Human Keratin Hydrogel Matrices Accelerate Wound Healing via Keratinocyte Activation

Introduction: Chronic wounds such as diabetic foot ulcers are prone to severe complications including infection and amputation, and efficient treatments are critical to prevent these costly outcomes. Biomimetic approaches have gained clinical popularity, using wound dressing materials derived from tissue extracellular matrix (ECM) to promote healing and improve patient outcomes. In this work, we investigate the efficacy of a novel human keratin-based hydrogel matrix (HKHM) compared to other biopolymer ECM materials in a mouse chronic wound model and probe its mechanism of action in wound healing.

Methods: To investigate HKHM efficacy in vivo, four full thickness skin wounds were created on the backs of at least 13 db/db mice. Treatment of the four wounds was randomized between untreated control, HKHM, and two of four other biopolymer ECM products: a bovine collagen matrix, two amniotic membrane products, or a porcine small intestinal submucosa derived dressing. Wound area was measured weekly, and average wound size and time to closure was calculated for each treatment. The mechanism of action of keratin-based wound dressings was investigated in vitro. Expression of growth factors and cytokines important for cellular activation, proliferation, and maturation in skin healing were measured through qPCR and Western blotting on primary human keratinocytes and fibroblasts grown on HKHM.

Results: Chronic wounds treated with HKHM were on average 6.8 ± 3.3 cm^2 smaller compared to those treated with other biopolymer ECM products, and achieved full closure 11 ± 4 days sooner. We further found evidence in vitro of differential expression of cytokines, growth factors and mitogenic factors responsible for keratinocyte activation in human keratinocytes and fibroblasts grown on HKHM compared to those grown on tissue culture plastic.

Discussion: HKHM shows a more rapid rate of closure than other biopolymer ECM wound dressings, and in vitro results suggest that this is due to keratinocyte and fibroblast activation upon contact with the material. Accelerated healing of chronic wounds is critical to improved patient outcomes, and as such, treatment with HKHM may lead to improved patient outcomes by increasing the biochemical factors necessary to promote healing phenotypes.