Keratin-based dressings for chronic wounds

What are keratin-based dressings?

Keratin is the protein that makes up skin scales. New technology is using keratin to cover and protect longstanding wounds or ulcers (especially chronic leg ulcers) to encourage healing.

Keratin dressings release keratin peptides into the wound. These activate keratinocytes (skin cells) in the wound bed, stimulating them to proliferate and leading to healing of the wound. Keratin dressings have been reported to reduce the total cost of care and improve quality of life.

Background information

Many wounds remain unhealed despite optimal standard care. For example, in the US, standard care of diabetic foot ulcers leads to healing of less than one-third of patients in 20 weeks. More than 25 per cent of venous leg ulcers remains unhealed, even after six months of therapy.

In chronic wounds, there is a failure of the normal healing processes, which include haemostasis (blood clotting), inflammation, the formation of granulation tissue and re-epithelisation of the skin surface.

Various attempts have been made to improve wound dressings, including the use of biological materials such as cells and growth factors.

The role of keratin in wound healing is under investigation. Traditionally, keratin has been viewed as purely a physical structure protecting the skin. However, we now know keratin proteins are also vitally important for normal wound healing.

Role of keratin in wound healing

Keratins (KRTs) are a family of epidermal proteins produced by cells called keratinocytes. They are present in skin, hair and nails. Keratin is an important component of skin barrier function.

Keratin gene expression demarcates three keratinocyte phenotypes:

• basal keratinocytes expressing KRT5 and KRT14 proteins
• differentiating keratinocytes expressing KRT1 and KRT10 proteins
• activated keratinocytes expressing KRT6, KRT16, and KRT17 proteins.

The activated or functional keratin has bioactive properties that enhance wound healing. Wound healing begins with the migration of keratinocytes at the edge of the wound towards the wound bed. This leads to the next stages of wound healing: proliferation and migration of fibroblasts, production of collagen and formation of granulation tissue.

Keratinocytes are not activated in non-healing chronic wounds.

Indications for use

Keratin dressings may be used to help heal a variety of wounds and ulcers. For example:

• Venous and arterial leg ulcers
• Diabetic foot ulcers
• Pressure ulcers (bedsores)
• Skin graft donor sites
• First and second-degree thermal burns
• Superficial injuries, cuts, abrasions and surgical wounds
• Epidermolysis bullosa.

What types of keratin dressings are available?

Keratin protein extracted from New Zealand sheep wool has been used to make wound dressings by Keraplast Technologies, LLC, San Antonio, Texas, USA (May 2013). Replicine™ Functional Keratin® advanced wound dressings are approved by the US FDA, European Union, Australian and New Zealand regulatory authorities.

Keratin dressings are available in different forms for different types of wound.

• Keratin-rich gel/ointment is suitable for dry wounds.
• Keratin matrix dressings are designed for wounds that produce a moderate amount of exudate; these dressings are absorbed into the wound as it heals.
• Multilayer dressings in which keratin in contact with the wound is backed by polyurethane foam are designed for highly exudating wounds.

How do we know that keratin dressings are effective?

No controlled clinical trials of keratin wound dressings have been reported to date. Available data are based on case series.

Clinical evaluations of keratin dressings for chronic wound care conducted at the Nurse Maude Wound Clinic, at Christchurch in New Zealand, have shown a reduction in wound size, confirmed by planimetry and wound photography, in a variety of problematic, non-healing chronic wounds.

• In 23 patients (mean age 74 yrs; mean wound duration 5.2 yrs) with chronic, long-term non-healing, non-infectious venous, arterial and diabetic wounds, three keratin dressings (gel, matrix and foam) were evaluated over a 3-month period.
• In this study, 91% of nurses and 86% of patients indicated a preference for the keratin dressings over their previous treatments.
• 71% of wounds categorized as non-healing by established independent criteria, (>6month duration, >5cm² size) achieved wound closure after the use of keratin dressings, confirmed by planimetry and wound photography, compared to a historical expectation of 13% for this wound type.
• In a separate case series of 4 patients with epidermolysis bullosa, regular use of keratin dressings for a period of 3-6 months resulted in a decrease in the rates of blister formation and improvements in wound healing rates.

How should keratin dressings be applied?

The following recommendations come from the manufacturer of keratin-based dressings.

• Sterility – the products are recommended for single-patient, single-use only and should not be used if the packaging is damaged.
• Infection control – if the wound is clinically infected, a dedicated antimicrobial dressing should be used to manage the infection before using keratin dressings.
• Preparation of the wound bed – the wound bed, should be cleaned, and all necrotic tissue removed and gently debrided.
• Dressing change – dressings should be changed sufficiently often to remove exudate from the wound and to replenish the supply of keratin.
• Dressings are designed to reabsorb and deliver keratin for a period of 4 to 7 days, depending on exudate levels and enzyme activity in the wound bed.

Do keratin dressings cause any harm?

To date, no adverse effects have been reported from keratin dressings. They are well tolerated by host tissues and do not provoke immune reactions.