Dermal Fibroblasts from the Red Duroc Pig Have an Inherently Fibrogenic Phenotype: An In Vitro Model of Fibroproliferative Scarring

Background: The pathophysiology of hypertrophic scarring is unknown in part because of the lack of a robust animal model. Although the red Duroc pig has emerged as a promising in vivo model, the cellular mechanisms underlying Duroc scarring are unknown, and the size and cost of Duroc pigs are obstacles to their use. Given the central role of the dermal fibroblast in scarring, the authors hypothesized that dermal fibroblasts from the Duroc pig exhibit intrinsic differences in key aspects of the fibroblast response to injury compared with those from the Yorkshire pig, a same-species control that heals normally. Methods: Duroc and Yorkshire dermal fibroblasts were isolated from uninjured dorsal skin. Actin stress fibers and focal adhesions were visualized by immunocytochemistry and transmission electron microscopy. Cell migration was measured using a scratch wound-closure assay. Contractile function was assessed by collagen gel contraction. Expression of scarring-related genes was determined by quantitative real-time reverse-transcriptase polymerase chain reaction, and transforming growth factor (TGF)-1 protein expression was determined by Western blotting. Results: Duroc dermal fibroblasts display increased adhesion-complex formation, impaired migration, enhanced collagen contraction, and profibrotic gene and protein expression profiles compared with Yorkshire fibroblasts at baseline. In addition, Duroc fibroblasts overexpressed TGF-1 and were less responsive to exogenous TGF-1. Conclusions: Duroc dermal fibroblasts have inherent myofibroblastic differentiation that may account for the pathologic scarring in these animals. The authors' data further validate the Duroc model and support Duroc fibroblast cell culture as a simple, inexpensive, reproducible, and biologically tractable in vitro model for the study of fibroproliferative scarring.