Mayer Tenenhaus

A role for human skin–resident T cells in wound healing

Epidermal T cells have been shown to play unique roles in tissue homeostasis and repair in mice through local secretion of distinct growth factors in the skin. Human epidermis contains both αβ+ and γδ+ T cells whose functional capabilities are not understood. We demonstrate that human epidermal T cells are able to produce insulin-like growth factor 1 (IGF-1) upon activation and promote wound healing in a skin organ culture model. Moreover, an analysis of the functional capabilities of T cells isolated from acute versus chronic wounds revealed a striking difference. Both αβ+ and Vδ1+ T cells isolated from acute wounds actively produced IGF-1, demonstrating that they are activated during tissue damage to participate in wound repair. In contrast, IGF-1 production could not be detected in T cells isolated from chronic wounds. In fact, skin T cells isolated from chronic wounds were refractory to further stimulation, suggesting an unresponsive state. Collectively, these results define a novel role for human epidermis–resident T cells in wound healing and provide new insight into our understanding of chronic wound persistence.

Toward a common language: surgical wound bed preparation and debridement

Wound management encompasses a number of disciplines. As new concepts and innovative technologies develop within this exciting field, it is important to share them in spite of the divergence of clinical perspectives between the expert disciplines. One such divergence exists between surgeons and nonsurgical wound specialists. As a result, there is a need to develop a common language between these two groups. How can we develop a common language that unites surgical expertise within medical wound management? One route may be through the principles of wound bed preparation, which we believe have great potential for the communication of effective surgical techniques. Another is through sharing our concepts of surgical debridement as it is applied to different wounds by a variety of surgical disciplines. In this monograph, we try to bring these two themes together. We discuss how wound bed preparation has added to our understanding of the pathophysiology of the nonhealing wound and has provided us with some general clinical concepts. We discuss what role debridement, and then specifically surgical debridement, has to play within wound bed preparation, before analyzing the importance of surgical debridement in tissue preservation and the control of infection. We finally look at ongoing work that examines the cost of various surgical debridement techniques. We will also review a new hydrosurgery system (VERSAJET®, Smith and Nephew, Hull, UK), which we believe has an important role to play in the surgical preparation of the wound. We also expect that this paper will remind our medical colleagues about the critical role played by surgery in wound management.

Encircling the Tendon Repair Site with Collagen-GAG Reduces the Formation of Postoperative Tendon Adhesions in a Chicken Flexor Tendon Model

BACKGROUND Tendon healing is a complex and coordinated event involving the activation of extrinsic mechanisms as in classic reparative skin wound healing as well as intrinsic mechanisms characteristic of regenerative wound healing. Despite improvements in surgical and rehabilitative techniques, tendon adhesions remain the most frequent cause of disability following tendon surgery. In this animal model, we evaluated the use of a clinically available, biocompatible collagen- glycosaminoglycan (GAG) material as an adjunct to surgical tendon repair. METHODS Thirty-two white leghorn chickens underwent surgical tendon repair of their left second and fourth digits. Digits were randomized to study and control groups. In both groups, the long flexor tendon was divided and repaired using a modified Kesslers repair. In the study group, collagen-GAG membrane was wrapped around the repair site. Animals were immobilized with a plaster cast and sacrificed at 3 wk. Sixteen animals had their tendon repair sites histologically assessed and graded for healing and adhesion formation. Eight animals had their tendon repairs assessed for quantification of the work associated with flexion, employing a specifically designed biomechanical apparatus. Eight animals had their repair sites tested for bursting strength. RESULTS Control (untreated) tendons showed fibrous tissue surrounding the repair sites with approximately 50% of the circumference of the repair site adherent to surrounding tissue elements. The mean histologic grades for control and study group were 3.1+/-0.2 and 1.9+/-0.2, respectively. The difference between mean grades for control and study group samples was statistically significant (paired t-test: P<0.01). The work of flexion (WOF) for flexion cycles 1, 2, 3, and 4 for the control group was 0.58, 0.55, 0.46, and 0.44N/mm, respectively. The study (collagen-GAG wrapped) group had WOF values 0.16, 0.14, 0.10, 0.09N/mm, and the difference between the groups was statistically significant (paired t-test, P<0.01). The mean bursting strength of repaired tendons for control and study groups were 14.3+/-1.87N and 11.5+/-1.85N, respectively. There was no significant difference in bursting strength between the groups (paired t-test, P=0.71). CONCLUSIONS Collagen-GAG reduces formation of early postoperative tendon adhesions in this chicken flexor tendon repair model. Collagen-GAG wrapped tendons healed with minimal peritendinous adhesion formation and required less effort for flexion. The investing collagen-GAG membrane did not appear to interfere with either the quality or strength of healing.

