Non-invasive visualization of epidermal responses to injury using a fluorescent transgenic reporter.

We describe transgenic mice in which expression of a reporter, the yellow fluorescent protein (YFP), is locally activated in epidermal cells at sites of injury. YFP is detectable a day after injury; its levels peak within 3 d, and then decline over the subsequent week. Expression is also activated by a chemical irritant, and is suppressed by topical administration of hydrocortisone. These mice permit non-invasive time-lapse monitoring of responses to injury in vivo. They can be used to detect epidermal activation and to test agents that may provoke or attenuate epidermal responses.