In the absence of skin innervation, wound healing is delayed and chronic nonhealing wounds may occur. Keratinocytes produce neurotrophic factors, such as nerve growth factor (NGF), which has been suggested to attract primary cutaneous afferent axons and exert mitogenic effects on keratinocytes. The present study was performed to examine the interaction of primary human keratinocytes (hKTs) and rat cutaneous primary afferent dorsal root ganglion (DRG) neurons with regard to neuritic outgrowth and keratinocyte proliferation. Neuritic outgrowth was assessed with neurofilament immunostaining where cell bodies and fine neuritic processes were identified. Neuritic outgrowth of neurons alone in culture is spatially random and radial. Neurites in cocultures of DRG neurons insinuated between the hKTs and grew to “clumps” of hKTs within the cultures. Immunostaining with anti-NGF antibody indicates that hKTs expressed the neurotrophin NGF. Proliferation of keratinocytes was significantly enhanced in coculture with DRG and hKT, and NGF levels were increased as compared to DRG or hKT culture alone. These results indicate a dynamic interaction between DRG neurons and hKTs whereby the DRG neurons issue neurites in association with hKTs and the hKTs up-regulate NGF and increase their proliferation rate. These findings support the hypothesis that nerve-skin interactions play a significant role in wound healing.
From the *Department of Plastic, Hand- and Reconstructive Surgery, Hannover Medical School, Hannover, Germany; †Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven; and ‡Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT.
Received June 30, 2012, and accepted for publication, after revision, September 28, 2012.
Conflicts of interest and sources of funding: Supported in part by the Medical and Research and Development Services of the Department of Veterans Affairs, the NIH and the National Multiple Sclerosis Society.
Reprints: Christine Radtke, MD, PhD, Department of Plastic, Hand- and Reconstructive Surgery, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover Germany. E-mail: firstname.lastname@example.org.