Effects of E-selectin and P-selectin blockade on neutrophil sequestration in tissues and neutrophil oxidative burst in burned rats

OBJECTIVE Neutrophil deposition in tissues (leukosequestration) after shock may produce local tissue injury from proteases and high-energy oxygen species released from sequestered neutrophils. The initial step in the binding of neutrophils to capillary endothelium is the interaction of adhesion molecule (selectin) receptors between neutrophils and endothelial cells. We quantified leukosequestration in the tissues of burned rats using two methods of analysis: a) measurement of lung myeloperoxidase; and b) measurement of radiolabeled neutrophils and erythrocytes deposited in multiple tissues. We then determined the ability of a selectin receptor blocking agent to affect neutrophil deposition in tissues after burn injury. DESIGN Prospective, controlled, laboratory study. SETTING University research laboratory. SUBJECTS Male Wistar rats (200 to 300 g). INTERVENTIONS After tracheostomy and venous cannulation, rats received 17% total body surface area full-thickness contact burns and were resuscitated with saline (20 mL i.p.). Experimental animals received 2 mg/kg body weight i.v. administration of a P- and E-selectin blocking monoclonal antibody, CY-1747, immediately after burn. Lung tissue neutrophils were estimated by measuring myeloperoxidase in lung tissue. Neutrophil retention in lung, liver, spleen, gut, skin, muscle, kidney, and brain tissues was determined by removing (preburn) and differentially radiolabeling neutrophils (111In) and erythrocytes (51Cr), reinfusing cells 4.5 hrs after burn, and measuring tissue radioactivity 30 mins later. Edema was estimated by measuring extravasated 125 I-labeled albumin in the various tissues. Peripheral blood neutrophils were analyzed for intracellular hydrogen peroxide content, utilizing a fluorescent dye that reacts with hydrogen peroxide, coupled with analysis of cell fluorescence by flow cytometry. MEASUREMENTS AND MAIN RESULTS Myeloperoxidase concentration was increased in lungs 5 hrs after burn (p < .05), indicating neutrophil deposition. Radioisotope studies demonstrated significant (p < .05) leukosequestration into the lung, gut, kidney, skin, and brain tissues at 5 hrs after burn. Flow cytometry showed increased intracellular hydrogen peroxide content in peripheral blood neutrophils 5 hrs after burn. Tissue edema, manifested by radiolabeled albumin retention, was not seen in any tissues. Postburn neutrophil deposition in lungs and liver was blocked (p < .05) by administration of CY-1747 after burn, but maximal neutrophil hydrogen peroxide content was unaffected. CONCLUSION Burn injury in rats results in accumulation of neutrophils in multiple tissues. Neutrophil deposition in the lungs and liver is blocked by administration of the E/P-selectin blocking antibody, CY-1747. Since sequestration of metabolically active neutrophils may induce tissue injury, therapies that block postburn leukosequestration may improve clinical outcomes by limiting remote tissue injury.

