1. Research Unit of Histology and Embriology, Department of Clinical and Experimental Medicine, University of Florence, 50121 Firenze, Italy
2. Department of Health Sciences, Division of Dermatology, University of Florence, 50121 Firenze, Italy
3. S. Raffaele Hospital, 20158 Milan, Italy
4. Research Unit of Histology and Embriology, Department of Biology, University of Florence, 50121 Firenze, Italy