The effects of Platelet-rich Plasma on healing of partial thickness burns in a porcine model.

Platelet-rich plasma (PRP) derived from autologous peripheral blood is rich in platelets that release growth factors and cytokines. We determined the effects of topically applied autologous PRP in a partial thickness porcine burn model. Partial thickness burns were created on the backs and flanks of six domestic pigs (24 burns each) using an aluminium bar preheated to 80° C for 20 seconds. After removing the necrotic epidermis, the burns were randomly treated with a topical antibiotic ointment or a single (day 2), double (days 2 and 7), or triple (days 2, 7, and 14) topical application of PRP that was prepared freshly before application. Periodic imaging and full thickness biopsies were conducted to monitor healing over 28 days. The percentage wound reepithelialization at days 11, 14, 18 and 21 did not differ significantly among the groups. By day 28 all wounds were completely (>95%) reepithelialized, and there were no differences among the groups. Time to complete healing (presented as mean, [SD]) did not differ among the groups (antibiotics, 17.1 [3.5]; single PRP, 17.6 [4.0]; double PRP, 18.4 [3.9]; and triple PRP, 17.7 [3.3] days; ANOVA P=0.43). Scar depth (presented as mean, [SD]) in mm at day 28 by treatment group was: antibiotic 5.0 [1.0], single PRP 5.5 [1.1], double PRP 5.4 [1.1], and triple PRP 5.5 [0.6], ANOVA P=0.026. We conclude that PRP results in similar rates of reepithelialization and scar depth to standard topical antibiotics in a partial thickness porcine burn model.

Le plasma riche en plaquettes (PRP), dérivé du sang autologue, permet le relargage de facteurs de croissance et de cytokines. Nous avons étudié l'effet de PRP appliqué localement sur un modèle de brûlure intermédiaire chez le porc. Cette brûlure du dos et des flancs était réalisée au moyen de l'application pendant 20 s d'aluminium chauffé à 80°C sur 4 groupes de 6 porcs. Après ablation de l'escarre, les animaux étaient tirés au sort pour être traités par topique antibiotique, 1 (J2), 2 (J2 et J7) ou 3 (J2, J7, J4) application locale de PRP préparé juste avant utilisation. Des photos et des biopsies ont été réalisées régulièrement pendant 28 j afin de surveiller la cicatrisation. Les pourcentages de surface cicatrisée à J11, J14, J18 et J21 étaient similaires dans tous les groupes. La cicatrisation était quasi complète (> 95%) à J28, dans tous les groupes. Le délai jusqu'à cicatrisation complète n'était pas différent dans les groupes (ANOVA, p=0,43) : Contrôle 17,1 +/- 3,5 ; PRP J2 17,6 +/- 4 ; PRP J2 et J7 18,4 +/- 3,9 ; PRP J4, J7 et J14 17,7 +/- 3,3 jours. La profondeur de la cicatrice, bien que statistiquement significative (ANOVA p = 0,026 ) : 5 +/- 1 (contrôle) ; 5,5 +/- 1,1 (1 PRP) ; 5,4 +/- 1,1 (2 PRP) ; 5,5 +/- 0,6 (3 PRP) mm n'est pas considérée comme cliniquement significative. PRP donne des résultats équivalents aux topiques antibiotiques sur une brûlure intermédiaire du porc.

Immediate tangential excision accelerates wound closure but does not reduce scarring of mid-dermal porcine burns.

Current evidence supports the use of excision to remove eschar from deep dermal and full-thickness burns. However, the role of excision of mid-dermal burns remains unclear. This study aimed to develop a porcine model that could produce reproducible middermal thermal burns that undergo tangential excision; and investigate the effects of immediate tangential excision (30 minutes postburn) on healing and scarring. An aluminum bar preheated in hot water (70°C) was applied for 20 or 30 s to produce a total of sixteen mid-dermal burns per pig on each of six pigs. Thirty minutes after burn creation, half of the burns were tangentially excised. Four partial- thickness wounds per pig were created as controls. Depth of burn injury (1 and 24 h), reepithelialization (7 and 10 d) and scar depth (28 d) were assessed microscopically. Total scar surface area was grossly evaluated on day 28. Exposure of porcine skin to a preheated aluminum bar at 70 °C for 20 or 30 sec resulted in reproducible mid-dermal burns, where immediate excision enhanced complete wound closure as judged by complete re-epithelialization, but did not reduce initial depth of injury, scar contraction and scar depth. Immediate surgical intervention is sufficient to enhance wound closure, but not to mitigate mid-dermal burn scar formation. This work provides a suitable animal model to evaluate novel therapies that may be used to inhibit burn progression, accelerate wound closure and decrease scarring, especially those therapies unable to penetrate burn eschar.

