An octyl-2-cyanoacrylate formulation speeds healing of partial-thickness wounds.

BACKGROUND: Occlusive dressings have been known to accelerate the rate of healing. Every year new dressings are being introduced in the marketplace. OBJECTIVE: The purpose of this study was to evaluate the effect of a new octyl-2-cyanoacrylate liquid dressing as compared to two over-the-counter bandages on partial-thickness wounds. Performance parameters were epithelialization, erythema, scab formation, material adherence, hemostasis, and infection. METHOD: Eight pigs with a total of 645 partial-thickness wounds were assigned to one of the following treatments: liquid dressing, standard bandage, hydrocolloid bandage, or untreated air exposed. RESULT: The liquid bandage enhanced the rate of epithelialization and was the only treatment to provide complete hemostasis, reduced scab formation, and did not induce an irritant response (erythema) or infection. CONCLUSION: The liquid bandage is an easy to use material that stops bleeding (instantaneous hemostasis) while enhancing healing of partial-thickness wounds.

The effects of topical transforming growth factor-beta2 and anti-transforming growth factor-beta2,3 on scarring in pigs.

BACKGROUND: Transforming growth factor-b2 (TGF-b2) has been implicated in the inflammatory response and subsequent scarring during wound healing. OBJECTIVE: The experiment was designed to study the effects of a topical application of TGF-b2 and mouse monoclonal anti-TGF-b2,3 neutralizing antibody (anti TGF-b2,3) on the development of fibrosis during healing. METHODS: Sixteen full-thickness excision wounds were made in the paravertebral and thoracic area of four domestic pigs. On day 0, three wounds each were treated with: a) 5 mg of TGF-b2, b) 5 mg of 2% methylcellulose (mc), or c) 1.2 mg of anti-TGF-b2,3. As a vehicle for treatment of each wound methylcellulose 2% was used. Four wounds served as the untreated air-exposed control. Wounds were biopsied and the tissue sectioned and stained with hematoxylin and eosin on days 7, 14, and 45. Three blinded observers evaluated the wound specimens. RESULTS: Using computer-aided point count stereology on days 7, 14, and 45, we found a statistically significant increase (p <.05) in the number of nucleated cells in the TGF-b2-treated wounds as compared to the other control wounds. Wounds treated with anti-TGF-b2,3 had significantly (p <.05) fewer nucleated cells on days 7,14, and 45. Microscopically, the TGF-b2-treated wounds had a larger scar area as compared to anti-TGF-b2,3 and controls. CONCLUSION: Treating wounds with an antibody directed against TGF-b2 might be a useful clinical approach to reduce fibrosis.

The evaluation of a cadexomer iodine wound dressing on methicillin resistant Staphylococcus aureus (MRSA) in acute wounds.

BACKGROUND: Many bacteria have become resistant to commonly-used antibiotics. OBJECTIVE: The purpose of this study was to examine the effect of a cadexomer iodine wound dressing on methicillin resistant Staphylococcus aureus (MRSA). METHOD: Partial thickness wounds were made on the backs of three pigs and inoculated with a known amount of MRSA. Wounds were treated with either cadexomer iodine dressing or vehicle dressing (without iodine), or they were left untreated. Three wounds from each treatment group per animal were cultured using quantitative scrub techniques after 24, 48, or 72 hours of treatment. CONCLUSIONS: The cadexomer iodine dressing significantly reduced MRSA and total bacteria in the wounds as compared to both the no treatment control and vehicle. No significant differences were observed in the number of bacteria recovered between the no treatment control and cadexomer (vehicle) treated wounds. Cadexomer iodine may be an effective agent for preventing proliferation of MRSA in wounds.

Effect of occlusion on cell proliferation during epidermal healing.

