SOAP-INDUCED WINTER XEROSIS 213 Table I Relationship of Skin Xerosis With Stratum Corneum Lipid Composition Skin xerosis grade Lipid species Grade 1 Grade 2 Grade 3 Grade 4 Lipid levels (ng lipid/lxg protein) Ceramides 64.9 +- 34.4 68.6 -+ 30.4 39.2 +- 14.9' 37.5 +- 14.1' Fatty acids 62.1 -+ 34.6 67.4 -+ 32.7 60.5 +- 37.0 54.9 +- 28.1 Cholesterol 3.9 +- 2.1 7.7 -+ 4.2 4.4 -+ 2.0 4.6 -+ 2.3 Relative lipid levels (% of total lipids) Ceramides 47.1 +- 17.4 48.3 -+ 8.6 40.2 + 13.2 38.3 +- 11.2 Fatty acids 49.7 + 18.6 46.2 + 9.8 55.0 + 12.0 56.0 + 10.8 Cholesterol 2.0 -+ 1.9 5.5 +- 2.6 4.8 + 2.4 5.2 + 3.2 Values represent mean +-- standard deviation. Grade 1, n = 8 grade 2, n = 8 grade 3, n = 12' grade 4, n = 12. * Significantly different from grade 1 (p 0.05). Table II Relationship of Skin Xerosis With Stratum Corneum Ceramide Composition Skin xerosis grade Ceramide species Grade 1 Grade 2 Grade 3 Grade 4 Relative lipid levels (% of total lipids) 1 10.6 +__ 2.8 12.4 + 3.6 15.6 + 3.3 15.7 --- 8.4 2 20.2 + 4.2 23.2 + 3.8 24.6 + 3.8 28.6 ___ 6.1 3 18.0 _+ 2.9 17.5 +-- 3.2 17.7 +-- 4.5 16.1 +__ 4.5 3a 10.6 +-- 4.6 6.4 --- 1.5 6.7 --- 3.3 6.7 --- 2.7 4/5 21.8 --- 5.1 22.9 +-- 1.5 20.9 --- 2.5 19.7 -+ 5.4 61 7.0 -+ 3.5 6.0 +-- 1.7 3.7 +-- 2.2 2.4 +-- 1.6 611 12.4 --- 3.1 11.7 --- 1.4 10.4 --- 2.6 9.5 --- 2.7 Values represent mean +--- standard deviation. Grade 1, n = 8 grade 2, n = 8' grade 3, n = 12' grade 4, n = 12. sequence, desmosomal degradation occurred by digestion of the desmosomes' internal components, followed by a widening of the intercellular space and progressive detach- ment from the corneocyte wall. Finally, desmosomal remnants appeared to be sur- rounded with lipid lamellae separating them from the corneocyte envelopes. Similar findings have been reported previously (12,39). The loss of desmosomal attachment has important implications for desquamation, as desmosomes are the principal proteinaceous intercorneocyte linkage molecules (2,8,11) their degradation is a prerequisite to surface corneocyte detachment. Intercellular lipids, however, may also help to reduce intercor- neocyte desmosomal interactions by surrounding the degraded desmosomal structures, or may even act as anti-cohesive elements (8). Nevertheless, reformation of lipid lamellae around the degraded and vacuolated desmosome probably helps to maintain the water barrier. In xerotic stratum corneum, the degradation of desmosomes is apparently perturbed,

214 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table III Relationship of Skin Xerosis With Stratum Comeurn Lipid Composition in the Inner and Outer Layers of the Stratum Corneum Skin xerosis grade Grade 1 Grade 2 Lipid species Outer SC Inner SC Outer SC Inner SC Lipid levels (ng lipid/ng protein) Ceramides 65.8 + 19.3 62.5 --+ 21.0 49.8 --- 23.0 64.5 --- 41.0 Fatty acids 53.0 - 30.6 42.5 - 22.9 64.4 -+ 51.7 39.3 +- 20.2 Cholesterol 6.4 --+ 5.0 5.2 --- 4.1 10.0 + 5.0 6.0 --+ 5.0 Relative lipid levels (% of total lipids) Ceramides 52.6 -+ 11.9 56.8 -+ 12.0 45.4 -+ 15.1 58.6 -+ 11.8' Fatty acids 42.4 + 11.9 38.6 -+ 12.6 45.5 -+ 21.6 35.9 +- 14.4 Cholesterol 5.1 -+ 2.5 4.7 -+ 3.1 9.0 + 7.0 5.6 + 3.4 Skin xerosis grade Grade 3 Grade 4 Lipid species Outer SC Inner SC Outer SC Inner SC Lipid levels (ng lipid/ng protein) Ceramides 49.6 + 38.1 47.6 + 22.8 41.7 --- 11.7 47.7 - 35.0 Fatty acids 92.8 - 70.4 53.6 - 38.6 84.2 - 49.8 48.5 -+ 28.8 Cholesterol 7.2 -+ 4.1 6.3 - 7.6 9.5 -+ 4.3 3.5 + 2.5 Relative lipid levels (% of total lipids) Ceramides 34.7 + 18.5 44.7 + 20.8* 35.2 -+ 14.1 45.5 + 10.6' Fatty acids 59.3 + 18.5 46.4 -+ 18.7 57.7 -+ 13.8 49.9 +- 9.4 Cholesterol 6.1 -+ 6.1 6.0 + 4.4 7.1 -+ 1.9 4.6 -+ 2.7' Values represent mean - standard deviation. Inner = tapes 2-8 Outer = tape 1. Grade 1, n = 8 grade 2, n = 8 grade 3, n = 12 grade 4, n = 12. * Significant differences between inner and outer stratum corneum (p 0.05). resulting in intact desmosomes in the surface layers, shown by electron microscopy and analysis of dsg 1 levels. The defective desmosome catabolism is probably the cause of the accumulation of corneocyte clumps on the surface of the skin to produce the scaling condition. Similar findings of desmosomal retention have been demonstrated in other skin scaling disorders, either pathological or experimentally induced (24,40-42). In- terestingly, dsgl appears to be the major adhesive desmosomal protein in the outer layers of the stratum corneum, since the other desmosomal cadherins, the desmocollins, appear to be degraded in the lower layers of the stratum corneum (43). As with the desmosomes, the stratum corneum lipid lamellae appeared to undergo a process of "degradation" or disruption at the surface layers of the cornified layer in normal skin the classical intercellular multiple-lipid bilayers present just below the surface layers appeared to disappear in the surface layers of the stratum corneum. Our findings are supported by infrared spectroscopic methods that found more fluid and