Les données actuelles des connaissances sont en faveur de l'excision des brûlures des 2ème degré profond et 3ème degré. L'intérêt de l'excision des brûlures intermédiaires reste mal précisé. Cette étude se penche sur un modèle porcin destiné à la réalisation de brûlures intermédiaires reproductibles et à l'évaluation de l'effet l'excision ultra précoce (30 mn après la brûlure) sur l'épidermisation et la cicatrisation de ces brûlures. Six porcs ont subi chacun un total de 16 brûlures intermédiaires infligées au moyen d'une barre d'aluminium chauffée à 70°C et appliquée pendant 20 à 30 s. La moitié des zones brûlées étaient excisées à la trentième minute. Quatre brûlures superficielles servaient de contrôle. La profondeur de la brûlure (à h1 et h24), la réépithélialisation (à J7 et J10) et l'épaisseur de la cicatrice (à J28), étaient étudiées microscopiquement. La surface cicatricielle totale était évaluée à J28. L'exposition pendant 20 à 30s de la peau d'un porc à de l'aluminium préalablement chauffé à 70°C entraîne une brûlure intermédiaire reproductible. L'excision immédiate en favorise la guérison lorsqu'elle est jugée sur la réépithélialisation mais n'en réduit ni la profondeur, ni la rétraction cicatricielle, pas plus que l'épaisseur de la cicatrice. L'excision immédiate favorise la fermeture de la plaie mais pas son évolution vers des séquelles. Ce travail permet de décrire un modèle animal fiable dans le but d'évaluer de nouvelles thérapeutiques destinées à limiter le progression des lésions, accélérer la fermeture et diminuer la survenues de séquelles, en particulier celles incapables de pénétrer dans une lésion constituée.

Crohn's disease and lichen nitidus: a case report and comparison of common histopathologic features.

We describe a 54-year-old black woman with Crohn's disease, who developed lichen nitidus, the third report of a patient with both diseases. The rarity of these diseases individually and the histopathologic features in common imply that the two diseases are linked. Multinucleated giant cells, a common finding in the lesions of Crohn's disease, are less common in the lesions of lichen nitidus. The presence of multinucleated giant cells in lichen nitidus in all three case reports is distinctly unusual. The infiltrates of Crohn's disease and lichen nitidus contain CD-68-positive macrophages. As such, the subset of lichen nitidus with giant cells should be recognized as a cutaneous manifestation of Crohn's disease.

Transient eruptive seborrheic keratoses associated with erythrodermic psoriasis and erythrodermic drug eruption: report of two cases.

The appearance of multiple seborrheic keratoses in association with underlying internal malignancy (known as the sign of Leser-Trelat) has generated much discussion and debate in the literature. However, comparatively few case reports exist that examine the appearance of multiple seborrheic keratoses associated with exfoliative erythroderma without underlying malignancy. We report 2 cases in which multiple, biopsy-proven seborrheic keratoses appeared in conjunction with erythrodermic skin eruptions. The underlying diseases in these 2 patients included psoriasis and an eczematous drug eruption; in both cases the erythroderma resolved with appropriate treatment. After resolution of the erythroderma, the newly developed seborrheic keratoses proceeded to involute and gradually fall off. Neither of the patients exhibited any evidence of internal malignancy. These cases represent the first reports of psoriasis and drug eruption as causes of erythroderma-induced transient eruptive seborrheic keratoses. Clinical and pathologic findings are consistent with previous descriptions of this entity.

Impact of genotypic variation of Borrelia burgdorferi sensu stricto on kinetics of dissemination and severity of disease in C3H/HeJ mice.