BACKGROUND: Occlusive dressings influence epithelization of superficial wounds by some unknown mechanism(s). OBJECTIVE: The effects of occlusion on epidermal cell proliferation in two types of wounds were examined. METHODS: Partial-thickness wounds and tape-stripped skin wounds were compared. An immunohistochemical technique, employing PC10 - a monoclonal antibody against proliferating cell nuclear antigen (PCNA) - was applied to formalin-fixed, paraffin-embedded porcine tissue sections. RESULTS: The number of PC10-positive cells was low during the migratory phase, then increased to a peak of proliferation 2 to 3 days after resurfacing. An overall increased proliferative response (mean = 21%) was seen in occluded compared to control partial-thickness wounds (day 10 postoperatively); an opposite effect of occlusion on epidermal proliferation was seen in tape-stripped skin. Occlusion decreased the proliferative response (mean = 42%) compared to air-exposure. CONCLUSION: Occlusion increased epidermal cell proliferation in wounds (where the entire surface epithelium and papillary dermis was removed), whereas an opposite effect was seen in tape-stripped skin from which only the stratum corneum had been removed.

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.

Suppression of prostaglandin H synthase-2 induction in human monocytes by in vitro or in vivo administration of interleukin 4.

IL-4 is a potent modulator of monocyte function. Our previous studies demonstrated that the suppression of monocyte matrix metalloproteinase production by IL-4 is a result of its inhibition of PGE2 synthesis, which was attributed to an effect on prostaglandin synthase. Here we report on the in vitro and in vivo effects of IL-4 on monocyte prostaglandin H synthase-2 (PGHS-2) and its regulation by second messengers. Stimulation of monocytes with either LPS or Con A resulted in the induction of PGHS-2 which was significantly inhibited by IL-4. Inhibition of PGHS-2 mRNA and protein was detected at 0.05 to 0.1 ng/ml of IL-4 with substantial suppression at 10 to 20 ng/ml. If added later than 2 hr after LPS, IL-4 failed to suppress PGHS-2, indicating that IL-4 acted early in the signaling cascade. Moreover, the ability of exogenously added PGE2 or Bt2cAMP to restore PGHS-2 production in IL-4-treated monocytes further suggested early disruption of the pathway. The early event inhibited by IL-4 did not involve suppression of phospholipase activity, because LPS-induced arachidonic acid release was relatively unaffected by IL-4. Unlike PGHS-2, PGHS-1, the constitutively expressed PGHS, was not modulated by IL-4. Thus, IL-4 appears to selectively block PGHS-2 synthesis, thereby blocking subsequent steps in the pathway leading to the production of matrix metalloproteinases. In an extension of these findings, we examined peripheral blood monocytes from cancer patients undergoing IL-4 therapy. In these cells the induction of PGHS-2 expression by LPS was significantly reduced compared to that of monocytes obtained prior to IL-4 therapy. Although perhaps not relevant as an antitumor mechanism, these findings have important implications in defining the potent anti-inflammatory activities of IL-4 in vitro and in vivo.

Early debridement of second-degree burn wounds enhances the rate of epithelization--an animal model to evaluate burn wound therapies.

The purpose of this study was to examine the rate of epithelization of second-degree burn wounds with use of two debridement times (early versus late). Burn wounds were randomly assigned to one of the following treatment groups: (1) control, no debridement, (2) early debridement at 24 hours after burning, or (3) late debridement at 96 hours after burning. Wounds from each treatment group were harvested, incubated to allow separation of the dermis and epidermis, and then examined macroscopically for complete epithelization. On day 7 after burning, the percentage of burn wounds completely epithelized was as follows: nondebrided, 41%, 24-hour early debridement, 75%, and 96-hour late debridement, 22%. Burn wounds that were excised 24 hours after burning enhanced the rate of healing as compared to 96 hour and nondebrided burn wounds.

Effects of an arginine-glycine-aspartic acid peptide-containing artificial matrix on epithelial migration in vitro and experimental second-degree burn wound healing in vivo.

