The Rebirth of Regenerative Medicine in Wound Care

  WATCH: Author Janice M. Smiell, MD discusses her article

  Amniotic membrane has been utilized to treat chronic wounds for more than 100 years. Originally, the natural amniotic membrane — obtained from labor and delivery — was applied to various types of burns and wounds with a goal of protecting the wound from vapor and heat loss while providing pain relief. However, other characteristics of amniotic membrane that are even more helpful in supporting the healing process went unappreciated. Over the years, research has suggested that amnion could be more intimately involved in wound closure through a contribution of collagens and a basement membrane to which cells were attracted and upon which they could attach.¹ Furthermore, some patients experienced a reduction in inflammation and scarring. In fact, amniotic membrane has gained use in repair of nearly every organ system in addition to the skin — pulmonary, cardiac, genitourinary, gastrointestinal, neurological, and musculoskeletal. In a sense, this trend marked an early form of regenerative medicine. Over time, and with the concern of disease transmission by harvested human tissues, the main focus in wound care shifted to foams, alginates, and other advanced wound dressings, which represent the current standard of care for treating wounds.

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  In recent years, there has been a “rebirth” of interest in regenerative medicine in wound care driven by a tenacious pursuit to translate groundbreaking research into therapeutic products.² One aspect of this has been a renewed focus on the potential role of amniotic membrane in wound treatment. Some researchers now believe a decellularized amniotic membrane could represent the next stage of advanced wound care as part of the treatment of chronic nonhealing wounds that cannot be resolved using advanced dressings alone.³ In recent years, scientists have developed methods for cleaning, preparing, and preserving human amniotic membrane for surgical use, and creating sheets of amniotic membrane that can be cut to size and stored.

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ONLINE EXCLUSIVE: Podcast on Regenerative Medicine
Listen to an exclusive podcast with author Janice M. Smiell, MD, who discusses the future implications of wound care when it comes to the use of amniotic membrane. Click here to listen to the podcast.
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Better Understanding of Wounds

  It is no surprise that wounds and their needs in the healing process have not changed in the past 100 years, but our understanding of how to tend to them has. With improved methods to detect viral infections and knowledge of how to preserve human tissue without destroying its native architecture and key components, the use of donated human tissue has become accepted as providing much more benefit than risk to improve the health of those who need it. Decellularized and dehydrated human amniotic membrane (DDHAM) allografts have already been created. A decellularized amniotic membrane is derived from the placenta of a normal, full-term pregnancy. Each donor must be carefully screened with comprehensive medical and social histories and viral testing prior to procuring, processing, and testing the donated tissue that would usually be discarded in accordance with standards established by the American Association of Blood or Tissue Banking and the US Food and Drug Administration — all to greatly minimize potential risks of disease transmission. Safety testing includes evaluations for cytotoxicity, hemolysis, irritation, endotoxins, and pyrogenicity. The product is terminally sterilized with electron-beam irradiation and tested post-sterilization to demonstrate the absence of bacterial and fungal pathogens. Bhatia et al⁴ conclude DDHAM is an extracellular matrix-like tissue that is devoid of cells. It likely mimics the scaffolding function of the extracellular matrix, allowing fibroblasts to bind and contribute to the wound healing process at the wound site. DDHAM contains key cell adhesion protein molecules, such as fibronectin. Bhatia et al additionally suggest that cells, including fibroblasts, recognize fibronectin in DDHAM via fibronectin-integrin interactions and are stimulated to secrete fibronectin and assemble an extracellular matrix. The bound fibroblasts are also stimulated to secrete a variety of growth factors and cytokines that invigorate wound healing.⁴

  Such a membrane is natural human tissue that contains several proteins: collagen, fibronectin, laminins, proteoglycans, and other proteins and nutrients that are essential to support wound healing. Additionally, no cells are contained in the finished product, minimizing the potential for an immune reaction that may cause irritation and inflammation that can hamper complete wound closure. The epithelial basement membrane and extracellular matrix of this allograft provide a natural scaffold for cell attachment and proliferation needed for tissue repair. With tissue that is human and without foreign components, less reaction may be followed by minimized inflammation and scarring.

