Histologic evaluation of chronic human wounds treated with hydrocolloid and nonhydrocolloid dressings

A tough and mechanically stable adhesive hydrogel for non-invasive wound repair

Wound healing has been a great challenge throughout human history. Improper treatment for wounds is so easy to lead to infection and a series of serious symptoms, even death. Because of the ability of absorbing fluid and keeping a moist environment, the hydrogel with 3D networks is ideal candidate for wound dressing. More important, it has good biocompatibility. However, most of the hydrogel dressings reported have weak mechanical properties and adhesion properties, which greatly limit their clinical application. Herein, a tough adhesive hydrogel with good mechanical stability for non-invasive wound repair is reported. The hydrogel is composed of polyethylene glycol dimethacrylate (PEGDA), chitosan (CS) and chitin nano-whisker (CW). PEGDA and CS form interpenetrating network hydrogel through free radical polymerization reaction under the UV light. The introduction of CW further enhances the toughness of the hydrogel. The pH-sensitive CS can form adhesion to various materials through topological adhesion. As a wound closure repair material, PEGDA/CS/CW hydrogel not only has the characteristic of effectively closing the wound, defending against invading bacteria, and keeping the wound clean, but also has good tensile and mechanical stability, which is expected to realize the closure and repair of joints and other moving parts of the wound. This adhesive hydrogel is proven a promising material for wound closure repair.

Wound Fluids: A Window Into the Wound Environment?

Wound healing of the skin is a complex biologic process involving temporal interactions between numerous types of cells, extracellular matrix molecules, and soluble factors. The process of repair can be viewed as involving 3 or 4 phases: homeostasis, inflammation, synthesis, and remodeling. These phases occur at different times and differ in their cellular, biochemical, and physiologic requirements. Disruption of one or more of these interactions can significantly interfere with the repair process. Such comorbidities as age, nutrition, immune status, and underlying disease status (eg, diabetes or venous stasis) contribute additional intricacy to the repair process. Because of this complexity, care of chronic wounds remains highly individualized, and it should not come as a surprise that treatment of these wounds as a group with single target therapies have met with only modest success. A major hurdle in the progression toward improved treatment regimens has been the lack of objective biochemical and physiological landmarks that can be used to assess wound status. Collection and biochemical characterization of wound fluids presents the opportunity to noninvasively obtain information reflecting the status of the wound and of specific biomarkers. This review discusses the collection of wound fluid and highlights biomarkers that may be useful to this end.

The debridement of hard to heal leg ulcers by means of a new device based on Fluidjet technology

Debridement plays an essential role in the wound-bed preparation of necrotic and sloughy ulcers, being a mandatory step to achieve a well-debrided bed, proceeding towards healing. This study reports our experience with Versajet [Versajet Hydrosurgery System (Smith & Nephew, Hull, UK)], a new device for the debridement of exudating ulcers, based on Fluidjet technology, which excises and aspirates the unwanted tissue by using the Venturi effect. In a 10-month time period, a total of 68 patients, out of a setting of 167 patients, hospitalised as affected by chronic, hard-to-heal leg ulcers, stuck in the inflammatory phase, were treated with Versajet. Based on ulcer characteristics and clinical conditions, the remaining 99 patients underwent traditional debridement with moist dressings (controls). In the majority of Versajet-treated cases (46), an adequately debrided wound bed was achieved with one operative procedure; two and three procedures were required in 17 and 5 patients, respectively. Almost all the procedures were performed in the ward at the patient's bedside. This procedure is quick (mean time per treatment is about 5 minutes); when compared with a traditional treatment with moist dressings, Versajet considerably shortens the in-hospital stay and promotes a quicker healing process. When used by an experienced surgeon, Versajet allows a selective debridement, as it makes it possible to remove only the tissue centred in the working end and spare the healthy tissue. Debriding with Versajet is highly effective in reducing the bacterial load of the ulcer bed. The pain caused by Versajet is well tolerated, especially when set for gentle debridement. If multiple treatments are required, the combined use with moist dressings is synergistic, as the dressings soften the necrotic tissue, thus facilitating the following Versajet debridement. The results indicate that Versajet offers more precision than standard mechanical debridement and, at high settings, offers an alternative to surgical debridement.