Various genotypes of Borrelia burgdorferi sensu stricto have been previously identified among a large collection of isolates cultured from patients with Lyme disease in the United States. Furthermore, association of specific genotypes with hematogenous dissemination early in the disease course has been observed. The present study assessed kinetics of spirochete dissemination and disease severity in C3H/HeJ mice infected with two different genotypes of B. burgdorferi. Spirochete load in plasma and ear and other tissue samples of infected mice was measured by quantitative PCR, and these data were compared to those obtained by culture and histopathologic analysis. In mice infected with isolate BL206 (a type 1 strain), the peak number of spirochetes was observed in plasma between day 4 and 7, in heart and ear tissue on day 14, and in joints on day 28 postinoculation. There was a correlation between the peak number of spirochetes in plasma on day 4 or 7 and that in ear biopsy and joint specimens on day 14. By contrast, spirochete burdens in plasma of mice infected with isolate B356 (a type 3 strain) were 16- and 5-fold lower than those of BL206-infected mice on days 7 and 14 of infection, respectively. Similarly, approximately 6- and 13-fold fewer spirochetes were detected in the heart tissues of B356-infected mice compared to BL206-infected mice. Histopathologically, severe arthritis and aortitis were noted only in mice infected with isolate BL206. Spirochete dissemination and disease severity vary significantly in mice infected with distinct genotypes of B. burgdorferi, suggesting that genotypic differences in the infecting spirochetes play a key role in the pathogenesis and development of clinical disease.

Histopathologic effects of cutaneous tape stripping in pigs.

OBJECTIVE: The stratum corneum (SC) is the major barrier to topical absorption of medications. Skin tape stripping (TS) removes the stratum corneum, allowing more rapid absorption of drugs such as local anesthetics. Prior to evaluating TS in human clinical trials, this study was performed to evaluate its immediate and delayed histopathologic effects in swine. METHODS: This was a prospective, interventional, longitudinal, experimental animal study using two isoflurane-anesthetized young swine. Cellophane tape was applied to the skin of clipped swine flanks and peeled away 10, 15, 20, 25, or 30 times. Each level of tape stripping was performed three times in each pig. Full-thickness biopsies were taken at 30 minutes and two weeks later for blinded histopathologic evaluation by a dermatopathologist using randomly ordered hematoxylin-and-eosin-stained tissue sections and conventional light microscopy. The absolute thickness of the cornified layer was measured and compared with normal (unstripped) cornified layer. RESULTS: Tape stripping up to 30 times produces thinning of the SC without detectable changes in the underlying epidermis and dermis at 30 minutes and 14 days post-stripping. The degree of thinning was proportional to the number of tape applications. Complete recovery of the cornified layer was noted at two weeks. There were no adverse effects, such as infection, scarring, or inflammatory cell infiltrates. CONCLUSIONS: Under the conditions studied, TS not only appears safe, but appears to produce no long-term sequelae.

Development of a histomorphologic scale to quantify cutaneous scars after burns.

OBJECTIVE: Cutaneous wound healing in adults invariably results in scarring; however, there are few scales to quantify the degree of such scarring. The authors developed a histomorphologic scale for quantifying scarring after cutaneous burn injury. METHODS: As part of a randomized trial comparing a variety of burn therapies, 40 partial-thickness burns were created on the backs and flanks of anesthetized pigs and treated with a tissue adhesive, antibiotic ointment, occlusive dressing, or dry gauze. Gross scar appearance was independently assessed by two investigators at 90 days on a 100-mm visual analog scale (VAS) marked "best appearance" at the high end. One of the investigators repeated the observation 30 days later. Full-thickness biopsies were taken 90 days after injury and evaluated histologically by a dermatopathologist for the presence of hyperkeratosis, epidermal hyperplasia, presence and depth of scar (defined as abnormally oriented collagen under polarized light), fibroplasia, vascular proliferation, and absence of adnexa, including hair follicles, apocrine glands, and smooth muscles. One point was assigned for each category in the presence of a normal finding, whereas an abnormal finding was assigned a score of zero. The normal dermis (absence of abnormal collagen) was given a score of 3, while decreasing scores of 2 to 0 were given for progressively deeper scars (i.e., 2 for papillary dermis, 1 for upper half of reticular dermis, and 0 for deep dermal lower half). The total histomorphologic score was derived by adding the scores on the individual items. The score ranges from 0 to 10 from worst scarring to absence of scarring, respectively. A subset of observations was evaluated a second time by one of the observers one month later. Intraobserver reliability of the histomorphologic scale was assessed with Spearman's correlation. Inter- and intraobserver Pearson's correlations for the gross scar VAS were calculated, and the correlation between gross and histomorphologic scores was assessed. RESULTS: Intraobserver correlation for individual histomorphologic categories ranged from 0.19 to 1.00. Intraobserver correlation for the total histologic score was 0.95. Inter- and intraobserver correlations for the gross scar VAS were 0.8 each. Correlation between the histomorphologic scale and the gross scar VAS was 0.38. CONCLUSIONS: A new reliable histomorphologic method for quantifying and scoring cutaneous scars is described together with a reliable scar VAS. However, these two scales are not highly correlated.

