Tumorigenicity Testing in Athymic Mice of Cultured Human Melanocytes for Transplantation in Engineered Skin Substitutes

Abstract

Autologous engineered skin substitutes (ESS) have been shown to close excised, full-thickness burns, but are consistently hypopigmented due to depletion of human melanocytes (hM) during culture of keratinocytes. Hypothetically, addition of hM to ESS may restore uniform pigmentation, but may also promote neoplasia and tumor formation. To evaluate this risk, 16 strains of hM were isolated and propagated in selective culture medium, then injected subcutaneously into athymic mice (1 χ 107 hM/animal; n = 6/strain) and followed for 24 weeks. Human melanoma cells (SK-Mel-2, SK-Mel-5) served as positive controls. No detectable tumors formed from hM strains derived from normal skin. In contrast, SK-Mel-2 formed tumors in 50% of mice, and SK-Mel-5 formed tumors in 83% of mice. Histopathology confirmed the tumorigenic anatomy of the controls and the presence of hM that were not tumorigenic in the test groups. These results support the safety of cultured hM for transplantation to restore uniform skin pigmentation in wounds closed with ESS.