Cells central to dermal tissue repair such as dermal fibroblasts and keratinocytes interact with arginine-glycine-aspartic acid (RGD)-containing proteins of the extracellular matrix such as fibronectin. It has been shown that synthetic peptides containing this RGD sequence can also support cell attachment and migration in vitro. We therefore set out to test whether the use of these peptides, when formulated as a synthetic RGD-peptide matrix consisting of peptide complexed with hyaluronic acid, would have an effect on the rate of epithelial migration and healing of experimental wounds. Evaluation consisted of measuring he extent of epithelial outgrowth from human dermal explants and the epithelization of experimental second-degree burn wounds in pigs. We show here that the RGD-peptide matrix supports epithelial sheet migration from explants in a dose-dependent manner. In second-degree burn wounds in pigs, wounds treated with daily applications of the RGD-peptide matrix under occlusion resurfaced at a significantly faster rate (day 7 = 57% completely epithelized) than wounds treated with hyaluronic acid under occlusion (day 7 = 13% completely epithelized, p < 0.01), occlusion alone (day 7 = 13% completely epithelized, p < 0.01), or air exposed (day 7 = 0% completely epithelized, p < 0.001). Histologic examination showed that wounds treated with the RGD-peptide matrix also had thicker epithelial covering and greater granulation tissue deposition than occluded, air-exposed, and hyaluronate-treated wounds. These data therefore show that the use of RGD-peptide matrix induces faster explant epithelial migration and results in faster healing of experimental second-degree burns.

Conductivities of pig dermis and subcutaneous fat measured with rectangular pulse electrical current.

We examined experimentally the relationship between perpendicular and tangential electrical conductivities, sigma, and peak current density J, in pig skin dermis and subcutaneous fat specimens by using a four-electrode measuring system with rectangular pulse electrical current (RPEC). We also investigated the relationship of the conductivity, sigma, vs. pulse rate, f. The rates were selected at 8, 32, 64, and 128 pulses per second (pps), and the pulse width was fixed at 140 microseconds. These values are often used in vivo to enhance cutaneous regeneration with RPEC stimulation. It was found that the conductivities may be approximated to be [equation: see text] for the skin dermis and [equation: see text] for the subcutaneous fat in the conditions of this experiment. These findings implies that the conductivities of pig skin dermis and subcutaneous fat are anisotropic, i.e., sigma x = sigma y not equal to sigma z. It was also found that the conductivities are independent of current density and pulse rate in the current range from 20 microA/cm2 to 120 mA/cm2.

In vivo 3-D distributions of electric fields in pig skin with rectangular pulse electrical current stimulation (RPECS).

We developed stimulating and detecting electrodes. We experimentally examined three dimensional (3-D) distributions of electric fields in living pig skin under and around the stimulating electrodes with the detecting electrodes and rectangular pulsed electrical current stimulation (RPECS). We verified our previous physical assumption, E approximately I/(A sigma dz), in the skin under the electrode, where E, I, A and sigma dz respectively represent the electric field, the externally imposed peak current, the cross sectional area of the stimulating electrode and the perpendicular conductivity of the skin. Pulses were 30 mA, 140 microseconds and 128 pulses per second (pps). These parameters were previously used in our laboratory to enhance cutaneous regeneration, in vivo, with RPECS.

Are excessive granulation tissue formation and retarded wound contraction due to decreased collagenase activity in wounds in tight-skin mice?

Wound contraction is delayed in tight-skin mice but the mechanism(s) are unknown. The purpose of this study was to investigate collagenase levels and the formation of granulation tissue in experimental wounds in tight-skin mice. One full-thickness skin excision (20 x 20 mm) was made on the back of nine tight-skin and eight normal mice. Granulation tissue analyses were performed 7 days post-operatively. The collagenase activity was determined by the use of a radiolabelled telopeptide-free collagen substrate, and the amount of granulation tissue was determined gravimetrically. Wound contraction was delayed (P < 0.001) in tight-skin mice (mean 22%) compared with normal mice (mean 46%). The collagenase activity was decreased (P < 0.05) by 40%, whereas the quantity of granulation tissue was increased (P < 0.001) by 60% in the wounds of tight-skin mice. Decreased collagenase content may provide one explanation for the delayed contraction of full-thickness wounds in tight-skin mice. Furthermore, this animal would model may prove useful in the understanding of the pathogenesis, and in exploration of treatment, of excessive granulation tissue formation during wound healing.

