Use of a Novel Human Keratin Matrix Improves Healing Rates in Diabetic Lower Extremity Wounds

Keratin has long been understood to play an important role in the structure and function of hair, skin, and nails, and it has recently been evaluated for its role in wound healing. In chronic wounds—those stuck in the inflammatory phase—keratinocyte activation is suppressed.¹ However, keratinocyte activation is related not only to inflammatory signaling, but to keratin as well.²

When keratinocytes are activated by keratin application, they support epithelialization of the wound bed via increased cellular migration and upregulation of basement membrane protein expression.^1,3 Furthermore, keratin has been shown to modulate inflammatory phenotypes in vitro, promoting progression past the stalled inflammatory phase of wound healing and towards closure.^3,4 Keratin biomaterials may also contribute to wound closure by supporting fibroblast viability and activation,⁵ and a recent publication showed the efficacy of a human keratin wound matrix product in the granulation and closure of chronic venous leg ulcers.⁶

The current case series evaluated the efficacy of a novel HKM (ProgenaMatrix; ProgenaCare Global, LLC) in the management of chronic lower extremity wounds in patients with diabetes that had not closed with previous treatment. 

Ten patients (6 males, 4 females; age range, 50–91 years) with lower extremity wounds were evaluated for healing rate with the use of HKM, compared as possible with previous treatment with SOC, including silver-containing (Acticoat; Smith+Nephew) and collagen-containing (Promogran Prisma; Solventum Medical) dressings. All patients had well-controlled type 2 diabetes (HbA1c <8%) and had risk factors for delayed healing, including neuropathy, infection (treated), or peripheral vascular disease (treated). Other systemic comorbidities present in these patients included end-stage renal disease requiring dialysis and/or heart disease. Patients were excluded if they presented with untreated infection or untreated ischemia. 

Patients were educated about potential risks (eg, patient discomfort due to product drying), benefits (eg, potential for improved healing rates), and complications (eg, periwound maceration in highly exudative wounds) of topical use of HKM. After informed consent was obtained, the wound was appropriately debrided to prepare the site for HKM application. Surgical debridement in the operating room was conducted initially to remove biofilm and visible nonviable tissue until a viable, granular wound bed was present.

The product (HKM) was fenestrated with a scalpel blade in a crosshatch pattern to allow for passage of wound drainage as needed, then fixed to the wound bed with gauze overlying. Offloading was also prescribed for patients with plantar foot wounds. Patients were followed up within 1 week of application. Mechanical debridement with a No. 15 scalpel blade to remove nonviable tissue, as well as reapplication of HKM, took place on a weekly basis until the wound was healed, unless otherwise noted. 

Wound area was calculated weekly by measuring the widest dimension (d1) and narrowest dimension (d2) of the wound with a ruler and assuming an ellipse with area (A):

A = πd₁d₂ / 4.

Healing rates were calculated as the change in wound area per week. 

If adverse events were observed, HKM was removed and patients received no advanced wound care products until their condition improved. The event was then evaluated for any relation to the applied HKM product. If the event was found not to be related to the HKM product, then HKM treatment was resumed until wound closure was achieved. 

Eight of the 10 patients originally were treated in a podiatry office with SOC, then switched to HKM. The wound healing rate prior to HKM treatment was obtained for comparison, and the percentage difference in healing rates with and without HKM was calculated. 

Statistical analysis was performed using Prism 9 (version 9.5.1; GraphPad Software). No power analysis was performed, and sample size for this small initial study comprised those with eligible wounds receiving care at the study site. The effect of HKM treatment on closure rate was evaluated using a Wilcoxon matched-pairs test with α set at .05 as the level of significance. Summary data are reported as the mean (SD) unless otherwise specified.

