Fig. 1. Histological appearance of untreated skin, 14-all trans RA-treated skin and skin treated with 14-all trans RA plus soy extract. Upper panels: (A–C) Hematoxylin and eosin-stained. The increase in epidermal thickness resulting from 14-all trans RA treatment is evident in panel B as compared to control skin (panel A). Likewise, the reduced epidermal thickness in skin exposed to 14-all trans RA plus soy (panel C) is evident. (D–F) Ki-67 staining. There are few nuclei stained in untreated skin (panel D), an increased number in the retinoid-treated skin (panel E) and fewer in the retinoid plus soy-treated skin. All sections are from organ-cultured skin after 8 days in culture. Lower panel: Epidermal thickness measurements were made after 8 days in organ culture. The value from control skin (i.e., skin incubated in the absence of 14-all trans RA and soy extract) was set at 1.0. The other values were assessed relative to the control value. Values are means and standard errors based on tissue samples from seven different individuals. Statistical significance was assessed by ANOVA followed by paired group comparisons. *indicates difference from untreated control value at the P < 0.05 level; **indicates difference from 14-all trans RA alone at the P < 0.05 level.

Fig. 2. Effects of soy extract on keratinocyte proliferation. Proliferation was assessed in KGM or KBM as described in Materials and methods. Values shown represent means and standard errors based on five separate experiments with duplicate data points in each experiment. Statistical significance was assessed by ANOVA followed by paired group comparisons. *indicates difference from untreated control value at the P < 0.05 level. Left-most bar represents zero-time value.

Fig. 3. Effects of soy extract on fibroblast proliferation and production of type I procollagen. Fibroblast proliferation was assessed in Ca²⁺- supplemented KBM as described in Materials and methods. Values shown represent means and standard errors based on four separate experiments with duplicate data points in each experiment. Type I procollagen was assessed as described in Materials and methods. Values shown represent means and standard errors based on three separate experiments with duplicate data points in each experiment. Statistical significance was assessed by ANOVA followed by paired group comparisons. *indicates difference from untreated control value at the P < 0.05 level. Left-most value in upper panel represents zero-time value.

Effects of genistein, daidzein, and glycetein on 14-all trans RA-induced epidermal hyperplasia in organ-cultured skin

Epidermal thickness measurements were made after 8 days in organ culture. The value from control skin (i.e., skin incubated in the absence of 14-all trans RA and the isoflavone alone) was set at 1.0. The other values were assessed relative to the control value. Values are means and standard errors based on tissue samples from four to six different individuals. Statistical significance was assessed by ANOVA followed by paired group comparisons.

Effects of soy isoflavones on proliferation of human epidermal keratinocytes in monolayer culture

Proliferation was assessed as described in Materials and methods. Values shown represent means and standard errors based on duplicate samples in four separate experiments for each condition. Zero-time cell counts were 4.01 ± 0.95 cells per well for experiments with KBM and 4.95 ± 1.36 cells per well for experiments in KGM. Percent inhibition was calculated using the formula: % Inhibition = 1 − (Exp − T₀) / (Ctrl − T₀) × 100%, where T₀ is the number of cells at the start and Exp and Ctrl represent the number of cells in the treated and control cultures, respectively, at the end of the experiment. Statistical significance was assessed by ANOVA followed by paired group comparisons.

Effects of genistein on proliferation of human dermal fibroblasts in monolayer culture

Proliferation was assessed as described in Materials and methods. Values shown represent means and standard errors based on duplicate samples in four separate experiments. Zero-time count was 3.21 ± 0.7 cells per well. Percent inhibition was calculated using the formula: % Inhibition = 1 − (Exp − T₀) / (Ctrl − T₀) × 100%, where T₀ is the number of cells at the start and Exp and Ctrl represent the number of cells in the treated and control cultures, respectively, at the end of the experiment.