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WOUND HEALING RESEARCH LABORATORY
Department of Dermatology and Cutaneous Surgery, University of Miami School of Medicine, USA
Anna Drosou MD

The Department of Dermatology and Cutaneous Surgery at University of Miami School of Medicine has a long history of dedication to wound healing science and clinical research. Our laboratory was founded in 1973 under the direction of Professor Patricia M. Mertz and with the strong support and personal involvement of William H. Eaglstein, M.D., Chairman of the Department of Dermatology and Cutaneous Surgery. During the past years, Stephen C. Davis, Assistant Professor, and Alex L. Cazzaniga, Research Associate, have also become an integral part of our laboratory. With our hard work and enthusiasm, our lab become one of the most recognized wound healing research laboratories in the US and has contributed greatly to the use of occlusive dressings and the understanding of 'moist' wound healing.

Professor Patricia Mertz with members of her team at
the Unversity of Miami, School of Medicine.

Our primary focus has been to evaluate the effects of various exogenous agents on the wound healing process and on wound infections, using well-controlled in vivo models. In addition, we have studied the various mechanisms involved in wound repair, to provide a better understanding of the pathophysiology of the wound healing process. Wound microbiology and bacterial biofilms are areas of great current interest for our research team. Recent cooperation with the molecular biology laboratory of Jie Li, M.D., Ph.D., who has joined our department and set up a basic research laboratory, has enabled us to conduct more diverse and complementary in vitro and preclinical in vivo and human studies. Her expertise has added a new dimension to our research capabilities with molecular tools to examine extracellular matrix, laminins, intergrin signaling and angiogenesis. Moreover, successful transfer of our results to the clinical setting is one of our top priorities.

For our in vivo studies, we have chosen porcine models, since porcine wound healing greatly resembles human wound healing and porcine skin has similar thickness and turnover time as human skin.¹ Over the past years we have developed and validated different wound models that closely imitate the clinical situations. By using the following models we determine the degree (and method) to which a topical medication, device, or dressing affects wound healing:

1. Partial thickness wound
2. Full thickness wound
3. Incisional wound
4. Second degree burn wound
5. Debrided second degree burn wound
6. Ischemic wound
7. Graft-take
8. Laser-induced wound

The procedures take place in fully equipped surgical rooms, and special attention is paid to reducing the stress of the animals during experiment. All protocols are approved by the University of Miami's Animal Use Com-mittee.
Wound healing is often determined by our epidermal migration assay.² Briefly, after separation of epidermis from dermis, epidermal defects are assessed and the time of complete reepithelialization is determined. In addition, histological examination, immunohistochemical, reverse transcription-polymerase chain reaction (RT-PCR) and other techniques are used to gather additional information on various mechanisms, inflammation processes, angiogenesis, collagen and connective tissue formation, and growth factor or cytokine profile. Small Angle Light Scattering (SALS), a laser device that determines the orientation of collagen fibers, enables us to objectively and precisely determine the effect of various exogenous therapies on collagen fiber alignment, an indication of scar formation.

Using our partial thickness wound infection model, we also establish the efficiency of different treatment modal-ities on preventing wound infection, decreasing the bacterial adherence or decreasing the bacterial proliferation of already colonized wounds. Different bacteria are used for this purpose; however, Staphylococcus aureus, MRSA and Pseudomonas aeruginosa are most frequently used, since they are the most common pathogens causing human wound infection. For bacterial quantitation, we have adop-ted technology used in the food industry. Serial dilutions of a wound sample are made and subsequently plated using the spiral plater system. The spiral plater system deposits a small amount (50ul) of suspension in a spiral pattern onto the surface of a rotating agar plate. Prior to initi-ating the in vivo evaluations, the effect of these wound treatment modalities may also be tested in in vitro studies.

In addition to developing the aforementioned wound models, our team has successfully used them to examine the influence of a large number of therapeutic modalities on the wound healing process. The effect of several antiseptics, antibiotics, dressings, as well as physical modalities such as electrical stimulation, ultrasound, ultraviolet irradiation, low energy photon therapy and others has been determined and their mechanism investigated. Our results have direct implication for the patient care setting. In some noteworthy past studies wet-to-dry dressings were found to injure wounds,³ an optimal period (therapeutic window) of application for occlusive dressings to promote and enhance the wound healing process was found, and early debridement of second degree burn wounds was shown to enhance the rate of reepithelialization.⁴

Briefly, some studies that were completed recently, or are currently being conducted in our laboratories, are:
(1) Determination of the efficacy of a 2-octyl cyanoacry-late formulation (Liquid Bandage, Johnson & Johnson), on promoting wound healing⁵ and its ability in preventing invasion of pathogens while controlling the proliferation of bacteria in colonized wounds.⁶ We found the Liquid Bandage to be very effective as a bacterial barrier and able to control the rate of bacterial proliferation of inoculated wounds more efficiently than the other treatment groups (standard and hydrocolloid bandages). Subsequently, Liquid Bandage was tested in a clinical trial on lacerations and was shown to promote wound healing more effectively than standard bandages.⁷ Liquid Bandage has been approved for over the counter use and has been launched this year.

