Burns and Engineered Skin Grafts - Research Paper Example

? Burns and engineered skin grafts Your al affiliation Skin is the largest organ in the body and is multifunctional as it provides immune defense, acts as a barrier to external insults and regulates heat and moisture exchange in the body. It also has sensory functions. Therefore, when injured through burns, timely healing and repair is needed to ensure patients’ survival. Healing is a dynamic process and in sometimes there is delay of onset of the process (Peng Liu et al, 2008). Older methods of burn management includes the use of autografts, allografts and xenografts and they have many limitations such as variable acceptance rates of grafts, vulnerability of the patient to infections , high costs and delays in obtaining such grafts (Forouzandeh, Jalili, Hartwell, Allan, Boyce, Supp and Ghahary, 2010).For a very long time amniotic membrane, frog and cryopreserved human cadavers have been used in treatment of burns but for the past years, reconstruction of human skin using tissue engineered skin substitutes has provided us with a therapeutic alternative for clinical limitations offered by old methods (Bello, Falabella and Eaglstein, 2001).For many years ago, the possibility of culturing replacement tissues for use in repairing human skin was not possible and the only available options for skin repair were full thickness grafts, free tissue transfers and tissue flaps. This problem was solved with the invention of tissue engineered therapies which allows production of large quantities of human epidermis from a small initial skin biopsy (Black, Berthod, L'Heureux, Germain and Auger, 1998).This technique has been approved by US food and drug administration (FDA).Tissue engineered skin substitutes are advantageous as they enable tissue replacement without requiring a donor site, no scarring left, they have no toxic effects, no rejections detected as they mimic autografts by acting as a pharmacological agent and tissue replacement therapy. These skin substitutes also improve healing in acute wounds and burns .They also reduce pain which is associated with uptake of autografts. Tissue engineered grafts are thought to exert their effects on the burn through altering cytokine profiles within the wound (Harding, Morris and Patel, 2002) .The use of tissue engineered skin substitutes and cultured skin cells emerged in the 1980’s and today they have many applications in the treatment of chronic ulcers and chronic venous ulcers. (Woei ng, Dietmar, Jan-thorstern, Chin, Heng-phon Too, Thiam, Toan and Swee Hin Teoh, 2001).These grafts have been used to solve the prevalent problems of chronic wound and burns. These skin engineered grafts are produced from small skin biopsy which are cultured to generate large epidermal sheets and are used to treat extensive burns (Harding, Morris and Patel, 2002).Recent advances in tissue engineered skin grafts has been seen in the production of various living skin equivalents (LSE) that have limited immunogenicity and are available commercially (Harding, et al, 2002).These skin substitutes are microengineered, biocompartible, polymer matrix which may also contain cellular or extracellular substitutes such as collagen. Healing and growth protein factors which coordinate and regulate various interrelated processes during the wound healing process have recently been engineered through recombinant DNA technology (Enouch, Grey and Harding, 2006).These growth factors includes granulocyte colony stimulating factor which enhances katinocyte proliferation as well as inducing terminal differentiation and release of neutrophils from bone marrow. On the other hand ,transforming growth factor ? acts as a chemotactic substance by attracting macrophages to burn site, inhibiting metalloproteinase activity and inducing collagen and fibrogen production (Enouch et al, 2006). All these growth factors have recently been produced .Examples of tissue engineered skin substitutes includes: Cultured epidermal autografts (EpicelTM).It is a living autologous keratinocyte graft and is used for coverage of superficial and partial thickness burns (Enouch et al, 2006). IntergraTm is a skin engineered graft which consists of dermal fibroblasts and bovine collagen and is used to generate neodermis (Bello et al, 2001) since it has an artificial dermis and a disposable silicone sheet which serves as an artificial epidermis (Bello et al, 2001).It is used for immediate coverage of surgically exercised full thickness burns in reconstructive surgery (Enoch et al, 2006). OrcelTm is another tissue engineered skin graft and is a living cultured skin which consists of allogeneic fibroblasts and keratinocytes which are grown in vitro and seeded on the opposite sides of bovine collagen bilayered matrix. It is used as a partial replacement for allografts on digits (Bello et al, 2001). DermagraftsTm is a living allogeneic dermal which comprises of non-immunogenic neonatal fibroblasts which are cultured on a polyglactin mesh and is used to treat burns and also diabetic foot ulcers. It shows good resistance to tearing (Harding