Comprehensive analysis of zinc derivatives pro-proliferative, anti-apoptotic and antimicrobial effect on human fibroblasts and keratinocytes in a simulated, nutrient-deficient environment in-vitro

Zinc as therapeutic agent in skin and wound care has been known for centuries, but its role is controversial and comprehensive investigations in nutrient-deficient environments are lacking. We aimed to provide a broad analysis of different zinc derivatives on proliferation, apoptosis and antimicrobial properties in a simulated nutrient-deficient environment in-vitro. Human fibroblasts (CRL2522) and keratinocytes (HaCaT) were treated with a broad concentration range (10 – 0.0001 µg/mL) of zinc-sulfate (ZnSO4), -gluconate (ZnGluc) and -histidine (ZnHis) for 1-6 days under nutrient-deficient media conditions. Cell proliferation was investigated by XTT-assay. Targeted analyses in proliferation- (E2F1, PCNA) and apoptosis- (TP53) associated genes were performed via qRT-PCR and apoptosis was determined via FACS (Annexin V/7-AAD staining). Antimicrobial efficacy was investigated using a quantitative suspension method (QSM) against S. aureus, P. aeruginosa, E. coli and C. albicans. Especially 0.1 to 0.001 µg/mL Zn increased cell proliferation in both cell lines. Fibroblasts were more susceptible with significant proliferation peaks on days 2 & 6 and days 1 & 4 for keratinocytes. Unfortunately, no relevant changes in gene expression were detected for E2F1 and PCNA levels nor for TP53 expression. Annexin-V/7-AAD-staining of fibroblasts revealed a small, yet insignificant reduction of apoptosis induction for ZnGluc and ZnSO4. 0.1% ZnGluc and ZnSO4 achieved high microbial reductions (4-5 log10 reductions) against tested pathogens. ZnGluc and ZnSO4 showed relevant pro-proliferative and antimicrobial, as well as tendential anti-apoptotic features in a simulated nutrient-deficient microenvironment in-vitro. This further validates a potential benefit of local zinc treatment in deficient wound microenvironments.