Can a Hypothermically Stored Amnion Graft Change DFU Outcomes in an Evolving Patient Demographic?

With the increasing prevalence of diabetes, it is crucial to develop new avenues to treat diabetic foot ulcers. These authors take a look at the research on a novel hypothermically stored amniotic membrane and its potential to close wounds faster.

The diabetes epidemic continues to grow in the United States. In 2018, a crude estimate of new cases of diabetes among adults 18 years old and older in the U.S. was 1.5 million—or 6.9 per 1,000 people.¹ This same survey estimated that 34.1 million—13.0% of all U.S. adults aged 18 years or older—had either diagnosed or undiagnosed diabetes in 2018.¹

This increasing pervasiveness of diabetes among Americans has had deleterious effects on the overall costs of healthcare, as well as on society and the economy. After adjusting for inflation, the medical costs of diabetes in the United States increased by 26% from $188 billion in 2012 to $237.3 billion in 2017, due to the increased prevalence of diabetes and the increased cost per person with diabetes.²

Historically, the prevalence of diabetes has correlated with advancing age. However, in 2015, adults ages 45–65 made up more than half of the reported new diabetes cases.¹ In 2017–2018, the estimated crude incidence rate of diagnosed diabetes among adults in the United States between the ages of 45–64 was 9.9 per 1,000 while the rate among those age 65 years or older was 8.8 per 1,000.¹

Correspondingly, as wound care practitioners we are seeing younger patients presenting with serious sequelae due to diabetes such as non-healing wounds, infections, and lower extremity amputations. The cost of treating a diabetic foot ulcer (DFU) is estimated to run $18,000 per case.³ The annual economic burden of chronic non-healing ulcers has been estimated to be $28.1 to $31.7 billion.4 When the cost of treating infections is included, the most expensive chronic wounds are surgical wounds ($11.7 to $13 billion) followed by diabetic foot ulcers ($6.2 to $6.9 billion).⁴

As the age of patients with new-onset diabetes decreases, the effects on the working-age population, and therefore on society and the economy, increases. In 2017, the estimated indirect cost of diabetes in the U.S. was $90 billion.² This number represents lowered work productivity and increased absenteeism among the employed, as well as reduced productivity for the unemployed and those who are unable to work due to disease-related disability.² This cost is rising as we continue to see more working-age patients seeking care for diabetes-related complications.

Despite advancements in medicine over the past two decades, DFUs continue to be a significant problem. Complications from DFUs are a leading cause of lower extremity amputations; it is estimated that 85% of all non-traumatic lower extremity amputations are a direct result of DFUs.⁵ It is well documented that amputations have a negative long-term effect on patient function, quality of life, and mortality.

Clearly, the impact of the diabetes epidemic is wide-reaching and compounding, particularly as the age of the affected population trends lower. Increasing the number of effective wound care therapies available to this patient population would decrease disease-related complications while increasing healing rates and the patients’ overall quality of life.

Advances in Amnion for the Treatment of DFUs

In recent years, cellular- and tissue-based products (CTPs) have emerged as one of the most promising groups of advanced wound care therapies for the management of DFUs. This category of advanced therapies supports cellular functions essential for wound healing. The ideal CTP is non-toxic, has no antigenicity, is immunologically compatible, and does not transmit disease. Broadly, CTPs can be categorized as autologous grafts, scaffold grafts, living cell grafts or amniotic tissue grafts—these last are derived from human placental tissue.

The use of placental tissue for wound healing began in the early 20th century when Dr. Davis at Johns Hopkins Hospital in Baltimore had success using amniotic membrane for skin grafting.⁶ Historically, this birth tissue that surrounds the fetus during gestation and acts as a protective barrier between baby and mother was harvested from women post-delivery. The intact and unprocessed amniotic membranes were then applied to a variety of wounds and burns. Presently, all commercially available amniotic tissue grafts are obtained from donated placental tissues of pre-screened, consented volunteers having C-section delivery of full-term live births and use one or more layers of processed amnion and/or chorion.⁷

Amniotic tissue has several advantageous properties for use in wound healing. One of the most advantageous is its lack of immunogenic markers. Amnion is considered “immunologically privileged” as it will not cause an immune response when applied to a host.⁸ The natural presence of anti-inflammatory cytokines and interleukins in amnion also makes it uniquely suited for use in wound healing. Chronic wounds such as DFUs do not progress in an orderly fashion through the complex healing cascade; they stall primarily in the inflammatory stage of wound healing. With such anti-inflammatory properties, the amniotic membrane can help “jump-start” the wound back into a healing progression. Structurally, amniotic tissue is composed of native collagen, laminin, and proteoglycans that lend structural support to the extracellular matrix.⁹ Mesenchymal stem cells, growth factors and cytokines are also abundant in amniotic tissue grafts.¹⁰ When applied to chronic stalled wounds, it is these regenerative molecules that are essential in activating cellular proliferation and migration to facilitate tissue growth and regeneration, which can eventually expedite wound healing.¹¹
New techniques in processing and storage of birth tissue have permitted the development of a fresh, hypothermically stored amniotic membrane (HSAM). One such HSAM is commercially available as Affinity™ (Organogenesis) (Figure 1). The Affinity allograft is derived from the amnion layer of human placental tissue. Affinity is minimally manipulated and, under the Food and Drug Administration’s (FDA) Good Tissue Practices and the American Association of Tissue Banks’ standards, undergoes aseptic cleansing through a proprietary process called Allofresh™.

