Comparison of the effects of vitamin D products in a psoriasis plaque test and a murine psoriasis xenograft model

Abstract

The aim of the present study was to compare the effects of Daivobet and calcipotriol on clinical score and biomarker responses in a modified version of the Scholtz-Dumas psoriasis plaque assay. Furthermore, it was the aim to compare the effects of calcipotriol and betamethasone in the murine psoriasis xenograft model. Twenty four patients with psoriasis were treated topically once daily for three weeks, whereas the grafted mice were treated for four weeks. Clinical responses were scored twice weekly and biopsies were taken at the end of each study to analyse for skin biomarkers by histology and immunohistochemistry. The results clearly demonstrate effects on both clinical signs and biomarkers. In the patient study the total clinical score was reduced significantly with both Daivobet and calcipotriol. Both treatments reduced epidermal thickness, Ki-67 and cytokeratin 16 expression. T cell infiltration was significantly reduced by Daivobet but only marginally by calcipotriol. Both treatments showed strong effects on the epidermal psoriatic phenotype.Results from the xenograft model essentially showed the same results. However differences were observed when investigating subtypes of T cells.The study demonstrates the feasibility of obtaining robust biomarker data in the psoriasis plaque test that correlate well with those obtained in other clinical studies. Furthermore, the biomarker data from the plaque test correlate with biopsy data from the grafted mice.

Figure 1

Percent reduction (mean ± SEM, n = 12) in total clinical score (TCS) from day 1 to day 22 after treatment with Daivobet^® vehicle, calcipotriol and Daivobet^® once daily 6 times weekly (excl. Sunday) for three weeks.

Figure 2

Correlation between biomarker responses and total clinical score in skin samples from psoriasis patients treated for three weeks with ointment vehicle. Correlation of clinical score with epidermal thickness (A; r = 0.733), CD3 positive T cells (B; r = 0.375), Ki-67 positive cells (C; r = 0.675) or cytokeratin 16 positive cells (D; r = 0.628).

Figure 3

Biomarker endpoints after treatment with vehicle (A, D, G and J), calcipotriol (B, E, H and K) and Daivobet^® (C, F, I and L) in the psoriasis plaque assay. A-C: Masson-Trichrome (MT) staining showing epidermal hyperplasia. D-F: Proliferation of keratinocytes in stratum basale of epidermis (Ki-67). G-I: Immunohistochemical staining with a pan-T cell marker (CD3). J-L: Epidermal expression of keratin 16 show decrease after treatment with calcipotriol and is absent after treatment with Daivobet^®.

Figure 4

Immunohistochemical stainings of a keratome biopsy before (A, B and C) transplantation and after (D, E and F) transplantation and treatment in the psoriasis xenograft SCID mouse. Before transplantation the expression of CD3 (A), CD4 (B) and CD8 (C) is seen in follicular structures and diffusely distributed in the skin. However, the intensity of CD4 expression is slightly decreased compared to freshly excised and fixed psoriatic skin (data not shown). Five weeks after transplantation including a three week treatment with vehicle the expression of CD3 (D) expression in the skin seems to be increased. In contrast, CD4 (E) and CD8 (F; arrows) expression is down regulated after vehicle treatment. The skin from A, B, C, D, E and F is from the same donor.