Correlation between Porcine and Human Skin Models by Optical Methods

Abstract

Background: Topical photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA) and methyl aminolevulinate (MAL) as precursors of protoporphyrin IX (PPIX) have been used in skin cancer treatment and other skin diseases. To establish new topical PDT, protocols are necessary first to conduct studies in vivo using animal skin models. The goal of this study is to evaluate the robust correlation between porcine and human skin models in vivo by optical methods to confirm the suitability of porcine skin models to predict drug behavior in the human skin on topical PDT protocols. Methods: The study was performed in vivo using porcine and human skin models. In human skin, ALA and MAL cream mixture samples were applied to the inner arm in a circular area of 1 cm 2 . In porcine skin, the cream was applied on the back in an area of 4 cm 2 , over which an occlusive dressing was placed. PPIX production was monitored for up to 5 h using widefield fluorescence imaging and fluorescence spectroscopy techniques. Results: Human skin models showed similar behavior to porcine skin models, which indicates high similarity between both models and confirms that porcine skin is an adequate model to establish new clinical PDT protocols in human volunteers.

Assessing the Dermal Penetration Efficacy of Chemical Compounds with the Ex-Vivo Porcine Ear Model

“…Porcine skin has a high similarity to human skin, and thus, is often used as a model for human skin [ 1 , 2 , 3 , 4 , 5 ]. The ex vivo porcine ear model has various applications; in most cases, it is used for the determination of the dermal penetration efficacy of chemical compounds from different formulations or to determine skin effects of the application of chemical compounds and/or topical formulations [ 2 , 6 , 7 , 8 ].…”

Thermoregulation mechanisms and perspectives for validating thermal windows in pigs with hypothermia and hyperthermia: An overview

“…A significant difference between piglets and hogs is the thickness of the skin and its supporting structures. The dermis and subcutaneous tissue of hogs measures around 3 mm, 21–26 μm ( 36 ). The thickness of the epidermis varies from one anatomical site to another, but ranges around 30–140 μm, which can be considered a barrier against cold temperatures ( 37 ).…”

“…In contrast, studies of one-day-old piglets report a skin thickness of 0.3–1.4 mm, a stratum corneum of 11–48 μm, and an epidermis of 33–68 μm ( 39 ). This influences their thermoregulatory capacity, tolerance to extreme climates, and interaction with the vascular anatomy that, in neonates, is similar to that of human skin ( 36 ).…”

“…Two other factors related to the skin are glandular structures and the presence of hair follicles. Piglets have a capillary: follicle ratio of 730/cm 2 , but reports on hogs estimate just 10.16 follicles/cm 2 ( 36 ). The importance of these structures during the first days of life lies in their heat-conserving function generated by piloerection.…”