Histopathology of persistent long COVID toe: A case report.

During the 2020 coronavirus (SARS-CoV-2) pandemic, several cutaneous lesions were identified, including pseudo-chilblain, vesicular, urticarial, maculopapular, and livedo/necrosis. A 59-year-old obese man with probable COVID-19 developed painful cyanosis with histopathologic capillary thrombosis of toes, and the cyanosis persisted for nearly 22 months. Shortly after initial exposure to family members with documented SARS-CoV-2, he developed upper respiratory symptoms, yet his anti-SARS-CoV-2 antibody and nasal swab RT-PCR tests were repeatedly negative. Two family members were hospitalized and one of them succumbed with documented SARS-CoV-2 pneumonia within 10 days of exposure. Biopsy specimen of the distal toe 16 weeks after initial exposure showed papillary dermal capillary thrombosis with endothelial swelling, telangiectasia, and peri-eccrine lymphocytic infiltrates resembling pernio. Overall, this is the first case of biopsy specimen of "long COVID toe" following presumed SARS-CoV-2 exposure, with a demonstration of thrombotic vasculopathy, toe cyanosis, and pernio-like pathology.

ADAMTS9 and ADAMTS20 are differentially affected by loss of B3GLCT in mouse model of Peters plus syndrome.

Peters plus syndrome (MIM #261540 PTRPLS), characterized by defects in eye development, prominent forehead, hypertelorism, short stature and brachydactyly, is caused by mutations in the ß3-glucosyltransferase (B3GLCT) gene. Protein O-fucosyltransferase 2 (POFUT2) and B3GLCT work sequentially to add an O-linked glucose ß1-3fucose disaccharide to properly folded thrombospondin type 1 repeats (TSRs). Forty-nine proteins are predicted to be modified by POFUT2, and nearly half are members of the ADAMTS superfamily. Previous studies suggested that O-linked fucose is essential for folding and secretion of POFUT2-modified proteins and that B3GLCT-mediated extension to the disaccharide is essential for only a subset of targets. To test this hypothesis and gain insight into the origin of PTRPLS developmental defects, we developed and characterized two mouse B3glct knockout alleles. Using these models, we tested the role of B3GLCT in enabling function of ADAMTS9 and ADAMTS20, two highly conserved targets whose functions are well characterized in mouse development. The mouse B3glct mutants developed craniofacial and skeletal abnormalities comparable to PTRPLS. In addition, we observed highly penetrant hydrocephalus, white spotting and soft tissue syndactyly. We provide strong genetic and biochemical evidence that hydrocephalus and white spotting in B3glct mutants resulted from loss of ADAMTS20, eye abnormalities from partial reduction of ADAMTS9 and cleft palate from loss of ADAMTS20 and partially reduced ADAMTS9 function. Combined, these results provide compelling evidence that ADAMTS9 and ADAMTS20 were differentially sensitive to B3GLCT inactivation and suggest that the developmental defects in PTRPLS result from disruption of a subset of highly sensitive POFUT2/B3GLCT targets such as ADAMTS20.

The effect of tadalafil on reepithelialization and scarring of partial thickness porcine burns.

Burn conversion from second to third degree is common leading to delayed healing and scarring. We hypothesized that tadalafil, a phosphodiesterase 5 inhibitor (PDE5I) that results in vasodilation, would reduce burn conversion leading to faster reepithelialization and less scarring of partial thickness porcine burns. We conducted a prospective, randomized, controlled, animal experiment using six female pigs (25-30 kg). We created 20 standardized partial thickness burns on each of the animals with an aluminum bar preheated to 80 °C and applied for 20 seconds to the pigs' dorsum. Three animals each were randomized to oral tadalafil 2.5 mg or control vehicle once daily for 1 week. Main outcomes were time to reepithelialization and depth of scarring at 28 days. A sample of 60 burns in each treatment group had 80% power to detect a 2-day difference in time to reepithelialization. Mean (95% CI) time to reepithelialization in burns treated with tadalafil and control were 14.9 (14.1-15.7) vs. 19.7 (18.2-21.3) days, respectively; mean difference 4.8 (3.1-6.6) days. After controlling for pig and within pig differences, mean time to reepithelialization was 6.5 (3.7-9.3) days shorter in burns treated with tadalafil compared with controls. Mean (95% CI) scar depth in burns treated with tadalafil and control were 2.7 (2.3-3.1) vs. 3.7 (3.1-4.2) mm. respectively, mean difference 1 (0.3-1.7) mm. After controlling for pig and within pig differences, scar depth in tadalafil-treated burns was 1.5 (0.7-2.3) mm lower compared with controls. We conclude that once daily oral tadalafil shortened time to reepithelialization and reduced scarring in a partial thickness porcine burns model.

