FIG. 6.

Immunohistochemical analysis of the 3D skin lip construct for keratins K13, K19, K4, and K10. In the top image, keratin 10 is seen decreasing (in the direction of the arrow) from a strong expression in the skin area, disappearing toward the oral part. A magnified view is presented in the second row. Keratin 19 (third row) is clearly seen (arrow) in basal cells of the oral part of the lip construct and is absent in the skin part. Both K13 and K4 were also negative in the skin areas of the construct. K13 and K4, which are strongly present in the native tissue, as shown in Figure 5, are only lightly present (K13) or absent (K4) in the construct. At this stage in the development of the in vitro lip substitutes it appears that the best markers to identify both the epithelial and oral areas are K10 and K19, respectively. Color images available online at www.liebertonline.com/tec