Collagenase during burn wound healing: influence of a hydrogel dressing and pulsed electrical stimulation.

Epithelialization of second-degree burn wounds is known to be accelerated by topical treatment with hydrogel dressings and further enhanced by pulsed electrical stimulation compared with no treatment (air exposure). Tissue collagenase has been proposed to be involved during the process of epithelialization. In the present study collagenase levels were examined in partial-thickness burn wounds in the skin of four domestic pigs. Collagenase levels, assayed on postburn days 1 to 10, were substantially reduced in deblistered and air-exposed burn wounds compared with excisional partial-thickness wounds. Early application of hydrogel dressing to the burn wounds was accompanied by elevated collagenase activities and an increased inflammatory reaction in dermis. Addition of pulsed electrical stimulation increased (p < 0.001) collagenase levels twofold above those with hydrogel alone during initiation of epithelialization (postburn days 3 and 4). These results suggest that collagenase is closely linked to wound epithelialization.

Interleukin 10 suppression of monocyte prostaglandin H synthase-2. Mechanism of inhibition of prostaglandin-dependent matrix metalloproteinase production.

Monocytes/macrophages are associated with chronic inflammatory lesions, such as periodontal disease and rheumatoid arthritis, in which there is extensive connective tissue destruction. Stimulation of human monocytes results in the production of matrix metalloproteinases (MMPs) via a prostaglandin E2 (PGE2)-cAMP-dependent pathway. Modulation of many monocyte functions by interleukin 10 (IL-10) suggested that this cytokine may influence the signal transduction pathway leading to the production of MMPs by monocytes. Pre-incubation of monocytes with IL-10 for 1 h prior to stimulation with ConA resulted in significant inhibition of prostaglandin H synthase-2 (PGHS-2, the inducible form of prostaglandin synthase). In contrast, PGHS-1, the constitutive PGHS, was not affected by IL-10. Suppression of PGHS-2 mRNA and protein levels was detected at 1 ng/ml of IL-10 with maximal inhibition at 20 ng/ml. Nuclear run-on transcription assays performed on monocytes exposed to ConA or the combination of ConA and IL-10 indicated that IL-10 treatment suppressed PGHS-2 expression at the level of transcription. Attenuation of PGHS-2 by IL-10 was accompanied by decreased prostaglandin production, including PGE2. The decrease in prostaglandin production was primarily related to the effect of IL-10 on PGHS-2, since the release of arachidonic acid was unaffected by this cytokine. The inhibition of PGE2 production by IL-10 resulted in the suppression of mRNA and protein for interstitial collagenase and 92-kDa type IV collagenase/gelatinase (gelatinase B). This conclusion is supported by the ability of exogenously added PGE2 or dibutyryl cAMP to restore the production of MMPs in IL-10-treated monocytes. Additionally, PGHS-2 was also restored by PGE2 or dibutyryl cAMP, indicating that PGHS-2 is regulated through a PGE2-cAMP amplification pathway. These data add further support to the anti-inflammatory properties of IL-10.

Temporal and spatial expression of laminin, collagen types IV and I and alpha 6/beta 1 integrin receptor in the developing rat parotid gland.

