The application of skin substitute or dermal replacement method in treating burns has been started since the 1980s. Utilizing tissue engineering technology to create skin replacement tissue has succeeded in improving the wound healing quality in burn cases and provides a good alternative therapy besides existing conventional treatments.

The Skin Substitute in Burn Treatment



Burns Wound Treatment Problems

The principle of burn treatment adopted today is "early excision and skin grafting." Dead skin tissue is excised as soon as possible and cover the wound immediately with the autologous skin graft. The purpose of applying this principle is to reduce the systemic inflammation impact and the risk of infection caused by dead skin tissue. The application of this principle has been reported to reduce mortality and morbidity in burn patients.

Wound management problems are present in patients with extensive burns. The large wound area and the limited available donor area are the main problems in applying the principle of "early excision and skin grafting." Tissue engineering technology is the answer to solve these problems. The researchers try to produce skin substitutes or material that could be used to cover the wound area.

The ideal skin substitute materials that can provide structural support have the following characteristics:
  • Durable
  • Compositions that resembles normal tissue,
  • nonimmunogenic,
  • cheap,
  • can be used immediately and universally,
  • also has a high rate of therapeutic success.

Until now, researchers are still trying to create products that can meet all these criteria.


Skin Substitute as a Result of the Application of Tissue Engineering Technology

In 1975, researchers succeeded in breeding epidermal and dermal cells in vitro. In 1981, for the first time, skin substitutes were applied in treating burn cases. To date, the development and clinical use of various skin replacement products worldwide are not only for burns treatment but also in ulcers and other medical cases where there is a lack of skin tissue.

Based on its components, the skin substitute can be divided into:
a. Epidermal (cultured epidermal autograft or CEA): the main constituent material is keratinocytes and functions as the outer covering of the skin, like the epidermal layer.

b. Dermal: Generally, this type of skin substitute product is an extracellular scaffold matrix with ingredients derived from animals, humans, or synthetic materials. In some products, the matrix also contains cells. The functions of dermal skin substitute as structural support for autologous skin grafts or epidermal tissue replacement.

c. Combination (dermo-epidermal): This skin substitute type has dermis and epidermis components so that it is expected to be used as a definitive or permanent skin replacement such as skin graft. 


A 24-year-old male patient with a full-thickness chemical burn (sulfuric acid) to the left upper limb, involving creases.
A: Initial appearance, with an adhered and hard eschar;
B: formation of a uniform and non-hypertrophic granulation tissue. It was red and had no discharge following two escharotomies. It was covered temporarily with skin allografts;
C: placement of split-thickness skin grafts transversely soon after surgery
D: appearance at postoperative month 

 

The Skin Substitute Application in Extensive Burn Treatment

Cultured epidermal autograft (CEA) as a replacement for the epidermis has a poor graft (take) rate when applied directly in burn after excision of necrotic skin tissue. CEA requires a dermis tissue base with good vascularity. Therefore, skin substitutes for burn treatment are generally performed in stages and combined with skin originating from cadavers (allograft).

In the first stage, the patient underwent surgery for the excision of necrotic skin tissue. Available healthy skin donors are taken a little to undergo the breeding process. The remaining healthy skin area is used as a skin graft donor to seal the burn as optimal as possible. Areas that have not been covered by autologous skin grafts are covered with allografts or dermal skin substitutes. To get an adequate amount of CEA, it takes about 2-3 weeks to breed.

In the second stage, the epidermis of an allograft is removed, so that remains is the allograft dermis that has been appropriately vascularized and filled by migrating fibroblasts. The same process also occurs in the use of dermal skin substitute. Furthermore, the CEA produced, or the autologous skin graft can be used to cover the area. At this stage, the skin graft donor area used in the first surgery stage is generally covered with epithelium to be reused as a skin graft donor area. CEA can be applied in the form of sheets or cell suspension spray.

To simplify applying this skin substitute, researchers tried to create a combination of skin substitutes that already have epidermal and dermis components, so that wound closure can be done in 1 stage. This skin substitute contains autologous keratinocytes and extracellular matrixes with autologous fibroblasts. The disadvantage of the product currently available is longer breeding time, around 30 days. This is certainly a significant obstacle in patients with extensive burns that require rapid wound closure. 



Challenges in Applying The Skin Substitute.

Several challenges must be faced in applying the skin substitute in burn management. This technology has been around for almost 40 years. However, the high cost and unavailability of the cadaveric allograft are major obstacles. The skin substitute also has other disadvantages, more fragile, and susceptible to infection than natural skin graft tissue. Therefore, handling of skin substitutes must be done very carefully. 

The wound bed must be adequately prepared to prevent infections. This wound bed preparation must be performed with careful planning so that the wound is in a state of 'ready' when the tissue culture is complete. 

Another disadvantage of the available skin substitute product today is no completely healthy skin structure. Important histological structures that are not present in the skin substitute include sebaceous glands, sweat glands, melanin pigments, and hair follicles. 

One effort being developed at this time to overcome these deficiencies is to utilize stem cell technology. Most stem cell research in burn shows good wound healing results in animals and human subjects. The stem cell is expected to stimulate tissue regeneration so that these important structures can be formed again. Another method being studied is to induce stem cells to develop into these important structures. 



Summary

The Skin substitute is a tissue engineering technology that is very useful in treating burn cases, especially patients with extensive burns. Currently available are various skin substitute products used in burn cases such as epidermal, dermal, and combination skin substitutes.

The Skin substitute has several weaknesses, namely more fragile and susceptible to infection, and have no important skin structures such as sebaceous glands, sweat glands, melanin pigments, and hair follicles. Various studies are currently underway, some of which are in stem cells, aiming to overcome these weaknesses and improve future burn healing quality.



1. Singer AJ, Boyce ST. Burn wound healing and tissue engineering. J Burn Care Res. 2017;38(3):e605–13.
2. Biedermann T, Boettcher-Haberzeth S, Reichmann E. Tissue engineering of skin for wound coverage. Eur J Pediatr Surg. 2013;23(5):375–82.
3. Chua AWC, Khoo YC, Tan BK, Tan KC, Foo CL, Chong SJ. Skin tissue engineering advances in severe burns: review and therapeutic applications. Burn Trauma. 2016;4(1):1–14.
4. Zhang C, Chen Y, Fu X. Sweat gland regeneration after burn injury: Is stem cell therapy a new hope? Cytotherapy. 2015;17(5):526–35.
5. Ghieh F, Jurjus R, Ibrahim A, Geagea AG, Daouk H, El Baba B, et al. The Use of Stem Cells in Burn Wound Healing: A Review. Biomed Res Int. 2015;2015.


Source: 
1. https://www.alomedika.com  written by dr. Johannes AB, SpBP-RE (Cosmetic and plastic surgery)
2. Picture: http://burnssurgery.blogspot.com/2012/08/thermal-burns-hand-burns-bilateral-feet.html
3. Picture: https://parjournal.net/article/view/2841