The aetiology of scars

Effectiveness of topical administration of platelet-rich plasma on the healing of methicillin-resistant Staphylococcus aureus-infected full-thickness wound model

This study aimed to investigate the wound-healing activity of animal platelet-rich plasma (PRP) in wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) in rats. After wound induction, the rats were divided into three groups: noninfected animals treated with PRP (PRP group), MRSA-infected animals treated with mupirocin (standard control group), and MRSA-infected animals treated with PRP (MRSA+PRP group). Scratch assays, MTT test, and live/dead cells were also investigated. Total bacterial count, parameters of wound area, histopathological assessment, and expressions of IL-1β, TNF-α, iNOS, PDGF, FGF-2, and TGF-β mRNA levels and immunofluorescent staining of CD31 and collagen type 1 were assessed. The results showed that culture with PRP increased migration. PRP only showed cytotoxicity in a concentration of 100%. Topical application of PRP (50 µL) reduced the wound area and total bacterial count compared with the control group (P<0.05). The mRNA levels of IL-1β, TNF-α, and iNOS expression on days 7 and 14 (P<0.05) decreased in the treated groups compared with control rats. The mRNA levels of PDGF and TGF-β expression (P<0.05) increased in the treatment groups compared with control rats on days 3 and 7 (P<0.05). FGF-2 expression was significantly higher in the treated groups compared with the control group on days 7 and 14 (P<0.05). Moreover, positive expressions of macrophage colony-stimulating factor (M-CSF), CD31, collagen type 1 and cytokeratin proteins keratinocyte proliferation, and re-epithelization were significantly (P<0.05) increased in both PRP and MRSA+PRP-treated groups compared with the control groups on days 7 and 14. Topical administration of PRP accelerated the wound healing in MRSA-infected wound by decreasing the inflammation and improving the proliferative phase.

Transition from inflammation to proliferation: a critical step during wound healing

The ability to rapidly restore the integrity of a broken skin barrier is critical and is the ultimate goal of therapies for hard-to-heal-ulcers. Unfortunately effective treatments to enhance healing and reduce scarring are still lacking. A deeper understanding of the physiology of normal repair and of the pathology of delayed healing is a prerequisite for the development of more effective therapeutic interventions. Transition from the inflammatory to the proliferative phase is a key step during healing and accumulating evidence associates a compromised transition with wound healing disorders. Thus, targeting factors that impact this phase transition may offer a rationale for therapeutic development. This review summarizes mechanisms regulating the inflammation-proliferation transition at cellular and molecular levels. We propose that identification of such mechanisms will reveal promising targets for development of more effective therapies.

Retrospective Study of the Association Between Hypertrophic Burn Scarring and Bacterial Colonization

Although the association between hypertrophic burn scarring and infection is well described, an association with colonization has not been established. This retrospective study sought to determine whether a significant association between hypertrophic scarring and bacterial colonization exists. Details from the case notes of all patients seen in our institution's burns unit over a two-year period were recorded and the incidence of hypertrophic scarring and burn bacterial colonization was noted. A total of 127 scars were recorded, and of these, 51 were hypertrophic and 76 nonhypertrophic. The incidence of bacterial colonization in the hypertrophic scar group was 88%, an association that achieved significance (P < .05) in comparison with nonhypertrophic scars (27%). This association holds true for individual organisms such as Staphylococcus aureus and Escherichia coli and for all burn depths and healing times. This study suggests that burn wound bacterial colonization may be more important than previously believed and perhaps suggests that striving toward an aseptic burn wound environment may reduce the incidence of hypertrophic scarring.

A Randomized, Placebo-Controlled, Double-Blind, Prospective Clinical Trial of Silicone Gel in Prevention of Hypertrophic Scar Development in Median Sternotomy Wound

BACKGROUND

Hypertrophic scarring caused by sternotomy is prevalent among Asians. The effectiveness of silicone gel in scar prevention may influence the decision of surgeons and patients regarding its routine use during the postoperative period.

METHODS

The authors conducted a randomized, placebo-controlled, double-blind, prospective clinical trial. The susceptibility to scar development varied among patients; therefore, sternal wounds were divided into the upper half and the lower half. Two types of coded gel prepared by an independent pharmacist were used on either half. Thus, selection and assessment biases and confounders were eliminated.