Standardized burn model using a multiparametric histologic analysis of burn depth.

OBJECTIVE: Burn depth and extent determine prognosis and therapy. The current classification into first-, second-, and third-degree burns is crude, making comparisons between studies difficult. The authors standardized a reproducible burn model and a precise histopathologic method for describing burn depth in swine. METHODS: This was a prospective, cross-sectional interventional animal study. Eighteen paired sets of burns were inflicted on the clipped flank skin of two anesthetized domestic pigs with a 2.5 cm by 2.5 cm by 7.5 cm aluminum bar preheated in water to 50 degrees C, 60 degrees C, 70 degrees C, 80 degrees C, 90 degrees C, degrees C or 100 degrees C. The bar was applied for 10, 20, or 30 seconds. Full-thickness skin biopsies were obtained 30 minutes after injury for blinded histopathologic evaluation using hematoxylin and eosin staining. Two dermatopathologists made two sets of measurements and were masked to each other's evaluations. The depth of injury was measured with an ocular microtome for each of five dermal parameters: collagen discoloration, intercollagen basophilic material, endothelial cell necrosis, epithelial cell necrosis, and mesenchymal cell necrosis. The correlation between burn depths of the paired sets of experiments was calculated to assess the reliability of the model. Inter- and intraobserver correlations were calculated to assess the reliability of the scale. Analysis of variance (ANOVA) was used to assess the relation between temperature and exposure times on burn depth. RESULTS: Depth of injury for all five dermal elements was related to temperature and exposure times (ANOVA, p < 0.001 for each). The depth of injury in the paired sets of burns was highly consistent (Pearson correlation, range = 0.88-0.95). Inter- and intraobserver correlations were excellent for all measured elements (range = 0.91-0.97 and 0.95-0.99, respectively). CONCLUSIONS: The authors describe a simple and reproducible animal burn model and histopathologic scale for measuring burn depth that they believe will facilitate standardization and comparison within future burn studies.

Octylcyanoacrylate versus polyurethane for treatment of burns in swine: a randomized trial.

In order to determine whether the enhanced reepithelialization of second-degree burns treated with octylcyanoacrylate (OCA) was due to its occlusive nature we compared reepithelialization (REP) and infection rates of second degree burns treated with OCA and polyurethane film (Tegaderm) in swine. Forty-four standardized partial thickness burns were created by applying an aluminum bar preheated to 80 degrees C to the backs of pigs for 20 s and randomly treated with OCA or Tegaderm. Full thickness biopsies were taken at 7, 10 and 14 days for blinded histopathological evaluation of rates of infection and reepithelialization. T-tests and chi(2) tests were used for group comparisons. There were no between group difference in the rates of reepithelialization and infection. All wounds were reepithelialized by day 14 and there were no infections in either group. We conclude that treatment of partial thickness burns with OCA spray or Tegaderm results in similar rates of reepithelialization and infection, suggesting that the beneficial effects of OCA on reepithelialization are due to its occlusive nature.

Octylcyanoacrylate for the treatment of contaminated partial-thickness burns in swine: a randomized controlled experiment.

