Fig 1.
Schematic of the scar biopsy processing methodology.
At each time point, at least one 6-mm biopsy punch was collected. Scars were marked to identify tissue orientation with respect to anatomy. The biopsy was cut in half with one half snap frozen and the other half processed for histology. The biopsy was first sectioned in cross-section. Subsequently, the biopsy was sectioned en face following removal of the epidermis with coarse sectioning.
Fig 2.
Representative images of scars.
Scars were either treated continuously with pressure garment therapy (continuous pressure), or pressure garment therapy was halted at week 17 (pressure released). Control scars did not receive any treatment. Pressure garment therapy (PGT) resulted in smoother, less contracted scars; however, when pressure was removed at 17 weeks scars became visibly contracted within 4 weeks post therapy cessation. Scale bar = 2 cm.
Fig 3.
Scar area as a function of time and treatment.
Scar area was normalized to the area of each individual scar at week 0 to obtain a percent of the original area. Pressure garment therapy was stopped at week 17 in the pressure released group, indicated by the red arrow. Cessation of PGT resulted in rapid contraction of the skin with scars in the pressure released group exhibiting similar scar areas as untreated controls by week 29 post injury. N = 8 per group.
Fig 4.
Scar height with respect to the levels of the surrounding normal skin.
Negative values represent scars that were depressed with respect to the surrounding tissue and positive values indicate raised scars. Cessation of pressure garment at week 17 resulted in significant scar thickening to raise the scar close to the level of the surrounding tissue. N = 8 per group except N = 7 for Continuous Pressure at week 17.
Fig 5.
Scar roughness (Rz) as a function of time and treatment.
Groups which received PGT were significantly smoother than controls at week 17. Cessation of PGT resulting in an increase in surface roughness versus the continuous pressure group. Photographs of scar replicas at week 29 (Right) illustrating the differences in surface texture. Scars treated with continuous PGT were comprised of very fine wrinkles whereas the released and control groups had much larger scale roughness. All images at the same magnification. Scale bar = 1 cm. N = 8 per group.
Fig 6.
Scar biomechanics as measured with a torsional ballistometer.
Deeper indentations (larger values) represent softer, more pliable skin. Pressure garment therapy decreased scar hardness compared to controls. PGT cessation resulted in an increase in hardness of the scars. N = 8 per group except N = 6 Pressure Released group at week 29.
Fig 7.
Representative images from trichrome stained histological sections prior to pressure release (left) and at the final time point (right). Pressure garment therapy resulted in less dense matrix deposition, indicated by a lighter blue stain. Over time, collagen deposition increased in all groups, but the density was greater in the pressure released and control groups at week 29. Scale bar = 750 μm.
Fig 8.
Representative images of Picrosirius Red stained histological sections prior to pressure released (left) and at the final time point (right). Pressure treated groups contained thinner collagen fibers oriented parallel to the surface of the scars. Cessation of pressure resulted in the formation of thick collagen bundles oriented perpendicular to the epidermis. Scale bar = 500 μm.
Fig 9.
Histological sections of scars cut en face showing extracellular matrix organization as a function of treatment and time.
Collagen fibers in the groups receiving pressure garment therapy (PGT) were oriented in two primary directions whereas controls were oriented parallel to the circumference of the pig (the vertical axis in each image). After cessation of PGT, collagen fibers within the pressure released group became more uniformly oriented in one direction. This increase in alignment continued until the end of the experiment (Week 29).