Micrografts. II: Evaluation of 25:1, 50:1, and 100:1 expansion skin grafts in the porcine model

Regional variations in the histology of porcine skin

Porcine skin is commonly used as a model for human skin injury and as a source material for biologic scaffold materials. Although remarkable similarities between porcine and human skin exist, regional anatomic variations present in human skin are also present in porcine skin. The objective of this study was to evaluate the structure of porcine skin from 11 different anatomic regions in the American Yorkshire crossbreed. Both qualitative and quantitative methods were used, with emphasis on epidermal and dermal thickness, hair follicle density, and collagen and elastin composition and distribution. The results showed that significant regional differences in skin histology exist, particularly with regard to the thickness of the dermis and epidermis and the amount of collagen and elastin within each tissue. Differences were also seen in the distribution of type I and type III collagen within the dermis. Therefore, while porcine skin shares many similarities with human skin, distinct regional differences in composition and morphology exist. This study highlights the importance of appreciating these regional differences to avoid misinterpretation of experimental results when using porcine skin as a human analogue.

The micrograft concept for wound healing: strategies and applications

The standard of care for wound coverage is to use an autologous skin graft. However, large or chronic wounds become an exceptionally challenging problem especially when donor sites are limited. It is important that the clinician be aware of various treatment modalities for wound care and incorporate those methods appropriately in the proper clinical context. This report reviews an alternative to traditional meshed skin grafting for wound coverage: micrografting. The physiological concept of micrografting, along with historical context, and the evolution of the technique are discussed, as well as studies needed for micrograft characterization and future applications of the technique.

Polyvinyl pyrrolidone-iodine liposome hydrogel improves epithelialization by combining moisture and antisepis. A new concept in wound therapy

Moist treatment of wounds has been shown to improve epithelialization, however at an increased risk of bacterial infection. In this monocentric, randomized, open, phase II pilot study of polyvinyl pyrrolidone-iodine, a well-established topical antiseptic was tested in a new liposomal complexed form in patients receiving meshed skin grafts after burns or reconstructive procedures. Mesh skin graft sites of 36 patients were dressed either with the new polyvinyl-pyrrolidone-iodine liposome hydrogel formulation (Betasom hydrogel) (n = 21), or chlorhexidine-gauze (n = 15). After the first dressing change, wounds were assessed daily and documented every other day until they were healed. Methods of analysis included clinical assessment, photoplanimetry (rate of epithelialization), impedance measurement (moisture of surface and wound healing quality), patient's assessment of pain and other sensations, and thyroid hormones (T3, T4, and TSH). The rate of epithelialization was improved with Betasom hydrogel compared to chlorhexidine-gauze on day 11 (96.3% vs. 75.9% p = 0.056) and significantly on day 13 (100% vs. 82.3% p = 0.005), respectively. Impedance measurements showed an earlier return to normal values (day 9) in Betasom-hydrogel-treated wounds as opposed to chlorhexidine treatment (day 11). Clinical assessment indicated significantly better antiseptic efficacy (p = 0.002) and wound healing quality (p = 0.004) of Betasom hydrogel. Graft loss occurred at a significantly lower rate in Betasom treatment (n = 1; 5%), than in chlorhexidine treatment (n = 5; 35.7%) (p = 0.001). No relevant adverse events or clinically relevant changes of thyroid hormones were observed with Betasom hydrogel. The rationale of this new polyvinyl pyrrolidone-iodine liposomal formulation was based on the properties of liposomes that provide higher moisture to the wound surface, release PVP-iodine at a low rate, and target the substance more exactly by interaction with the cell surface. These initial clinical results show earlier epithelialization and better healing in wounds treated with polyvinyl pyrrolidone-iodine liposome hydrogel, which combines moisture and antisepsis, compared to wounds treated with a conventional antiseptic chlorhexidine-gauze.