Within 8 weeks, all 8 patients with diabetes whose wounds were treated continuously with HKM exhibited complete closure of wounds ranging in initial size from 1.2 cm² to 40.0 cm² (Table 1), with a mean (SD) healing rate of 2.48 (1.95) cm² per week (Figure 1). The median number of HKM applications to wound closure was 6.5. Eight patients had been previously seen at the study location for standard wound care, and SOC healing rates were collected prior to HKM application. The wounds treated with keratin had significantly increased healing rates, with up to a 185% increase in healing rate with HKM compared with previous SOC with collagen (Figure 1, Table 1). 

In 2 cases, treatment with HKM was paused due to adverse events, as described previously. These events were determined not to be related to the keratin matrix, and treatment resumed after resolution of the condition. Patient 6 required a break in treatment for infection management due to noncompliance with outer dressing changes and resulting maceration (Table 2). Patient 10 was hospitalized for several weeks due to a cardiac event and received SOC wound treatment during that time (Table 3). During the times HKM was not applied, both of these patients experienced a decreased wound healing rate and an increase in wound size. The healing rate increased again when HKM treatment resumed. Patient 10 died of unrelated cardiac complications prior to confirmation of complete healing.

Three of the 10 cases are highlighted to demonstrate results of interest from HKM treatment.

Case 1
A 63-year-old female with type 1 diabetes and a history of neuropathy, peripheral vascular disease treated with angioplasty, kidney transplant, and previous midfoot-level amputation presented with a large (32 cm²) lateral ankle and lower leg abscess with lateral compartment necrosis (Figure 2A). The patient underwent irrigation and debridement with hypochlorous acid, silver and collagen dressings, and subsequent weekly HKM application (Figure 2B, C). Closure was confirmed at week 6 of treatment, after 5 applications of HKM (Figure 2D). 

Case 3
Case 3 was a 66-year-old female with type 2 diabetes with a history of critical limb ischemia with midfoot gangrene. The subsequent surgery on the affected foot created wounds requiring negative pressure wound therapy and skin grafting, which took over 5 months to heal, thereby putting the patient at high risk for nonhealing. The patient presented for the current study with neuropathy, peripheral artery disease, and acute thrombosis that was treated with arterial thrombectomy and subsequent extensive debridement, with fourth and fifth ray amputation (Figure 3A). The wound closed in 7 weeks with application of HKM (Figure 3B-D).

Case 10
A 59-year-old male with type 2 diabetes and neuropathy presented with a lower extremity wound and a history of peripheral vascular disease treated with percutaneous transluminal angioplasty (Figure 4A). This patient had the unusual circumstance of a 4-week interruption in keratin application in the middle of treatment while he was admitted to the hospital for heart failure, during which time he did not receive HKM treatments. This occurrence provided 2 separate treatment periods in the same patient (Figure 4B, C; Table 3). The wound showed a more noticeable reduction in size during the periods of HKM treatment (Figure 4D, green shaded areas) compared with treatment with other products. The wound closed after 9 nonconsecutive weeks of HKM treatment.

The current study has a small sample size and is an initial evaluation of a keratin-based product (HKM) for wounds in patients with diabetes, particularly wounds that had not responded to prior treatment. The initial results were promising, with wounds treated with keratin consistently exhibiting increased healing rates compared with treatment with other types of dressings commonly used, such as collagen. Notably, this was seen in a variety of wound types in these patients with diabetes, including nonhealing postoperative wounds. Diabetes is associated with delayed wound healing due to metabolic changes and impaired circulation, particularly in the lower extremities.⁷ By including a broader array of wounds beyond diabetic foot ulcers typically focused on in studies of advanced wound care products, the authors of the current study demonstrate that HKM treatment may be an effective way to address wound nonhealing in patients with diabetes in general. Although this difference was statistically significant, this small study is only an early indication of the potential efficacy of HKM in managing diabetic lower extremity wounds, and future study is needed.

