TOPICALLY APPLIED LIPOSOME-ENCAPSULATED T4 ENDONUCLEASE V INCREASES REPAIR OF UV-INDUCED CYCLOBUTANE PYRIMIDINE DIMERS IN NORMAL REPAIR PROFICIENT RECONSTRUCTED SKIN.

This study by scientists at AGI Dermatics demonstrated that MatTek’s EpiDermFT full-thickness in vitro human skin tissue equivalent can be used as a model for DNA repair in human skin and to investigate the effects of topical application of liposome-encapsulated DNA repair enzymes. Reconstructed skin is a useful model because it uses human cells and avoids the use of animals. Scientists at AGI Dermatics used an epidermal full thickness model (MatTek EpiDermFT EFT-200) to determine the ability for DNA repair in a human skin equivalent compared to that exhibited in normal human epidermal keratinocytes. To measure the repair of cyclobutane pyrimidine dimers (CPD) in DNA, reconstructed skin inserts were exposed to UVB from a Kodacel-filtered FS40 sunlamp over a dose range of 750 J/m2 to 7,500 J/m2. DNA was extracted from either a 2-mm or 4-mm punch biopsy and then loaded onto a dot blot, which was stained with an antibody specific for thymine-thymine dimers. The blot was calibrated with samples of UV-irradiated ë-DNA for which the CPD frequency was known. Scientists found that sufficient DNA could be recovered from a 2-mm punch biopsy to permit triplicate measurements, and that a UVB dose of at least 750J/m2 was required for reproducible measurements. A dose of 3,000 J/m2 produced approximately 600 CPD per million bases. This CPD frequency declined by approximately 40% over 24 hrs, which is comparable to what is reported for normal skin. Liposomal T4 endonuclease V, in a hydrogel lotion, was applied to the reconstructed skin inserts following UVB irradiation. T4 endonuclease V cleaves DNA at the site of UV-induced CPD and initiates its removal, and the liposome delivery facilitates its entry into skin. Reconstructed skin irradiated with 3,000 J/m2 and treated with 77,500—465,000U/mL T4 endonuclease V liposome lotion exhibited repair of CPD, at 6hr, which was approximately 60% of the repair potential seen in this system. These results indicate that EpiDerm reconstructed skin tissues can be used as a model for DNA repair in human skin and to investigate the effects of topical application of liposome-encapsulated DNA repair enzymes.

Cyclobutane pyrimidine dimers (CPB), DNA repair, EFT-200, EpiDerm-FT, EpiDermFT, Hydrogel lotion, Liposome, Liposome-encapsulated DNA repair enzymes, T4 endonuclease V, TN 45 Liposome lotion, TN45 Liposomes, UVB irradiation

Liposome lotion (TN45), Liposomes (TN45)