We have examined the temporal expression and cellular localization of the genes and proteins for the extracellular matrix (ECM) proteins laminin (B1, B2 and A chain), collagen types alpha 1 (IV) and alpha 1 (I) and the integrin receptor complex alpha 6/beta 1, during parotid gland postnatal development. Laminin B1 and B2 isoforms and collagens alpha 1 (IV) and alpha 1 (I) mRNA steady-state levels were highest at ages 0, 7 and 14 days after birth and declined to the adult (90 days) level at 21 days and older. Laminin A chain transcripts were not detected at any age. Collagen alpha 1 (IV) and laminin were localized in the basal membrane of the developing acinar and ductal cells, while collagen alpha 1 (I) was localized in the stroma surrounding the cells. The amounts of these ECM components were high at the early stages of development and lower at later times. The pattern of expression of the alpha 6/beta 1 integrin genes during development was similar to those of laminin and collagens alpha 1 (IV) and alpha 1 (I). Accumulations of mRNA were high at 0, 7 and 14 days after birth and lower at 21 days and older. High levels of beta 1 integrin were localized in the developing acinar and ductal cell membranes at early ages (7 days); lower amounts were present in the same distribution pattern at later stages of gland development.(ABSTRACT TRUNCATED AT 250 WORDS)

Wound healing microbiology.

The relationship between wound healing and cutaneous microbiology is a complex one mediated by the type of wound, its treatment, and the defense mounted by the injured individual. Acute wounds harbor microflora similar to that of noninjured skin. "Dirty" traumatic wounds or chronic wounds with devitalized tissue offer more opportunity for microflora colonization, with the potential for bacterial adherence to the host cells and ultimate invasion into viable tissue or infection. The alterations of these wound environments can be brought on by topical treatments. Occlusive dressings with various moisture vapor transmission rates can provide a wound environment suitable for microflora proliferation. In spite of this increase in numbers of organisms, most wounds do not become infected, as shown by a survey of published trials. Infection requires the proper pathogenic microorganism, its attachment, and subsequent multiplication. To cause an infection, an organism must invade viable tissue and evade the host defense response. The many occlusive dressing types available offer an opportunity to select a wound therapy tailored for the microenvironment most suitable for healing. Wounds can be protected from exogenous microfloral contamination with dressings. Some dressing types, such as hydrocolloid dressings with no moisture vapor transmission, should not be used on chronic wounds suspected of harboring anaerobic organisms. Other typical treatments, such as antiseptics, can injure tissue and make infection more probable, providing devitalized tissue for bacterial adhesion. Povidone-iodine solution has been shown not be efficacious, whereas povidone-iodine cream effectively limits bacteria and infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the repopulation of Langerhans cells in partial-thickness wounds. Air exposed and occlusively dressed.

BACKGROUND AND DESIGN: The use of occlusive dressings on partial-thickness wounds has been shown to promote early epithelization and connective tissue regeneration. Because Langerhans cells (LC) have been implicated in epidermal homeostasis we studied the rate of repopulation of LC in air-exposed vs occlusively dressed wounds. Partial-thickness wounds on the backs of pigs were treated with occlusive dressings (Tegaderm) for 3 days or left air exposed. On days 3, 5, 7, and 11 after keratome wounding, epidermal sheets from the regenerating wounds were isolated and stained for LC using indirect immunofluorescence. The LC populations were quantified in the interfollicular regions and expressed as average number of cells per square millimeter of epidermis. RESULTS: Normal skin control had 1024 +/- 93 LC/mm2 distributed uniformly. On day 3 after wounding occlusive-dressing-treated wounds had an LC repopulation of 46% of the original value. Langerhans cells in air-exposed skin could not be evaluated until epithelization occurred at day 5. Langerhans cells in both air-exposed and occlusive-dressing-treated wounds were 46% to 51%, 65% to 71%, and 91% of normal value, respectively, on days 5, 7, and 11. CONCLUSIONS: We conclude that at least in regenerating epidermis, the degree of repair of the new epidermis apparently plays a limited role in the migration of LC, as does the earlier growth of blood vessels.

Theoretical study of rectangular pulse electrical stimulation (RPES) onskin cells (in vivo) under conforming electrodes.

