Preclinical Psoriasis Studies

Psoriasis is a common, benign, chronic inflammatory skin disorder. It is characterized clinically by indurate, silvery scales on bright red well-demarcated plaques usually on the knees, elbows and scalp. Currently there is no cure for psoriasis but there is significant research activity. Perry Scientific offers the following mouse tail model that can be used as a screening assay for new compounds with anti psoriasis activity.

Perry Scientific Mouse Tail Model

This is accepted as a screening method for measuring anti-psoriatic activity of drugs. The basis of this method is that topical treatment of a mouse tail with anti-psoriatic drugs enhances orthokeratotic cell differentiation in the epidermal scales. This characteristic is used in our new evaluation system allowing direct measurement of drug efficacy in an animal model.

Drugs are applied topically, once daily, 5 times a week, for 2 weeks. Two hours after the last treatment the animals are sacrificed; longitudinal sections of the tail skin are made and prepared for histological examination (hematoxylin-eosin staining). (Note that this model can also be used to evaluate the activity of drugs given orally or intravenously).

As an indicator of orthokeratosis, the number of scale regions with a continuous granular layer is counted and expressed as a percentage of the total number of scale regions per section. Drug activity is defined by the increase in percentage of orthokeratotic regions.

Examples of the histology of this model are shown below.

Figure 1. Click on image for larger view.

Figure 1 shows an untreated control which reveals 12% orthokeratotic regions.

Figure 2. Click on image for larger view.

Figure 2 shows treatment with dithranol, a known anti psoriasis agent, and reveals 22% orthokeratotic regions.

Figure 3. Click on image for larger view.

Figure 3 shows treatment with Retin A, a commercially available ointment with anti psoriasis activity. This agent reveals 72% orthokeratotic regions.

Other studies using this model showed dithranol and retinoic acid dose dependently increased orthokeratosis up to 75 and 79%, respectively. Beech tar, in a concentration of 5%, induced a 19% increase in orthokeratosis. These were compared to untreated (11+/-6%) and methyl cellulose hydrogel-treated (13+/-6%) controls.

We conclude that morphometric quantification of the conversion of parakeratotic into orthokeratotic regions in mouse tail scales induced by topical drug treatment is a suitable and reliable procedure to investigate new drugs from which anti-psoriatic activity may be expected.

Histopathological Staining of Lesions

Perry Scientific offers the following histopathological stains for characterizing psoriasis:

• Epidermal thickness
• Epidermal differentiation markers
• CD3 stain for T-lymphocytes
• CD4 stain for total lymphocytes
• Leder stain for neutrophils
• KI67 for proliferating cells
• CD20 stain for in B-lymphocytes
• CD68 stain for macrophage

Pricing and Service Commitment

Perry Scientific is committed to providing on-time delivery and quality service that exceeds expectations.

Perry Scientific’s pricing is customized to meet client quality needs and budgetary constraints.