Comparison of comparable scald and contact burns in a porcine model: A preliminary report.

Whether the depth and healing of scalds and contact burns are similar is controversial. Due to water's greater heat capacity, we hypothesized that when exposed to similar temperatures and durations of exposure, burns caused by hot water would be deeper than those caused by contact with hot metal. Forty standardized burns were created in two anesthetized female domestic pigs using a brass bar or circulating heated water. In one pig, the temperature was kept constant (95°C) while the duration of exposure varied (5, 10, 15 seconds) In the second pig, the exposure time was kept constant (10 seconds) while the temperature of exposure varied (70°C, 80°C, 98°C). Periodic punch biopsies were taken to determine burn depth immediately after injury, percentage burns reepithelialized within 21 days, and depth of scar at 28 days. The analysis was performed using analysis of variance. When the temperature was held constant, duration of exposure (5, 10, and 15 seconds) was associated with scar depth (2.1 vs 3.8 vs 5.0 mm, respectively, P = 0.001) but not with burn depth (2.0 vs 2.2 vs 2.3 mm, respectively, P = 0.10). When exposure duration was held constant, temperature (70°C, 80°C, 98°C) was associated with scar depth (0.6 vs 1.7 vs 3.6, P < 0.001) but not with burn depth (1.2 vs 1.5 vs 1.7 mm, respectively, P = 0.21). Burn depths were greater for scald than contact burns although not significantly greater. After controlling for temperature, the difference in scar depth between scalds and contact burns was statistically significant (marginal means 3.0 for contact burns, 4.3 for scalds, P = 0.008). We conclude that burns created in swine with circulating hot water result in deeper scars than those created by contact with a brass bar when controlling for temperature and duration of exposure.

Survival of human cadaver skin on severe combined immune deficiency pigs: Proof of concept.

Transplantation of human xenografts onto immunocompromised mice is a powerful research tool for studying wound healing. However, differences in healing between humans and mice and their small size limit this model. We determined whether human cadaver skin xenografts transplanted onto pigs with severe combined immune deficiency (SCID) would survive and not be rejected. Meshed (1:1.5), cryopreserved human cadaver skin was transplanted onto 10 partial thickness dermatome wounds in each of two normal domestic pigs and two SCID pigs. Autografts (n = 2/animal) from the four animals were used as controls. In normal pigs, all autografts were engrafted and healed with a minimal, if any, inflammation and scarring. All human xenografts were rejected by the normal pigs within 5-11 days and associated with an intense T-cell inflammatory response. In contrast, both autografts and xenografts were engrafted and survived the 28-day study in the SCID pigs with a minimal inflammation and no gross scarring.

Blood vessel occlusion with erythrocyte aggregates causes burn injury progression-microvasculature dilation as a possible therapy.

Burns are dynamic injuries characterized by progressive tissue death and continuous severe pain over the course of several days. The extent of burn injury progression determines the ultimate patient outcome. Initial burns result in a central zone of necrosis surrounded by a potentially viable zone of ischemia. Several mechanisms have been proposed to explain injury progression, including oxidant and cytokine stress resulting from either ischemia/reperfusion and/or inflammation, but no proven therapy has emerged. To address the unmet need to limit burn injury progression, the root cause of this process must be delineated. For this reason, we have recently focused on post-burn blood vessel occlusion, currently ascribed to microthrombi. We have found that blood vessel occlusion is initially, mainly and persistently caused by erythrocyte aggregation. Although thermal-induced cell necrosis is the immediate cause of cell death, apoptotic cells from persistent ischemia/anoxia, admixed with inflammatory cells, form a band between viable and nonviable tissue 24 hours later. The delayed cell death by apoptosis appears to be the main attractant for inflammatory cells. Finally, we posit that fibrinogen elevation arising from inflammation provides stimulus for additional erythrocyte aggregation, further extending blood vessel occlusion. In our view this persistent occlusion with resultant prolonged tissue ischemia/anoxia, not ischemia/reperfusion, is the root cause of burn injury progression concomitant with associated severe and persistent pain. Epiviosamines, a new class of peptides, appear to selectively dilate microvasculature, and may provide therapy for burn injury progression.