  The natural function of the amniotic membrane brings protection and support to the wound to which it is applied, specifically by reducing inflammation, supporting tissue growth, and providing a biological barrier to infection as well as minimizing pain upon application. These are the same benefits for which it was promoted in the early 1900s when used soon after it was obtained from a delivery room. It is designed to assist wound care clinicians (including surgeons, physiatrists, nurse practitioners, and podiatrists) in the treatment of a wide variety of wound types. With a pure amniotic membrane (no chorion layer) there is no need for specific orientation for placement. One decellularized amniotic membrane now on the market has a five-year shelf life and is available in sizes of 1 cm x 2 cm, 2 cm x 3 cm, 4 cm x 4 cm, and 6 cm x 6 cm.

  The decellularized amniotic membrane is intended for the management of non-infected partial- and full-thickness wounds, including chronic and acute wounds such as diabetic ulcers, pressure ulcers, venous ulcers, chronic vascular ulcers, tunnel/undermined wounds, surgical wounds (donor sites/graft, dehiscence), trauma wounds (abrasions, lacerations, second-degree burns, and skin tears), and draining wounds. Recently, the field of use for this product has been expanded to include podiatric and orthopedic applications including sports medicine-related conditions pertaining to use during the repair of tendon, nerve, and bone in the foot and ankle, and other surgical procedures in these specialty areas.

Benefits Related to Decellularized Membranes

  The clinical benefit of decellularized amniotic membranes in wound management has been supported by clinical studies. For example, Treadwell et al⁵ compared the treatment of second-degree burns using the membrane with a nanocrystalline silver dressing. Patients underwent burn debridement, photography, and measurement, and were randomized into one of two treatment groups. Burns treated with the membrane received one application of the product and weekly dressing changes with a nonadherent dressing. Burns treated with the nanocrystalline silver dressing had weekly application of the dressing. The time to healing and visual cosmetic appearance of the burn scar were reported. Treadwell et al⁵ reported that patients treated with the decellularized amniotic membrane healed by 1.3 weeks compared to 2.6 weeks for the silver dressing. Burn biopsy results showed faster restoration of normal skin architecture in the membrane-treated patients. The membrane-treated group healed with fewer complications and with better cosmetic results than patients treated with the silver-containing dressing. The pathological findings on burn wound biopsies in the patients showed a potential protective effect on the burned epithelium when used early in the treatment of injury. The study concluded the decellularized amniotic membrane can support a 140-fold increase in secretion from the tissues of IL-8, a chemokine that has been shown to enhance re-epithelialization of deep partial-thickness skin burns in the guinea pig model. Treadwell et al⁵ suggest this may explain the efficient healing of these injuries when treated with the membrane. Furthermore, they posit the fibronectin-containing matrix of the membrane may support the healing of the burn wound with less scar compared to the increased scar noted elsewhere in superficial donor-site wounds treated with silver dressings.

  Additional studies further illustrate the practical potential of amniotic membrane in the treatment of ischemic ulcer/surgical wounds, including a large registry study that included 230 patients.⁶ The wound types included both acute (traumatic and burns) and chronic (venous, diabetic foot, arterial, pressure, and collagen vascular disease ulcers). The presentation concluded that despite the challenges of uncontrolled factors that affect wound healing, this registry study demonstrated the safety and effectiveness of a decellularized, dehydrated human amniotic membrane allograft to support healing across a variety of wound types and patient conditions over the course of treatment in real world environments. Cases that were included in the registry follow examples of the benefits observed. One patient presented with gangrene of the great toe and experienced severe ischemia despite a recent successful bypass.⁷ The acute transmetatarsal amputation site of the toe resulted in a full-thickness wound with moderate exudate. This patient was treated with an amniotic membrane product over an area measuring 6.5 cm x 2.5 cm and 10 mm deep. Both the ulcer and the wound healed 15 weeks after two applications of the membrane.

