vascularization CD31 NORMAL HUMAN SKIN 3D SKIN BILAYERED EQUIVALENT 3D SKIN THREELAYERED EQUIVALENT COLLAGEN IV NORMAL HUMAN SKIN 3D SKIN BILAYERED EQUIVALENT 3D SKIN THREELAYERED EQUIVALENT COLLAGEN XVIII NORMAL HUMAN SKIN 3D SKIN BILAYERED EQUIVALENT 3D SKIN THREELAYERED EQUIVALENT EN4 NORMAL HUMAN SKIN 3D SKIN BILAYERED EQUIVALENT 3D SKIN THREELAYERED EQUIVALENT ENDOSTATIN NORMAL HUMAN SKIN 3D SKIN BILAYERED EQUIVALENT 3D SKIN THREELAYERED EQUIVALENT LAMININ NORMAL HUMAN SKIN 3D SKIN BILAYERED EQUIVALENT 3D SKIN THREELAYERED EQUIVALENT PODOPLANIN NORMAL HUMAN SKIN 3D SKIN BILAYERED EQUIVALENT 3D SKIN THREELAYERED EQUIVALENT