Laser-assisted indocyanine green dye angiography accurately predicts the split-thickness graft timing of integra artificial dermis.

BACKGROUND: The use of an artificial dermal substitute such as Integra-a bilaminate combination of thin silicone and cross-linked bovine tendon collagen and chondroitin-6-sulfate-has become a popular method to address large surface area wounds or smaller, complex wounds devoid of a vascular bed. The incorporation of Integra depends on a vascular wound bed or periphery and can take 4 weeks or longer to occur. If the Integra has not fully incorporated at the time of placement of the split-thickness graft, complete graft loss may result. The availability of a minimally invasive method to assess the incorporation of Integra would be of great value. METHODS: Two 5 × 10-cm paraspinal full-thickness wounds were created on 3 female swine. Wounds were randomly assigned full-thickness skin graft or Integra (Plainsboro, NJ) treatment. Both types of grafts were placed after the application of fibrin glue (Tisseel, Deerfield, Ill) to the wound bed. Laser Doppler imaging (LDI) (Moor), indocyanine green dye (ICG) angiography (LifeCell SPY), and clinical scoring were performed weekly for a period of 8 weeks after grafting. At 4 weeks, the silicone layer of the Integra was removed, and a culture of autologous keratinocytes was applied. A 4-mm punch biopsy sample of each graft was taken 1, 2, 4, 6, 7, and 8 weeks postoperatively for histologic analysis. RESULTS: Both ICG angiography and LDI perfusion measurements noted an increase in perfusion at the Integra graft site that peaked 3 weeks after grafting, corresponding with the start of neovascularization and the optimal time for the application of a split-thickness skin graft. indocyanine green dye angiography measurements exhibit greater reproducibility between animals at late time points as compared with LDI. This decrease in LDI precision is directly related to increases in scar tissue thickness of greater than 5 mm as determined via histologic analysis and corresponds with the accepted maximum penetration depth of the LDI laser. CONCLUSIONS: Indocyanine green dye angiography may provide valuable information as to graft integrity and split-thickness skin graft timing at late time points. Range of LDI seems to be insufficient for split-thickness graft timing or late time point accuracy. Future exploration of ICG angiography potential will involve tracking Integra graft delay in porcine models.

Endothelial necrosis at 1 hour postburn predicts progression of tissue injury.

Burn injury progression has not been well characterized at the cellular level. To define burn injury progression in terms of cell death, histopathologic spatiotemporal relationships of cellular necrosis and apoptosis were investigated in a validated porcine model of vertical burn injury progression. Cell necrosis was identified by high mobility group box 1 protein and apoptosis by Caspase 3a staining of tissue samples taken 1 hour, 24 hours, and 7 days postburn. Level of endothelial cell necrosis at 1 hour was predictive of level of apoptosis at 24 hours (Pearson's r = 0.87) and of level of tissue necrosis at 7 days (Pearson's r = 0.87). Furthermore, endothelial cell necrosis was deeper than interstitial cell necrosis at 1 hour (p < 0.001). Endothelial cell necrosis at 1 hour divided the zone of injury progression (Jackson's zone of stasis) into an upper subzone with necrotic endothelial cells and initially viable adnexal and interstitial cells at 1 hour that progressed to necrosis by 24 hours and a lower zone with initially viable endothelial cells at 1 hour but necrosis and apoptosis of all cell types by 24 hours. Importantly, this spatiotemporal series of events and rapid progression resembles myocardial infarction and stroke and implicates mechanisms of these injuries, ischemia, ischemia reperfusion, and programmed cell death in burn progression.

Melanoma masquerading as xanthogranuloma: a diagnostic pitfall.

