Novel therapeutic targets for diabetes-related wounds or ulcers: an update on preclinical and clinical research

INTRODUCTION

Diabetes-related wounds, particularly diabetes-related foot ulcers, are mainly caused by lack of foot sensation and high plantar tissue stress secondary to peripheral neuropathy, ischemia secondary to peripheral artery disease, and dysfunctional wound healing. Current management of diabetes-related wounds involves the offloading of high foot pressures and the treatment of ischemia through revascularization. Despite these treatments, the global burden of diabetes-related wounds is growing, and thus, novel therapies are needed. The normal wound healing process is a coordinated remodeling process orchestrated by fibroblasts, endothelial cells, phagocytes, and platelets, controlled by an array of growth factors. In diabetes-related wounds, these coordinated processes are dysfunctional. The past animal model and human research suggest that prolonged wound inflammation, failure to adequately correct ischemia, and impaired wound maturation are key therapeutic targets to improve diabetes-related wound healing.

AREAS COVERED

This review summarizes recent preclinical and clinical research on novel diabetes-related wound treatments. Animal models of diabetes-related wounds and recent studies testing novel therapeutic agents in these models are described. Findings from clinical trials are also discussed. Finally, challenges to identifying and implementing novel therapies are described.

EXPERT OPINION

Given the growing volume of promising drug therapies currently under investigation, it is expected within the next decade, that diabetes-related wound treatment will be transformed.

Australian guideline on wound classification of diabetes-related foot ulcers: part of the 2021 Australian evidence-based guidelines for diabetes-related foot disease

BACKGROUND

Wound classification systems are useful tools to characterise diabetes-related foot ulcers (DFU) and are utilised for the purpose of clinical assessment, to promote effective communication between health professionals, and to support clinical audit and benchmarking. Australian guidelines regarding wound classification in patients with DFU are outdated. We aimed to adapt existing international guidelines for wound classification to develop new evidence-based Australian guidelines for wound classification in people with diabetes and DFU.

METHODS

Recommended NHRMC procedures were followed to adapt suitable International Working Group on the Diabetic Foot (IWGDF) guidelines on wound classification to the Australian health context. Five IWGDF wound classification recommendations were evaluated and assessed according to the ADAPTE and GRADE systems. We compared our judgements with IWGDF judgements to decide if recommendations should be adopted, adapted or excluded in an Australian context. We re-evaluated the quality of evidence and strength of recommendation ratings, provided justifications for the recommendation and outlined any special considerations for implementation, subgroups, monitoring and future research in an Australian setting.

RESULTS

After the five recommendations from the IWGDF 2019 guidelines on the classification of DFUs were evaluated by the panel, two were adopted and three were adapted to be more suitable for Australia. The main reasons for adapting, were to align the recommendations to existing Australian standards of care, especially in specialist settings, to maintain consistency with existing recommendations for documentation, audit and benchmarking and to be more appropriate, acceptable and applicable to an Australian context. In Australia, we recommend the use of the SINBAD system as a minimum standard to document the characteristics of a DFU for the purposes of communication among health professionals and for regional/national/international audit. In contrast to the IWGDF who recommend against usage, in Australia we recommend caution in the use of existing wound classification systems to provide an individual prognosis for a person with diabetes and a foot ulcer.

CONCLUSIONS

We have developed new guidelines for wound classification for people with diabetes and a foot ulcer that are appropriate and applicable for use across diverse care settings and geographical locations in Australia.

Monocyte phenotype as a predictive marker for wound healing in diabetes-related foot ulcers

AIMS

Delayed healing of diabetes-related foot ulcers (DRFUs) is associated with increased macrophage and matrix metalloproteinases (MMPs) at the wound site. Whether circulating monocyte phenotype and/or MMPs are altered in association with wound healing outcome is unknown, and was investigated in this study.

METHODS

Blood was obtained from 21 participants with DRFU, at initial visit (V1), week-4 (V2), and week-8 (V3) for measurement of monocyte number (CD14⁺), phenotype (CD16, CD163) and chemokine receptors (CCRs) by flow cytometry, and circulating MMPs and TIMP-1 by ELISA.

RESULTS

Six wounds healed during the study. At V1, non-classical CD16⁺⁺ monocytes and MMP-3 were higher in healed vs unhealed (both p < 0.05). At V3, the increased %CD16⁺⁺ persisted and %CCR2⁺ was decreased in healed, but no other monocyte markers nor MMP/TIMP differed between groups. Increased wound closure rate (WCR) at V3 correlated with increased %CD16⁺⁺ monocytes and decreased MMP-2 at V1 or V1 + V2. Receiver operating characteristic (ROC) curves yielded an area-under-the-curve of %CD16⁺⁺ at V1 of 0.78 to predict ulcer healing at V3.

CONCLUSIONS

These results indicate that circulating monocyte phenotype and MMPs alter as DRFUs heal. The relationship of %CD16⁺⁺ monocytes with WCR and ROC curve suggest a predictive role of %CD16⁺⁺ monocytes for ulcer healing.

Podiatrists' views of assessment and management of pain in diabetes-related foot ulcers: a focus group study

Background

Contrary to the belief that patients with diabetes-related foot ulcers (DRFU) do not experience wound related pain due to the presence of peripheral neuropathy there is increasing evidence that pain can be present. Subsequently, wound-related pain is often underestimated and undertreated. The aim of this study is to describe what influences pain assessment of DRFU.

Methods

A qualitative exploratory study was conducted with podiatrists who managed DRFU. Eight podiatrists were recruited through a professional organisation to participate in a focus group. A thematic analysis was conducted to identify themes that explored the barriers and enablers to pain assessment and management of DRFU.

Results

Three themes emerged. Observational and non-verbal cues were the preferred approaches used to assess wound pain. Assumptions and value judgments of the pain patients experienced and the relationships between podiatrists, patients and other health care practitioners were important influencers on the assessment and management of pain.

Conclusion

The perceived barriers to the assessment and management of wound related pain in DRFU were attitudes and beliefs about pain, lack of DRFU-specific validated assessment tools and lack of knowledge and skills to manage the pain.