OBJECTIVE: To compare infection and reepithelialization rates of contaminated second-degree burns treated with octylcyanoacrylate (OCA), silver sulfadiazine (SSD), polyurethane (PU) film, and dry gauze (control; C) in swine. METHODS: Eighty standardized burns were created by applying an aluminum bar preheated to 80 degrees C to the backs and flanks of young pigs for 20 seconds. All burns were immediately contaminated with 0.1 mL of Staphylococcus aureus 10(5)/mL and randomly treated with OCA spray, SSD, PU, or dry gauze (C). Full-thickness biopsies were taken at 3, 7, and 14 days for blinded histopathologic evaluation using hematoxylin and eosin (H&E)-stained slides. Burns were considered infected in the presence of interstitial reticular dermal neutrophils containing bacteria (intraobserver agreement, kappa = 1.00). Quantitative wound cultures were performed on a second day-3 specimen. RESULTS: At day 3, wound infection rates were 30% (OCA), 50% (SSD), 55% (PU), and 50% (C); p = 0.40 (Kruskal-Wallis test). At day 7, infection rates were 35% (OCA), 85% (SSD), 70% (PU), and 65% (C); p = 0.01. Median bacterial counts at day 3 were 6,500 (OCA), 20,000 (SSD), 1,000,000 (PU), and 650,000 (C); p = 0.29. The proportion of completely reepithelialized wounds at day 14 were 75% (OCA), 90% (SSD), 85% (PU), and 90% (C); p = 0.50. CONCLUSIONS: Treatment of contaminated partial-thickness burns with OCA spray resulted in fewer infections at one week than with the other three treatments.

The effects of epidermal debridement of partial-thickness burns on infection and reepithelialization in swine.

OBJECTIVE: Early postburn debridement of burn blisters is controversial. This study was conducted to compare rates of infection and reepithelialization in debrided vs nondebrided second-degree burns in swine. METHODS: This was a prospective, blinded, controlled, experimental trial using isoflurane-anesthetized swine. Standardized partial-thickness burns were inflicted by applying an aluminum bar preheated to 80 degrees C to the backs and flanks of two young pigs for 20 seconds. In half of the burns the necrotic epidermis was manually debrided. All burns were randomly treated with octylcyanoacrylate spray (OCA) or dry gauze (C). Full-thickness biopsies were taken at 7, 10, and 14 days for blinded histopathologic evaluation. The primary outcomes were the proportions of infected burns at days 7 and 10 and the proportion of completely reepithelialized burns at day 14. Burns were considered infected in the presence of intradermal neutrophils containing bacteria (intraobserver agreement, K = 1.00). A secondary outcome was the proportion of burns with the presence of scar tissue (abnormal collagen under polarized light; intraobserver correlation, K = 0.93). Chi-square tests were used for group comparisons. This study had 90% power to detect a 40-percentage-point difference in infection rates (alpha = 0.05). RESULTS: A total of 126 biopsies from 42 burns were available for review. Infection rates were higher in the debrided burns both at day 7 (55% vs 4.5%, p < 0.001) and at day 10 (65% vs 9%, p < 0.001) after injury. The proportion of nondebrided burns that were completely reepithelialized was higher at days 10 (68% vs 0%, p < 0.001) and 14 (100% vs 65%, p = 0.003). The presence of scar tissue was more common in debrided burns (75% vs 4.5%, p < 0.001). Burns treated with OCA had fewer infections than controls (4% vs 55%, p < 0.001). Fewer OCA-treated debrided burns were reepithelialized at 14 days than those that were not debrided (30% vs 100%, p = 0.001). CONCLUSIONS: Under the current study conditions, early postburn epidermal debridement of second-degree burns resulted in more infections and slower reepithelialization rates in swine. The effects of early postburn epidermal debridement in humans should be explored.

Condyloma acuminatum in a cynomolgus monkey (Macaca fascicularis).

Condyloma acuminatum was found on the penile shaft and glans of a wild-caught cynomolgus monkey. The characteristic cauliflower-like, digitated lesions corresponded histopathologically with epidermal hyperplasia, hyperkeratosis, hypergranulosis, pallor of the mid-spinous zone, and crowding of keratinocytes. Electron microscopy revealed 10 intranuclear viral particles. In situ hybridization studies using human DNA probes (pan-Human Papillomavirus [HPV] 6/11, HPV 16/18, and HPV 31/33) all failed to hybridize. Polymerase chain reaction using papillomavirus probes MY09, MY11, GP5, and GP6 failed to amplify HPV DNA. We conclude that this lesion likely is a viral-induced condyloma but that the virus is not detectable by using presently available human or monkey papillomavirus probes.

