial cells to further define neural modulation of endothelial cell inflammatory responses, migration and proliferation.
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