Treatment of deep second-degree burns on the abdomen, thighs, and genitalia: use of tilapia skin as a xenograft

Tilapia skin has a non-infectious microbiota and a morphological structure similar to human skin. Phase II clinical studies, not yet published, have shown promising results in their use for the treatment of burns. In the protocols of these studies, patients with lesions in areas of skin folds, such as genitals and inguinal regions, were excluded, as it was thought that the biomaterial would not adhere properly, resulting in a lower degree of healing. Case report of a female patient, 18 years old, without comorbidities, with deep second-degree burns in the abdomen, inguinal region, part of the genitalia and upper half of both thighs, involving 13.5% of the total body surface area. Tilapia skin was applied to the lesions leading to a complete re-epithelialization with 16 days of treatment. No side effects were observed. Tilapia skin, therefore, brings the promise of an innovative product, easy to apply, and highly available, which can become the first animal skin nationally studied and registered by the Agência Nacional de Vigilância Sanitária, for use in the treatment of burns. This case report contributes to reduce the limitations concerning the anatomical areas appropriate for the application of tilapia skin, since, even with the need for skin replacement, good results were obtained with application to the genitalia and inguinal region. ■ ABSTRACT

Treatment of deep second-degree burns on the abdomen, thighs, and genitalia: use of tilapia skin as a xenograft EDMAR  Tratamento de queimaduras de segundo grau profundo em abdômen, coxas e genitália: uso da pele de tilápia como um xenoenxerto Tilapia skin has a non-infectious microbiota and a morphological structure similar to human skin. Phase II clinical studies, not yet published, have shown promising results in their use for the treatment of burns. In the protocols of these studies, patients with lesions in areas of skin folds, such as genitals and inguinal regions, were excluded, as it was thought that the biomaterial would not adhere properly, resulting in a lower degree of healing. Case report of a female patient, 18 years old, without comorbidities, with deep second-degree burns in the abdomen, inguinal region, part of the genitalia and upper half of both thighs, involving 13.5% of the total body surface area. Tilapia skin was applied to the lesions leading to a complete re-epithelialization with 16 days of treatment. No side effects were observed. Tilapia skin, therefore, brings the promise of an innovative product, easy to apply, and highly available, which can become the first animal skin nationally studied and registered by the Agência Nacional de Vigilância Sanitária, for use in the treatment of burns. This case report contributes to reduce the limitations concerning the anatomical areas appropriate for the application of tilapia skin, since, even with the need for skin replacement, good results were obtained with application to the genitalia and inguinal region.

INTRODUCTION
Burns are responsible for 180,000 deaths annually, which are mainly concentrated in low and middle-income countries, a group in which Brazil is included. Besides, non-fatal burns result in prolonged hospitalization, disfigurement, and disability, with subsequent stigma and rejection¹.
Nile tilapia (Oreochromis niloticus) is the most cultivated fish in Brazil and the fourth most cultivated in the world². In addition to the full availability and constituting a product that used to be discarded, tilapia skin demonstrated, in previous studies, a noninfectious microbiota³, a morphological structure similar to human skin, even with higher amounts of collagen type1 4.5 , and excellent results when it was used as a xenograft to treat experimental burns in rats 6 .
Phase II clinical studies, not yet published, comparing tilapia skin with 1% silver sulfadiazine cream have shown promising results. In the protocols of these studies, patients with burns in areas such as the face, genitals, neck, armpits, antecubital fossa, and inguinal region were excluded. The presence of skin folds in these regions generated the hypothesis that the biomaterial would not adhere properly, resulting in a lower degree of healing.

■ RESUMO
Descritores: Queimaduras; Tilápia; Curativos biológicos; Materiais biocompatíveis; Ciclídeos. sodium chloride solution for 5 minutes, a process that is repeated three times in a row. The coverage of at least 1cm of healthy skin at the edges of the burned area and the overlapping of at least 1cm between the pieces of skin are necessary procedures to ensure that an eventual movement of patients in the first days of treatment does not lead to the exposure of any segment of the lesion.
The patient underwent balneotherapy under anesthesia and analgesia with 100mg of ketamine, 2mg of midazolam, and 2000mg of dipyrone. After removing any necrotic tissue and cleaning the lesion with drinking water and 2% chlorhexidine gluconate, the tilapia skin was applied. In total, 11 tilapia skins were used, sometimes cut to fit the contour of the burned area ( Figure 2). Finally, the region was firmly covered with gauze and bandage.
On the fourth day of treatment, the patient was submitted to a new anesthetic bath, in which the dressing was opened for the first time. It was observed good adhesion of the tilapia skin in part of the burned surface; however, in some regions, the skin did not adhere, having been removed together with the gauze or remaining in the burn bed, but with softened consistency and excess of underlying secretion (Figure 3). In these regions, the tilapia skin was removed (Figure 4), and, after cleaning, the biomaterial was replaced (Figure 5), covering tightly with gauze and bandage. The same sequence of procedures was performed on the seventh day of treatment, but with   better adherence to the tilapia skin and less presence of secretion ( Figure 6). On the 14th day of treatment, after opening the dressing, it was observed that several of the pieces of tilapia skin previously adhered, now had a dry, hardened    appearance and had started to come off. These pieces were removed by digitally separating the burn bed with the aid of petroleum jelly, exposing the underlying scarred skin (Figure 7). The rest of the tilapia skin was removed in the following 48 hours, and the patient was discharged, totaling 16 days of treatment.

DISCUSSION
In the search for new therapeutic alternatives for the treatment of burns, biocompatible or biological dressings have been highlighted. Since allografts are challenging to obtain and have low availability, xenografts can be a viable alternative due to their greater safety and reduced price 7 . Although frog skin has been used as a treatment for burns in Brazil 8 , it has never been registered by the Agência Nacional de Vigilância Sanitária (ANVISA) and is no longer in use. Therefore, the tilapia skin promises to be an innovative product, easy to apply, and highly available, which can become the first animal skin nationally studied and registered by ANVISA for use in the treatment of burns, in addition to be the first aquatic animal skin in the world used for this purpose.
With the use of standard treatments, it is expected about three weeks for complete healing of deep second degree burns 9 . Therefore, the 16-day period required for reepithelialization of this patient's burn and the absence of side effects suggested the effectiveness of tilapia skin as a flexible and adherent xenograft, with no antigenicity and toxicity, and the ability to conserve moisture and avoid the entry of microorganisms, characteristics of an ideal dressing for burns 10 . Besides, this case report contributes to reducing the limitations concerning the anatomical areas appropriate for the application of tilapia skin, since, even with the need for skin replacement, good results were obtained, including in the inguinal and genital regions. The decrease in the number of dressing changes is an essential factor in reducing pain in these patients, decreasing teamwork and hospital costs.