A Closer Look At The Efficacy Of Bioengineered Alternative Tissues For DFUs
- Volume 25 - Issue 10 - October 2012
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The second characteristic that bioengineered alternative tissues must possess is the ability to remain immunologically inert but structurally intact until the proliferation and migration phases of wound healing are complete. If the product prematurely degrades, angiogenesis and synthesis of neodermal tissue will not occur. Eventual biodegradation of the dermal substitute is required but should take place at the appropriate time.
Enabling cell influx or providing a cell source within the product itself is the third quality. Fibroblast and endothelial cell migration onto the three-dimensional scaffold depend upon pore size and composition of the tissue product. While embedding fibroblasts into the matrix seems like an easy fix, one must take into account concerns about disease transmission and costs.
Lastly, the bioengineered alternative tissue must be resilient and resist shear forces. Ease of handling and application are key factors, especially when these chronic wound sites are located over a joint or on a weightbearing surface.
A Guide To The Categories Of BATs
According to Kim and colleagues, the vast number of bioengineered alternative tissues can be consolidated and understood more simply by dividing them into two broad categories: “living tissue” or “bioactive adjuncts.”12
Those that fall into the living tissue group derive from living cell cultures in which fibroblasts and keratinocytes are implanted into the construct. These products either stimulate the release of growth factors or deliver them directly to the wound when one applies these products. Wounds of a superficial nature tend to respond more favorably to “living tissue” bioengineered alternative tissues as they contain the ingredients needed to replace the currently absent dermis and epidermis.
Tissue substitutes that do not contain living cells are considered members of the bioactive adjunct group and function as a scaffold that supports cellular ingrowth. These products are generally reserved for deeper wounds in which the hypodermis and underlying tissue are compromised in addition to the superficial skin layers. Since the base of the ulceration needs to be built up, a supportive scaffold is in order and the bioactive bioengineered alternative tissue ultimately provides this.
Both categories of bioengineered alternative tissues serve a particular role in wound care management as the depth and the etiology of the ulceration should complement the product design and components. Keep in mind that improper selection and utilization of a bioengineered alternative tissue will result in a lesser degree of predicted success.
While a sizable number of biologics have been released with varied indications, let us take a closer look at the efficacy of the more commonly utilized bioengineered alternative tissues. These are Oasis (Healthpoint Biotherapeutics), Graftjacket (Wright Medical and KCI), Apligraf (Organogenesis) and Dermagraft (Advanced BioHealing). Apligraf and Dermagraft are approved by the Food and Drug Administration (FDA) for diabetic foot ulcers.
What You Should Know About Oasis
Oasis is a porcine xenograft derived from the small intestinal submucosa of swine. It falls under the bioengineered alternative tissue category of “bioactive adjuncts” because this product has components of the dermal extracellular matrix like collagen, elastin, proteoglycans, glycoproteins, glycosaminoglycans and growth factors although no living cells are present. Once harvested, Oasis soaks in antibiotics and bleach, and subsequently gets irradiated to ensure sterility while maintaining the structure of the extracellular molecules. The matrix architecture serves as a scaffold for cell proliferation and adherence. It also helps to alleviate pain, protects vital structures and allows for partial closure and granulation.