Allograft Application

  Amniotic membrane has proven helpful in the treatment of venous leg ulcers.⁸ A 68-year-old female presented with peripheral vascular disease and a venous stasis ulcer on the left anterior shin. An amniotic membrane product was applied to an area measuring 3 cm x 5 cm and 1 mm deep. The ulcer healed approximately one week after a single application of the product.

  A decellularized amniotic membrane allograft is easy to apply and its translucency allows for wound bed visualization. It can be applied with either side facing the wound and can be anchored as needed and as determined by the clinician. Like all tissue allografts, a decellularized amniotic membrane should not be applied until excessive exudate or bleeding, acute swelling, and infection are controlled. The wound area should be prepared using standard methods to ensure it is free of debris and necrotic tissue. A commercially available version of the membrane can be trimmed to the desired shape and is available in a range of sizes to minimize waste. Upon application, the product conforms to the wound bed, creating the environment for cell migration into its native architecture. If a wound is larger than a single sheet, multiple sheets may be used to cover the open wound area. It is applied dry, providing the clinician with the option to either allow wound fluid absorption to hydrate it quickly or add sterile saline or other sterile isotonic solution, as needed, to hydrate. If there is a concern about wound fluid collection beneath the membrane, small slits may be made through the allograft (ie, “pie-crusting”) to facilitate drainage. After application, an appropriate nonadherent dressing should be used to stabilize its contact against the wound surface and to maintain a moist wound environment.

  This renewed focus on the role of human amniotic membrane is strong evidence that regenerative medicine is a key tool in wound care. When the wound bed is prepared and the allograft is used properly, amniotic membrane can assist in the healing process through a variety of pathways to promote regenerative healing while simultaneously reducing scar formation. Researchers have demonstrated dramatic wound closure rates for chronic wounds while recent studies of the mechanisms are offering a better understanding of the healing process. As a result, decellularized amniotic membranes — a key element of regenerative medicine’s “rebirth” — offer an interesting and effective new option for advanced wound care specialists and their patients.

Janice M. Smiell is chief medical officer at Alliqua BioMedical Inc., Langhorne, PA.

References

1. Koob TJ, Rennert R, Zabek N, et al. Biological properties of dehydrated human amnion/chorion composite graft: Implications for chronic wound healing. Int Wound J. 2013;10(5):493-500.

2. MacKay G. Regenerative medicine: Engineering its continued success. GEN. Dec. 27, 2012. Accessed online: www.genengnews.com/gen-articles/regenerative-medicine-engineering-its-continued-success/4653.

3. Koob TJ, Rennert R, Zabek N, et al. Op. cit.

4. Bhatia M, Pereira M, Rana H, et al. Mechanism of cell interaction and response on decellularized human amniotic membrane: Implications in wound healing. Wounds. 2007;19(8):207-217.

5. Treadwell T, Walker D, Nicholson B. The treatment of second-degree burns with dehydrated, decellularized amniotic membrane vs. a nanocrystalline silver dressing. Accessed online: https://equitiesiq.com/wp-content/uploads/2013/09/Biovance-Poster-SAWC-2014.pdf.

6. Smiell JM, Hahn HD, Gurney JP, Herb SE, Treadwell TA. Real world experience with a decellularized dehydrated human amniotic membrane (DDHAM) allograft. Poster presented at SAWC Fall 2014.

7. Alliqua BioMedical. Tissue reborn: Introducing BIOVANCE human amniotic membrane allograft. Accessed online: https: https://alliqua.com/wp-content/uploads/2014/05/Biovance-Visaid_Reader-Spreads.pdf.

8. Alliqua BioMedical. Tissue reborn: Introducing BIOVANCE human amniotic membrane allograft. Accessed online: https: https://alliqua.com/wp-content/uploads/2014/05/Biovance-Visaid_Reader-Spreads.pdf.