Cutaneous microcirculatory assessment of the burn wound is associated with depth of injury and predicts healing time

RATIONALE Current trends for the treatment of deep partial thickness and full-thickness burns include early excision and skin grafting. In this study we retrospectively evaluated the ability of Laser Doppler Flowmetry (LDF), taken within 24h of the burn to predict: (1) burn wound depth and (2) wounds which would heal in less than 21 days. METHOD The Laser Doppler Flowmeter (O2C, LEA Medizintechnik, Germany) was employed to non-invasively measure the cutaneous microcirculation of 173 selected areas on 28 patients who suffered burns. RESULTS A distinct association between initial flow (<24h after burn injury) and the clinical assessment of depth of burn wounds was observed. Wounds demonstrating an initial blood flow of >100 AU were, in 93.1% of cases, correctly (positively) predicted for spontaneous healing within 21 days. A blood flow of <100 AU (negatively) predicted in 88.2%, those wounds which would not go on to heal within 21 days. Sequential measurement analysis (<24h, 3 days after injury and 6 days after injury) revealed no significant decrease in skin perfusion velocity or flow rate. CONCLUSION LDF can provide immediate results for early determination of burn wound depth and is useful in selecting patients for conservative treatment of their burn wounds.

Reduction of Diabetic Foot Ulcer Healing Times Through Use of Advanced Treatment Modalities

Diabetic wounds are a major health care problem associated with delayed healing and high amputation rates. This review systematically evaluated newer wound care therapies for the treatment of diabetic wounds. More recent means of approaching diabetic foot ulcers include various dressings, off-loading shoes, and bioengineered skin constructs and growth factors. Electrical stimulation, phototherapy, electromagnetic fields, and shockwave therapy have been further proposed as potential treatments. A brief overview of these treatments is presented using peer-reviewed evidenced-based literature. A review of the literature demonstrated that treatment of diabetic wounds has focused on either prevention of the wounds in the form of off-loading shoes or adequate protective dressings or on direct treatment of wounds with bioengineered skin constructs, growth factors, or medical devices that accelerate wound healing. The authors’ conclusion, following extensive literature review, is that although excellent national and international guidelines exist regarding suggested approaches to the treatment of the diabetic foot ulcer, there is no definitive or universal consensus on the choice of specific treatment modalities. The importance of optimizing comorbidities and the disease state, hemodynamics, local and peripheral skin and wound care, and metabolic challenges while reducing biological and bacterial burden and minimizing trauma remain the primary approach, followed by choice of the most appropriate treatment material or product.

Uncultured adipose-derived regenerative cells (ADRCs) seeded in collagen scaffold improves dermal regeneration, enhancing early vascularization and structural organization following thermal burns

OBJECTIVE Advances in tissue engineering have yielded a range of both natural and synthetic skin substitutes for burn wound healing application. Long-term viability of tissue-engineered skin substitutes requires the formation and maturation of neo-vessels to optimize survival and biointegration after implantation. A number of studies have demonstrated the capacity of Adipose Derived Regenerative Cells (ADRCs) to promote angiogenesis and modulate inflammation. On this basis, it was hypothesized that adding ADRCs to a collagen-based matrix (CBM) (i.e. Integra) would enhance formation and maturation of well-organized wound tissue in the setting of acute thermal burns. The purpose of this study was to evaluate whether seeding uncultured ADRCs onto CBM would improve matrix properties and enhance healing of the grafted wound. METHODS Full thickness thermal burns were created on the backs of 8 Gottingen mini-swine. Two days post-injury wounds underwent fascial excision and animals were randomized to receive either Integra seeded with either uncultured ADRCs or control vehicle. Wound healing assessment was performed by digital wound imaging, histopathological and immunohistochemical analyses. RESULTS In vitro analysis demonstrated that freshly isolated ADRCs adhered and propagated on the CBM. Histological scoring revealed accelerated maturation of wound bed tissue in wounds receiving ADRCs-loaded CBM compared to vehicle-loaded CBM. This was associated with a significant increase in depth of the wound bed tissue and collagen deposition (p<0.05). Blood vessel density in the wound bed was 50% to 69.6% greater in wounds receiving ADRCs-loaded CBM compared to vehicle-loaded CBM (p=0.05) at day 14 and 21. In addition, ADRCs delivered with CBM showed increased blood vessel lumen area and blood vessel maturation at day 21(p=0.05). Interestingly, vascularity and overall cellularity within the CBM were 50% and 45% greater in animals receiving ADRC loaded scaffolds compared to CBM alone (p<0.05). CONCLUSIONS These data demonstrate that seeding uncultured ADRCs onto CBM dermal substitute enhances wound angiogenesis, blood vessel maturation and matrix remodeling.