Melanoma can present with protean combinations and permutations of histologic features mimicking a plethora of nonmelanocytic benign and malignant proliferations. Anecdotal cases of melanoma closely simulating fibrohistiocytic proliferations have been reported. At times, the reliable differentiation between melanoma and histiocytic proliferations could be vexing histopathologically. We report an unusual presentation of melanoma in an 87-year-old man strikingly resembling xanthogranuloma both clinically and histopathologically. Histologic sections revealed a diffuse proliferation of pleomorphic cells some with foamy cytoplasm and occasional Touton-like giant cells in the dermis accompanied by inflammatory cells. Rare single-cell pagetoid scatter was evident within the epidermis. The infiltrate had patchy staining on CD163, interpreted as part of the inflammatory component but the atypical cells stained heavily with Melan A and tyrosinase confirming the diagnosis of malignant melanoma. Our case demonstrates yet another face of malignant melanoma and the critical but judicious use of immunohistochemistry in reliably distinguishing between melanoma and histiocytic tumors.

Verhoeff van Gieson staining in laser-irradiated gingival tissues.

There have been several studies on the use of the Verhoeff van Gieson staining method to demonstrate thermal effects on tissues. However, this method has rarely been used for the analysis of periodontal tissues. This study was undertaken to compare the quality and effectiveness of the Verhoeff van Gieson (VVG) staining method with conventional hematoxylin & eosin (H&E) in measuring the thermal effects in gingival tissues. Periodontal tissues around bovine mandibular teeth were treated using different surgical lasers (wavelengths of 10,600 nm, 970 nm, and 445 nm) at 2 W power setting. Measurements of the depth of the coagulation zone were recorded for all treatment groups in sample tissues stained with H&E as well as the VVG-staining method. Measures were interpreted by a trained pathologist. A statistical analysis was performed using the Wilcoxon signed-rank test to determine if there was a statistically significant difference between values recorded for the light penetration depth on tissues stained with each of the two staining methods. It was determined that there was no significant difference in the recorded values (P = 0.23). We have concluded that the VVG-stained tissues were better able to visualize the depth of thermal damage and thus may make it easier for someone not well trained to interpret the depth of light penetration in these tissues.

A Comparison of Topical Agents for Eschar Removal in a Porcine Model: Bromelain-enriched vs Traditional Collagenase Agents.

Surgical excision and grafting of deep partial-thickness (DPT) and full-thickness (FT) burns is a cornerstone of wound care. The use of commercially available topical enzymatic agents has been limited due to slower and less complete eschar removal than surgical excision. Using a porcine model of DPT and FT burns, we compared the eschar removal efficacy of a bromelain-enriched enzymatic agent derived from the stems of pineapple plants and a commercially available collagenase. We created 40 DPT and 40 FT burns on four anesthetized Yorkshire pigs. Eschar removal was initiated 24 hours later. Two pigs each were randomly assigned to collagenase or the bromelain-enriched agent. The bromelain-enriched agent was applied topically once for 4 hours followed by a 2-hour soaking. The collagenase was applied topically daily until complete removal of eschar or for up to 14 days. All bromelain-enriched treated FT burns underwent complete removal of the eschar after a single application while none of the collagenase-treated FT burns underwent complete removal of the eschar even after 14 days of treatment. All bromelain-enriched treated DPT burns had complete eschar removal after the single application. None of the collagenase-treated DPT burns experienced complete removal of eschar after 10 days; by day 14, 35% had complete eschar removal, 30% had >50% eschar removed, and 35% had <50% eschar removed. We conclude that eschar removal is quicker and more complete with the bromelain-enriched compared with collagenase debriding agent.

Histopathologic staining of low temperature cutaneous burns: comparing biomarkers of epithelial and vascular injury reveals utility of HMGB1 and hematoxylin phloxine saffron.

