Pig Scarring and Reduction
- Duration of study – 70 days
- Lead time – 30 days
- Standard results – Visual observations, photography, histology
The Red Duroc (porcine) scarring model was originally developed as a model of hypertrophic scarring in humans. While the scarring in this model is readily apparent and does show signs of hypergranulation, BRIDGE PTS no longer promotes as a model of true hypertrophic scarring, but rather as a model of traditional scarring. For this latter purpose, the model is highly effective and reproducible.
A series of 20, full thickness excisional square wounds are placed on the backs of each pig. Treatment can initiate at any time, but is typically done on Day 0 (the day of wounding) or around Day 14 (the day when 80%+ of the wounds are completely re-epithelialized). The study runs for 70 days with visual assessments taken every 2 weeks. At the termination of the study, scar biopsies are taken and evaluated histologically to better understand the degree of subcutaneous healing and scar formation/reduction.
How the Model Works:
Visual-Analog Scores (VAS)
Scars are scored using a variety of clinical (visual) parameters. One such parameter is the visual analog scale. The table below shows example data from a study looking at high and low dose drug compared to a vehicle control. Silicone sheets (a medical device approved for scar reduction in humans) serve as the positive control in this model. The VAS is a 10-point scale. Due to the failure of this drug (scores were worse than or equal to vehicle), this study was terminated at Day 56 and therefore no Day 70 data exists.
|Low Dose||High Dose||Vehicle||Silicone Sheet|
The photograph below shows a series of control wound scars at day 70. Note the star-shaped pattern of the scars which started out as square excisional wounds. This healing/scarring pattern is characteristic of this model and demonstrates the extreme wound contraction that occurs during healing.
This model and the rabbit ear scarring model are the only two models for scar reduction accepted by the FDA for scar reduction products. Compared to the rabbit ear model pioneered by Dr. Mustoe, we find the Duroc model to be much more reproducible and less operator-dependent. Furthermore, the Duroc scarring model offers the ability to look at collagen maturation and other histologic parameters that are not available in the rabbit ear model due to the structure of the tissues underlying the ear epithelium (cartilage, not collagen).
The primary disadvantage to the model is its long cycle time (typically 70 days), making it a relatively low-throughput model and one best-saved for studies further along in their development cycle.
Advantages and Disadvantages of This Model:
- Gallant-Behm CL, Olson ME, Hart DA. Cytokine and growth factor mRNA expression patterns associated with the hypercontracted, hyperpigmented healing phenotype of red duroc pigs: a model of abnormal human scar development? J Cutan Med Surg. 2005 Aug;9(4):165-77.
- Gallant-Behm CL, Hart DA. Genetic analysis of skin wound healing and scarring in a porcine model. Wound Repair Regen. 2006 Jan-Feb;14(1):46-54.