(2) Pulsed electrical stimulation was found in our previous studies to accelerate epidermal wound healing in a porcine wound model⁸ and in human acute wounds in pilot studies. The optimal therapeutic regimen was also identified. Presently, we are investigating the effects of pulsed electrical stimulation on TGF-b1 and TGF-b2 secretion and activation and mast cell recruitment. Our hypothesis is that electrical stimulation can reduce fibrosis through the aforementioned mechanism.

(3) The effect of several over the counter (OTC) antimicrobial first aids on the proliferation of Staphylococcus aureus bacteria on colonized partial thickness wounds was evaluated. Surprisingly, the antibiotic bandages and ointments tested failed to have a significant impact on the bacterial proliferation, with the exception of the bandage and ointment containing neomycin, and

(4) An innovative therapeutic modality for wounds, low energy photon therapy, was recently studied in our facility. Our preliminary results showed it greatly accelerates wound healing in partial thickness porcine wounds and up regulates neutrophilic activity. We intend to continue our study in order to confirm and validate low energy photon therapy as an efficient alternative modality, mainly for the treatment of acute wounds and also chronic leg ulcers.

Interior of the laboratory of the Department of Dermatology and
Cutaneous Surgery at the University of Miami School of Medicine - one of
the leading wound healing research laboratories in the USA.

We also have great interest in studies of biofilms, which are aggregations of adherent bacteria living in a polysaccharide matrix. Biofilms were initially described in teeth plaque and on medical devices like catheters. Bacterial cells living in biofilms are particularly resistant to antimicrobials and can cause persistent infections. Recently, we demonstrated the formation of pseudomonal biofilms in inoculated acute partial thickness wounds⁹ and we reported data showing that bacterial biofilms also form in human chronic leg ulcers.¹⁰ These were the first reports implicating bacterial biofilms in wounds and resulted in an award at the 2001 Symposium of Advanced Wound Healing. The existence of biofilms in wounds can have direct clinical relevance and provides a possible explanation for the frequent failure of antibiotics used to treat infected chronic leg ulcers. Currently, we are focusing on discovering new methods to disrupt biofilms and on evaluating the effects of several antimicrobial agents commonly used on wounds on bacterial cells living in biofilms.¹¹
In addition to research, our laboratory members have been very active in various educational activities. P. M. Mertz and W. H. Eaglstein were instrumental in the University of Miami co-sponsoring the Symposium of Advanced Wound Care, an annual American meeting aiming on promoting wound care. Our faculty participates in and supports various national and international meetings and wound healing organizations. We have encouraged and guided medical students and dermatology residents research projects, which resulted in many publications.

The Wound Healing Research Laboratory of the University of Miami has had an active and successful course in diverse areas of wound healing. The successful application of our findings to clinical wound care is the most rewarding aspect of our research. We intend to continue with the same enthusiasm and commitment in the future. Collaboration with different academic departments with an interest in wound healing continues to be one of our goals. We would be glad to welcome you to our department and discuss in more detail our going research or future research projects.

References

1. Sullivan TP, Eaglstein WH, Davis SC, Mertz PM. The pig as a model for human wound healing. Wound Rep Reg, 2001; 9: 66-76.
2. Eaglstein WH, Mertz PM. New method for assessing epidermal wound healing: The effect of triamcinolone acetonide and polyethylene film occlusion. J Invest Dermatol. 1978; 71(6): 382-4.
3. Alvarez OM, Mertz PM, Eaglstein WH. The effect of occlusive dressings on collagen synthesis and reepithelialization in superficial wounds. J Surgical Research, 1983; 35: 142-8.
4. Davis SC, Bilevich ED, Cazzaniga AL, Mertz PM. Early debridement of second degree burn wounds enhances the rate of reepithelialization. An animal model to evaluate burn wound therapies. J Burn Care and Rehabilitation, 1996; 17: 558-61.
5. Davis SC, Eaglstein WH, Cazzaniga AL, Mertz PM. An Octyl-2-cyanoacrylate formulation speeds healing of partial thickness wounds. Dermatologic Surgery 2001; 27: 783-788.
6. Mertz PM, Davis SC, Cazzaniga AL, Drosou A, Eaglstein WH. Barrier and antibacterial Properties of 2-octyl cyanoacrylate derived wound treatment films. Journal of Cutaneous Medicine and Surgery (in press).
7. Eaglstein WH, Sullivan TP, Giordano PA, Miskin BM. A Liquid Adhesive Bandage for the treatment of minor cuts and abrasions. Dermatologic Surgery (in press).
8. Mertz PM, Davis SC, et al. Electrical stimulation: acceleration of soft tissue reapir by varying the polarity. Wounds, 1993; 5(3): 153-159.4
9. Seralta VW, Harrison-Balestra C, Cazzaniga AL, Davis SC, Mertz PM. Lifestyles of bacteria in wounds: Presence of biofilms? Wounds 2001: 13(1): 29-34.
10. Bello YM, Falabella AF, Cazzaniga AL, Harrison-Balestra C, Mertz PM. Are biofilms present in chronic wounds? Symposium in Advanced Wound Care, April-May 2001
11. Drosou A., Cazzaniga A.L., Davis S.C., Silver J.L., Mertz P.M. In-vitro evaluation of the bactericidal activity of three wound antiseptics against biofilms of common wound pathogens. Symposium of Advanced Wound Care, April 2002.