Histopathology remains the gold standard for evaluation of burn depth, progression, and healing, but burn literature offers little guidance on the best stains for analysis of these complex and evolving injuries. A battery of histochemical and immunohistochemical stains was compared on adjacent sections to determine the best stains for histopathologic study and imaging of burns. Using a validated porcine model of vertical burn progression, full-thickness cutaneous biopsies were stained using hematoxylin and eosin, Hematoxylin phloxine saffron (HPS), Masson Trichrome, Elastin Von Gieson, Movatt's Pentachrome, vimentin, CD31, KI-67, caspase 3a, and high mobility group box 1. Depth of collagen degeneration, cellular necrosis, apoptosis, and vascular occlusion; and reparative processes of cellular hyperplasia, reepithelialization, and new collagen deposition were measured by ocular microscopy. High mobility group box 1 was superior for necrosis between 1 and 24 hours postburn. Vimentin underestimated necrosis until 48 hours postburn. For overall assessment, hematoxylin and eosin and HPS were comparable, except for analysis of thermally injured collagen, vessel occlusion, erythrocyte extravasation, and polariscopic study of collagen deposition, where HPS was superior. HPS stain offers specific advantages in histopathologic burn analysis. Inexpensive and rapid to produce, HPS allows users to analyze eosinophilic components more precisely than standard hematoxylin and eosin.

The Maximum-Tolerated Dose and Pharmacokinetics of a Novel Chemically Modified Curcumin in Rats.

PURPOSE: CMC 2.24, a chemically modified curcumin, was developed as a novel, pleiotropic MMP-inhibitor to treat various inflammatory/collagenolytic diseases including periodontitis. To date, this compound has shown efficacy in vitro, in cell culture, and in vivo (oral administration) in mice, rats and dogs. In preparation for possible Phase I human clinical trials, the current study describes the maximum-tolerated-dose (MTD), pharmacokinetics (PK), and toxicology of CMC 2.24 in the rat model. METHODS: For the MTD study, 30 Sprague-Dawley rats were randomly distributed into 5 groups (3M/3F per group): Placebo (vehicle; carboxymethylcellulose) and CMC 2.24 at various doses (50, 100, 500, 1000 mg/kg/day), were administered once daily by oral gavage for 5 days. For the PK study, 24 rats were administered either Placebo or CMC 2.24 (100mg/kg/day) once daily for 28 days or only once (500 or 1000 mg/kg). Analysis of this test compound was done using LC/MS/MS for PK evaluation on blood samples drawn from rats at multiple time points. The animals were sacrificed after 5 or 28 days of treatment, and blood chemistry and serology were analyzed. Major organs (heart, lung, liver, kidney, spleen, intestine, brain) were histologically examined at necropsy. RESULTS: Orally administered, CMC 2.24 did not produce significant changes in body weight, food consumption or adverse events in the MTD and toxicology studies. Moreover, no obvious pathologic changes were observed based on histology, hematology, serum biochemistry, or necropsy compared to placebo-treated controls. The PK study demonstrated a peak-blood concentration (Cmax) at 45 mins after oral administration of 2.24 and a serum half-life of 10 hours. CONCLUSION: In conclusion, CMC 2.24, orally administered to rats once a day, appears to be safe and effective at a wide range of doses, consistent with efficacy previously demonstrated in studies on animal models of various collagenolytic diseases, such as periodontitis, diabetes and cancer.

Spatiotemporal progression of cell death in the zone of ischemia surrounding burns.

Burns are dynamic injuries, characterized by progressive death of surrounding tissue over time. Although central to an understanding of burn injury progression, the spatiotemporal degrees and rates of cellular necrosis and apoptosis in the zone of ischemia surrounding burns are not well characterized. Using a validated porcine hot comb model, we probed periburn tissue at 1, 4, and 24 hours after injury for high-mobility group box 1 as a marker of necrosis and activated cleaved caspase-3 as a marker of apoptosis, followed by spatiotemporal morphometric analysis. We found that necrosis was the most prominent mechanism of cell death in burn injury progression, with significant progression between 1 and 4 hours postburn. Apoptosis appeared not to play a role in early burn injury progression but was observed in cells at the interface of necrotic and viable tissue at 24 hours postburn. Our findings imply that intervention within the first 4 hours following injury is likely necessary to limit burn injury progression. Additionally, based on high-mobility group box 1 staining patterns, we define distinct early, intermediate, and late pathological signs of cell necrosis that may facilitate delineation of causal mechanistic relationships of burn injury progression in vivo.

Validation of a porcine comb burn model.