Our previous in vivo experimental results have shown RPES can enhance skin wound healing by using conforming electrodes. Based on an equation of polarization transmembrane voltage [Cole, K. S. 1972], two equations were derived to describe the peak RPES intensity on skin cells in vivo: (1) U = 1.5 a J/sigma, (2) Jm = 1.5 a (J/sigma) (Cm/tau). Where U: polarization transmembrane voltage. a: radius (R) for spherical cells or semi-length (L) for long fibers parallel to the electrical field. J: external imposed pulse current density under the electrode. sigma: average conductivity of skin tissue. Jm: transmembrane displacement current density. Cm: membrane capacitance per unit area and tau: time constant. Calculations indicated that the sensory fibers (SF) would receive the strongest stimulation compared to other cells in skin since generally LSF > or = 100 R. The sensitivity of SF to the stimulation could enhance skin wound healing as well as protect normal skin cells from harmful electroporation. From these theoretical calculations. We proposed a theoretical range of the pulse current density as: U1 sigma/(1.5 L) < or = J < or = U2 sigma/(1.5 L), where U1 and U2 are the excitation threshold voltage (about 0.01 V) and polarization electroporation voltage (about 0.1 V) for a SF respectively, for RPES to enhance skin wound healing.

Collagenase in wound healing: effect of wound age and type.

Collagenase is believed to be important for cell migration and collagen remodeling during tissue repair and regeneration. We have investigated collagenase concentrations in different types of surgically inflicted wounds in pigs. Collagenase was extracted from tissue homogenates of wounds by heating to 60 degrees C for 6 min in 0.1 M CaCl2. The molecular weight of latent collagenase was about 52 kDa. Activated collagenase produced the characteristic 3/4 fragment of collagen. Collagenase was assayed by the use of radiolabeled telopeptide-free collagen. To detect maximal collagenase activity, extracts were reduced and alkylated to destroy inhibitors, then activated with aminophenylmercuric acetate. Sutured incisions showed peak collagenase content on postoperative day 1 and thereafter steadily declining concentrations. Granulation tissue from non-sutured large defect full-thickness wounds showed high collagenase content on postoperative day 5 and then a sharp decline to day 7 followed by a slowly declining curve to postoperative day 21. Partial-thickness wounds exhibited a different time course, with collagenase increasing to peak concentrations on postoperative days 3-5; however, a large proportion of the detected collagenase was due to the adherent scab. By day 7 collagenase concentrations approached the low concentrations of normal skin when epithelialization was complete and the scab rejected. In general, collagenase shows an early maximum and then declines with postoperative time, with the sharpest decline occurring when epithelialization is complete.

Reciprocal expression of c-jun, proline-rich protein and amylase genes during rat parotid salivary gland development.

We have investigated the temporal expression and cellular localization of the c-jun proto-oncogene and two major rat parotid gland secretory protein genes, PRP (proline-rich protein) and amylase, during postnatal development. c-jun mRNA steady-state levels increased at days 1, 7 and 14 after birth and decreased to basal levels at 21 days and older. PRP mRNA was first detected at 14 days and abruptly increased to adult levels at day 21. Amylase transcripts were first seen at day 7 and progressively increased to adult levels by 28 days. In situ hybridization demonstrated c-jun mRNA accumulation in the differentiating acinar cells and the ducts. The c-jun mRNA accumulation with time corresponds with the proliferative activity reported to occur in these two cellular populations. PRP transcripts were present exclusively in the well differentiated acinar cells while the accumulation of amylase mRNA corresponded to the progressive commitment of parotid cells to acinar differentiation. Our data suggest that during the postnatal development of the rat parotid gland: (a) c-jun expression associates with parotid gland proliferation and precedes the expression of PRP and amylase genes, and (b) activation of PRP and amylase genes is not concomitant and apparently occurs only in differentiating acinar cells.