# A Novel Application of RNA In Situ Hybridization in the Analysis of Vitamin D Receptor Expression in Psoriatic Skin Tissue Following Etanercept Treatment

## TL;DR

This study explores how etanercept treatment affects vitamin D receptor expression in psoriatic skin using a new technique called RNAscope.

## Contribution

The study is the first to apply RNAscope for analyzing VDR expression in psoriasis.

## Key findings

- One patient showed a significant decrease in VDR expression in the perilesional dermis after treatment.
- Both patients showed a non-significant trend toward increased VDR expression in the lesional epidermis.
- The study demonstrates the feasibility of using RNAscope for VDR analysis in psoriasis.

## Abstract

Psoriasis is a chronic inflammatory skin disease marked by abnormal keratinocyte proliferation and immune dysregulation. The vitamin D receptor (VDR) plays a crucial role in regulating skin cell growth and immune responses, but its expression in psoriatic skin and modulation by treatment remain unclear. This study aimed to analyze VDR mRNA expression in psoriatic skin tissue before and after etanercept therapy using RNAscope, an RNA in situ hybridization technique that, to the best of our knowledge, has not previously been applied in psoriasis research. Two bio-naïve adult patients with moderate to severe plaque psoriasis received etanercept (50 mg weekly) for 12 weeks. Skin biopsies from lesional and perilesional areas were collected at baseline and post-treatment. VDR expression was assessed in different epidermal layers and the dermis using a semi-quantitative scoring system. In one patient, a statistically significant decrease in VDR expression was observed in the perilesional dermis after treatment (p < 0.001), though this preliminary finding warrants careful interpretation given the very limited cohort size. Both patients exhibited a non-significant trend toward increased VDR expression in the lesional epidermis post-treatment. These preliminary findings suggest that etanercept may modulate VDR expression in psoriatic skin, but individual variability and the small sample size preclude definitive conclusions. The study primarily demonstrates the feasibility of using RNAscope for VDR analysis in patients with psoriasis, an approach that may be novel in this context, and underscores the need for larger investigations to confirm these preliminary findings and further clarify the role of VDR in disease pathogenesis and treatment response.