Compression therapy affects collagen type balance in hypertrophic scar

Abstract

Background: The effects of pressure on hypertrophic scar are poorly understood. Decreased extracellular matrix deposition is hypothesized to contribute to changes observed after pressure therapy. To examine this further, collagen composition was analyzed in a model of pressure therapy in hypertrophic scar.

Materials and methods: Hypertrophic scars created on red Duroc swine (n = 8) received pressure treatment (pressure device mounting and delivery at 30 mm Hg), sham treatment (device mounting and no delivery), or no treatment for 2 wk. Scars were assessed weekly and biopsied for histology, hydroxyproline quantification, and gene expression analysis. Transcription levels of collagen precursors COL1A2 and COL3A1 were quantified using reverse transcription-polymerase chain reaction. Masson trichrome was used for general collagen quantification, whereas immunofluorescence was used for collagen types I and III specific quantification.

Results: Total collagen quantification using hydroxyproline assay showed a 51.9% decrease after pressure initiation. Masson trichrome staining showed less collagen after 1 (P < 0.03) and 2 wk (P < 0.002) of pressure application compared with sham and untreated scars. Collagen 1A2 and 3A1 transcript decreased by 41.9- and 42.3-fold, respectively, compared with uninjured skin after pressure treatment, whereas a 2.3- and 1.3-fold increase was seen in untreated scars. This decrease was seen in immunofluorescence staining for collagen types I (P < 0.001) and III (P < 0.04) compared with pretreated levels. Pressure-treated scars also had lower levels of collagen I and III after pressure treatment (P < 0.05) compared with sham and untreated scars.

Conclusions: These results demonstrate the modulation of collagen after pressure therapy and further characterize its role in scar formation and therapy.

Keywords: Burn scar; Collagen; Compression therapy; Hypertrophic scar; Pressure therapy.

Figure 1

Temporal changes in collagen amounts from scar biopsies in pressure or sham treated scars using hydroxyproline quantification as a surrogate.

Figure 2

Changes in total collagen quantity assessed from biopsies obtained from pressure treated, sham treated, or untreated scars. (A) Representative photomicrographs at 40x magnification of biopsied sections stained with Masson’s trichrome at pressure initiation and at weeks 1 and 2 afterwards. (B) Image-based quantification of collagen using Masson’s trichrome stained sections. * denotes significant differences between pressure treated scars and other treatment groups (p < 0.05). ** denotes significant differences between pressure treated scars and pretreated scar (p < 0.05).

Figure 2

Changes in total collagen quantity assessed from biopsies obtained from pressure treated, sham treated, or untreated scars. (A) Representative photomicrographs at 40x magnification of biopsied sections stained with Masson’s trichrome at pressure initiation and at weeks 1 and 2 afterwards. (B) Image-based quantification of collagen using Masson’s trichrome stained sections. * denotes significant differences between pressure treated scars and other treatment groups (p < 0.05). ** denotes significant differences between pressure treated scars and pretreated scar (p < 0.05).

Figure 3

Assessment of collagen precursor transcript fold change in pressure treated and untreated scars using RT-PCR.

Figure 4

Assessment of collagen type I by immunofluorescence. (A) Representative photomicrographs at 40x magnification of biopsied sections stained for collagen type I immunofluorescence between pressure treated, sham treated, and untreated scars at pressure initiation and at weeks 1 and 2 afterwards. (B) Image-based quantification of collagen type I sections. * denotes significant differences between pressure treated scars and other treatment groups (p < 0.05). ** denotes significant differences between pressure treated scars and pretreated scar (p < 0.05).

Figure 4

Assessment of collagen type I by immunofluorescence. (A) Representative photomicrographs at 40x magnification of biopsied sections stained for collagen type I immunofluorescence between pressure treated, sham treated, and untreated scars at pressure initiation and at weeks 1 and 2 afterwards. (B) Image-based quantification of collagen type I sections. * denotes significant differences between pressure treated scars and other treatment groups (p < 0.05). ** denotes significant differences between pressure treated scars and pretreated scar (p < 0.05).

Figure 5

Assessment of collagen type III by immunofluorescence. (A) Representative photomicrographs at 40x magnification of biopsied sections stained for collagen type III immunofluorescence between pressure treated, sham treated, and untreated scars at pressure initiation and at weeks 1 and 2 afterwards. (B) Image-based quantification of collagen type III sections. * denotes significant differences between pressure treated scars and other treatment groups (p < 0.05). ** denotes significant differences between pressure treated scars and pretreated scar (p < 0.05). At week 3, differences are noted only between pressure treated and untreated scars.

Figure 5

Assessment of collagen type III by immunofluorescence. (A) Representative photomicrographs at 40x magnification of biopsied sections stained for collagen type III immunofluorescence between pressure treated, sham treated, and untreated scars at pressure initiation and at weeks 1 and 2 afterwards. (B) Image-based quantification of collagen type III sections. * denotes significant differences between pressure treated scars and other treatment groups (p < 0.05). ** denotes significant differences between pressure treated scars and pretreated scar (p < 0.05). At week 3, differences are noted only between pressure treated and untreated scars.