Abstract
There is a lack of quantitative and non-invasive clinical biomechanical assessment tools for diabetic foot ulcers. Our previous study reported that the indentation stiffness measured by an optical coherence tomography-based air-jet indentation system in a non-contact and non-invasive manner may reflect the tensile properties of diabetic wounds. As the tensile properties are known to be contributed by type I collagen, this study was aimed to establish the correlations between the indentation stiffness, and type I collagen abundance and organisation, in order to further justify and characterise the in vivo indentation stiffness measurement in diabetic wounds. In a male streptozotocin-induced diabetic rat model, indentation stiffness, and type I collagen abundance and organisation of excisional wounds were quantified and examined using the optical coherence tomography-based air-jet indentation system and picrosirius red polarised light microscopy, respectively, on post-wounding days 3, 5, 7, 10, 14, and 21. The results showed significant negative correlations between indentation stiffness at the wound centre, and the collagen abundance and organisation. The correlations between the indentation stiffness, as well as collagen abundance and organisation of diabetic wounds suggest that the optical coherence tomography-based air-jet indentation system can potentially be used to quantitatively and non-invasively monitor diabetic wound healing in clinical settings, clinical research or preclinical research.
Highlights
Diabetes mellitus is a metabolic disease characterised by hyperglycaemia
The load of indentation is mainly absorbed by the cutaneous proteoglycans in the extracellular matrix (Silver et al, 1992), which participate in regulating collagen deposition and maturation (Raghow, 1994; Reed and Iozzo, 2002) as well as in the whole wound healing process (Werner and Grose, 2003; Schultz and Wysocki, 2009)
Together with our earlier study that demonstrated the negative correlations between the tensile strength and indentation stiffness of a diabetic rat wound model (Choi et al, 2015), we hypothesised that the indentation stiffness is associated with the recovery of type I collagen histology during wound healing
Summary
Diabetes mellitus is a metabolic disease characterised by hyperglycaemia. Peripheral polyneuropathy, regional ischaemia in the limbs and foot ulceration are common diabetesrelated complications. Preclinical studies have consistently concluded that impaired wound healing in diabetic condition is characterised by decreased tensile strength, as well as reduced collagen abundance and organisation (Yue et al, 1987; Davidson et al, 1997; Schäffer et al, 1997; Reddy et al, 2001; Immonen et al, 2013; Minossi et al, 2014; Zhang et al, 2016) Both tensile testing and histological examination are not feasible in clinical settings because the excision of tissue samples from the subject is required. Together with our earlier study that demonstrated the negative correlations between the tensile strength and indentation stiffness of a diabetic rat wound model (Choi et al, 2015), we hypothesised that the indentation stiffness is associated with the recovery of type I collagen histology during wound healing
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