RESULTS

One hundred wounds in 50 patients were randomized into two arms, 50 control and 50 silicone gels. The median age was 61 years and there were 34 men and 16 women. Ethnic distribution was 28 Malays, 18 Chinese, and four Indians. No side effect caused by the silicone gel was noted. Ninety-eight percent of patients had moderate to good compliance. The incidence of sternotomy scar was 94 percent. At the third month postoperatively, the silicone gel wounds were scored lower when compared with the control wounds. The differences were statistically significant in all parameters, including pigmentation (p = 0.02), vascularity (p = 0.001), pliability (p = 0.001), height (p = 0.001), pain (p = 0.001), and itchiness (p = 0.02).

CONCLUSIONS

The effect of silicone gel in prevention of hypertrophic scar development in sternotomy wounds is promising. There are no side effects and patients' compliance is satisfactory. This study may popularize the use of silicone gel in all types of surgery to minimize the formation of hypertrophic scars in the early postoperative period.

Bacteria and wound healing

PURPOSE OF REVIEW

Wound healing is a complex process with many potential factors that can delay healing. There is increasing interest in the effects of bacteria on the processes of wound healing. All chronic wounds are colonized by bacteria, with low levels of bacteria being beneficial to the wound healing process. Wound infection is detrimental to wound healing, but the diagnosis and management of wound infection is controversial, and varies between clinicians.

RECENT FINDINGS

There is increasing recognition of the concept of critical colonization or local infection, when wound healing may be delayed in the absence of the typical clinical features of infection. The progression from wound colonization to infection depends not only on the bacterial count or the species present, but also on the host immune response, the number of different species present, the virulence of the organisms and synergistic interactions between the different species. There is increasing evidence that bacteria within chronic wounds live within biofilm communities, in which the bacteria are protected from host defences and develop resistance to antibiotic treatment.

SUMMARY

An appreciation of the factors affecting the progression from colonization to infection can help clinicians with the interpretation of clinical findings and microbiological investigations in patients with chronic wounds. An understanding of the physiology and interactions within multi-species biofilms may aid the development of more effective methods of treating infected and poorly healing wounds. The emergence of consensus guidelines has helped to optimize clinical management.

The efficacy of 5% Sulfamylon solution for the treatment of contaminated explanted human meshed skin grafts

Large TBSA burns have a deficiency of skin graft donor sites necessitating meshed skin autografts, cultured epithelial autografts or biosynthetic skin substitutes. Because these do not effect immediate complete biological closure of the wound, the burn victim remains at risk for life-threatening infection. Topical antimicrobials can protect colonization of these grafts from becoming invasive sepsis. However, many of these agents are cytotoxic to new partially keratinized epithelial cells. This study using a model of epithelialization kinetics of human meshed skin grafts explanted to athymic 'nude' rats evaluated: (1) the effect of bacterial colonization on the rate of closure of meshed graft interstices; (2) the efficacy of 5% Sulfamylon solution for bacterial control and (3) the effect on interstitial closure rates caused by control of bacterial proliferation. Results showed the rate of interstitial closure was progressive over 7 days in noncontaminated grafts treated with moistened saline dressings. Areas of total closure of a 1:1.5 meshed graft were seen as early as 5 days. When grafts were inoculated with 10(2) or 10(3) Pseudomonas aeruginosa organisms and treated with saline moistened dressings, the resultant bacterial load rose to 10(6) organisms, less than 3% of the interstices closed and grafts were destroyed. With the same organism level of contamination, bacterial levels were eradicated with topical 5% Sulfamylon solution, interstitial closure rates returned to normal and areas of total meshed graft closure were seen by day 4. These data demonstrate the efficacy of 5% Sulfamylon solution on epithelialization kinetics of contaminated meshed skin grafts.

The use of silicone occlusive sheeting (Sil-K) and silicone occlusive gel (Epiderm) in the prevention of hypertrophic scar formation

