Tissue Engineering and Wound Control
This essay is the fifth in the series Drexel students write about Drexel innovations
Tissue Engineering and Wound Control
by Jiaxu Zong and Hai Ngo
Tissue engineering is the application of cell biology, materials and engineering principles by the National Science Foundation in 1987 and formally established. It research and development of lesions for repair or improvement of human tissue or organ structure and function substitute the biological activity of science by the National Science Foundation in 1987 and formally established. My topic is built on tissue engineering and its application and development. Nowadays, Tissue engineering is widely used in biomedical engineering field that aims to make new biological material for replacing diseased or damaged tissues or organs. Tissue damage and defects will lead to dysfunction. The traditional repair method is autologous tissue grafting, although you can achieve a satisfactory effect, it at the expense of the cost of autologous approach to healthy tissue, and it will lead to many complications and additional injury; human organ failure, medication, temporary replacement therapy could save lives of patients, but it is limited sources of donor organs because of immune rejection requires long-term use of immunosuppressive agents, sometimes may brought the fatal complications. Since the 80's scientists put forward "tissue engineering" concept, it brought the dawn for many defects and the treatment of patients with organ failure.
The Need for Tissue Engineering Therapeutic applications include any disease in which tissue is lost or damaged. For instance, in type I diabetes the pancreatic islets of Langerhans are selectively attacked and destroyed by the body’s own immune system. Shapiro and co-workers have shown that islet transplantation can, over a short period of time, correct this disease and free its sufferers from reliance on insulin injections and regular glucose checks (Nicholas and Julia 87). Tissue engineering can be use for other autoimmune diseases also, such as rheumatoid arthritis, where the joints are the target of the immune attack.
In humans, skin represents approximately one-tenth of the body mass, and damage such as trauma, disease, burn or surgery to a part of this major organ has dramatic consequences (Anthony and Mark 413). For this point, people have found skin substitutes that is easy to handle and apply to the wound site; readily adherent; have appropriate physical and mechanical properties; be sterile, non-toxic, non-antigenic; and evoke minimal inflammatory reactivity. Besides that, they could reduce the host with minimal scarring and pain and facilitate angiogenesis, while still being economy. This way is feasible because they have the ability to release a multitude of growth factors, cytokines and bioactive peptide fragments in a temporally and spatially specific event-driven manner (Anthony and Mark 413). This kind of cytokines, enzymes and pharmacological agents should promote tissue repair and wounds.
There are varieties of materials to make artificial dermal and epidermal components. Examples of natural materials include polypeptides, hydroxyapatites, hyaluronan, glycosaminoglycans (GAGs), fibronectin, collagen, chitosan and alginates. Examples of synthetic materials include polyglycolide, polylactide and polylactide coglycolide, which are used for sutures and meshes; other examples include polytetrafluoroethylene and polyethylene terephthalate (Anthony and Mark 415).
Some people may confuse about regeneration and the normal outcome of tissue repair, namely fibrosis and scarring, let me explain the differences between them: Tissue repair is normally a rapid process that has been devised through evolution to allow animals to escape danger and rapidly recover tissue integrity using scarring to join the wound edges or to fill tissue voids (Anthony and Mark 420). Wound healing has often been described as a sequential mechanism and it is more specifically an event-driven process, whereby signals from one cell type set off cascades in other cell types, which propel the wound through the phases of healing (Anthony and Mark 420). In other aspects, it has the same effect. Scars are no more exists after almost every dermal injury. Regenerative medicine must to produce replacement skin which both aimed at the original structural and functional properties and incorporates into the host tissue without any scarring.
For many reasons, traditional wound healing and skin substitute have their advantages and disadvantages. Let us take a look of traditional ways of wound healing. As we know, in the past, people always use herbal plants to healing wounded skin, especially in China and India. It was called folk and traditional medicine. Ayurveda, found in India that using especially native plant sources as remedies. Actually, wound healing in western societies is different with Asian style. Wound research in Western societies using carefully understood principles of clinical science has focused on developing drugs, dressings or skin covers, or devices for treating patients with chronic wounds (Terence J. 22). There are many other traditional medicines in India, as well as local folk traditions used for healing wounds such as Hypericum hookerianum and Aloe.
All in all, we can see traditional medicine is affordable, but without the purification. Skin substitutes are made from abundant non-animal material and bioactive material promoting wound healing; Off-the-shelf.
The last thing I want to mention is Stem cells and their application to an engineered construction. Stem cells are defined by their ability to self-renew and to differentiate into multiple cell types, and are normally divided into somatic and embryonic stem (ES) cells (Nicholas and Julia 88). Stem cell of early human development is very important especially in children and adults. It can be found in post-stem cells as well. One of the most well-known stem cells is hematopoietic stem cells, for example, hematopoietic stem cells both exist in every child and adult’s bone marrow and circulating blood, but it is very small. In the course of our whole life, hematopoietic stem cells are constantly added to the human blood cells - red cells, white cells and platelet in the process plays a key role. So, we cannot survive without hematopoietic stem cells. Under certain conditions, it can be differentiated into various functions within the cell. According to stem cell developmental potential, it is divided into three categories: whole stem cells (totipotent stem cell, TSC), pluripotent stem cells (pluripotent stem cell) and single-stem cells (unipotent stem cell). Stem Cells (Stem Cell) are not fully differentiated and immature; it has regeneration of various tissues with organs and the potential function of the human body, the medical community known as the "million by cell." Biomedical engineers hope the use of human stem cells isolated and cultured in vitro breeding of the tissue or organ, and eventually through the tissue or organ transplantation to achieve the clinical disease. "In situ regeneration of skin stem cells to cultivate new skin technology" not only to achieve the use of stem cell replication skin organ but also make a copy of human skin organ in situ, so that in vitro cultivation of human tissue from stem cells into the organ transplant therapy, directly into the body of the original bit stem cell replication organs. With the rapid development of genetic engineering; embryo engineering; cell engineering and other biotechnology and according to a certain purpose, in vitro artificial isolated and cultured stem cells has become possible, using stem cells to build a variety of cells, tissues, organs as a source of organs for transplant, which will become the main direction of stem cell applications. Scientists generally believe that: stem cell research for clinical application will provide a broader outlook.
The ultimate goal of tissue engineering of the skin is to rapidly produce a construct that offers the complete regeneration of functional skin, including all the skin appendages (hair follicles, sweat glands and sensory organs) and layers (epidermis, dermis and fatty subcutus) with rapid take (vascularization) and the establishment of a functional vascular and nerve network and scar-free integration with the surrounding host tissue (Anthony and Mark 430). With this constructs, it allows the skin to accomplish many normal functions: mechanical and aesthetic functions; thermoregulation; pigmentory defence against UV irradiation and barrier formation. While it has many advantages, yet they are not easily to commercially scalable treatment regimes. Anyway, skin substitutes for wound healing are no longer a dream.
Anthony D, Metcalfe, and Mark W.J Ferguson. "Tissue engineering of replacement skin: the crossroads of biomaterials, wound healing, embryonic development, stem cells and regeneration." Journal of the Real Society Interface 4.14 (2007): 413-437. Web. 23 Feb 2011.
Terence J. Ryan. "Use of Herbal Medicines in Wound Healing: A Perspective Paper." International Journal of Lower Extremity Wounds. 2.1 (2003): 22-24 . Print.
Nicholas D. Evans, and Polak Julia M. The Potential of Stem Cells in Tissue Engineering. 2. Imperial College London, UK: Imperial College Press, 2007. 85-105. Print.