Patrick S. Cottler

Evaluation of clinically applicable exsanguination treatments to alleviate venous congestion in an animal skin flap model

This study compares the effectiveness of alleviating venous congestion with mechanically‐made outlets or leech therapy in promoting skin flap survival. Free flaps of abdominal skin (3 × 6 cm) were raised on Sprague‐Dawley rats and subjected to ischemic events, simulating venous congestion. Animals received 1) no treatment; 2) two treatments involving two 18‐gauge needle‐puncture outlets; or 3) two sessions of leech therapy. Flap perfusion was monitored with a scanning laser Doppler flowmeter. Photographic images of flaps at 7 days were assessed for areas of normal tissue (n = 15), and laser Doppler flowmeter data consisted of control (n = 6), outlet (n = 6), and leech (n = 7). Both the needle‐puncture outlet (40.0%± 9.24%) and leech treated (34.6%± 7.34%) groups had a significantly greater surviving skin area than untreated control flaps (8.0%± 5.0%), with 2 of 15 flaps receiving mechanical outlets exhibiting > 90% surviving area. After 7 days, laser Doppler flowmeter data showed greater mean perfusion in the outlet (71.7%± 16.8%) and leech (92.6%± 17.2%) treated groups, compared to controls (15.2%± 10.2%). There was a significant increase in perfusion in the outlet (13.3%± 6.2%) and leech (9.1%± 1.1%) treated groups from the end of secondary ischemia to day 7 (p < 0.05) compared to controls. The results suggest that two spatially separated outlets are as effective as one leech in increasing the area of surviving skin in venous congested flaps.

Development of a clinically useful mechanical leech device that promotes flap survival in an animal model of venous-congested skin flaps

The authors describe the design and testing of a mechanical leech device that has shown greater efficacy in alleviating venous congestion and promoting skin flap survival than previously described clinical therapies. Abdominal skin flaps (3 × 6 cm) were raised on Sprague–Dawley rats and were subjected to two ischemic events that simulated clinical venous congestion. The animals received two treatments with the device prototype during 7-day experiment (N = 9). Flap perfusion was monitored with a scanning laser Doppler imager (LDI) and was normalized to adjacent skin perfusion. Photographic images of flaps at 7 days were assessed for areas of nonnecrotic tissue, and LDI data consisted of perfusion measurements at nine time points during the 7-day experiment. The device prototype was able to promote an average survival area in the flap of 60.0 ± 3.5%, which was not only a significant (p < 0.05) increase over previously published control groups (8.0 ± 5.0%) that did not receive any treatment, but was a significant increase over the same treatment schedule with clinically used leeches (34.6 ± 7.3%). At 7 days, LDI data showed flap perfusion to be 65.6 ± 7% of adjacent skin perfusion, a significant increase over this level at the end of the second ischemic event (21 ± 1%;p < 0.05). These results suggest that this device could be used clinically to alleviate venous congestion and to promote flap survival. The device could also be useful for prophylactic treatments and to minimize treatment delays because its long shelf-life permits immediate availability when a treatment decision is made.

Complement Activation and STAT4 Expression Are Associated with Early Inflammation in Diabetic Wounds

Diabetic non-healing wounds are a major clinical problem. The mechanisms leading to poor wound healing in diabetes are multifactorial but unresolved inflammation may be a major contributing factor. The complement system (CS) is the most potent inflammatory cascade in humans and contributes to poor wound healing in animal models. Signal transducer and activator of transcription 4 (STAT4) is a transcription factor expressed in immune and adipose cells and contributes to upregulation of some inflammatory chemokines and cytokines. Persistent CS and STAT4 expression in diabetic wounds may thus contribute to chronic inflammation and delayed healing. The purpose of this study was to characterize CS and STAT4 in early diabetic wounds using db/db mice as a diabetic skin wound model. The CS was found to be activated early in the diabetic wounds as demonstrated by increased anaphylatoxin C5a in wound fluid and C3-fragment deposition by immunostaining. These changes were associated with a 76% increase in nucleated cells in the wounds of db/db mice vs. controls. The novel classical CS inhibitor, Peptide Inhibitor of Complement C1 (PIC1) reduced inflammation when added directly or saturated in an acellular skin scaffold, as reflected by reduced CS components and leukocyte infiltration. A significant increase in expression of STAT4 and the downstream macrophage chemokine CCL2 and its receptor CCR2 were also found in the early wounds of db/db mice compared to non-diabetic controls. These studies provide evidence for two new promising targets to reduce unresolved inflammation and to improve healing of diabetic skin wounds.