The development of hypertrophic scars and keloids is an unsolved problem in the process of wound healing. For this reason, a successful treatment to prevent excessive scar formation still has not been found. Over the last decade, however, a promising new treatment has been introduced. Silicone materials have proved to reduce the amount of scar tissue and are believed even to prevent hypertrophic scar and keloid formation. In this study, the prophylactic effect of a silicone occlusive sheeting (Sil-K, Degania, Israel) and a silicone occlusive gel (Epiderm, Inamed B.V., The Netherlands) was investigated in a bilateral breast-reduction scar model in which the nontreated scars were supported by nonocclusive Micropore (3M, The Netherlands). The inframammary scars of 129 female patients with a mean age of 31 years ( 14 to 69 years) were studied up to 1 year after the operation. The width and height were measured, and B-scan ultrasound, laser-Doppler flowmetry, and color measurements were used as objective indicators to distinguish between normal and exuberant scars. Three months following the operation, 64.3 percent of the patients developed a hypertrophic scar, which was reduced to 56.6 percent after 6 months and down to 35.3 percent after 1 year. No keloids were seen. Patients with an easily tanning skin, nonsmokers, and patients with an allergy showed more hypertrophic scar formation. Neither Sil-K, used in 68 patients, nor Epiderm, used in 61 patients, could prevent the formation of hypertrophic scars. If both groups were taken together, the scars treated with silicone materials even developed significantly more hypertrophy compared with the Micropore-applicated scars.

Immunological aspects of urethral stenosis. Involvement of the S100 protein-positive dendritic cells

— Within the superficial layers of healthy skin and of some mucosae there is a Population of accessory cells of the immune system, able to interact with T helper lymphocytes. Such cells, called tissular dendritic cells (DCs), increase their density and display different morphological features in a variety of immunologically-mediated dermatological disorders. In the present work we investigated DCs within the various urethral segments, both in normal conditions and in urethral stenosis. The specimens, obtained from urethrectomies and urethroplasties with end-to-end anastomosis, were stained with anti-S100 protein antibody and immunofluorescence techniques. We demonstrated an increasing density of S100 protein-positive epithelial DCs from the Prostatic urethra to the glandular one, where DCs were also larger and richer in dendritic Processes. In urethral stenosis the intraepithelial infiltrate of ramified DCs was much denser than any other control. We therefore hypothesize a role for the immune system in the development and maintenance of urethral stenoses, where, as already demonstrated for other types of pathological scarring, morphological changes of DCs serve as clues to their functional activation.

Hypertrophic scar formation after skin injury

An examination of the current treatments available to reduce skin scarring after surgery, burns or trauma.

Factors influencing the performance of temporary skin substitutes

Advances in our knowledge of the wound healing process has led to the development of various synthetic skin substitutes, which when applied to the wound surface provide a microclimate conducive to healing. The requirements of an ideal temporary skin substitute are presented. This review also provides an updated account of the preclinical evaluation procedures utilized to assess these demands, particularly important parameters such as water vapour permeability, adherence to excised wound surface, oxygen permeability, mechanical properties, microbial permeability and exudate soaking capacity.

Preclinical evaluation of skin substitutes

The important requirements of a skin substitute such as water vapour permeability, adherence to the excised wound surface, oxygen permeability, mechanical properties, impermeability to micro-organisms and exudate soaking capacity have been highlighted. Two commercial synthetic skin substitutes, Bioclusive and Geliperm, have been used to establish the preclinical assessment procedures for skin substitutes. Two in vitro techniques, the 'Water Cup' and the 'Inverted Cup,' and two in vivo methods involving a 'Ventilated Hygrometer Chamber' system and an Evaporimeter have been employed to assess and compare the water vapour permeability of the skin substitutes under controlled conditions. An Evaporimeter, which is very simple to operate, provides more accurate results. A simple test has been designed to evaluate the early adherence of the skin substitutes to the excised wound surface of rats. The pulling force and the peeling force required to remove the membrane from the wound surface have been measured and these forces have been found to depend upon the composition of the membrane. An oxygen permeability cell has been fabricated which measures the dissolved oxygen permeability of the skin substitutes. The detection of oxygen is based on the electrocatalytic reduction of oxygen at the surface of a noble metal. The tensile properties of the skin substitutes have been measured by an International Standard procedure and both the skin prostheses are associated with some drawbacks. An in vitro method of testing the microbial permeability of the skin substitutes has been designed which simulates an oozing colonized wound that a skin substitute faces in cases of septicaemia. Both the test materials were impermeable to both bacteria and fungi and will provide an effective barrier. The effectiveness of the skin substitutes to absorb wound exudate from the wound surface has been evaluated by soaking the pieces of the membranes in water, plasma and serum and observing their weight gain. The soaking capacity depends upon the composition and nature of the material. The procedures developed have been employed to evaluate a hydrogel type synthetic skin substitute recently formulated in our laboratory.