OBJECTIVE: A brass comb burn model that creates 3 full-thickness burns separated by 3 interspaces of unburned skin representing the zone of ischemia has been described in rats. We evaluated this model in pigs. METHODS: Design--observational. Subjects--6 pigs (20-25 kg). Interventions--4 burns created on each animal on the dorsum using a brass comb with 4 rectangular prongs preheated in boiling water and applied for 30 seconds resulting in 4 rectangular 10 x 20-mm full-thickness burns separated by three 5 x 20-mm unburned interspaces. Outcomes--wounds observed at 1, 2, 3, and 7 days for evidence of necrosis in unburned interspaces. Full-thickness biopsies from interspaces were evaluated with hematoxylin-eosin staining 7 days after injury for evidence of necrosis. Data analysis--the percentages of interspaces progressing to necrosis were analyzed with descriptive statistics. RESULTS: Twenty-four comb burns with 72 unburned interspaces were created evenly distributed between the animals. The percentages of interspaces that progressed to full-thickness necrosis at 1, 2, 3, and 7 days after injury were 88.9% (64/72; 95% confidence interval [CI], 79.6%-94.3%), 88.9% (64/72; 95% CI, 79.6%-94.3%), 88.9% (64/72; 95% CI, 79.6%-94.3%), and 97.7% (70/72; 95% CI, 90.4%-99.2%), respectively. There was perfect agreement between gross inspection and histomorphology. CONCLUSIONS: The comb burn model in swine results in the progression of most unburned ischemic interspaces to full-thickness necrosis within 1 to 7 days.

Melanoma screening with serial whole body photographic change detection using Melanoscan technology.

The use of an automated, whole-body, diffusely lit digital imaging enclosure to produce serial images, which were then compared, using an astrophysics image display method, enabled a private practice dermatologist to detect melanoma at significantly thinner Breslow depths compared to all other clinical detection paradigms examined in this study. The patients were triaged to scanning using a melanoma risk survey system. The system employed a 24 camera semicircular imaging wall, with front and back views. 10,000 whole body photographic scans were obtained. Privacy was maintained with 128-bit image encryption and off-line storage. Image to image comparison of whole body digital photography was combined with a whole body skin exam in order to sensitize a clinical dermatologist to skin changes in individuals at risk for melanoma. Mean depths (Breslow scores) were compiled from six distinct melanoma biopsy cohorts segregated and based on different clinical screening paradigms. The Breslow depth of invasive lesions of the serial screening cohort was significantly less (by at least 0.050 mm) compared to three other clinical screening groups (patient self-detection 0.55 mm, p=0.007; referred by outside non-dermatologist physician 0.73 mm, p=0.03; and serial dermatologic evaluation 0.23 mm, p=0.03) as well as two pathology laboratory cohorts (community hospital laboratory 1.45 mm, p=0.003; dermatopathology laboratory 0.18, p=0.0003). This approach provides a quick and effective method for detection of early melanomas with a significant reduction in the skin area required for lesion examination.

Effect of tadalafil on reduction of necrosis in the ischemic zone in a rat comb burn model.

OBJECTIVES: A major goal of burn management is to reduce the progression of necrosis in the zone of ischemia surrounding the central zone of necrosis. A rat comb burn model is often used to assess the progression of necrosis in the zone of ischemia. We compared various combinations of naproxen [NPX], N-acetyl cysteine [NAC], and tadalafil [TD] (a phosphodiesterase-5 inhibitor used as a vasodilator to treat erectile dysfunction) in a rat comb burn model to determine their effects on injury progression. METHODS: We created two comb burns on the backs of 40 anesthetized Sprague-Dawley rats using a brass comb with four rectangular prongs preheated in boiling water and applied for 30s, resulting in four rectangular 10×20mm full-thickness burns separated by three 5×20mm unburned interspaces, representing the ischemic zones. We randomized five animals each to daily oral gavage with TD (1mg/kg), NPX (10mg/kg), NAC (500mg/kg), NAC+NPX, TD+NPX, TD+NAC, TD+NPX+NAC, or normal saline [NS]. Wounds were observed daily for gross evidence of necrosis in the unburned interspaces and full-thickness biopsies from the interspaces were evaluated with Hematoxylin & Eosin seven days after injury for histological evidence of necrosis. RESULTS: The percentages of interspaces with histological evidence of necrosis at day seven were TD-40%, NPX-93%, NAC-97%, NS-87%, TD+NPX-50%, TD+NAC-40%, TD+NPX+NAC-33%, and NPX+NAC-60% (P<0.001). Repeated measures ANOVA demonstrated reduced gross percentage of interspace area undergoing necrosis in all groups that included TD, compared with all groups not including TD (P<0.001). There were no differences among the various treatments within the groups that did or did not include TD. CONCLUSIONS: Daily oral therapy with tadalafil reduces necrosis in the unburned interspaces compared with naproxen, NAC, or their combination in a rat comb burn model. Addition of naproxen or NAC to tadalafil does not further reduce injury progression.

