In vivo Sponsored by
a The Bio-Rad Detergent Compatible Protein Assay Kit used for this study is manufactured by Bio-Rad Laboratories, Hercules, Calif., USA.
b The Hitachi U-2001 UV-vis Spectrophotometer used for this study is manufactured by Hitachi, Tokyo.
Table 1 summarizes the results from the Kalia, Schwindt and Pirot studies quantifying SC thickness.
Furthermore, 5-7 um of SC removal resulted in significant TEWL elevations, a depth unobtainable by the rayon tape (see Table 2).
The results obtained from three keratolytics from colorimetric protein assays, as described by Dreher et al.
Stratum corneum (SC) adhesive tape stripping has been utilized in the measurement of SC mass, barrier function, drug reservoir and percutaneous penetration of topical substances for nearly 50 years. The process involves a methodical, relatively noninvasive layer-by-layer removal of the outermost epidermal cell layers. Complete SC removal may require more than 70 tape strips.1, 2
The quantity of SC harvested diminishes with each sequential strip, possibly due to increased SC cohesiveness in deeper layers. Thus, the mass of any single strip depends upon the mass removed by the prior strip. SC removal may rely on the interaction between the adhesive stripping force and the cohesive intercellular force.3
In this article, several methods to quantify the protein collected by tape stripping are described, including traditional gravimetric methods as well as novel colorimetric and visible spectroscopic techniques. Further, one colorimetric method is described to effectively determine the keratolytic efficacy of various materials in vivo, suggesting additional roles for this method.
Biological Response to Tape Stripping
Tape stripping was first devised in the 1940s. In 1951, Pinkus demonstrated a remarkable burst of mitotic epidermal activity post-stripping and concluded that the lost horny layer is replaced by basal mitotic division.4 The degree of hyperplasia correlates with the level and duration of barrier disruption.5 Nevertheless, the mitotic rate may remain five times greater six days after stripping than at baseline.6 This keratinocyte hyperproliferation may be a response to water barrier disruption or cytokine release secondary to epidermal injury.5, 6
Adhesive stripping increases epidermal lipid synthesis, lamellar body production/secretion in the stratum granulosum, epidermal DNA synthesis, epidermal cytokine production, dermal inflammation, and the presence of TNF and IL-1α in skin.6 Conversely, the occlusion of stripped human skin via adhesive application suppresses mitotic activity; adhesive occlusion may therefore provide an artificial restoration of the lost barrier. Similar experiments in mice, however, do not support these findings.6