Homeostasis of the epidermal barrier layer: A theory of how occlusion reduces hypertrophic scarring

Abstract

The mechanism of hypertrophic scar reduction using silicone gel sheeting remains elusive. We hypothesize that the decrease in scar formation is due to occlusion and homeostasis of the barrier layer. Using an established model of hypertrophic scarring, rabbits were divided into four groups and scars were tape-stripped or occluded with Kelocote, Cavilon, or Indermil, with each rabbit serving as its own internal control. All wounds were harvested on day 28 and examined histologically to measure the scar elevation index (SEI), epithelial thickness, and cellularity. Immunohistochemistry fluorescence was used to quantify inflammation in the dermis. Transepidermal water loss (TEWL) was measured for each occlusive agent and tape stripping. Ultrastructural analysis was performed by electron microscopy. Kelocote, Cavilon, and Indermil all significantly decreased SEI when compared with controls. Each of the occlusive treatments was shown to decrease TEWL while tape stripping increased TEWL. Tape stripping significantly increased the SEI, epithelial thickness, and cellularity. Immunostaining for macrophages showed increased density of inflammatory cells in the tape-stripped scars. Under electron microscopy, the tape-stripped wounds displayed extensive inflammation and keratinocyte damage. Both unwounded skin and occlusion-treated scars did not display these characteristics. In conclusion, hypertrophic scarring was reduced regardless of occlusive method used. Furthermore, repeated disruption of the permeability barrier by tape stripping led to an increase in scarring. Ultrastructural analysis suggests that occluded wounds may be in an advanced state of wound repair. Occlusion may mediate its effects through establishing homeostasis of the epidermal barrier layer.

Epidermal Differentiation in Barrier Maintenance and Wound Healing

“…Interestingly, in hypertrophic scars, another pathological process where normal cutaneous wound healing fails, although the epithelium regenerates, the barrier function of the stratum corneum is altered, displaying high rates of water loss. 52 …”

The Use of Silicone Adhesives for Scar Reduction

“…The epidermal thickness index can be used as a supporting indication of how well the wounded skin has regenerated. Many studies have proven the effectiveness of SGS in minimizing the SEI, returning it closer to normal skin in both hypertrophic scars 13,14,21,41,42 and keloids. 43 Another physical measure is pliability of the scar tissue, also found to be improved.…”

“…19 It is worth noting that the gentle removal of SGS compared with alternative adhesive sheeting also minimizes skin stripping of the newly formed stratum corneum, further contributing to its treatment potential. 20,21 Another physical mode of action provided by SGS is transferring tension from the lateral edges of the wound bed to the silicone gel sheet. The gentle reduction in tension which can be provided by an adhesive SGS provides the ideal environment for normal scar development and can significantly reduce the rate of abnormal and keloid scarring.…”

Wound bed preparation: A novel approach using HydroTherapy

“…HydroTac provides a continuum of hydration that aids wound healing.  Faster wound healing (Winter, 1962;Dyson et al, 1988;Beam et al, 2008)  Promote epithelialisation rate (Winter, 1962;Eaglstein, 2001;Ågren et al, 2001;Varghese et al, 1986;Rubio, 1991;Madden et al, 1989;Wigger-Alberti et al, 2009)  Promote dermal/wound bed healing responses, e.g., cell proliferation, ECM synthesis (Svensjö et al, 2000;Dyson et al, 1992;Mosti, 2013;Korting et al, 2010;Chen et al, 1992;Leung et al, 2010;Field & Kerstein, 1994;Dowsett & Ayello, 2004;Katz et al, 1991)  ReducI can't es scarring (Atiyeh et al, 2003(Atiyeh et al, ,2004O'Shaughnessy et al, 2009;Mustoe & Gurjala, 2011;Tandara et al, 2007;Hoeksema et al, 2013)  Retention of growth factors at wound site (Svensjö et al, 2000;Hackl et al, 2014;Powers et al, 2013;Chen et al, 1992;Attinger et al, 2006;Vogt et al, 1995)  Lower wound infection rates (Kannon & Garret, 1995;Hutchinson & Lawrence, 1991;Lawrence, 1994)  Reduces pain perception (Wiechula, 2003;Metzger, 2004;Leaper et al, 2012;Coutts et al, 2008;Feldman, 1991;...…”