Plasticity of Auricular Cartilage in Response to Hormone Therapy

Introduction Correction of auricular deformities can be accomplished through splinting within the first few weeks of life. This is hypothesized to be due to retained circulating maternal estrogens decreasing the structural density of collagen; however, this has not been fully tested. Cartilage elasticity is dependent on the concentration of the proteoglycan aggregate, and hyaluronic acid, a constituent of proteoglycan aggregate, is increased by estrogens. Nonsurgical correction of these deformities in more developed patients has the potential to change clinical practice and eliminate surgical risks. Previous studies have demonstrated preliminary promise with the use of injectable estrogen to treat auricular deformities. For this study, we have validated an animal model and demonstrated the feasibility of a more therapeutically appropriate topical estrogen treatment in restoring neonatal plasticity of auricular cartilage. Methods Ears of 12 New Zealand rabbits were folded and splinted, and assigned an experimental group (estrogen, placebo, and untreated control) (n = 8 ears). Treatment ears received topical estrogen or placebo cream daily for 4 weeks, whereas controls received no treatment. The splints were removed following 2 additional weeks, and photographs were taken to calculate the retained fold angle. Biopsies were also taken for histologic analysis. Results The 8 control ears showed a statistically increased angle from a folded orientation of 46.6 degrees to return of ear position to a normal upright position of 151.2 degrees by the fourth day after splint removal. Both the estrogen-treated and placebo-treated ears responded to splinting with maintained folding (36.6 degrees and 32.5 degrees, respectively). Auricular cartilage thickness trended toward thicker in ears treated with estrogen, consistent with increased matrix components. Conclusions Estrogen and placebo treatment with splinting of ears lead to a significant change to the cartilage configuration, validating the model. The results of this study are very encouraging and provide the foundation for a noninvasive therapeutic approach for correcting auricular deformities. Future work will include a more detailed mechanistic study evaluating the dosing of estrogen and the efficiency of dermal penetration as well as evaluating the long-term outcomes and molecular mechanism-associated cartilaginous responses to estrogen.

Computer Simulation and Optimization of Cranial Vault Distraction

Objective: The objective of this study was to validate the proof of concept of a computer-simulated cranial distraction, demonstrating accurate shape and end volume. Design: Detailed modeling was performed on pre- and postoperative computed tomographic (CT) scans to generate accurate measurements of intracranial volume. Additionally, digital distraction simulations were performed on the preoperative scan and the resultant intracranial volume and shape were evaluated. Setting: Tertiary Children’s Hospital. Patients, Participants: Preoperative and postoperative CT images were used from 10 patients having undergone cranial distraction for cephalocranial disproportion. Interventions: None; computer simulation. Main Outcome Measure: Computer simulation feasibility of cranial vault distraction was demonstrated through creation of digital osteotomies, simulating distraction through translating skull segments, followed by simulated consolidation. Accuracy of the model was evaluated through comparing the intracranial volumes of actual and simulated distracted skulls. Results: The developed digital distraction simulation was performed on the CT images of 10 patients. Plotting the relationship between the actual and simulated postdistraction volumes for the 10 patients yielded a slope of 1.0 and a correlation coefficient of 0.99. The average actual resultant volume change from distraction was 77.0 mL, compared to a simulated volume change of 76.9 mL. Conclusions: Digital simulation of cranial distraction was demonstrated through manipulation of the CT images and confirmed by comparing the actual to simulated volume change. This process may provide objective data in designing an individual distraction plan to optimize volume expansion and resultant cranial shape as well as patient education.