Allofresh permits the membrane to retain a viable cell content, unlike most currently available amniotic membranes that lose their native viable cell populations during processing.⁷ In addition to being fresh, not cryopreserved or dehydrated, the Affinity membrane more closely resembles the structure and function of unprocessed placental tissue than other commercially available amniotic allografts. The Allofresh process permits Affinity to retain growth factors, anti-inflammatory cytokines, structural collagen and mesenchymal stem cells that other processing methods damage or decrease.

In 2017, McQuilling and colleagues used proteomic analysis to investigate the mechanism of action of the Affinity HSAM in wound healing.⁷ In their research they quantified 25 angiogenic, regenerative and anti-inflammatory growth factors and cytokines that are known to play an important role in wound healing. The results of microarray tests showed physiologically relevant levels of all of the essential growth factors and cytokines tested. Additionally, their work demonstrated that HSAM retains biologically active mesenchymal stem cells while also influencing increases in fibroblast and keratinocyte migration. This finding is of particular interest for the treatment of chronic wounds such as DFUs in which the normal activity of keratinocytes and fibroblasts have been found to be senescent and/or non-responsive. McQuilling’s benchtop research illustrates that the various pro-healing functions of HSAM make it a compelling treatment option.

The Results of a Recent Randomized Controlled Trial Using HSAM in DFUs

The authors recently participated in a first-of-its-kind clinical trial comparing outcomes between the use of HSAM (Affinity) and standard of care (SOC) to SOC alone in the treatment of DFUs.¹² This prospective, randomized, controlled study was conducted at 14 centers across the United States. SOC consisted of wound debridement per clinician discretion, use of appropriate inert wound care dressing to provide a moist wound environment, and offloading of plantar foot wounds via total contact cast. A two-week screening/run-in period of SOC alone was required for all participants.  

Inclusion criteria required patients to be age 18 or older, with at least one Wagner Grade 1 or 2 DFU, without signs of infection or osteomyelitis, that measured between 1–25 cm2, and had failed at least one wound care therapy. Patients also had to have an HbA1c <12%, an ABI between 0.7–1.3 mmHg and be able to tolerate offloading in a total contact cast or walking boot if they had a plantar surface wound. Patients with wounds that healed by greater than 20% during the screening period were excluded.

At the end of the screening period still eligible patients were randomized 1:1 into either HSAM + SOC arm or SOC alone arm. Wound evaluation and treatment visits occurred weekly for 12 treatments, or until wound healing was complete, whichever occurred first. The Aranz™ laser-assisted wound measurement device was used to obtain wound photographs and wound area measurements.

There were no significant differences in the baseline demographics of the 76 randomized subjects. The majority of patients were male (76%) and the median age was 59. At the first treatment visit, the mean ulcer areas were similar in both groups: 3.12 cm² in the HSAM group and 3.33 cm² in the SOC group. The rate of wound closure by 12 weeks in the HSAM group was significantly greater than that of the SOC group (55% vs. 29%). The median time to closure for the HSAM group was 11 weeks, while median time to wound closure for the SOC group could not be determined as 50% of those wounds had not healed by the end of the treatment period.  
This study was the first RCT to compare the efficacy of a fresh hypothermically stored amniotic membrane to a controlled SOC in the treatment of DFUs. Affinity-treated subjects showed a statistically significant, greater incidence of wound closure compared to SOC alone. The use of Affinity also improved median time to wound closure. These results support the use of HSAM plus SOC for the treatment of DFUs in a diverse patient population that has failed previous wound healing therapies.

Notably, the median age of patients in this trial was 59 years. This number falls below the average retirement age of 63 years—about 64 for men and 62 for women.¹³ With over half the new cases of diabetes occurring in patients 45–65, clinicians are seeing more working-age patients with diabetes related comorbidities and complications.¹

In Conclusion

HSAM has shown efficacy in improving median time to wound closure in a younger patient demographic. Healing wounds more quickly could reduce infection rates, hospitalizations, and amputations, thereby helping to minimize the impact of diabetes on overall healthcare costs and on society.   

Real-world studies comparing HSAM with other amniotic tissue membrane allografts for the treatment of DFUs may provide additional data to support these conclusions.

Windy Cole is an Adjunct Professor and the Director of Wound Care at Kent State University College of Podiatric Medicine in Independence, Ohio.

Stacey Coe is a Clinical Research Coordinator at Kent State University College of Podiatric Medicine.

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