Stiff muscle fibers in calf muscles of patients with cerebral palsy lead to high passive muscle stiffness

Cerebral palsy (CP), caused by an injury to the developing brain, can lead to alterations in muscle function. Subsequently, increased muscle stiffness and decreased joint range of motion are often seen in patients with CP. We examined mechanical and biochemical properties of the gastrocnemius and soleus muscles, which are involved in equinus muscle contracture. Passive mechanical testing of single muscle fibers from gastrocnemius and soleus muscle of patients with CP undergoing surgery for equinus deformity showed a significant increase in fiber stiffness (p < 0.01). Bundles of fibers that included their surrounding connective tissues showed no stiffness difference (p = 0.28).). When in vivo sarcomere lengths were measured and fiber and bundle stiffness compared at these lengths, both fibers and bundles of patients with CP were predicted to be much stiffer in vivo compared to typically developing (TD) individuals. Interestingly, differences in fiber and bundle stiffness were not explained by typical biochemical measures such as titin molecular weight (a giant protein thought to impact fiber stiffness) or collagen content (a proxy for extracellular matrix amount). We suggest that the passive mechanical properties of fibers and bundles are thus poorly understood.

Using lower eyelid fascial slings for recalcitrant burn ectropion.

Burns of the lower eyelid represent a difficult management problem. Even with skin grafting, scarring and contraction can result in ectropion. This condition creates a marked aesthetic deformity, poses a risk of corneal exposure, and jeopardizes the patient’s vision. Historically, full-thickness skin grafts and tarsorrhaphies have been described to manage recurrent ectropion. The lower eyelid fascial sling (LEFS) uses a temporalis fascial strip to create a suspension sling for the lower eyelid. In a series of 7 patients, the LEFS procedure resolved the symptoms permanently in all patients. Because the LEFS procedure counteracts the natural scar contraction forces of lower eyelid burns, it can resolve recalcitrant ectropion successfully while preserving the function and aesthetics of the lower eyelid.

Cushing's syndrome after intralesional triamcinolone acetonide: a systematic review of the literature and multinational survey.

BACKGROUND Intralesional triamcinolone acetonide (TAC) is a well-established treatment for keloids and hypertrophic scars. The present text provides a systematic review of all previously reported cases of Cushings syndrome resulting from intralesional TAC in an effort to discover whether an association exists between dosage or frequency of injection and the subsequent development of Cushings syndrome. Data collected from a multinational survey of plastic surgeons is presented and discussed to understand current trends in the use of TAC. Recommendations for early recognition of Cushings syndrome, TAC dosages in children, and follow up guidelines are presented. METHODS A systematic review of the literature from 1950 to 2012 was performed to evaluate outcomes following intralesional TAC used for the treatment of scars. A confidential survey was sent to 4125 plastic surgeons, 102 responses from 9 countries were received. RESULTS A total of 18 cases of Cushings syndrome after intralesional TAC have been reported in the English world literature. Survey data reveals that at least 30% (25/84) of plastic surgeons exceed the recommended dosage of TAC and 47% (46/97) are not aware of Cushings syndrome as a possible complication of intralesional TAC. CONCLUSIONS Cushings syndrome resulting from intralesional TAC has been reported multiple times in the literature. Published literature suggests that TAC administered within the most recent recommendations does not appear to place adult patients at increased risk for developing Cushings syndrome. Children appear to be most at risk for developing Cushings syndrome and yet insufficient recommendations currently exist with regard to their safe dosage. Intralesional dosage should not exceed 30 mg per month in children while noting that at least one reported case of Cushings syndrome resulted from a smaller dose. Diligent follow up and patient education is advised for any patient treated with TAC so that complications can be recognized and addressed promptly.