Genistein aglycone, a soy-derived isoflavone, improves skin changes induced by ovariectomy in rats

Abstract

Background and purpose: Ovariectomy accelerates age-related skin changes as adequate oestrogen levels are required to control structural integrity and functional capacity of skin. Genistein, a soy-derived isoflavone, has been tested in anti-ageing cosmetic preparations with interesting results on skin elasticity, photoaging and skin cancer prevention. We investigated the effects of genistein aglycone and compared them with systemic raloxifene hydrochloride and 17-α-ethinyloestradiol on skin changes in aged, ovariectomized (OVX) rats.

Experimental approach: Six months after ovariectomy, rats were randomly allocated to different groups and treated, daily, with genistein aglycone (1 and 10mg·kg(-1) s.c.), raloxifene hydrochloride (0.05 and 0.5mg·kg(-1) s.c.) or 17-α-ethinyloestradiol (0.003 and 0.03mg·kg(-1) s.c.) for 12 weeks. Controls were untreated OVX and sham OVX rats. At the end of the treatment period, a skin biopsy was carried out and skin samples were assessed for molecular, histological and functional changes.

Key results: Skin samples of untreated OVX rats showed a decrease in TGF-β1, VEGF, MMP-2, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 compared with sham OVX rats. All the treatments significantly restored this depressed molecular profile revealed in OVX rats. Genistein aglycone, 1mg·kg(-1) , also significantly increased the thickness of collagen and breaking strength of skin in the OVX rats.

Conclusions and implications: Relatively long-term, systemic treatment with genistein aglycone shows comparable efficacy to oestrogen in reversing some molecular, histological and functional changes of the skin associated with ovariectomy in aged rats. This suggests that genistein aglycone might be an effective alternative therapy for the management of age-related skin changes in postmenopausal women.

Figure 1

Representative flow chart of experimental model.

Figure 2

Light microscopy of Masson's tricrome staining in skin biopsies from sham OVX (A), untreated OVX (B), OVX + 17-α-ethinyloestradiol 0.003 mg·kg⁻¹ s.c. (C), OVX + genistein 1 mg·kg⁻¹ s.c. (D) and raloxifene hydrochloride 0.05 mg·kg⁻¹ s.c. (E). Original magnification ×5. (F) Histogram represents the thickness (mm) of the collagen layer; ^§P < 0.001 vs. sham OVX; *P < 0.001 vs. untreated OVX.

Figure 3

Representative Western blot analysis of both TGF-β1 (A) and VEGF (B) in skin biopsies from ovariectomized rats (OVX) treated, daily, with 17-α-ethinyloestradiol (E; 0.003 mg·kg⁻¹ s.c.); genistein (G; 1 mg·kg⁻¹ s.c.); raloxifene hydrochloride (R; 0.05 mg·kg⁻¹ s.c.). The upper panel shows a representative autoradiography highlighting TGF-β1 and β-actin (control) expression. The columns show quantitative data and represent the mean ± SD of six animals. ^§P < 0.001 vs. sham OVX; *P < 0.001 vs. untreated OVX; °P < 0.01 vs. untreated OVX; ˆP < 0.05 vs. untreated OVX; #P < 0.05 vs. OVX + raloxifene.

Figure 4

Representative Western blot analysis of MMP-2 (A), MMP-9 (B), TIMP-1 (C) and TIMP-2 (D) in skin biopsies from OVX rats treated, daily, with 17-α-ethinyloestradiol (E; 0.003 mg·kg⁻¹ s.c.); genistein (G; 1 mg·kg⁻¹ s.c.); raloxifene hydrochloride (R; 0.05 mg·kg⁻¹ s.c.). The upper panel shows a representative autoradiography highlighting MMPs, TIMPs and β-actin (control) expression. The columns show quantitative data and represent the mean ± SD of six animals. ^§P < 0.001 vs. sham OVX; *P < 0.001 vs. untreated OVX.

Figure 5

Light microscopy of MMP-2 immunostaining in skin biopsies from sham OVX (A), untreated OVX (B), OVX + 17-α-ethinyloestradiol at 0.003 mg·kg⁻¹ s.c. (C), OVX + genistein at 1 mg·kg⁻¹ s.c. (D) and raloxifene hydrochloride at 0.05 mg·kg⁻¹ s.c. (E). Original magnification ×5. Arrows point to positively stained cells in dermal layer.

Figure 6

Light microscopy of MMP-9 immunostaining in skin biopsies from sham OVX (A), untreated OVX (B), OVX + 17-α-ethinyloestradiol 0.003 mg·kg⁻¹ s.c. (C), OVX + genistein 1 mg·kg⁻¹ s.c. (D) and raloxifene hydrochloride 0.05 mg·kg⁻¹ s.c. (E). Original magnification ×5. Arrows point to positively stained cells in epidermal layer.

Figure 7

Breaking strength of skin biopsies from ovariectomized rats (OVX) treated, daily, with 17-α-ethinyloestradiol (E; 0.003 mg·kg⁻¹ s.c.); genistein (G; 1 mg·kg⁻¹ s.c.); raloxifene hydrochloride (R; 0.05 mg·kg⁻¹ s.c.). The columns show quantitative data and represent the mean ± SD of six animals. ^§P < 0.001 vs. sham OVX; *P < 0.001 vs. untreated OVX; °P < 0.001 vs. OVX + raloxifene; °P < 0.001 vs. OVX + oestradiol.