Treatment of superficial surgical wounds after removal of seborrheic keratoses: a single-blinded randomized-controlled clinical study

BACKGROUND

For the treatment of superficial surgical wounds, there are a number of options, including topical antibiotic ointments, dressings, and specialized wound care materials, such as hydrocolloid dressings.

OBJECTIVE

To evaluate the wound-healing activity of a commercially available hydrocolloid wound dressing (Avery H2460, Avery Dennison, Turnhout, Belgium) in comparison with a control treatment (Fucidine cream with Cutiplast sterile dressing) in superficial wounds after surgical removal of seborrheic keratoses.

METHODS

In a single-blinded, randomized, controlled trial, the hydrocolloid wound dressing (Avery H2460) was compared with healing by secondary intention as a control. Sixteen patients between 18 and 80 years of age with seborrheic keratoses were enrolled. Wound healing was evaluated after 7 and 10 days and then daily until complete closure of the wound area. In 7 of 16 patients, biopsies were taken after 14 days of reepithelization.

RESULTS

The hydrocolloid wound dressing (Avery H2460) induced a significantly (p<.05) faster healing (median: 8.5 days) in comparison with the control treatment (median: 10 days). The histologic investigations showed no significant differences for the investigated parameters in both groups.

CONCLUSION

The faster healing in comparison with the control treatment supports the use of the hydrocolloid wound dressing (Avery H2460) for the treatment of superficial surgical wounds.

Anaerobic cocci populating the deep tissues of chronic wounds impair cellular wound healing responses in vitro

BACKGROUND

Anaerobic cocci are estimated to be present in the deep tissues of over 50% of chronic skin wounds. While the part they play in the chronicity of these wounds is uninvestigated, anaerobic cocci have previously been shown to be involved in other chronic inflammatory human conditions.

METHODS

In this study the anaerobic microflora of the deep tissues of 18 patients with refractory chronic venous leg ulcers (mean age 80.3 years; mean duration > 24 months) was characterized using strict anaerobic culture conditions. The effect of the anaerobic organisms isolated from these tissues on extracellular matrix (ECM) proteolysis and cellular wound healing responses was studied using in vitro models.

RESULTS

Anaerobic organisms were present in the deep tissues of 14 of 18 wounds and were principally Peptostreptococcus spp. The effects of three Peptostreptococcus spp. isolated from these wounds (P. magnus, P. vaginalis and P. asaccharolyticus) on cellular wound healing responses were compared with those of two pathogenic organisms also isolated from these wounds (Pseudomonas aeruginosa and Citrobacter diversus). While the direct ECM proteolytic activity exhibited by the Peptostreptococcus spp. was limited, they did significantly inhibit both fibroblast and keratinocyte proliferation, but only at high concentrations. However, at lower concentrations peptostreptococcal supernatants profoundly inhibited keratinocyte wound repopulation and endothelial tubule formation. The magnitude of these effects varied between strains and they were distinct from those demonstrated by Pseudomonas aeruginosa and Citrobacter diversus.

CONCLUSIONS

These studies confirm the importance of anaerobic organisms in chronic wounds and demonstrate an indirect, strain-specific mechanism by which these microorganisms may play a part in mediating the chronicity of these wounds.

The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium

The human cathelicidin anti-microbial protein, hCAP18 is a component of the innate immune system and has broad anti-microbial activity conferred by its C-terminal fragment LL-37. hCAP18 is constitutively produced in leukocytes and is induced in barrier organs upon inflammation and infection. We demonstrate here a novel role for this peptide in re-epithelialization of skin wounds. We show that high levels of hCAP18 are produced in skin in vivo upon wounding. The highest hCAP18 levels are attained at 48 h post-injury, declining to pre-injury levels upon wound closure. hCAP18 is detected in the inflammatory infiltrate and in the epithelium migrating over the wound bed. In chronic ulcers, however, hCAP18 levels are low and immunoreactivity for hCAP18/LL-37 is absent in ulcer edge epithelium. Using a noninflammatory ex vivo wound healing model, composed of organ-cultured human skin, we show that hCAP18 is strongly expressed in healing skin epithelium, and that treatment with antibodies raised and affinity purified against LL-37, inhibits re-epithelialization in a concentration-dependent manner. Immunoreactivity for the proliferation marker Ki67 is absent in the epithelium of such inhibited wounds, suggesting that LL-37 may play a part in epithelial cell proliferation. Thus, we suggest that, in addition to being an anti-microbial peptide, LL-37 also plays a part in wound closure and that its reduction in chronic wounds impairs re-epithelialization and may contribute to their failure to heal.

