Application of Electron Paramagnetic Resonance (EPR) Oximetry to Monitor Oxygen in Wounds in Diabetic Models

Abstract

A lack of oxygen is classically described as a major cause of impaired wound healing in diabetic patients. Even if the role of oxygen in the wound healing process is well recognized, measurement of oxygen levels in a wound remains challenging. The purpose of the present study was to assess the value of electron paramagnetic resonance (EPR) oximetry to monitor pO2 in wounds during the healing process in diabetic mouse models. Kinetics of wound closure were carried out in streptozotocin (STZ)-treated and db/db mice. The pO2 was followed repeatedly during the healing process by 1 GHz EPR spectroscopy with lithium phthalocyanine (LiPc) crystals used as oxygen sensor in two different wound models: a full-thickness excisional skin wound and a pedicled skin flap. Wound closure kinetics were dramatically slower in 12-week-old db/db compared to control (db/+) mice, whereas kinetics were not statistically different in STZ-treated compared to control mice. At the center of excisional wounds, measurements were highly influenced by atmospheric oxygen early in the healing process. In pedicled flaps, hypoxia was observed early after wounding. While reoxygenation occurred over time in db/+ mice, hypoxia was prolonged in the diabetic db/db model. This observation was consistent with impaired healing and microangiopathies observed using intravital microscopy. In conclusion, EPR oximetry using LiPc crystals as the oxygen sensor is an appropriate technique to follow wound oxygenation in acute and chronic wounds, in normal and diabetic animals. Nevertheless, the technique is limited for measurements in pedicled skin flaps and cannot be applied to excisional wounds in which diffusion of atmospheric oxygen significantly affects the measurements.

Impact of Hyperglycemia and Low Oxygen Tension on Adipose-Derived Stem Cells Compared with Dermal Fibroblasts and Keratinocytes: Importance for Wound Healing in Type 2 Diabetes

“…In contrast, alterations of ASC functions in diabetic rodent models were also described [6,16–18]. Because Desmet et al demonstrated prolongation of hypoxia in diabetic mice in vivo [19], we postulated that hyperglycemia coupled with hypoxia may influence the function of ASC. Veriter et al also demonstrated preliminary results concerning the capacity of VEGF released during hypoxia and normoxia conditions and its function in in vitro glucose concentrations.…”

Protection of glucotoxicity by a tripeptide derivative of α‐melanocyte‐stimulating hormone in human epidermal keratinocytes

“…Prolonged hypoxia, e.g. via microangiopathy, is considered to play a pathogenetic role in diabetic wounds . Moreover, HIF‐1 signalling was shown to be disrupted in diabetes .…”

Measuring Flap Oxygen Using Electron Paramagnetic Resonance Oximetry

“…Electron paramagnetic resonance oximetry (EPR oximetry) allows for direct, repeated, noninvasive measurements of oxygen through injection of a paramagnetic source into tissue . Although it has been used primarily to measure tumor oxygenation in response to radiation and chemotherapy, interest in utilizing it to measure tissue oxygen in wound healing and surgical flaps is growing . Using transcutaneous oximetry (TcO 2 ) as a control, we demonstrate the accuracy and ease with which EPR oximetry may be used to monitor flap oxygenation and viability.…”