Effect of P144® (Anti-TGF-β) in an "In Vivo" Human Hypertrophic Scar Model in Nude Mice

Abstract

Background: Hypertrophic scars are one of the most important complications in surgery due to their cosmetic and functional impairments. Previous studies in tissue fibrotic disorders have shown promising results by inhibiting the biological activity effect of Transforming Growth Factor-beta 1 (TGF-β1). The aim of the current study was to determine the clinical effect of the inhibition of TGF-β1 signaling in human hypertrophic scars implanted in nude mice by topical application of an inhibitor of TGF-β1 (P144®).

Material and methods: A total of 30 human hypertrophic scars were implanted in 60 nude mice. The animals were divided in two groups, group A (placebo) and group B (treatment). Group C (basal) was considered as the preimplanted scar samples and they were not implanted in the nude mice. After the shedding period, topical application of a lipogel containing placebo (group A) or P144 (group B) was daily administered during two weeks. The animals were sacrificed upon completion of the study. Total area, thickness and collagen fibers area were measure and compared across all groups. Immunohistochemistry was also performed in order to quantify collagen type I and type III and elastic fiber expressions present in the dermis.

Results: Successful shedding was achieved in 83,3% of the xenografts. The mean time for shedding was 35±5.4 days. Statistically significant differences were found in the total area, collagen fibers area and thickness between the groups. Increased elastic fibers and decreased collagen I were found in the P144-treated group compared to the basal group.

Conclusion: Topical application of an inhibitor of TGF-β1 may promote scar maturation and clinical improvement of hypertrophic scar morphology features in an "in vivo" model in nude mice after two weeks of treatment.

Fig 1. Macroscopic aspect of a hypertrophic scar in a nude mouse.

A. Characteristic stiffness of a human hypertrophic scars after 35 days. B. After sacrificing the animal, vessels can be seen coming from the surrounding tissue arrived to nourish the hypertrophic scar.

Fig 2. Box plots representing values corresponding to total area of the three groups. (cm2).

Fig 3. Box plot corresponding to collagen fibers area of the three groups (cm²).

Fig 4. Box plot corresponding to thickness of scars in three groups (cm).

Fig 5. Histological preparations of hypertrophic scars staining with Masson’s Trichrome. (20x magnification).

Fig 6. Images of hypertrophic scars staining with anti-collagen I.

A (basal), B (placebo) and C (treatment) belong to the same scar. D (basal), E (placebo) and F (treatment) are from a second scar. Fewer stained fibers can be seen in C and F when comparing with the other groups.

Fig 7. Images of hypertrophic scars staining with anti-collagen III.

A (Basal), B (placebo) and C (treatment) represent the same scar. Differences between these three groups is minimal. Images from a second scar, D (basal), E (placebo) and F (treatment).

Fig 8. Images of hypertrophic scars staining with anti-fibrillin-1.

A (basal), B (placebo) and C (treatment) belong to the same scar and D (basal), E (placebo) and F (treatment) to a second one. It is noticeable that there is almost a complete absence of elastic fibers in A and D (basal group). Rearrangement of elastic fibers system is more obvious in pictures C and F.