A Closer Look At The Efficacy Of Bioengineered Alternative Tissues For DFUs

Melissa Skratsky, DPM, and Stephanie Wu, DPM, MSc

   Winters and colleagues retrospectively evaluated the time to complete healing and the percent resolution of chronic full-thickness diabetic ulcerations that received Graftjacket.12 In 75 people (100 wounds) with comorbidities ranging from soft tissue and bone infection to cardiac disease, researchers found the mean time to heal to be 13.8 weeks and noted that 91 percent of patients went on to full epithelialization. The study authors concluded that this acellular dermal matrix is a viable treatment option for a wide array of diabetic wounds.

What The Literature Reveals About Apligraf

Apligraf (graftskin) differs from the two previously described tissue substitutes in that it contains viable allogeneic cells, thereby making it a “living tissue” bioengineered alternative tissue. This biologic consists of two layers that resemble epidermis and dermis. The keratinocytes and fibroblasts that are embedded within the bovine Type 1 collagen of this product originate from neonatal foreskin. By releasing various growth factors and proteins, these cells create a cocktail of cytokines and chemokines that replenishes the deficiencies of the wound and promotes healing.

   Initially approved in 1998 by the FDA for chronic venous leg ulcerations, Apligraf received another FDA approval two years later for neuropathic diabetic wounds of three weeks’ or greater duration. Although it has a maximum shelf life of only 10 days and is one of the more expensive bioengineered alternative tissues, Apligraf provides adherence that results in a good cosmetic appearance that is similar to autograft incorporation.18 Complete epithelialization of the ulcer may require multiple weekly applications. However, the overall cost when utilizing Apligraf in comparison to standard wound care practice is often much less due to the fact that the number of office visits and treatment duration is typically fewer.19

   A robust and comprehensive study performed by Veves and colleagues evaluated 208 patients with diabetic ulcerations.20 Researchers randomized the patients into either the control group (wet-to-dry dressing) or the graftskin group, and provided treatment for 12 weeks. A maximum of five weekly applications of graftskin was allowed and researchers assessed complete wound healing. The investigators found that 56 percent of graftskin patients and 38 percent of control group patients went on to closure. They determined that the odds ratio for complete healing was 2.14 in comparison to a number for the control group in favor of the bioengineered alternative tissue product. Additionally, the median time to epithelialization was 65 days for graftskin and 90 days for the control group, supporting the view that Apligraf results in a higher healing rate and may be an appropriate adjunctive treatment option for recalcitrant wounds.

Pertinent Insights On Dermagraft

Approved by the FDA in 2001 for full-thickness diabetic ulcers of greater than six weeks’ duration, Dermagraft also belongs in the “living tissue” category. This bioengineered alternative tissue has no epidermal component and is for use on superficial wounds as one cannot apply it over tendon, bone, muscle or capsule. It is composed of neonatal foreskin fibroblasts cultured on a bioabsorbable polyglactin mesh. These cells secrete matrix proteins and growth factors that ultimately create a three-dimensional scaffold, which stimulates ingrowth of fibrovascular tissue and epithelialization.

   Since Dermagraft is cryopreserved and stored at -75ºC, advantages of this tissue substitute include ease of handling, resistance to tearing and, in most instances, a lack of a foreign body immune response. Some disadvantages are the need for multiple applications, a higher price, the presence of bovine proteins in the medium and a storage solution that could result in hypersensitivity reactions.

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