[Experimental study on removal melanin granules from acellular dermal matrix of giant nevus]

To study the possibility of removal melanin granules from autogenic acellular dermal matrix of giant nevus tissue by H2O2 bleaching technique.

A total of 32 skin specimens (0.5 cm x 0.5 cm) from giant nevus tissue and 1 piece (0.5 cm x 0.5 cm) of normal skin were obtained from the surgical removal. One giant nevus tissue was chosen as control. The others and the normal skin tissue were treated with solution of 0.25% Dispase II for digestion for 24 hours under normal temperature to remove epidermis. Then each piece was immerged into solution of 0.5% Triton X-100 for digestion for 48 hours in normal temperature. One giant nevus tissue and the normal skin tissue were chosen as control. The others were immerged into solution of different concentrations of H2O2, treated under different temperature and lasting for different period. Lastly, all specimens were treated with HE staining, immunohistochemical staining, light microscopy and so on.

After giant nevus tissues were treated with solution of 0.25% Dispase II and immerged into solution of 0.5% Triton X-100 in normal temperature, nevus cells and all other cellular components of pigmented nevus tissues can be effectively removed, there were the cavities left by removal of cells without any residual cell debris, but still remaining part of pigment. Then each specimen were immerged into solution of different concentrations of H2O2, under different temperature and lasting for different period which can remove residual melanin granules. In solution of 3% H2O2 for 36 h under 37 degrees C, can remove all the melanin particles, the content of collagen type I in the obtained specimen was not changed. Collagen fibers were uniform in thickness, regular in arrangement with no obvious degeneration.

With solution of 0.25% Dispase II and solution of 0.5% Triton X-100 in normal temperature, all cells in nevus tissue can be removed effectively. Further treatment with 3% H2O2 at 37 degrees C for 36 h can remove all the melanin particles, while collagen type I has no obvious change. The preparation of acellular dermal matrix of the giant nevus may possibly be applied as autologous tissue implant to repair tissue defects.