In patients with diabetes, wound recurrence is a significant issue. Advanced wound care products do not address the underlying causes of these wounds and their chronicity, such as vascular damage and neuropathy, and newly healed tissue is often delicate and subject to recurrence. Six patients who receive regular podiatric care at the site of the current study were available for reevaluation of their healed wound upon their return 4 months after the conclusion of the study. No wound recurrence was observed in any of these patients. However, not all of these wounds resulted from the underlying diabetic condition (eg, surgical wounds), though this may have contributed to their chronicity. Nevertheless, this result suggests that HKM might support wound closure without recurrence. A larger study with extended follow-up of treated patients is needed to further study the effect of HKM on wound recurrence.

Interestingly, in the current study there were several cases in which it was not possible to use keratin continuously during the wound treatment period. A marked decrease in the healing rate was observed when HKM was paused; the healing rate increased again when treatment resumed. These results further support that the increased wound closure observed in the current study was related to HKM treatment.

Preparation of the wound bed is an important factor in the efficacy of advanced wound care products such as HKM. Not only has debridement been shown to be the most important factor in healing in lower extremity wounds in patients with diabetes,⁸ but a recent study also suggested that appropriate debridement is important in the efficacy of HKM in the management of other chronic wound types, such as venous leg ulcers.⁶ In the current study, appropriately debrided, viable, granular wound beds were an important consideration in the use of HKM. Moisture control also likely influences successful wound healing with this keratin matrix. Excessive moisture may lead to maceration and delayed healing,⁹ whereas too little moisture may dry the matrix and reduce wound bed contact. In the current study, the product was fenestrated to allow drainage of wound exudate through to an overlying secondary dressing to manage moisture.

Another clinical consideration for the use of HKM in the current study was weekly removal and reapplication of the matrix. However, given the enzyme-resistant nature of keratin,¹⁰ HKM may persist in the wound for an extended period and continue to support increased healing rates. Furthermore, keratin has been shown to attenuate the activity of enzymes such as matrix metalloproteinases.¹¹ In the persistent inflammatory environment of chronic wounds, excessive enzymatic activity contributes to wound nonhealing.¹² This is in contrast to collagen in the wound environment, which is highly susceptible to enzymatic degradation.¹³ Further investigation into the interaction of HKM with enzymes in the wound is needed to identify whether the product shares this enzyme-attenuating property of native keratin. 

The chronic inflammatory environment in nonhealing lower extremity wounds in patients with diabetes also contributes to nonhealing by preventing progression of the wound from the inflammatory phase to the proliferative and remodeling phases.¹⁴ Keratin has been reported to promote the transition of the macrophage immune response from the pro-inflammatory (M1) toward the pro-regenerative (M2).^3,4 While the current study did not directly investigate the composition of the immune response to the wound area, HKM treatment markedly improved the healing rate of wounds with seemingly stalled healing that did not close in 4 weeks or more. Future investigation, such as of biopsies or wound fluid samples, are needed to better understand the biological foundation of the results in the current study. 

Patients with diabetes often are at risk for nonhealing wounds due to systemic complications that disrupt the healing process. Overall, the results of the current study are promising first evidence of the efficacy of HKM in the management of lower extremity wounds in patients with diabetes. The weekly application of HKM consistently accelerated wound closure rates in chronic and difficult-to-heal wounds in these patients. This effect was dependent on continued contact of the product with a properly prepared wound bed. Wound closure rates decreased when HKM treatment was interrupted. Additional study is warranted of this promising treatment for wounds in patients with diabetes to further understand its clinical effect and its role in wound healing.  

Authors: Allison N. Ramey-Ward, PhD¹; and Ryan Chatelain, DPM²

Affiliations: ¹ProgenaCare Global, LLC, Marietta, GA; ²East Tennessee State University, Johnson City, TN

ORCID: Ramey-Ward, 0009-0007-9502-1531

Disclosure: Product used in this study was provided by ProgenaCare Global, LLC. Dr Ramey-Ward is an employee of ProgenaCare Global, LLC. No additional funding was obtained.

Correspondence: Ryan Chatelain, DPM; East Tennessee State University Quillen College of Medicine - Department of Surgery, PO Box 70575, Johnson City, TN 37614; ryan.chatelain@etsu.edu

Manuscript Accepted: April 25, 2024