Comparative trial of octyl-cyanoacrylate and silver sulfadiazine for the treatment of full-thickness skin wounds.

A prospective, randomized, blinded, controlled experimental trial was performed in pigs to compare the rates of reepithelialization of 126 full-thickness cutaneous 4-mm punches treated with an octyl-cyanoacrylate spray, silver sulfadiazine, or a dry gauze (controls). Full thickness biopsies were taken 7, 14, or 30 days later for histopathological evaluation of hematoxylin and eosin stained tissue sections by a dermatopathologist. The primary outcome measure was the proportion of wounds completely re-epithelialized at days 7 and 14. Secondary outcomes were the rates of infection, foreign body reactions, and the depth of any resulting cutaneous dells measured with a micrometer. Between-group comparisons were performed with ANOVA or Chi-square tests. Octyl-cyanoacrylate treated wounds re-epithelialized more slowly, as fewer wounds treated with octyl-cyanoacrylate were re-epithelialized at day 7 in comparison with silver sulfadiazine or control wounds (50% vs. 90% vs. 100%, p < 0.001). There were no infections or foreign body type reactions. Amounts of granulation tissue were similar among groups. Octyl-cyanoacrylate wounds were more depressed than silver sulfadiazine wounds at days 7 and 14 yet had similar histopathological characteristics at day 30. We conclude that treatment of small, full thickness cutaneous wounds with octyl-cyanoacrylate results in delayed re-epithelialization and dermal repair in comparison with silver sulfadiazine, yet it does not result in any foreign body-type reaction. However, by 30 days, histopathological wound characteristics were similar in all groups.

Octylcyanoacrylate for the treatment of partial-thickness burns in swine: a randomized, controlled experiment.

OBJECTIVE: To compare re-epithelialization rates of superficial partial-thickness burns treated with octylcyanoacrylate (OCA), silver sulfadiazine (SSD), and dry gauze (controls) in swine. METHODS: This was a prospective, longitudinal, blinded, controlled, experimental trial using anesthetized swine. Sixty-three standardized burns were created by applying an aluminum bar preheated to 80 degrees C for 20 seconds to the flanks of four young pigs. Three equal sets of 21 burns were randomly treated with OCA spray, SSD, or dry gauze (controls). Full-thickness biopsies were taken after 30 minutes and at seven and 14 days for blinded histopathologic evaluation by two dermatopathologists using hematoxylin and eosin staining. The percent of wound re-epithelialization was measured at days 7 and 14, calculated by dividing the length of the regenerated epidermis by the measured width of the biopsy. Analysis of variance (ANOVA) and repeated-measures ANOVA controlling for the individual pig were used for comparisons among groups. This study had 80% power to demonstrate a large between-group difference in percent re-epithelization (alpha = 0.05). RESULTS: There were 63 burns and 126 biopsies. Ten biopsies were excluded for technical reasons. At seven days, there was a significant between-group difference in percent re-epithelialization. Percent re-epithelialization was greatest in the OCA group (65.0%), followed by the SSD group (37.6%), and lowest in the control group (8.8%). At 14 days, all wounds demonstrated near complete re-epithelialization and there was no significant difference in the percent of re-epithelialization among the groups. There was only one wound infection in the OCA group. CONCLUSIONS: Under these study conditions, treatment of partial-thickness burns with OCA spray resulted in a higher percent of re-epithelialization at seven but not 14 days when compared with both SSD and control, with no significant increase in infection rates. Future studies should evaluate the use of OCA for the treatment of burns in humans.

Low-frequency sonophoresis: pathologic and thermal effects in dogs.

