Moist dressing coverage supports proliferation and migration of transplanted skin micrografts in full-thickness porcine wounds

Abstract

Transplantation of skin micrografts in a 1:100 ratio regenerate the epidermis of full-thickness wounds in pigs within 14 days in a wet environment. The aim of the current study was to combine micrografts and commercially available moist dressings. We hypothesized that micrografts regenerate the epidermis when covered with a moist dressing. 5 cm × 5 cm and 10 cm × 10 cm full-thickness wounds were created on the backs of pigs. Wounds were transplanted with 0.8 mm × 0.8 mm micrografts created from a split-thickness skin graft in a 1:100 ratio. 5 cm × 5 cm wounds were treated with wound chambers, moist dressings or dry gauze (non-transplanted control group). 10 cm × 10 cm wounds were compared to non-transplanted wounds, both covered with moist dressings. Reepithelialization was assessed in biopsies from day 10, 14 and 18 post-transplantation. 5 cm × 5 cm transplanted wounds covered with moist dressings showed 69.5 ± 20.6% reepithelialization by day 14 and 90.5 ± 10.4% by day 18, similar to wounds covered with a wound chamber (63.9 ± 16.7 and 86.2 ± 11.9%, respectively). 18 days post-transplantation, 10 cm × 10 cm transplanted wounds covered with moist dressings showed 66.1 ± 10.3% reepithelialization, whereas nontransplanted wounds covered with moist dressings were 40.6 ± 6.6% reepithelialized. We conclude that micrografts combined with clinically available moist dressings regenerate the epidermis of full-thickness wounds.

Introduction

Extensive burns and large wounds represent major treatment challenges. Split-thickness skin grafting is the standard of care in these difficult scenarios. However, in large burns, donor sites will have to be used multiple times and may increase the risk of wound infection and add to patient mortality [1], [2]. Current skin expansion ratios at a maximum of 1:6 are often times not sufficient [3], [4].

Cultured epithelial autografts provide an expansion ratio of up to 1000 times [5]. However, the cell culture process takes up to weeks, requires special laboratory facilities and puts the patient at additional risk [6], [7].

Early skin grafting techniques were developed by Reverdin [8], Thiersch [9], Pagett [10] and Brown [11]. In 1958, Meek [12] described a technique for expanding a small piece of skin with a microdermatome. Using this technique an expansion ratio of 1:10 could be achieved [12], [13]. However, the Meek technique required the skin pieces to be transplanted with the dermal side down to ensure dermis to dermis contact, and survival of the grafts. This made the technique extremely cumbersome [4].

Several attempts have been made to modify Meek's technique utilizing micrografts of different sizes [14], [15], [16], [17]. The modified postage stamp graft technique (also known as the Flypaper technique) has been widely used in burn patients, especially in Asia [18], [19], [20]. However, these methods all provide similar expansion ratios as compared to the original Meek technique and still remain labor-intensive and costly [4], [21], [22].

Previously we have described a simple technique to create skin micrografts from an autologous split-thickness skin graft (STSG) using a handheld mincing device. The micrografts were transplanted in a 1:100 ratio and were able to regenerate full-thickness porcine wounds in healthy as well as diabetic pigs [23]. The wounds were treated in a wet environment utilizing a polyurethane wound chamber that has been tested extensively in previous experiments [24], [25]. The wet environment enabled the skin micrografts to migrate and proliferate independent of orientation, which has been demonstrated in our previous work [23], [26].

In this study, in order to translate the micrografting technique into a clinically applicable setting we used a common moist dressing (hydrogel and foam) in place of the wound chamber. The hypothesis of this study was that micrografts will survive and regenerate the epidermis of full-thickness porcine wounds, independent of orientation, when covered with a clinically available moist dressing.