et al, 2002). AllodermTm is a non living allogeneic acellular dermal matrix with intact basement complex and is immunologically inert. It is processed from fresh cadavers skin (Enouch et al, 2006) and is used for preparation of wound’s bed before grafting. It has risks of infection transmission and split thickness skin graft is needed later (Bello et al, 2001). Cultured epidermal allografts-living allogeneic keratinocytes grafts are types of grafts which do not require biopsy and they are available immediately as they as can be cryopreserved. Recent studies have shown that if keratinocytes are suspended in a natural fibrin sealant matrix they have the potential to treat many skin defects including burns. The natural fibrin sealant promotes graft adhesion by acting as an ideal guiding structure for keratinocytes to reorganize themselves (Kopp, Marck, Alexander, Ulrich and Raymond, 2004). In cases of thickness burns, combination of this new tool with allogenic dermis has led to complex dermal epidermal reconstruction (Kopp et al, 2004).Another extracellular matrix which is processed from allogenic human fibroblasts is transcyte Tm and is available commercially as it can be cryopreserved (Enouch et al, 2006). Apligraft Tm contains both dermal and epidermal components and is used to treat venous leg ulcers, burns and foot ulcers. It is a living allogenic bilayered construct which is extracted from bovine tendons and then purified and cultured in allogenic human fibroblasts and cells which are isolated from neonatal skin of humans (Bello et al, 2001). Cultured epidermal allografts are also biologically engineered and are obtained from unrelated allogeneic donors. They can be grown and stocked for future use. However they have limitations such as they do not survive permanently on wound bed and can also transmit disease (Bello et al, 2001).Pig derived materials are also used for dressing of wounds and burns as they act as dermal matrices. OasisTm is an example of pig derived material which is derived from porcine small intestinal submucosa. The submucosa is important as it acts as a reservoir for cytokines and cell adhesion molecules which provide a scaffold for tissue growth. It is mainly used for management of partial thickness wounds/ burns (Bello et al, 2001). Studies have shown that skin engineered substitutes are important in the management of severe ocular chemical burns which in the recent years it has been challenging. These tissue engineered skin grafts have shown to reduce inflammation and promote ocular surface epithelial healing (Peng Liu et al, 2009). Though this technology is quite promising, good results have been obtained when there is optimal preparation of the recipient’s burn wound. Vacuum therapy has therefore been combined with this technology and is important as it ensures continuous elimination of serum, reduces bacterial counts and wound secretions at the same time creating a wound healing environment. It also ensures that the transplanted skin substitutes are kept in place (Koop et al, 2004). References Bello, Y.M., Falabella, A.F and Eaglstein, W.H (2001). Tissue Engineered skin: current status in wound Healing. American jounal of clinical dermatology , 2 (5), 305-313.Retrieved from http://www.transcyte.com Black, F.A., Berthod, F., L'Heureux, N., Germain, L and Auger, F.A (1998). In vitro reconstruction of human capillary- like network in a tissue engineered skin equivalent. FASEB J. , 12 (13), 1331-1340.Retrieved from http://www.fasebj.org Enouch, S., Grey, E.J and Harding, K.G (2006). ABC of wound healing .Recent advances and emerging treatments. BMJ , 332, 332-962. doi:10.11.3/bm.3327547.962 Forouzandeh, F., Jalili, R.B., Hartwell, R.V., Allan, S.E., Boyce, S., Supp, D and Ghahary, A J. (2010). Local expression of indoleamine 2,3-deoxygenase suppresses T-cell mediated rejection of an engineered bilayer skin substitute. Wound Rep Reg , 18, 614-623. doi:10.1111/j.1524-475X.2010.00635.x Harding, K.G., Morris, H.L and Patel, G.K (2002). Clinical review, Healing of chronic wounds. BMJ , 324, 160-163.doi:10.1136/bmj.324.7330.160 Kopp, J. G. (2004). Applied tissue engineering in the closure of severe burns and chronic wounds using cultured human autologous keratinocytes in a natural fibrin matrix. Cell and Tisses Banking , 5, 89-96. doi:10.1023/b:CATB.0000034082.29214.3d Peng Liu., Zhihong, D., Shufang, H., Tao, Liu., Ning Wen, Wei Lu, Xianthui Geng, Sha Huang and Yan Jin. (2009). Amniotic membrane extraction solution for ocular chemical burns. Clonical and Experimental Ophthalmology , 37, 855-863. doi:10.1111/j.1525-1594.2008.00654.x Peng Liu., Zhihong, D., Shufang, H., Tao, LiuL., Ning Wen, Wei Lu, Xianthui Geng, Sha Huang and Yan Jin. (2008). Tissue -Engineered skin mesencymal cells improves burn wounds. Artificial organs , 32 (12), 925-931. doi:10.1111/j.1442-9071.2009.02159.x Woei ng, K., Dietmar,W, H., Jan-thorstern, S., Chin, S., Heng-phon Too, Thiam, C., Toan,T and Swee Hin Teoh.. (2001). Evaluation of iltra Thin pol (e-Caprolactone) Films for Tissue Engineered skin. 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