OBJECTIVE: Low-frequency sonophoresis has recently been shown to significantly facilitate transdermal permeability of various substances (e.g., insulin) in animal models, thus eliminating the need to inject such agents. Prior to human trials, the authors studied the safety profile of low-frequency sonophoresis in dogs by evaluating microscopic and temperature changes in the skin after sonophoresis. METHODS: An evaluator-blinded canine study of sonophoresis using different energy intensities and probe diameters was performed. Low-frequency ultrasound was applied for 60 seconds to the clipped abdominal skin of 3 anesthetized adult mongrel dogs using a sonicator operating at a frequency of 20 KHz with a maximal energy output of 400 W. The sonicator was immersed in normal saline, and intensities of 4%, 10%, 20%, 30%, and 50% were applied during 600 msec of every second (pulsed mode). Three probes, 1-cm cylindrical, 5-cm cylindrical, and 10-cm disc-shaped, were evaluated. Each experimental condition was performed twice. Subcutaneous temperatures were measured by temperature probe before and after sonophoresis. At 30 minutes post-sonophoresis, full-thickness skin biopsies were taken for blinded histopathologic evaluation. RESULTS: Minimal urticarial reactions were noted with the 1-cm probe at intensities of < or = 20% and with the 5-cm probe at 4% intensity. With higher intensity, thermal injuries were observed grossly with erythema and vesicles. The microscopic correlates were papillary and dermal edema with neutrophils and telangiectasia. The conditions producing vesicles grossly had foci of epidermal necrosis, subepidermal vesicles, and degeneration of papillary dermal collagen. With still higher intensities, confluent epidermal necrosis became apparent. Use of the 10-cm probe did not result in any injury. CONCLUSIONS: Low-frequency ultrasound at low intensities appears safe for use to enhance the topical delivery of medications, producing only minimal urticarial reactions. Higher-intensity conditions resulted in second-degree burns, most likely attributable to localized heating.

Topically applied CMT-2 enhances wound healing in streptozotocin diabetic rat skin.

Delayed wound healing is one of the complications of diabetes mellitus, exhibited by increased wound collagenase and decreased granulation tissues. The current study compared wound healing in normal and diabetic rats, and the effects of topically applied 1% or 3% concentrations of chemically modified tetracycline-2 (CMT-2) on 6-mm circular full-thickness skin wounds healed by secondary intention. On day 7 after wounding, tissues were removed for biochemical analysis and histology. The wound granulation tissue hydroxyproline was less in the untreated diabetic rat with increased collagenase and gelatinase. Treating the diabetic rat wounds with 3% CMT-2 increased the wound hydroxyproline and decreased activities of gelatinase and collagenase. There was a delay in wound filling by granulation tissue in diabetic rats. In CMT-2-treated diabetic rats, the volume of granulation tissue was greater than that in untreated diabetic rats. CMT-2 appears to normalize wound healing in diabetic rats and may be a valuable adjunct in the treatment of chronic wounds.

Mesenchymal cell activation is the rate-limiting step of granulation tissue induction.

During wound repair a 3-day lag occurs between injury and granulation tissue development. When full-thickness, 8-mm-round, excisional wounds were made in the paravertebral skin of outbred Yorkshire pigs and harvested at various times, no granulation tissue was observed before day 4. Day 4 wounds were 3% filled with granulation tissue, day 5 wounds 48% filled, and day 7 wounds 88% filled. The prerequisites for granulation tissue induction are not known but hypothetically include fibrin matrix maturation or cell activation. To examine whether matrix maturation was necessary, wounds were allowed to heal for 5 or 7 days and then aggressively curetted, resulting in the formation of fresh fibrin clots in the newly formed wound spaces. In contrast to original wounds, no lag phase was observed; wounds curetted on day 5 were 23% filled with granulation tissue 1 day later and 99% filled 3 days later, whereas wounds curetted on day 7 were 47% filled 1 day later and completely filled within 2 days. Thus, granulation tissue formation resumed promptly and independently of fibrin clot matrix maturation. This observation suggested that mesenchymal cell activation might be the rate-limiting step in granulation tissue formation. To address this hypothesis more directly, cultured porcine or human fibroblasts, grown to 80% confluence in Dulbecco's minimal essential medium plus 10% fetal calf serum, were added to new wounds. These wounds were sealed with a freshly made exogenous fibrin clot. In some wounds, platelet releasate was added to the fibrin clot. Granulation tissue did not form in day 3 wounds, which had received either fibrin alone, fibrin and platelet releasate, or fibrin and fibroblasts. In contrast, granulation tissue was observed in wounds receiving fibrin, human fibroblasts, and platelet releasate. By day 4, wounds receiving cultured human fibroblasts, fibrin, and platelet releasate were 14% filled with granulation tissue compared with less than 4% granulation tissue in control wounds. Thus, fibroblast activation is a limiting step of granulation tissue formation, and continued cell stimulation is required for accelerated development.