Biphasic Presence of Fibrocytes in a Porcine Hypertrophic Scar Model

Abstract

Objective The duroc pig has been described as a promising animal model for use in the study of human wound healing and scar formation. However little is known about the presence and chronology of the fibrocyte cell population in the healing process of these animals. Methods Wounds known to form scar were created on red duroc swine (3“ × 3”) with a dermatome to a total depth of either 0.06“ or 0.09”. These wounds were allowed to heal completely and were biopsied at scheduled time points during the healing process. Biopsies were formalin-fixed and paraffin embedded for immunohistochemical analysis. Porcine-reactive antibodies to CD-45 and procollagen-1 and a human-reactive antibody to LSP-1 were used to detect the presence of fibrocytes in immunohistochemistry an immunocytochemistry. Results Initial immunohistochemical studies showed evidence of a biphasic presence of fibrocytes. Pigs with 0.06“ deep wounds showed positive staining for CD-45 and LSP-1 within highly cellular areas at days 2 and 4 after wounding. Additional animals with 0.09” deep wounds showed positive staining within similar areas at days 56, 70, and 113 after wounding. There was no immunohistochemical evidence of fibrocytes in skin biopsies taken at days 14, 28, or 42. Procollagen-1 staining was diffuse in all samples. Cultured cells stained for CD-45, LSP-1, and procollagen-1 by immunocytochemistry. Conclusions These data confirm that fibrocytes are indeed present in this porcine model. We conclude that these cells are present after initial wounding and later during scar formation and remodeling. We believe that this is evidence of a biphasic presence of fibrocytes, first as an acute response to skin wounding followed by later involvement in the remodeling process, prompted by continued inflammation in a deep partial thickness wound.

Compression therapy affects collagen type balance in hypertrophic scar

“…Duroc swine were prepared and used as previously described [28]. Animals were brought to an operating suite and anesthetized using a combination of ketamine and xylazine delivered intramuscularly.…”

“…By day 70 post-wound creation, all wounds were confirmed to have formed hypertrophic scars. At this point, an automatic pressure delivery system (APDS) for scar compression therapy [29] was mounted onto hypertrophic scars for treatment as previously described [28]. This device consisted of a polycarbonate enclosure that housed a wireless communication device (XBee 2.4 GHz RF modem, Digi International, Inc., Minnetonka, MN) and a compression plate for pressure delivery onto hypertrophic scar.…”

“…Slides were deparaffinized using xylene and rehydrated through an ethanol gradient. Staining was then performed by Masson’s trichrome or immunofluorescence using previously described protocols [28, 31]. For immunofluorescence, primary antibodies included monoclonal anti-mouse collagen type I (Abcam, Cambridge, UK) and monoclonal anti-mouse collagen type IIII (Abcam, Cambridge, UK) at a 1:500 dilution.…”

Imaging mass spectrometry for accessing molecular changes during burn wound healing

“…This study marks a preliminary foray toward the elucidation of novel biomarkers that are likely to shed light on the unwanted sequelae in human burn victims that nearly always result in hypertrophic scarring that persists for a lifetime. While porcine‐based reports based on the use of the red Duroc swine model have been used in recent years to evaluate scar formation, such studies are extremely expensive due to their long term housing costs . Smaller murine models of fibrosis have had limited utility to date and models using human skin transplanted onto immunocompromised mice have a limited ability to study the local burn wound in the context of the human systemic inflammatory response .…”

“…While circulating mediators and cells that affect patients from a global and systemic basis have been examined, global proteomic examination of local skin responses in patients after thermal injury have not been reported. Historically work with burned skin has used available techniques and tools that represent a reductionist type of approach that are focused on the role of individual or several mediators or used skin tissue from animal models …”