The effects of topical nitric oxide on healing of partial thickness porcine burns.

BACKGROUND: Nitric oxide is a wound mediator that promotes wound healing. We hypothesized that topical application of nitric oxide would speed reepithelialization, enhance angiogenesis, and reduce scar thickness in a partial thickness porcine burn model. METHODS: While under general anesthesia, 20 partial thickness burns were created on the backs of four female Yorkshire swine using a 2.5cm×2.5cm×7.5cm, 150-g aluminum bar, preheated to 80°C and applied for 20s. The necrotic epidermis was removed and the burns were randomized to low, medium, and high concentrations of a novel nitric-oxide (NO) releasing drug or its ointment vehicle applied 3 times weekly for 28 days. Full thickness punch biopsies were performed at 8, 11, 14 and 28 days after injury to determine percentage wound reepithelialization and scar thickness using H&E staining and blood vessel density using CD31 staining. RESULTS: At day 11, the percentages (SD) wound reepithelialization were: control, 26.3 (34.6); low NO, 23.9 (36.9); medium NO, 43.3 (42.9); and high NO, 59.9 (43.6); ANOVA, P=0.02. The number of CD31 stained blood vessels at days 8 and 11 were greater in wounds treated with high dose NO vs. controls (48.1 vs. 22.9 [P<0.001] and 44.0 vs. 33.5 [P=0.05] per 1mm2 respectively). Scar thicknesses (SD) in mm at day 28 by treatment allocation were: control, 4.8 (1.2); low NO, 4.7 (1.2); medium NO, 4.3 (1.2); and high NO, 4.1 (1.0); P=0.22. CONCLUSIONS: Treatment of partial thickness porcine burns with high concentrations of topical NO resulted in earlier reepithelization and increased angiogenesis but not reduced scar thickness compared with its control vehicle in a partial thickness porcine burn model.

Development of a contaminated ischemic porcine wound model and the evaluation of bromelain based enzymatic debridement.

OBJECTIVES: There are no well accepted animal models of chronic wounds, limiting advances in understanding and treatment of chronic ulcers. We developed a porcine wound model which combines multiple factors involved in chronic wounds to create a contaminated necrotic eschar and evaluated the debriding efficacy of a novel bromelain based enzymatic debriding agent (EscharEx). METHODS: Contaminated ischemic wounds were created on the flanks of domestic pigs by 'sandwiching' the skin between 2 'O' rings (1 placed on the surface of the skin and the other underneath the skin) for 24h prior to dermatomal excision of the necrotic eschar and its contamination with Staphylococcus aureus and Candida albicans. After confirming the development of infected eschars, additional animals were used to compare the effects of daily application of topical EscharEx or its hydrating vehicle on eschar debridement as a control. RESULTS: In all cases, application of the 'O' rings resulted in full thickness necrotic ecshars with invasive infections, which did not reepithelialize and sloughed off spontaneously within 14-21 days. All wounds reepithelialized within 28-42 days forming contracted scars. All EscharEx treated eschars were completely debrided within 7-9 days, while no debridement was evident in eschars treated with the control gel. CONCLUSIONS: Our model simulates the initial phase of chronic wounds characterized by a contaminated necrotic eschar allowing evaluation of wound debriding agents, and that a bromelain-based debriding agent completely debrides the contaminated necrotic eschars within one week in this model.