Human chronic wounds treated with bioengineered skin: histologic evidence of host-graft interactions

Bioengineered skin is being used to successfully treat a variety of wounds. Randomized controlled clinical trials have shown that a living bilayered skin construct (BSC), consisting of human neonatal keratinocytes and fibroblasts in a collagen matrix, was able to accelerate complete closure of both venous and diabetic ulcers. BSC was particularly effective in difficult-to-heal wounds of long duration. In patients treated with BSC, no obvious signs of gross clinical rejection were observed. Testing of these treated patients showed no BSC-specific immune response and no immune response to bovine collagen or alloantigens expressed on keratinocytes and fibroblasts. However, very little is known about the histologic changes that occur after BSC has been placed on human wounds. We report our preliminary histologic observations in this uncontrolled study of a cohort of 11 patients with 14 wounds treated with BSC in whom biopsy specimens of the grafted sites were obtained at least 2 weeks after application of the construct. The etiology of these ulcers varied from arterial or venous disease to an extensively and poorly healing burn wound. Histologically, thickening of the grafted bioengineered skin was seen in all samples where residual BSC could be identified. Mucin deposition was noted in the dermal layer of the wounds and BSC in 13 of the 14 specimens examined. Unexpectedly, and in spite of good clinical outcome, 4 of the 14 specimens exhibited a foreign body-like granulomatous response. There was no history of prior exposure to BSC in the 4 patients who had a granulomatous response. These early histologic observations suggest that stimulatory interactions develop between BSC and the wound. The consistently found deposition of mucin may point to a fetal pattern of wound repair associated with the neonatal cells in BSC.

Letters

A NEW CLASSIFICATION OF LEG ULCERS CYTOCOMPATIBILITY OF HYDROCOLLOID DRESSINGS CORRECTION.

A comparative study of three occlusive dressings in the treatment of full-thickness wounds in pigs

BACKGROUND

Little objective information is available on the influence of occlusive dressings on the healing of cutaneous full-thickness wounds.

OBJECTIVE

Our purpose was to examine the effects of three occlusive dressings-two hydrocolloid dressings (Comfeel Ulcer Dressing, Coloplast A/S, Espergaerder, Denmark [hydrocolloid dressing A] and DuoDERM; ConvaTec, Princeton, N.J. [hydrocolloid dressing B]) and one polyurethane film dressing (OpSite, Smith & Nephew, Hull, U.K. [film dressing])-on tissue reactions, degree of inflammation, wound contraction, and epithelialization in full-thickness wounds in domestic pigs.

METHODS

Standardized 20 mm full-thickness punch biopsy wounds were treated for 10 days. Healing was assessed by light microscopy and by planimetry.

RESULTS

Material from both hydrocolloid dressings was phagocytosed as indicated by the presence of foam cells in the granulation tissue. Granulomatous tissue reactions around extracellular vacuoles were found in 10 of 12 hydrocolloid dressing B-treated wounds compared with one in hydrocolloid dressing A-treated wounds and in none of the 10 film dressing-treated wounds (p < 0.0001). Inflammation was significantly (p < 0.002) more pronounced in hydrocolloid dressing B-treated wounds. The extracellular vacuoles in the hydrocolloid dressing B group contained dressing material as demonstrated by Fourier transform infrared microscopy. There was a tendency (p < 0.07) towards a delayed entry into the contraction phase with hydrocolloid dressing B, but there was no significant difference in epithelialization between the three dressings.

CONCLUSION

Wound tissue reactions to different hydrocolloid dressings vary depending on composition. The tissue reactions had no significant effect on wound contraction or epithelialization.